LIBRARY UNIVERSITY OF CALIFORNIA. Deceived M^^L- * , i8g Accession's No.& 1 / 1 . Class No. 3TS, AD' \TJLIC WORLD. 1EDALS JTIONS. KEITH'S PATENT BOILERS The " CHALLENGE/' The "VIADUCT," The " PYTHON," Ac., FOR HOT-WATER HEATING, Require no building work round them, are without rivals in efficiency and economy, and heat respectively from 50 feet up to 20,000 feet of 4-inch pipe, or its equivalent. KEITH'S PYTHON BOILER, as illustrated, and in its full size, has about 1000 square feet of effective heating surface, heats 20,000 feet of 4-inch pipe, and is the most powerful and complete sectional ' special ' hot-water boiler in the world. KEITH'S Boilers are in successful use by the thousands in all parts of the world, and they are almost exclusively used by Her Majesty's Government at the HOME OFFICK, for the heating work of the prisons throughout the United King- dom, in preference to all others. CS ENGRAVING "illustrates the most powerful form of Boiler that has yet been made for Hot-water Circulation." EXTRACT from 'Hooo' on Warming by Hot Water, New Editions, 1891-1893. PHENOMENAL REVOLUTION IN PUBLIC BATHS AND WASH-HOUSES. KEITH'S PATENTED SYSTEMS OF HEATING WATER, For Swirnmin 01 Ponds, Slipper and other Baths, Wash-tubs, Laundries. &c., by direct and indirect hot-water circulation on entirely new lines, have, within "the past year or two, and with the approval of Her Majesty's Local Government Board, been largely adopted by Municipal Corporations and Commissioners of Public Baths and Wash-houses, in preference to all other Systems. KEITH'S Systems have been adopted notably at the Putney, the Ilampstead, the Battersea, the East Dulwich, the Camberwell Green, the Caledonian Eoad, and the Hornsey Boad, Islington, Public Baths and Wash-houses, London; and at the Leicester Corporation Baths, being manufactured in America under JAMES KEITH'S AMERICAN " CHALLENGE " PATENTS, which United States' PATENTS have been purchased by and assigned to the makers of the said " Perfect" toiler. HARTLEY & SUGDEN, LTD., WROUGHT-IRON AND STEEL WELDED & RIVETED BOILERS, OF EVERY DESCRIPTION, FOR HOT-WATER HEATING APPARATUS. CORNISH "TRENTHAJVI" BOILER. ELEVATION. CROSS SECTION. J1EW INDEPENDENT " DUCHESS" BOILER. Registered No. 195501. New Illustrated Catalogue on application. PRACTICAL TREATISE UPON WARMING BUILDINGS BY HOT WATER Telegraphic Address "DONBOWES, LONDON." Telephone No. 3199. BROADWAY CHAMBERS, WESTMINSTER, LONDON. Sole Licensees & Manufacturers of Mr, Eogers Field's Patents ROGERS FIELD'S NEW 1889 PATENT" SELF-ACTING SIPHON, For building into Brick or Concrete Chambers, for Flushing Town Sewers, and SELF-ACTING GALVANIZED IRON FLUSHING CISTERN, Fitted with Rogers Field's New "1889 Patent" Annular Siphon for House Drains. PREVENTS DANGEROUS DEPOSITS IN DRAINS. PREVENTS THE LIABILITY TO THE EVIL EFFECTS OF SEWER GAS. AUTOMATIC FLUSHING CHAMBER FOR CLEANSING TOWN SEWERS. Bowes Scott & Western's Patent SELF-CLEANSING TROUGH CLOSETS And Kogers Field's PATENT FLUSHING OISTEENS for same. Suitable for Factories, Schools, Barracks, Workhouses, &c. &c. TROUGH URINALS on the same principle. REGISTERED IMPROVED FLUSHING GREASE TRAP, FOR USE IN CONJUNCTION WITH AN AUTOMATIC FLUSHING CISTERN. For further Particulars and Prices apply to BOWES SCOTT & WESTERN, BROADWAY CHAMBERS, WESTMINSTER, LONDON, S.W. A PRACTICAL TREATISE UPON WARMING BUILDINGS BY HOT WATER AND UPON HEAT AND HEATING APPLIANCES IN GENERAL WITH AN ENQUIRY RESPECTING VENTILATION, THE CAUSE AND ACTION OF DRAUGHTS IN CHIMNEYS OR FLUES, AND THE LAWS RELATING TO COMBUSTION BY CHAS. HOOD, F.R.S., F.R.A.S., &c. n RE-WRITTEN By FREDERICK DYE AUTHOR OF 'HOT WATER SUPPLY,' ETC. ETC. SECOND NEW EDITION HonUon: E. & F. N. SPON, 125 STRAND fltfo Sorfc: SPON & CHAMBERLAIN, 12 CORTLANDT STREET 1894 Engineering Library PREFACE. IN undertaking the recompilation of the late Mr. Hood's deservedly popular and valued book, it is with a feeling that the task might probably be an unsuccessful one, except for the fact that different methods and principles, due to the ever-varying requirements, are being continually brought to the front, and very many modifications in details and appliances have been introduced since the last edition of the book in question was published. Natural laws, of course, do not vary, and consequently many of the results obtained by Mr. Hood, evidently at great pains and research, will be repeated with but slight variation, a variation only brought about by the better and more precise appliances we now have at command ; but it is peculiar to note that, in studying the results brought about by any natural law, we have, to a very considerable extent, to consider many other branches of natural phenomena, and with a view to make everything as comprehensive and easily understood as possible, a brief notice upon heat, in its application to hot-water work, has been introduced, preceding the chief subject-matter under discussion. It is hardly reasonable to suppose that every one who takes up this book can be fully acquainted with all the properties of applied heat, yet it will be obvious that this knowledge, if only in a limited or elementary form, is practi- cally of necessity, if the perusal of this work is seriously undertaken. Successful hot-water engineering, whether for heating purposes or for domestic supply (now considered to be two distinct branches), is of all things perhaps the most dependent upon a very tolerable knowledge of nature's rules, a know* vi Preface. ledge, unfortunately, not possessed by the great majority of even our best class workmen, and on this account errors are of the most frequent occurrence, particularly when circum- stances make it necessary to carry out an undertaking some- what contrary to the customary method. Of course, pro- blems arise very commonly which need an advanced degree of skill to solve them, but this is the exception rather than the rule. If men who have intelligent ideas, and hope at some future time to control other workmen, were to devote a little time to reading up elementary works upon such sub- jects as natural philosophy (matter, motion, and heat), hydro- statics, &c., a pleasing study would be opened to them, and the knowledge would be of evinced value almost daily. In fact, any one interested or engaged in any profession or pursuit embracing any description of mechanics, would derive a most marked and obvious benefit by a knowledge of natural laws, without which knowledge very many undertakings must resolve themselves into mere guess work or crude inventions. If the whole credit of bringing the science of heating, particularly by hot water, to the forward state it now is in, is not due to Mr. Hood's labour and researches, there is no one who will begrudge him the greater share of it, for we have to remember that his first treatise was published in 1837, and although many of the rules laid down by him are now com- mon knowledge, the information he gave to the world at that early date was of an exceedingly advanced character, and much beyond what was commonly known at the time. In his death, the scientific, and also the social world, suffered a genuine loss. F. DYE. CONTENTS. CHAPTER I. HEAT. Material and kinetic theory Experiments and results Transmission of heat. CONDUCTION Conductive properties of materials Utility of poor conductors Diffusivity. RADIATION Radiating power of substances and surfaces Radiant heat and the atmosphere Action of radiant heat. CONVECTION Water and its composition and properties Action of convection Experimental results Convection of air and gases Advantages of hot water as a heating medium Page I CHAPTER II. CIRCULATION OF WATER, &c. UPON THE CIRCULATION OF WATER Theory and phenomena Tred- gold's explanation and Hood's criticism and theory Actual cause of circulation Variation in results- Motive power Table for deter- mining motive power. CONNECTING PIPES TO BOILERS Direction of pipes Multiple flow and return services Disadvantages of hori- zontal pipes Various simple forms of apparatus and their leading features demonstrated The most practical method . . . . 28 CHAPTER III. AIR IN PIPES SUPPLY OF WATER EXPANSION OF PIPES. AIR IN PIPES Accumulation and dislodgment Air pipes and cocks- Stoppage of air vents. WATER SUPPLY Provision to replenish loss by evaporation, also when water is drawn off Expansion of water by heat Capacity of supply cisterns Overflow Position of cistern Service pipe and connections Rain or hard water Sediment or lime deposit Useful appliance for small purposes Flushing and cleansing. EXPANSION OF PIPES Provision for expansion Measure of expan- sionPipe bearings . . . . . . . . . . . . . . 47 viii Contents. CHAPTER IV. IRREGULAR FORMS OF APPARATUS. Dipping pipes below doorways and other obstacles Its effect upon the motive power and general efficiency Velocity and its effect Practical T/. theoretical results Retrograde motion Calculations as to *' dip- ping " pipes Other phenomena Theory as to results obtained im- mediately the heat is first applied to the boiler . . . . Page 60 CHAPTER V. IRREGULAR FORMS OF APPARATUS continued. Other and more irregular forms of apparatus Methods of calculating the resistance experienced A phenomenon opposed to a theoretical basis Method of assisting the circulation in an irregular form of apparatus Hood's suggestion to this end and its advantages and disadvantages Another and practical method of effecting a good circulation below the boiler level The tank system Further informa- tion as to expelling air . . . . . . . . . . . . . . 74 CHAPTER VI. CAUSES AFFECTING CIRCULATION OF WATER IN APPARATUS. Friction Table of relative degrees of friction in different sized pipes Different purposes for different sized pipes Limit to circulation As to limiting the length of services Obstructions and faults Erratic results and their causes The effect of air in circulating pipes Reversed cir- culations As to whether the flow or the return services should contain the greatest amount of water . . . . . . 87 CHAPTER VII. EXAMPLES OF HOT-WATER APPARATUS. Describing some examples of the average apparatus A small apparatus for a lean-to greenhouse Description of boiler Arrangement of pipes Water supply, &c. Another apparatus suited for a small conserva- tory General description, position of boiler, &c., &c. Description of another conservatory apparatus A larger apparatus to heat two glass- houses Pipes in channels General description A large apparatus to heat a range of five glass-houses with melon pits Main pipes and their uses Carrying mains in trenches Branch services Pits with bottom heat Evaporating troughs Capacity of air for moisture Necessity of providing moisture Position of pipes as regards roots, shrubs, &c. . . . . . . . . . . . . . . . . 96 Contents. ix CHAPTER VIII. BOILERS. Heating surface, direct and indirect Horizontal and vertical Different resulting effects due to different conditions of the fuel Hood's standard of heating surface areas, and its application Boiler-makers' lists, and the deduction necessary to be made from them Flue surface and its value Action of flames and heated gases in flues Fletcher's heat collectors Suggested new standard value of different heating surfaces Small and large waterways Deposit, its effect and removal Cast and wrought boilers Area of furnace bars Hood's table, and necessary additions thereto Independent boilers and fixing Gas boilers Coke boilers, the " Star," " Coil," " Finsbury," " Horse-shoe," " Ivanhoe," " Dome-top," " Independent terminal end Saddle," " Challenge," and " Viaduct " Page 133 CHAPTER IX. BOILERS FOR BRICK SETTING. Saddle boiler and modes of setting it fully described Water bars and connecting Check ends and waterway fronts Cross tubes Flued saddle boiler The " Colonial " boiler The " Climax " boiler The " Imperial " boiler The " Delta " boiler The " Excelsior " boiler Wagstaff 's tubular boiler The " Champion " boiler Week's tubular boiler Water bars for coil and tubular boilers The " Python " boiler The Trentham Cornish boiler 182 CHAPTER X. APPLIANCES AND FITTINGS FOR HORTICULTURAL WORKS. Hot-water pipes and fittings Price list Jointing pipes The rust joint Red and white lead joint Rubber ring joint Improved expansion and other joints Stop valves and their uses The throttle valve The slide valve The medium screw valve The reliance valve Furnace fittings . . . . . . . . . . . . . . 217 CHAPTER XL QUANTITIES FOR HORTICULTURAL WORKS. Hood's rule and its application Hood's calculating table and notes thereon Rapid calculating table and notes thereon . . . . 238 x Contents. CHAPTER XII. FUEL, STOKING, AND ATTENTION TO HORTICULTURAL WORKS. Fuel Steam coal, coke, &c., and its use Sulphur Stoking and regula- tion of the fire Damping down Attention to air-vents Flue cleaning Frost, and precautions necessary Non-freezing solution Clean sur- faces to ensure full radiation of heat . . . . . . Page 247 CHAPTER XIII. UPON WARMING BUILDINGS (Low PRESSURE). Distinction between horticultural and building works Pressure and how exerted Calculations for pressure Shapes for boilers when pressure excessive Pressure does not aid circulation Comparison in size of pipes Air cocks and vents Expansion pipe Water supply . . 254 CHAPTER XIV. PIPES AND APPLIANCES FOR BUILDING WORKS. Pipes and fittings Qualities Price list Joints Gilled radiating pipe Coils and radiators, and their distinctive features Box coil Coil with expansive joint Coil cases and objections thereto Connections Cannon's radiator The " Universal " radiator Rosser and Russel's radiator Sanderson's radiator Heap's radiator Saturation of the air Ventilating radiators Stop valves . . . . . . . . 262 CHAPTER XV. QUANTITIES. Hood's rule and suggestions, and their application Calculations of cubical capacity Varied circumstances to be considered Table for rapid calculations . . . . . . . . . . . . . . 277 CHAPTER XVI. EXAMPLES OF LOW-PRESSURE APPARATUS FOR BUILDINGS .. 280 CHAPTER XVII. HIGH PRESSURE APPARATUS. Phenomena of Ebullition Heating of water in sealed vessels The high pressure system Size of pipe Boiler coil Motive power Expansion pipe and its use Filling Joints Stop-cocks Testing Advantages Contents. xi and precautions Frost Non-freezing fluid Uses of this system Proportions Temperature and pressure table Modification of H.P. apparatus Regulating valve The application of the Building Act Example apparatus . . . . . . . . . . . . Page 301 CHAPTER XVIII WARMING BUILDINGS BY HEATED AIR.. .. .. .. 313 CHAPTER XIX. HOT-WATER WORKS FOR BATHS, LAVATORIES, AND OTHER DOMESTIC AND GENERAL PURPOSES. Circulation Boilers and incrustation Pipes, taps, and other fittings and appliances Covering pipes and reservoirs for the conservation of heat Conversion of a tank apparatus to the cylinder system Twin boilers and services Improved and other systems ; peculiarities noticed from experiments, and their results in practice Coils and coil services Faults and sources of trouble Accidents and sources of danger Safety valves, &c. Low-pressure boilers, also fitting high-pressure boilers for temporary low-pressure work . . . . . . . . 329 CHAPTER XX. COMBUSTION ; ITS APPLICATION TO WARMING PURPOSES BY GRATES, &c. Stoves and grates Value of radiant heat Smoke Slow combustion, advantages and disadvantages Utility of the " Blower " to grates Dr. Arnott's principle, and its unique value Fire-brick and poor heat conducting materials Grate backs and other improvements Process of combustion Carbonic acid and oxide Bituminous fuels Products of perfect and imperfect combustion Carbon and hydro-carbon Soot . . . . . . . . . . . . . . . . . . 439 CHAPTER XXI. CHIMNEYS. Draught in chimneys, cause and effect Causes of sluggish draught Stoves v. grates Sizes and areas of chimneys Suggested sizes for horticultural works Residence chimneys A common but little known cause of trouble Pipe chimneys Descending chimneys "Pilot" stoves . . 4 . .... . . 452 xii Contents. CHAPTER XXII. VENTILATION. Ventilation by natural or mechanical means Quantity of air per person Table of quantities for various requirements Ventilation to living rooms Extract flues Table of velocities at different temperatures Air propulsion Relation of inlets to outlets Points of entrance for cold or heated air . . . . . . . . . . . . Page 465 CHAPTER XXIII. THE METROPOLITAN BUILDINGS ACT. ITS APPLICATION TO HOT- WATER, STEAM, AND HOT-AIR WORKS, AND TO CHIMNEYS AND SMOKE-FLUES .. .. .. .. .. .. .-477 APPENDIX .. .... 488 INDEX .. .. 503 PRACTICAL TREATISE UPON WARMING BUILDINGS BY HOT WATER. CHAPTER I. HEAT. Material and kinetic theory Experiments and results Transmission of heat. CONDUCTION Conductive properties of materials Utility of poor conductors Diffusivity. RADIATION" Radiating power of substances and surfaces Radiant heat and the atmosphere Action of radiant heat. CONVECTION Water and its composition and properties Action of convection Experimental results Convection of air and gases Advantages of hot water as a heating medium. THE sensation produced when we approach or touch anything of a high temperature was, until a comparatively short time ago, attributed to the presence of an infinitely subtile material, matter or fluid (whatever one likes to desig- nate it) that pervaded substances that had been acted upon in a manner to make them what we call " hot " ; this delicate fluid being imponderable and, in fact, impalpable to all our senses except that of feeling. When the material assumed a redness from heat, it was not supposed that the fluid itself was thus made visible, but that it was merely an altered appearance of the substance due to the presence and con- dition of the fluid. The name given this material was Caloric (calor^ heat) of the Material Theory. Side by side with this belief was another which for some B 2 Warming Buildings by Hot Water. time did not receive so much favour, by some inexplicable cause, but which now is considered to be, and is recognised by all without exception, as the true cause of the phenomena under discussion. By this latter theory we understand that heat is wholly and solely motion nothing more and nothing less a rapid movement of the small particles (molecules) of which all descriptions of matter are made up ; the rapidity at which the particles move being the index to the temperature, so to speak ; that is, the more rapid the movement the greater the heat felt, and vice versd. This has received the title of the Kinetic (motion) Theory. Great were the contests at the time that these two theories were approaching an equal footing, the followers of one having as many irrefutable arguments as the other ; but Count Rumford, Sir Humphry Davy, and more recently Professor Tyndall, are chiefly responsible for the victory of the kinetic principle. The first of these scientists received his chief impressions from noticing that in boring cannon the gun itself became heated, the shavings noticeably more so, and also the tool ; and this heat was evolved and felt for however long a period the boring was continued. Sir Humphry Davy's chief or best known experiment was to cause a blunt steel tool to revolve at a high speed against the bottom of a metal cylinder, this cylinder being surrounded by another and the space between rilled with water, and so long as the tool revolved the friction produced sensible heat, and the water attained a high temperature whether for an hour or days. It requires but little discernment now to see how opposed this is to the material theory, in which substances or bodies were supposed to have a capacity for so much hidden heat (that is, to hold or have room for a certain quantity of heat which did not manifest itself except under certain conditions), for these experiments showed that two very small pieces of metal, if kept in friction one against the other, were capable of giving out heat for an almost endless period, or until they were worn away. Then Conduction of Heat. 3 again, with our most precise and delicate appliances, it has been impossible to discover the slightest increase in heaviness in a body after it has been heated, yet the lightest gases and elements known to us have a very sensible weight. Heat transmits or manifests itself to our sense of feeling in three ways, viz. by 1. Conduction. 2. Radiation. 3. Convection. All these three methods intimately concern the art of heating by hot water, and a knowledge of them is accountable for the majority of the improved appliances introduced. i. CONDUCTION OF HEAT. This is the mode by which heat is transferred through or about a material or body ; but its effect is chiefly noticed with solids, some of which possess great powers of conductivity although fluids (both liquids and gases) possess this property in a limited form. In discussing hot-water work it is not with the conductive powers of fluids that we have to deal, for, as just mentioned, the property is manifested to such a trifling extent as to be useless for practical purposes, excepting when it is desired to prevent loss or transference of heat, as fluids come under the heading of poor conductors of heat, of which we shall show the utility presently. Water is a good absorber of heat, and as a generally applicable rule we may consider that anything that imbibes heat readily is just as willing to give it up again ; conse- quently, in water we have an exceedingly cheap and available material in the greatest abundance, admirably suited for the absorption and dispersion of heat needed in hot-water work. But these two qualities which it possesses are by no means all that is necessary for a successful apparatus ; for we cannot have the heat direct from the water itself, owing to the B 2 4 Warming Buildings by Hot Water. necessity of inclosing it in some form of vessel or container (piping) ; and if the material of this container is not a good conductor of heat, all the good qualities of the water and other parts of the apparatus are rendered nil. And further than this, the materials must not only possess successful conductive powers, but must also have another quality which will be found under the heading of Radiation. If we were to use papier-mache pipes (as are used largely in America for cold water) we should get the very worst results, the same with any other material (such as earthen- ware) having a low conductive power ; but were we to use pipes of silver (having the outer surface adapted for radiation) an improvement upon iron would be effected, as the table which follows will show : COMPARATIVE CONDUCTIVE POWERS OF SUBSTANCES. (Wiedemann and Franz.) Conductivity. Silver 100*0 Copper 73-6 Brass 23*6 Iron 11*9 Lead 8-5 German silver 6-0 (M. Despretz.) Silver 97'3O Copper 89-82 Brass 75*20 Cast iron.. 56*90 Wrought iron , 37'43 Lead 17*96 Marble 2*36 Firebrick 1*14 Water 0*90 An appreciable difference exists between these two tables, as will be seen at a glance, although the different substances follow in rotation alike in both cases ; but it is worth noting that Mr. H. G. Madan, in his excellent work upon heat (1889) Conduction of Heat. 5 follows the former table closely, his figures standing as follows, silver being taken as the standard = 100. (Madan.) Conductivity. Silver 100*00 Copper 74/00 Iron 12*00 Lead 8*50 Marble 0*15 Glass 0-05 Wood o-oi Hood quotes the second (Despretz's) table. When a material is subjected to heat it is supposed that the particles or molecules (of which the substance is built up) nearest the source of heat are set in motion, this movement being of a revolving character similar to what we have on a vast scale in our planetary system, bodies rotating and travelling around and about one another (but at present this is mere hypothesis, as the motion has never been detected by the most careful microscopic treatment). As the temperature increases the rate of motion is increased in like ratio ; but the mere increase and decrease of motion and proportionate increase and decrease of temperature do not accelerate or retard conduction in any important way, as the latter effect is due to a property possessed in a greater or less degree by the material itself, which either permits of a free motion of its particles which allows of a ready transference of the motion of heat, or the reverse. For the present purpose we may consider that the property of conduction only applies to the metal composing the boiler plates and that of which the pipes or heat-diffusing appliances are made ; conduction cannot be said to apply to the fire around the boiler or the water within it, nor the air outside the pipes or the water within them, it only applies to the material that separates the fire from the water, or the water from the air, respectively. If we could apply the fire heat directly to the water and transfer the heat from the heated water without the intervention of. any material, how- 6 Warming Buildings by Hot Water. ever good its conductive power may be, we should get much better results : that is to say, by a less consumption of fuel and in considerably less time. There is not the least doubt that heating by hot water would never have attained its present popularity if the materials so well suited for the purpose were not so cheap and easily obtained, for in cast iron we have a substance possess- ing ample strength, easy of adaptation as to form, size, &c., by the common process of casting, cheapness due to abund- ance, and what is more necessary, a good conductive power. Cast iron is of greater conductivity than wrought iron by a considerable degree, and what is objectionable in wrought pipes (even if of as little cost) is that its greatest conductive power lies with the grain or fibre and not across it, in the way it would be of the greatest use for this purpose. It is difficult to say which of the three modes of conveying heat is of the greatest importance in hot-water work, for each is most intimately concerned in the success or non-success of the work. If the boiler or pipes were constructed of any sub- stance possessing a low conductive power there would be an almost impassable barrier introduced at once, the heat being closely imprisoned within the apparatus, although ready in every sense of the word to dissipate itself, if the circumstances were favourable. Poor conductors of heat enter into the construction of nearly every apparatus that is erected, in some form or another, as it is not sufficient that we merely transfer some portion of the heat of combustion to the water and subse- quently to the place to be heated : we have to most severely consider the question of economy in fuel and labour and con- sequent wear and tear, and a hot-water engineer's good repu- tation is frequently based upon his success in this particular ; indeed, it is no uncommon thing for an apparatus to be either partially or totally unsuccessful, owing to its dissipating heat where the heat has no valuable use. First may be mentioned the great use made of firebricks in the construction of the flues surrounding the boiler (if the Conduction of Heat. 7 boiler is not an independent one), this material having the double advantage of poor conductivity and a refractory nature, so that although a flue surrounding a boiler is of course bounded on two sides, one by the boiler and one by firebrick, it is only on the boiler side that absorption of heat takes place to any material extent ; and the peculiar nature of the clay of which firebricks are made makes it well suited for the purpose owing to its good wearing properties under the influence of heat. Another instance of the utility of a poor conducting material is when some portions of the service pipes have to be carried along in cold situations (occasionally out of doors) where the radiation of heat is often worse than useless owing to the decrease of heat it necessarily occasions in those situations where the heat is required. In such instances the pipes have to be covered with some material or compound having a low conductive power so as to conserve the heat, i.e. retain the heat within the pipes, which will be spoken of more fully presently. Another important instance of the kind is when the boiler is of the independent description requiring no brick setting, these boilers being most liable to loss of heat in a way that is opposed to good results. It will be noticed that with all independent boilers, including those illustrated in this treatise, the whole outer surface, both of the portion that contains water and of parts constituting the fire-box, is fully exposed to the air and all its influences. In an actual experiment made with a vertical dome-topped boiler, it was found that a coil situated a short distance away took one-third longer time to heat when the boiler was exposed, than when it was covered with a poor conducting compound. It will be readily understood how quickly the heat is transferred from the fire to the outer surface of the boiler, and the next chapters upon radiation and convection will show clearly how soon the heat is disposed of when once it has reached this point. For some very obscure reason the word " non-conductor " has become quite common, through heedlessness probably, as 8 Warming Buildings by Hot Water. there is no such thing as a non-conductor of heat, although very many substances rank as exceedingly poor conductors, and on this account answer general purposes almost as well as a non-conductor would. Professor Tyndall once informed the writer that asbestos, which answers excellently as a poor conductor with ordinary heats, quite failed, in some ex- periments he made with very high temperatures even though an air space existed between the asbestos and the source of heat. There is another feature in the conductive power of iron to be considered, as its application is becoming more and more general, and with very satisfactory results. This has been very correctly named " diffusivity," meaning the power that iron has in diffusing heat over a large area (of iron) ; simply another name for conduction, but the result bears a different application. If we take a hot-water pipe and charge it with water at a temperature of, say Fig. i. 1 80, the heat at the outer surface will bear a close relation to these figures ; but if we add a number of gills or feathers to the pipe, as at Fig. I, the heat will instantly diffuse itself into these plates, and the result will be that in- stead of a small area at a high tempera- ture, we shall get a greater area at a lower temperature, that is to say, we shall get a greater radiating surface but giving off cooler rays of heat, and a greater surface for air contact, but the air will not be heated so greatly. We do not expect to get a higher aggregate temperature, as in both cases the results are only brought about by a certain quantity of water at 180, but by this means we are able to diffuse the heat about an apartment in a rather more equable manner. But the chief advantages are, that the lower temperature of the radiating surface prevents accidents, &c., when a person's hand or body comes in contact with it, and with a lower temperature we are less likely to get odours arising from the decomposition of any matters that may fall upon the pipes Radiation of Heat. 9 in the form of dust, &c. These things, and also the saturation of the air which is affected, are worth consideration in hot- water work, but in stove work they are of the greatest importance, as will be explained when treating these articles. When treating open fire-grates we shall speak of the disadvantages experienced by the good conductive power of iron, and the various means of obviating the difficulty. RADIATION OF HEAT. To clearly grasp the existing theory of radiant heat (radio, to emit beams or rays) we have to understand that there exists around us, in every conceivable space, an infinitely thin and subtile medium, which is called the ether (or the interstellar medium), which is quite independent of the atmo- spheric air, or, we may say, is mixed with it, and this medium is the means by which radiated heat, as also light, is trans- ferred or conveyed from a hot body to surrounding objects. Radiant heat is therefore the motion of heat transmitted to the ether, which motion is carried or propagated in the form of waves in straight lines from the source of heat. It is not at all necessary that air be present to effect the phenomena of radiation, as if we suspend a thermometer in a vacuum, and apply heat outside, or place a heated substance in the vacuum and the thermometer outside, or place both in a vacuum, we find that the transmission of radiant heat is still manifested ; consequently we must believe that this ethereal medium is of a totally different character to air or gases, as it cannot, apparently, be withdrawn from a vessel in the manner we should exhaust it of air. We have already mentioned that the fact of a material conducting heat satisfactorily, as iron does, is not sufficient to ensure success to a hot-water apparatus, for the simple reason that the heat brought to the surface of the pipes only, is practically useless, as to benefit by its presence we must have it striking against us and surrounding objects in the form of radiant heat, and it must also part with its heat to the sur- io Warming Buildings by Hot Water. rounding air. Silver pipes, as mentioned, would give the best possible results so far as conduction is concerned, but a highly polished silver surface stands the very lowest in a scale of radiating power, consequently this costly material would not, with its excellent conductive power, answer so well as plain black cast iron, as the following table will show : RADIATING AND ABSORBING POWERS OF SUBSTANCES. (M. Pouillet.) (The absorbing and radiating powers of materials are equal, but their reflecting powers are in exact inverse ratio.) Radiating and Absorbing Power. Lampblack 100 White lead 100 Glass 90 Cast iron, polished 25 Wrought iron 23 Zinc, polished 19 Steel 17 Brass, roughly polished II Brass, highly 7 Copper, either cast or deposited on iron . . 7 Silver, highly polished, either cast or \ hammered / ' (Leslie.) Lampblack 100 Water (by estimate) 100 Glass 90 Plumbago 75 Tarnished lead 45 Clean lead 19 Silver and copper 12 Neither of these tables gives a comparative figure for plain cast iron (unpolished), but from results obtained in practice this should stand at about 60, if the outer surface is untouched, i. e. having its own natural coating of oxide. From these tables it will be conspicuously noticed that polished metals are the very worst radiators, and on this account it is that kettles, urns, and the copper cylinders sometimes used in hot-water supply apparatus are, or should Radiation of Heat. n be, kept polished, to prevent loss of heat by radiation, the polished surface so very successfully preventing radiation. The writer's best remembered experience of this was the fitting up of an electroplated radiating coil in the hall of a gentleman's residence, and this was a most obvious failure, although no blame could be attached to the boiler, and the coil felt hot if touched, and succeeded in warming the air somewhat. The radiating power of a body is not due to its material substance, but to the nature of the oiiter film or skin ; so that if we coat a bad radiating but good conducting material with say lampblack, we shall get the best possible results. For example, silver has the highest conducting power, but the lowest degree of radiation ; but coat a silver pipe with lampblack, and we have the highest conceivable success, and the rougher the coating of black the greater the radiation, as a rough material presents a greater surface than a smooth one, and radiant heat (the dark rays) seems to leave a rough surface (which really consists of a great number of minute points) more freely that a smooth one. Lampblack is supposed to have no reflective power whatever, and consequently it is classed as a perfect radiator at least as perfect as any known at present. This has led to a belief that colour materially affects radiation of heat, which is correct so far as regards rays of heat that proceed from a luminous body, these standing in order from white to black, the lightest radiating the least, and vice versa. But this has no interest to the subject being treated, as we have only to deal with radiation from non-luminous bodies, and colour makes no difference whatever to the free radiation of dark rays of heat. This brings us to consider what is the best material to coat the coils and pipes of a hot-water apparatus with. It must be noted that the table of radiating powers given only applies to dark rays, that is, rays of heat proceeding from substances below about 500. Lampblack is doubtless the best of all materials to coat coils and pipes with, but this has an objection in the fact that 1 2 Warming Buildings by Hot Water. it does not increase the sightly appearance of an object, and consequently recourse is had to paint, which fortunately possesses radiating powers as nearly as possible equal to lampblack ; and for rays of heat proceeding from non-lumi- nous bodies, white paint will give about as good results as black, or any intermediate colour. Consequently, if we use the improved form of radiating coils (of which we shall speak fully presently) in a living-room, we are enabled to colour them to suit the surrounding decorations without any prejudicial effect upon their radiating efficiency. Two which the writer had erected in a drawing-room, and coloured cream and gold, with marble tops, were eminently successful, both for efficiency and good appearance. These ornamental coils are frequently bronzed for the sake of good appearance, and they act very fairly ; but for radiating power preference should certainly be given to paint, as the bronze, whether copper or an alloy like brass, is com- posed of poor radiating materials, as well as being of a polished metallic nature. A thick film of oil stands at "59 in the scale of radiating substances with lampblack at 100, and as the majority of metallic oxides (which go with oil to make paint) are good radiators, a coating of such a mixture is very satisfactory. There is a material which is an excellent radiator, but which, although not used in connection with hot-water work, is used to a fair extent upon stoves, and that is glass, which forms the glazed surface of tiles of nearly every description. Glass, it will be seen, stands at "90 in the scale of radiat- ing powers, but a great objection possessed by it, as also by the substance of all tiles, is their low conductive powers ; consequently, although the outer film of glass readily sends out its heat, the difficulty is to transfer the heat to the outer surface, and on this account a glazed earthenware pipe would be most objectionable as a radiating pipe, although the glazed surface itself cannot be found fault with. The question of the low conductive power of earthenware and fire- brick substances will be spoken favourably of presently, as it Radiation of Heat. 1 3 is a material largely used where escape of heat is to be prevented, and this is why an earthenware bath (unglazed inside) is so delightful to use. We have at present only spoken of radiant energy as existing at the extreme outer surface of the radiating media ; we now have to consider how the agreeable effect of the heat is experienced by the body. First, it is to be understood that radiant heat does not (so far as this subject is concerned) increase the temperature of the atmospheric air. It is most commonly thought that the heat radiated from a bright fire is warming the air, but this supposition can be disposed of by placing two thermometers a few feet from the front of the fire, one facing and one with its back to the source of heat, and notice the difference of temperature, although the same air surrounds both. But there is a more convincing and irre- futable proof of this in the fact that although on a summer's day the air might be warm near the earth, if we left the earth in a balloon for instance we should find the air get colder and colder as the distance increased, until at a high elevation (above the clouds) a thermometer would probably register a freezing temperature ; and yet all this time we should begetting nearer and nearer to the sun, which might be shining brightly all the while. Radiant energy is felt in the form of heat on all bodies, our own bodies included, and air is heated by coming in contact with objects that have been heated ; but in the case of the earth, we who are upon its surface have the benefit of the sun's heat agreeably transmitted to us owing to the presence of water vapour in the atmosphere, which fulfils two exceedingly beneficial purposes without which existence would be next to, if not quite impossible. Now, water vapour is a very great absorber of heat, and in this instance it firstly tempers the fierce heat of the sun that is radiated upon us, and secondly it effectually prevents the instantaneous loss of heat by re-radiation from the earth's surface and the objects upon it, which would take place if it were absent. If our atmosphere were what we may call pure, that is, free from the admixture of foreign substances, water 14 Warming Buildings by Hot Water. vapour in particular, the presence of the sun would cause a really scorching heat to be felt, and its absence would be instantly noticeable by the loss of heat and a most intensely bitter cold. As we get away from the earth's surface the atmosphere becomes less humid, and the sun's heat is felt and lost almost at the same instant, the air remaining excessively cold and robbing us of heat by convection (as will be understood directly) at a great rate. The peculiarity possessed by the atmosphere in not absorbing radiant heat (by which it would be made intolerably hot) is of particular benefit to mankind, whose nature is specially adapted to profit by it. Indeed it must be notice- able to every one that we require and are rendered comfort- able by a much higher temperature for our bodies than for the air we breathe, which is evinced by the pleasure most people feel in breathing the sharp air of a fine winter's day, provided the body is well clothed and so kept at a good heat. This naturally leads us to consider which form or method of heating is best suited to fulfil these natural and conse- quently most desirable conditions. Although each system will be treated fully hereafter, it may be mentioned that the methods are practically confined to four only, viz. open fires (radiant heat and air heated by contact with warmed objects) ; hot-water and steam pipes (radiant heat and air heated by contact with the pipes and by warmed objects) ; stoves (same as hot-water pipes, but with different and less pleasant results) ; hot air (air heated by contact with hot bodies and conveyed where required by pipes or conduits, and some radiant heat from bodies warmed by the air). Radiant energy is projected from the source of heat in the direction of a straight line, but its motion has been likened to a series of waves which continue in one direction irrespective of other influences, as Mr. Madan says, " like the waves on water pursuing their course uninterrupted by tides and other influences." This motion or it had better be called heat- loses its intensity very quickly as it leaves its source ; not that Radiation of Heat. 15 we may consider the heat itself to be lost, but it quickly diffuses itself over a wide area. Thus we get it over a larger space but at a lower temperature, and there is no objection to this, for we are enabled to heat a large space from one source of heat. As already mentioned, these rays pass through the atmosphere without affecting it, and their effect is only experienced on surrounding objects. Thus, in a room, the walls, furniture, and other objects receive the heat which impinges, so to speak, upon them, and they in their turn re-radiate the heat in various directions to various extents depending upon their radiating power and other properties, so that when we stand in a part of the room where the rays from the fire do not directly strike us we feel an equable heat (provided we are not near any rapid conductor of heat or near a window where a cold down-current nearly always exists, as will be explained later), owing to the dark rays of heat from the surroundings being projected in all directions. But immediately we get near the fire and obstruct some of the rays that come directly from it, we feel hotter on the side nearest the source of heat than we do on the side removed from it, owing to the greater intensity of that which we receive from the fire than that which we receive from the warmed objects the other side. A very good illustration that heat travels in straight lines, is to hold any object in front of us as we face the fire and notice how instantly the heat is cut off, and a minute observa- tion made at the moment would show that a greater heat would be felt from the objects at the back from which we have not shielded ourselves. If radiant heat did not travel in straight lines a sunshade or awning would be a very useless article. It has been very pertinently pointed out that this fluid theory of radiant heat, i. e. that radiant energy is transmitted by a subtile ether, existing in an intermingled state with the .atmosphere, and beyond the atmosphere (to account for the sun's rays being transmitted to the earth), may at some time be exploded like the fluid or material theory of heat itself (see p. 9). For this is practically the last of the fluid 1 6 Warming Buildings by Hot Water. theories, and is founded upon mere conjecture, as the fluid itself has never been detected, neither by weight nor other experiments ; and what may be considered as rather fatal to this supposition, is that radiation proceeds about as well in a vacuum as in the air, showing that although we can exhaust the receiver of a good air-pump almost perfectly, we do not apparently abstract this ether, notwithstanding that every other known fluid can be withdrawn readily, In hot-water work it is only the dark rays of heat that have to be considered, as no part of an apparatus, even upon the high-pressure system, is supposed to exceed about 350 external temperature, and is consequently far from being luminous. This is so far as concerns the pipes, but in the furnace of course the dark rays are absent, as all the heat pro- ceeds from highly luminous fuel. The surface of a boiler nearest the fire gathers heat in several distinct ways, viz. by radiation from the glowing mass, by contact with the glowing mass, which we might call absorption, and by contact of heated gases. Of course the greatest effect is brought about by radiation from, and contact with, the glowing fuel, which gives the water every opportunity to manifest its rapid power of absorption. Flame needs no consideration, as coke is the fuel invariably used (except at some special time, or under some special circumstances), but the hot gases evolved, which it is understood include the highly heated products of combustion (carbonic dioxide, carbonic oxide, &c.) are an element of some importance, as the flues which are carried round and about a boiler have no incandescent fuel within them, and the surfaces within these flues receive heat from the hot gaseous products only. Heated gases, it will be found, only do effective work in the boiler flues by coming into actual contact with the surfaces, which surfaces, if of an absorptive nature, take up some of their heat, and if by any means the heated products are able to es- cape without touching the surfaces in question, decidedly less good results will be obtained. It is peculiar to note that these gases manifest to a great extent a property which is very Convection of Heat. 1 7 noticeable with flame, and that is to avoid coming into actual contact with surfaces if there is room and a possible way to avoid so doing, so that if we surround a boiler with flues larger than a recognised efficient size, very little heat will be gained from what passes through them ; yet, on the other hand, we cannot successfully cramp the flues beyond a reasonable limit, as will be shown presently. CONVECTION. A knowledge of the two subjects, Conduction and Radia- tion, is of considerable necessity and interest in studying any mode of heating ; but where we employ water as the medium for the transmission of heat, the present subject, viz. con- vection, possesses greater interest than all, and a knowledge of it is absolutely necessary for the proper planning and carrying out such work. Convection (from conveho, to carry up) is described as " the act of conveying heat by the ascent of heated particles in a gas or liquid" Water and gases, in fact all fluids, are com- posed of one or more elements existing in the state of a mass of exceedingly minute particles, which are termed molecules, these particles having no cohesive or adhesive properties. In fact the commonly accepted notion is that there is a distinct repelling influence existing, which causes the particles, as of water and particularly of gases, to spread in all directions when unconfined. For instance, we might compare a mass of water to a mass of exceedingly fine sand, except for the pro- perty just explained ; for although the particles of sand are all free and quite independent of one another, like the particles of a mass of water, yet we can have a heap of the former, but no one ever saw a heap of the latter (except in a frozen state). One reason accounting for the heaping of sand, is that the friction amongst the particles, owing to their irregular shape, helps and in fact is the chief cause of their s-upporting one another ; and although no suggestion has been made as to the shape of water molecules, we cannot help thinking they must be c 1 8 Warming Buildings by Hot Water. spherical, which would then account greatly for their very perfect mobility, for if we took, say, a bushel of small coke (an irregular shaped material) and a bushel of glass balls, and emptied them on the ground, there is no doubt about the balls acting very much like a bushel of water would do, viz. spreading out in all directions, which the coke would not do. Fluids, however, both liquid and gaseous, possess the property of mobility in a most marked degree ; the particles have the most free and independent motion possible to con- ceive, not manifesting the faintest sign of friction between the particles, which we are naturally inclined to expect in every- thing, certainly solids. When water is agitated the particles glide over and under and around one another without interrup- tion or resistance in the slightest degree, and on this account, i. e. the absence of friction, water would want an enormous amount of agitation to raise its temperature perceptibly to an ordinary thermometer. We may therefore consider a body of water when un- disturbed and of a uniform low temperature, to be a mass of minute particles, all free to move by the slightest cause ; and if we take a glass vessel a large tumbler or an ordinary jar will do we can quickly investigate and become acquainted with the exact action of Convection. First, it is necessary to obtain a substance that will be visible in water (for water is invisible) without giving erratic results, and nothing is better than amber for this purpose, if ground to a very fine powder, as the specific gravity of this material is I 080 with water at I *ooo ; or the finest sawdust of some moderately heavy woods answers very fairly.* If we apply heat to the bottom of a * I have tried amber several times, and also mahogany dust ; the gravity of amber, however, either varies very greatly, or else we have a far greater number of imitations of this article than we are apt to suppose, and it is sometimes necessary to discard two or three pieces owing to their uselessness for this purpose. With mahogany dust there is very little objection ; it has a tendency to sink to the bottom (the greater portion of it), but the ascending current of water carries the particles up, which is exactly suited to the requirements. A substance that wholly floats .at the top of the water would not answer the purpose at all. Convection of Heat. 19 vessel charged with water with this dust material in it, we shall notice almost immediately that some of the particles are propelled upwards, and as the particles leave the bottom and lower part of the vessel, other particles will be noticed travel- ling down from the upper part towards the bottom, to take the place of those that have ascended. The exact action is as follows : the particles or molecules of water in contact with the bottom of the vessel are stationary before the heat is applied, but immediately heat is transferred to them they expand in bulk and are thus rendered lighter (bulk for bulk) than their fellow particles, with the consequence that they immediately begin to rise like any substance would that is lighter than its equal bulk of water. We may consider that these heated and lightened particles of water (although still of the same composition of water) act like a foreign lighter material such as cork, and insist upon rising to the highest possible point, until they have lost their heat and again become of the same bulk as the other molecules. As these particles rise they carry up the particles of amber with them, by which means the action of the water is illustrated. After but a very short time a steady circulation will be found to have set in, as at Fig. 2,* and this circulation will continue so long as heat is applied to the bottom or lower * It is very interesting to watch this phenomenon, its action is so regular, and the particles of solid matter (amber or wood) spring up from the bottom and travel round apparently without any reason or cause, yet in such a regular and uniform manner ; but it is most interesting to look at the action from the top, that is through the upper exposed surface of the water, the particles rising and falling like a stream of animalcula, all travelling in one recognised direction, and a peculiar result that will be noticed is, that notwithstanding the disturbance, i. e. the circulation of the water, the upper surface is undisturbed and perfectly motionless. Never was there a better illustration of the upper layer of molecules in a vessel of water forming a skin to the contents. As the water gains in temper- ature the bottom of the vessel will get encrusted (inside) with minute air- bubbles showing how the aeration of the water is disposed of, and rendering water that has been heated so flat and unpalatable. If mahogany dust is used the water will become impregnated with some of the brown colouring matter of the wood, but this is not objectionable. C 2 20 Warming Buildings by Hot Water. Fig. 2. ill"! part of the vessel. It is doubtful if this circulation would ever cease while heat is applied, as although we may suppose that the water would attain a uniform temperature eventually, this is not the case with a heating apparatus. With this latter a reduction in temperature takes place very soon after the water leaves the boiler, owing to the ready radiation of heat both by water and iron, as already ex- plained, and from the contact of cold air, &c. ; consequently there is always a dif- ference, more or less great, between the temperature of the water leaving and that entering the boiler ; the difference in tem- perature meaning, of course, difference in bulk for weight. This is the simple ex- planation of Convection as applied to water, but in a later chapter the subject will have to be dealt with more fully. There is no doubt that the rapid heat- ing of water and gases was originally attributed to Conduction a very reasonable deduction indeed, as it is this phenomenon that accounts for the transference of heat throughout the mass of all solids ; but in solids we can obtain a transference of heat to the portion furthest removed from its source, whether the heat be applied to the top, bottom, or sides, which is not the case with fluids, as can be simply tested with the glass vessel just referred to. If this vessel be rilled with cold water and a gas flame be applied to the top, it would be found to take a very great time before the least trace of heat reached the lower part, showing, as has been conclusively proved, that, water does not conduct heat at all willingly, and it has been classed as one of the poorest conductors. If on the other hand we took a vessel of hot water and placed a very cold substance at the top of it, a circulation would be noticed at once, as in this case we simply reverse the action of the convection currents ; the cooled particles being rendered heavier (bulk for bulk) than the hot ones, so that they Convection of Heat. 21 Fig- 3- instantly sink to the bottom and hot ones ascend to take their place, an exactly reverse process to that first described In an apparatus for heating purposes it will be readily seen that the vessel just referred to only illustrates the action of the water in the boiler, and although we may look upon the pipes from which the heat is radiated as mere extensions or continuations of the boiler, the way in which the hot water is conveyed (or conveys itself) into them needs a little explanation. If we construct an apparatus as at Fig. 3, which consists of a bottle with a cork stopper (which must fit tightly, and may probably require waxing over), with two glass tubes passing through the stopper, one reaching say three- fourths of the way to the bottom, and the other not projecting inside in the least degree (for reasons to be presently explained), and carry these tubes something like the illustration, we shall have a model apparatus of simple form, which will in its action explain everything very clearly.* When the heat is applied, the circula- tion will set in almost instantly, and it will set in at all parts, that is to say, it will not be confined to the boiler, but will, at the first indication of a movement, be seen travelling along the pipes in the direction indicated by the arrows. It is hardly sufficient to say that the motion is brought * The writer has adopted very humble materials in illustrating this apparatus, but they possess the advantage of acting with as great certainty as an elaborately constructed erection, and as the whole model is glass the result can be noted with greater accuracy than with any metal appliances, but if any one proposes investigating the matter thoroughly, it would be worth while having a glass boiler made. The object in having one pipe at a lower point in the boiler than the other is to ensure the regular circulation of the water in one direction, as will be understood ; if the pipes started level with each other a circula- tion would still set in, but there would be no certainty as to which would act as a flow pipe and which as the return. 22 Warming Buildings by Hot Water. about by the fact that heated water is lighter than cold of the same bulk ; it is really the other way about, as the phenomenon is wholly due to gravity, that is, the cold water being heavier that the hot, which, although a trifling distinction, has a considerable difference for the purposes of this discussion. The cold water having greater specific gravity than the hot, has a tendency to sink and find the lowest possible point by reason of its superior weight, so that when a particle of water becomes heated and rarefied in the slightest degree, it is in- stantly pushed away, so to speak, by its surrounding fellows whose weight is now superior and able to displace the lighter mass. It can be seen that hot water has no tendency to rise whatever without being compelled to do so by a superior force. If a vessel is filled with hot water, no part of it will raise itself beyond its natural level ; consequently the particles of warmed water that rise and constitute a convection current, take up this motion entirely by reason of their being urged in that direction by a crowd of heavier fellows all jostling and making their way to the lowest point by their greater weight or gravity ; and to use the expression attributed to Dr. Balfour Stewart, " Were there no gravity there could be no convection ; were it not for gravity it would be of no conse- quence what part of a vessel we heated, the effect of the heating would be always the same." This is a slight digression, but it is to make it more clear why the circulation or convection current sets up in all parts of an apparatus at once, instead of locally to the source of heat, as some might possibly suppose. When the layer of particles nearest the source of heat are rarefied and pushed up by the heavier particles surrounding them, this movement is as a matter of course (owing to the inelasticity of water) trans- mitted from the highest point, in the same way that there would be an instant movement from top to bottom of a tube or vessel of water if we withdrew some of its contents at the bottom. Consequently, in an apparatus as at Fig. 3, we shall find that the down and up flow will occur simultaneously from the highest to the lowest point in the circulating pipes, and Convection of Heat. 23 the result is the same whether the erection be large or small, simple or complex, provided its principle is correct. This is the result with a glass apparatus; with one of metal a little different conclusion might be arrived at, as although the heated particles are travelling up one of the pipes (the " flow " pipe), no heat will be felt externally for a little while, owing to its being absorbed in many ways by the pipes, &c., as we naturally cannot expect to have warmth from the outer surface until everything is warmed within. No precise table can be laid down to indicate the speed of convection currents, owing to their being varied by so many different incidental circumstances, but the speed can be theoretically calculated by a rule that will be given in the next chapter. However, it may be considered that no liquid exists that will give better results than water, owing to its perfect mobility, and to the fact that not the slightest degree of coagulation takes place however much it may be used over and over again, and it is a material that can be obtained readily and practically without cost wherever the apparatus happens to be situated. Many attempts have been made to utilise other liquid materials with the view of getting a higher temperature, and so obtain equal results with less pipe, &c., but at present nothing very satisfactory has been done, owing chiefly, no doubt, to the fluids which boil at a greater heat than water being of a more viscid or less mobile nature, such as a satu- rated solution of common salt or oil, &c. With these and all fluids of a like nature convection proceeds more slowly, and the more viscid its nature the slower it moves, until we have it in a solid or semi-solid state, when the particles will not circulate at all. Convection being caused by gravity, it follows that the more a material (i. e. its particles) expands by heat, the faster the convection currents must be, and it is on this account that the circulation of atmospheric air or any such light gas proceeds with great rapidity. A familiar experience of this is in gales, which, as well as gentle breezes, are 24 Warming Buildings by Hot Water. all convection currents ; that is, a flow of cold air conveying itself to some spot where a rise of heated air is taking place. Trade winds and ocean currents all proceed in the same way, except that one is convective currents of air and the other of water. Thus far we have considered the question of convection as applied to the water in the boiler and the pipes, this water receiving the heat from the fire, which is conveyed through the boiler plate by conduction to the particles of water that are in contact with it, these particles starting off immediately, and conveying the heat to the desired locality ; but before abandoning this subject we have to see how the heat is transferred from the pipes or coils to the surroundings, the heating of which has been the sole object of the apparatus. It will be readily understood that it is not sufficient to bring the heated water into the pipes, but this heat must pass through the substance of the pipe, as it readily does by con- duction (already explained), and it must freely transmit itself to the surroundings. Now it has already been shown that by radiation heat is transferred from a heated surface in direct lines in all directions, its intensity being governed by the good or poor radiating powers of the surface coating. With hot-water pipes, in addition to this, we have another mode of heat transmission from the surface, viz. by convection, that is, the heating of air particles in contact with the pipe and the consequent circulation of air as explained with water, excepting that with air the action is very much quicker with equally rapid distribution of the heat. This takes place quite independently of the heat emitted by radiation, and it is the argument for and against both open fires and hot-water pipes by grate-makers and hot-water engineers respectively. The grate-maker's contention is that open fires give the only natural result (that is a result exactly similar to that experienced by the sun), by reason of their imparting heat to the body and surrounding things, rendering everything agreeable to the touch and to our feelings and senses generally, without materially (we may say perceptibly) Convection of Heat 2 5 increasing the temperature of the air, and certainly without altering its general character ; whereas with any method of heating by hot water the cheerful brightness is lost, radiant heat (the congenial heat) is obtained in a less degree, and we have warmed air conveyed to our lungs which is not supposed to impart such a feeling of vitality as a cooler atmosphere ; and further, that in increasing the temperature the saturation of the air, i. e. its volume of watery vapour, is not increased proportionately at the same time as would be the case in nature, so that a sense of dryness may be supposed to exist. This is a good list, and a rather strong case for the grate- maker, and although the hot-water engineer is willing to contest this argument strongly, it must be contended that his theories are not quite so forcible and do not appeal so readily to an average person as the grate-maker's ; but for one par- ticular purpose the hot-water engineer will be seen to have much the best of the contest. The advantages claimed for heating by hot water may be summed up as follows. By the most ordinary attention an equable heat can be obtained all the day, and if desired all night, so that at no time need any part of the house be cold during early morning, for instance. The heat can be dis- tributed anywhere and everywhere, so that passages are as comfortable as the rooms. As just mentioned, the heat does not fluctuate, as must be the case with grate fires. There is less need of attention, cleaning, &c. (but it must be mentioned that an apparatus upon even a moderate scale needs a fairly experienced person to attend to the stoking). The loss of the sight of the fire is quickly become used to. As the heat of the pipes (of the low pressure system) is very rarely beyond 180, the air is not raised sufficiently in temperature to make a noticeable difference in its moistness, not even to those with bronchial affections, who would be the greatest sufferers. This, however, is open to objection, as the writer has been told more than once that the difference is noticeable to these sufferers, and this is partly borne out by the hot-water engineer sometimes dropping this argument and substituting, ' . 26 Warming Buildings by Hot Water. " That if a dryness of the atmosphere is noticed, the remedy is simple, by the introduction of vaporising pans or troughs." And lastly, for conservatories and horticultural work it is eminently suited beyond all other methods by its regu- larity of temperature, the simple method of application, the ease with which the heat can be regulated as the weather or outer temperature varies, and the exceedingly simple and natural means of increasing the humidity of the air or over- saturating it with moisture, and so rendering it exactly like what nature provides where the earth is most prolific of ver- dure. It is most noticeable that wherever both warmth and a moisture-laden air exist, there abound all nature's best productions in a degree bordering on extravagance. This is so different to our English climate with its prevalence of dry cold winds. There are other minor points claimed by both sides, but for general agreeable results in private residences a combina- tion of the two methods is very satisfactory, provided strict economy in fuel is not of primary importance. It will probably have been understood by the action of convection in water that air instantly makes a move in an upward direction when it has absorbed heat, partly account- ing for the great heat experienced near ceilings when a room is comfortably warm near the floor. The convective action of air does not proceed wholly from the pipe surfaces, for we have it from every other object that is warm, whether these other objects have received their heat by radiation or other- wise, so that even with open grates we have warmed air to some extent from its contact with our warm bodies, walls, furniture, and general surroundings. Air may be said to receive heat by contact only, and this is what it is continually doing, robbing everything of heat that it comes in contact with (unless it be of a less temperature than itself, when it gets robbed in its turn). This, it may be mentioned, is an argument used and worn threadbare by some hot-water engineers as against the open grate, viz. that radiant heat warms one side of our body whilst the cool air is abstracting Convection of Heat. 27 heat from the other side, whereas with hot water the air is directly warmed to a temperature beyond actual coldness. This argument, although very forcible to a lay mind, is not strictly correct, as although we get a greater heat one side than another it is only while we directly intercept the hottest rays. If we move out of range of these rays we find a fairly equable heat in all other parts of the apartment. It simply remains to be said that as heated air takes an upward direction the instant it is rarefied, all hot-water pipes and such heating media require to be near the floor, as at the ceiling it would indeed be a very long time before their good effects were noticeable below. It is this action that brings about the up-draught that is found in all chimneys, and it is an indirect reason why a baker's and pastrycook's oven has to have a bottom heat to ensure lightness to the articles baked. 28 Warming Buildings by Hot Water. CHAPTER II. CIRCULATION OF WATER, ETC. UPON THE CIRCULATION OF WATER Theory and phenomena Tred- gold's explanation and Hood's criticism and theory Actual cause of circulation Variation in results Motive power Table for deter- mining motive power. CONNECTING PIPES TO BOILERS Direction of pipes Multiple flow and return services Disadvantages of hori- zontal pipes Various simple forms of apparatus and their leading features demonstrated The most practical method. THIS subject claims the attention of all who are in the least degree interested in hot-water works, as a knowledge in this direction is of primary importance in their design, except, perhaps, in cases where the apparatus requires to be of the most ordinary and commonplace description, in which in- stances the work is most usually left to workmen, who having erected many such before, are able to copy their previous undertakings without troubling to consider the reasons for the success they may probably bring about. When, however, the requirements are out of the common and some special form of apparatus, or some unusual feature is to be carried out, failure must, almost as a matter of course, ensue, unless the designer is properly and well acquainted with the different rules that govern the work, and particularly the phenomena of circulation. Hood goes to some length to explain and make this subject clearly understood by the reader, and much profit can be gained from his description. He first points out that previous to his undertaking the task, Mr. Tredgold was the only person who attempted to describe the cause of the cir- culation of water, which he did as follows : " If the vessels A, B (Fig. 4) and the pipes connecting them be filled with water and the heat be applied to the vessel A, the effect of Circulation of Water. 29 heat will expand the water in the vessel A, and the surface will in consequence rise to a higher level a d, the former general level surface being b b. The density of the fluid in the vessel A will also decrease in con- sequence of its expansion, but as soon as the column c d (above the level of the centre of the upper pipe) is of greater weight than the column />, motion will commence along the upper pipe from A to B, and the change this motion produces in the equilibrium of the fluid will cause a corresponding motion in the lower pipe from B to A." This explanation is far from being clear to the average mind at first reading, but to put other words to what it is intended to convey (with the hopes of making it more easily understood, if possible) it has to be explained that in this argument it is supposed that from the point c, which repre- sents the centre of the upper pipe, to the point b, which represents the normal ^/^/-water level (these two points are represented in exactly the same position at e and b or e and /), there exists a certain height of water, say 2 inches ; when the water is heated in A, the expansion which takes place increases this height of water by, say, another inch (to a d) ; this 3 inches is then sufficient to outbalance the 2 inches at the top of vessel B (viz. from e to/), and consequently forces itself along the upper pipe in that direction, making a proportion of water travel along the lower pipe from B to A. This, perhaps, is a lengthy explanation devoted to what Hood very correctly points out to be an erroneous theory which will not account for the circulatory action in every case, and he quickly explodes the matter by a description he gives of an apparatus similar to Mr. Tredgold's illustration, but which will not admit of the water rising above the normal cold- water level when heat is applied, and which would not work at all if the circulation depended upon the action described. The apparatus in question is as Fig. 5, which it will be instantly seen bears the closest resemblance to the other with 30 Warming Buildings by Hot Water. the addition of an overflow pipe, and two stop-taps. The de- scription, which is in every way clear and worthy of repetition, is as follows : " Suppose the apparatus, Fig. 5, to be filled with cold water and the two Fig. 5. y? stopcocks to be closed ; on ap- " ~W c PI plying heat to the vessel A, the B water it contains will expand * ^J in bulk, and a part of it will flow through the waste-pipe x, which is so placed as to prevent the water rising higher in the vessel A, than the top of the vessel B. The water which remains in the vessel A, after it has been heated and a portion of it has passed through the waste-pipe x, will evidently be lighter than it was before, while its height will remain un- altered. Suppose now, the two cocks/ g to be simultaneously opened, the hot-water in the boiler A will immediately flow towards B through the upper pipe, and the cold water in B will flow into A through the lower pipe, although by the hypothesis previously alluded to, unless the water in the vessel A above the pipe centre C were heavier or rose to a higher level than the water in the vessel B, no circulation could take place, and in this case another explanation must be found. The power which I consider explains this action is, let us suppose heat to be applied to the boiler A, Fig. 5, a dilatation of the volume of the water takes place and it becomes lighter ; the heated particles rising upwards through the colder ones, which latter sink to the bottom by their greater specific gravity, and they in their turn become heated and ex- panded like the others.* As soon as the water in the boiler begins to acquire heat and to become lighter than that which is in the opposite vessel B, the water in the lower horizontal pipe d is pressed by a greater weight at z than at y, and it therefore moves towards A with a velocity and force equal to the difference in pressure at the two points y and z. The water in the upper part of the vessel B would now assume a lower level were it not that the pipe c furnishes a fresh * See Convection, Chapter I. Circulation of Water. 31 supply from the boiler to replenish the deficiency. By this unequal pressure on the lower pipe, the water is forced to circulate through the apparatus, and it continues to do so as long as the water in B is colder, and therefore heavier than that in the boiler A." The writer has made this rather extensive extract from the last edition, chiefly by reason of the argument being so soundly dealt with, and were it put in other words the ultimate amount of information imparted would have been about the same. It is so very necessary to impress upon the student that it is the superior weight of the colder water, and this alone, that brings about the movement of the particles, and ultimately the mass, of the liquid. It seems so natural to hear it argued that it is the fact of the hot water being lighter than the cold that brings about the circulation, whereas it is just the reverse. A distinction without a difference, some may say, but it is far from being so, as every practical man knows how many errors are fallen into through considering the ascending properties of hot water instead of the superior descending force of cold water, when working out some problem. If we take a vessel of heated water (at any temperature) that is not being subjected to further heat, we shall find that it exhibits exactly the characteristics of cold water. So far as movement is concerned the particles will remain at rest if the vessel is not shaken, and it will be seen that the water has no tendency to rise, not any particle of it, yet from the very generally accepted notion that hot water has the power of rising, we might almost expect that the vessel would have to be sealed at the top to prevent it escaping. If the vessel of hot water just referred to has some cold body placed at the top, a piece of cold metal or ice for instance, so that the upper stratum of water is cooled, a circu- lation will instantly set in (similar to that which would ensue if heat were applied at the bottom), as in this case we cause cold particles to be above the heated particles, and this being contrary to the laws of gravity the former by their superior 32 Warming Buildings by Hot Water. weight displace the latter and find their way to the bottom, leaving a fresh supply of warm particles to come in contact with the cold object, to be cooled and sink in their turn, and so on. This perhaps will give a clearer idea of how it is that the circulation of fluids is due to the superior weight of the cold particles, and not to the lightness of that which has been heated. It is simply the result we get when we place different substances in the pans of a pair of scales : the pan which contains the greater weight sinks, and that with the least weight rises, not because the lighter article has any inclination to rise, but because it is impelled by the superior force out- balancing it. This difference in the weight of two columns or bodies of water, causing movement in opposite directions, has been designated the " motive power " of the circulation, a name which is of course strictly correct, yet does not at first sight give a very good conception of its meaning. Hood has set out a scale or table showing theoretically the speeds obtained in circulation by certain differences in temperature, which table will be quoted directly ; but it is next to impos- sible to set up a standard for practical purposes, owing to the ever varying conditions that are met with, no two apparatuses working under the same circumstances, and even one apparatus will not give exactly the same results always, as it maybe influenced by changeable external conditions. This will show what a difficult task it would prove to any one to compile any reliable information in this direction ; and even if it were possible its adoption would not be general, as the speed of circulation does not always govern the success of an under- taking, although as a rule it is considered that an apparatus is well designed and erected when all the pipes and radiating surfaces are at a high temperature soon after the fire is started ; but this would be due chiefly to the size and power of the boiler, the skill of the attendant, and to some extent, the quality of the fuel, and also whether the pipes were in a temperate or very cold situation, and several other circum- stances, as will be learnt presently. Circulation of Water. 33 Perhaps the greatest drawback to the adoption of any table of this kind would be its difficulty of application. In the first place it would be necessary to complete the erection of the apparatus in every part, then charge it, and when this was done it could be very easily tested in the ordinary way to see if it fulfilled the designer's expectations, and gave the desired temperature. If it did this no further trouble would be needed, whereas if we tested the speed of the circu- lation and it proved satisfactory, it would by no means indicate the success of the work, as it would not tell us if there was sufficient pipe or radiating media, nor would it tell us if the pipes were well placed, in fact it would prove misleading. In dwelling upon the non-practical utility of the table referred to, it is with no desire to underestimate its value in other ways, and apart from its scientific use it is desirable information to impart as showing exactly what constitutes motive power in hot-water circulation. DIFFERENCE IN WEIGHT OF Two COLUMNS OF WATER, EACH ONE FOOT HIGH, AT VARIOUS TEMPERATURES. (Hood.) Difference in Temperature of the two Columns Difference in Weight of two Columns of Water contained In different sized Pipes each ONE FOOT in height. of Water, in j r Fahrenheit's scale. i in. diam. z in. diam. 3 in. diam. 4 in. diam. Per square inch. o grains.' grains. grains. grains. grains. 2 I'S 6-3 I4'3 25^ 2-028 4 3'I 12-7 28'8 5I-I 4-068 6 4*7 19-1 43'3 7 6- 7 6-108 8 6-4 25-6 57'9 I02-5 8-160 10 8-0 32-0 72-3 I28-I ICT2OO 12 9-6 38-5 87-0 I54'I 12*264 14 II-2 45 'o 101-7 180-0 14-328 16 12-8 5 J *4 116-3 205-9 16-392 18 14-4 57*9 131-0 231-9 I8-456 20 16-1 64*5 i45'7 258-0 20-532 The above table, on account of its accuracy, may well be considered a testimonial to the exceeding care exercised by Hood in compiling his data. 34 Warming Buildings by Hot Water. The above table has been calculated upon the difference in the temperatures of from 170 to 190, these two tempera- tures being about the heat that is obtained in a well-con- structed apparatus when in full work. This table, it will be noticed, gives the difference in weight between water at two different temperatures per foot in height, so that in arriving at the actual motive power exerted in an apparatus, we must take the height from say the centre of the return pipe, where it enters the boiler, to the top of the flow pipe, where it ceases to travel vertically Fi s- 6 - as at a, Fig. 6. This distance varies from ^. 3 a few inches to three or four feet in ^ common horticultural work ; taking an apparatus of an ordinary kind we will sup- pose this distance is three feet. We next have to ascertain the temperature of the water that enters the boiler from the re- turn pipe, and that which leaves the boiler by the flow pipe, both temperatures to be taken at points as near to the boiler as possible. Supposing the pipe to be 4-inch, and the difference to be 16, we get from the foregoing table 205 grains per foot, x 3 = 615 grains = \\ ounce, and this weight, which will strike the reader as being exceedingly trifling, constitutes the motive power of the circulation in an apparatus. This very small difference in the weights of the water is, however, under ordinary circumstances, capable of setting up a tolerably rapid movement, notwithstanding that in the average apparatus there may be as much as 210 gallons = 2100 pounds of water to be made to circulate. In water, fortunately, we have a material peculiarly adapted to this purpose, as owing to its perfect mobility, friction does not play a very important part in its passage through the pipes ; if it did, failure would be inevitable. From the results just explained we gather two points of importance : first, that by increasing the difference in tempera- ture of the water entering the boiler by the return pipe, and Circulation of Water. 35 that leaving the boiler by the flow pipe we shall obtain an increase of motive power (i. e. the speed of circulation) ; and, secondly, that the more we can carry the flow and return pipes in a vertical direction, the faster will the water circulate, with pro- portionately better results. When an apparatus is first started (by applying heat to the boiler), the results are quickened by the fact that a considerable difference in temperature exists between the water entering and that leaving the boiler just at this time, as all the water passing in from the return pipe is quite cold ; but after the whole is heated up a less difference exists, but the water continues to circulate at about the same speed, owing to some extent to the impetus given it. It does not always follow that the more the fire is urged the greater the speed of circulation, as although the water will leave the boiler at a higher temperature (and diffuse a greater heat), yet it will return into the boiler at a higher temperature also, so that the difference in gravity between the two columns remains almost the same. It is most wonderful to note what an exceedingly low degree of heat will bring about movement amongst the particles of water. In any of the simple forms of apparatus already referred to, it will be noticed that particles of water commence to rise almost instantly the heat is applied, hardly allowing time for the heat to pass through the substance of the vessel, and when once the circulation is established, many particles will be noticed flying upwards at a velocity that could scarcely be followed with the eye if the water was not confined to such a small space. This bears out the theory that not only is there an absolute want of cohesion amongst the molecules, but there must be a repelling influence exerted, otherwise how could such an extraordinary absence of friction be manifested ? In considering the small amount or value of the power that produces a circulation in such a large bulk of water it naturally brings to mind, as Hood very wisely points out, that a trifling obstruction or error in workmanship must have a very prejudicial effect, or probably ruin the efficiency of the D 2 ' 36 Warming Buildings by Hot Water. work. But it is rather unusual to hear of such failures ; that is, they are very small in number compared to the successes, notwithstanding that there are about as many such under- takings working with a low motive power (nearly all horti- cultural works) as with high. With careful, i. e. thoughtful workmanship and attention to the rules laid down, success nearly always ensues as a matter of course. CONNECTING PIPES TO BOILERS. One of the most necessary rules to be observed in hot- water works is, as to the point at which the flow pipe is connected into the boiler. From what we have learnt of the action of convection \hzflow pipe should be connected up at the top of the boiler in readiness to convey away the heated particles of water in the direction required ; but merely con- necting this pipe at a high point is not sufficient, it must be connected at the very highest point, as at Fig. 7 for instance. Fig. 7- Fig. 8. The reason for this may not be apparent to the uninitiated, and it is therefore necessary to explain that supposing the^ze; pipe to be connected at some lower point, as at Fig. 8, we should then be unable to expel all the air from the boiler. In other words, we could not fill the boiler with water above the top of the flow pipe, as shown, as unless the air be expelled, we cannot get water to enter, for both air and water cannot occupy the same space at the same time, and this accumulation of air will prove a great obstacle to the free circulation. Now if we placed an air cock at the point Circulation of Water. 37 marked a, we could quickly dispose of the air for the time being, and get the boiler quite full of water, but it would only give temporary relief, as water, particularly in cooling, readily absorbs air, and when heated parts with it again, and the air may always be looked for at the highest points, and conse- quently this air cock would require fairly constant attention. If, on the other hand, we put an air pipe at the point a, the difficulty experienced by air collection would be overcome (this pipe having an open end above the level of the supply cistern), except that it is against all recognised principles to start the flow pipe horizontally if the work is of any magnitude ; for small works it is permissible (see the Loughborough boiler). After starting the flow pipe from the extreme top of the boiler,* it should be continued in a vertical direction as far as it is possible, so as to favour the motive power to the greatest extent, although in many horticultural works there is often- times only room for a few inches of vertical pipe, a bend having sometimes to be placed Flg * 9 * directly on the boiler, as Fig. 9. All the vertical pipe in an apparatus goes to increase the motive power and the consequent quicker results ; that is to say, if the pipe rises one foot from the boiler before it is carried horizontally, and then it rises another foot and then another, we can calculate upon having three feet of vertical pipe, although it is not all immediately near the boiler. All vertical pipe aids in increasing the circulation ; horizontal pipe does not aid in the least wherever it is situated ; in fact, it is the reverse, owing to the friction it involves, and all matter, sediment, &c., collects in these pipes. In many apparatus it is found desirable to have two and even more flow pipes. This can be done with every satisfaction, and the writer is rather in favour of this arrange- * If it is a wrought-iron pipe screwed into the substance of the boiler, the pipe must on no account be screwed right through so as to project inside, otherwise the objectionable accumulation of air must ensue. 38 Warming Buildings by Hot Water. ment, where it is convenient, and the circumstances make it desirable, in preference to the one flow pipe and its many branch services. The position in which the return pipe enters the boiler is not so important as the flow pipe, but at the same time it should not be brought in anywhere. The usual and correct place to bring it in is close to the bottom of the boiler, situated about centrally from front to back, as Fig. 10, but a system Fig. 10. Fig. ii. that is at all extensive has usually two returns (although but one flow), and this practice is to be highly commended as equalis- ing the action in the boiler, and it also reduces the likelihood of fracture of the boiler plate.* The flow pipe, which, as we have already explained, starts from the top of the boiler, is taken vertically as far as possible, and then t it is usually continued at right angles, i. e. hori- zontally ; but every practical man tries to give the horizontal pipe a slight rise where at all possible, if only an inch or two in fifty feet, as there is then a natural inclination for the water in the return pipe to aid in the motive power ; and though * It is found that with very many boilers that are taken out fractured, and which have only one return pipe, the fracture has occurred on the side opposite to that where the return is connected, as shown at Fig. n, the fracture being due to an accumulation of sedimentary deposit at this point which has kept the water from having free contact with the metal, thus ending in the destruction of the fibre by the heat. This deposit could not have occurred just there had there been a return pipe at that side. The fracture shown is exaggerated as to size, and marked a. \ We shall deal with horticultural work first, and speak of the domestic systems, pipes or coils, in which a great deal more vertical pipe is obtain- able, presently ; but the same general principles apply to .both. Circulation of Water. 39 the inclination be trifling, it is better than a perfectly hori- zontal pipe in which we may suppose the water remains quite inactive unless propelled by another force. This gradual rise is continued to the farthest limit of the apparatus if possible, as in Fig. 12. It may be mentioned that it is usually possible Fig. 12. to do this if care be exercised in planning the work, and as every glasshouse for horticultural purposes has, as a matter of course, to be heated, the builder (who may also do the hot- water work) arranges the structure to the best advantage, putting the boiler pit at the lowest point ; and where there are a series of houses it is very advantageous if they can be put on slightly rising ground so that each house is some inches higher than the preceding one. There is an idea rather prevalent, especially amongst work- men, that it is necessary always to keep the flow pipe above or over the return as shown at Fig. 12. This is not really necessary, although preferable, but it is not always convenient and sometimes hardly possible, and when pipes are carried in shallow trenches or laid beneath gratings it is commonly necessary to lay them flat side by side. If, however, it is required to carry them along the side of a wall, then they are placed one above the other, but if there were more than two pipes it might occasionally prove awkward to connect any branch services required. In any case if the flow pipe rises to a certain height above the boiler the motive power will be the same whether it be carried above the return or whether they be carried side by side, or in other words, either arrange- ment will prove equally satisfactory under similar general conditions. 40 Warming Buildings by Hot Water. There can occasionally (though rarely) be met with an apparatus in which the return-pipe is brought back over the flow as at Fig. 1 3 ; this is, according to general supposition, opposed to good principles, Fi s- J 3- and the general verdict would be that the apparatus was the result of employ- ing insufficiently skilled labour, as possibly might be the case, but whatever com- ments might be passed, the apparatus (if all its other features are favourable) will be found to work satisfac- torily, and this should be sufficient to silence opposition. Now in an apparatus as illustrated, the flow pipe will act as a flow pipe * up to the point marked a (supposing the pipes have a gradual rise to this point, as should always be the case if any way possible, as before explained), and from this point the water will commence to fall (constituting it the Fig. 14. " return ") and by its gravity produce the needed circulation. Now in this case we get exactly the same length of hori- zontal and vertical pipe in the return as if the apparatus were constructed as at Fig. 14 (which is a copy of Fig. 13 with the position of the pipes altered) ; consequently exactly the same * It sometimes seems difficult to fix the point in an apparatus where the flow pipe terminates and the return pipe begins, especially as one is merely a simple continuation of the other ; but it is usual to consider the flow pipe as extending from the top of the boiler to the highest point in the apparatus, and from this highest point the continuation of the pipe is con- sidered to be the return even in a form such as Fig. 20. Circulation of Water. 41 results are obtained practically, and in theory we may expect results of a little better nature owing to the whole of the vertical portion of the return pipe being near the boiler, as will be understood directly. It is not by any means intended to recommend this arrangement of the pipes in preference to the customary method, for in the first place the difference in actual results would not be appreciable, nor could it be detected at all except in a very large undertaking, and then only to a trifling extent, and to advocate such a change for practically no benefit what- ever would be useless and would lead to endless trouble and confusion amongst workmen. This unusual arrangement is merely described to show that were it necessary it might be carried out without hesitation ; even a branch service from an ordinary apparatus could be so carried if particularly con- venient. In support of our view of the importance of having the whole of the vertical portion of the return pipe as near to the boiler as can be arranged, we cannot do better than quote Hood's words, on account of the very lucid manner in which he deals with this much disputed question.* He says : " As the water in the pipes is constantly parting with its heat both by radiation and conduction, while that in the boiler is as continually receiving additional heat from the fire, an equality of temperature never can occur ; consequently, as the circulation is caused by the water in the descending pipe being colder and therefore heavier than that which is in the boiler, it follows, as a necessary consequence, that the colder the water in the descending pipe shall be relatively to that in the boiler, so much the more rapid will be its motion in the pipes. In an arrangement of pipes as Fig. 15 the water in the descending pipe c d having to come a greater distance * This question is very much debated even at this present time, and even by those who profess to be authorities upon the subject, but who, it must be inferred, lack some of the more preliminary knowledge necessary in discussing the matter. The theory established by Hood 'is strictly correct in actual practice, and can be relied upon. T7SI7BRSIT7 42 Warming Buildings by Hot Water. before it descends to the lower part of the boiler than when the pipes are arranged as Fig. 16 ; it will of course be colder at the time of its descent in Fig. 15 than Fig. 16, and there- fore the circulation will be more rapid."* Fig. 16. It will be seen very clearly that the water in the descending pipe (which is furthest from the boiler) in Fig. 16 must necessarily have hotter water in it than when the water has to travel a still greater distance before it descends, as Fig. 15, and has therefore lost more of its heat. This can be shown still more clearly by spacing off the pipe and supposing that Fig. 17. 175 170 165 160 1 ., 5 j r [125 130 135 14-0 L WS ISO the water, by radiation, &c., loses five degrees of heat in traversing each length of space so marked. In Fig. 17 we will suppose the water starts from the boiler at 200 and * As Hood remarks, it is very necessary, when studying this work, to avoid the erroneous hypothesis that the motion of the water commences in the upper pipe instead of the lower one. Circulation of Water. 43 returns into it at no ,* the water losing five degrees of heat each space it passes through. Now let us also suppose that for each five degrees of temperature lost there is an increase of weight of 20 grains, we can then see almost at a glance that in Fig. 17 the water when it reaches the descending pipe Fig. i 8. 130 IBS 180 175 170 165 160 155 r n ^ -ISO - J 125 130 will be 300 grains heavier (for a given bulk) than when it issued from the boiler, whereas in Fig. 18 it will be but 170 grains heavier and so proportionately less in motive power. Fig. 20. Figs. 19 and 20 show two methods of which there will occasionally be found advocates who contend that better results are obtainable by these arrangements than if the work is carried out in the ordinary way. It should be first mentioned that only in a simple form of apparatus could either of these methods be adopted, as any * These are, of course, supposed temperatures. 44 Warming Buildings by Hot Water. system of branch or secondary services would be almost impossible unless the circumstances happened to be just favourable. With Fig. 19 the contention is that instead of carrying any portion of the return pipe horizontally, which is of no assistance to the motive power, the return should be made to slope down all the way, commencing at the termina- tion of the flow pipe, and ending at the boiler, as shown, so that the water commences to exert its downward force from beginning to end of this pipe, no portion of the pipe being valueless as regards assisting in the motion of the water. This, it must be admitted, makes up a very fair case for the advo- cates of the method, but upon analysis it is very weak, and the method recommended (Fig. 17) will give the best results practically as well as theoretically. If we space this apparatus off as we did the last, we shall find that in the return pipe we have an average tempera- ture of 135, which, according to the method adopted, repre- sents water having a gravity superior to that just leaving the boiler by 260 grains. Now, although the return pipe of this apparatus slopes a long way, the actual fall it has is no more than in Fig. 17, so that to get comparative results in each case we must take the average temperature of the water in the return pipe of each system (not allowing horizontal pipe to enter into the calculation in either instance), and that which shows the least temperature has the greatest motive power, as in each case we show the water leaving the boiler at the same heat, viz. 200. In the apparatus now being described we get an average temperature of 135 in the sloping return pipe, representing an increase in weight of 260 grains, as already stated. If we take the average of Fig. 17 (the style of apparatus most recommended), we get an average temperature of 120 in the active part of the return pipe, and this represents an increased weight of 320 grains,* which it only remains to be added * It is desirable to again remind the reader that these temperatures and weights are purely supposititious, although not such a great way from those actually found. Circulation of Water. 45 conclusively proves that it is a more efficacious arrangement than that with the sloping return as in Fig. 19. This plan of sloping the return pipe in the manner shown would give better results than erecting the apparatus as at Fig. 1 8 ; in fact it would be equal to putting the descending portion of the return pipe half-way between the boiler and the termination of the flow pipe, as Fig. 21. Fig. 21. Apart from the question of effectiveness, this method has hardly ever been adopted, owing to the trouble that must necessarily ensue when an apparatus is not confined to a few straight lines of pipes. In Fig. 20, which Hood illustrates and very clearly explains, we should get worse results than with any method yet explained ; yet, strange to say, there are a good many people who, if not quite positive, are quite ready to give an opinion in favour of having the flow pipe commencing to descend immediately after it leaves the boiler, the contention being that, by making the pipes almost wholly the return service, the motive power will be aided proportionately. This argument, however, is not sound, as in the first place, although the flow pipe is not continued to the further end of the apparatus, yet what we may call the active part, i. e. the ascending column of the flow pipe, is not disposed of, and, as explained with the last method, the sloping pipe, although perhaps extending a long way, has only an actual fall of two or three feet, and this fall takes place where the water is of least weight, so that by the method used in calculating the results obtained in the other systems, we shall find that the effect obtained is the same as constructing an apparatus as Fig. 22. There is but one way of making the system less effective (without wholly 46 Warming Buildings by Hot Water. destroying its efficiency), and that would be to make the apparatus as this last illustration, but with the descending pipe still closer to the boiler. Any one of the methods dealt with will work that is to say, the water will circulate within Fig. 22. them, and in a small apparatus such as we should erect in a greenhouse, it is doubtful if any difference in results would be perceptible ; but in an undertaking of even a moderate character, a deal of trouble might arise with the less efficient methods, as not only does the apparatus require to be working at its best, with the least expenditure of fuel and labour, but with the increased quantity of pipe and its ramifications, a greater resistance is opposed to the motive power, which, if not great, might be actually nullified, for we have seen that in horticultural works, which are very dwarfed as to height, the circulation is the result of but a few ounces difference in weight of the entering and outflowing water at the boiler, under favourable circumstances. The principle described under Fig. 17 is considered and been found the best, both by theorists and practical workers. ( 47 ) CHAPTER III. V . AIR IN PIPES SUPPLY OF WATER EXPANSION OF PIPES. AIR IN PIPES. Accumulation and dislodgment Air pipes and cocks Stoppage of air vents. WATER SUPPLY. Provision to replenish loss by evaporation, also when water is drawn off Expansion of water by heat Capacity of supply cisterns Overflow Position of cistern Service pipe and connections Rain or hard water Sediment or lime deposit Useful appliance for small purposes Flushing and cleansing. EXPANSION OF PIPES. Provision for expansion Measure of expan- sionPipe bearings. THE preceding chapter has only dealt with the most elementary forms of apparatus, yet before proceeding to describe those which may have necessarily to be executed a little differently from the customary way, and to what extent such variations can be carried, it is necessary to speak of a subject which plays an important part in the execution of these works, and which should be explained before going further. This is the dislodgment of air from the pipes, a collection of air at some unexpected point being one of the most prolific and annoying sources of trouble and vexation possible, owing to its so effectively impairing the circulation. And we must also deal with the means adopted to supply the apparatus with water, particularly to make good the loss by evaporation, or any that may be drawn away. When an apparatus is newly constructed, the boiler, pipes, and all appurtenances are, of course, filled with air previous to their being charged with water, and when the water is admitted, the air is driven to the highest point, where it will persistently stay, whether the pressure of water be high or low, and most effectually prevent the water circulating. We cannot, as some have supposed, by any means make the air quit its high position and descend, and so escape by the 48 Warming Buildings by Hot Water. supply pipe ; not even if we get the water to circulate can we get it to carry any accumulation of air, however small, down- wards, consequently a means has to be provided in the shape of a cock or small open pipe to allow of the free escape of collected air, not only when first charging, but afterwards, as the water is by the fluctuation of temperature continually absorbing and expelling air. In a simple apparatus, as Fig. 23, the water in the two pipes would be effectually prevented from having contact, as shown, if no air outlet was provided, but with a pipe or cock at a, the trouble is instantly overcome. Fig. 23. Of course it is easy to suppose that the fixing of the points for the air vents is a simple task, owing to the air finding the highest position due to its being so many times lighter than water. But this is not exactly the case, for in the ramification of an extensive system it is not at all an unusual thing for some point to be overlooked, and so cause trouble until remedied, and the remedy sometimes partakes of the nature of a problem, as will be learnt presently. If we get a horizontal flow pipe of any length (which fortunately is rarely required, as a rise, however little, can usually be got) ; the air will collect in great bubbles at irregular points along its whole length, whether this pipe be the highest one, or whether it is only one of a series, and in this case it would be desirable to have two or three air vents along the pipe when first charging, as the air globules do not move when the water circulates (they would if the pipe had a rise) ; but remain in Air in Pipes. 49 their positions most tenaciously, the water, when circulating, passing under, as Fig. 24. This can be ascertained only too quickly in any model or experimental apparatus. The most simple (but generally most expensive) and by far the best air vent is an open pipe. This may be in iron, copper, or composition tube ; in size it varies from Fig. 24. \ inch to f inch, but both these are extremes. As air can escape from an aperture with exceeding rapidity, it is not neces- sary to have a large tube, and accordingly | inch and J inch are the two sizes commonly used ; if the latter, it is the iron gas tube that is most usually employed ; but with the former, copper tube generally takes its place, as this can be readily bent, and the small quantity required makes but a small difference in cost. Composition tube (a soft metal tube commonly called "compo") is inexpensive, and readily bent to any desired angle ; but its softness is objectionable, as being so readily injured and disfigured by trifling mishaps, and as an air pipe is commonly a conspicuous object, its appearance must be considered. This is another reason for using copper tube, and a further reason why the pipe should be of limited size. Air tubes, especially when they have two or three bends in them, may sometimes be- come stopped by dust and debris, assisted by cobweb, and for this reason, although an J-inch pipe would give free vent to the air, it is not desirable to use it. To prevent a stoppage as much as possible, it is a good practice not to leave the pipe pointing upwards, but turned over either as Fig. 25 or Fig. 26, and to facilitate removal, when they require cleaning, a union should be used to connect this tube with the hot-water pipe. E Fig. 25. Fig. 26. Warming Buildings by Hot Water. Fig. 27. One very important feature connected with these tubes is that they must not on any account dip downwards, that is to say, like the flow pipe of a hot-water apparatus, they must either be vertical, or ascending to some degree a horizontal pipe being hardly tolerated, and an air pipe that descends in the least degree being utterly wrong. If we carry an air pipe downwards at any point, as at Fig. 27 for example, this pipe may be quite clear, and fulfil the duties of an air vent properly when first the apparatus is charged ; but after the appa- ratus has been in use a short time, water will collect at a, by condensation of vapour (and in time a collection of dirt par- ticles will also be found there), and this small quantity of water will effectually prevent the free exit of any air that may collect afterwards, as we have to remember that there is no pressure exerted to expel the air, unless the boiler be over fired and generate steam. It is practically the same effect as is obtained by putting a trap in a bath waste pipe, this trap holding a small quantity of water to prevent the exit of objectionable gases, which it does successfully a success which has objectionable qualities in the air pipe of a hot -water apparatus. No portion of an air pipe which contains water must be carried outside, or it will be seriously affected by frost. An air pipe cannot conveniently be used with an apparatus that extends through several floors of a building, owing to the great length some of the pipes would have to be,* and resort has then to be made to a tap or cock. * There has to be an air vent to every distinct service and to every coil, radiator, &c., so that in an extensive apparatus of this character twenty or thirty vents might be needed ; but so many as this are rarely needed in the low-lying horticultural class of work. Air in Pipes. An air cock is usually of a shape similar to Fig. 28 (full size), which has an internal construction very much like an ordinary tap, but the " way " or passage through it is only about \ or T 3 ^ inch in diameter, which, however, is ample for the purpose, as these are things that cannot get stopped up in any Fig. 28. Fig. 29. way like an air pipe. The screw portion is commonly made to fit into a hole which is drilled and tapped for J-inch gas thread (pipe). A more improved form of cock has been quite recently introduced, as Fig. 29 (full size). This form is a de- cided improvement, being less subject to leakage from wear and use, and less likely to stick tight ; and the makers claim that as the nozzle is situated at the side, there is less likelihood of damage being done when turned on, if it is in proximity to any wall or other decorations. When an air tap is opened (i. e. turned on), if there is any air, it escapes ; but we can never tell if the whole of the air has escaped until water issues, and if there is any pressure the water will be ejected to a considerable distance, oftentimes wetting the ceiling if an upright air cock is used, as Fig. 28. The other form of cock, Fig. 29, is supposed to overcome this, as the outlet is at the side ; but it must be submitted that if the ceiling escapes injury, the water may still be projected against a wall ; but with either form of cock this trouble can be overcome by holding a cloth, or some such substance, over the tap when discharging the air. E 2 5 2 Warming Buildings by Hot Water. There are two forms of automatic air vents to be had ; but although such appliances are much needed, the writer hesitates to recommend them, owing to the bare possibility of their failing at some time, early or late, which Fi g- 3- failure would be almost a calamity in some instances ; as should it for instance be in a radiator situated over a valuable ceiling, the leakage would in a few moments do some harm ; or in a grape house the possible flood of water might ruin the vines, which need a dry atmo- sphere, besides causing an instant fall in the temperature, which, if occurring in the night, would work endless mischief in any horticultural building. SUPPLY CISTERNS, ETC. It is, of course, necessary to pro- vide some means not only of filling a hot-water apparatus in the first place, but also of replenish- ing the waste of water that takes place from evapora- tion, and that which may be drawn off, if a means of drawing water off is provided. Between an apparatus that loses water by evaporation only and one that has water drawn from it as well,* some difference may exist in the provision for replenishing, and it will be best to speak of each separately, the latter arrangement being taken first. In this case a supply cistern has to be provided, this cistern being very commonly of cast iron, either plain or galvanised, and its size requires to be governed by the magni- tude of the apparatus in the following way : Water expands, i. e. increases in bulk, upon the applica- tion of heat, the expansion uniformly increasing as the tem- perature rises, so that a vessel exactly filled with cold water would, when heated, overflow ; therefore if a cistern of * The writer is still alluding to horticultural work, in which a deal of warm or tepid water is required for watering melon and cucumber pits, and for many other purposes. Water Supply. 53 insufficient size were provided, it would not be capable of holding the increased quantity or margin that has to be provided for when the water is heated. Water, when heated from freezing to boiling point expands one twenty-fourth that is to say, twenty-five gallons of boiling water equal in weight (and original capacity) twenty- four gallons of water at freezing point ; or in other words, water near freezing point occupying 24 inches space in a vessel, would, upon being heated to 212, be found to be occupying 25 inches. But in hot- water works we have no occasion to make provision to this extent, as the two extremes of heat named are not experienced, and the calculation need only be based upon a difference of about 130, that is from 50 to 1 80, which, according to the above result, would give us an increase in bulk of about one in thirty-six ; so that by using a cistern having a capacity of one- thirtieth of the whole contents, we shall allow room for expansion, and have a little room to spare, which is needed,* especially as the pipes, &c., are also affected by heat, and the slight increase in size that they undergo enables them to hold a little more water. It is a very desirable plan to fit these supply cisterns with an overflow pipe, this overflow being conducted to some non- objectionable point, and it is requisite when charging an apparatus not to fill the cistern more than an inch or two, otherwise an overflow will take place as the water heats. The ball valve (if one is used) requires to be fitted near the bottom. The quantity of water that is lost by evaporation only is very trifling, perhaps a quart per week (according to the size or heating properties of the apparatus), and if none is drawn off, a ball valve to automatically replenish the loss is not * See table at end giving capacities of pipes, &c. As an instance, 500 feet of 4-inch pipe and the boiler would contain about 280 gallons. This divided by 30 gives 9i gallons, which represents the least capacity the cistern should have, unless an overflow of water is unobjectionable, or unless the overflow pipe of the cistern is of good size and relied upon to take away the surplus water (see page 56). 54 Warming Buildings by Hot Water. necessary, and is sometimes fruitful of mischief, as these articles are ever ready to refuse to act when they have little work, and get stiff in the working parts. When water is drawn off for any purpose whatever, it is very desirable and necessary to have a ball valve or cock ; but care should be exercised to get one of a good quality, as a really perfect article of this description has not been made yet. The position in which the supply cistern should be fixed is governed to some extent by circumstances, but it is usually placed as near the boiler as possible, but there may be no objection to its being at the further extremity if desir- able. There is something of a controversy existing amongst workmen as to whether or not an advantage is gained by carrying the supply service into the boiler itself instead of into a pipe ; but there is no strong argument in favour of this, in fact there is a greater likelihood of the water in the cistern becoming hot by this means. The best arrangement by far, and which is adopted by all the leading specialists, is to connect the cold supply service into the return pipe, this service (cold supply) either dipping down below the return pipe before entering it, as Fig. 30, or having what is called a "siphon," in reality a double bend, as Fig. 31, to prevent the hot water circulating up it, as it would do readily if the pipe proceeded straight from one point to the other.* Some * In this we have illustrated a phenomenon peculiar to the earliest form of hot-water apparatus in which but one pipe is used. In this arrange- ment the pipes could never be allowed to dip down to the slightest extent under any circumstances without entailing a marked failure. Each pipe, whether there were many or only one, was a flow and return in itself. If vertical, the heated water ascended up the centre of the pipe, and the cold descended around close to the outer surface. If they were carried in a slanting direction, the hot water travelled along the upper half of the pipe, the cold travelling back beneath it. It is worth any one's while testing this with a glass tube apparatus as already referred to, as the action is very peculiar, showing again how very free from friction the water particles are which allow of contrary currents travelling alongside in contact with each other, yet absolutely free from the least trace of resistance. If this single pipe is carried horizontally or nearly so, the water does not circulate. To dip the pipe in the least degree is to keep it more still if possible. Water Supply. 55 prefer to adopt both measures, as Fig. 32, and as the extra cost is but trifling, it is much the best plan. The cistern need never be fixed higher than from 12 to 24 inches above the level of the highest point in the flow Fig- 3i- Fig. 32. pipe, so that the apparatus may quite fill. No more than this is required, as increasing the height of the position that the cistern occupies only adds to the strain upon the appa- ratus by the increased pressure of water. This will be more fully explained presently, when speaking of those forms of apparatus that are used for heating several floors of a building, and in which the question of pressure must have every con- sideration. The supply pipe (from the cistern to the return pipe) should be either f inch or I inch, the latter for pre- ference, as a great deal of sedimentary deposit occurs. It is an excellent plan to have a screw plug at the bottom point of the double bend, as dirt may accumulate here very quickly. It must be mentioned that when water is drawn off for various purposes a new and objectionable feature commonly ' presents itself, if the water be hard (by coming from chalk strata), in the fact that the boiler gets incrusted inter- nally with a coating of carbonate of lime, which, when of 56 Warming Buildings by Hot Water. sufficient thickness, will cause the boiler plate to become fractured. This takes place in a minute form with nearly every apparatus (unless rain-water be exclusively used, as is always recommended), but no appreciable deposit shows itself unless the water is often changed, as each quantity of water, when subjected to heat, deposits a certain quantity of lime, which, although small, quickly forms a thick coating on the boiler plate when fresh water is frequently entering the apparatus. This subject will also be treated fully presently under the heading of " Hot Water Supply " (for baths and household purposes). When no water is drawn from the apparatus a ball valve is not usually employed, owing to this article being apt to get out of order unless it has regular use, and it is not always that the rule as to the size of the cistern being governed by the capacity of the apparatus is adhered to ; as although the water expands when heated to the extent described, yet it only expands when first heated, and does not contract until the water is allowed to cool, which will be probably an interval of six months at least, so that in many cases a small cistern is put just for filling purposes. The water, when first heated up, is allowed to overflow (passing away through the overflow pipe) as much as it will, after which no trouble is experienced until it is next charged full with cold water, which certainly does not happen in the winter, and if a forcing house is in connection the fire is then kept going all the year round. For a simple apparatus consisting only of a few lines of pipe a very useful appliance is obtainable, which fulfils the purpose of a supply cistern and air vent combined, besides acting as a support and junction piece to the flow and return pipes. This article is as Fig. 33, which shows its application clearly. It is a very useful contrivance. Rain-water is most commonly used for charging the apparatus ; but although it is the best, as creating no incrusta- tion of lime deposit, however much the water may be drawn off, yet it is not always obtainable ; and when it is, it cannot Expansion of Pipes. 57 Fig- 33- Fig. 34- be got quite free from dirt, and through a little carelessness the circulation has often been stopped by leaves, &c. It is also noticeable that soft water has a much more vigorous action upon iron than hard, causing it to rust very rapidly. For these reasons it is very necessary to provide a means of emptying the apparatus by a pipe or tap fixed at a low point, so as to periodically flush out all sedimentary matter. This should be done regularly, and at least twice a year, otherwise the deposit quickly becomes suffi- ciently solid to prevent its being removed by a flush of water, and it will then become necessary to take the pipes apart to clear them. The writer once saw a long length of pipe more than half filled with deposit caked hard, as Fig. 34. This accumulated by about three years' negligence. The expansion brought about by an increase of temperature has been spoken of so far as it concerns the water that fills the apparatus, but we have also to consider its effect upon the iron pipes, &c., which contain the water, as these, and practically everything else in nature, are subject to this phenomenon. Although the increase is exceedingly minute in a single length of pipe, yet in long runs it amounts to sufficient to bring about a rupture somewhere, unless provision is made for the movement to take place freely and without strain. Taking the extreme temperature of water from 32 to 212 (for the heat of the pipes is, of course, governed by the temperature of the water), we get a difference in bulk (or, in this instance, we may say length, as the increase in diameter is not appreciable in this work) of I in 900, or, in other words, a 100 foot length of cold pipe would, upon being heated to 212, be increased in length by if inch not a great increase certainly, but sufficient to break some joints if no provision was made. In a long length of pipe it is not sufficient that the extremity farthest from the boiler be clear 58 Warming Buildings by Hot Water. to allow of this further projection, as the weight or pressure exerted by the pipes upon their supports brings sufficient friction into play to prevent their movement until a con- siderable force is exerted, which in the meantime breaks the joints or does some other damage. It is therefore necessary (with long lengths) to rest the pipes upon rollers placed upon the brick supports. These may be short lengths of round rod iron or tube, or to secure neatness and Fig. 35- stability an iron support with rollers can be obtained, as Fig. 35. This ensures free move- ment in expansion and contraction ; but this is not sufficient by itself, as in the first place the top (flow) and the bottom (return) pipes of a main or a branch service expand to different extents, as they are never at the same temperature, and it will be seen that very awkward results would ensue if this was not provided for. Then again, from a long main service there may proceed three "or more branch services, and it would not do for these services (which are most probably carried off at right angles to the main) to be carried to and fro as the main pipe ex- tended or contracted itself, this being likely to do a deal of mischief if the branches pass through a wall or were rigidly fixed in some such way. It therefore resolves itself into a necessity for provision to be made not only for the pipes to have freedom to move without binding on their supports, but this movement must be made local, so to speak, to various points in the apparatus by using expansive joints, which, as their name implies, admit of a slight movement confined to the joint itself; or with some of these joints we may consider they permit of a sort of telescopic movement, so as to prevent the extension continuing beyond the joint. More, however, will require to be said about these presently. It sometimes happens that in residence work the pipes have been secured rigidly to their supports, or to the wall by means of wedges or some such arrangement, or it has occa- Expansion of Pipes. 59 sionally been known for the further extremity of a service to terminate butt against a wall or partition ; in either of these cases very unhappy results must be, and always are, ex- perienced. In the latter instance the writer once saw a new greenhouse wall pushed right out by the expansive force. 60 Warming Buildings by Hot Water. CHAPTER IV. IRREGULAR FORMS OF APPARATUS. Dipping pipes below doorways and other obstacles Its effect upon the motive power and general efficiency Velocity and its effect Practical v. theoretical results Retrograde motion Calculations as to " dip- ping " pipes Other phenomena Theory as to results obtained im- mediately the heat is first applied to the boiler. IT has already been explained that it is no uncommon thing to have an apparatus which, from the highest point in the flow pipe to the point where the return enters the boiler, measures, perhaps, only 4 feet vertical, so that the circulation of a large body of water depends solely upon a difference in the weight of two short columns amounting to but I oz., without deducting any allowance whatever for friction or any other trifling obstruction that may present itself. In all horticultural works where but a small rise and fall in the pipes is practicable, an obstacle must never be more than a trifle, or the results will be partially or wholly bad. Now it not uncommonly happens that with a view to convenience, or from necessity, a pipe, the return pipe prob- ably, requires to be carried down below its normal course, usually when it has to pass a doorway, which it cannot do without being carried down to a level with or below the floor line as Fig. 36, and an instance might arise where a pipe has to be taken down below the level of the boiler itself. This in glass-house work is possible ; but it is not at the advantage an apparatus is that is carried up two or three floors of a build- ing, with, as a matter of course, a vastly increased motive power. The motive power of an apparatus can be increased by increasing the vertical length of the flow and return pipes Irregular Forms of Apparatus. 61 7 fx^v^^^^^^^ (with some limit), and also by increasing the length of hori- zontal pipe, so that the water may lose more heat and create a greater difference in temperature (and weight) between the water leaving and entering the boiler. This also must have some limit. In horticultural work it has been pointed out that the former of these two methods can never be resorted to with a view to increase the motive power, as every inch of vertical pipe that can pos- sibly be fitted is usually required to work an appa- ratus of an ordinary cha- racter in the usual way. For we have to remember that the house is usually placed upon the level of the ground (many gardeners prefer having the floor of the house below the ground level), the pipes cannot be put much above the floor level, and the boiler cannot be fitted far below, as a very deep boiler pit is objectionable and quite impracticable in many instances, where water is obtained 2 or 3 feet below the surface of the ground ; so that we may consider that an average height from the return pipe at boiler to the highest point of the flow pipe is about 5 feet, representing say 4 oz. as the motive power certainly a very weak power to permit of our carrying pipes in a way, or doing anything, contrary to what favours the circulation. The object in thus dwelling upon the insufficiency of the motive power that is obtained in this particular branch of hot- water works is to make it clear that precautions should always be taken to avoid peculiarities in the construction of the appa- ratus, particularly that of carrying pipes in a direction opposite to what is favourable to its success, viz. a continually ascend- ing flow pipe, and a continually descending return pipe. For the disadvantages of a low motive power are in reality two-fold, namely, the want of the power itself to increase 62 Warming Buildings by Hot Water. the circulation and the loss in velocity of circulation, which is clearly a drawback when obstacles have to be overcome, for it takes much less to further retard or overcome the motion of a sluggishly moving body (whether solid or liquid) than it does to interfere with anything travelling rapidly, that is to say, with a moderate impetus. Before proceeding to discuss the possibility of " dipping " pipes in their course, it is desirable perhaps to just explain the question of velocity of circulation, as tending to make matters still more easily understood, although really no reliance can be placed on the results arrived at, as though strictly correct in theory, they are so modified and varied in practice, particularly by friction,* quantity and size of pipe, &c., &c. Hood grasped the subject of velocity very strongly, as is evident by his treatment of it, as follows : " The velocity with which the water circulates in this kind of apparatus can be calculated theoretically when certain data are agreed upon or are ascertained to exist This * The writer is always in doubt as to whether the term " friction " is correctly applied here. When we speak of this phenomenon we suppose that it exists between two substances more or less rough (for the finest polished surface shows a roughness under a powerful microscopic glass), this rough- ness offering a resistance which prevents one of the bodies readily slipping from the other when their surfaces are tilted more or less out of level. But there are no substances so rough on the surface that they do not readily part company if they are forcibly moved or tilted right over. This is not the case with water, for if we take a finely polished surface and pour water on it, it runs off as fast as poured on, with the exception of some of the liquid that lies close to the surface referred to, and this, however it may be tilted, still adheres, even if the object is turned upside down. Consequently there must be an attractive or adhesive force the former, most likely, as we cannot suppose it is a single layer of water particles that remains fastened, so to speak, on the surface, but very many layers as the particles of water are so exceedingly minute. This property is manifested almost the same whether the surface be very rough or very smooth. It is therefore just possible that the particles of water next the inner surface of the pipe are quite still, although the particles of water next them may be in motion, in the same way that in watching the circulatory movement of water heated in a glass jar, we find the top surface or " skin " of the water is perfectly still, as already explained. Irregular Forms of Apparatus. 63 velocity is easily calculated ; a gravitating body falls 1 6 feet in the first second of time of the descent, 64 feet in two seconds, and so on, the velocity increasing as the square <3f the time To estimate the velocity of motion of the water in a hot- water apparatus, the same rule will apply. If the average temperature be 170, the difference between the temperature of the ascending and the descending columns 8, and the height 10 feet, when similar weights of water are placed in the two columns of an inverted siphon, the hottest will stand '331 of an inch higher than the other, and this will give a velocity equal to 79*2 feet per minute. If the height be 5 feet, the difference in temperature remaining as before, the velocity will be only 55*2 feet per minute, but if the differ- ence in temperature in this last example had been double the amount stated that is, had the difference of temperature been 1 6, and the vertical height of the columns 5 feet, then the velocity of motion would have been 79 2 feet per minute, the same as in the first example, where the vertical height was 10 feet, and the difference in temperature 8. This therefore proves, in corroboration of what has been already stated, that reducing the temperature of the water (that returns into the boiler), either by using smaller pipes (which part with the heat faster), or by increasing the length through which it flows (so that there may be more heat radiated), has the same effect on the circulation as increasing the vertical height? leaving out the question of friction. " The velocity for 3 feet of vertical height by the same rule will be 43*2 feet per minute, for 2 feet of vertical height 36 feet per minute, and for 18 inches of vertical height it will be 30*7 feet per minute, if the difference between the two columns be in each case 8 the same as in the former examples. It must be here observed, however, that, although it appears by these calculations that increasing the vertical height of the pipe fourfold will produce a double velocity of circulation, as the water will then pass through the pipe in half the time, the difference between the temperature of the flow-pipe and of the return-pipe will be* lessened, so that the 64 Warming Buildings by Hot Water. quadruple increase of height will only produce a rate of circu- lation about one and a half times the original velocity." As Hood remarks, such is the result in theory (as regards the sums and figures stated). In practice we shall never meet with an instance agreeing with these results, even in an apparatus small in size and constructed upon the most favourable principles. To get at the true velocity a large amount must be deducted from these theoretical figures, as the data given are arrived at upon the calculation that the sub- stance is falling through air. Now air offers no resistance comparable to water passing through pipes, particularly those that are horizontal, the water in which is helpless to assist in its own movement ; then every angle offers additional resistance, not merely a resistance of friction, but a tendency to obstruct the whole mass bodily. With an ascending or descending pipe we more nearly approach the theoretical velocity, but in these pipes we only get a true velocity near the centre, the particles nearest the surface being very sluggish in movement. Hood explains that the motions in a vertical flow pipe and a vertical return pipe differ in character by reason of the outer particles not clinging to the pipe surface in the latter pipe as they do in the former, but that the water in the return pipe moves bodily, so to speak, instead of the centre particles moving faster than the particles near the surface, as they do in the flow pipe, as just explained. The writer has, it must be feared, to contradict this, as in numberless experi- ments with glass pipes this phenomenon has never been detected. It is obvious from Hood's explanation that the deduction has been arrived at by considering the water in the return pipe to be cold, which of course only happens wnen the fire is first started, as this is afterwards rarely allowed to go out (unless it is a small amateur apparatus). Now in dealing with an apparatus in which we wish to dip one or both pipes below their normal course, that is, to make the pipe descend to pass some obstacle and then rise up to its original level, we have to remember first, that we introduce Irregular Forms of Apparatus. 65 an obstacle to the natural course of the circulation, and, secondly, that in horticultural work the circulation at its best is hardly anything better than feeble. The cause of a dip proving a check to the circulation is as follows : We may suppose an apparatus constructed as at Fig. 37, exceedingly simple, as it is merely a pipe proceeding all Fig. 37- round a greenhouse,* but in carrying the pipe along all four sides of the house we encounter a doorway under which the pipe must be carried at the floor-level as shown. Now from the top of the boiler to the point E everything is normal (as in fact it is to the point G) ; but in the vertical pipe E to F we have a descending column of water lighter than the ascending one in the pipe G to H, as according to the principles laid down the water gets colder and heavier as it gets nearer (in its return) to the boiler, due to loss of heat by radiation. The fact of the water in the pipe G, H being heavier than that in the pipe E, F naturally tends towards a back or retro- grade movement, as it is now clearly understood that it is the fact of the water in one pipe being of greater weight than that in the other (of the ordinary circulating services) that brings about the movement which is termed the circulation, by the * Let it be clearly understood that this is not the usual way of arrang- ing the pipe or pipes. They are usually carried up and down two or three sides of the house so as to avoid the doorway, as will be explained later ; the above arrangement is merely adopted for the purpose of illustrating the " dipped " pipe. F 66 Warming Buildings by Hot Water. heavier forcing the lighter bulk before it, and not the heavier giving way, retreating before the lighter, as we require it to do in this instance. In the simple dipping of a pipe under a doorway there is no very marked difference in the temperature of the descend- ing and ascending pipes referred to, as they are so near together, although there is quite sufficient difference to bring about a movement in the wrong direction if the general motive power of the apparatus did not exist. If a distance of say 20 or 30 feet separated the two points F and G, a greater obstacle would present itself, as the greater the distance between these two points the greater must be the difference in the temperature, and consequently the weight of the water in the two pipes indicated. It may be accepted as a rule that the greater the space referred to, the greater the resistance offered in the circulation. Now the motive power of the apparatus must be sufficient to overcome this inclination to return movement, and it must be sufficient also to have a surplus of power to produce the general circulation required. This residue of power should be sufficient, as a feeble movement will not only fail in con- veying heated water to the extremity of the apparatus by reason of its slowness permitting the heat to radiate before it can get to its destination, but it will readily fail if an obstacle get in the pipe ; a leaf (so frequently found in the pipes) or a collection of refuse would totally stop the circulation. This requires consideration, as in most country places, pond, ditch, or surface water is used to charge the apparatus. To show a simple way of calculating if the dip in the last illustration is permissible, we can take another figure, Fig. 38, and by spacing it out in imaginary degrees of temperature as shown, tolerably correct results can be arrived at by comparing the mean temperature in the ascending and descending volumes of water. From A to B we have 179 mean, and from J to K we have 141 mean, a difference of 38, and to this we can add, say, one degree for the portion of vertical return pipe at C, D, making 39 to produce the circulation if Irregular Forms of Apparatus. 67 the dip was absent. If we take the mean temperatures of the two vertical columns of this dip we find there is a difference of 7, this being 7 of resistance to the circulation, and which has to be deducted from the 38 last mentioned. This, it will be seen, however, leaves ample margin of motive power in this Fig. 38- n i :\ 5)* _J. 1*2 1*3 . 140 '45' K [[ 153 IS4 155 156 157 158 ISO ^ 14.6 14-7 140 149 case ; but, as already pointed out, if we increase the space between G and F, or increase the depth of the dip, further resistance is offered.* In Figs. 37 and 38 just explained, the dips are shown in that portion of the pipe that is returning to the boiler, whereas in Fig. 37 the flow pipe might have been carried towards the doorway, where the dip has to be, first ; in this case no more nor less resistance would have been offered by the dip itself, supposing its dimensions to be the same in each case, but when first starting the circulation the obstacle (for the dip is an obstacle) would be encountered before the circulation gained the impetus it would do if the dip was situated as Fig. 38. We must give every consideration to what happens when the circulation is first started, as any ill effect that is to be experienced will give the greatest trouble at this time. In Hood's description of this he shows the dip in the flow pipe as Fig. 39, his explaination dealing only with the resistance offered by the dip irrespective of its situation as follows : " In an apparatus constructed thus, the motion through the boiler and pipe A, B, and through the descending pipe C, D, takes place according to the principles described. But it is * It must be explained that in these calculations again, the results are but theoretical, as the temperature of the air, the size of the pipes, and the position of pipes, all tend to vary the general effect. F 2 68 Warming Buildings by Hot Water. evident that, on motion commencing in the return pipe y y z, in consequence of the greater pressure of C, D than of A, B, the water from A will be forced towards , at the same time that the water in , /, g, h flows to- wards C. But when a very small quantity of hot water has passed from the pipe and boiler A, B, into the pipe *?,/, the column of water g, h will be heavier than the column e, f, and therefore there will be a tendency for motion to take place along the upper pipe towards the boiler instead of from it. This force, whatever be its amount, must be in opposition to that which occurs in the lower or return pipe, in consequence of the pressure of C, D being greater than A, B ; and unless, therefore, the force of motion in the descending pipe C, D be sufficient to over- come this tendency to a retrograde motion, and leave a residual force sufficient to produce direct motion, no circulation of the water can take place." Now if we can dispose of the ascend- ing pipe G, H (Fig. 37), and continue the return pipe straight from G to K, the circulation becomes normal, which is of course the best course to aim at if possible, but this is governed chiefly by the distance from G to K, as it is not desirable to carry this pipe below the floor-level and probably lose its heat, unless it is a matter of a few feet only. In all the illustrations referred to, the dip has not been shown as extending below the point where the return pipe enters the boiler, in fact, its depth would not need to exceed 24 inches at the utmost ; but, paradoxical as it may seem, it is quite possible to extend the dip below the bottom of the boiler without creating any greater obstacle or resistance to the circulation than with the dips already explained. Supposing a deep dip to be required at some point near the boiler (in which case the pipe would not be required to ascend to its original level again), the pipe could be arranged Irregular Forms of Apparatus. 69 as Fig. 40, in which, by spacing out in imaginary degrees of temperature, we get a mean of 179 in the ascending pipes A, B, and a mean of 149 in the descending pipe E to *, the difference being 30 in favour of the circulation without Fig. 40. 74 173 172 171 170 169 iCa 167 tS 165 164 163 C ,162 50 151 152 153 154 155 156 157 ISfl I5S 160 143 143 144 14-5 the dip ; the resistance offered by the dip is 6, leaving a suffi- cient margin for effective work, to which may be added the effect of the small piece of descending pipe C to D. In this instance it will be seen that the apparatus is normal from the top of the boiler at A to the point in the descending pipe marked,* which is opposite the point where the return enters the boiler. It is almost the same (so far as the resistance offered by the dip is concerned) as placing the Fig. 41. dip as Fig. 41, therefore if this dip is of the same dimensions as the one described in Figs. 37 and 38 it will only offer the resistance to the circulation that these latter would do, even though in one case the dip extends below the bottom of the boiler and in the other the dip does not reach this point. In this case, as in the others, the resistance is increased by in- creasing the space between F and G, and also, of course, by increasing the depth of the dip. 70 Warming Buildings by Hot Water. In describing the results obtained from an ill-formed apparatus, Hood points out that occasionally an apparatus can be met with which, although apparently constructed on the worst principles, has, in consequence of various circum- stances, been favourable in results ; and he goes on to describe an apparatus constructed as Fig. 42, where the pipes were not more than 3 inches apart, "yet the water circulated with freedom, but in this case not only was the pipe of con- siderable length, and without any angles or turns, but the size of the pipe was only 2 inches diameter, so that the pipes cooled twice as fast as they would have done had pipes of 4 inches diameter been used " (see pp. 243, 298, &c.). It can hardly be supposed (although the intention seems very clear) that Hood intended this last-described apparatus to be an instance of "construction on the very worst principles/' as there are hundreds if not thousands of small apparatuses carried out in precisely this manner. Pro- viding all other points in the apparatus are correct, the distance between the two pipes is sufficient to ensure success, if the apparatus is small in size. There is a very common practice (which, however, cannot be recommended for reasons to be presently stated) of heating a small greenhouse or conservatory from a kitchen range boiler. If the floor of the greenhouse is on a level with the kitchen floor, or a little below it, as is often the case, the pipes will most usually be found taken from the side of the boiler, which will not always permit of their being more than 3 inches apart, yet so far as the circulation is concerned all goes well, so much so that a complaint is rarely heard of its working badly. If an apparatus was constructed as Fig. 43, with the pipes as exactly level as possible to get them, a free circulation would be found to set up in the pipes and without any hesi- tation at the start, although it cannot be relied upon to circulate in the same direction every time it is started afresh, Irregular Forms of Apparatus. 71 as, in a series of experiments made with this apparatus, it was found sometimes that what hitherto answered as the flow pipe acted as a return, and vice versa, although there seemed to be a preference for one pipe to act as an established flow pipe and the other as a return. If we carefully investigate the question of how the circu- lation first starts or sets up, we shall see that it is quite Fig. 43- natural for it to act and traverse the pipes (circulate) that are connected on a level with each other as just described. Whether inquiring upon a theoretical basis or from results obtained from practical experiments, we shall find that in- stead of the water failing to circulate (when the apparatus is constructed contrary to accepted notions) the difficulty will be to get the water to remain still an apparatus has to be erected in an extraordinary manner to wholly prevent the water moving in the pipes. Returning to the apparatus with the pipes starting level (Fig. 43), in accounting for the results we must consider what happens when heat is first applied, the water in all parts of the apparatus being stationary up to this moment. Move- ment may be considered to first take place in the water nearest to the source of heat, which we will suppose is at the bottom. Almost at the very instant the particles are noticed to move there they will be found moving in the other parts of the boiler also, for the movement everywhere is almost simultaneous, as it can be so readily seen that the movement of water at the bottom of the boiler is due to and dependent upon the pressure and consequent movement of the water at the top. Now the instant the water in the boiler becomes warmed Warming Buildings by Hot Water. and rarefied and is in movement, we should have the pheno- menon of hot water being in the boiler and cold water in the pipes extending from the top of the boiler. In other words, we may rightly consider the pipes as an extension of the boiler itself, in which case we should have hot water in the general body of the boiler, while a portion of the upper part is tenanted by cold water, and this, it is needless to add, is against all principles, and cannot exist unless the portion of cold water referred to was confined in some way, and even then it would set up a circulation of its own, if the hot water imparted heat to it. We thus see that the cold and heavier water cannot remain in these pipes at or near the top of the boiler if they have free communication with the heated water which is practically beneath them, but it is equally obvious that the cold water cannot come down both pipes at the same time : one must act as a flow pipe and the other as a return, and this they readily do. The only inference to be arrived at for their so acting is that they may not be perfectly level, or some inequality or trifling obstruction in one pipe permits the other to take the lead. We have practically the same result when we connect vertical pipes both on top of a boiler (without continuing one of them down inside), as Fig. 44, only that the explanation just given bears even a stronger application in this case, as the water within the pipes is truly on top of the water in the boiler, and it certainly will not remain there when the latter becomes heated ever so little, and a circulation will be found to set up directly heat is applied to the boiler. It is a common impression, particularly amongst work- men, that this last arrangement described would fail to act by the water remaining stationary in the pipes, although the water would become of a high tem- perature in the boiler, but this is incorrect, for the water will never fail to circulate up one pipe or the other. It is most peculiar to note that when the pipes start level, no reliance Fig. 44- Irregular Forms of Apparatus. 73 can be placed as to which pipe will act as a flow and which as the return. Sometimes the water will proceed up one pipe when the apparatus is first started, and when the circulation is once established it will continue acting in the same way. If it is allowed to cool down again and the water to become stationary, then it is just possible the water will flow up the other pipe when started again. This will be more fully in- vestigated in a later chapter, when treating of branch services. It must not be supposed for one moment that in dealing with the circulation that takes place when pipes are started from level points, it is intended to recommend this method. The question has been dealt with to dispose of or put upon a more sound basis one of the little problems that are always presenting themselves in this work. The customary plan of having the flow pipe from 9 to 30 inches above the return pipe, that is, the flow pipe at the extreme highest point in the boiler and the return at as low a point as possible, is decidedly the best arrangement. It is reliable, for the water will always circulate one way, and it in every way aids the natural effect. Hood has set it down that 12 inches should be the recognised minimum distance between the two pipes : this is a safe and practical suggestion. It is somewhat unusual if this space cannot be had, as boilers made for heating purposes are seldom less than, say, 15 inches high. The illustrations, Figs. 23, &c., show the correct points for the two pipes, but of course the return can come in at either or both sides, and it is not absolutely necessary by any means for the flow or return to be situated centrally from front to back, as will be seen in the various illustrations of boilers on later pages. 74 Warming Buildings by Hot Water. CHAPTER V. IRREGULAR FORMS OF APPARATUS continued. Other and more irregular forms of apparatus Methods of calculating the resistance experienced A phenomenon opposed to a theoretical basis Method of assisting the circulation in an irregular form of apparatus Hood's suggestion to this end and its advantages and disadvantages Another and practical method of effecting a good circulation below the boiler level The tank system Further informa- tion as to expelling air. A WELL-KNOWN and talented author upon " Heat " * clearly explains (theoretically) to what extent a pipe may be dipped, as shown in Figs. 45 and 46. In the first figure we have an apparatus which would undoubtedly extend up one or two floors of a building (thus differing from the horticultural form of apparatus, which has been almost exclusively treated up to this point), its construction being normal, and showing a mean temperature of 160 in the ascending column and 117 in the descending column, a difference of 43 degrees to fur- nish the motive power, which, it is needless to add, would create a very rapid circulation in an apparatus wholly of vertical pipe. In Fig. 46 the mean temperature in the ascending column is about 135, and in the descending column 135 also, so that theoretically there should be no circulation at all ; or, if we vary it a little by placing the boiler a little lower than shown in Fig. 46, as at Fig. 47 for instance, the mean temperatures in ascending and descending columns would be, say, 134 and 128 respectively, a difference of 6, which would produce a less rapid circulation. But according to the principles laid down this would be sufficient to do moderately effective work in a vertical apparatus, and shows * Box upon ' Heat ' ; London : E. and F. N. Spon. Irregular Forms of Apparatus. 75 conclusively that the higher we carry the ascending column the greater the motive power obtained, and consequently permitting of the return pipe being carried to a greater distance below the boiler than when the ascending column is of limited height, as we get it in horticultural works. Now, as before mentioned, this is strictly correct in theory, but if any one erects a model apparatus as at Fig. 48, in which the pipe descends below the boiler, say three times as Fig. 45- 140 Fig. 46. Fig. 48. 130 170- 105- 135 95 much as it rises above it, upon heat being applied to the boiler a circulation will almost immediately set in that is to say, as soon after the application of heat as in an apparatus of normal construction, and the circulation will be in the correct direction, viz. ascending up the short pipe at the top of the boiler and returning by the pipe that enters the boiler near the bottom. Although we may only make this experiment in a small model apparatus, yet the results in this case may be quite 76 Warming Buildings by Hot Water. relied upon as being natural, although a little thought will show that it is opposed to all accepted principles.* It is easy to account for the circulation or movement that first occurs in this case, as we may consider the whole of the apparatus above the two points marked * to be of a normal character, and the part below these points simply consists of an inverted siphon with an equal weight of water (while cold) in each leg, so that when heat is applied to the boiler we must, as a matter of course, quickly have the water in the column A, B lighter than in the column C, D, which will be sufficient to produce a movement in the direction of B to C, for while the water in the pipes below the points * remains cold (that is to say, not yet affected by the heat) it will have no effect whatever upon the circulation, no more than to move in whichever direction the difference in pressure in the pipes above may cause it. This may account for a circu- lation setting in when the heat is first applied, and up to the time that the heated water has travelled round to D, but when in the course of circulation the heated water reaches the point E or F (but not yet past F) then we shall have the column B to F heavier than C to E, yet the circulation continues (but more sluggishly) in the direction in which it started, and does not cease to do so so long as heat is applied to the boiler. This experiment, although demonstrating a peculiarity in hot-water circulation as regards the principles and theories we recognise at present, is not valuable, as although the circula- tion remains constant it is of so low a speed as to be useless for large works. But supposing such an apparatus was needed, then its efficiency could be rendered secure by apply- ing heat to it at F, or at a low point in the pipe between F and G not an additional boiler, but by passing a piece of the pipe through a small fire (which, however, would require to be kept alight all the time the apparatus was at work), or * As this book goes to press there is an apparatus exhibited at the Crystal Palace which has the flow pipe carried from the side of the boiler, descending to heat some coils below it, and then returning into the bottom of the boiler, no part of the pipe services being as high as the top of the boiler. Irregular Forms of Apparatus. 77 Fig. 49. by applying a moderate sized " Bunsen " gas burner, which would be, perhaps, easier of application and certainly very regular in results. This, it must be quite understood, is sup- posing that the boiler cannot anyhow be placed at the lowest point, as it should be if possible. Hood describes a method whereby the introduction of some extra pipe or radiating surface, which he shows in the form of a coil, is the medium by which he can carry the pipes before the boiler to a greater extent than can be done if this coil was absent, and without impairing the circulation. His description is as follows : " In an arrangement of pipes, such as Fig. 49, the circulation will depend en- tirely upon the quantity of heat given off by the coil c, for it is evident that when the boiler B and pipe a are heated, the direct motion will arise in consequence of the greater weight of the water in the coil c and pipe d above that which is in the boiler and pipe B a. But as the water in the pipe e y below the dotted line, will be lighter than that in the pipe /, the ten- dency in that part of the apparatus will be towards a retro- grade motion. " The result of these two forces will be that if the water in the whole length of pipe w x is heavier than that of the whole length y z, in a sufficient degree to overcome the increased friction, circulation of the water will take place, and the velocity of motion will depend upon the amount of this difference in weight." Nothing could be more sound than the principle here laid down viz. that by putting a coil at the point shown we are able to dissipate more heat and make the water heavier by the time it exerts its influence in the descending pipe, and by Warming Buildings by Hot Water. this means it is rendered of greater power in overcoming the obstacle of the ascending pipe f, which is understood to be full of the heaviest water. But we could obtain the same result without the coil if we subject the pipe at the point w to some cooling influence, such as passing it through a small tank of cold water or exposing just this point to the outer air. This brings most forcibly to notice that in the majority of cases the mere fact of cooling the pipe here is, of all things, what should be avoided, as we may suppose that the object in carrying the pipe down below the boiler is for the purpose of providing heat (by a coil or series of pipes) at some point between x and z, in which case the object would be completely frustrated by the cooling influence at w. Therefore, although the principle is sound, it is not practicable, as a dip of such depth would never be necessary unless for some useful heating purpose, and then very little heat would be obtained. Supposing such a dip was required, but not for any heating purpose, then the coil would be permissible, but perhaps it Fig. 50. would be more useful to extend the pipe at the point w (as Fig 50), and so make some good use of it instead of coiling it up, as the result would be practically the same. Hood also describes another method having the same principle and effect and the same drawback as the last, but Irregular Forms of Apparatus. 79 instead of using a coil as the medium for cooling the water and rendering it heavier, he shows an apparatus, as Fig. 5 1, in which the flow pipe is carried by the nearest and most direct route to an open feed cistern or tank, and from there it is carried to wherever the heat is needed. He indicates a preference for this, owing to the absence of the friction which a coil would entail, and which is somewhat considerable. Fig- Si- 3 L It will be plainly seen that if this cistern is going to be used as a means of cooling the water somewhat, that its use will be prejudicial to the object for which the apparatus is intended, and on this account it could not be recommended ; but if the cistern is kept with a cover upon it, and in a fairly warm position, this method has some points in its favour, and it is not at all uncommon to meet with an apparatus so constructed and doing good service. In the first place it is understood that the cistern acts as a supply or filling cistern, and it possesses the advantages of allowing the freest possible escape of air and also of steam should the boiler become overheated. It prevents in a great measure, and in some instances entirely, the passage of air into the return pipe or pipes, and it will be readily seen that air, however small the quantity, must take up some space, and consequently will render the contents of the pipe or pipes 8o Warming Buildings by Hot Water. lighter than if air was absent, so that the whole of the space would be occupied by water. When this arrangement is adopted it can be made to bring about a saving in stop valves or cocks, as, supposing it can be conveniently carried out, there is one flow pipe of a sufficient size from the boiler to the tank, but from the tank there may proceed two or even three or four return pipes to the boiler, the number being governed by the different directions in which the pipe requires to be taken ; then whenever one or more of these services require to be stopped, it is only necessary to insert a wooden plug into the pipe where it appears inside the tank, and this plug will of course prevent all flow of water through the pipe in question. One of the chief reasons, however, for the adoption of a tank (into which the water is circulated) is, that by fixing the tank in a high position, as near the roof of the glasshouse as possible, we get a higher motive power, and by this means we can with greater facility circulate below the level of the boiler, as (see ante) it has already been explained that one of the means of increasing the motive power is to increase the vertical height, and the greater the vertical height the greater the extent to which we can dip below the boiler. An instance where this arrangement becomes desirable is when we have two or more greenhouses to be heated from one boiler, these houses being upon irregular ground, so that they stand at different levels, and it is found impossible to have the boiler at a lower level than shown. In this case it becomes possible that one set of pipes has to be carried a little below the boiler as Fig. 52, and in this case a tank becomes a necessity, as we should get poor results by running a pipe directly from the top of the boiler down to a point below its level, then up again on its return. The illustration shows the tank fixed, this tank, however, being closed and having a steam or air pipe from it ; this certainly does away with the convenience of plugging the pipes, but it is the best arrangement to save the heat and prevent a too lavish distribution of vapour. It must not be overlooked that in all these unusual forms Irregular Forms of Apparatus. 81 of apparatus air cocks or pipes play a more important part than ever, and in practice it will be found that a good deal of judgment is required to successfully rid the pipes of air in a thorough manner, a very necessary requirement, as it will be G 82 Warming Buildings by Hot Water. understood that in departing from the normal arrangement we must in a greater or less degree impair and lessen the motive power, and but a trifling accumulation of air under these circumstances may ruin the efficiency altogether. In Fig. 36 an air vent would have to be placed at the highest point of that portion of the pipe on the right-hand side of the door, and also at the highest point of the pipe on the left side, as a dip like this is a certain obstacle to the passage of air either way, whether it be the flow pipe or the return. It may be pointed out that in this arrangement the depth of the dip can be reduced by using a special form of pipe that is made to pass under doorways, this pipe having a flat even top, so that it need not be covered with earth or the paving material, but be fixed level with the floor line. In Fig. 37 we may suppose the pipe ascends slightly all the way from A to C, this latter letter being at the highest point, where an air vent would be required. From this point C the pipe decends to F, and no further outlet would be required thus far, but at H (which we may suppose is a trifle higher than J) another vent would be needed, as any air collected in this short piece of horizontal pipe would not be able to escape either way, it descending at both ends, neither could this pipe (J to H) properly fill when first charging, unless an air vent be there. In Fig. 38 an air vent would be needed at C, and one also at H (supposing H to be a trifle higher than J) in exactly the same way as the last described. In Fig. 39 we have practically the same apparatus again, although the dip is situated differently ; at e an air vent would be needed, as we may suppose this point is a trifle higher than A, and again at C would provision have to be made for air exit ; at no other point in the apparatus would it be needed, provided the apparatus is erected in the usual way, which would make C the highest point In Fig. 40, again, the point C should have its air vent, and this in a small apparatus would be sufficient, but if where the return enters the boiler there is ever so short a length of pipe, Irregular Forms of Apparatus. 83 it would be a most desirable plan to put an air vent in it at its highest point of course. In a short length of pipe it might be fixed in a manner that would be considered perfectly hori- zontal, and a difficulty would be experienced in deciding where to put the air vent, but this can be settled by using a spirit-level. It will be noticed that nothing could give us better results, as the chief feature in this article is a pipe having water with a globule of air imprisoned within it, the direction which the air takes in the spirit-level being exactly the direction the air will take in the hot-water pipe, supposing the level to be resting evenly upon the pipe in question. In Fig. 41, again, C is the necessary point for an air vent, and also H if we suppose H to be a trifle higher than the point where the pipe enters the boiler. The two pieces of horizontal pipe on the opposite side of the dip to H do .not require any provision for air exit, as these should both ascend towards the point C, i. e. descend toward the boiler. In Figs. 42 and 43 an air vent would be needed at the termination of the pipes furthest from the boiler (as shown in Fig. 43), but if an apparatus was constructed in this manner the boiler itself would also require an air vent of some sort at the top, as will be seen. In Fig. 5 1 we touch upon debatable ground when suggest- ing a position for the air vents. One of course would need to be at the tank, unless it has an open top or loose lid, but in the circulating pipe it depends entirely upon how this is run, as there are in this system as many advocates for making the upper pipe descend towards the end, the under pipe being carried horizontally as Fig. 53, as there are advocates for making these two pipes ascend towards the end in the usual way as Fig. 54. In the former case an air vent should be provided where shown, to prevent a possible air-lock when re-charging, and to aid when first charging ; and in the latter case the air vent would require to be placed at the accustomed extremity as shown. There is every argument in favour of carrying the pipes, G 2 84 Warming Buildings by Hot Water. under this particular tank system, in the manner shown at Fig- 53, thus treating the pipe from the tank to the boiler wholly as a " return " ; it allows of the freest possible escape of air, and brings about more natural results. Fig. 53- Fig- 54- In Fig. 52 is introduced two most distinct systems, but which will work in complete harmony (with a little care), and the results obtained by both arrangements should be satis- factory in every way. The whole of the apparatus on the right- hand side of the point marked A is of the most simple descrip- tion, and an air vent at the extremity as shown will suffice for this portion. An air vent is needed in the tank unless it has an open top or loose cover. This is regulated by the use to which the house is put ; as an instance, we may say that an open top would not do in a grape house, where an excess of moisture is usually objectionable. In the pipes on the left side of A, an air pipe can be fixed as shown if these pipes rise towards that extremity ; but as just described, it is better to arrange them as Fig. 53, in which case an air pipe should Irregular Forms of Apparatus. 85 be fixed at B, which however might not be so much needed at first charging, but we have in this case to bear in mind that unless special provision is made, the lower pipe on this side will not be emptied when the apparatus is discharged for any purpose, and this would cause a trap to be formed for air when recharging. The tank in this system should be from 10 to 25 gallons capacity, according to the magnitude of the job, but the water supply must not be arranged for the tank to fill more than about a third or half full, as already explained under water supply. The upper termination of the flow pipe need not stand up more than 3 inches inside the tank, and the pipes A to C, and E to G need not be more than 2 inches, unless they are all within the house and diffuse a useful amount of heat as the other pipes do. If any part of the pipes just named are carried out in cold situations (under- ground or outside the house) it is very necessary indeed to cover them in some way with a poor conducting material, to prevent loss of heat, as will be explained fully. It would be very necessary in this apparatus to provide throttle valves to each set of pipes, as it may be taken for granted that the portion of the apparatus on the right of A will have the freest circulation, and will take the ."lead" as it is termed, and it will be found that if the circulation starts in one direction more strongly than another it will continue so, and the part of the apparatus that is working the least effectively will fail to pick up and recover itself, in fact it may seem to get worse. This, however, is exceedingly easy of remedy by the use of valves, the gardener regulating them as necessary or accora- ing to his desire. Even in an apparatus constructed upon simple principles, if it has two or three distinct branches, the gardener usually finds some regulation necessary, and, strange to say, the regulation varies considerably in the same apparatus, one branch working freely at one time and sluggishly at another. The water supply (still referring to Fig. 52) is arranged for by the erection of a small filling cistern at the side, this, how- ever, is not so necessary if the tank can be permitted to have 86 Warming Buildings by Hot Water. a loose cover or open top. The filling is done by hand from a can, or by a ball valve if a regular service of water is accessible. In rilling by hand we have an objection in the fact of the tank being situated up out of reach, and it is not easy to tell when the supply wants replenishing unless an indicator is fitted. The usual indicator is a float inside the tank, a pulley on the top of the tank, at the edge, and a piece of wood to drop down outside ; this piece of wood being connected with the float by a light chain or cord which passes over the pulley as Fig- 55- It will be noticed that there is a deep dip in the pipe that connects the small cistern with the tank, the object of this dip being to prevent the contents of the small cistern becoming hot, which would be of no advantage whatever. It has been explained that water (when warmed) will circulate with con- siderable freedom in a single pipe from a boiler, and in the in- stance just referred to, we may consider the tank as acting the part of a boiler, and a circulation would set in, we may say immediately, between the tank and the small cistern if the con- necting pipe was straight, i. e. not dipped. The circulation would certainly be sluggish, but nevertheless sufficient to make the water in the small cistern hot, which would be an objection that the small cistern is provided expressly to obviate. The feeble circulation that sets up in a single horizonal pipe is immediately checked when the pipe commences to descend. This dip should be about 10 inches deep ; a small plug could be fitted in the lowest point of this " siphon " (as it is wrongly (called if any liability of stoppage by dirt, &c., exists. 87 CHAPTER VI. CAUSES AFFECTING CIRCULATION OF WATER IN APPARATUS. Friction Table of relative degrees of friction in different sized pipes Different purposes for different sized pipes Limit to circulation As to limiting the lengthiof services Obstructions and faults Erratic results and their causes The effect of air in circulating pipes Reversed cir- culations As to whether the flow or the return services should contain the greatest amount of water. THE subject of friction has an important sound, and in theory it ranks as a moderately important subject, but it is doubtful whether the question has more than the scantiest attention from the hot-water engineer. No one can aim at more than constructing the apparatus on as simple a plan as possible, so that the least number of bends, &c., are used. Any other responsibility is met by using a boiler that the makers guarantee to be powerful enough for a certain length of a certain sized pipe.* The boiler-maker, in arriving at the working value of his boilers, has to consider the question of friction to some ex- tent, or, in any case, allowance has to be made for it, as in estimating the result that a certain area of heating surface will give, this is always calculated first upon the basis that no friction or resistance of a like nature exists. Hood gives a table of the relative amounts of friction or resistance by friction that arises in pipes of various sizes. This table is sufficiently accurate for all practical purposes, although not strictly correct as to fractions of quantities * See boilers and the rule as to deductions to be made in arriving at the practical value of the boiler as against the theoretical figures given by most boiler-makers. 88 Warming Buildings by Hot Water. which, however, are really not needed for this purpose. The results are arrived at by emptying the contents of a given sized vessel, from a given height, through various sized pipes. It is found that if water passes out through a i-inch pipe in say ten minutes, it takes less than half this time for the water to pass out through a pipe of exactly double the area, and as the pipes get larger the time becomes less than what is pro- portionate to the size. Diameter of pipes \ I 2 3 4 inches. Friction 8 4 2 1*3 i From this we see that the smaller the pipe the greater the resistance opposed to the motive power, and although it has been shown that the motive power (other circumstances being favourable) is increased by using small pipes which lose their heat faster and so create a greater difference of temperature between the outflow and inflow at the boiler, yet by aiding the circulation in this way we introduce another objectionable feature, which may be said to about equalise and make the effect only the same as a larger pipe. On this account larger pipes have come to be regularly used and the more readily that their cost is less in proportion. In horticultural works it may be said that 4-inch pipe is always used, the only exceptions being in cases where the apparatus is very small, or where the gardener has some special idea of his own, for, as already stated, the gardener usually has considerable authority in this matter. For churches, chapels, and halls, or any places where the apparatus is not working continuously, smaller pipes are often used, as it is desired to heat the building up as quickly as possible after the fire is lighted. One 4-inch pipe with its circumference of 12 inches holds as much water as about four 2-inch pipes with an aggregate circumference of 24 inches : it will be seen from this that the advantage is with the latter, which has so much more radiating surface for distributing heat quickly. On the other hand, of course, it cools more quickly when the fire is slackened ; however, that is not Causes Affecting Circulation. 89 objectionable in church work, though it would be in horticul- tural buildings.* The fact that from a fluctuating fire large pipes distribute heat more regularly than small ones is one of the chief features in their favour, but at the same time nothing is gained by having larger pipes than 4-inch. If it were not for friction it is reasonable to suppose that we might continue the circulating pipes for an enormous dis- tance a mile for instance ; but under present circumstances this would be no advantage. The longest distance in a horizontal direction that the writer ever saw an apparatus carried was 250 feet, extending from the extreme east to the west wing of a nobleman's residence. This, which was upon the high pressure system, worked excellently. In the same way we might consider that the increase of vertical height in an apparatus would increase the motive power proportionately to an indefinite extent, but in this case the friction would eventually reduce it to a mean rate. But fortunately this need give us no anxiety for the present, as the highest buildings we have would not be high enough to bring any objectionable features into play. If an extensive apparatus (extensive horizontally) had to be erected, it would be better to arrange for two or more distinct services to be carried in different directions in pre- ference to one continuous apparatus extended hither and thither all around the building. This would be done by placing the boiler somewhat centrally to the work to be done, or in some instances by taking a main flow and return to a central point and thence branching off in different direc- tions. This will not reduce the friction in aggregate, as we may suppose that about an equal quantity of pipe is used in each case, but in using the long single service the friction reduces the flow of water to the extent that by the time it is nearing its return to the boiler it will have lost all its heat and * The writer knew a church where it was the practice for years to light the fire every Friday evening to heat up the place to a satisfactory point for Sunday. 90 Warming Buildings by Hot Water. be worthless for any purpose near this point. In other words, two or more short services which do not permit of the loss of a great amount of their heat by the time they return into the boiler are preferable to one unusually long service in which a greater portion of the return pipe contains water cooled down to a somewhat ineffective temperature by reason of the comparatively long time that has elapsed since it left the boiler. It will be understood that the length of horizontal pipe could be effectively increased by increasing the height of the vertical portion, as by the latter means we increase both the motive power and velocity. By thus increasing the speed of circulation we proportionately overcome the trouble referred to, as the quicker the water is in getting back into the boiler the less heat it will lose in its passage. Of course there will not be a less amount of heat radiated in the aggregate, that is. in a given time. The whole of the return pipe will be usefully distributing heat, and the heat will be more equally distributed everywhere. The plan of increasing the vertical height cannot, however, well be adopted in horticultural works, as will be understood. In suggesting that preference should be given to two or more services in place of one very long one, it must not be thought that an eighty or hundred foot run is too long by any means. Where there are three or four glasshouses all in a line it is quite the usual and proper thing to heat them from a straight line of main pipes coming from a boiler situated at one end. It is intended to suggest that when there are three or four houses not in proximity or in line, but scattered about somewhat, it is best to take a separate service to each rather than continue the one main service from the boiler around the whole group. This, however, is another question that the gardener usually settles, very many of them preferring to have more than one boiler (of a proportionately smaller size), even though the houses are near enough to be all heated from one fire. It may be here mentioned that never in any two cases Causes Affecting Circulation. 9 1 will opinions as to the planning of a work be found to agree, but the principle involved is of course the same always. As already explained several times, the power which brings about the circulation in horticultural works of an ordinary character is, at the best, feeble. On this account every care should be taken in carrying out the work after it is planned, for, granting its arrangement to be good, it is just possible a small fault introduced will have a disastrous effect. The most common cause of this in new work is the introduc- tion by inadvertence of some foreign material into the pipe. Some men leave the ends of unfinished services open when they leave their work, and something may chance to get in ; or in the reverse case, when men temporarily plug the un- finished end with a cloth or some such material, instances have been known where it has been accidentally pushed in and lost sight of. It may not seem necessary thus to dwell upon the possible careless actions of a workman, but it has to be remembered that it is after the apparatus is finished and being tested that the trouble first arises, and a very serious trouble it usually proves. Firstly, it has to be ascertained what is the cause of the bad or eccentric results. The workman has no know- ledge of his blunder or oversight, and the true cause is generally the last thing to be thought of, if it is thought of at all. Usually the faulty part has to be located as nearly as possible, and then the work has to be undone to a greater or less extent. Difficulties of this kind are specially connected with quite new work, but with an apparatus already in use a sudden failure in some direction cannot usually be attributed to defective workmanship, as it can be recognised as an in- flexible rule that if an apparatus works efficiently once (under ordinary conditions) any fault that may be developed after- wards can rarely be blamed to the construction : it must be due to some other natural cause, an obstruction for instance, unless of course the apparatus has been subjected to an accident. The causes of erratic results are practically confined to 92 Warming Bitildings by Hot Water. air, or the introduction of some foreign substance, which either checks or for a time stops the circulation. In the latter case it may be leaves or rubbish if ditch or pond water is used at all carelessly. Of course there are other things that will bring about an unexpected stoppage of work, such as a failure in water supply, &c., but with an apparatus which customarily works with steadiness and regularity any little unexpected trouble is usually due to one of the causes named. Water that is of a varying temperature is always under- going a change in its aeration, absorbing and expelling air, and on this account the air vents have more use than merely allowing for an escape of air when the apparatus is first charged. Every hot-water fitter knows that when first charg- ing it is more difficult to expel the air from an apparatus than is commonly supposed, so that it is quite understood that if an apparatus is allowed to get a little short of water, so that air enters one of the pipes, some trouble may ensue. When once an apparatus is working with regularity every care should be bestowed upon it to keep it so. Hood speaks of the phenomena of hot water ascend- ing the return pipe, and the colder water coming down the flow ; that is to say, the water in an apparatus circulating in a contrary direction to that which it is intended to do, although the pipes are correctly connected at the boiler. " This," he says, " may arise in an apparatus having but a small motive power, and in which the principle has not been followed out, of making the water rise to the highest point as soon as possible ; also having in the flow pipe much more pipe and impediments than in the return, so as to create a greater resistance by friction ; and having a greater bulk of water in the ascending pipe than in the return ; and also with boilers which are low in depth." In horticultural works the quantity of pipe, &c., in main and branch flow and return services, is usually about equal, but when there are say five pipes, the odd one is put either in the flow or return according to the judgment of the engineers, some considering one way correct and some the other. In Causes Affecting Circulation. 93 truth, it is doubtful whether with one single pipe there is any noticeable difference either way. A large and well known firm, who bear a high repute for this work in and around Middlesex, always put the odd pipe into the flow, that is to say, if a forcing house is heated by a branch flow and return service containing five pipes, three would constitute the flow and two the return. This has always proved eminently successful. This method, however, will appear to be opposed to Hood's argument, but it really is not so, as he refers chiefly to apparatus designed for warming buildings which have a number of coils, radiators, or stacks of pipe in connection with the main services, and with this he very rightly recom- mends that, if not all, at least the bulk of these appliances should be on the return. However, this subject will be dealt with separately. The reversing of the circulation is very likely indeed to be due to the use of a very shallow boiler, in which a very small distance exists between the points where the flow and return pipes enter the boiler ; but this of itself would not be sufficient to cause this phenomenon, though it would be favourable to any other cause that might be active. This, however, is an occurrence exceedingly rare, and in horticultural works if the return pipe is found hotter than the flow it may be taken for granted that an obstruction exists air probably ; or that the supply of water is insufficient, and the flow pipe partially empty. In experimenting with a small copper boiler having a system of circulating pipes in connection with it, the writer on one occasion noticed that the circulation had started the wrong way, and as the apparatus was constructed upon correct principles, and had worked correctly on all previous occasions, it was for the time rather puzzling to fix upon the real cause. The first thought was that some unusual feature might exist somewhere, as the apparatus by much alteration in experi- menting had become rather complex, but examination proved that the results should be normal and no reason appeared for 94 Warming Buildings by Hot Water. the reversed circulation which was proceeding strongly all the time. The last thing to be noticed was that the lamp was not standing centrally under the boiler, but was giving all its heat immediately under the return pipe. The return pipe came through the top of the boiler, projecting down a few inches inside. This was suspected to be the cause of the fault, and further experiment with a simply constructed apparatus showed conclusively that it is not at all difficult to get a reversed circulation by applying the greatest heat to the vicinity of the return pipe.* In the majority of cases the return pipe enters the side of the boiler, which arrangement greatly obviates the likelihood of this trouble occurring. In very many cases, however, the return pipe, when it comes into the boiler side, has to pass through a flue where it feels a considerable heat, and if by a blunder a vertical portion of this pipe was placed within a flue or any heated position the effect of the heat would very greatly favour a return circulation, and in any case it would impair the efficiency of the apparatus, most probably ruin it.f Perhaps amongst the phenomena that may be experienced in this work, the most peculiar is the eccentric way an apparatus will sometimes work in which there are, say two branch services carried off from a main in contrary directions, yet both starting equally, and both having about the same amount of work to do. In an instance like this, every engineer knows that it is the exception for the two services to work equally, i. e. for both to heat up in the same time, and both distribute an equal heat. Yet instead of one proving to be more efficacious than the other permanently, it will frequently be found that they will act to an extent alternately, * These experiments were only conducted with a boiler having the return pipe brought in through the top. f Of course every practical man avoids carrying the return pipe into any heated position. When it has to pass through a flue surrounding a boiler, it is usual to cover it with brickwork, and there is one point in the boiler where the pipe can enter and yet not be subjected to much heat, although it passes through the flue, but in every case a covering of brick- work should be resorted to. This will be more fully explained later. Causes Affecting Circulation. 95 sometimes one taking the lead and sometimes the other, with- out any apparent reason. Of course a remedy for this should exist in every apparatus in the shape of a proper provision of stop (or throttle) valves, which are inserted with a view to the regulation of the heat to any desired degree at any point, but apart from the remedy, the peculiarity remains at present unaccounted for. In this case it has been ascertained with tolerable certainty that air is not the cause of the trouble, and it would be hard to attribute it in any waylto irregular stoking. To the writer's mind, the most feasible solution is that these instances of fitful- ness of the circulation are due to variations in the weather. In two houses, or two different positions, we must have one more subject to external influences of heat or cold than the other, and external influences always influence the apparatus in the greater or lesser absorption of heat by the air from the pipes. This would only happen to a noticeable extent with branch services that have each about an equal amount of work to do, and such is really the case, as services which differ considerably from one another do not, as a rule, exhibit this phenomenon. In a small and simple apparatus it would not matter very much which way the water circulated provided it was regular in distributing a sufficiency of heat, but in a larger apparatus, any irregularity must bring about some ill effect and annoy- ance, to say the least. 96 Warming Buildings by Hot Water. CHAPTER VII. EXAMPLES OF HOT-WATER APPARATUS. Describing some examples of the average apparatus A small apparatus for a lean-to greenhouse Description of boiler Arrangement of pipes Water Supply, etc. Another apparatus suited for a small conserva- tory General description, position of boiler, etc., etc. Description of another conservatory apparatus A larger apparatus to heat two glass houses Pipes in channels General description A large apparatus to heat a range of five glass houses with melon pits Main pipes and their uses Carrying mains in trenches Branch services Pits with bottom heat Evaporating troughs Capacity of air for moisture Necessity of providing moisture Position of pipes as regards roots, shrubs, &c. IN studying a few examples, which we describe, of the average description of apparatus that is to be met with, it must be clearly understood that the illustrations are not made with a view of providing designs to which other works can be erected. In the first place, it would probably be found utterly impossible to adapt any of them to a new situation. Secondly, it is best and proper to work out and plan each apparatus that has to be constructed in a manner best suited to the require- ments, not giving any particular thoughts to previous under- takings. There is scarcely a doubt that of the many such works erected in England there are not two precisely alike, so vary- ing are the circumstances that have to be taken into account. Still, those whose knowledge of such work is limited will find considerable assistance from the consideration of an apparatus practically complete and in position. A mere explanation of the principles governing the work is hardly sufficient, unless the reader has already had considerable practical experience. After this chapter, appliances (boilers, materials, joints, &c.) will be fully dealt with. Examples of Hot-water Apparatus. 97 Perhaps the most simple form of apparatus that is ever erected in connection with a boiler heated with coal fuel is at Fig. 56. This is simply a flow and return pipe run up Fig. 56. along one side of a greenhouse, the pipes being most probably 3-inch. This is a sort of apparatus used chiefly for small amateur purposes, for a small sized glass house attached to, or in the garden behind, a suburban residence. The illustration shows a somewhat recent innovation as regards the boiler. Previous to this form being introduced a brick-set boiler would have been required, or else one of the common independent form. In the latter case an objection existed in that the boiler had to be in a sheltered position, most probably in the greenhouse itself; in this case the pre- sence of the boiler might not be so very objectionable, but in the majority of cases the unsightly flue pipe had to have a prominent position ; and in any case all stoking and attention and the attendant dirt and dust, occurred inside. The boiler illustrated is constructed in such a manner that it can be fixed in the substance of the wall itself, as Fig. 57, which shows a section of the wall with the boiler in position. By this arrangement the flue pipe is conveniently disposed outside, and all feeding, stoking and cleaning takes place outside also. The pipe connections are. of course, inside (as shown), and as there is no need in this case to place H Warming Buildings by Hot Water. Fig- 57- the boiler out of the way or in an inconspicuous position, it can be placed (other circumstances permitting), so that the pipe can be carried straight away, as shown, and so save the cost and other objections that the introduction of bends and elbows brings about. With this boiler there is but little heat radiated from the body of the boiler itself, as there would be if it stood wholly within the house ; yet even in this case there is little actual loss, as the boiler, being im- bedded in the wall, the poor con- ducting property of brickwork pre- vents the escape of heat, so that it remains in the water and escapes from the pipe surfaces only (excepting that which is radiated from the boiler front). The other extremity of the apparatus is shown terminating in a supply and expansion box, as recommended on p. 56 This contrivance cannot be overvalued, as it is so neat, so accessible, takes the .place of the supply cistern and its neces- sary connecting pipe, dispenses with the air pipe, saves a connecting piece at the end, and provides a substantial sup- port to one end of the apparatus. This appliance cannot usually be made self-filling with the customary ball valve, unless a small cistern be introduced, as the expansion box itself is rarely made large enough to take a ball valve, which requires an inconvenient amount of room. With an apparatus on a small scale, however, an arrangement for self-filling is not only unnecessary, but is a positive drawback, since the evaporation being so slow and the loss of water so slight, there is not sufficient work for the ball valve to keep it in order. As most people know, this appliance works stiffly and " sticks " if not in constant use. In an apparatus even as small as this the pipes should be made to rise towards the extremity, to assist the circulation and to permit of the free escape of air. This can be effected Examples of Hot-water Apparatus. 99 by standing the expansion box on a slight elevation (a tile or some bricks) if necessary. The use of this boiler necessitates starting the flow pipe horizontally, and as the total difference between the highest point in the flow and the lowest point in the return is but a matter of inches, the motive power is small, and no obstacles could well be permitted. It is not a boiler to recommend for large purposes if fixed in the way shown. If such a boiler be used below the greenhouse level, the flow pipe should be taken from the top. Fig. 58 introduces another form of apparatus almost as simple in form as the last, but in this case it is supposed Fig. 58- that a greenhouse or conservatory attached to a residence requires to be heated, but the boiler has to be situated in a cellar or basement room of the house (in proximity to the work). On the left-hand side of the illustration is shown an inde- pendent boiler of an ordinary form ; and as it is in this case fixed below the level of the work, the flow pipe is taken from the top, the return entering the side near the bottom as usual These vertical independent boilers are admirably suited for H 2 i oo Warming Buildings by Hot Water. such a purpose as this, their shape making them convenient as to the room they occupy, the necessary fixing is reduced to a minimum, as they are quite independent of brickwork, and merely require to be connected to the hot-water pipes and to a chimney ; the latter is effected by a length of iron pipe and an elbow. They are made complete with fire-box, ash-pit, feeding and stoking doors, and only require to be stood upon an earth or stone floor, or if the floor be wood, a stone or concrete base has to be provided. When fixing a boiler of this character it is necessary, to make it work effectively, that the flue pipe fit on the nozzle of the boiler tightly ; if it does not fit accurately, then let it be jointed with stiff putty (ordinary glazier's putty). Where the flue pipes are jointed together, and where the pipe or elbow enters the chimney, the joints must be sound and tight also, or a leakage of air or draught will take place into the chimney with a proportionately ill effect. Every description of close fire boiler, stove, &c., thus requires great care in fixing, as all the air that passes into the chimney should first pass through the fire ; if any other opening is left by which much air can pass in, the draught through the fire will be slackened and the boiler will not heat effectively. This will be spoken of fully when treating of chimneys. A vertical-shaped boiler is particularly adapted for holding a charge of fuel which is delivered in through the feeding door which is always situated at the top. Small horizontal boilers do not meet this requirement quite so well, although these can have a means of so doing if required, but hardly so well as with the vertical shape. It will be readily understood that in such a case as this it is very desirable that the boiler should hold a store or charge of fuel sufficient to last a number of hours without attention, as in all probability the stoking may be done by a domestic servant. This end is met perfectly in a vertical boiler, as a medium-sized one will hold perhaps i^ bushel of coke, sufficient for twelve, or at least eight hours ; and once the use of the dampers is understood, the temperature can be kept at a regular point continuously. Examples of Hot-water Apparatus. 101 Fig. 59- Every boiler of this description has the stoking and ash pit doors arranged so that they can be used as dampers or draught regulators, but, unless carefully attended to, they do not bring about such regular results as a sliding or throttle damper in the flue pipe will do. Considering the small outlay involved one of these latter should be provided in any case, especially as they are better understood by inexperienced persons. Fig. 59 illustrates a sliding damper, this damper and its frame being made in and part of a length of flue pipe. This is by far the best of all dampers. Fig. 60 shows in section what is called a throttle damper, being a disc of iron which by a handle attached can be made to lie at any angle to retard or to give free way to the draught. This can not well be made to fit accurately, and a great drawback is that unless very nicely balanced it will not stay in the position it is placed at ; it may by the up current or draught swing open (or close), and even if it fits well at first, wear, or ex- posure, &c., will afterwards make it work erratic.- It may be mentioned here, although it will again be referred to, that in charging these boilers with fuel, some care or experience is needed parti- cularly as to the size of the coke. When the boiler is filled up with fuel it is with the view of providing a store of fuel at the top to automatically replenish the part below as it burns away. The automatic action is merely the gradual fall of the upper material by its own weight as the lower is con- sumed. Now every one knows with what tenacity pieces of coke will cling together, and if we filled a small boiler with pieces of medium size we should find that in many instances it would refuse to fall freely, and although the lower part burnt away, the upper part would wedge itself up and be- come " bridged," as it is called. The maintenance of the fire Fig. 60. IO2 Warming Buildings by Hot Water. depends upon the regular and gradual fall of the fuel, and this is made certain by breaking the coke very small, that is, to walnut size for conservatory boilers in general ; with large boilers, of course, a larger fuel is permissible, as the ' bridging " does not take place so readily in a larger area. On the right of the illustration Fig. 58 is shown an arrangement of pipes that may be in connection with the boiler just referred to. There is no need to show how the pipes are carried through the space that may be between the boiler and the greenhouse, as this will now be quite under- stood. They are simply carried by the nearest route, and care must be exercised to see that they do not dip down in their course anywhere, but are either carried horizontally or with a rising inclination. The connection of the pipes, how- ever, at the boiler and at the commencement of the radiating pipe is shown, and each pipe marked, namely, F flow, and R return. With this apparatus it has to be explained that the pipes between the boiler and the greenhouse do not by any means require to be large, certainly not the large cast pipes such as will be fitted in the greenhouse itself, as these would be most awkward to use, of greater expense, and quite unnecessary. The pipes between the points named need not be larger than i inch for a moderately small purpose, or ij inch or I \ inch if the conservatory is of good size and has a fair quantity of radiating pipe. Wrought iron tube is used for this ; it is easy of adaptation, is neat, and very reasonable in cost. In ordering the boiler it must be required to be drilled and tapped for whatever size of pipe is to be used. The cast radiating pipes have ends fitted to them which can be drilled and tapped in the same way for connection. The illustration shows three rows of pipes carried round two sides of the house, two flows, and one return. Let it be clearly understood that it is not always necessary to have three pipes, in fact it is not usual, two pipes only, one flow and one return, being generally sufficient and customary for this small purpose. Three pipes are shown, however, to Examples of Hot-water Apparatus. 103 illustrate the ordinary method of adding the extra pipe if needed. For instance, suppose the conservatory to be used only as an adjunct to a ball room, in which instance it might be filled with hardy shrubs and heated only as occasion demanded. In this case three 2-inch or 3-inch pipes would give quicker and more economical results than two 4-inch pipes, as has already been explained. Or, supposing the conservatory to be a lofty one in regular use and having sub-tropical trees in it, then two pipes would probably be insufficient. The pipes would be arranged so that the extremity where the air pipe is situated is higher (by several inches if possible) than where they first start off horizontally* after coming through the floor. When the pipes extend away around the house as these do, it is very necessary that they have support at different points. The nature of the support varies very greatly, different engineers having different views upon the subject. A very common method is to use brickwork, a small column Fig. 61. Fig. 62. being built up to and around the pipes as Fig. 61. This is a very good and workmanlike practice, but it is hardly admis- sible if the pipes are situated in a conservatory fully exposed to view, and recourse is then usually had to iron in some form. A very good iron pipe-support is made, as Fig. 62. These are made for any number of pipes one above the other, or they * In speaking of horizontal pipes in this work, it is understood that they are slightly rising towards one extremity. IO4 Warming Buildings by Hot Water. can be had suitable for two rows of pipes ranged side by side. Another form is simply a wrought-iron strap bent to the shape shown at Fig. 63 ; this, however, is only of use when the pipes run along a wall or partition, as the Fi s- 6 3- straps require to be secured to something at the back of the pipes, as will be understood. When the strap is used, a strip of wood is stood up between the wall and the pipes, as it is not desirable that the pipes bind firmly against the wall ; in fact, they should hang in mid-air, so to speak, so that free radiation of heat from the whole of the pipe surfaces be assisted. Of course, any other form of support is permis- sible, provided it is of firm bearing, not likely to lose its shape or rigidity. Some care must also be ex- ercised to see that the foundation to the support is good, or the weight of the pipes or some other cause may make the support sink and the pipes become uneven and out of level. This occasionally happens with brick piers, which are weighty in themselves, and if placed on the earth without care may soon sink down to some extent. The cold supply to this apparatus need only be provided for by a small cistern, filled by hand, as the loss by evapora- tion would be so trifling, insufficient to make the use of a ball valve at all necessary. This small cistern should be placed at the most convenient spot, out of sight if possible ; or, if not, it may be fastened on a wall and decorated, but it need only be just above the level of the highest point of the flow pipe. It is never a good plan to place these cisterns more than, say 3 feet (a few inches is sufficient) above the point mentioned, as there is no need for it ; it makes the regular replenishment a little more troublesome and more likely to be overlooked, as the want of water could not be observed so readily ; and, lastly, it increases the strain upon the joints and apparatus generally. (See Pressure of Water in Pipes, p. 255.) The cold supply pipe need not be larger than half-inch in Examples of Hot-water Apparatus. 105 a small apparatus like this, and it should be carried and con- nected into the return pipe near the boiler, or into the boiler itself, otherwise the contents of the cistern will probably get heated (notwithstanding the dip in the pipe), and vapour will rise from it. This would not very much matter in some instances, but it is not desirable in a conservatory. If, how- ever, the boiler is a distance from the work, then the cold supply may enter the return pipe at some other point, but let it be as much below the radiating pipes as possible. In any case the customary dip is needed in this pipe close to where it enters the return, and this dip should be about 12 inches deep if possible, to prevent the heated water travelling up this pipe as has been already referred to. Although the dip in the cold supply pipe is necessary, and is supposed to appear in every apparatus that is rilled from a cistern, there is one noticeable drawback, namely, the liability of this dip becoming choked with dirt which cannot be washed out or removed without taking the pipe to pieces. This is greatly aggravated by the practice of leaving the lid off the cistern, so that dirt and matter finds its way into it, and this eventually reaches the dip where its further movement is stopped, and should rain water be used, there is even a greater liability of stoppage, as will be understood. This drawback is quite recognised, and occasionally preparations are made for its cure ; but the only remedy that is at all worthy of recom- mendation is the provision of a screw plug at the lowest point in the dip, and if the dip is abrupt, that is to say, the two pipes close together, then a stoppage can be readily disposed of by the insertion of a wire or cane. The next apparatus, Fig. 64, exhibits an arrangement differing from the last, as it is desired to heat a small glass- house or conservatory around all four sides. It cannot be arranged for the flow and return from the boiler to be con- nected at either of the extremities of the radiating pipes, and consequently the apparatus becomes one having, to all intents and purposes, branch services from the primary or main flow and return pipes. A certain care then becomes necessary to io6 Warming Buildings by Hot Water. arrange for the branch in each direction to heat equally or at any rate to work without a noticeable irregularity. In this apparatus, as with the last, it has to be explained that an unusual feature is introduced, as it is rarely necessary, Fig. 64. .s_ i-> 9 00 r 1 V 3 r '- T and more rarely customary, to heat (i.e. carry pipes around) all four sides of a conservatory ; but the illustration will serve to explain how to treat these branch services, whether they extend as far as shown, or a less distance. We may suppose this apparatus to be heated by a small independent boiler placed in a basement or some such point contiguous to the work, but, of course, below the conservatory floor level. From the boiler to the radiating pipes there need only be a i-inch or ij-inch flow and return, connected and dealt with in every way as described with the last apparatus and in Fig. 58, and the pipes are marked F and R in the same way as in the preceding illustration. We may suppose that this house is not very large, in which case, if the pipes are carried all round, 3-inch would be sufficient. This is governed by various circumstances, and recourse must be had to the rules and calculations provided to determine quantities, sizes, &c., for heating certain areas Examples of Hot- water Apparatus. 107 and for certain purposes. This subject is dealt v/ith fully in Chap. XL Should the calculations prove that a third pipe is requisite or desirable, this can be added as explained in the last apparatus, that is two flows and one return. If it were thought best, one branch might have two pipes as illustrated, and the other three, that is two pipes round one end of the house, and three round the other ; but this is quite an excep- tional requirement. It will be noticed that one branch has to travel farther than the other, as the primary flow and return does not enter at an equal distance from the door either way. Consequently, if some care is not used, there will be every likelihood of the shortest branch " taking the lead " as it is termed, that is a rapid circulation setting up in the short branch to the preju- dice of the longer one, and causing the circulation in the latter to act sluggishly and to be of less heat-giving efficiency than it should be. In a large apparatus this is fully expected with some of the branch services, and provision is made for its proper regulation by means of throttle valves, the faster heating services being checked that the sluggish ones may attain a normal circulation and so on, according to the wishes and requirements of the gardener. But in a small apparatus such as we are discussing, the use of regulating valves for this purpose is unnecessary, normal and sufficiently regular results being easily obtainable by giving a greater rise to the long branch than the shorter one, and this greater rise will be found to counteract the greater resistance that the increase of length offers. At the highest extremity of each branch an air outlet has to be provided as shown, these being connected and carried* in one of the manners described on p. 82. The pipes have also to be supported well and securely, as described with the last apparatus explained. As the work gets larger, attention must be given to the question of expansion, as although in a small apparatus the elongation of the pipes when heated is so trifling as to be unnoticeable, yet in a large one, where long runs of pipe exist, 1 08 Warming Buildings by Hot Water. consideration must be given as has already been explained, but it is only in what we may consider very long lengths, that rollers and frictionless bearings on the supports are needed. When pipes are supported on any of the iron stands referred to, there is so little friction that a moderately long length of pipe moves easily upon it as the expansive force, or the reverse is exerted ; but in brick piers the resistance by friction is greater, and with these, roller bearings for the pipes would be needed with a shorter length than if the supports were iron properly constructed with the bearing surfaces reduced to a minimum. But the fact of building a brick pier support around the pipes as explained and shown in Fig. 61, does not materially increase the friction over a plain brick pier which would not cover the pipes, as it will be found that when once the apparatus is heated, which to a trifling extent increases the girth of the pipes, the brickwork will no longer firmly bind upon the pipes, and any movement lengthwise will experience no particular resistance, the brickwork having ceased to hold the pipes with any degree of tenacity. The cold supply should be provided for and connected in the manner described with the last apparatus, and reference should be made to Chapter III. The next form of apparatus, Fig. 65, we may describe, is one in which the work is a step further than that just com- pleted, and one in which we may suppose there are two glass houses to be heated, these houses joining one another end to end as is customary, but requiring different temperatures for different purposes, this being the primary reason, of course, that there are two houses instead of one larger one. Although these houses are spoken of in the plural sense, it will be found in almost all cases that the erection, in reality, is but one house, with a division in it, so that plants or fruit requiring different temperatures, &c., may each have the distinct treat- ment and an atmosphere which is most congenial to them. When the house is divided in this manner, the partition is commonly of wood and glass, but, whatever it is composed of, there is always (there may be exceptions) a doorway in it, Examples of Hot-water Apparatus. 109 and this interferes with the carrying of the pipes all round the house in anything like a simple manner, as in addition to the doorway in the partition we may as a rule expect to find a doorway in each end also as shown. Of course, a doorway TOT USI7BR5ITY 1 1 o Wanning Buildings by Hot Water. can be passed by dipping the pipes ; but this plan is very rarely resorted to in practice, it is not natural and under the best of circumstances it is in some degree prejudicial to success ; and perhaps one of the greatest objections to it is that a dip in a pipe must prove a collecting point for dirt, and is rarely accessible for easy cleaning even if such a provision is thought of. It is quite customary, with an apparatus such as we are describing, to carry the pipes around one-half of the house as far as the doorways will permit, this half being on the most- exposed side. As glasshouses are so often built against a wall there is no noticeable objection to this arrangement, supposing a very high temperature is not needed. When a high temperature is required, arrangement is then made (if possible) to carry the pipes on all sides, and some- times also up the centre, every available point having pipes if the house is for tropical plants or fruits, orchids, &c. Unless there is some very strong objection, it is always arranged for the hottest house to be nearest the boiler. It is exceedingly exceptional for this latter arrangement to be impracticable, as upon the erection of hothouses every forethought and care is given to their being successfully heated, and, as before- mentioned, it is the regular thing for the gardener to superin- tend and to direct the works generally. The illustration represents two houses, which we may suppose are of fair size, situated against a wall at the back, and having a passage-way through the centre, thus introducing a door at each end, and one in the division as shown. The boiler (of saddle or any customary shape, or it may be of the independent kind, although this is not usual), is fixed in a pit at one end near to the wall, or it could be on the other side of the wall if more convenient or desirable. The pipes in this case would be of full size where connected to the boiler, and continued of full size throughout the apparatus, 4-inch being the most suitable for work of this size and character, or 3-inch is permissible if specially wished for. In this case the pipes from the boiler would need to enter the house below the floor level (the top of the boiler being Examples of Hot-water Apparatus. 1 1 1 12 inches or more below this point). Immediately where they enter close to the wall they require to be branched, one branch instantly rising and being carried along the back wall (one flow and one return), and around as far as the middle doorway, as shown. The other branch is carried along inside the end of the house nearest the boiler, but still below the floor-level until the doorway in this end is passed. This pipe thus carried adds its proportion of heat to the total result, as it is placed in a brick or tile trench, and covered with an open grating. When pipes have of necessity to be placed in channels or trenches, allowance must be made for lessened results due to absorption of heat by the surrounding brickwork, &c. The top gratings should be easily removable, as on no account must the pipes be allowed to get coated with dirt, nor must dirt be allowed to accumulate around them, as they would then cease to distribute heat and might as well be covered over entirely without the expense of the trench and grating. Pipes in trenches, however carefully attended to, do not add to the heat of the atmosphere in an equal proportion to the pipes that are out of channels, and in calculating quantities this must be remembered and allowed for (particularly in church work, &c., in which exposed pipes are not permissible except to some trifling extent where they are hidden from view). This will be found more fully explained in the calcu- lating tables. The illustration shows the branch (from the boiler towards the front of the house) carried in a trench along the full length of that end before it is elevated, but it will be under- stood that the elevation may, if desired, take place im- mediately it has passed the door. Immediately the pipes are brought up out of the channel they are carried along the front of the house, but upon the supposition that considerable heat is needed, the flowpipe is shown with an extra pipe added, this being usually required in a tropical house, and oftentimes when the house is of good size and cannot have pipes on all sides. ii2 Warming Buildings by Hot Water. The branch now being spoken of may consist of four or even six pipes. This branch, as already explained, is carried along the front of the house as far as the division where it turns, and is continued as far as the door. At this extremity the three pipes are reduced to two, which are carried through and back along the division on the other side in the other house, and there continued along the front and around the further end as far as the door, as shown, this house being we may suppose for more hardy plants a greenhouse, in which case the two pipes along the front and halfway up each end will usually give a sufficient heat. At the point where the three pipes of the hothouse are reduced to two and carried through into the greenhouse, there is the possibility of unsightly work being introduced unless a box end is introduced. This gives much more sightly results, and also to some extent reduces the labour, it also forms a support at this point, where one is much needed. This box end is similar to Fig. 66 which shows three pipes entering at one side and two leaving at another side at right angles as would be required in this case. It must not be forgotten that throughout this apparatus (and throughout all that may be erected) the pipes must be fixed to have a gentle rise all the way from the point nearest the boiler to the furthest extremities. This has already been insisted upon, but it is desirable perhaps to repeat it. In an apparatus that extends through two or more houses it is necessary to introduce stop-cocks or valves to regulate the heat, &c. In such an undertaking as we have now under consideration it may be supposed that the heat in the green- house may not be required during mild weather, yet in the hothouse heat is necessary even during the summer, and in such a case a means must be provided to partially or wholly check the circulation beyond the partition. This would be effected by inserting stop-valves of some description (see pipes, fittings, and appliances), in the two pipes immediately Examples of Hot Water Apparatus. 113 where they enter the greenhouse through the partition, as in Fig. 67, which shows the box end already referred to, but with the stop-valves attached to the two pipes just as they enter the greenhouse. The cocks are thus situated so that they effectually bring about the result desired, yet they do not, when closed, interfere in the least degree with the circulation in the first house. This is a very necessary consideration. Stop-cocks and valves can be had in any size, but in such an apparatus as this there is no need whatever to have them of the full size of the pipe 2-inch will be sufficient without any risk of impairing the general efficiency ; as in a small undertaking, rapidity of circulation is of no moment, the extent of the services being limited, and a very rapid circulation would only tend to convey the hot water back to the boiler for no good pur- pose ; whereas, if we check the circulation in a small appa- ratus we get a stronger motive power by reason of a greater difference in the temperatures of water leaving and entering the boiler, and this at no risk of diminution of the heat evolved. It must not be forgotten that the chief reason for using smaller stop-valves is the lessened expense, these articles being rather expensive if of good quality. The use of smaller stop-valves, however, has to be made with discretion, it lies chiefly with the distance that the pipes have to travel after leaving the boiler. If the work is of great extent every care has to be used to prevent the cir- culation being checked as it is of no use having the water travel a great distance if it is barely warm when it arrives.* The same care has to be bestowed upon the question when the circulation from some cause is sluggish. Air vents are * The majority of gardeners are now rather averse to very extensive runs of pipe, preference being given to the use of a second boiler. More reliable results and oftentimes greater convenience is experienced. I H4 Warming Buildings by Hot Water. needed at the highest points as a matter of course. There is one shown at the box end at the division of the houses ; this is necessary, as will be easily understood from the illustration. From the doorway nearest the boiler there is shown a trench and grating carried up the middle of the house as far as the division doorway. If it is thought necessary two (or more) pipes may be carried up in this direction, in this man- ner, this service being a branch from that which is carried beneath the floor level past the doorway. To keep the trench as shallow as possible, the two pipes should be carried side by side as in Fig. 68. This at any time giving better results than pipes one above the other, if they are in trenches, or in some cases the cost of trenching can be avoided, and the pipes run along in the open at the side of the path or footway as in Fig. 69. This service would require an air outlet Fig. 69. Fig. 68. at the extreme end, which of course is understood to be the highest point ; but this air pipe need not be carried up inde- pendently, it may join any other air pipe that is nearest to Examples of Hot-water Apparatus. 115 it, but as already explained it must not be allowed to dip down anywhere, but must ascend all the way. The cold supply to this apparatus would be provided for by a cistern (with cover) in the usual way, the service pipe from the cistern being connected into the return at a near point to the boiler, or into the boiler itself. There is, however, an objection to taking the cold supply into the boiler in an apparatus like this, inasmuch as, unless special provision be made, some difficulty will be experienced in disconnecting it, which is very likely to become necessary as the dip or " siphon " in this cold service so commonly gets stopped with debris. The cold supply pipe in this case would not be larger than |-inch (some may use ^-inch), and this readily be- comes stopped at the dip, where dirt quickly collects, if pond,, rain, or ditch water is used for rilling. On this account it is desirable to keep the pipe clear of the brickwork surrounding the boiler, so as to be readily disconnected if desired, yet at the same time let it be attached to the return pipe at as near a point to the boiler as possible. It has already been mentioned that one reason for bring- ing the cold supply into the return near the boiler is that it may enter where the coolest water is, and so the contents of the cold cistern be least likely to become heated ; but in an apparatus such as this it becomes necessary to have the cold supply somewhere on the boiler side of the division between the two houses, as, were it connected to the pipes in the greenhouse, the water supply (as well as the circulation) would be cut off when the stop-cocks were closed. The branch that is carried round the back of the hothouse should not be given much rise, so that the circulation in this direction may not outdo that in the other direction, where it has more work to do. It is hardly necessary to insert stop- valves* in this back branch, if it is kept nearer the horizontal * The names " stop-cocks " and " stop-valves " have hitherto been used indiscriminately, but the different uses they are intended for will be explained when treating these articles and appliances generally. I 2 1 1 6 Warming Buildings by Hot Water. than the other ; this usually proves sufficient check in a moderate-sized apparatus like this. We can now proceed to describe another form of apparatus as illustrated in Fig. 70,* which is upon a still larger scale than those already treated and which introduces a new feature that usually becomes necessary when more than two houses are heated from one boiler. This particular feature is the " main " service, which is practically a primary flow and return, the general work being done by a number of branch or secondary services from it. The real uses of this main service are twofold, firstly, if say four houses in a. line were required to be heated from one boiler it would be impossible to hope for anything like good results from the house furthest from the boiler if the circula- tion had to work through all the ramifications of the pipes in the first three houses. In fact it is doubtful if any very good results would be obtained in the third house unless cir- cumstances happened to be propitious. Secondly, if the pipes were continued from one house to the other as just described it would be impossible to close the stop-valves in any one house without seriously interfering with the heat in the houses beyond it ; and it is absolutely necessary that each house have means to regulate its heat without in any way prejudicing the results in the others. In the illustration, Fig. 70, the main pipes are shown carried along the front of the first three houses with the view of affording heat to some melon pits as shown ; this is a very common practice and there is no objection to it, but if the melon pits did not exist, then the main pipes might be carried up the middle of the houses in a channel, or * These illustrations are of houses which are bounded upon one side by a wall. This is an arrangement usually sought for, but not always possible, particularly in large professional growers' grounds where there are ranges of houses side by side, necessitating the use of what are known as span houses, and which, on account of their width, usually have pipes carried along each side instead of on one side ; and when the house is of good width, there may be pipes carried up the centre (under the stages) as well, as there would be a foot-way on each side. Examples of Hot-water Apparatus. 117 1 1 8 Warming Buildings by Hot Water. better still, they might be carried along the outer side of the back wall (on the same side of the wall as the boiler.) See p. 120. In any case the main pipes should start as far below the level of the house floors as conveniently possible so as to afford a gentle rise along their full length. In addition to this, allowance has to be made for each branch service to rise a little after leaving the main, and to effect this it would be very desirable in a large undertaking like this to have the boiler top 2 feet below the floor-level of the houses if possible, but this is very usually governed by the nature of the ground, as in some situations water is met with a very little way below the surface, and a deep boiler pit is out of the question. If the boiler pit cannot be of ordinary depth by reason of water being found near the surface, it becomes necessary to use one of the several forms of shallow boilers which are made expressly for this emergency (see Boilers, p. 205). Or perhaps the houses may be placed on sloping ground so that a rise is naturally required for the pipes as they go from house to house this arrangement obviates the necessity of putting the boiler lower than is barely necessary to start the pipes horizontally into the first house. The main pipes, in this latter case, need not be lower than the floor-level unless it is necessary to carry branches beneath doorways, &c. ; but should the houses be quite level and extend a good distance, as these do, then it is desirable to start the main as low as possible so as to give it as much rise as can be obtained in its journey to the extremity of the apparatus. When the houses are on rising ground this latter necessity does not arise, but it is the customary and generally desirable plan to carry the mains below the floor level some little distance. In the apparatus under discussion the melon pits, through which the mains run, are a little lower than the houses they lean against ; this is arranged and planned in concert with the gardener's wishes and ideas. There used to be a controversy as to the correct size of main pipes, one suggestion being that the proper sized pipe Examples of Hot-water Apparatus. 119 to use was one having a sectional area equal to the aggregate areas of the branch services, that is to say, if there were eight branch services of 4-inch pipe, then the main pipes should have a sectional area equal to the combined areas of eight 4-inch pipes. It is needless to add that this would make the mains of enormous proportions. Theoretically this argument carried weight, but in practice it was all wrong. The large size was most inconvenient and costly, the extra quantity of water contained in such large pipes was unnecessary and objectionable in other ways, and it was found that 4-inch mains were ample even for the most horizontal works, and even 3-inch mains have been found sufficient where a more than usual rise and fall has been attainable and in residence work where a deal of vertical pipe exists the mains rarely exceed 2-inch, and are not commonly as large as that. The greater the rise and fall the less size the mains need be, but in horticultural work 4-inch is usually necessary, in fact it is the recognised size for this purpose. The chief reason why a 4-inch main answers so well is that in a pipe of this size which has but few bends and a gradual rise from the boiler to the extremity, there must be necessarily a fair rapid circulation and this fulfils all that a main service is required to do, viz., carry a supply of hot- water to the required points quickly, and the cooled water back to the boiler in an equally short time. The branch services from the mains do not require to have a particularly rapid circulation, for so long as the heated water finds its way into the house, and then out again before it is absolutely cool it suffices, for it passes in with the view of dissipating its heat there, and no great gain is effected by its going in and out too quickly. A circulation can of course be too sluggish, but if the branch return, as it leaves the house, is found to be just warm, the rate of circulation is sufficient. If the mains are carried up the centre of the house in channels, they should be covered with loose gratings (as ex- plained in the last apparatus) so as to benefit by their useful effect, and in such a case allowance may be made for the I2O Warming Buildings by Hot Water. presence of the mains in the house, when calculating the quantity of pipe needed, but it will be remembered that pipes in channels do not radiate more than three-fourths the heat that exposed pipes do (see p. 245). If the mains were carried along the outer side of the back wall, they would then be carried in a brick channel, but a quite new feature is introduced here, as there should in this instance be no heat radiation from the mains themselves. Were this the case the heat so radiated would be wholly lost, without the least beneficial effect, and consequently means have to, or should, be resorted to with the view of conserving the heat within the pipes, and only permitting radiation to take place from the pipes in the houses where the heat fulfils its useful purpose. The conservation of heat is a very interesting and im- portant subject and requires every consideration, but it is not necessary to speak of it at length here, as it will be found fully discussed in Hot Water Supply, p. 329, and Independent Boilers, p. 156. However, some necessary measures may with advantage be spoken of in this place. If the mains are carried along the outer side of the wall, it may be assumed that the earth on that side is upon a level with the house floors, in which instance the pipes will have to be carried underground. This being the case it is usual to make a brick trench or channel, in which the pipes are laid, the channel being afterwards covered with slates and the earth filled in on top of these. This makes the pipes easily accessible if it is desired to expose them, but it is also necessary that the space around the pipes in the channel be filled in with some poor conducting material, otherwise it is just possible that a current or circulation of air may set in through the channel, and this would have a rapid cooling effect upon the pipes, as will be understood. Of course a current or passage of air through the trench could be prevented by making it perfectly air-tight ; but this would be a greater trouble and expense than filling it in, especially as good materials for this purpose are so cheap. Examples of Hot-water Apparatus. 121 Perhaps one of the best materials is dry sand. Silicate cotton is better, but a quantity of this would become expen- sive. Hair or even sawdust would do, but the former is expensive and the latter absorbs moisture. Sand is most commonly used and answers well, and is most easy of applica- tion ; little wood fillets can be placed across the channel here and there for the pipes to rest upon, and this will then permit the sand to get under the pipes also. There need never be any fear in letting these pipes come in contact with wood, as no possible danger can arise, although the Building Act classifies them with flues and other possible causes of a conflagration. The Act, however, is not at all strictly adhered to with hot-water pipes, and there is no occasion for the pre- caution in the way the Act puts it ; but it is just possible that in framing these provisions a thought was given as to what would happen should the apparatus be used, by some extra- ordinary oversight, without any water in it, as in this case the pipes near to the boiler would become of a very high tempera- ture, sufficiently so to ignite any inflammable material that might be in contact with them, in the same way that an over-heated hot-air apparatus would do. Branch Services. In this apparatus, as in the last, the mains after leaving the boiler are carried across the end of the house below the floor-level, in a brick trench covered by a grating. In the first house, which is assumed to be for tropical plants, there is shown a branch of three pipes, two flows, and one return across the back of the house and around as far as the doorway in the division ; also a branch of a similar character across the front of the house and around to the division doorway, and a branch of two pipes carried up the middle beneath the floor in a channel covered by a grating. This is usually ample for a tropical house, but the reader is again reminded that the sufficiency of pipe is determined by calculation as described hereafter (p. 238). The pipes in this house (and throughout the whole ap- paratus) will be 4-inch, and an air-vent would be needed at the highest (i. e. furthest) extremity of each service. 122 Warming Buildings by Hot Water. In the second house, which is reserved for a certain kind of grape and for strawberries, it will be found sufficient to carry the pipes across the front and around each end as far as the division doors, these pipes being connected to the mains by a branch brought across the melon pit as shown ; and in this case it is supposed that the vine roots are at the back of the house near the wall. In this grape-house there are shown four pipes, two flows, and two returns, this particular variety being supposed to require a higher temperature than that in the next house which has a pipe less. It does not, however, fall to the hot-water engineer's lot to decide what temperature a certain variety of fruit requires, this being determined by the gardener, who (it cannot be repeated too often) decides all such questions and dictates generally. To this second house there would need to be a pair of stop valves ; one in the flow, and one in the return, where the pipes pass across the melon pit before they enter the house, and before the branch is increased to four pipes. No valves were mentioned in the tropical house, it being a somewhat disputed question as to whether they are needed there, many gardeners affirming that no regulation is needed in that house, too much heat being impossible, and others having an opposite opinion. If cost is not of primary importance, it is best to have valves in every branch that is of the least importance. In this second house there would need to be the usual air vents at the furthest extremity of each end of the branch, that is the end by each doorway. The third house is supposed to be devoted to grapes of another variety requiring a lower temperature, and possibly a slightly different atmosphere, which renders it difficult for the two varieties to be grown together, and so necessitates a separate house to each. In this case there would possibly be two flows and one return running along the front of the house and up each end to the doorways, the necessary air vent being provided at each of these ends ; but in this case we may suppose that the roots of the vines are differently disposed, and instead of Examples of Hot-water Apparatus. 123 being situated at the back they are brought through the front of the house, the roots themselves being in the earth outside the house, but the stem or trunk being trained through the front of the house into the inside, where the whole of the vine may be said to exist, except the roots. This is a most common practice, the famous vine at Kew being trained in this manner, and it is to be presumed that it gives favourable results, although it interferes somewhat with the disposition of the hot-water pipes. If the house abuts against a wall, it is very properly sup- posed that that side nearest the wall is in least need of heat, or, rather, it loses its heat less quickly ; and if one side of the house only is encircled with pipes, then it should be that side which is most exposed, and this would be the side furthest from the wall. If, however, the vines enter through the front then some remedy has to be sought, and commonly the little problem is solved by putting the pipes along the wall side. This, however, is not the best plan, a better one being to run the pipes along on stands or supports just in front of the vine trunks. Provided the pipes are kept away six inches no harm will ensue from this, and it will give as good results as any way, and certainly better than carrying the pipes along the back wall. In this case stop valves would need to be fixed in the branch flow and return as they cross the melon pit, as explained with the last house. In the next, which may be termed a greenhouse, three pipes two flows and one return across the front only without returning up the ends, usually suffice, these being connected from the main, as before described, with the neces- sary stop-valves and air exits. A greenhouse is generally used for plants, sub-tropical productions, or orange trees, &c. ; but the term greenhouse does not convey any very exact meaning, and consequently the quantity of pipe will be wholly governed by what the gardener intends stocking the house with. The last, and which would be called a cool-house, has two pipes only, carried along the front. This house would 124 Warming Buildings by Hot Water. only be used for wintering trees or hardy plants, or for apricots, tomatoes, &c., that only need to be preserved from frost This house will not require to be in direct communication with the mains, and if the pipes are continued through from the greenhouse this will be found quite satisfac- Fig. 71. tory, but there will have to be an H -piece with valves, just at the division between the houses as Fig. 71 ; this provides a means of closing off or regulating the heat in the house. An air-exit must be provided at the extremity of the two pipes, at which point the apparatus reaches its highest level. The pits along the fronts of the houses, which are generally devoted to melons and cucumbers, are heated by the two main pipes which pass through their whole length, and also by the branch services which cross them. There is, of course, no means of shutting off or regulating the heat of the mains except by the regulation of the fire under the boiler, so that if the pits are at too high a temperature (they are never too cool with two 4-inch pipes through them), recourse is had to the lights or covers, which are opened to a greater or less extent, and so permit the heated air to escape,* and thus reduce the temperature within. These pits are lower than the houses, this being arranged in the construction, which gives every facility for the gentle ascent of the pipes from beginning to end. This apparatus will consist wholly of 4-inch pipes, and it may be said that the work here shown is as much as should ever be put upon one boiler. With any apparatus larger than this two boilers would be desirable, and would give more satisfactory results. In an apparatus such as this the pipes would be supported by brick piers or by iron stands ; brick- work is most usual, although of the two iron has the best * It takes but a very little time to reduce the temperature of a pit, as immediately the cover is shifted the warmed air, by its rarefaction, is dis- placed by cold air, and a change in temperature is directly effected. Examples of Hot-water Apparatus. 125 appearance and as much solidity. In any case, the founda- tion or ground upon which the supports rest must be firm, and have no tendency to sink in the least degree. The next and last apparatus that it is intended to describe (in this chapter) is as Fig. 72, Very little space need be taken up in describing this, as it only differs from the previous ones in having one (or more) houses cut off from the others by reason of a doorway coming in the wall at the point shown, and assuming the boiler has of necessity to be placed at the point here indicated instead of at the end of the houses, as in the other undertakings described. It is not, of course, absolutely necessary that the boiler be at one extremity of the houses to be heated ; in fact, by placing the boiler somewhat centrally, we may occasionally gain a little in convenience. Here again, however, we have to act agreeably to the gardener's planning ; no one is more capable of deciding such questions ; but let it be understood that he is not to be appealed to in everything, the worker must have judgment of his own. At the same time, if there is a gardener on the premises, as there nearly always is, he must be consulted and his wishes carried out. In most cases the gardener superintends the work to a very considerable measure, and everything is done in accordance with his views ; indeed, many gardeners are highly skilled in planning such works. In the arrangement just referred to (Fig. 72) it becomes necessary to have two sets of mains, so to speak ; that is to say, the main flow has to be branched off in two opposite directions immediately it leaves the boiler, or, if desired, two distinct flows could be taken from the boiler direct ; in either case the pipes should be 4-inch, no larger nor smaller becoming any more desirable by either arrangement. In the illustration it is supposed that there is one house on the left of the doorway, and two or more on the right, and that no pits exist in front of the houses. In this case the main to the left may be carried along the outer side of the wall, below the ground level (thus clearing the doorway), 126 Warming Buildings by Hot Water. until it reaches the nearest end of the house, where it passes through the wall inside and is disposed of for heating pur- poses in some one of the various ways already spoken of, or as circumstances or judgment may dictate. The return pipe would be brought back into the side of the boiler, and although the two main flows may be branched from one pipe there is no need whatever for the returns to be joined in any way ; the two returns come one into each side of the boiler, this arrangement giving the most uniform results generally. On the right-hand side of the boiler the main service is shown carried along the outer side of the wall as described on p. 1 20, and from this the branches are taken through the wall into the houses at the points desired ; this has been fully described also. From this last main service there is shown a branch 01 supplementary main service, carried off at right angles near the boiler for the purpose of heating another house which we may suppose is a few yards away. This can be done in the way shown, or supposing this service had its starting point anywhere near the boiler it might be taken direct from the boiler itself. Examples of Hot-water Apparatus. 127 It would be rather necessary to have stop-valves in each pair of main pipes (as well as in the branch pipes where usually needful) with the view of regulating the circulation in each direction. It would also be very necessary to carry and surround these main pipes in the way described (p. 120), as it is supposed that they are wholly underground. And there would need to be the customary air-exits, and other provisions already spoken of fully in the previous works described in this chapter. In the majority of hothouses of any pretension, there should be a pit with water pipes beneath it, to be used for forcing purposes, also in the cultivation of pine-apples, &c. This description of pit must not in any way be confounded with a pit that is a space dug out of the earth : those now referred to usually stand above the level of the hot- house floor- There are three or four arrangements for heating them ; * one being as in Fig. 73, in which the earth rests upon a sort of false bottom full of perforations, the pipes being disposed beneath as shown ; or in another case the pipes are laid within the pit at the bottom, as in Fig. 74, these being first covered Fig. 73- Fig. 74- with clinker, large stones, or broken bricks, and the earth being placed on top of this large material. Sometimes the lower part of the pit contains water, the earth resting on a perforated false bottom above it, as in Fig. 75, the pipes passing through * By adopting hot-water pipes for this work, the use of manure and such heating matters is avoided, with all the consequent inconvenience, irregu- larities, &c. 128 Warming Buildings by Hot Water. the water as shown. The part containing water is usually made of brickwork well cemented to render it water-tight- It will be understood that when first starting the apparatus the water in this tank robs the pipes of heat very rapidly, but once the water is hot it is kept in that condition with very little expenditure of heat. This arrangement is also adopted for heating a tank of water for watering purposes, but in such a case there are usually valves, so that the water does not always circulate through owing to the cooling influence it would have as the water in this tank is drawn off, and replaced with cold. Frequently, therefore, the valves are only opened at such times as the heat can be most spared at noon for instance, when natural warmth is at its highest In Figs. 73 and 74, air pipes would be needed as shown, and in Fig. 75 an Fig. 75- emptying tap and a filling tube are required for the cistern portion as well as an air pipe to the circulating service. The filling tube to this latter pit should be of good size, so as to allow of the free escape of air as the water poured in displaces it, a 3-inch pipe might be used. Three pipes are usually sufficient for these pits, but in Fig. 74 the pipes are sometimes carried round the pit, and a cross pipe used as in Fig. 76. Four-inch or 3-inch pipes are used for these. Examples of Hot-water Apparatus. 129 Fig. 76. A very necessary feature in nearly all glasshouses whether the hottest or the coolest, is what are known as evapo- rating troughs, or trough pipes (see fittings, p. 218). There are three recognised forms of these : one being as Fig. 77, in which the trough is cast on and forms part of the pipe itself; another is as Fig. 78, which is a cast trough laid or resting upon an ordi- nary pipe. Both of these require to be filled by hand periodically. The third sort is an open channel pipe as Fig. 79; this, however, must be fixed in a high position or it will over- flow, and it is hardly worthy of mention, as it is so rarely used. There is no recognised rule as to -the quantity of these pipes to be used in certain houses ; it is usual to put two or three in all houses as they cost but little extra, and the gardener need only use what he thinks proper, and usually Fig. 77. Fig. 78. Fig. 79. this is one of the details of a hot-water apparatus that has to be carried out according to the gardener's wishes in the first instance. The advantage of having a sufficient quantity is that the houses may be used for different purposes at different K 130 Warming Buildings by Hot Water. times. At certain times of the year greater moisture is needed than at others, and again there are times when the troughs are used for evaporating others liquids than plain water. Perhaps the movable trough Fig. 78 is most convenient, and occasion- ally these are made in zinc for temporary purposes. The object of these troughs is to provide a sufficient moist- ness to the air or in technical language to "saturate" the atmosphere. It is a well-known fact that the air at all temperatures holds a certain amount of water in suspension, but it is the least quantity with the lowest temperature, and the greatest quantity with the highest ; air having an increasing capacity for holding water in suspension as the temperature rises. As an instance, we know that the morn- ing dew and the freshness produced to vegetation by moisture disappears gradually as the sun gains in power, and everything has a different appearance at noon to what it had in the early morning. This result is entirely brought about by the transference of moisture from the earth and vegetation to the air. We have exactly the same result in a hothouse which is first filled with air at a low temperature, which, as it becomes heated, and its water-absorptive power increases, abstracts all the moisture it can from the plants, &c., which will suffer in proportion ; but by providing evaporating troughs the air is saturated as the temperature increases. Indeed, it is easy to over-saturate the air so as to have the peculiar dampness and heat that are characteristic with luxuriant tropical vegetation. In the hothouse and for ferns, moisture is in great request, but in a grape-house the air must be dryer, especially at certain times of the year. The gardener can generally judge of these things to the best advantage, but in any case it will be understood that evaporating troughs are provided to fulfil a natural atmospheric law, and that without this precaution plants would be robbed of moisture as well also as the earth in which they grow, and their end would be quickly brought about. When we artificially heat a place, greenhouse, or residence, Examples of Hot-water Apparatus. 1 3 1 we must artificially provide for the additional moisture that the warmed air has increased capacity for, otherwise unnatural results must ensue in a greenhouse as already described, but in a place for habitation by the air becoming unhealthily dry, a most undesirable state of things for bronchial troubles. This subject will be more fully entered into when speaking of stoves and appliances for warming a residence by first warming the air. The necessity of supplying moisture to air as its temperature is raised cannot be too strongly impressed upon the reader, otherwise the air will help itself from any surround- ing objects that have the least particle of moisture about them. Natural heat is perpetually doing this ; it dries our roads, splits and warps our woodwork, withers vegetation, and acts in a thousand ways to this end, solely by reason of the sun causing the air to become of a higher temperature, so that it has to rob everything of moisture to satisfy as much as possible its greater capacity for water. In every illustration of hot-water heating apparatus devoted to horticultural work, the pipes are shown running along the walls hither and thither apparently without regard to situation or as to how they may affect any roots (grape, peach, apricot, roses, &c.) that have to be carried and supported against the walls or elsewhere. It is impossible to suppose that the roots can conveniently be disposed to suit the pipes, consequently, recourse must be had to the gardener to settle this question also. It is not necessary to entirely alter the plan of the pipes on this account, but arrangements must be made that the pipes do not come in anything like contact with the stems or trunks of the plants. Of course all this should be settled before commencing the undertaking, as whether the work is done to estimate, or con- tract, or otherwise, everything is planned out and arranged beforehand ; at the same time it is possible for such a detail as this to be overlooked. The average gardener will permit of pipes coming as close as 6 inches to grape roots, if it is necessary, and if the pipes are kept, say, 4 inches below the lattice that supports pots, it will suffice ; but it is not usually K 2 132 Warming Buildings by Hot Water. permissible to have them closer than this. The general plan is, as already shown, to have the roots on the wall side of the house, and the pipes along the opposite side, but it fre- quently happens that a vine root is outside the house and the trunk trained to enter close to the ground, and then it becomes necessary to dispose the pipes to clear this. If a quantity of shrubs are growing close to the walls it is sometimes con- venient to carry the pipes alongside the footway as at Fig. 69 (page 114). ( 133 ) CHAPTER VIII. BOILERS. Heating surface, direct and indirect Horizontal and vertical Different resulting effects due to different conditions of the fuel Hood's standard of heating surface areas and its application Boiler-makers' lists, and the deduction necessary to be made from them Flue surface and its value Action of flames and heated gases in flues Fletcher's heat collectors ^Suggested new standard value of different heating surfaces Small and large waterways Deposit, its effect and removal Cast and wrought boilers Area of furnace bars Hood's table, and necessary additions thereto Independent boilers and fixing Gas boilers Coke boilers, the " Star," " Coil," " Finsbury," " Horse-shoe," " Ivanhoe," " Dome-top," " Independent terminal end Saddle," " Challenge," and " Viaduct." IT is only possible within the limits of this chapter to deal with a representative selection of boilers, showing some of the leading features, and illustrating the peculiarities of those that have gained public favour and for which there is a fairly general demand. It is proposed to commence with the most simple forms, viz., those which are heated by oil or a small Bunsen burner, and from these to proceed by regular degrees to boilers capable of fulfilling the greatest demand. There is no reason why the small heaters, which combine boiler and radi- ating pipes in the one article, should be neglected ; they are of considerable use and fulfil a greatly felt want for amateur greenhouse work, as they are capable not only of keeping the frost out, but also of keeping the air at quite a mild tempera- ture, and were they better known (for the few makers of these articles keep in the background most strangely) they would meet with a rather large demand and sale. Before proceeding with the actual description of the various 134 Warming Buildings by Hot Water. boilers it is necessary to refer to some of the special features that a good boiler should have, and also to review Hood's decisions in this direction. The first question to be con- sidered is what qualities constitute a good boiler, that is an efficient boiler, one that gives the best results for a given size or space occupied, working under normal conditions and with- out undue expenditure of fuel, labour, &c. One would be led to think that this question had never yet been satisfactorily answered judging by the number of differ- ent boilers that have been designed from time to time. Even now new forms are continually being introduced at fairly regular periods, but it is evident that the old pattern " saddle " boiler still retains favour as vast numbers of these are at this moment being made and used about 10 times as many as any other shape, and nearly every new one bears some resem- blance to the saddle ; there - Fi g- 8o - fore, for the study of what constitutes a good boiler we may take the saddle Fig. 80 as an example. It can be readily under- stood that the boiler surface immediately facing the fire or in direct contact with the glowing fuel is at the greatest advantage in heat absorption, particularly that part of the boiler which is directly over the fire, as with a mass of coal confined to a certain space as it is in a boiler, it will be found that the greatest effect is by the heat that is radiated from the top of the fire, assuming the fuel to be in an incan- descent state. In any case it may be accepted as a recog- nised fact and rule that the part of the boiler directly facing or in contact with the fuel, absorbs heat at a much greater speed than any flue surface, in a proportion that will be deter- mined directly. As a rule it is considered that the area of boiler surface immediately over the fire is of greater value than that which Boilers. 135 forms the sides or bounds the fire, in a proportion of about three to two. Hood has fixed the ratio at this, and theo- retically it may be accepted, though not strictly exact. It is, however, desirable (to prevent an error being fallen into here, for these results are only based upon the supposition that the fire is in a similar state of combustion at sides and at top), to adopt a more homely way of arriving at the con- clusion. Let us suppose that we have a vessel of water which has a side surface of the same area as the bottom (a cube for instance) ; also let it be supposed that we have a fire in an incandescent state with the top surface and the front surface in an equally glowing state. Now if we boil the water by placing the vessel on top, we shall get the result aimed at in a much less time than if we put the side of the vessel against the front of the fire. This is what it is intended to convey when we read that the boiler surface over the fire is of a greater value than that which bounds or comes opposite the side of the fire. It may now be seen where the error may be made, viz., in assuming the top of the fire to be always in a glowing state. Now if the gardener or attendant is skilled as a stoker (as most of them are), and if he take the trouble to stoke the fire regularly, by use of the dumb-plate, each charge of fuel is coked and prepared before it is put upon the active part of the fire, and its bright and glowing nature is little interfered with. But this again is merely an assumed state of things, for unless the apparatus is on a great scale necessitating the almost constant employment of a fireman, there is very little of the skilled stoking done, and neither is it expected nowa- days, for in most of the new boilers introduced a feature is made in economising time in stoking so that the fire can be charged and need no attention for several hours thus giving opportunity for other useful work to be done in the time that might otherwise have been spent in stoking. It will also be understood that during the night, with any description of boiler, the fire has to be made up and cannot have constant attention, and at night the greatest heat is needed. 136 Warming Buildings by Hot Water. The object of this explanation is to show that only under rather special and favourable circumstances is the top of the fire in a bright and glowing condition, and to arrive at the theoretical power of a boiler we must not be too ready to give a much higher value to the surface over the fire as against the surface at the sides of the fire, especially as the latter has actual contact with the fuel, which the former has not. Again referring to the kettle illustration we can see that if the front of the fire was of red hot fuel and the top of the fire was black with fuel newly put on, it is just possible that the kettle placed in front would heat the more quickly. Under these circumstances the boiler surface immediately around the fire, whether at the sides or above, should be estimated to give about equal results in the aggregate. In every description of boiler, whether new or old, there is one important feature that has to be studied in judging its effectiveness, namely, whether it has every possible portion of its surface area devoted to direct or primary heating, that is surface coming directly opposite the fire, for should any portion of this surface be sacrificed to make flues, unless the flue surface so gained is three or four times as large as the direct heating surface sacrificed, the result will be lessened and not increased. Boilers have, and may have, flues by all means, but flue surface being of so much less value than direct heating surface (in a proportion that will be directly investigated) it has never been found advantageous to lessen the latter for the purpose of increasing the flue room. This undoubtedly accounts for the favour that the saddle boiler has so long enjoyed, its shape making it so capable of benefiting by the heat, forming as it does an envelope to the fire, and conducing to a freer circulation than we get from a flat top. Hood points out the advantage gained by the use of an old pattern boiler (which existed some years ago but is no longer to be found) which much resembled a large basin inverted over a fire, and having a flow pipe proceed- ing from the apex. With this very excellent results were obtained, but it could not conveniently have flues carried Boilers. 137 around it and was not suited for any large purposes, but it serves to illustrate the advantage of direct heating surface. We have now, however, boilers that bound the fire on all sides as the one just described did, but not necessarily circular, and they have the advantage of being adapted for flues being Fig. 81. Fig. 82. carried around them (so as to heat the outside surface as well as the inside, as will be explained directly). One is the saddle boiler but with water-way front and back ends, Fig. 8 1 ; another is a circular boiler, Fig. 82, which bears several names and will be described in a later page. There are also some other designs that fulfil this object, in fact, makers are generally alive to the importance of getting the utmost direct heating surface and making boilers to envelop the fire so as to retain and benefit by the radiant heat to the utmost extent. Flue surface is nearly always- easy of attainment and is of no very great value at the best, except that part where the flame has impact immediately it leaves the fire : the tail of the flame and heated products after having travelled the length of the boiler once, do but a very limited amount of good. (See flame contact, p. 142). 138 Warming Buildings by Hot Water. This now brings us to consider and discuss one of the most important features in Hood's book, and which is brought to the notice of every engineer when purchasing boilers for hot water work : this is the question as to what area of heating surface a boiler should have to render a certain amount of service, or in other words, what amount of pipe or radiating surface can be effectually worked from a superficial (square) foot of boiler surface. Hood, in his painstaking manner, went to great trouble and apparently took note of many results before arriving at and fixing his data, and to the best of every one's judgment, he succeeded in getting accurate figures, but unfortunately figures that could only be expected in results under the most favoured conditions as to surroundings, con- struction, quality of fuel, good stoking, external temperature, &c. This is the more to be regretted as practically every boiler maker has adopted his standard, with very unfortunate results. This standard which was set up, was that one square foot of boiler surface subject to a direct heat was capable of heat- ing 50 feet of 4-inch pipe, or if any flue or indirect heating surface entered into the calculation then three times the area was to be allowed, that is three square feet of indirect heating surface was to be allowed for 50 feet of 4-inch pipe ; this is the standard adopted by the majority of boiler makers, but they are not free from fault in adopting it, as Hood clearly points out the favourable circumstances, and strange to say the boiler makers have overlooked an important paragraph affecting this matter, in which Hood says, "A very good proportion, suitable for nearly every purpose is to allow about one foot of boiler surface (direct heating) to about 40 superficial feet * of pipe or other radiating surface, or about I -fifth more boiler surface than the preceding Table states." * The word " superficial " is correctly used as the circumference of a 4-inch pipe is so nearly 1 2 inches, that every foot in length of this sized pipe may be called a superficial foot in this work. Boilers. 139 This very clearly shows Hood's feeling in the matter, viz., his disbelief in his original standard acting up to the results given if worked under common conditions which differ so greatly from the conditions that attend an experi- ment. But, as before mentioned, this last paragraph and the detail leading up to it have been quite overlooked by those who have adopted his data and held him responsible for their figures. Of course the makers and users of boilers quickly became aware of the unsatisfactory results that attended the adoption of this standard when the articles in question were used in the way that many boilers are used, which shows a great desire to economise labour to the prejudice of good results, consequently a method of obviating this difficulty had to be discovered, and the general rule adopted is to adhere to Hood's data, but with a brief preface as follows : " The heating powers given in this price list of boilers are based on Hood's standard work on hot-water heating, viz., 50 feet of 4-inch pipe for each foot of direct heating surface in boiler and one-third this quantity for indirect or flue surface ; but for ordinary actual work the heating powers in the list should be reduced 30 per cent, thus a boiler estimated to heat 1000 feet should only be put to 700 feet to do its work well and economically." The standard list that this refers to is as follows : Wrought Welded PLAIN SADDLE BOILERS, with from 2-inch to 3-inch Waterways, according to size. T w TT Approx. Heating Power, 4-inch Pipe. 24 x 12 x 12 300 feet. 30 x 14 x 14 425 36 x 16 x 16 600 42 x 18 x 18 800 48 X 21 X 21 1000 54 x 24 x 21 1300 60 X 24 X 21 I50O This list is abbreviated for sake of space ; there are many intermediate and some smaller sizes and of course there are 1 40 Warming Buildings by Hot Water. many other lists that apply to other forms of boilers, but all calculated results are based upon Hood's original data, which require the deduction of fully 30 per cent, to arrive at actual practical value under ordinary conditions. Now in actual practice, especially if first cost is not of great importance, it is desirable to make even a greater deduction than this so as to permit of economy in stoking and attention, and to provide for the advent of any unusual con- dition, in weather, surroundings, or attention, that may occa- sionally manifest itself. This greater deduction from the standard list particularly applies to boilers that have a top feeder as it is termed, like Fig. 83, which boiler is arranged Fig. 83. particularly for charging from the top and not from the front, consequently the top or most valuable surface of the fire is not usually in a bright state. This arrangement very readily permits of putting a heavy charge of fuel in at one time and thus less attention is required. Another ques- tion to be discussed respecting the standard set up is as to the value of flue surface, relative to that surface which comes next to the fire and is heated direct. Hood has fixed this at one-third, or three superficial feet of flue surface, to give the same results as one foot of Boilers. 141 direct heating surface. Here again there is a regrettable difference between experimental and practical results, and again is it necessary to hold the heating surface at a lower value than the proportion set down. In the first place, we have to consider that with the majority of boilers (the saddle shape as an instance) we cannot get any flue surface beneath the water space, the flues have necessarily to be carried along the outer sides and across the top of the boiler. It has already been shown what a much lower value vertical or side-heating surface has, compared with horizontal flat surface with the source of heat beneath it (the condition of the fire or flame being equal in each case), so that when we consider what value can be given to heating surface that is beneath the source of heat, as it is when any flue is carried over the top of a boiler, we shall find it is practically nil, of no use whatever, or at least bearing only the most trifling comparison to the direct heating surface that we get in the fire-box. We have also to consider that flue surfaces quickly get dirty when coal fuel is used, and even when nothing but coke is burnt there is a deposit of dirt on flat surfaces, such as the top of the boiler ; and whether the dirt be soot or of a dusty nature, it requires but a thin coat to materially obstruct the absorption of heat, as the dirt deposited in flues is always of a low conductive power. This goes to lessen the value of flue surface unless the flues were swept daily, which is not done. Lastly, there is a phenomenon exhibited by flame (supposing coal to form part or the whole of the fuel used), which has been but little understood or noticed. In the first place, any one having had experience with flues of any description will have noticed that flames and other heated products exhibit a strong disinclination to come in contact with surfaces of any description ; and should the flues be too large, the flame, &c., in its passage from the fire to the chimney will not do so much useful work as it might do otherwise. The objectionable feature in this is that the flame gives off but little heat by radiation, and may be said to heat by contact only, consequently the flues should be sufficiently 142 Warming Buildings by Hot Water. small to bring about this result, at the same time not so small as to become quickly stopped by soot, or to choke the draught (passage of air, &c.). Flues to a furnace burning coke only might be a trifle smaller than those connected with a coal fire, but this will be dealt with in its proper place. The next question, affecting the comparative value of flue surface, is a somewhat peculiar one, involving the discussion of a phenomenon that Thomas Fletcher, the well-known scientist and gas engineer, treated in a paper read before the meeting of the Gas Institute, London, June 9th, 1886, entitled, "Flame Contact : a new departure in water heating." This is the fact that flames under ordinary conditions do not come in contact with a vessel containing water at all ; whether the water is hot or cold, or whatever the vessel be made of, there will exist a thin film of air or space between the flame and the vessel so long as the vessel contains water, or, in other words, so long as the metal of the vessel is prevented from reaching a higher temperature than about 212. This film or stratum of air does not exist when the flame is acting upon some surface that is at a much higher temperature, it only manifests itself when some cooling influence exists, as the presence of water, which even at boiling-point seems to have the repelling effect upon the flame as explained. This peculiar action was fully explained by Fletcher in the paper referred to, and it goes to show that, as applied to water heating, ordi- nary flue surface is still further at a discount. It is worthy of note that the remedy that Fletcher suggests for this state of things takes the form of a suggestion made by Hood, but the peculiarity is that Fl S- 8 4- the two suggestions, although they would bring about the same results, originate from different ideas. Hood's proposition was the addition of gills or projecting flanges outside and beneath the boiler, as Fig. 84, with the view of increasing the area of the heating surface to this extent. From results obtained at that time it was decided that water covering a certain area of boiler surface was capable of taking Boilers. 143 up or absorbing heat 2 6 times as fast as it could be received by the same given area from the fire, and the addition of these flanges provided this extra heat-receiving surface without any trouble being taken to increase the water-surface. This was exceedingly successful with cast boilers, but its application to wrought boilers has never been successfully carried out, although it is worthy of serious attention from boiler-makers.* It would not be necessary to adopt gills in particular ; any mode of adding to the heat-collecting surface will do, but it should consist of solid parts, for the reason that will be made clear from Fletcher's investigations. When Fletcher discovered that a metal surface at 212 or less practically repelled flame from contact with it (under ordinary conditions), he set to work to devise a means of obviating what in his practical mind was an objectionable feature, and opposed to the best results. His experiments showed him that a metal surface that could be raised to a higher temperature readily received flame contact, so he devised a vessel having a large number of solid projections upon the bottom, as Fig. 85, and the differ- ence in results in transference of heat from Fi S- 8 5- the flame to the water was most remark- able. In a small vessel of the ordinary character with a flat bottom, 40 ounces of water was boiled in three minutes fifty seconds, whereas with a similar sized vessel, but with the solid studs or rods on the bottom, 40 ounces of water was boiled over the same flame in one minute fifty seconds.! We see from this * Corrugated boilers have been introduced for the generation of steam, but these increase the water surface as well as the heat receiving surface, which is not necessary. But with steam boilers the corrugations are an element of safety, if undue pressure is exerted, as they give to the strain instead of bursting. t See ' Flame Contact, a new departure in water heating ; ' by Thos. Fletcher, F.C.S., obtainable from T. Fletcher & Co., gas engineers, War- rington. 144 Warming Buildings by Hot Water. that solid projections (whether studs or plates) from a boiler have the important advantage of adding to the heat- receiving surface whether direct or from flame, as aimed at by Hood, and secondly, they have the very important ad- vantage of achieving the excellent results discovered by Fletcher, of securing the actual, the utmost real benefit of flame contact. This latter feature not only applies to flame but to heated gases (products of combustion, &c.) also ; and it is effectual when coke fuel is used, from which we get no flame (except the small blue flames from carbonic monoxide). It will be understood that the success lies in the fact that the extremity of the rods or studs (which in this case were i Jin. long) are too far removed from the water to have their tem- perature kept down to anything like as low as 212 (after having once become heated) ; yet by the rapid power of con- duction possessed by iron or copper, they are all the time transferring heat from their highly heated extremities to the interior of the vessel. This brings us to consider whether the flue or indirect heating surface that we obtain with an ordinary saddle boiler fixed in an ordinary way is of the value put to it, viz., three superficial feet for 50 feet of 4-inch pipe ; and in the writer's opinion it is not, far from it. If a new standard could be introduced * it would be found that for ordinary purposes, that is general horticultural and other purposes, in which certain troublesome conditions occa- sionally introduce themselves, but which in this case would * This is somewhat improbable, as in the adoption of a new standard, however necessary it may be, the makers of boilers would have their interests prejudiced, as their goods would be apparently raised in price. A saddle boiler for 500 feet of 4-inch pipe, now listed at 5/. Js. 6d., would, by the adoption of this proposed standard, be raised to about 8/. los. ; but, in the latter case, the 500 feet would represent the work that could be actually performed by the boiler under the most ordinary and common conditions with quite satisfactory results ; whereas at present, when a boiler is required to heat 500 feet of pipe, the user has of neces- sity to purchase one that the maker's list says will heat 750 feet, but in reality will not. Boilers. '45 One square foot to 30 superficial feet of radiating surface, not require special consideration, this standard would be as follows : Suggested New Standard* DIRECT HEATING SURFACE. Whether the boiler requires stoking in the ordinary way, or is arranged to take a charge of coal to last several hours. These figures are for an average square foot of heating surface, that is to say, not necessarily that part which comes nearest to the glowing mass of fuel, but to all the surface that receives direct heat. INDIRECT HEATING SURFACE. For primary flue surf ace, that is, for flues that receive the flame and heat directly after it leaves the fire-box, and which flues have, as a matter of course, a greater value than secondary or return flues next in order : If the flue is a flat or \ One square foot to 12 horizontal one, and the flame S superficial feet of radiating passes beneath it . . . . j surface. If the flue is a vertical | One square foot to 10 one, and the flame, &c,, acts V superficial feet of radiating upon the one side of it . . J surface. For secondary or return flue surface, that is, flues which receive the flame or heat directly it leaves the primary flues just alluded to : If the flue is a flat or \ One square foot to 8 horizontal one, and the heat \ superficial feet of radiating passes beneath it . . . . J surface. If the flue is a vertical | One square foot to 6 one, and the heat acts upon ) superficial feet of radiating the one side of it . . . . J surface. * This standard could only be held to apply to boilers provided with a correct area of furnace bars, as will be described directly. L 146 Warming Buildings by Hot Water. No allowance has been made for horizontal flues which have the heat passing over them, such flues are usually as near as possible valueless. The question of third and fourth flues has also been ignored ; these are of value when circumstances permit their use, and allowance could be made in proportion to the foregoing figures ; but for these third and fourth flues, and also the horizontal flues with heat passing over them, to do any efficient duty, the draught must be stronger than is usual in horticultural work of the ordinary character, as chimneys of even moderate height are not permissible in the gardens attached to a residence. In business establishments, or with professional growers, the unsightliness of a taller chimney is overlooked, a more powerful draught is at once introduced, and in this case the flues just mentioned, although still of the least value, add to the total efficiency, and all heat- ing surfaces bear a greater value consequent upon the greater consumption of fuel and heat evolved. The standard just suggested is merely to take the place of the impracticable one that is used by all boiler makers, for boilers of the ordinary character and which constitute the greatest number in demand. It is of course unreasonable to still retain such fictitious figures, especially as even at this day it leads to many unfortunate errors being made. Builders and others who only occasionally use the articles, are not all aware of the deduction to be made, and as the makers who mention it in their catalogues only mention it once, it is easily overlooked. Many makers would readily alter their figures, but of course the alteration must be universal, or some would appear to be charging very differently to others, higher or lower, as the alteration had been made or not. It may be held that the standard now suggested is too low, but such is not the case ; it will only be found to give really satisfactory results. It is quite of common occurrence for boiler users to adopt half Hood's figures, that is, purchase a 1000 feet boiler for 500 feet of 4- inch pipe, to ensure efficiency with economy and to allow for possible irregularities in stoking or conditions, and presuming first cost is not all- Boilers. important. If the standard just suggested errs in the least degree (for it is quite impossible to arrive at exact figures, conditions and other things never being twice alike) it errs towards efficiency. If it were otherwise it would lead to per- petual allowances being made for trifling circumstances. Apart from this, every boiler user will endorse the writer's opinion that a boiler should always be capable of over-doing its work if pressed a little. A boiler that answers quickly to any attention that is paid to the furnace gives the utmost pleasure to the user. A boiler should be thoroughly effective when the inclemency of the weather is inclined to tax its capabilities, otherwise the work of months may be instantly ruined or thrown back. Any boiler will heat a place in mild weather, or it might suffice in the bitter weather if it had constant attention, but no such risks should be run, especially as the remedy is gained with two or three extra inches in the length or width of the boiler. The waterway in a boiler varies with its size the smallest being 2-inch (none, however small, should be less than this), the larger sizes being 3-inch and 4-inch; occasionally boilers are made with still larger waterways, but these may be considered rather as exceptions to the rule. There is no gain in having an unusually large waterway, but the 4-inch size is worthy of recommendation for the large and also for moderate-sized boilers. In the first place, for a given sized direct heating surface (the part which surrounds the fire, and which is commonly called the inside) we get a greater indirect or flue surface with a 4-inch than we do with a 3-inch waterway, and by this means the efficiency of the boiler is increased, although but very little. Some makers value the heating properties of a 4-inch waterway boiler at one- eighth more * than a 3-inch, but this is most unreasonable ; * An aggregate eighth, that is, giving to the little extra flue surface the credit of adding one-eighth to the total value of the boiler, whereas it does not add one-eighth to the flue or indirect heating surface alone. A letter upon this subject addressed to the writer by a hot-water engineer of some note in London reads as follows : " The larger water- way does certainly increase the power of the boiler, because of the L 2 1 48 Warming Buildings by Hot Water. the difference in actual results is hardly worth taking into consideration in practice, unless the boiler was a really large one. But of course boiler makers are quite justified in showing some greater heating efficiency in their lists, as an increased indirect surface does exist. The chief advantage of a 4-inch waterway is its less liability to become choked with deposit (sedimentary dirt, foreign matter, or incrusted lime deposit) than with a narrower size. This is worthy of consideration, as there is every necessity to prepare for this trouble, for in the best constructed appa- ratus in which care is used to exclude dirt, a sediment always accumulates in time, and in an apparatus that is probably tended by a boy who charges it with pond or ditch water, a large amount of mud-like deposit quickly accumulates. In every boiler there should be provision made for cleaning out any deposit that may accumulate, whether it be dirt or incrustation due to hard water. It is customary for this pur- pose to put what are called mud holes at a low point in each side of the boiler. These are merely fair-sized holes, drilled and secured by a screw plug, and provision is made in the brick setting for easy access and their removal when necessary. Very commonly, and in fact usually, a pipe is brought from these holes straight through the brickwork in front of the boiler, these pipes being plugged at the ends ; this makes the periodical flushing (to remove loose deposit or dirt) a simple matter, as a cane can easily be pushed in to disturb the dirt. The accumulation of incrusted lime deposit is a more serious matter. This only occurs when what is known as " hard " water is used ; this water containing lime in solution, which is precipitated and adheres to surfaces most tenaciously when the water is heated.* This is more difficult of removal than the larger area of outside surface, but in my opinion not sufficiently to be worth taking into calculation. ... I have found it very unsafe to take the figures that appear in boilermakers' lists. ... I always deduct one-third from the work values that appear in most catalogues." * The heating process throws down the lime, and softens the water. It is the same deposit or "fur" that we get in the tea-kettle when hard water is used. Boilers. 1 49 deposit of dirt it cannot be flushed out. This question is more fully treated under hot- water supply (p. 333), and the causes, remedies, &c., are fully dealt with there ; but it should be mentioned here that, although the incrusted deposit is the most difficult to contend with, it fortunately shows itself very little in heating work, as firstly, it is the common practice to use soft water (rain water from ditches or ponds, or collect- ing tubs), which has no appreciable amount of lime in it ; and secondly, if hard water is used it is not often changed, not more than a gallon or so being evaporated in a week or more (according to the size of apparatus), and as a given quantity of water has only a certain (very small) amount of lime in solution, the deposit is very trifling and does not become noticeable for a very considerable time. It is only in apparatuses that have the water continually drawn from them (as in a domestic hot-water supply apparatus, or in a kettle) that we get the thick incrusted accumulations. If, however, a heating apparatus is fed by a cistern with a ball valve, this usually means that the water is supplied from a water company's mains. Should this water be hard, as is nearly always the case in the southern half of England, the incrusted lime deposit must be expected more or less quickly. This will be governed by (i) the percentage of lime in the water, (2) the quantity of water evaporated, and (3) whether any water is drawn from the apparatus for watering pur- Flg> 86 - poses. This latter prac- tice greatly aggravates the trouble. It has just been mentioned that what are technically termed " mudholes " should be provided with every boiler, these holes being situated one on each side, in front of the boiler near the bottom, and generally having a pipe screwed into each of them, as Fig. 86, so as to come through the brickwork, which has to be erected in front of the boiler 150 Warming Buildings by Hot Water. (unless it is one of an independent character). The object in having these holes situated in the position shown is that any accumulated deposit, whether hard or soft, can be removed from the surface of the boiler where it is most likely to cause injury, which is at the part pointed to by arrows in the illustration, and where nearly every fracture takes place. This part can be reached with a rod instrument inserted from the front, through the holes referred to. If these bottom angles are kept clear the boiler should do many years' good service. If the boiler is one having a return pipe brought in upon one side only, it is the other side the part of the boiler furthest from the return pipe where the greatest soft deposit* will be found. Again refer- ring to the question of large or small waterways to boilers, it may be considered that for medium and large boilers 4-inch is a desirable size, and no gain will be effected by using larger. An increased bulk of water is a disadvantage unless it was desired to secure a store of water, in which case it would be better to use a tank as a reservoir, f About the only case in which a store of hot water is useful is when an equable temperature is particularly needed with uncertain stoking. In this case a tank of good size might be put in connection with the apparatus, and provided it was well covered with some poor conductor of heat, it would provide a storage of hot water that would be circulated through the pipes and give up heat for some little time after the fire was out. This is a most unusual requirement, but nevertheless, it may occasionally be resorted to, and is found useful in works of a peculiar or special nature. It will be found in the description of boilers that follows this, that some are made of a very shallow shape, expressly for use with what is called " shallow drainage," that is, situa- tions where water is met with (when excavating for the boiler * The term soft deposit is used as embracing all matters of a dirt-like nature. The hard deposit (carbonate or sulphate) of lime is of a stony character. t A tank is sometimes of service when a pipe has to be carried below the level of the boiler, as described on p. 81. Boilers. 151 pit) very near to the surface of the ground, so that a deep boiler pit is out of the question. Even those that may be con- creted round, or lined with iron, cannot be kept free from water if they are deeper than the point that the surface water rises to, and the pits cannot under this circumstance be so readily drained, as every pit should be, if possible, for various reasons. Boilers are made of cast iron, wrought iron, and copper. The former and the latter are but seldom used, especially the latter, by reason of its costliness. Cast iron is used to some extent with small boilers, chiefly of the independent kind, and is found fairly satisfactory, as they are but seldom subjected to heavy usage. This material is also used in some kinds of boilers of a larger size, as will be seen presently, and might be used to a much greater extent if the right kind of admix- ture of metal were used to produce a tough casting * which would not only withstand rather violent handling, but would last a long time without fracture from ordinary wear and tear. Wrought iron is the material nearly always used for boilers 'of moderate and large size, both of the independent and other kinds. The plates are most commonly jointed by a weld, this being cheaper than riveting, and is satisfactory in use ; * To illustrate the difference in the natures of various brands of cast iron, the writer once saw a cupola man in a foundry breaking pigs of what is known as " white iron." A pig would break with one very moderate blow of a sledge hammer, and not only break, but fly in four or five pieces ; whereas a pig of superior iron, noted for its toughness and softness, was subjected to about fifteen to twenty of the heaviest blows with the same hammer, and, after all, had to be dropped across a block of iron set edgeways before it came into two pieces ; then, instead of a clean break, as is obtained with white iron, the break bore the appearance of being torn asunder a never-failing sign of excellence of quality. This foundry was devoted to the manufacture of cooking ranges, and the castings, if struck at the edge, would burr over, instead of having a piece fly off, as is expected, as a matter of course, with anything made of cast iron. A casting of good quality should not break even if dropped a moderate distance on to a stone surface, yet the average of castings met with have to be handled like glass. 152 Warming Buildings by Hot Water. but with large sizes, riveted joints are resorted to. All boiler- makers' lists show two thicknesses of plate, viz., T V-mch and flinch, the price differing about 20 per cent. The latter thickness is always recommended, and if cost is not of primary importance it should be used ; but it has often occurred to the writer that if a boiler of each quality could work side by side under exactly similar conditions it is doubtful whether the f -inch would give 20 per cent, more service than the -^--inch. We have to remember that many, in fact almost the majority of boilers, do not fail from actual wear, but become fractured by some accidental cause (accumulation of deposit, &c.), this being obvious in a great measure by the fact that the fracture nearly always takes place as shown in Fig. 86 (page 149). But it is not intended to recommend the thinner plate, as in good work it would be best to use the thicker quality, although the advantage gained may not be quite proportionate. There is another good reason for using f-inch plates, viz. that when the apparatus is one that extends some distance in a vertical direction, it necessarily brings a considerable strain to bear upon the boiler which is at the lowest point. However, this happens but rarely in horticultural works, and the reader is therefore referred to p. 255, where the subject is fully considered, as it need be, in heating of build- ings and high places. The last, but important subjects to be considered (before dealing with the boilers themselves) are, the area of furnace bars needed for certain boilers, and some general features that should be studied in connection with furnace construction. With some of the boilers that are described later, there will be shown methods of setting them, particularly with the ordinary saddle boiler which so greatly resembles many of the more recent patterns, and is a guide in a great measure to the treatment of these others, so far as setting is concerned ; but with all of these there is a certain recognised rule to be followed in deciding the size of the furnace bars. This rule requires almost as much consideration in practice as that one which governs the selection of the boiler itself. Boilers. 153 Hood very correctly points out that the area of furnace bars should bear a distinct and fixed relation to the area of radiating surface, without any material consideration as to the size of the boiler. This, however, must be allowed a little latitude occasionally, as although with a certain area of fire- bars we can consume only a certain quantity of coal in a given time, whether the boiler be small or large (draught and other conditions being equal), yet with a larger boiler we should be getting better results generally, but under all ordinary conditions a fixed rule can be adhered to with a certainty of good results.* Occasionally a greater area is desirable when a greater consumption of fuel is required, but the special nature of the circumstances will decide what proportionate extra area is needed. If it is desired to get a greater heat by a proportionately greater consumption of fuel, this is better effected by increas- ing the area of furnace bars than by using ordinary sized furnace bars and increasing the draught. Of course, a certain amount of fuel will yield only a certain amount of heat, but to economically utilise the heat evolved is, as just stated, better effected by having a larger area of fire-bars with a normal draught than a small set of bars with a stronger or forced draught, for it has been a recognised rule always that if the fuel can be had in a moderately thin layer spread over a good surface, burning brightly (as it would do under such conditions), better results will be attained than if we have to confine the fuel to a smaller area in a mass, with a forced draught. Another, though minor, objection to a forced draught is that it necessitates more attention being given, and it also causes undue wear and tear. Hood's rule, or table, which is recognised and found correct at the present day, is as follows. * If in ordering a boiler the maker is asked to supply the fittings, he will send a grating or furnace bars of a suitable area, together with the furnace doors, dumb plate, &c., all of a correct size for the work the boiler is supposed to do. This is a convenience if the purchaser desires to avoid the trouble of calculating, &c. 154 Warming Buildings by Hot Water. HOOD'S TABLE FOR CALCULATING THE AREA OF FURNACE BARS NEEDED FOR CERTAIN LENGTHS OF PIPE. Area of Bar, 75 square inches will supply 150 200 300 ioo 200 266 400 150 300 400 600 200 400 533 800 250 500 666 1000 300 600 800 1200 400 800 1066 1600 500 ICOO J333 2000 It will be seen that, although the table is extended to eight lines, it really says that for all general purposes in which small to fairly large sized boilers are used, it can be laid down that each ioo feet of radiating surface should be allowed 50 square inches of furnace bars. Now Hood's table can only be applied to plain saddle boilers, as immediately we introduce a boiler with flue ways or cross tubes, &c., in it, we increase its power with regard to the radiating surface it can deal with, but we may not increase the size of the furnace or the lower part of the boiler in the least : and although in an instance like this the radiating surface capable of being dealt with is greater than with a plain saddle boiler, there is no need to increase the area of furnace bars proportionately, or in fact, at all. When Hood fixed his standard of 50 square inches of fire-bars for ioo superficial feet of radiating surface, boilers with check ends, chambered flues, cross tubes, &c., were little known, or rather were accorded but little favour, but now they have a considerable demand, particularly where space is limited; and where we can get increased surface, particu- larly direct heating surface, and increased results for a given amount of fuel, without increased size, it is, generally speaking, a desirable end attained. In practice it is found that, adopting Hood's calculation (which is strictly practical) for saddle boilers, a list, such as the following, gives accurate results under ordinary conditions, and with an ordinary draught. Boilers. 155 The areas mentioned in the following table include the bars and the spaces between the bars. The table may be varied to suit special requirements, and no noticeable trouble is experienced if under ordinary circumstances the area is increased a little beyond the proportions given, but it is by no means ever desirable to decrease the areas suggested. An increased area with a low draught is better than the reverse. For every 100 superficial feet of radiating surface allow : TABLE SHOWING THE AREA OF FURNACE BARS FOR VARIOUS KINDS OF BOILERS AT PRESENT IN USE. Square inches. With a plain boiler 50 saddle boiler having one check or waterway end 45 two waterway ends (front and back) .. .. 40 a tubular flue (as Fig. 125) 40 two tubular flues . . . . 38 With saddle boilers such as Figs. 127 and 128, which have check ends and tubular flues 35 If a boiler is fitted with a cross tube (as Fig. 102) the area of furnace bars can be reduced below the above figures for every 100 feet of radiating sur- face 5 to 10 Keith's boilers are worked with an average of about 20 square inches of furnace bars per 100 feet of radiating surface. This low allowance is sufficient, the direct heating surface being so extensive within a small area. From this table it will be seen that a plain saddle boiler, estimated to heat say 800 superficial feet of radiating surface, should have furnace bars of an area of 400 inches ; but if this boiler were fitted with an oval cross (waterway) tube, it would be capable of dealing with 1000 feet of radiating surface, but the area of fire-bars need not exceed the measurements above given. In dealing with the following representative variety of boilers, no particular distinction will be made between those used for horticultural works and those that may be better adapted for heating buildings. Up to the present we have 156 Warming Buildings by Hot Water. almost exclusively dealt with horticultural undertakings, but there is no need to have more than the one general description of boilers, and therefore this chapter must be made to apply to the other articles upon low-pressure heating which follow. INDEPENDENT BOILERS. These boilers, as the name signifies, are constructed in such a manner as to be quite independent of any construc- tional work in fixing. Assuming that they are stood upon a non-inflammable floor or base, there is no need of any brick or mason's work to make them complete. The connection with the chimney is effected by a pipe, and the furnace is made and enclosed in iron, and forms a lower part to the boiler itself. These boilers are rarely used for large undertakings, as their power is somewhat limited, and they cannot be used so economically as those that are arranged for a brickwork setting ; but for small and moderate undertakings their use- fulness cannot be over-estimated. Perhaps the chief drawback to the efficiency of these boilers is the inability to make use of the outside shell as heating surface (what has been termed the flue or indirect heating surface in brick-set boilers). And unless some pre- cautions are taken, the outer surface will bring about a con- siderable loss of heat by radiation, an impossible thing when a boiler is surrounded by brickwork, or with flues containing flame or heated gases. It is very desirable, and, properly speaking, necessary to coat or surround independent boilers with some poor con- ductor of heat, otherwise the practical as well as the theoretical value of the boiler will be unreliable, varying in results with the heat or coldness of its position and surroundings. There are very many materials that can be utilised for the con- servation of heat as applied to boilers, but not all are very easy of application. Slag wool or silicate cotton, for instance, is a material most highly suited for surrounding heated bodies, even those that attain a temperature that would ignite any- Boilers. 157 thing like hair felt, as it is non-inflammable, and is as near as possible a non-conductor of heat ; but as it is a wool-like substance, it would require to be encased round the boiler, and this is not convenient. Asbestos is another material of a similar character ; * but there are now several patented compositions in which, no doubt, silicate cotton and asbestos represent the chief ingredients, and these are fairly easy of application, the chief care commonly being to see that the first coat is made to adhere to the metal, this usually being effected by well rubbing it on. For an application of this material to be thoroughly effec- tive it should be put on sufficiently thick to wholly prevent loss of heat. It usually requires a layer or coating of I J inches to 2 inches thickness to do this (with the boilers now being spoken of), and if when the boiler is full of hot water the hand is applied to this coating and no heat is felt, it is sufficient indication that no waste of heat is occurring in this direction. If space and appearance are of no object, brickwork built closely round the boiler would answer admirably ; but this is a clumsy method, and defeats the object sought in having the boiler of an independent character. Of course, if the boiler or any portion of it was situated in the green-house itself, then there would be no occasion to cover it where the heat radiated was useful in effect and not wasted. As before mentioned, it is intended to commence with the smallest form of boiler, one which has the radiating surface made in connection with it, as, although these little appliances may be esteemed trivial to engineers of great enterprises, they are found particularly valuable in amateur works and for the small glass houses that are often attached to residences. If it were not for these useful little devices it would necessarily become expensive to heat the place, as an independent boiler, of one of the kinds presently described, and a system of pipes would be necessary, as any system of heating by oil stoves is usually found unsatisfactory from several causes. * Both these articles can be had in sheets and slabs, &c., but then they are not so easily applied to boilers as a cement compound. 158 Warming Binldings by Hot Water. Fig. 87. Fig. 87 * shows an apparatus where the boiler is made ot sheet iron or copper, and the whole outer surface japanned. This is arranged to burn oil or gas, the latter for preference. For gas burning they are made in various sizes, the largest being capable of heat- ing 100 feet of 3-inch pipe. In the small sizes they fulfil a decided want, as they are so readily fixed, and the price is particularly reasonable, the smallest costing but 2Os., in- clusive of boiler and case, atmospheric burner, 10 feet of 2-inch pipe, feeder stand, a purifier to fit in the flue outlet, and indiarubber rings to joint the pipes, &c. ; an extensive list of appliances for such a small sum. These boilers can also be had fitted with a flow and return on each side, and so be situated in the centre of the work if desired. The maker of these appliances introduces a purifier to the gas boilers and heating appliances of small size, this appliance being a metal case containing charcoal, through which the products of combustion have to pass. This material is pro- vided to intercept the sulphurous acid which is so particularly hurtful to plant life. This and other details will be more fully discussed when finishing the subject of gas-heated boilers (P. 163). * It is proposed to give the names of the makers of the different boilers and appliances that will be illustrated ; firstly, for the convenience of those readers who may wish to use the particular appliances referred to ; and, secondly, in recognition of the loan of the blocks from which the illustra- tions are printed. The above illustration is from the catalogue of Messrs. Charles Toope & Co., of Stepney Square, London. Mr. Toope, in addition to being a manufacturer of appliances, is an ardent amateur grower, and takes great pride in his collection of orchids, especially as they are grown in Stepney. Boilers. '59 Fig. 88* shows a very original little appliance for window conservatories, its neatness is admirable, yet it is quite com- plete, with boiler, gas burner, filling tube, and a flow and return pipe carried all round the outer boundary of the en- closure. Of course, the gas burner would require to be left alight night and day in severe weather, and attention must needs be given to the filling tube ; in fact, the same details are present that we obtain in a larger apparatus, but it very probably would not fall to a gardener's lot to attend to this one. The attention needed in replenishing would not be at all objectionable, provided the gas flame was properly regu- lated and no unnecessary evaporation took place ; a candle flame, if it were smokeless, would almost suffice. Fig. 89! represents a most ingenious form of gas boiler, embodying in a practical form the suggestions made in Mr. Thomas Fletcher's paper upon " Flame Contact." Mr. Fletcher, in his paper read before the Gas Institute, stated that flame, whether from gas or coal (practically one * This illustration also is from Messrs. Toope's list. f From the catalogue of Messrs. T. Fletcher & Co., of Warrington. 1 60 Warming Buildings by Hot Water. and the same thing), had no actual contact with a vessel containing water at or below 212 (boiling point), and he adduced in evidence several experiments to convincingly prove this. His suggested remedy, which is very practical, appears in the appliance just illustrated in the form of a number of solid studs or rods projecting from the heating surface, these projections acting as heat collectors and conductors. He went on to say that flame readily had contact with bodies at a higher temperature than boil- ing water (with increased effect) com- mencing at about 400, and this takes place with the projecting rods on the boiler, the heat being transferred from their extremities to the water by the high conductive power of the metal of which the rods are composed (copper). It might be inferred that the projections simply act as increased heating surface, and the same results would be obtained if the rods were hollow,* but this is not the case, as he showed by experiment and subsequent calculation. Another peculiar feature with the solid rods is that they present fully twice as much heat-receiving surface to the fire as there is water sur- face, yet they are at no disadvantage, as a given surface of water is capable of absorbing heat at 2-5 times the rate that the same surface of metal (iron) is capable of receiving and transferring it t * If these projections were hollow, they would fail quickly with hard water, by becoming solid with incrusted deposit. Mr. Fletcher has set a limit to the length of these studs, as beyond a certain point they receive more heat than the water can as quickly absorb, and the extremities then perish. t A boiler tube has just been introduced which is a practical applica- tion of this, it being a tube of ordinary length and diameter, but having a series of longitudinal ribs or gills within it thus ^ > which do not interfere with the flue brush, and are considered to give fully 30 per cent, better results than a plain tube. Boilers. 161 Fig. 90. The effectiveness of this principle is demonstrated with the boiler now referred to (Fig. 89), as a small size, measur- ing but 6 inches in diameter and 5 inches in height, is sufficient to heat 40 feet of 2-inch iron pipe (practical quantity) without undue consumption of gas or specially favourable conditions. It requires no support to itself, as the rigidity of the pipes is sufficient for such a light con- trivance, but a boiler of this kind requires to be fixed outside the greenhouse, as will be explained directly. Fig. 90* illustrates another boiler having Fletcher's principle applied to it, but differing considerably from the last so far as shape is concerned. This boiler is made of cast iron, and one par- ticular feature is that its construction is such that it can be used for supplying hot water for draw-off purposes, not- withstanding that a hard deposit may accumulate, for a lid is provided, easy of removal, that gives access to all parts where the accumulation may occur. Provision is also made for easy removal of soot, should the light be attended to carelessly, causing soot to be formed and deposited. Hood as early as 1828 adopted the plan of having a great number of solid protuberances on the heating surfaces of boilers, first, in the form of rods or pins, and subsequently in the form of continuous bars or ribs ; and a Mr. Sylvester afterwards in 1835, an d a Mr. Williams in 1841, both patented other adaptations of this idea. In effect Hood found the plan very successful, but, apparently, no part of the resulting gain was in any way credited to the fact that the flame readily came in contact with the extremities of these projections ; whereas it would not do so with the plain boiler surface. No mention of this fact is made by Hood, so doubtless it escaped observation ; but Mr. Keith found a greater practical value in this improvement, and more recently adapted it again with success ; but he found care was needed in the use of these projecting parts, as they are apt to collect soot, &c., and thus defeat their usefulness. * Also from Messrs. Fletcher's catalogue. M 1 62 Warming Buildings by Hot Water. Fig. 91. Fig. 91* illustrates another form of gas boiler upon an ingenious principle of forming the construction in sections. This principle is adopted by Mr. Keith in nearly all the boilers that he makes.t A particular gain is effected by this arrangement in various ways, the chief being that by making these boilers in parts of moderate bulk a great com- plexity of form can be more readily given them (for they are of cast iron), so as to give the greatest possible heating surface by tubes, convolutions, &c., which could not be nearly so well effected if the boiler was con- structed any other way. In the boilers of large size (for coal burning) this arrangement simplifies the diffi- culties of transport, fixing, &c., and it enables a very great variety of sizes or powers, to be readily supplied (but this latter is chiefly to the maker's advantage). It will be necessary, however, to again refer to this style of boiler later in the chapter, and fuller particulars can then be given, as most details apply to those boilers con- structed for coal and coke burning. The particular boiler now being referred to (Fig. 91) is but 13 inches square, but varies from 15 to 28 inches in height, depending upon the number of sections used. Gas boilers are not made to heat more than about 100 feet of 4-inch pipe (200 feet of 2-inch), but if desired, no doubt they could be made larger to order ; but if a larger quantity of pipe than the above had to be heated by gas, it would be better to have a group of the 100 feet boilers, a battery so to speak, connected together, * From the catalogue of Mr. James Keith, 57, Holborn Viaduct, London. f Mr. Keith also uses heat collecting studs and fins in his boilers, and has done so for many years, having included them in one of his patents in 1875. Boilers. 1 63 than one of an unusual size.* They could then be used one or more at the time as desired. Every gas boiler, whether small or large, should, properly speaking, be fixed outside the greenhouse. Under some circumstances, and where they receive attention and care, they do well inside, but this should be considered merely an exception to the rule, and by no means be regarded as a precedent even by those who have fixed them inside successfully. Even when so fixed, the burnt gases, as they are called, the products of combustion, must be carried outside except in the very small sizes. Small stoves are sometimes fixed inside, and discharge their products there without appreciable ill effect, provided a means is adopted of arresting the sulphur fumes (sulphurous acid SO 2 ) that are always given off from gas stoves, and which are so particularly hurtful to plant life, even in small volume such as we get from a single gas-burner for instance, if the area be limited. The question as to the different properties of the products of combustion from gas-burners will well bear a short explanation, as new gas stoves for various purposes are being introduced every season, and many of them are devoted to greenhouse and conservatory work. The products derived by the combustion of carburetted hydrogen (coal gas) burnt from a Bunsen or atmospheric burner, which is almost exclusively used in heating work, consist of carbonic acid (CO 2 ) and water (H a O),f and some other gaseous matters which are the results of impurities which cannot wholly be eliminated in the manufacture. These impurities, with one exception, are either harmless or in such small quantity as to be of no consequence. The exception is sul- phurous acid, which is brought about by the combustion of a small percentage of sulphur which is always carried over with the gas in the manufacture, and at present cannot * The chief reason why larger gas boilers are not made is that the demand would be so limited ; for if any large quantity of pipe had to be heated, a gas boiler could not do it nearly so economically as a boiler heated by coke. t Of course another, and the chief result of combustion, is heat. See Combustion. M 2 1 64 Warming Buildings by Hot Water. wholly be disposed of, although every effort is made to effect its removal. It is the sulphurous acid and carbonic acid gases that are the objectionable elements in the products, but the former is most hurtful to foliage. It has been mentioned that small stoves may discharge their products into the greenhouse without any noticeable effect, provided the former of these two substances is arrested. This is because carbonic acid in limited quantity is non-injurious to plants, it being their food,* but even this latter substance must not be present in any volume, as apart from its effect upon plants, it would then become hurtful to human life, causing asphyxiation. With small gas stoves the removal of the sulphurous acid is generally done by taking advantage of the great affinity this substance has for water. One of the products of combustion is water, as just explained, and if this water of combustion is condensed by being brought into contact with a cooling surface before it escapes, it will be found to have collected the sulphur with it, and the carbonic acid will go free, in- odorous and tasteless, and not so observable as when it carried the unpleasant odour of sulphur with it. This has led a good many makers of gas stoves to perpetrate what looks greatly like an imposition upon the public, as there is a form of stove now made called a " condensing " stove, which acts in the manner just explained, the water of com- bustion being condensed! by having to pass through two cast-iron tubular columns. A maker's list before the writer distinctly states that "all the products of combustion are condensed." We must charitably attribute this assertion to ignorance, as Nature lends her aid to the deception by making the carbonic acid quite unnoticeable to the average person * Plant life absorbs, and is nourished by carbonic acid (but in daylight only). The carbon is taken up, and goes to make living material, and the oxygen is set free. t Approximately it will be found that the greater part of a pint of water can be brought down from every 30 feet of gas burnt, the quantity varying, however, with the area or coolness of the condensing surface. This water has a very unpleasant smell, and acid properties. Boilers. 165 after the sulphur is removed. It is fortunate this style of stove cannot well be made in large size, for the volume of acid gas then given off would speedily be dangerous in a small or close apartment. There are two chief objections to having a gas boiler in the greenhouse. One is the possibility of the gas escaping (by accident, carelessness, or other cause) unburnt,* this being firstly an element of danger by explosion, and it is just about as injurious to plants as the sulphurous acid just spoken of. The second objection is the liability of the products of combustion being discharged into the house notwithstanding the flue provided to carry them outside. There is a notion, much too prevalent, that a piece of pipe taken from the stove through the wall, constitutes a sufficient flue for a gas stove, but nothing could be more incorrect, a flue to a gas stove must be erected and carried out in every detaL tJie same as a flue for a coal stove, but because the ill action of the flue cannot be very well noticed with a gas stove as it can when there is smoke, these flues are commonly put up upon some hypothesis of the workmen engaged (and their ideas are extraordinary sometimes)! and the consequence is that on many days (depending upon the direction of the wind usually) the products will not pass out of the flue-way at all, but insist upon coming into the house. The question of flues or chimneys will receive proper treatment in a later chapter (see Chimneys), and it will therefore suffice to mention here that the flue from a gas stove should rise above the house top, * For this reason, the flue pipe from a gas stove should never be carried into the brick chimney of a house, as an escape of gas from the stove might bring about serious results. t An exceedingly common idea entertained by many, even well- informed people, is that if a coal stove or grate is rendered useless by reason of the chimney having a defective draught, a gas stove can be successfully substituted, the supposition being that the gaseous products from the latter will pass up the chimney in no way interfered with by the bad draught, although exactly similar products from a coal fire, but carrying a little soot with them, fail to do so. No notion could be more incorrect in fact, it borders upon absurdity ; and, although not entertained by specialists, it is very prevalent amongst workpeople. 1 66 Warming Buildings by Hot Water. and in some cases the addition of a conical cap is desirable or necessary. If the boiler is fixed outside the house it is still necessary to carry the flue up to a sufficient height, as, although the escape of combustion products will not then materially matter, the down-draught will interfere seriously with the proper working of the burner (usually by blowing the light out), sufficiently so in all probability to render the apparatus useless, and it must not be forgotten that in an iron flue a deal of condensation will most probably take place, depending upon the situation, and some provision must be made for the disposal of the constant stream of water that will be trickling down the flue if the products of combustion become sufficiently cooled to bring about this result. When a gas boiler is fixed outside the house it becomes necessary to surround it with a box-like structure, a little house, to protect it from the elements, particularly from strong winds, which will be found to interfere seriously with its steady working unless some method is adopted to guard against the trouble. This enclosure must not be anything like air-tight, as the burners, like a coke furnace, must have a copious supply of air to effect combustion, and in addition to this, as the burner is sure to be of the atmospheric type, a free supply of air must have admission to this also, otherwise the peculiar character of the burner will be destroyed, and the worst results ensue. A grating, or strip of perforated metal, is all that is needed to ensure the necessary supply of air, but let this be of fair size, and insert it in the side of the structure that is least exposed to the weather. A very necessary precaution in the use of a gas boiler, particularly with one that is enclosed, is never to turn on the gas until the light is ready to be applied, and before the light is applied it is a wise precaution to open wide the door of the enclosure, so that any possible collection of gas may be dispersed. If a burner is blown out by the wind there is instantly a source of danger, by the escape of unconsumed gas that takes place. Boilers. We can now turn to the consideration of independent boilers that are used with coke fuel.* These outrival gas boilers in variety, also in power, and although they may need a little more attention in stoking and occasion a little trouble by dirt, they are considered more reliable, and there is less trouble in other ways. Very many of them are now made that will admit of economy in attention by taking a charge of fuel sufficient for many hours (depending, however, upon the way the flue damper is used). Fig. 92. Fig- 93- Figs. 92 and 93 f illustrate the least powerful and least expensive of these, yet having all the essential features and conveniences of the larger ones. These are usually known as * Occasionally 'ordinary and small coal is burnt in independent boilers, but it is objectionable in many ways, and should never be used if coke can be obtained (this is not always possible, if the boiler is in some remote country place, and no gas works within very many miles). The chief advantage with coke is its adaptability for charging purposes ; for as fast as the lower part of the charge burns away some more falls to replace it. and this could not be relied upon with coal, as it fuses, and cakes into a mass. t From the catalogue of Messrs. Hartley & Sugden, Halifax (England). 1 68 Warming Buildings by Hot Water. " star " boilers, but different makers give them different names to suit their own purposes, for this pattern is not confined exclusively to one manufacturer, it can be seen in nearly every boiler maker's list that may be taken up. Both have top feeders, that a good charge of fuel may be put in at once, but Fig. 93 is particularly adapted for this, as the extended portion on top is provided expressly to take a greater quantity of fuel, this fuel gradually falling and coming within the area of combustion as that nearest the furnace bars is consumed. This advantage is greatly heightened by having the boilers, and also this extended fuel chamber, slightly conical in shape, as this prevents all liability of the fuel " bridging " itself, that is refusing to fall, and added to this the conical shape causes the sides to slightly overhang the fire, and the more this can be done, the better the results. The writer would much like to see a boiler of this class or the " dome top " (presently to be mentioned) provided in every private residence of fair size to furnish hot water for domestic purposes, instead of the customary " high-pressure " boiler that is fixed in the kitchen range. The results with an inde- pendent boiler are so much more regular, not depending upon the cooking (which regulates the attention to the fire), and the charge of fuel spoken of would keep the water hot night and day, and there would be plenty in the early morning, when there usually is none. In many cases there would be an actual saving in fuel, for it is really astonishing how much more quickly a cooking range acts when it has no boiler in actual contact with the fire, and how very economical in fuel it at once becomes (see ' Hot Water/ p. 350). The boilers just referred to (Figs. 92 and 93) are made to heat from 1 50 to 700 feet of 2-inch pipe (theoretical quantity). Both are made in exactly the same sizes, the disparity in the illustrations is rather misleading. They are made of cast-iron, and the pipe-sockets and flue nozzle can be had on right, left, or at back as desired. Fig. 94* represents what is known as a coil boiler, con- * From the catalogue of Messrs. Hartley & Sugden, Halifax (England). Boilers. 169 sisting of an outer iron case, with the usual furnace fittings, &c., but instead of having what we recognise as a boiler it has a coil of pipe placed so that the fire acts strongly upon it, as shown in the illustration, which exposes the interior of the boiler. This boiler is Fi S- 94- also of small size, to heat from 100 to 450 feet of 2-inch pipe, but it has all the necessary fittings complete, and it will take sufficient fuel to last all night without attention. A coil, under some circumstances, may be considered the most powerful form of boiler (for the space it occupies) ever in- troduced, as it is wholly direct heating surface, and is also wholly in contact with the glowing mass of fuel, but there are objections to its use (which objections are greatly obviated by using a large-sized pipe, as will be referred to when treating brick-set boilers). Perhaps the great objection is in the smallness of the pipe, causing a stoppage and subsequent fracture by the accumulated dirt, which is difficult of removal, and this precludes its use in anything like a complex form.* There is no objection to a coil of this description upon a small scale, as the evaporation and consequent replenishing of the water supply is not great, and there should be a proportionate decrease of the dirt that finds its way into the pipes. It is a common and very convenient arrangement to put a coil of two or three pipes into an ordinary grate for the purpose of heating a radiator in another room of a residence, as is ex- plained on p, 281. Figs. 95 and 96 1 show a description of boiler commanding * In heating apparatuses upon the high-pressure system, large coils of small pipe are invariably used, but in this case the apparatus is sealed, and all dirt matter is thus excluded. t The " Finsbury boiler," from the catalogue of Messrs. Lumby, Son, & Wood, Limited, of Halifax (England). 1 70 Warming Buildings by Hot Water. a large sale, and which has received much favour since its first introduction a few years ago. It was first introduced under the name of the " Loughborough " boiler, as it originated in Fig. 95. Fig. 96. that place, and it fulfils a decided want. Its peculiarity con- sists in its being adapted for building in the thickness of a wall (see p. 98), so that all the stoking and feeding doors are practically away from the greenhouse, yet the pipe con- nections are inside, and every inch of pipe does useful work, thus saving the cost of providing connecting pipes between the boiler and the radiating pipes (so commonly necessary with independent boilers, which cannot always be fixed near to the house) and also the loss of heat that takes place from these connecting pipes unless they are well protected. It will be noticed that there Is an arrangement inside which prevents the flame and heated gases taking a short cut up the front of the boiler and out of the flue way, and they are instead compelled to come in contact with the back and sides and impinge against the top, and thus give their greatest effectiveness. In the writer's opinion the waterway front is not of value proportionate to its cost, as this part is openly exposed to all weathers, and the water in contact at this point experi- ences a great cooling influence which must materially prejudice Boilers. 171 the efficiency of the other heating surfaces. These boilers are made to heat from 300 to 1200 feet of 2-inch pipe, and the smoke nozzle (which is fitted with a damper) can be placed on right or left side of the front as required. Fig. 97* is a boiler similar in character to the one just described, being suited for fixing in the thickness of a wall, Fig. 97. but it has one or two improvements that are desirable addi- tions to a stove of this description. This is called by the makers " The Horse-shoe boiler " as the plan of the boiler portion is of this shape extending round the back and the sides in a semicircular form. There is no waterway across the front, and as just mentioned, none is needed ; but in this boiler there is a peculiar arrangement for the inflowing air to pass down just inside the front as illustrated, so that it becomes highly heated before it enters the fire, a hot blast in fact, which * From the catalogue of Messrs. Kinnell & Co., Southwark, London. 172 Warming Buildings by Hot Water. produces economical results. A further feature is what the makers call a revolving bottom grating. This, however, does not revolve, but can be made to oscillate or rock, so as to shake out the ash that accumulates and chokes the draught. A further feature peculiar to this boiler is an automatic or self-regulati'ng air-inlet, shown as a flap in the illustration, just below the feeding door. This flap acts upon the principle of Dr. Arnott's ventilator in the fact that it can be set so as to adjust itself to the draught, a feeble draught leaving it full open, a strong draught drawing it partially close. This im- provement is worthy of commendation, as it is in reality a self-acting damper, a thing very much desired, but, to the best of the writer's belief, not yet made in a perfect form, a form that will prove itself efficient at all times under all conditions. If the one now in question acts perfectly, the maker (or inventor) is deserving of the highest praise. It will be readily understood that a damper does not of necessity have to be in the flue, as a provision for regulating the inflow of air to a fire, checks or accelerates combustion just as well as a provision for regulating the draught up a chimney ; in both cases the passage of air through the fire is controlled equally, and this controls the speed of combustion. A self-acting damper evinces its utility particularly when the draught in a chimney is variable (as is frequently the case, for the wind and weather will commonly bring about this effect), as it will then accommodate itself to the varied conditions, and the draught or passage of air through the fire will remain regular. Another good feature in this boiler is that the waterway is continued below the fire-bars. This is a feature that can be had with almost any wrought iron independent boiler, if so ordered ; it could also, with some extra trouble, be arranged with brick-set boilers. It incurs a little extra expense, but is even better if the waterway is also brought right beneath the ashpit as in Fig. 98.* The advantage gained is that accumu- lations of sedimentary matter (dirt) which always settle at * From Messrs. Hartley and Sugden's catalogue. Boilers. Fig. 98. the lowest point, are taken below the fire, so that, however much it may collect at this point, its effect is nil, for it is only when the deposit is successful in keeping the water away from the boiler plate, against which the fire acts> that harm ensues, or a frac- ture occurs. Were there a return pipe entering the boiler at the bottom just above the level of the fire-bars, this pipe would more readily get stopped with dirt if the boiler terminated at the fire-bars, than it would if the boiler were continued below. The desirability of having the waterway right across the bottom beneath the ashpit, as just illus- trated, consists in that it permits the whole accumulated matter to be removed from one mudhole (if a good-sized one is put) as the raking instrument when inserted will reach all around the lower part, as can readily be understood.* This advantage applies chiefly to boilers that are circular in form, as most independent boilers are, for it can be seen how difficult it is to clear out the deposit from the cylindrical portion of the waterway, unless some five or six manholes are provided, and then it cannot be done so well ; the waterway bottom forms a sort of catch-pit or settling bed for sedimentary matter. With hard deposit (" fur ") the waterway bottom has a beneficial effect, but of a different character, in this way. When this matter is precipitated it generally adheres to the surface it is deposited upon, particularly if this surface is at a high temperature. Now the surfaces bounding the fire (if a waterway bottom exists) are vertical, and consequently a very * It can be plainly seen that it is at the boiler and not in the pipes where the greatest amount of dirt accumulates, as the boiler is at the lowest point, all pipes sloping down towards it. 74 Warming Buildings by Hot Water. Fig. 99. small proportion of the deposit adheres here, as the major portion of it falls very naturally straight down, which carries it below the highly heated area. On the other hand, if the boiler terminated on a level with the fire-bars, as is most usually the case, practically the whole of the deposited matter must collect just at the point where the greatest heat is felt, con- sequently it becomes exceedingly hard, and the quantity soon becomes sufficient to keep the water away from the iron, and a fracture ensues. In addition to the obvious disadvantage of terminating the boiler at the furnace bars, which practically assists the deposit in injuring the boiler, there is another drawback in the fact that at the angle immediately nearest the firebars there has necessarily to be a weld or joint, a weak point where it should be strongest, but which of course is remedied by carrying the waterway down below. What should be aimed at is to prevent a collection of deposited matter of any description being formed in close proximity to the firebox, the only place where it can have an ill effect ; the deposit is practically harmless above or below where the glowing fuel is situated. A further advantage in continuing the waterway to the bottom and making the boiler in- dependent of a base is, that occasion- ally a leakage of gaseous products may take place between a boiler and its base, and if any part of the boiler is in the house these gases would prove objectionable. But this could only occur when a downdraught manifested itself in the chimney. Fig. 99* shows in section the " Ivanhoe " boiler, another of the class that is suited for building in the thickness of a * From the catalogue of Messrs. Robert Jenkins & Co., of Rother- ham. Boilers. 175 Fig. 100. wall as illustrated. In most respects this is similar to other boilers of this character, the chief variation being that with the small sizes only the inner side, the back, has a waterway, the front and right and left side being iron and fire-brick, but to increase its effectiveness the waterway can be continued round one or both sides. This boiler has the advantage of having a very good- looking shape, which adapts it either for fixing in a wall or standing clear (in a potting shed or adjacent outhouse). Fig. 100* is the well-known welded dome-top boiler, the dome having the flow-pipe on its apex, which decidedly favours better results than when the flow-pipe has to start horizontally from the side. This is a boiler which is greatly benefited by having the water- way continued to the bottom, parti- cularly in the larger sizes, it being made to heat from 350 to 3250 feet of 2-inch pipe (theoretical). This boiler, as in fact all boilers, should have a proper complement of mud-holes. Two are not sufficient with a cylindrical boiler like this, as it is so difficult to get any instrument, even a cane, to pass round the circular sides to disturb the sediment. Three or four holes should be provided, and if the sediment is likely to be hard, manholes and not mudholes should be put. Fig. ioit is a description of boiler that is worthy of every commendation, being powerful (heating from 800 to 2200 feet of 2-inch pipe), and very compact in shape. This is in reality a saddle boiler with terminal or waterway ends back and front, a boiler that will be strongly recommended when treating of brick-set boilers. The waterway front end, how- * From the catalogue of Messrs. Graham & Fleming, Halifax (England). t Also from Messrs. Graham & Fleming's list. ^C2^*~. k Of TffiR IVBESITT; fcjfc_^ i 1 76 Warming Buildings by Hot Water. Fig. 101. ever, necessitates a top feeder as shown, not that this is a disadvantage by any means, quite the reverse, as it enables the boiler to more readily be charged with fuel to last several hours without attention. Hori- zontal boilers can of course be charged with fuel in this way without a top feeder, but this latter arrangement makes it more easily done, practically as easy as with a vertical boiler. This boiler is more easily cleaned than the circular ver- tical shape, but it would be none the less better for having the waterway carried down be- neath the firebox as recommended. This shape of boiler is in many respects preferable to the vertical, with exception as to the space it occupies. If space has not to be economised, then it is the best to be used of the two. This boiler is of a square shape in cross section, which makes the heating surface above the fire flat. This is no objection, the dirt does not accumulate at that point, the circulatory move- ment of the water prevents this, and no provision need be made for cleaning at the top part of the boiler. Fig. 102* is another boiler similar to the last, but without the waterway front. This can, of course, be had or omitted just as the user wishes, but, as shown, no top feeder is actually needed if the waterway front is not used. This illustration is chiefly introduced to show the waterway tube that passes from side to side across the fuel chamber. This is an addition that never fails to materially increase the heating power of * Also from Messrs. Graham & Fleming's list. Fig. 102. Boilers. 177 the boiler, as it is wholly direct heating surface, and situated at a point where it cannot fail to receive the full benefit of the heat, at some times being almost enveloped with fuel in a glowing state. Sometimes these cross tubes are quite horizontal, but there is no doubt that some benefit accrues by letting them slope from side to side, which is the usual way they are fixed. In either case cleaning holes should be placed on one or both sides of the boiler, opposite the terminations of the tube or tubes, not that any noticeable amount of soft or dirt deposit will be found here, but that any incrusted deposit that may be formed can be removed, for with powerful boilers the amount of water evaporated is a fair quantity in six months, particu- larly if the boiler is fully powerful and overheats sometimes, and more particularly if any water is drawn out of the apparatus for the gardener's use. In this latter case con- siderable attention must be given to the cross tubes, as they generally get incrusted more quickly than any other part, and are a great source of trouble if fractured. Of course these latter remarks only apply to the use of hard waters, but with soft waters holes should be provided that the tubes may be examined when the bottom of the boiler is being cleaned out. The next, and last, description of independent boilers to be noticed are those made by Jas. Keith, being widely different in character to any we have mentioned yet, and having many novel and decidedly advantageous features in them. Fig. 103,* "The Challenge," is perhaps the best known of the boilers made by this firm. This is made of cast iron, in square ring sections which are placed one above the other, the parts which come together being turned and faced true, so as to easily effect a perfect joint. The particular gain resulting from its sectional construction is that the interior can be so readily made of any varied shape that may be considered to give the best results, that is to arrest and cause absorption of the heat, a result that cannot be arrived at in a * From the catalogue of James Keith, Holborn Viaduct, London, and of Glasgow and Edinburgh. N 178 Warming Buildings by Hot Water. boiler wholly made in plates, which can only give us plain flat surfaces as a general rule. These sections take more than one form, those near the fire being less complex than elsewhere, to facilitate cleaning. Fig. 103. Those forming the upper part of the boiler are much like gratings, the cross bars being water tubes, so that the products of combustion by the time they arrive at the flue outlet of a tall boiler have very little useful heat left in them. Boilers. 1 79 It must be noted that the arrangement of these different heating surfaces has been very judiciously arrived at, so that there are no collecting points for deposited matter, all water- ways being kept of a vertical shape and well arranged. The use of sections in this case introduces another convenient feature in the fact that the section having the feeding door in it can be placed at any height, so as to make it possible to charge the boiler with a quantity of fuel, or not, as required, but for the most powerful results it is better to have the firing door at the low point.* There is not the least doubt that the large amount of direct heating surface obtained must produce a most rapid circulation in the boiler itself, and there is the possibility that this, in a very great measure, prevents sedi- mentary matter being deposited. But this is rather a dis- puted question at present, and the writer unfortunately has not yet had an opportunity of arriving at a sufficiently satis- factory solution of the question. Theoretically it is right, but practically it may show different results, and if in practice it is found that a very rapid circulation prevents the deposit resting anywhere, it would only apply to suspended matter and not to the hard deposit from lime, &c., in solution. These boilers are made to heat up to 7000 feet of 4-inch pipe (if miles), but it is very necessary that they should be coated or surrounded with some material that is a poor conductor of heat, otherwise a serious waste of heat must necessarily occur. Fig. 104! is a boiler of a very powerful character, as the internal heating surface consists, not only of the shell sur- rounding the fire, but also of vertical tubes, and a saddle * It will be readily understood that when any boiler is filled up with fuel a deal of the inner or direct heating surface must be shielded from the heat by the mass of fuel laying above the active part of the fire, and at this time it is the parts of the boiler that have the red fuel resting against them that do all the work. Of course, by urging the fire the whole mass could soon be got into a hot state ; but this is not done as a rule. When the charge of fuel is partly burnt and sinks down, the upper heating sur- faces then experience a benefit. t Also from Mr. Keith's list. N 2 1 80 Warming Buildings by Hot Water. overhanging the fire in such a way as to receive the greatest possible benefit of all heat and heated products. The interior surface of the boiler constituting the fire-box is ribbed, and the bottom grating is fitted so that it can be shaken (rocked) to clear the fire from ash, &c. Fig. 104. The illustration gives a very clear and sufficient explana- tion of the external portion of the boiler, but it may be pointed out that this pattern can also be had with the water- way carried down and beneath the fire if required. This makes the boiler safe in use on an inflammable floor (sup- posing it is never fired when empty, a most unlikely occur- rence), and it permits of pipes being carried to the boiler on the floor level without dipping them. This, also, is of con- Boilers. 1 8 1 siderable use and convenience when pipes or radiators upon the same floor level as the boiler have to be heated. This boiler is of cast iron, and made in varied sizes to heat from 200 to 3000 feet of 2-inch pipe. The feeding door is situated so that the fire can be charged with fuel to last several hours when desired. 1 82 Warming Buildings by Hot Water. CHAPTER IX. BOILERS, FOR BRICK SETTING. Saddle boiler and modes of setting it fully described Water bars and connecting Check ends and waterway fronts Cross tubes Flued saddle boiler The " Colonial " boiler The " Climax " boiler The "Imperial" boiler The "Delta" boiler The "Excelsior" boiler WagstafPs tubular boiler The " Champion " boiler Week's tubular boiler Water bars for coil and tubular boilers The " Python " boiler The Trentham Cornish boiler. THE chapter just finished dealt almost exclusively with boilers of the independent kind, and which require no brick- work in their construction or setting (unless it is desired to build them in a wall, or to jacket them with brickwork). It is now proposed to treat of those that are dependent upon the bricklayer for their erection, setting, and subsequent efficiency. The independent boilers shown constitute but a small portion of the great variety that are made, but enough has been said to illustrate the features that may be considered essential and good or bad in them. The boiler that must take precedence in the following list is the "Saddle," Fig. 105. This shape stands high in every one's esteem, for it has been tried in every conceivable way, and found satisfactory. Hood praised it at least twenty years ago, and it is in favour still ; and very many, most in fact, of the new designs of wrought boilers introduced follow the saddle shape to a great extent, as will be seen as the chapter progresses. Boilers for Brick Setting. 183 The particular features in favour of the saddle boiler are, firstly, of all wrought-iron boilers it is about the cheapest to make ; its shape is particularly adapted to receive and benefit by the heat evolved, especially the direct heat, which is the most valuable and effective, and it is found in practice that this shape is free from the faults that are brought to light from time to time with the many new shapes introduced. The saddle shape, however, is not usually adopted for works that exceed, say, 800 to 1000 feet of 4-inch pipe, as it is beneficial to bring the heating surface within a limited area, so that it may profit fully by the heat radiated from the fire, and this is effected by adding waterway ends, cross tubes, &c., which greatly increase the power of the boiler without increasing the size, as has been already ex- plained. If we used a very long saddle boiler it would necessitate our greatly increasing the length of the fire if we wished the whole internal surface to receive a full share of the radiant heat which is so necessary for good results. From the illustration (Fig. 105) it will be noticed that from a point about half way up the boiler, the top describes an almost true half circle, both outside and inside, but to the writer's mind greater effect would be obtained if the boiler was made more square in shape so that the inner the direct, and most valuable heating sur- face would be added to, and the vertical flue surface would be increased, the vertical sur- face doing more effective work than that which comes beneath the heating products as is the case with all the outside rounded portion of the ordi- nary saddle boiler. Fig. 106 illustrates what is meant by making the boiler square in shape, and it will be readily seen that the internal and external surface is added to, and of course the quantity of plate used is increased proportionately. Fig. 1 06. 1 84 Warming Buildings by Hot Water. There is not the least doubt that the top outer surface of a boiler, whether it be round or flat, is of little value, as in the first place every one knows what little useful effect is pro- duced by applying heat to the top of a vessel ; and secondly the top of the boiler of either shape has always a coating of dirt or soot upon it (except immediately after it has been swept clean), and this dirt material is always of a low con- ductivity, so that it permits of little heat passing through the boiler plate to the water. In the square shape of boiler the top surface could still be made use of if desired, but it must be contended that by placing the mid-feather half way up the side of the boiler and causing the flame to travel up and down the side only, better results will be obtained than if any part of the side surface is neglected for the sake of passing the heated products over the top. With the shape under discussion the top need not be used at all (unless particularly desired). There is ample vertical surface for the heat, with an ordinary draught, to act upon, and every one must admit that however low a value vertical surface has, it is more valuable than any surface that comes beneath the source of heat, the source of heat in each case being equal. If, with this square shape, no use was made of the top outer surface the cost and labour of fixing would be reduced to a small and simple affair, as no arch would be needed. As before mentioned the " saddle " boiler has always been found very effective and satisfactory for many general pur- poses, as it is free from complexity ; and it is somewhat ex- ceptional for it to be set wrongly, as it has become so well known and used by all classes of heating engineers. The mere fact of the knowledge of its proper setting being so general has doubtless gone far to effect its recommendation, as many engineers, especially those who have no very extensive prac- tice, are naturally somewhat shy of the newer patterns of which they have had no experience. But as before mentioned, however much the " saddle " shape may be esteemed, it is not suited for large works, as for economical and rapid results we Boilers for Brick Setting. 185 must have the direct heating surface as extensive as possible close to the fire, or next best to this, have flues constructed within (i. e. through) the boiler itself where the heated gases can do effective work almost immediately they leave the burning fuel, and before they can have possibly lost heat. There is more than one method of setting a saddle boiler, and for the smaller sizes it is doubtful if leading the flame to and fro, the length of the boiler, is so satisfactory as the following way, which permits all heated gases, &c., to escape at all points around the boiler, and envelope it so to speak. This method is to have the furnace bars, dead plate, and other fittings in their customary places, but instead of the boiler standing level with the fire grating it is placed upon four firebricks, one at each corner, forming four feet, which raise the boiler about 3 inches above the level of the bars ; and instead of bringing the boiler tight against the front brickwork, and also partially closing up the back portion, it is simply stood so as to come within, say ij to 2 inches of the brickwork at either end, with a clear space of 3 to 3 J inches up each side and over the top. Figs. 107 and 108 show the arrangement in length and cross-sections, but the position of the chimney requires con- Fig. 107. Fig. 108. sideration, as it must always be remembered that the action of the draught induces the flame and heat to take the shortest or easiest route, if there are two or more ways 1 86 Warming Buildings by Hot Water. unequal in length or size, &c., by which it can pass. In the illustrations the chimney is shown, built to pass off as near as possible, centrally over the top of the boiler, and supposing it were situated exactly over the centre and the flue passages up the boiler sides were equal in size, the boiler would heat about equally all round. If, however, the chimney was not so situated, steps would require to be taken, by means of de- flecting plates, &c., to cause the flame to distribute itself generally in all directions as it passed away from the fire. But this arrangement is only suited for small boilers, and unless the circumstances appeared very favourable the writer would not recommend this method as against the customary way of conducting the flame up and down the boiler side as next to be explained. It must also be pointed out that when a fire has been going quietly for several hours there accumu- lates a quantity of ash on the fire-bars and this would some- what interfere with the free passage of heat to the outer or indirect heating surface of this boiler by choking the way along the bottom each side. It will be understood that the reason for giving a ij-inch space between the front and back ends of the boiler and the brickwork, is to prevent the flame having too free a passage in either of these directions to the prejudice of the outer side heating surfaces ; and if the chimney was situated at the back end of the boiler (could not be carried otherwise) instead of centrally over the top, then it would be better to let the back end of the boiler butt tight against the brickwork, without any passage way being left at this point. The most customary and, at present, the best way to set a saddle boiler of any size, is to provide flues passing to and fro along its outside as follows : The boiler is placed upon a level with the furnace bars* and so as to come tight up against the * Any direction as to the height of the furnace bars is rather unneces- sary, as the position for these is fixed by the make of the furnace fittings, that is the front, with fire doors, and the other articles that constitute the set of fittings, which are purchased complete from the boilermakers or elsewhere, and which show exactly where the furnace bars are to come. Boilers for Brick Setting. 187 front brickwork, that which the front fittings are fixed against, making a flame-tight joint at this point as Fig. 109.* This brickwork will be 9 inches thick. The furnace bars, in addition to having their upper surface on a level with the Fig. 109. SECTION OH E. F. bottom of the boiler, are so arranged that the front extremities of the bars are exactly in a line, vertically, with the front of the boiler, the dumb or dead plate extending from the bars to the furnace door as shown, and this plate should come exactly level with the furnace stoke hole, so that all the parts that constitute the bottom of the fire-box, where the fuel rests, are on a level from end to end right through as illustrated. The bars usually occupy about two-thirds the length of the fire-box (see area of fire-bars, p. 155), resting at one end on the dead plate, which should be rebated to receive them, and at the other end on a bearing bar on or in front of the solid brickwork which extends from this point, the rest of the way to the back.f The back end of the boiler does * From the catalogue of Messrs. Robert Jenkins & Co., Masbro' boiler works, Rotherham. t The furnace bars are always kept forward, so that the whole of the direct heating surface may have the full benefit of the heat before it passes to the flue entrance. 1 88 Warming Buildings by Hot Water. Fig. no. not come against the back wall, but is kept from 5 to 7 inches away from it to admit of making the proper passage way from the interior of the boiler to the outer flues. Between the boiler and brickwork at back is built a fire- brick bridge or check end (to check the too free escape of heat, &c.) extending from side to side as shown on the plan drawing Fig. 1 10,* and reaching quite half way up the arched opening in the boiler, as shown in the last illustration. With small boilers a thick fire- brick slab is occasionally used for this purpose. This bridge fulfils another useful object in forming a bound- ary to the fire-box, as were the side flues to have their entrances low down the stoking of the fire would quickly cause them to get partially stopped with cinders and debris. Above this check end, another bridge has to be made to prevent the exit of flame from the upper part of the arch into the upper flue above the mid-feathers. This bridge may be made with a large firebrick if the boiler be of limited size, but usually it consists of an arch formed in firebricks, as will be fully explained shortly. The illustration shows the direc- tion the flame has to take, the arrow passing sharp round to the outside of the boiler, below the mid-feather, the position of which is indicated by the dotted lines. Fig. no| shows m P^ an ( at a point just below the mid- * This bridge usually extends right to the brickwork each side, nothing is gained by keeping it just the width of the boiler, t Also from Messrs. Jenkins and Co.'s catalogue. Boilers for Brick Setting. 189 Fig. in. SECT I ON \ONA.B. feathers) the position of the lower firebrick bridge with arrows showing how the flame passes to right and left around to the outside of the boiler within the flues referred to. The extent of the side flues, the position (in plan) of the two lower soot doors, the fire-bars, and dumb plate, &c., are also clearly shown. Fig. 1 1 1 * shows the same boiler in sectional elevation, the section being across the front of the furnace bars. It will be noticed that the brickwork forming the bottom of the side flues is also on an exact level with the bars, so that at the moment the fixer is about to place the boiler in position, the erec- tion, as far as he has proceeded, is about 12 inches high, and perfectly level from side to side, and from end to end. At the back end of the boiler will be seen the bridge already referred to ; and the flow pipe proceeding from the top, and the return entering the side are also shown clearly; the return pipe can of course be brought in either side, or one in each side if desired, but the position of the return pipe will be further referred to directly. The most important features in this illustration are the mid-feathers, and the arched flue-way which the mid-feathers divide into three parts. These drawings are not to scale, so no accurate result can be arrived at by comparing any portion with the size of the bricks of the brickwork, and it will be noticed that the flow pipe, assuming that it is 4-inch, is out of proportion with the size of the boiler. This is merely mentioned as it is so customary and natural to judge ap- proximate dimensions by comparison. This flueway, at sides * Also from Messrs. Jenkins and Co.'s catalogue. 1 90 Warming Buildings by Hot Water. and top of boiler, as here shown, and which appears on the other drawings, must be of a proper size (width) as, if too small, it will choke the passage of flame, and with coal fuel it would be soon stopped with soot ; if too large, the flame or heated gases will not have their full useful effect, for (as already explained) flame has a most pronounced tendency to float between surfaces without having contact with them where it is possible, and as flame radiates but a very small amount of heat, it is very necessary that it should be made to impinge or have contact with the parts to be heated. When the flame leaves the interior of the boiler at the back, the direction in which the draught impels it to travel, makes it hug, or cling to, the sides of the boiler, so as to neutralise to some extent the inclination which flame has to avoid contact with surfaces, but notwithstanding this if the flue were too wide little contact would take place. When the flame ascends from the side flues, in front, and passes into the flue over the top of the boiler, the flame, following its natural tendency, is inclined to seek the highest point and does more towards heating the top brickwork than heating the boiler top. All these arguments go to show that the flues must be restricted in size, and as a general rule 4^-inch is the size that should be adopted. This size is subject to variation to some extent as the boilers vary in size. 4-inch or even 3-inch would suffice for the smaller boilers, say less than 3 feet long, and in those of large size, a 6-inch flue would be better suited. It may be considered that the majority of plain saddle boilers made measure between 3 and 6 feet in length ; many are of smaller and larger sizes than this, but they do not represent the majority by any means, and between these two sizes a 4j-inch flue is suitable. The mid-feathers extending from the end of the boiler to within about 6 inches of the front, as shown by the dotted lines on Fig. 109, can be made of firebrick, iron plate, or, if desired, the boiler maker will make a waterway through them, Boilers for Brick Setting. 191 Fig. 112. as Fig. 112. They are most commonly made of firebrick, as if iron is used it should be affixed to the boiler by the maker, which may cause delay. It is quite possible to support an iron mid-feather from the brickwork, although it is not such a satisfactory job as when riveted to the boiler. The waterway mid-feather adds to the total efficiency of the boiler, but it is doubtful whether the gain effected is in full ratio with the increased cost. If waterway mid-feathers are used, it is very necessary to order them to the position required, otherwise they will be most probably placed, as at Fig. 83, which in the writer's opinion is not so good as placing them as Fig. in. The position of the mid-feathers, i. e. the height at which they are placed, needs to be considered -with the view of getting the best work from the fuel expended. It has been most commonly the practice to place these feathers at right angles to the sides of the boilers at the point where the curve commences, as at Fig. 83, just referred to ; but the ultimate effect can certainly be increased by placing them higher up, giving more surface for the heated products to act upon immediately they leave the fire, instead of devoting more space to the top flue, where the heat does less work, and is to a great extent expended when it reaches there. In the illustration now under discussion (Fig. in) the feathers are shown fairly high, but they might advantageously be placed just a trifle higher than this, as Fig. 113, so as to leave the top flue barely larger than the two side flues. This will have a judi- cious choking effect to the top flue and help to bring the heat into more effectual contact with this surface, which so usually escapes to a great extent by reason of all heated gases having a tendency to keep clear of surfaces beneath them if there is sufficient room to permit it. Fig. 113. 192 Warming Buildings by Hot Water. Fig. 114. Occasionally a workman will be found carrying the front end of his mid-feathers down a little way at right angles, as Fig. 114; this has a good effect in causing the flame to spread itself more over the side surfaces, as with a high mid-feather, the flame and gases always seeking the highest possible point, and the draught al- ways taking the very shortest and nearest passage it can, partly prevents the lower portion of the boiler sides being acted upon, as the flame would be found to pass rather closely under the mid-feathers if this turned down portion did not exist. Of course this improvement is not a necessity, but an improvement it really is, and adds a trifle to the total efficiency. The feathers must not be turned down very far, or they will interfere with the proper cleaning of the boiler (flues) outside, which is particularly necessary if the fuel, or any part of it, is coal. Before leaving these side flues it is desirable to point out that there is a point at which the return pipe (or pipes) should enter so as not to cross the flue, and, firstly, be no obstacle to the soot 'or flue-raker, and, secondly, be no means of checking or reversing the cir- Fig. 115. . culation, as putting the return pipe in a highly heated place would be likely to do. The point referred to is low down in the side (as usual) at the back ; at this point the return pipe can be neatly covered with brick and cement work, as Fig. 115; this obviates both the objections named. Nearly every boilermaker's illustrations show the return pipes connected into the middle or towards the front, but the back is decidedly the best in every way, as Boilers for Brick Setting. 193 it does not block the flue. If Fig. 1 1 1 is referred to, it will be seen how awkwardly the return pipe would be placed, if we suppose it to be brought in anywhere near the front.* The arrangement of flues at the back of the boiler has already been referred to, but it is necessary to deal with it further, so as to make it clear how this part of the setting is carried out, for it is perhaps the most difficult point to those who have no experience. It has been explained (p. 188) that, in addition to the fire-brick bridge, which reaches from the bottom to about half way up the back of the boiler, there is another bridge carried across just above this with the view of stopping all passage of flame directly into the chimney above, and so causing it to pass around to the sides of the boiler beneath the mid-feathers. The construction of this upper bridge requires both care and skill, as although it is a common practice to carry this brickwork straight across, support- ing it on iron bearing bars, as Fig. Fl &- II6 - 1 1 6, this is in the end a very unsatisfactory arrangement, as the bars must some day, sooner or later, be affected by the heat and gradu- ally give way, and by this gradual collapse, choke, and eventually stop the passage - way between the two bridges in question. Hood recommended a solid fire-lump for this purpose, as Fig. 117, which is his original illustration of the back of the boiler with the bridges in situ. Fire-lumps, however, are hardly practicable for large wide boilers on account of the expense or difficulty in getting them when the work is away from large towns (as it usually is). The upper bridge can be better made of fire-bricks, without a bearing bar, by making it arched, as Fig. 1 1 8. This arch should commence on a level with the feathers, these being * It is desirable to keep the flow and return pipes as far away from one another as possible, as this prevents to a great extent collections of sediment and other objections to be explained directly. O i 9 4 Warming Buildings by Hot Water. brought right through just below it to as far as the back brickwork ; and supposing this arch bridge to rest on the edge of the feathers, as this explanation suggests, then they Fig. 117. must be well supported by brickwork gathered out from the back, as Fig. 1 19. It will be noticed from Fig. 1 18 that the top of this arch-bridge is level with the top of the boiler ; this Fig. 119. Fig. 1 1 8. permits the top flue to pass right over it, supposing the chimney to be quite at the rear ; but when the chimney starts Boilers for Brick Setting. 195 away from the top, as Fig. 109, this bridge is sometimes carried over, resting on the edge of the boiler, as is shown there. A little better joint between the boiler and brickwork is effected this way, but it is not the best plan if the chimney starts upright at the back, although it could still be done then. In this drawing, Fig. 109, the bridge in question is made by bricks placed lengthways from front to back, about i inch resting on the boiler, and 2 inches in the brick- work at the back. This leaves a 6-inch space, which is sufficient with moderate sized boilers, but it might advantage- ously be made 8 inches in the larger sizes. Roominess at this point, from front to back, is desirable ; at other points it is objectionable, as explained. The pit in which the boiler is situated can be either of brickwork or concrete, and sometimes they are lined with iron, but with none of these materials can the pit be kept dry if the drainage is shallow ; that is, if water is found in the earth at a higher level than the bottom of the pit. This necessitates the use of special shallow boilers (see p. 204) unless the house which the boiler is to heat is by some unusual circumstances raised up somewhat. In any case, every effort should be made to drain the pit, as even with good ground water may find its way into the pit from various causes, and as the pit is very commonly in an exposed place provision to shelter it from rain and general inclement weather, must be made. In building in the pit it must be made of such a size as to admit of the stoking tools being used freely, although shift could be made as regards this if absolutely necessary. The size of the pit is governed by the size of the boiler, and on this account, if the situation of the pit is peculiar, thought must be bestowed upon what space the boiler may be allowed to occupy. A " blow-off " cock for emptying purposes must be provided from the boiler in the pit, and, as explained, the plugged pipe ends should appear in front, see Fig. 86, so that the accumulated sediment in the boiler can be disturbed with rod or cane inserted through these pipes. O 2 196 Warming Buildings by Hot Water. Fig. 1 20 * shows the front in a finished state as it appears in the pit, with sweeping doors opposite the two sides and the top flues, the flow and return pipes, and the damper in the chimney in place. Fig. 120. All the brickwork that is acted upon by the flame and heat should be built up in good quality firebricks. The other brickwork that is not acted directly upon by the heat can be of the ordinary character. The arch that is carried over the top of the boiler, corresponding in radius with the boiler top, is very commonly made by first building the sides up to the mid-feathers, then, after fixing these in position, the boiler top is covered with ashes or dry earth to a depth that the flue is to be, say 4^ inches, then the bricks are carried over, resting on this material, which is afterwards raked out when the brickwork has set. This is a most simple way of making the arch without the use of special appliances. The iron furnace front is secured to the brickwork by clamps, but inserting these in the ordinary way is not always * Also kindly loaned by Messrs. Jenkins & Co. This illustration does not show the cleaning plugs that should appear in front. Boilers for Brick Setting. 197 sufficient to keep the front soundly secured, the general effects of the heat tending to loosen it. Some fixers will have clumps extended from the furnace front right through, and clipping round the rear end of the boiler ; this usually makes a good job of it, and it can be taken as fair evidence of skilled workmanship if the furnace front keeps sound and tight against the front brickwork after the boiler has been in use a little time. There are variations to the method explained for setting saddle boilers. Some engineers consider that better results are attained by first carrying the flame over the top of the boiler from back to front, immediately it leaves the interior, and causing it to descend and pass along the sides under the mid-feathers to enter the chimney. This arrangement has merits probably, or it would not be resorted to ; but the writer has not discovered them, and certainly the results cannot be so satisfactory as by the method which has been fully explained, and which has by far the major shs^ of approval. The particular objection to it in the writer's eyes is that it devotes the best services of the flame and heat to the top of the boiler, where it has the least useful effect, even supposing it was kept scrupulously clear of ash-dust and such matters. Sometimes a workman will bring his mid-feathers right up to the front end of the boiler and make provision for the flame to pass from the lower to the top flue by a recess in his front brickwork opposite the feather ends ; no particular gain results from this, if anything it interferes somewhat with the removal of soot or dirt from the top flue unless other soot-doors were provided, it being swept down into the lower flues in the usual way. It was explained on p. 187 that from the lower edge of the furnace door, right across the fire-bars to the back was an exact level. This is not always the case, as sometimes a fixer will make his dead plate slope down towards the fire-bars, so that the bars and the bottom of the boiler resting upon them are below the bottom edge of the furnace door, perhaps 198 Warming Buildings by Hot Water. three inches, reducing the height of the ash-pit to this extent. This arrangement is usually resorted to only when it is desired to keep the boiler as low as possible, or, in other words, to work in the shallowest pit that can be used efficaciously, and for this purpose the method is a good and practical one. The chimney, if brick, should not be less than 9 by 9 inches (inside) for moderate sized boilers ; for the largest sizes 14 by 9 or 14 by 14 is desirable. A very common error is fallen into in making chimneys too' small ; these will be dealt with fully under " Chimneys," on a later page. There remains to be mentioned that occasionally it is desired to use water-bars to the furnace instead of the ordinary solid bars ; and in this case the return pipe or pipes do not enter the boiler at all, but enter the box end of the bars in question, and from thence circulating into the boiler, as here shown (Fig. 121). These Fig. 121. bars keep more free from clinker than the ordinary solid bar, as they are al- ways kept at a lower tem- perature by the water with- in them, and they add to the heating surface to a fair extent, though not so much as would be the case if they were always clear of ash, which, however, cannot be expected. Commonly, the returns are brought into the front box end of the water-bars, as shown, and this is the best ; but, instead of their bringing the connecting pipes into the front end of the boiler they might just as well enter the back,* so as to be no obstacle in cleaning the flues. The pipes forming the bars are cast much stronger, heavier, than the pipes used for radiating purposes, they are also smaller. * The positions that the flow and return sockets occupy on nearly all illustrations of boilers in the makers' lists is the flow near the back end Boilers for Brick Setting. 199 They cannot be cleaned out ; their strength, however, goes far towards saving them from ill results, even supposing they became solid with deposit. The first improvement on the saddle boiler was in making it with a waterway check end, as Fig. 122. This was a decided gain by adding considerably to the direct heating surface, and also to the flue surface at a point where the heat has its greatest effect after leaving the fire-box. This in no way affected the labour in fixing, except to lessen it a trifle, and the cost is increased to but a reasonably small extent if we compare one of these with an ordinary saddle of similar power (not similar size). Fig. 122. Fig. 123. The effectiveness was further increased by putting a water- way front to the boiler (as well as a waterway end), as Fig. 123, but this introduced a new feature that had to be provided for, viz. the inability to attend to the fire at all successfully from the front, as the furnace door gave but little access to the fire-box, except for raking out clinker, &c., and therefore a door for feeding or banking up had to be placed elsewhere ; this is best if put in the top, as shown at Fig. 101. and the returns near the front, the contention being that this arrangement causes the water to circulate more uniformly through the boiler, entering one end and passing out at the other. The contention is a good one, as it will prevent as much as possible large accumulations of sediment occurring in certain parts of the boiler, and it will also prevent any violent internal circulations taking place ; but for general purposes it will be found better to have the returns entering the back and the flow off the front at top. 2oo Warming Buildings by Hot Water. This form of boiler is in character with Hood's standard of efficiency, and even at this moment it is considered, and worthy of being considered, good, and capable of giving good results, although of course there are many new features since introduced that go to increase efficiency without materially increasing size. Perhaps, one of the earliest ways of adding to the effec- tiveness of a boiler of any description (saddle, Trentham, or vertical) was the addition of one or more cross tubes, as Fig. 1 24 ; * these are wholly direct heating surface, and being Fig. 124. in, or nearly in contact with the glowing fuel, a very decided gain in heating efficiency is effected. This can be readily judged from a maker's catalogue, in which this boiler, 36 by 1 6 by 1 6, is listed to heat 1050 feet of 4-inch pipe, and a plain saddle boiler to heat this same quantity requires to be 48 by 1 6 by 1 6, one-third longer than the other. It is, however, not particularly desirable to introduce these cross tubes unless it becomes from some cause necessary ; and for small works it is better to have a plain boiler, the cross tubes being merely one of the different devices for adding to the power of the boiler without making it of unwieldy size.f * From the catalogue of Messrs. Graham & Fleming of Halifax. f If the writer is found to speak in greater favour of one boiler than another, it is not intentional ; all the boilers being noticed have some good features of their own, and none are introduced that have been found defec- tive x>r practically weak, it also needs to be mentioned that no one can Boilers for Brick Setting. 201 Fig. 125 * shows a further addition to the saddle boiler, in the top flue way, which is within the boiler itself, and does not come within the category of the top flues deprecated by the writer when speaking of the value of flue surfaces, and again Fig. 125. later under the heading of " Saddle Boilers." This top flue allows of the flame and heated gases coming beneath a water surface, and by this means we get the most efficient of all flues, giving better results than the vertical side surfaces. Several makers' lists show this boiler in section with the flame travelling through this flue from back to front, and then passing from the front over the top of the boiler to the chimney, as Fig. I26,t the object of the illustration (in the catalogues) safely recommend one boiler to the exclusion of all others, as many of about an equal degree of efficiency are made, and, consult as many authorities as you will, they will all differ to some extent as to the merits of different kinds. Again, architects who have to deal with heating works, have different ideas as to what should be specified, some going so far as to design new boilers for their own purposes ; and all these differ- ences in opinion of course account for the really vast variety of boilers that are now put upon the market. It is also peculiar that certain patterns will occasionally be sought after very greatly for a short time and the demand then cease, and some other pattern have the increased call. Certain patterns, furthermore, are favoured in certain localities. * From the catalogue of Messrs. Lumby, Son, and Wood, Limited, Halifax. t This boiler is made with or without a terminal end, but the former is much to be preferred, as illustrated. 2O2 Warming Buildings by Hot Water. being to show the method of fixing. Now, with an ordinary draught in the chimney there is no objection whatever to carrying the flame * down from the front and back along the Fig. 126. Fig. 127. two sides, using a vertical feather, as Fig. 127^ This illus- tration shows a similar boiler with waterway front, neces- sitating the top feeder which is carried through the flue-way, as shown. It must not be forgotten in setting these to provide the sweeping doors opposite the flues, as described with the saddle boiler, and one is particularly needed opposite the top flue-way through the boiler, as a deal of dusty matter will be deposited here from coke, or soot from coal. The boiler just illustrated has a large demand, as it is very powerful, and has no objectionable features ; it is also well suited for shallow drainage, and is economical of space for the results attained. Fig. 128^ is another powerful boiler, resembling in some respects the last one, but having twin flues at top instead of the wider single one. A peculiar feature in this boiler is the * The word flame is used very freely, and it is feared in instances where it would be literally incorrect ; but it is a more convenient word than "heat " or "heated gases," when dealing with flues, even though it may apply to a furnace burning coke and producing no actual flames. t The " Colonial," from the catalogue of Messrs. Graham and Fleming, of Halifax (England). J The " Climax," from the catalogue of Messrs. Hartley and Sugden, of Halifax (England). Boilers for Brick Setting. 203 pieces stopped out of the front termination of the top flues, which permits of the boiler being butted tight up against the brickwork in front, thus decreasing in a consider- able degree the labour in fixing. The brickwork is also brought down close to the top, the top surface not being used (the makers recognising the useless- ness of this surface). Fig. 129* shows in section the simple way in which this boiler is fixed. The neces- sary soot doors must not be forgotten. Fig. 129. Fig. 1 30 f is another boiler, adapted for shallow drainage, and of a powerful character, but from the illustration it will * From the catalogue of Messrs. Hartley and Sugden, of Halifax (England). t The " Imperial," from the catalogue of Messrs. Graham and Fleming, of Halifax (England). 204 Warming Buildings by Hot Wafer. be noticed that the flame is carried both to and fro in flues within the boiler, and then to and fro along the outside, as shown by the mid-feather. This necessitates having a chimney with a stronger draught than the preceding.* Fig. 1 3 1 f is a Fig. 130. Fig. 131. transverse section of this boiler, showing its internal shape and also the method of setting. The flame when it leaves the fire enters the two lower side flues without leaving the boiler, and from these it is caused to enter the top flues at the front, and from these top flues it is conducted outside at the back, passing under the mid-feathers, then back over the top. Perhaps the shallowest boiler at present made for difficult drainage is as Figs. 132 and I33,J its power being obtained by the increase in width instead of height. This is a terminal end boiler, and the arrangement of the flue-ways at the end cause the flame to impinge upon the upper surface imme- diately beneath the flow-pipe. This must more effectually induce circulation when the apparatus is first started, and at any time a good result is attained by causing flame or heated products to impinge and come in contact with the boiler * A taller chimney, see Chimneys, t Also from Messrs. Graham and Fleming's catalogue. J The " Delta," from the catalogue of Messrs. R. Jenkins and Sons, of Rotherham. Boilers for Brick Setting. 205 plates ; this is the object of the "bridge" inside horizontal cylindrical boilers. This must close the list of horizontal plate boilers. Amply sufficient has been shown to make clear the general features Fig. 132. Fig- 133- that at present exist in these, and although it is no exaggeration to say hundreds of other shapes would be found if all the dif- ferent makers' lists were collected, there is a great similarity in the majority of them to some of those just described, and we can therefore now describe those that have some peculiar and novel features, and which entirely differ from those just treated, which are generally recognised as ordinary boilers. It must never be overlooked that the greater the length of horizontal flues the higher the chimney must be, and the more the flues turn to and fro the greater strength of draught and corre- sponding height of chimney is needed. This is often of con- siderable importance, as in so many situations a tall shaft is by no means admissible, and an increased natural draught cannot be obtained except by increased height of chimney (see Chimneys). Fig. 1 34 * shows a boiler that is considerably in favour and is of a decidedly powerful character, presenting, as it does, all possible direct heating surface to the fire (except what can be * The " Excelsior," from the catalogue of Messrs. Lumby, Son, and Wood, Limited, of Halifax (England). 206 Warming Buildings by Hot Water. gained by cross tubes, &c.), and having almost the whole of its outer surface enveloped in flame when in use. The shape of this boiler particularly adapts it for with- standing a heavy internal pressure, as is always obtained with an apparatus that may extend up three or four floors of a high building (never in ordinary horticultural works), in which case it is not advisable to use the simple type of saddle Fig. 134- Fig- 135- boiler as it would probably bulge out in the middle, inside, and be ruined, perhaps even before the fire was lighted, as the pressure becomes enormous in the boiler of an apparatus that extends to any considerable height, and which the cylin- drical shape is best able to withstand (see p. 255). This argument, however, does not apply to cast-iron boilers. Fig. 135 * shows the method in which this boiler is fixed. The flames and heat from the interior pass out by way of the grated opening near the top, as shown. The grating is provided to prevent the fuel falling through into the flue, the boiler being specially adapted for filling with a full charge of fuel. The flame is then caused to pass down the sides beneath the mid-feathers, then up again into the chimney at back ; the top surface of the boiler is not made use of. This boiler can be had with waterway mid-feathers if desired. * Also from Messrs. Lumby, Son, and Wood's catalogue. Boilers for Brick Setting. 207 Fig. 136* is an ingenious form of boiler that has now been in use for a considerable time, and survived all the criticisms and trials that a boiler is subjected to during the few years of its existence. This is a cast-iron boiler made in Fig. 136. segments and bolted together, the particular features being the large direct heating surface obtained, by what are practically deep convolutions, and the very good way in which the heat is allowed to pass from the furnace outside to reach the chimney. It will be seen in the illustration that where the sections meet at the sides provision is made for a slot-shaped opening to come at every joint, extending from near the bottom to the point where the rounded top of the boiler commences. When the boiler is in action the flame passes out through these slots and, presuming the chimney to be at the back, as usual, the whole of the outer surface receives the full effect of the heat. This tends to simplify fixing, as the front and back are butted tight up against the brickwork. Figs. 137 and 138! will illustrate this, but in these two drawings the boiler is shown fixed with water-bars to the furnace. * From the catalogue of Mr. J. G. Wagstaff, of Dukinfield, near Man- chester, t Also from Mr. WagstafPs list. 208 Warming Buildings by Hot Water. This boiler is also made in an independent form, and to some of the patterns in which they are constructed a top feeder can be applied. Fig. 137' Fig. 138. Fig. 1 39 is a form of boiler that is gaining favour, as it has been subjected to some severe trials in competition with others, and gained favour. This is a coil boiler, but differing from those previously referred to in the Fi S- '39- fact that it is in every way ad- r~ "^ ~fl apted for large works. This coil f~ jj is of cast iron built up in sections, ( j but presenting in other ways the ( ) same appearance as one of C . ) P rv wrought-iron pipe. It will be C ymJ noticed that the pipes forming the coil are set down close together without any passage way or space between them for flame or heat to pass through, and this constitutes one of the chief features in the patent of which this boiler is the subject, as from a considerable experience that the inventor had (perhaps more than any other water engineer) with coils and coil boilers, it was found that by preventing egress of flame through the sides of the coil but conducting outside with flues with three or four vertical mid-feathers, a considerable improvement in results was effected, chiefly in this instance, by preventing such a very free escape of useful heat into the chimney as takes place Boilers for Brick Setting. 209 with the open coil with a powerful furnace, an effect that is, however, considerably modified with the small independent coil boilers. By closing up the coil we certainly get a larger surface in contact with and near the fire than we could do with an open coil, and this undoubtedly has gone far to make this boiler more efficient. The usual method of fixing this boiler is to arrange for the furnace to be within it and to lead the flame out at the top to pass up and down the outer surface by vertical mid-feathers. The heated products escape from the interior by a flue way at the top of the boiler, and then, by the feathers provided, it is led up and down the boiler, finally escaping by the chimney which leads off at the back. These are very com- monly fixed with a sort of auxiliary flue leading direct from the furnace to the chimney, to draw up the fire quickly when lighting, &c., this flue being closed by a damper when the fire is fairly established. In fixing this boiler an arrangement for feeding at the top is necessary ; the customary emptying service is needed, and particular care should be given to the easy cleaning out of deposit. The size of the pipe constituting the coil is 3 inches, a suffi- ciently full size, and it has to be said in favour of this boiler that the argument as to water staying about the flat top surface of some boilers is entirely disposed of, as there cannot possibly be any check to the free passage of water to the pipes in this case. The argument referred to is that in some square-shaped boilers a rapid circulation goes on within the boiler itself, and only a proportion of the heated water passes at once into the pipes instead of all of it. This contention, however, carries but little weight, and the disadvantage (for it certainly exists, as can be noticed with any experimental apparatus) is so trifling in actual practice as to be hardly appreciable (except at first starting), not even with the squarest-topped boiler that is made. This boiler is usually fixed upon and connected with water-bars of a shape to permit of the stoking tools passing under the lower edge of the boiler, which could not be done with the ordinary flat bars in this instance (see Fig. 140). P 2 JO Warming Buildings by Hot Water. Fig. 140* illustrates a special form of tubular boiler which has seen a deal of service, and is still in regular demand. The illustration clearly shows the construction of this, render- ing much description superfluous. Fig. 140. This description of boiler is always arranged for top feeding, the conical shape making it very suited for this, as there can be no great risk of the charge of fuel " bridging " up, instead of gradually sinking as the lower part burns away. * From the catalogue of Messrs. J. Weeks and Co., of Chelsea, London. Boilers for Brick Setting. 21 1 The conical shape, however, has its chief use in increasing results by overhanging the fire, the arrangement of the tubes being such (as to spaces between them, &c.) that they receive efficient contact with all heated products. Most of these boilers, particularly those of smaller size, are made differently to the one illustrated, in the fact that they do not consist of two distinct halves as this one does ; this division, however, only being for convenience of transport and passage into cramped positions. The illustration shows the boiler set on to and connected with water-bars, the dipped shape of these latter being necessary to admit of stoking, which could not be readily done otherwise. The return pipe is shown brought into the water-bars as is customary. The setting of this boiler is effected by enclosing the boiler in a circular surrounding of brickwork corresponding with the shape of the boiler, but a little larger, the top being finished off flat with the feeding door in it, and the chimney being carried off as near the top as possible, with a feather placed to prevent the too direct escape of heat. This description of boiler can also be had of saddle and horizontal square shape, but the upright conical shape has the most favour. With ordinary care they are very lasting ; the makers' list offers a guarantee for ten years. It is a cast-iron boiler. This shape, and all boilers of a circular form, are best cleaned out with a chain. A wire is first passed round, and once this is got through, the chain can easily be made to follow. Fig. 141* illustrates about the most powerful form of boiler that has yet been made for hot-water circulation. This should have been classified with the independent boilers, as it is wholly independent of brick-setting, but it is very much removed in both size and character from the independent * " The Python." From the catalogue of Mr. James Keith, Holborn Viaduct, London. This boiler is so named, as it can be lengthened or contracted by increasing or decreasing the number of sections. P 2 212 Warming Buildings by Hot Water. Boilers for Brick Setting. 213 kind, and it should be surrounded with brickwork, or some low conducting material, to prevent the great loss of heat that would otherwise occur, as the boiler is water-jacketed every- where except the front* It will be noticed that the particular object aimed at with this boiler is to get the utmost possible direct and semi-direct heating surface, and by this means to render the boiler practi- cally independent of the (comparatively) little additional help it would obtain from outer flue surfaces. This end, it is needless to add, is fully attained in the boiler illustrated ; but if it were not that it had been made and subjected to con- siderable use for some time, the apparent complexity of its construction would suggest caution in speaking of it ; in this case, however, the boiler has had every test possible, and has come out successful. The troublesome features which a boiler of this kind introduces to its manufacturer are, firstly, the mathematically correct allowance necessary for expansion and contraction (for a very little variation in temperature would show results with the long tubes of this boiler), an allowance which needs the utmost care in a large boiler, and particularly in a cast-iron one (as this is), which has such rigid surfaces. Secondly, there must be a simple means of cleaning it from soot or dirt, which so quickly decreases the value of the heating surface ; and there must also be, very importantly, a means of cleaning dirt and incrusted deposit from its interior.! * There are but two flow pipes shown on this drawing : it would be better were there three or four, as such a rapid heater should have every provision for its water to pass off rapidly. All large boilers should have two or three flows, or (if particularly convenient) one or two of larger size. One flow is not usually sufficient for a rapid heating boiler of any size. t It may be mentioned that a boiler like this, heating perhaps up- wards of 10,000 feet of pipe, must cause a deal of water to be evaporated, which, of course, necessitates the introduction of fresh water, and adds to the hard lime deposit ; so provision must be made not only for flushing, but also for scraping out, as although an " anti-incrustator " fluid would be used with a boiler like this, the deposit in its loosened state would still have to be removed. If the boiler was used for heating water for sup- plying public baths, c., then the question of incrusted deposit would be a serious one. 214 Warming Buildings by Hot Water. This boiler has provision made for both of these last- named works, and its sections are also ribbed outside, so as to permit of the ready application of any boiler-coating com- pound to prevent loss of heat. The metal of the tubes is about f inch thick. The automatic damper in connection with the chimney is an ingenious arrangement, much upon the principle of an Arnott's ventilator, as it can be set to work with any strength of draught. Its action is brought about by the fact that the up-current of air in a chimney is due to difference in gravity or weight between the outer cool air and the heated air in the flue, the latter being made to ascend by the pressure exerted by the superior weight of the latter (see Chimneys). Now this pressure is, in the usual way, only exerted at the lower end of the chimney through the fire-box ; but if we cut a hole in the flue somewhere a little way above the stove, we shall find that the cold air will instantly push itself (so to speak) in the aperture with a deal of force, so that if we fixed a balanced door at this point, the outer cold air would have sufficient force to make it swing open to give it entrance, and the stronger the draught in the chimney, the greater force the outer air will exert in entering (by reason of a greater volume being required in the chimney), causing the door to open wider ; and the weaker the draught, the less the inflow of air, and the door will incline to swing shut proportionately with the feebleness of the current of air passing in. The particular utility of this valve is that when the fire is out or low, the draught is at its least, and the door remains shut ; but if the fire becomes fierce (through inattention), the draught by the great heat evolved becomes stronger, and the door gradually swings open, \ permitting air to enter the chimney without passing through the fire, thus checking and decreasing the passage of air through this latter direction, and so automati- cally regulating the speed of combustion, as the combustion is wholly controlled by the strength of the draught through the fire. This valve, in fact, acts as a governor, and it can be " set " so as to permit of a certain speed of combustion being Boilers for Brick Setting. 215 attained before it opens. The Arnott's valve is of particular use when fixed in a kitchen chimney breast, as it will automatically regulate the working of the kitchen range, instead of its regulation being dependent upon the partial closing of the dampers, which is never done. There remains one more boiler to be noticed, as it has done enormous and long service, and in many cases is now found advantageous in use, notwithstanding the variety of new patterns designed since its introduction. This is the Trentham or Cornish boiler, Figs. 142 and 143,* elevation and longitudinal section. The large amount of room this neces- sarily occupies is an objection sometimes, but for many years it was considered very economical in fuel, and this doubtless Fig. 142. has prolonged its use ; but it is doubtful whether, with all its years of useful service, it will be in demand much longer, as its economical features are now outdone by several of the newer patterns. This boiler is very commonly fitted with cross tubes, behind the fire box ; and immediately behind where the fuel rests there is provided a " bridge," a raised part which causes the flame and heated gases to impinge upon the upper surface inside. The sectional drawing shows the boiler as having a waterway check end, which again adds to the total effective- ness, as has been explained. The flame is, after it leaves the interior, conducted by means of flues to and fro the length of * From the catalogue of Messrs. R. Jenkins and Co., of Rotherham. 2 1 6 Warming Buildings by Hot Water. the boiler, some engineers preferring to first carry the flames under the boiler, and then to pass along the top to the chimney ; others first carry the flame over the top of the boiler, and then along the bottom to the chimney, much in the same way as explained with the saddle boiler. Each has an argument in favour of its respective way, but in actual results, there is not the least doubt, for the reasons Fig- 143- several times mentioned, that the former method is best. There are sweeping doors for the flue ways at top and bottom of the fire front, as shown in both cuts. This is another boiler that should have two or more flow pipes leading away from it ; it is of too large a character to have all its water pass away up one pipe, unless it was of large size. CHAPTER X. APPLIANCES AND FITTINGS FOR HORTICULTURAL WORKS. Hot-water pipes and fittings Price list Jointing pipes The rust joint Red and white lead joint Rubber ring joint Improved expansion and other joints Stop valves and their uses The throttle valve The .slide valve The medium screw valve The reliance valve- Furnace fittings. A PECULIAR source of annoyance and trouble occurs with ordinary cast hot-water pipes, by reason of the varying thick- ness of the substance of metal in the castings, and the differ- ence is particularly noticeable between pipes and fittings, the former almost invariably being lighter or less in substance than the latter ; and it is to be presumed that either the moulders at the foundry are paid differently for pipes than for fittings such as paying by the piece for pipe and by weight for fittings or it is a sign of careless work in the mould- ing shop and a proportionate waste of material, as nothing is gained by the fittings carrying this surplus metal, and it is a constant source of trouble by reason of the work it occa- sions in making joints. Sometimes there is a f-inch space for the joining material, sometimes the spigot end of the pipe will only just pass into the socket, and this is particularly unfor- tunate with the rubber ring joints, as will be learnt directly. Another ill practice that has become a little prevalent is that of issuing pipe insufficient in diameter and weight No doubt it is brought about by competition, and it never need be feared with any firm of good standing. A 9-foot length of 4-inch pipe should weigh 98 Ibs.,* and its size, 4 inches, is internal diameter in the pipe portion (not in the socket). This pipe differs considerably to cast smoke pipe and to * See Appendix. 2 1 8 Warming Buildings by Hot Water. the pipe used so extensively for conveying the rain water from roof gutters to the ground, both these latter being of a much lighter quality ; and, as a rule, the pipe for hot water is cast from different metal of a somewhat finer quality. Nearly every make of hot-water pipe has two or three (usually three to a 9-foot length) bands or rings cast round the diameter of the pipe, one at the opposite extremity to the socket, and two at equal distances between. The socket is considerably larger than the pipe (compared to the other two qualities of pipe men- tioned), so as to admit the ringed spigot end and give suffi- cient room for the jointing material and the tool with which it is caulked. It has no flanges for securing it to wood or brickwork like the rain-water pipe. The socket should be particularly strong, with two cast rings formed round it and with strengthening bars between them. The different varieties of patent joints, expansive and other kinds, will not, of course, be found to answer to this description correctly, but they should be equal in strength and quality. The following list comprises all the fittings in general demand, and is compiled from the catalogue of a well-known firm, and the prices shown may be considered as the average cost of these goods of a satisfactory quality. PRICED AND DESCRIPTIVE LIST OF HOT-WATER PIPES AND FITTINGS OF THE ORDINARY KIND. (These prices are subject to a discount to the trade.) Hot-water pipe, 9 ft. lengths 6ft. 3ft- spigot or coil pipes, 3 ft. 6 in. to 7 ft 2 ft. to 3 ft. ,, ,, 6 ft. to 9 ft. Trough pipes, 9 ft. lengths, troughs 4 in. wide 6 in. 9 in - Loose trough, 2 ft. 6 in., to fit on pipe Evaporating trough, 6 ft. x 15 in. X 7 in. deep. 2 in. 3 in. 4 in. 2/ 2/6 per yd. 1/4 2/ 2/6 1/6 2/2 2/8 1/4 .- 1/6 2/ 2/6 3/8 5/6 6/6 6/9 8/ 8/6 10/4 2/10 3/6 4/8 each. Appliances and Fittings for Horticultural Works. 219 No. 2 in. 3 in- 4 in. i. Elbow, i socket, ist row 1/6 2/5 3/o each. 2. ii || 2nd ,, 2/8 3/8 4/6 ,, 3. 7rd 6/4 8/0 4. 3 4th / T^ 8/ / 10/9 5. cth IO/4 6. ii 2 sockets, *J ist }} >B 1/9 * / *T 2/9 3/7 11 7- 11 ,, 2nd ,, 3/ 3/10 4/9 ,, 8. ,, ,, 3rd ,, .. 6/8 8/8 ,, 9. 4th 8/6 1 1/ 10. cth 10/7 14/7 ii. ,, no sockets, D ist 5> 1/6 2/5 TV O 3/ ii 12. ,, ,, 2nd ,, 2/8 3/8 4/6 ii 17. 3rd 6/4 8/ J 14. *) 4th / T^ 8/ IO/Q 9 9 15. {-111. Cth " / 10/4 / s 9 9 1 6. ii |th circle, I socket, 1st row .. 1/9 3/2 4/ 99 J 7- 99 > 9 ,, 2nd .. .. 2/3 3/7 4/9 99 18. ,, ,, ,, 3rd .. .. .. 6/4 8/ 99 19. ,, ,, ,, 4th .. .. 8/ 10/9 ,, 20. 99 || ,, 5th .. .. .. 10/4 I4/ 11 21. ,, ,, 2 sockets, ist , 2/ 3/4 . 4/4 ,, 22. ,, II ,, 2nd .. .. 3/2 4/9 5/8 ,, 23- ,, ,, ,, 3rd .. .. .. 6/7 8/3 ,, 24. ,, ,, ,, 4th ,, .. 8/3 1 1/ ,, 25- ,, 99 ,, 5th .. ., 10/7 H/3 ,, 26. ii |th angle, I socket, ist .. .. 2/3 3/4 4/6 n 27. 99 ii ,, 2nd .. .. 3/3 4/4 5/6 ii 28. 99 reducing, 4 * 3 in- ist , .. .. 3/w ' 99 2 9 . 99 ii 4 X 3 9, 2nd .. .. 5/8 91 30. 99 ,, 4 X 2 ,, ist ,, .. .. .. .. 3/ic 1 > 31- ,, ,, 4 X 2 ,, 2nd .. .. .. .. 5/8 || 32. ,, ,, 3 X 2 ist .. .. .. 3/ .. II 33- ,, ,, 3 X 2 ,, 2nd .. .. .. 4/ 99 34- 99 > j 3 X 4 99 ist .. .. .. .. 3/*o 99 35- 99 ii j x 4 99 2nd .. .. .. .. 5/8 99 36. 99 ii 2 X 4 ,1 1st ,, .. .. 3/10 99 37- 99 99 2 X 4 ii 2nd .. .. .. .. 5/8 99 38. 99 99 2 X 3 99 ist , .. 3/ .. ,, 39- ,, 2 X 3 2nd , .. 4/ .. ,, 40. Offset , i socket, 3 in . projection 2/IO 4/6 6/ 99 41. II > 9 6 11 2/10 4/8 6/4 99 42. ,, ,, 7i ii 3/6 5/4 6/8 43- ,, ,, 9 ,, 3/6 5/4 6/8 || 44. ,, ,, 12 ,, 4/ 6/ 7/3 J> 45- 99 2 sockets, 3 ,, 2/10 4/6 6/ ,, 46. ,, ,, 6 ,, 2/10 4/8 6/4 99 47- J5 99 9 ,, 3/6 5/4 6/8 II 22O Warming Buildings by Hot Water. No, 2 in. 3 in. 4 in. 48. Offset, twin, I socket 3/8 6/ 7/6 49- 3/8 6/ 7/6 50. ,, ,, 2 sockets O/ 4/4 6/6 8/6 51. 95 55 55 ' 4/4 6/6 8/6 52- ,, reducing, 12 in. projection, 4 x 3 in. .. 8/ 53- 4X3 .. .. 7/6 54- 5, ,9 4X2 .. 8/ 55- 99 99 ,9 4X2 ,, .. 7/6 56. 59 99 9> 3X2 ,, .. 6/ .. 57- 99 99 9> 3X2 ,, .. 5/8 .. 58. Syphon, open 2 way 2/3 3/8 4/6 59- ,, close 2 ,, 2/3 3/8 4/6 60. 7 , 4/6 7/8 9/10 61. 99 99 499 9/10 13/6 62. 7/3 1 1/9 1 6/3 63. 6 8/6 13/6 1 8/6 64. ,, elbow, spigot outlet, 2 sockets .. Of 6/ / 65. 99 9 9> 3 99 .... 6/ 9/ 12/6 66. 4 99 7/ 12/6 1 6/6 67. 5 9, .. .. 8/6 13/9 i8/ 68. 99 99 9J ^99 .... 9/9 15/3 19/9 69. ,, ,, socket outlet, 3 3/10 6/ 8/ 7o. 4 9, " 6/ 9/ 12/6 71. 5 ,9 - " 7/ 12/6 1 6/6 72. 99 99 9. 6 ,, 8/6 13/9 i8/ 73- 7 99 9/9 15/3 19/9 74- ,, ,, reducing, 4 X 3 in. spigot out. .. 8/ 75- 99 99 99 4X3 99 99 .. .. 12/6 76. 4 X 2 .. .. 12/6 77- ,,4X2 ,, .. .. 16/3 78. ,, ,, ,, 4x2 ,, socket out. .. .. 8/3 79- ,, 4 X 2 .. 16/3 80. outlet, open, 2 way, spigot outlet .. 3/10 6/ 8/ 81 7/IO 6/ 8/ 82. ,, ,, close, 2 ,, spigot ,, O/ 8/ 83. ., 6/ 9 / 12 j 6 O 84. / 7/ si 12/6 1 6/6 85 8/3 1 8/3 86. ,9 99 99 6 ,, 9/6 15/6 / O 20/ 87. ,, ,, ,, 2 ,, socket outlet .. -7/ O/ 6/ 8/ 88. 59 99 19 3 99 99 91 6/ 9/ 12/6 89. 99 4 99 99 99 7/ 12/6 1 6/6 QO. C 8/3 I4/ 1 8/3 .7 V 91. ,9 99 6 .. / O 9/6 15/6 / J 20/ 92. ,, ,, 4X3 in. reducing 8/ 07. 91 99 4X2,, ,, 8/ "O 94. 99 99 3X2,, ,, .. .. 6/ each. Appliances and Fittings for Horticultural Works. 221 No. 95- 96. 97- 98. 99. 100. IOI. 102. 103. 104. 105. 106. 107. 1 08. 109. I IO. Syphon, branch, 2 way, socket outlet i 2 spigot outlet .. .. i 11 3 11 4 , 11 " " i 11 5 11 6 ,, ,, .. .. , ,, 2 ,, socket outlet .. i 11 3 11 11 i 11 4 11 11 i 11 5 11 .... 6 .. .. , chair, spigot outlet , ,, socket ,, , coil, 2 way, spigots i 11 Z 11 11 H piece, close . . . . 2 in. 3/9 3/9 6/ 7/ 8/6 9/9 3/9 6/ 7/ 8/6 9/9 4/ 3/6 4/6 5/ 3 in. 6/ 9/ 12/6 14/6 1 6/6 6/ 9/ 12/6 14/6 1 6/6 6/3 6/6 6/ 7/8 7/8 4 in. 8/ 8/ 12/8 16/9 iS/3 20/9 8/ 12/8 16/9 18/3 20/9 8/2 8/8 8/ 1 1/ 10/4 each. i) 11 11 11 11 in open c/ 7/8 IO/4 112. 117. Cross piece, 2 sockets 4/2 6/4 7/ 8/6 9/6 " 114. to 151. 1^2 >Tee piece, equal and reducing Branch piece 2/3 4/ 3/8 5/9 4/6 7/4 1C -I. 4 / C/Q 7/4 ic/i Reducing nipple 4x3 in 2/7 ice 4x2,, 2/3 itfi 7X2,, 1/8 157- 158. 159. 160. 161. 162. 167 ,, piece, 4 in. spigot, 3 in. socket .. 11 11 4 11 2 ,, 3 11 2 11 11 3 11 4 11 11 > 2 ,, 4 11 11 2 ,,3 7 X A ill 2/8 2/8 3/6 3/6 3/6 3/6 7/6 11 1 6 A 2X4. 7/6 1U 4- 165. 1 66 > 2x3** Blank spigot /6 2/8 /9 11 1 66 cored /8 i/ 1/7 167. 167. 1 68. 1 60 ,, socket or cap cored Union socket or collar i/ 1/2 1/8 1/6 1/6 2/8 2/ 2/3 2/ 3/8 11 I7O 2/3 3/4 4/4 171 socket 2/6 3 / 1/1. 172 2/7 3/4 4/6 I /A I 77 2/7 3/4 4/6 1 /J' 174. 175- Flange and socket elbow, short long 3/2 3/4 4/3 4/6 5/6 5/6 11 11 222 Warming Buildings by Hot Water. No. 176. 177. 178. 182. 183. 184. 185. 1 86. 187. 1 88. 189. 190. Socket for welded boiler ,, over end ,, overside Throttle valve, socket, and spigot ,, ,, 2 sockets H pipe valve, open, I valve ,, ,, ,, 2 ,, 2 in. .. 3/4 .. 3/9 .. 3/6 .. ii/ .. ii/ -. 2 5 / .. 28/6 3 in. 4/6 4/9 4/6 I3/ I3/ 3o/ 35/8 BO/ 30/ 35/8 So/ 34/ 34/ 2O/ 20/ 20/ 20/ 27/ 27/ /5 /5 2/ i/ 4 in. 5/8 e; 5/9 5/6 IS/ IS/ 35/ 42/8 54/ 35/ 42/8 54/ 4i/ 4i/ *5/ 25/ 25/ 25/ 3o/ 3o/ /6 /6 2/6 '/3 ich. i > i i i > i i n 11 >} )> )> > > > 7) J ^ 43/ ,, ,, close, i ,, ,, ,, ,, 2 ,, .. 2 S / 28/6 ,, ,, ,, 3 ,, 43/ T ,, .. 2 .. 28/ .. 28/ .. i6/ .. i6/ .. i6/ .. i6/ .. 2 5 / .. 2 S / /4 191. 198. 199. 200. 201. 202. 203. 2 ,, Diaphragm valve, socket and spigot .. ,, ,, 2 sockets ,, ,, angle socket and spigot ,, ,, ,, 2 sockets Slide valve, 2 sockets ,, socket and spigot Pipe stands, single ,, double Caulking tools, steel ,, iron Indiarubber rings White and tarred yarn Iron borings . . /4 .. 1/6 /9 5/ per lb. /S 9/ per cwt There are several ways of jointing this ordinary descrip- tion of socket and spigot hot-water pipe, almost every hot- water fitter having some special notion of his own as to quantity or the admixture of material, &c., but in general prac- tice it will be found that the methods are confined to three, viz. the iron borings or rust joint, white and red lead, and the rubber ring. With the two former, hemp, yarn, or gaskin requires to be used with the materials named, but the latter is commonly used by itself. It will be understood that although these joints have to be water-tight, they have but a trifling pressure to withstand in glass-house work, very diffe- rent to what the pipe joints experience in a building that has several floors heated from one boiler. It is quite possible to make a sound and lasting joint, where the pressure is so low, with the yarn only. The cheapest joint is that made with iron borings, as the GENERAL IRON FOUNDRY CO.'S CASTINGS-HOT-WATER PIPE CONNECTIONS 163 157 160 154- 97 61 71 84- 89 GENERAL IRON FOUNDRY'S CASTINGS-HOT-WATER PIPE CONNECTIONS MACFARLANE'S CASH N G S H OT- WATER P'l P E CONNECTIONS BM3 HB MACFARLANE'S CASTINGS HOT-WATER PIPE CONNECTIONS Appliances and Fittings for Horticidtural Works. 223 material costs so little ; but in many respects this joint is objectionable, as will be explained. The joint is made by mixing with iron borings (which require to be pounded if very coarse) some sal-ammoniac and sulphur, both in a powdered form, these two latter materials bringing about a chemical change in the borings, causing them to set hard and solid, or, in simple language, causing the borings that are driven into the socket joint to rust up into a solid mass. This rusting process takes place slowly, or rather, it is some time before the chemical action quite ceases, although the joint may be quite rigid in a short time ; but as the change that takes place brings about an expansive force, it is very necessary that this joint be made skilfully, or the sockets may be split. It is fair evidence of a man's good workman- ship if his iron joints are made soundly, yet do not afterwards split open, for it is no exaggeration to say that many thousands of lengths of pipe have perished from this cause. Some workmen consider that it is proper to first caulk the joint half full of yarn, the remaining half with borings ; others say three-fourths of yarn, and finish ofT with a fourth (about f inch) of borings. Occasionally only half an inch of the joint is of this latter material, and sometimes a joint may be met with having first about one-third yarn, then half an inch of borings, then a little more yarn, and finishing off with more borings. There is no doubt that three-fourths yarn and one- fourth borings makes a sufficiently sound joint under ordinary conditions, but it would be better to make one-third borings the least quantity,* although the less the quantity of this material, the less the liability of the socket being afterwards fractured. The borings once prepared cannot be kept except for a very short time, as they set hard quickly. This joint costs the least in materials, and is generally * There is no doubt that the yarn by itself makes these joints water- tight, the borings only acting as a support to the yarn, or to keep it sound and the pipe rigid. The writer once saw some joints made with old rope material caulked in, and when, in experiment, it was subjected to 30 Ibs. pressure per square inch, it was perfectly sound, and had ultimately to be burnt out before the pipes could be separated. 224 Warming Biiildings by Hot Water. considered the cheapest in the end ; but when we take into consideration the time occupied, the cracked sockets (which, of course, ruins the whole length of pipe), the inability to afterwards disjoint the pipe for alteration or repairs, &c., it is doubtful whether the rubber ring does not run it very close in ultimate expense. The proportions usually laid down for making the rust joint are, by weight, one part powdered sal- ammoniac, two parts powdered (flour) sulphur, and 80 to 100 parts borings ; thus I cwt. of borings would require about 2 J Ibs. of sulphur and fully I Ib. sal-ammoniac, and the whole must be moistened and thoroughly well mixed. These pro- portions are not fixed with any exactness ; if they vary a little no harm results. In fact, when the mixing is left to a workman, he judges (from previous experience) what is needed, and puts, say, a handful of one material to so much of another, calculating the aggregate amount by pailfuls very commonly; but if too strong, a fracture may ensue, but if a little too weak, it only takes a little longer in setting. It requires to be made from half an hour to two hours before use, according to the weather, and it usually cannot be kept longer than one day without becoming hard. The joint for general purposes, and which has the greatest use at present, is that made with white and red lead and yarn,* this being more simply made than the last, safe in results, not so very hard and rigid, and there is no after- action to endanger the sockets ; but the materials are a little more expensive that the rust joint. In making this, the white lead, which is a soft, sticky mass, is mixed with sufficient dry red lead to make a mixture of about the substance of putty when they are incorporated together. It is then desirable to mix some of this material with boiled oil to form a thick liquid paint to coat the socket and spigot with before the jointing material is inserted ; next a length of yarn is well caulked in, then a layer of the lead mixture is introduced, then another length of yarn, and so on, * It should have been mentioned that the yarn is readily procurable adapted for this purpose ; it is used in pieces about a yard long. Appliances and Fittings for Horticultural Works. 225 until the socket is filled, finishing off with the lead. This, when dry, is a very hard and durable joint, and at present is much in favour. It is the material just mentioned that is used, with a little loose yarn, to make the joint where the flanged socket is secured to the boiler. The next joint to be spoken of is that which consists merely of an indiarubber ring, the rubber being circular in section, so that when stretched over a pipe it can be made to roll up and down with moderate ease. This joint is made by stretching the rings on to the extreme spigot end of one pipe, then forcing it into the socket of the next, this being sufficient to make a water-tight and sound connection, as the rubber is of a proper thickness (about J inch) to effect this. If, however, the castings are of irregular size, as just explained, it frequently happens that the space left in the socket is insufficient for the ring to pass in, even if the edge of the socket is chipped round, and great force is used in the endeavour to insert it. This is a drawback to the use of the rubber ring joint, but fortunately not a serious one. Oftentimes the space within the socket is just sufficient to admit the spigot and ring upon it if great force is used, in which case the ring is flattened out and makes a joint of decidedly sound character, but one that would be difficult to undo after a little time. The chief objection to this rubber ring joint is its utter want of rigidity, as it affords no support whatever to the pipe, and some form of bracket or pipe-stand is needed almost at every length, unless the pipe happens to be laid on a flat surface, or in a trench. But notwithstanding this, the joint is a very convenient one ; it is durable, for the rubber adheres to the metal after a time, and it is easily and very quickly made. It is the kind of joint provided with the small independent boilers that are sold with pipes complete for erection by an amateur in his own greenhouse. This joint does away with the necessity for any device providing for expansion, as every joint in the whole apparatus is a provision in itself. The cost of material (the rubber) is more than that for a rust joint, but the greatly lessened time Q 226 Warming Buildings by Hot Water. and the utter absence of risk equalises the ultimate expense in each case. Many engineers are using the ring entirely now, as, provided they have a careful foreman, only indifferent labour is needed for joint-making. Fig- 144. When there are a large number of joints to be made, a " ring expander " is used, as Fig. 144; the rings can then be rolled on, which is better than stretching them on with the fingers an awkward method, causing the rubber to get twisted. It is almost needless to add that there are other methods of jointing pipes, by patent cements, &c., but the ordinary and successful methods are all that can be safely spoken of. As already mentioned, old rope, untwisted, will make a better joint than yarn ; and there is not the least doubt that tarred rope, old tarred scaffold cord, &c., would, under ordinary circumstances, make a good joint by itself. The particular and valuable use of a reliable expansive joint as we get with a rubber ring, or one of those about to be mentioned, is that with the fluctuations of temperature that are constantly taking place to a greater or less degree, we get a constant, though almost imperceptible, movement of the pipes, sufficient to ruin any rigid joint in a comparatively short time if the run of pipes be anything but short. We have to remember that the flow and the return pipes are never of an equal temperature, and that the movements or strains brought about by the variations in heat are irregular, and tend to make these pipes, which are connected at both extremities, injure one another, as they do not act in unison either as to time or extent. In arranging to obviate this ever-present trouble, different engineers have again different ways of proceeding. One large firm of growers * that the writer came in contact with would not * Large horticultural establishments always keep their own staff of fitters, under a foreman engineer ; and there is ample work for several men at many such places, when there may be perhaps fifty boilers in use, with miles of piping. Appliances and Fittings for Horticultural Works. 227 permit of a rust joint being made on their premises ; their joints were made, some with red and white lead, and some with rubber ring, a rubber ring at about every sixth joint as a pro- vision for irregular expansion, as explained.* Another firm preferred to use both red and white lead and rust joints, one of each alternately, and this, of course, was satisfactory ; but long loose sockets were provided, packed and arranged as stuffing boxes, to allow the pipes to have a slight movement in them as they expanded lengthwise. Great care has to be exercised in this matter if three or four pipes are carried one above the other, connected at their extremities, and are likely to be of different temperatures. An excellent form of patented expansion joint is as illustrated, Fig. 145-t This consists of two cast collars, an Fig. 145- IMPROVED OF JOINT iron ring, and two rubber bands, the drawing together of the two cast collars compressing the rubber, and effecting a very sound joint. The particular advantage of this joint is the fact that it is used with perfectly plain pipes, no sockets being needed, nor need the pipe ends be perfectly regular or cleanly cut. In addition to this, as the pipe is inde- pendent of sockets or special ends, there is no occasion to order or wait for certain lengths, as the plain pipe can be readily cut and inserted at once ; and lastly, but of great importance, this joint permits of any length being taken out * If the expansion in both pipes was equal, expansive joints would not always be needed, as the roller bearings to the supports would give freedom of movement ; but even this would not suffice always, as the extension of a long length of pipe might injure the branch services from it. t From the catalogue of Messrs. Jones and Attwood, of Stourbridge the patentees. Q 2 228 Warming Buildings by Hot Water, for repair, or in case of leakage, &c., almost instantaneously, without disturbing any other parts of the service no mean advantage, as any one will acknowledge, if, after laying down a long length of the ordinary pipe, a bad leakage is found somewhere about the middle.* This joint is not by any means a costly one, and its expense is somewhat lessened in the time saved in jointing pipes and the non-use of jointing materials ; it can be used by inexperienced persons, facilitates alterations, and the pipe is of a little less cost than the socketed variety. The price of a joint for 4-inch pipe, complete with bolts and rubbers, is is. $d. (gross) ; they are made in all sizes from ij to 6 inches, and can be had for reducing, or for receiving small wrought pipe at right angles, or set to obtuse angles, and also attached to throttle valves, &c. A well-known firm in Manchester uses this joint extensively in small size for jointing copper pipes in hot-water supply apparatus, and they are of the greatest value for this purpose, as it is Fig ' I46 ' so very difficult to get any metal or rigid joint to last with copper pipe that is subjected to heat. Another expansion joint is as Fig. I46.f With this one end only of the pipe is plain, the other end socketed in a special form, one rubber only being needed to effect the joint. The explanation devoted to the last description will show what advantages this one possesses. Another joint (Fisher's patent) is as Figs. 147 and 1484 This is used with plain pipe, no sockets or special ends being needed, and the joint is made with red and white lead with * Loose sockets have to be provided at regular distances, in long lengths of pipe, jointed in the ordinary way. These act as unions, and can be moved to disjoint the service. f From the catalogue of Messrs. Newton, Chambers, & Co., of ThornclifTe, near Sheffield, and London. \ Also from Messrs. Newton, Chambers, & Co.'s catalogue. This cannot be called an expansion joint. Appliances and Fittings for Horticultural Works. 229 hemp, a strip of canvas being used to prevent any jointing material entering the pipes. The two half-circular pieces are corrugated inside so as to ensure the joint being made soundly, by keeping the jointing material from being squeezed Fig. 147. Fig. 148. out In making the joint the material is first spread on as evenly as possible, and after the two sections are in position, the key is driven up as shown ; but in doing this, care must be exercised to see that in driving the key home the whole joint is not shifted. STOP COCKS AND VALVES. In an earlier part of the book these two articles were mentioned indiscriminately, without regard to whether the circumstance made a valve or a cock desirable. It is now time to explain the difference between the two, and to show their respective uses. The term " stop cock " is commonly used as applying to the articles under discussion, but the term is really an incorrect one, as a stop cock, in the proper sense of the word, is not usually met with in this work : they are really all stop valves, but of two kinds one the "throttle," and the other some form of screw-down arrangement which shuts off the circula- tion of water perfectly, which the throttle does not. Doubtless the only cause which makes the throttle valve so much in 230 Warming Buildings by Hot Water. demand is the fact that it is decidedly cheaper than the other kinds, and as they operate with fair success with a slow circulation such as we get in horticultural works, there is no great objection to their use. Fig. 149 illustrates a throttle valve, it being a short length of pipe with a disc of metal within it operated by a handle, its simple construction keeping the cost low, an important consideration in low-lying work, which will not always permit of using valves of a smaller "I l^^L_jn T|| size than the service pipe (as we can == nr in heating buildings, which see) ; (J I|J (Jl the cost of a moderately common quality valve of a 4-inch size is as much as 1 $s* In the ordinary throttle valve just illustrated, the disc, which is turned in a lathe, is made to fit the opening in which it works as closely as possible ; but it cannot be made water-tight, as allowances have to be made for expansion of metal, &c. No opportunity must be given for the working parts to get bound up in any way, as these valves, when once set to the requirements, may not be afterwards operated very often, although, properly speaking, they should be looked to and tried very frequently. The fact that a throttle valve does not perfectly shut off the circulation is not a very great objection in some horti- cultural works, as just explained, for the circulation, although it may be good in the ordinary sense of the word, is not very rapid, consequently it is easily checked or stopped to such an extent as to prevent any very noticeable movement past the valve, and the water passes on in other directions freely, as its impetus is not sufficient to force a great amount past an obstacle. In a vertical apparatus, even of moderate height, the circulation is of sufficient strength to effectually work through a very small opening, which permits of the use of * Occasionally valves of a smaller size than the service pipe can be used, but rarely with extensive works in glass houses, where the motive power is low. Appliances and Fittings for Horticultural Works. 231 small pipes between the boiler and the radiating media, and also small valves, without impairing results, in the usual way. The use of throttle or perfect valves is another question generally decided by the gardener in horticultural works, and their use is greatly governed by what is to be stocked in the houses, some gardeners contending that a slight variation or irregularity in temperature is sufficient to interfere with the steady progress of the plants. When such care as this is needed, the gardeners will not admit a throttle valve of any description. Fig. 150* shows a throttle valve similar to that just described, but having facilities for removing the disc or working portion for repairs, or for easing the working parts when too stiff, &c. This Fi s- r 5- is a decided improvement, as these valves of the ordinary description are far from simple to get at when attention is needed ; whereas this one, as the illustration plainly shows, renders the matter exceedingly easy. This valve, as well as the one last explained, has a stuffing box at the point where the rod of the handle passes through the substance of the pipe. Without this, of course, it would be difficult to make it water-tight, and the stuffing box is also required to make the valve work steadily ; in fact, it is usual to have them work rather stiffly, so that there may be no risk of the disc moving from any slight cause after it has been set by the gardener. Fig. 1 5 1 t illustrates what is commonly called a slide valve. This is a valve of the " perfect " kind, which does not permit of the water circulating past it when it is closed. In the illustration it will be noticed that the circulation through the barrel of the valve is checked or cut off by a slide or door, which is caused to move downwards by the screwing down of * From the catalogue of Mr. W. G. Cannon, heating engineer, London Road, London. t Also from Mr. Cannon's catalogue. (Of 232 Warming Buildings by Hot Water. the wheel handle (the valve is, of course, opened by reversing the motion). This permits of the movement in the water being regulated to the greatest nicety, and the gardeners who require Fig. 151. great exactness in results, are able to get it with a valve of this character. This valve is used to a very considerable extent. Fig. 152,* the medium screw valve, shuts off the circula- tion perfectly (even more perfectly than the last, which could not be considered thoroughly water-tight, although it effec- tually stops the circulation). This is a screw-down valve, the seating being turned and faced with rubber. It is a simple yet effective valve, but one which has a clear straight way through it is preferable. Fig. 152. Fig 153- Fig. 1 53 is another valve of the " perfect " kind, its working parts beL;g a disc hinged at the top edge with a turned face, * Also from Mr. W. 'G. Cannon's catalogue. Appliances and Fittings for Horticultural Works. 233 or faced with rubber, the opening and closing of this disc seating being effected by an ingenious thread and tooth gear, as shown. This has a straight passage through it, but it requires to be mentioned that all valves faced with rubber should have fairly constant use, or the seating will adhere to the metal it presses against if left closed, this result being accelerated by heat. The last that needs mentioning is as Fig. 154,* a novel arrangement, effecting a considerable saving in H and T Fig- 154- pieces, which very usually require two and three valves each to do what this does with one. It is in reality a double or treble-acting throttle valve, the disc being replaced with two leaves placed at right angles or in a line, as shown. With the T valve a quarter turn of the handle sends the water in either direction, but it can be placed so as to permit circulation in all directions if required. With the H valve the action is different, a quarter turn of the handle permitting the water to either pass along the flow and return past the valve (as illustrated), or, on the other hand, causing it to pass from one pipe to another without passing the valve, thus effecting precisely the result that three valves are required to do in the ordinary H piece. There are other forms of valves, more or less modifications of those spoken of, but it is needless to describe them here, as all that is required is to explain the different acting prin- ciples of what are at present in demand. Undoubtedly the ordinary throttle valve has the greatest use of all of them ; but, as explained, it is to a great extent due to its lowness in * " The Reliance Valves," from the catalogue of the Thames Bank Iron Co., Upper Ground Street, London. 234 Warming Buildings by Hot Water. price. Although it was pointed out that some gardeners required the greatest exactness in temperature, even to one degree of heat, this is only in cases where delicate things are being reared, or some important feature is being developed. To many of the common articles that come from glass-houses, a little irregularity is not minded, as they may be tolerably hardy, and only require to be guarded against the severe cold of night or winter. The throttle valve * has the advantage of a screw-down valve in indicating by the position of the handle the extent to which it is opened or closed. The screw-down arrange- ment does not do this, and if in doubt, the attendant has to try it by screwing the handle up or down to ascertain how much it is opened or closed ; but when the screw-down valve is in use, the gardener soon ascertains how many turns the handle requires for the result he wishes to obtain. It may be mentioned that valves are made to meet every requirement, for corners, upright, in box-ends, &c. None of the valves here mentioned are used for hot-water works in buildings where smaller pipes are introduced between the radiating media and the boiler. These will be referred to when that subject is treated. Although mentioned before, it will bear repeating, that it is not sufficient to put a valve in the flow pipe only there must be one in both flow and return, or the hot water will find its way up the latter pipe, and produce very annoying results. If throttle valves are used, it becomes, if possible, even more necessary. FURNACE FITTINGS. The variety of these is very limited, and at present there seems no demand for any extensive improvements. They do not seem to create any particular feeling of competition, as the same patterns can be got from nearly every maker, appearing, with little exception, as if all were made from the same design. * This valve has a very straight and full way through it. Appliances and Fittings for Horticultural Works. 235 Fig. 155* shows the oldest form at present in use a cast frame, with two cast doors with wrought hinges and fittings ; and there should be a shield plate, properly affixed to the inner side of the upper door, otherwise the heat will soon affect it. This shield plate is shown on the door in section, at Fig. 109. This plate should be cast iron, which is at all times better Fig. 155. Fig. 156. able to withstand heat than wrought, especially when no medium, as water, for abstracting the heat exists. The upper door of this style of furnace fitting is sometimes made circular in shape an improvement and sometimes the front casting is also circular at top. A more modern fitting is as Fig. 156,1 a front casting with an arrangement of rails upon which the doors are merely hung, and can be pushed freely to the right or left, or as easily lifted off. This does away with two rather weak features in the other fitting, viz., the hinges and latches, which do not operate well, that is, easily, to the attendant, who more often uses his foot than an instrument to move the doors. This sliding arrangement permits perhaps of more careful adjustment, firstly, of the lower ashpit door, which is utilised as a damper, * From the catalogue of Mr. W. G. Cannon, heating engineer, London Road, London. t Also from Mr. Cannon's catalogue. 236 Warming Buildings by Hot Water. and of the upper door, which is sometimes opened slightly when the gardener wishes to gradually cool down a little without interfering with his fire. There is another form of sliding door, which does not project so far as this one ; and it should be mentioned that there has been a set of doors recently intro- duced with the outer frame extended so as to include the customary three soot doors in it, as -pig. 157.* This is an improve- ment, as the box soot doors just inserted in the brickwork will so commonly come loose by friction with the flue-cleaning tools ; but it must be noted that the provision of soot doors in the front casting rather fixes the boiler setter with his flues. The dumb plate should be of what is called the new or im- proved pattern, being rebated at the edge where the bars come and rest upon it (see Fig. 109). The older pattern was a plain flat plate, which butted against the front edge of the bars, the two being supported by a bearing bar, which was a source of trouble, being situated where a most intense heat could act almost directly upon it. A wrought bar would quickly get misshapen. The furnace-bars (which can be spoken of but very briefly, as it is a fit subject for a small book by itself) are very usually of the plain fished or fish-belly shape. These should be thin and deep to give the best service. Their chief enemy is clinker, which adheres most tenaciously, and does its best to stop up the spaces that intervene between the bars. This objection is overcome to a very great extent by using some one of the different pattern bars that are now made with grooves or channels cut in their top surface, where the fuel rests upon, the usefulness of these grooves being in the fact that they become filled with ash, which protects the metal * Also from Mr. Cannon's catalogue. Appliances and Fittings for Horticultural Works. 237 surface, and ash being a poor conductor of heat, the life of the bar is lengthened to a considerable extent. This is a valuable improvement, but one which most of the readers will be acquainted with, no doubt, as it is far from being new, having been introduced for the furnaces of steam boilers very many years ago. Water bars, i. e. furnace-bars made of a row of tubes having water circulating through them, have been referred to on p. 198. Fi S- The form of soot door most commonly used is as Fig. 158, and is termed a box soot door, by reason of its length. This is the best form of door, the deep flange to the frame giving it the utmost possible chance of being securely fixed in the brickwork. The damper in the flue needs no description, nor does the form of soot door that requires to be placed in the chimney for sweeping purposes. 238 Warming Buildings by Hot Water CHAPTER XL QUANTITIES FOR HORTICULTURAL WORKS. Hood's rule and its application Hood's calculating table and notes thereon Rapid calculating table and notes thereon. THE quantities mentioned in this chapter are of 4-inch pipe, this being the most useful size, as a foot length can be con- sidered a superficial foot of radiating surface, and therefore the quantities in question will readily apply to radiators and other irregular shaped articles, the radiating surface of which the makers' lists give in superficial feet. If a smaller sized pipe is used, the quantity used will be one-third more for 3-inch and double the quantity for 2-inch pipe. Hood has laid down an exact rule which has needed no variation in horticultural work, but which, owing to its complexity, has had little use from the average engineer ; but it has been from this rule that practically all others of a simpler form (but approximate only) have been deduced. This rule is as follows : Rule. Multiply 125 by the difference between the tem- perature at which the room is purposed to be kept, when at its maximum, and the temperature of the external air, and divide this product by the difference between the temperature of the pipes and the proposed temperature of the room ; then the quotient thus obtained, when multiplied by the number of cubic feet of air to be warmed per minute, and this product by 222, will give the number of feet in length of pipe, four inches in diameter, which will produce the desired effect. This rule is based upon the fact that every superficial foot of glass which constitutes the glass house is capable of cooling i \ cubic feet of warmed air down to the temperature of the Quantities for Horticultural Works. 239 air on the outer side of it, per minute,* and the result given by this rule is the quantity of 4-inch pipe needed to make good this cooling influence, the calculation allowing for the lowest possible night temperature outside, say 10 F. (22 below freezing), and the water in the pipes being about 180. In allowing for so low a temperature as 10, it is supposed that all ventilating appliances will be closed at this time, which would be in the night ; ventilation only being allowed on a small scale during the day, when the thermometer would register 20 at its lowest. Of course, it is supposed that venti- lation be almost dispensed with when these phenomenally low temperatures are experienced. According to this rule, a grape house requiring to be kept at a temperature of 60, and having 1000 superficial feet of glass to it, would require 293 feet of 4-inch pipe, as follows : 125 x 50 (difference between internal and external tem- perature) = 6250 -f- 1 20 (difference between heat of pipes and internal temperature) = 52 x 1250 (cubic feet of air cooled by 1000 superficial feet of glass per minute) = 65,000 -f- 222 = 293 feet of 4-inch pipe to keep up a heat of 60 in the house when the outer temperature is 10. In arriving at the quantity of glass, the material of the frames, &c., are included ; but if they be wood, one-eighth total area can be allowed and deducted. For metal frames no de- duction is permissible, as they as readily reduce the tempe- rature as glass. Hood points out that although wind is a most active element in reducing temperature,! there is no need to take it into consideration, as when an excessive degree of cold is experienced, it is rarely, if ever, accompanied by wind ; and consequently when wind in any strength manifests itself, the * Corrugated iron, when existing, requires to be calculated, and have the same allowance made for it, as glass. t We can readily judge this by the difference in our feelings on a windy day and a still day, although the thermometer registers the same temperature on each occasion. Air is a poor conductor of heat, and when it is still it does not permit of such a ready escape of heat as when it is moving rapidly past the heated surface. 240 Warming Buildings by Hot Water. thermometer will always be moderately high compared with the degree of coldness this rule is based upon, viz. 10. The rule in question permits of variation if the position in which the house is situated should be very well sheltered, or be in any part of England, or other country, where the tem- perature does not fall so low as that mentioned ; and there might be considered other features, such as whether the fire will be attended to by a practical man or by an inexperienced person, but for general horticultural works it may be considered that the attendants are skilled. Hood also points out, and goes to some lengths to prove, that the glass, whether vertical or sloping (for both appear in nearly every glass house), needs but the same allowance in calculation. There is, as he shows, a difference in the degree at which the heat may be abstracted ; but the difference is unimportant, and as it would be governed by a number of complex conditions, it is best to treat all the glass at the same rate. But to be safe, the surface which loses heat the fastest is taken as a standard, which is usually the vertical, and this cools I J cubic feet per superficial foot per minute, as already stated. There is also a difference between lapped glass* and glass set in iron or wood frames ; but this difference only exists if the internal air be dry, and this never being the case in horticultural work, no allowance on this score is needed. As before stated, Hood's rule, though mathematically correct, is, we may say, never used : it is not adapted to the understanding of many who undertake this work, and with those who might be able to use it, something that permits of more rapid calculations being made is better liked, notwith- standing that the rapid calculating tables introduce a deal of approximate and guess work.j This, however, is usually met by allowing a little more pipe than the needful quantity, if it * The majority of new work is carried out in this way, as all the new systems of horticultural glazing allow for lapping one pane upon another, with usually a complete absence of jointing material. t Guess work is much too prevalent, and doubtless would account for many failures. How many engineers are there who could confess to taking measurements by sight only, without a rule or measuring tape ! Quantities for Horticultural Works. 241 is considered that the circumstances require it by reason of exposed situation, &c. The rapid tables are compiled by allowing a certain quan- tity of pipe per thousand cubic feet capacity, the quantity of pipe varying with the temperature required, so that if we have a glass house 30 feet x 10 feet X 10 feet, we readily find its cubical capacity is 3000 feet, and if we require a temperature of 65 when the thermometer registers 10 out- side, we must allow 55 feet of 4-inch pipe per 1000 cubic feet capacity = 165 feet of pipe for the house in question. Nothing could be quicker than this, but it is very unreliable, chiefly for the reason that in twenty houses of the same cubic capacity, probably not two would have exactly the same area of glass.* As all authorities will agree, the area of glass controls the results, and differences in results must consequently occur, although, perhaps, in the majority of cases the variation may not be important, and if the difference is sufficient to be important, then it would be noticed and allowed for.f Another feature making the capacity tables unreliable is that if we have a house, say 20 feet long, and one 40 feet long, both of the same width and height, we get in the second double the cubic capacity of the first ; yet (assuming they are both built to the same design) we do not get double the glass surface : we should get double the top and side surfaces, but the ends would remain the same, and as the ends represent a moderately fair proportion of the whole, an inaccuracy of some moment is introduced.}: In compiling the table for * The difference in this respect between lean-to houses (against a wall) and span houses is tremendous. t It is the quantity of glass wholly and solely that regulates the quantity of pipe required in horticultural work : when once the interior is heated the heat may be said to be lost from the glass only. There is practically nothing else to abstract the heat except ventilators, and the gardeners do not look to bring these appliances into use during the bitterest cold of winter midnight. At other times the heat given off will permit of a little reduction. \ In the same way a glass conservatory, which is very commonly higher than a vinery, would get more than its proper share of pipe (which , R 242 Warming Buildings by Hot Water. this method of rapid calculation (page 245) the writer has only been able to base the figures upon the average quantity of glass per 1000 cubic feet internal space. TABLE SHOWING THE QUANTITY OF 4-iNCH PIPE WHICH WILL HEAT 1000 CUBIC FEET OF AIR PER MINUTE ANY REQUIRED NUMBER OF DEGREES, THE TEMPERATURE OF THE PIPE BEING 200 FAHRENHEIT. Temperature of External Air. Temperature at which the Room is required to be kept. 45 50 55 60 65 70 75 80 85 90 Deg. Fahr. IO 126 150 i74 200 229 259 292 328 367 409 12 119 142 166 I 9 2 220 251 283 318 357 399 14 112 135 159 184 212 242 274 309 347 388 16 105 127 J5 1 176 2O4 233 265 3 00 337 378 18 9 8 120 143 168 195 225 256 290 328 368 20 91 112 i35 1 60 I8 7 216 247 28l 3i8 358 22 83 105 128 152 179 207 238 271 308 347 24 7 6 97 120 144 170 199 229 262 298 337 26 6 9 90 112 136 162 190 220 253 288 327 28 61 82 IO4 128 154 181 211 243 279 317 30 54 75 97 120 H5 173 202 234 269 307 32 47 67 89 112 137 164 193 225 259 296 34 40 60 81 104 129 155 184 215 249 286 36 32 52 73 9 6 1 2O 147 175 206 239 276 38 25 45 66 88 112 138 166 196 230 266 40 18 37 58 80 104 129 157 I8 7 220 255 42 10 30 50 72 95 121 148 178 210 245 44 3 22 42 64 87 112 132 168 2OO 235 46 .. 15 34 56 79 I0 3 130 159 190 225 48 .. 7 27 48 70 95 121 150 181 214 50 .. .. 19 40 62 86 112 140 171 204 52 ii 32 54 77 103 131 161 194 Hood, in his painstaking way, went to enormous trouble to compile a table that would dispense very greatly with however, is no fault), as, supposing it to be double the height of a green- house, it would have practically the cubic area and side glass surfaces of two green-houses, yet it would only have one top. Quantities for Horticultural Works. 243 the complexity of the calculations needed by the rule he laid down, this table being based upon the rule itself, but, as it will be seen, making the total to be arrived at much more easily discovered. This table, however, has one serious objection viz., that it is based upon the pipe being at a temperature of 200. Although this is quite possible, it is not usually experienced in effect, and 180 should be con- sidered the maximum* with skilled attention ; therefore, if it is desired to make use of this table, one-fifth should be added to the quantities of pipe given to allow for the pipe temperature being 20 lower than that which Hood has calculated upon. It was mentioned that the glass was the sole cause of loss of heat in horticultural work after the interior air and fixtures were once heated. This is so ; but in the usual way it takes three or four hours to get the heat up to the required degree when first lighting, as, firstly, there is the volume of air to be warmed, then all the interior fittings are absorbing heat on a considerable scale ; and what takes even longer to cope with is the amount of moisture that would exist in such an instance and neutralize the general effect of the heat in a great measure. A perfectly dry place would be heated up much quicker. Hood approximated the time that a glass house, with a sufficiency of pipe and a boiler of corresponding power, takes to become heated up as follows : With 4-inch pipe .......... about 4^ hours. 3 .......... 3i These times cannot be relied upon with any accuracy, although they are useful to base an idea upon ; but in heating * The word " maximum " is correctly used, for unless the fire receives proper and sufficient attention from a person accustomed to the work, 1 80 will be the exception and not the rule. t The results with 2-inch pipe are so much quicker, as they contain much less water for a given amount of radiating surface than the larger sizes. R 2 244 Warming Buildings by Hot Water. up, the time must vary by the condition of the interior fittings, whether very damp, &c. ; the cubic contents, which vary very greatly ; and the natural temperature of the atmosphere, which varies still more. When the fire is started, the warmth from the pipes goes to heat the air, and the air to heat what it first comes in contact with, and for a little time the glass has no cooling influence ; but as soon as the whole internal air has attained a higher temperature than that outside, then the cooling process is commenced, and it increases as the heat inside is increased, until (supposing the quantity of pipe to be exactly correct, &c.) they balance one another. In the following rule for calculating quantities of pipe per 1000 feet cubic contents of glass houses, it must be repeated again that the figures are approximate only, conditions and position varying. In this table the pipe is supposed to be kept at 1 80, and the extreme coldness of the outer air to be 10.* In the inspection of a greenhouse the following things require consideration before fixing the quantity of pipe. 1. Its position, whether exposed, or sheltered by sur- rounding houses, trees, or walls. If unusually exposed, additional pipe should be used. (Span houses suffer most in this respect.f) 2. Position with a lean-to house, as to whether it faces south, south-west (the two best), or a more trying quarter. If not south or south-west, some additional pipe should be allowed. 3. If not a large works, it is important to know how the fire will be attended to. If by a coachman or boy, then a * This can only be for a limited number of nights in winter. Some fruits require a varying heat as tomatoes, which, when being ripened off, are commonly given a higher than normal temperature ; but unusual heats are never needed in mid-winter, and at other times nature will assist, so that a maximum temperature of say 70 in winter can readily be in- creased to 80 in spring. t Span houses are commonly lower (taking a mean height) than lean- to houses, and consequently have more cooling surface for the cubical capacity than they would have if they were as high as the other houses. A cube-shaped house would give us the least glass surface in proportion to its internal capacity ; any deviation from this increases the cooling surface. Quantities for Horticultural Works. 245 good allowance in extra pipe should be allowed (and a little larger boiler would be advisable). The following table shows the length of 4-inch pipe needed to keep up a given temperature to every 1000 cubic feet capacity in a glass house for horticultural purposes, the pipe being at 1 80, and the outer air at 10 or higher (no ventilation when outer air below freezing point). Temperature required. Quantity of pipe to each 1000 cubic feet. Some of the purposes for which the houses may be required. Deg. Fahr. 9 feet. 80 85 75 Pines and forcing purposes. 80 70 75 65 ] Tropical flowers and some ferns. 70 60 I Pits for melons, &c. 65 55 60 So Grapes, strawberries. 55 45 5o 45 40 37 > Fruit trees, conservatories. 40 35 Trees, cuttings, stock, &c. The above quantities are for lean-to houses, with one side of brickwork ; if span houses (position not much exposed) add one-fifth to the lengths or pipe given. If pipes carried in trenches or channels, covered with a grating, they must be calculated as being one-fourth less effective than those that are exposed.* Notwithstanding every care being used in compiling the above Table, which will in practice be found safe and give the results quoted, it is yet better to allow more pipe still ; economy is not of first importancef; even 15 per cent, more pipe could advantageously be used, requiring less attention at * If the channels are not of full size the pipe will be still less effective. t No such allowance is necessary if the works are for a professional grower or an amateur on a large scale, as there would be highly-skilled attendants employed. 246 Warming Buildings by Hot Water. the furnace and further obviating risk of failure, as it must be remembered that for the heat to go down on one occasion only is sufficient to cause disastrous results if the weather be severe. The remarks in the right hand column of this table are, to a great extent, useless, as it must not be supposed the hot water engineer is the person to fix the temperature for certain purposes. It is understood he has to receive instructions in this respect from the gardener. Notwithstanding the use of this rule it can be recom- mended as a wise precaution that the area of glass be also measured as accurately as possible, and the amount of pipe required calculated by Hood's table, and so let one method check the other. This will, it is to be hoped, bring the result as close to accuracy as it is possible, as should the two calculations differ to a serious extent, it will at once indicate the existence of some unusual circumstance in con- struction. This may be considered a deal of trouble, but it is trouble worth taking. Nearly every one has heard of failures occurring in hot water works of this kind. They are not infrequent, but in nearly all such failures the apparatus will be found correctly erected but insufficiently effective, the calculations having been wrong somewhere, either in boiler or pipes, or both. It will not be forgotten to allow upon Hood's table, as explained just before it. CHAPTER XII. FUEL, STOKING, AND ATTENTION TO HORTICULTURAL WORKS. Fuel Steam coal, coke, &c., and its use Sulphur Stoking and regula- tion of the fire Damping down Attention to air vents Flue cleaning Frost, and precautions necessary Non-freezing solution Clean sur- faces to ensure full radiation of heat. It is desirable, perhaps, before closing the description of horticultural hot-water works, to mention a few things in connection with the use of the apparatus, and as to stoking, &c., also as to some different features in these undertakings that require attention after the work is complete. The fuel used in these boilers * is almost as varied as fuels can be, as in many places, badly situated for con- veniently obtaining what may be best suited, resource has to be had to wood and even peat, when the coal or coke has run short ; in fact, anything that evolves heat will do temporarily if the apparatus is not on a large scale ; but with such fuel as wood, a deal more attention would be needed. Wood in blocks, made by cutting about a 6-inch tree branch into 6-inch lengths will be found fairly successful when nothing better can be obtained at the moment required. The customary fuel for very large boilers, brick set, is hard steam coal. This coal has -a moderate percentage of bituminous properties, sufficient to cause a useful and effective amount of flame, without making such a heavy deposit of soot, as the softer kinds of coal do, which commence to flare before they are at a really intense heat, the soot not only preventing the water having the benefit of the heat evolved * For both horticultural and building works. 248 Warming Buildings by Hot Water. by its low conductivity,* but also represents so much lost fuel fuel converted into a form in which it cannot be usefully employed for giving heat. The steam coal, although having a flame and causing a sort of deposit, does not have this latter disadvantage in nearly such an aggravated form as the soft coal ; as in the first place its bituminous properties are limited ; and, secondly, in burning it reaches a much higher temperature and state of incandescence than the other, which greatly aids in reducing the formation of soot. This coal is not expensive, from i6s. to 19^. per ton delivered in London in one or two ton lots (small quantities), and it is very economical in use, it being so lasting in com- bustion ; but it is not so inexpensive as what is known as slack, which is coal-pickers refuse, not necessarily small, but very mixed usually, and costing practically nothing but cost of transit from the pit Slack is not so good in general results as hard steam, and not so clean, but some people minimise its drawbacks to some extent, by mixing coke with it. A mixture of coal and coke is a very effective fuel. For medium-sized brick set and for independent boilers of practically every kind, coke without any coal admixed is best, and is used more largely than any other fuel. Coke, when fairly alight, evolves a most intense heat, as it so readily becomes incandescent, and there are then no obstacles (smoke and soot being absent) whatever to the boiler experi- encing its full effectiveness. No doubt the absence of soot is a great factor in the good results obtained, as the surfaces, particularly in the flues, are kept so clean, and it will be found that the heated air and hot gases from a coke fire do excellent work outside a boiler ; not so much as flame at first starting perhaps, but flame, by the soot it carries, so soon neutralises its capabilities to some extent. Coke, however, has rather a deleterious effect upon iron work by reason of the active action of the sulphur contained * Were it possible, soot would be fairly effective to put outside inde- pendent boilers to prevent loss of heat, as it ranks moderately high as a low conductor. Fuel and Stoking. 249 in it. This sulphur is, of course, present in coal, even to a greater extent than with coke, as in the conversion of coal to coke a deal of sulphur is carried off with the gas ; but it will be found that in the consumption of coal the sulphur is not nearly so noticeable, as different causes tend to render it more inactive as against the iron work. The activity of the sulphur with coke is, however, not very objectionable upon surfaces which are kept at a low temperature by water being in contact with them on the other side, and the present form of welded wrought boiler, which has all smooth surfaces, suffers very little indeed ; but this cannot be said with the furnace fittings or with any projecting parts from a boiler itself, and with rivetted boilers it is generally considered that the ultimate failure of the rivet heads on the heating surfaces is due to the insidious action of the sulphurous acid, when coke is used. With coal fuel, the rivet heads do not suffer nearly so much, although the coal may have exactly the same percentage in it as the coke. Notwithstanding the sulphur, coke is the best fuel for nearly all boilers, and it is of particular advantage with those boilers which have a complexity of tubes or irregular heating surfaces, and which would be of some trouble to keep clean of soot. With the small forms of independent boiler, all the cinders from the house fires can be successfully used. A deal of skill can be shown in stoking a furnace, even with those of a small size, and with those of large capacity it is, of course, well known that stoking is a calling in itself, needing some intelligence. With boilers for ordinary hot- water works, however, it is only necessary to point out a few rules for general observance. The most effective fire, that is, the one to give the greatest results with the least expenditure of fuel, is that which is always kept bright, and this can only be done by frequent and regular attention. It is necessary with this object in view to keep a rather thin layer of fuel upon the furnace bars (except when banking up for the night) ; as apart from the brightness of the whole of the fuel, the combustion is rendered more perfect with less formation of carbonic oxide (see 250 Warming Buildings by Hot Water. Combustion). With coal fuel it is the custom to make use of the dead plate immediately inside the furnace door for receiving a charge of fuel, so that it may be dried and partially coked, the more volatile products being thrown off as it lies at this point, and these products having to pass across the incandescent fuel, undergo combustion, and do effective work instead of going to form soot, as they would have done if the coal was put directly upon the fire. It is very improper to force fires, that is, get them up to a fierce state in a short time, it should be quite unnecessary, and is commonly evidence of bad stoking. This frequently happens with a new apparatus in a building, where the attendant is an odd man, not having the skill a gardener would, and being unacquainted with the work, the consequence being that the water becomes overheated ; and unless the boiler has an expansion pipe directly from it, and this of good size, there will be an overflow at the supply cistern by the generation of steam at the boiler. When this occurs it is most quickly stopped by opening the front furnace door, which will permit of a free passage of cold air over the fire to the flue, and the boiler will be cooled, and the effect of the fire be lessened. If the boiler is fully large for the work the risk of over- heating is increased, but this risk can only be for the first few days, as the attendant should quickly become acquainted with the use of the dampers, and then the advantages of the larger boiler become apparent, for with the greater effective- ness of the large fire, the dampers can be nearly closed, attention in feeding the fire reduced to a minimum, and in the end it will be found that a saving of fuel is effected by reason of the lessened draught and speed of combustion, although the boiler takes a larger charge of fuel in the first place. It is the common practice for gardeners to use the front furnace door to lessen the heat, instead of altering the damper in the chimney. In charging the boiler with fuel for the night, it is usual and best to place some ash on top to " damp " the fire dowc as it is termed, the real effect of the ash being to choke all Attention to Apparatus. 251 the little air passages between the fuel, and smother it to an extent. A fire skilfully " damped " down will keep alight for an incredible time, but it is only for the night that this practice is adopted, as it causes the fire to get into a dirty state, and would be less effective after some few hours, un- less it was raked and cleaned as requires to be done each morning. This latter attention does not necessitate with- drawing the active fuel from the furnace. In an apparatus having air-cocks, it is very necessary that these be opened to discharge the air frequently. It will be found that air accu- mulates at the high points in the apparatus (of any kind) very rapidly, and it is a good plan to open the air-cocks as often as twice a week, as in many instances the accumulation of air may be at a point where a small quantity will interfere with or wholly check the circulation.* The time for cleaning the flues varies from several causes, but experience quickly fixes the time in which it should be done, as the attendant can so readily judge by the quantity of soot or dirt that he removes. Attendants' ideas, however, vary, as those who have the time and the desire clean the flues very frequently daily, as it renders the boiler more effective, and is consequently a good practice. With coke fires, attention in cleaning is still needed, but not with such frequency as when soot is formed. The deposit from coke is a fine dust, that will be found in the greatest quantity on horizontal surfaces, or anywhere that it can rest. Frost has particularly to be guarded against in all hot water works, but more particularly to those devoted to horti- * A peculiar instance of this came to the writer's notice quite recently ; a school dining hall insufficiently heated by the fires was fitted with some radiators in connection with a hot water apparatus. They were a success for a week or two and then failed, and the master instead of mentioning the matter took it for granted that the work was a failure, and actually let the matter rest for nearly two years, when it was discovered that the air taps had never been opened, and the radiators had been full of air all this time. No water could get into them to be of use, as they were of the kind that have upright pipes, which necessitates their being quite full to permit the water to circulate. 252 Warming Buildings by Hot Water. culture. There ought not, however, to be any fear that frost will be permitted to act upon the contents of a glass house unless the attendant be exceedingly careless, but there are other effects of frost that need be guarded against. If a new apparatus be cpmpleted during severe weather it should not be charged and left full of water unless it is convenient to light the fire at once, and to keep it alight night and day, and in the same way no existing apparatus should have the fire drawn, and be allowed to cool down, unless it is intended to at once withdraw all the water it contains, as should the water in the pipes, radiators, or any other parts be allowed to freeze considerable damage will be caused. It is unnecessary to deal with the question of the ex- pansion that takes place when water freezes. This, in a general way, is within everyone's knowledge, and it is suffi- cient to point out that no cast or wrought iron pipes, used in a hot water apparatus, are strong enough to withstand its effect, and a fracture must occur, unless by some favourable circumstances there was a space into which the water could expand itself without resistance. Sometimes an expansion joint of one of the many kinds will prevent damage, as the force exerted will disjoint the pipe, but this cannot be relied upon by any means, for the expansion is very sudden. The smaller the pipe the quicker the water freezes, and the only really good remedy is to keep the fire alight or to empty the apparatus. There are now to be obtained materials that will success- fully prevent water freezing at the lowest English temperature. Mr. Stainton* patented a solution containing as its chief in- gredient chloride of calcium, and this permits of water retain- ing its fluidity at an intense degree of cold. Common salt is * Of the firm of W. Stainton and Sons, a firm of high repute in general hydraulic engineering. His invention was for the object of preventing the water being frozen in the pipes of high-pressure apparatus, which cannot be so readily emptied and refilled, certainly not by an inexperienced person, and for this purpose the invention is a decidedly valuable one. Attention to Apparatus. 253 effective in a moderate way, as water will take sufficient of this material in solution (about 30 per cent.) to prevent its freezing at our lowest known temperature, but for various reasons it has never gained favour, and it is not the writer's intention to recommend it. It requires to be mentioned that if a boiler and apparatus be emptied, great care should be exercised to see that they are filled before the fire is lighted, as not only would injury be done to the boiler, but the inflow of water on to hot boiler plates would probably cause an explosion of a very serious character. It is also necessary to protect air pipes from frost. They should always be arranged so that the part of the pipe that contains water is within the house, only the empty portion passing outside. It is not always necessary to carry the air pipe outside at all, but it is usually done in case of the boiler overheating, and steam or water being ejected. All radiating surfaces, pipes, &c., should be kept quite clean, otherwise the heat will not pass from them freely, depending upon the thickness of dust. Pipes in trenches and beneath gratings are apt to be neglected, and the same remark applies to coils of pipes in cases. Every portion of pipe that is not used for radiating should be covered with a material to prevent loss of heat (see p. 120), as otherwise the heat it diffuses will be totally lost, and represent so much wasted fuel, even supposing the boiler is powerful enough to allow of the waste. 254 Warming Buildings by Hot Water. CHAPTER XIII. UPON WARMING BUILDINGS (LOW PRESSURE). Distinction between horticultural and building works Pressure and how exerted Calculations for pressure Shapes for boilers when pressure excessive Pressure does not aid circulation Comparison in size of pipes Air cocks and vents Expansion pipe Water supply. THE preceding papers have dealt almost exclusively with horticultural works, but it will be found that there are many minor points that apply to all hot water works alike, and instead of repeating any of the information given it is pro- posed, as the subjects are reached that have already been mentioned, to make reference to the pages where these questions are dealt with. In treating the heating of buildings, the various pheno- mena relating to circulation, radiation, &c., are actuated by precisely the same natural laws as in horticultural works, but the circumstances and conditions are so totally different as to make it almost a distinct calling, so much so that a man accustomed to glass house work wholly, would be at a loss to erect hot water plant for buildings unless he had considerable tuition, in the same way that he would be incapable of erecting a circulating apparatus for domestic hot water supply (see P- 329> In hot water works for buildings, where the apparatus extends upwards, perhaps, several floors, there is introduced a feature which is not present in horticultural works that rarely extend more than a few feet above the boiler, this feature being the great strain that is exerted upon the lower parts of the apparatus by the pressure or weight of water. For the information of those unacquainted with hydraulics Distinctive Features in Building Works. 255 it must be explained that this has no reference whatever to the bulk of water, as this makes no difference, whether the quantity be large or small. The pressure of water in pipes is exactly proportionate to its weight viz., that the contents of a pipe two feet four inches high,* and having an internal area of one square inch (the nearest sized pipe we have to this is ij inch diameter) will, when full, contain I Ib. of water, ana a boiler having a pipe this length connected with it vertically, and fitted with water, would be said to have a pressure of I Ib. to the square inch within it, this pressure being as stated merely the weight of I Ib. of water pressing within it. The common impression would be that this pressure of I Ib. would be distributed over the whole of the boiler (which is correct), but diminished by being spread over a large surface. This, however, is not the case, as the pressure of 1 Ib. will be exerted upon every square inch inside the boiler, top, bottom, and sides, so that the aggregate pressure brought to bear upon a moderate sized boiler by the contents of this short length of pipe may be two tons,f and this needs con- sideration in various ways in the works now alluded to, as we do not have merely the effect of this short length of pipe to deal with, but with an effect twenty times as great when the apparatus extends up three or four floors. Another, what may almost be termed a peculiarity, is that the effect is precisely the same with any sized pipe that may be used, whether it be J inch or 4 inch, but it is only vertical pipe that counts that is, the vertical height between the supply or feed cistern and the boiler will give the pressure exerted in the boiler by calculating I Ib. for every 2 feet 4 inches of this measurement in question. From the boiler upwards the pressure diminishes in exactly equal ratio, every 2 feet 4 inches in height the pressure per square inch in th c * This may be termed practical measurement ; it is not strictly correct, as the actual figures are 4328 of a pound to the foot. t Any treatise upon hydraulics or hydrostatics explains this. Without this peculiar phenomena the hydraulic lift, hydraulic press, &c., would be of no use. 256 Warming Buildings by Hot Water. pipe, or in any appliance connected with the pipe, being reduced I Ib. In case it may not be clear to all the readers why the pressure is precisely the same with any sized pipe, it may be explained that the standard of pressure is a supposed mass of water 2 feet 4 inches high and I inch square, this mass or body weighing exactly I Ib. Now, if we could stand this upright, we should have one end of it standing upon a space exactly I inch square, and this small space would be pressed upon by a weight of I Ib. If we took another body of water exactly the same size and placed it close up against the other they would together be a quantity representing the contents of a pipe with an internal area of 2 square inches, and we get double the weight or pressure, but the pressure is upon 2 square inches of space at the bottom ; we have not increased the pressure per square inch. We have doubled the pressure certainly, but taken double the space to exert it upon, or, in other words, a pipe of a size equal to 2 square inches exerts double the pressure of a pipe of I square inch, but as it exerts it upon double the area there is no increase of pressure per square inch. On the other hand, a pipe of an area of half a square inch would only contain sufficient water to exert a pressure of half a pound for every 2 feet 4 inches of its height, but this half pound would be exerted upon every half square inch in the boiler, and so with the reduced pipe there would be no reduction of pressure per square inch in the boiler. The same reasoning permits us to have a various number of pipes entering the boiler without in any way varying the pressure, as the pressure of water, both in the pipes and boiler, exerts itself exactly in all directions. No one pipe would cause more pressure than another, and no part of the boiler would escape more than another. It will also be understood that it matters not what quantity of water is contained within the feed-system, the fact of the cistern having a large capacity makes no difference if the height of the cistern remains the same. Of course, if we had a tall cistern full to the top, there Distinctive Features in Building Works. 257 would be a greater pressure exerted than with a shallow cistern, supposing both were upon the same floor. The height of the water-line in the cistern adds to the pressure in the boiler exactly as if it were a pipe, viz., one pound to the square inch for every 2 feet 4 inch vertically. This strain upon a boiler has no injurious effect to speak of, but it firstly necessitates the use of a proper-shaped boiler when a high pressure has to be borne (say, for three or more floors of a warehouse), as the ordinary saddle boiler, even of |-inch plate, may become bulged on the inner side, even when first charged and cold ; and it does not permit of the boiler being used so long as with a low pressure, for so soon as the boiler gets a little weak from wear and tear, the heavy pressure will bring about its destruction. With low pressure works the boiler might wear until it was quite thin, and still do good service. If the boiler were small there would be no particular fear of bulging, but with a plain saddle boiler, four or five feet long, it would be most probable, and consequently, when a strong pressure has to be borne, a strong form of boiler is used, and preference is commonly given to a cylindrical shape, as a cylinder is capable of bearing enormous strains if equally distributed inside, as it would be with water (or steam). To those, however, who wish to avoid responsibility in this respect, it may be suggested that the vertical pressure be mentioned to the boilermaker, when purchasing, and he will then supply what he can safely be responsible for. In the bursting of a circulating apparatus containing water only (an exceedingly rare occurrence) there is no danger whatever to be feared, unless it occurred through the expan- sion pipe, and all such outlets being tightly closed (by frost), as in this case probably steam might be generated, which would be an element of great danger. If a burst occurred through the mere pressure or weight of water, there would instantly be a violent outrush of the liquid, but this would only be harmful to those who might be near enough to be scalded, supposing the water was at a high temperature, 258 Warming Buildings by Hot Water. further than this nothing need be feared. It is such a different matter with steam, for the elasticity of this fluid has a rending effect of a truly terrific nature when the steam is at high pressure, and a burst is a highly dangerous occurrence. Water may be considered (for the purposes of this paper) incompressible, and consequently inelastic, as it can only be compressed one-sixteenth of its volume under a pressure of 20,000 Ibs. to the square inch. There is an erroneous idea, somewhat prevalent amongst workmen, that the pressure, in an apparatus that extends some distance vertically, aids the circulation. Perhaps this error is fallen into easily from the fact that, as a rule, the greater the pressure, the more rapid the circulation, for an increase of pressure indicates increase in height, and, as a general result, we may always look for a quicker circulation the higher we go (see p. 63). But it must be clearly under- stood this is in no way accounted for by the pressure, which is exerted equally in all parts, and if it increased the flow of water down the " return " pipe, it would just as greatly retard the flow of water up the "flow" pipe, for it presses with practically equal force down each. The erroneous idea, how- ever, is fairly common, and workmen will be found sometimes putting the supply cistern much higher than necessary with the view to increase the circulation ; a very unnecessary thing in these works, as a rule. The circulation, that is, the strength of the motive power and speed at which the water circulates, is, in these works, if properly constructed, everything that could be desired, as reference to p. 63 will make clear, and is sufficient to over- come many obstacles that would render a horticultural appa- ratus inefficient by reason of the exceedingly low motive force in these latter works. There is invariably a high speed of circulation in all verti- cal apparatus, but the motive power does not increase in exact ratio with the increased height of the pipes, and we might reasonably expect that there could be a height which would not permit of the circulation taking place at all, but this limit Main Pipes in Building Works. 259 is never reached in building works of an ordinary character, even with the highest blocks of warehouses that exist at present,* neither is it likely to be reached just yet. There is another result introduced in vertical works that sometimes needs consideration, which is, that with a rapid circulation in the main pipes, there is a likelihood of the water passing by the branch services without freely circu- lating through them as it should do ; but this does not need such very particular attention in the ordinary way, and any methods for overcoming this difficulty, can be better explained when showing some example works (pp. 280 to 300). The main pipes of these erections are, as a rule, rather small compared to those in greenhouse work, for with the high velocity of the circulation, frictional resistance plays a less important part. No rule can well be laid down to determine the size of the mains, as their capacity may be ruled by various incidental features ; but commonly their increase or decrease in size would be governed by the greater or less quantity of water contained in the radiating media,f the greater or less quantity of radiating surface (which would vary the quantity of hot water to be brought to replace that which has lost its heat), and lastly, the greater or less vertical height, which governs the motive power. The higher the motive power the less size the main pipes need be. There is no gain whatever in having the main pipes larger than is really necessary, as, assuming them to be exposed, they would lose more heat if large than if small, and they would increase the bulk of water to be heated, this increase * If we ever have buildings of enormous height, there is no doubt that any heating by hot water would be done by two or more boilers placed at different heights, each boiler taking so many floors. If it were attempted to heat all floors from one boiler in the basement, it would need one of enormously strong make ; the joints of the radiating media would also have to be very strong (at the lower floors), and there would have to be a range of boilers and many separate main services, otherwise we should be poorly supplied with heat at some points. t Some of the modern radiators have a very large radiating surface for the quantity of water they hold. S 2 260 Warming Buildings by Hot Water. being of no service in the usual way. Of course, if any part of the main pipes are used for radiating purposes, this argu- ment will not hold good ; but this again is not a usual practice. Suggested sizes for main pipes will be spoken of when treating of example apparatus. The question of covering pipes that are used merely for conveyance of water, and not for radiation, was spoken of in horticultural works, p. 120, and will be found again referred to under hot water for domestic purposes, p. 329 ; these latter works are more nearly related to those under discussion. It can, however, be repeated that every part of the services not used for radiating purposes should be covered, and loss of heat prevented. Air vents are of course equally necessary in these as in other works, but it is not the usual thing for air pipes to be admissible unless the works all occupy a low level. Air pipes are decidedly the best whenever they can be used, but if an apparatus extended up several floors of a building, the vent pipes, from the lower part, would have to be of a most expensive and inconvenient length, quite unreasonable in fact, and introducing one or two objections. Air pipes are also considered unsightly, for even warehouse work, especially if made up coils or radiators are used, which would necessarily have the air pipe connections rather prominently in view. As a rule, some form of air cock is used, and these, as ex- plained, require regular attention to allow the air to be expelled, for it collects at all the high points very rapidly. When an apparatus is wholly devoid of air pipes, it is usual to provide an expansion or steam pipe at the top of the circulation, in event of the apparatus overheating ; but not all make this provision, as no danger need be feared, while the cold supply pipe is clear. Any unusual expansive force would relieve itself through this, but causing most probably a sudden overflow of water. It is best to have an expansion pipe it is practically always possible, and it should be of fair size. It might as well be of the same size as the mains, considering it only wants carrying up a short distance to be Water Supply to Building Works. 261 above the supply cistern. It will be seen presently that the circulation can be made to pass through a tank at top, this tank being filled but a little way up, and having either a loose cover or a good-sized expansion pipe from it ; this plan is very satisfactory. The tank only needs to be of small size. The water supply to these erections is provided for by a cistern of proper proportions, see p. 52, but it is not so usual for these to be rilled by hand as with horticultural works, and consequently a ball valve has to be introduced, and unsatisfactory as these things are in general use, they are still more unsatisfactory for this purpose, as they have so little work to do, and they therefore need frequently looking at, even with the best of them, as the ball arm gets stuck and hung up, and does not admit the water to replace that evaporated. This, however, is not a serious matter, as with a moderately high apparatus there need be no fear of the pipes and boiler getting entirely exhausted of water for at least a very considerable time, and there would be various symptoms to indicate the fault. There, however, remains the fact that there is no ball valve that can be thoroughly relied upon for this work, and they must be inspected periodically. Where the pipes (main or branch) pass along conspicuous places, they may be decorated in colours to match their surroundings, either oil or water colours (but it is better to cover them as explained). In the same way the radiating surfaces, whether pipes, coils, or radiators, can be painted any colour, and many of them permit of very skilled treatment in decoration, but bronzing or gilding or giving any bright metallic surface is objectionable in results. See Radiation, p. 9. The boilers have been fully treated (Chap. VIII ). It only needs to be mentioned that in ordering these the sized pipe to be used should be mentioned, and also state that it is wrought pipe, otherwise the plain sockets for large cast pipe may be fitted and sent, causing a deal of trouble. 262 Warming Buildings by Hot Water. CHAPTER XIV. PIPES AND APPLIANCES FOR BUILDING WORKS. Pipes and fittings Qualities Price list Joints Gilled radiating pipe Coils and radiators, and their distinctive features Box coil Coil with expansive joint Coil cases and objections thereto Connections Cannon's radiators The " Universal " radiators Rosser and Russel's radiators Sanderson radiator Heap's radiator Saturation of the air Ventilating radiators Stop valves. THE pipes and fittings, used for main and branch services in these works, are almost invariably of wrought iron, the same in fact as are used in hot water works for domestic supply, and also in steam heating, the only difference being in size, and this difference is very small. This pipe has screwed joints of an ordinary character, a joint eminently suited for the pressure that has occasionally to be withstood. There are two qualities of this tube, the cheapest being that used for gas services, and is of a natural black colour. The best, which is used for steam, is of a much stronger quality, and is sent out from the works painted a dull red. Both these qualities can be had galvanised if desired. They are then, of course, both of the same colour, and can only be distinguished by the thickness of metal. The steam quality should always be used (unless the works be of a very tem- porary nature), as the difference in cost is not so very great, and although the black tube is used with the greatest fre- quency it is a bad practice, and often leads to complaints. Another disadvantage with black tube is that the fitter, in making his soundest joints, has to exert considerable strength, and unless the tube or fittings be strong he may, with his tools, crush the material or else distort its shape, and in either case render it useless. Wr ought-iron Pipes and Fittings. 263 *jvoOOvOOOvOOOOvOvoO\ O\vo O vO O t^ ON t^ o vo vo o vo vo ^-vo o co co Ti- <* co 1000 co O\ covO O O vO VO O O m t>. o o\oo OVO O O O m\o CO vO VO *Q O\ co O O O co ONVO O co O O co co O covo O 4 M N cocO'^-'^-cococomi-i i * HH i-i M NOO Ovo Ovo O H M N N CO <* O O vO COVO COO vO 00 00 O O t*> ONO OOO COX) COVO MNNNNNNNCOOOOOOONH OOMMNN ^j M woo COO O\Q\O\>-< OvOvOOOOOvO ONVO vO VO O\ N vO *i CO OJQ-WWNWMMIHHCOOOOOOO^OO 00-HHN CO CON rh CO ^ rJ-vO VO ^t-t^Tj-vO vO 00 O <; o o N O O O O O O wvo O O -" M IH ^voooOOC<-iOOOOcocomm covO NVO ^mt^O NVO O\ *;OOOOHOHIMOOOOOOM^OOOOMI-IM M OOOOOOOOOwOOOOOO'-' f*5O O O O M M. M ^ : : M w- 1 ^ a ^ M o S ? J? p-*" ^ o .! .S .3 .S COTj- VO ; r^HiN'^ HNHN'^ -N ci co ^- vnvo txod o\O* "-I ri coffi CO 264 Warming Buildings by Hot Water. The universal list of wrought tube and fittings on the pre- ceding page applies to all qualities, black, red, or galvanised, the difference in price being effected by allowing more or less discount from it. The pipes for radiating purposes can be of the same make and quality as those for horticultural works (see p. 217) if desired, but it is needless to say that they are not suited for positions where appearances have to be studied, but for warehouse work, drying rooms, covered trenches in churches, &c., there could be no objection whatever, but care is needed in making the joints. The rubber ring joint, which is so useful in horticultural works, cannot be used where there is a pressure of even a few pounds, and neither is the red and white lead used to a great extent, as it will not bear pressure when it is soft, and consequently prevents the apparatus being charged until the joint is set hard, supposing the apparatus is of fair height. The rust joint is almost ex- clusively used in this work purposely to effect a very strong joint capable of resisting a severe strain. (See p. 222). There has been some pipes introduced having gills or plates on their exterior surface, one as Fig. i, page 8, and another form as Fig. 159.* The Fi - I59> latter is best in results, as it does not so readily collect dust to minimise its radiating power, supposing the pipe to be fixed horizontally. The ob- ject of these gills is to extend the radiating surface as described with the gill stove (p. 316). We do not get quite the useful effect with a hot water pipe as we do with a stove, but a fair degree of usefulness is experienced in the way described, and the pipe is always at a safe temperature if anyone's hands come in contact. This description of pipe would be no particular gain for trench work. It can be made up into coils as fig. 160.* This principle is also adapted in * From the catalogue of the General Iron Foundry Company, Upper Thames Street, London. Coils and Radiators. 265 a very ingenious way to circular upright (pedestal) coils, one pattern consisting of a series of ring or annular pipes with gills, and another being sections of a fair-sized pipe, each Fig. 1 60. section having gills or feathers round its circumference. Every description of gilled pipe must be fixed so that the gill plates do not lie flat to collect dust, as radiating surfaces must be clean to be effective. The distinction between a coil and a radiator is at present in a very undefined state, as a stack of plain pipes fixed horizontally is always called a coil, even though it may not be of a coiled form, but have box ends as Fig. 161*, whereas if the pipes were of a slightly ornamental character and fixed vertically, as some of those illustrated further on, it is termed a radiator. Both act precisely the same, are connected the same way, but with the radiators the makers are now aiming at giving the greatest amount of radiating surface to the least amount of water, so as to get quicker results, and the vertical arrangement of pipes has the particular advantage of keeping free from dust. The common form of box end coil, Fig. i6i,f is composed * From the catalogue of the General Iron Foundry Company, Upper Thames Street, London, t Ibid, 266 Warming Buildings by Hot Water. of plain pipes inserted each end into socketed holes in the boxes, the joints between the two parts being made with iron borings as described (p. 222). Another decidedly better Fig. 161. Fig. 162. arrangement is to use an expansion joint, as described, with piping joints. This permits of much easier and more rapid erection. Fig. 162* shows one of these of a very good form. All coils and ordinary radiating surfaces are best made of cast iron. The usual objection to what are called coils is their unsightli- ness. They may be suited for warehouse work, workshops, and such like, but few people adopt them in exposed positions for halls* rooms, or public places without a casing, and this latter arrange- ment has several drawbacks. In the first place, a coil case, even of a very open pattern, obstructs and retards the passage of radiant heat, not seriously, perhaps, when once it is all hot and in full working order, but at first starting, or at any time when heating up, it delays results considerably. Another argument is that when a case * From the catalogue of Messrs Jones and Attwood, of Stourbridge. Coils and Connections. 267 exists around a coil the total results are considerably lessened and this is nearly always the case, although the cause is not what it is usually thought to be, the real fact being that coils (horizontal pipes) collect dust rapidly, and when in a case they are not kept clean, and this accumulated dirt is a great barrier to the free distribution of heat. A coil cased and one uncased always give different results from this cause, as the latter would, as a matter of course, be dusted regularly, which atten- tion the former does not have, especially as most coil cases have their parts screwed up, and a workman would be needed to take it down. Amongst workpeople there exists a considerable difference in opinion as to where the pipes should be connected into a coil (or radiator), some being very desirous of putting one of the pipes into the top, or near the top, and the other out at a lower point, as Fig. 163. This would give very good results, Fig. 163. but it is quite unnecessary, for both pipes can be carried in and out at the bottom with the best possible effect, as will be seen further on, but when it is convenient to carry one pipe in at the top it can be done so. If a branch flow and return is carried to the coil it could be connected as Fig. 164, or if the coil was wholly on the return, then as Fig. 165. Coils and coil pipes can be had in nearly every conceivable design, ornamental and otherwise. Gothic and ecclesiastical patterns are obtainable for church work. 268 Warming Buildings by Hot Water. In calculating radiating surface of coils, the aggregate length of pipe can be easily got at, and the box ends can be calculated as two lengths of pipe. Fig. 164. Fig. 165. RADIATORS. The radiating surface of the majority of radiators would be very difficult to measure, so the makers' lists must be referred to to ascertain their value in this respect. Fig. 1 66 * illustrates a very neat pattern which the writer has had considerable experience of and found successful. It holds but very little water, compared to a pipe coil, and is rapid in results. These can be had in pedestal form either square or round, with marble tops, or half circular to rest flat against a wall. * From the catalogue of Mr. W. G. Cannon, London Road, London, S.E. Radiators. 269 Fig. 167 illustrates another by the same maker, this pattern being arranged for ventilating (air inlet) purposes, the air being brought in through the heated surfaces to effec- Fig. 166. tually warm it, as will be referred to under ventilation. This radiator has an improved feature, which admits of any of the loop castings being taken off without disturbing the other parts, should one become injured from any accidental cause. Fig. 167. Fig. 1 68 * illustrates the "Universal" radiator, a really good and effective pattern, but in some people's eyes, not of quite such good appearance as others, but this design admits readily of decoration, and the other good qualities it possesses should be taken into consideration. This radiator is very compact, giving a large radiating surface in a small area, the 4-foot size, 3 feet high, being equivalent to 130 feet of 2-inch * From the catalogue of Mr. James Keith, Holborn Viaduct, London. 270 Warming Buildings by Hot Water. pipe. All radiators are made in a variety of heights and lengths, this one being made in sixteen sizes, and is also made double or treble widthways. Fig. 1 68. Fig. 169. Fig. 169* represents another pattern by the same maker as the last, but it differs in being of a highly decorative nature, an ornamental construction in itself. These are also made in various sizes, and also in pedestal form. * Also from Mr. Keith's catalogue. Radiators. 271 Fig. 170* shows another form of ventilating radiator with an ingenious arrangement to regulate the fresh air inlet at the base, so that either the inflow of air from the outside can be acted upon, or this can be stopped and a valve or flap Fig. 170. in front of the base opened for the air of the apartment to be warmed only. This is of convenience when the room is to be heated quickly, or when the occupants are very few and ventilation by special means is of less importance. This pattern radiator is also made without the ventilating arrangement, in plain and in- expensive form, as the two last, also in pedestal and other shapes. Fig. I/I f is a very neat pattern radiator which, like the others, can be had in SK' .''fo?5ESta&JgV3E^3 K^C'!^5* almost any size. This pattern consists of circular pipes with projecting ribs or gills on the outside as can be seen from the illustration. These can be had for ventilating purposes if desired, in which case the air is conducted through the centre of each pipe, this to some extent limits the ingress of air, but it comes in at a decidedly higher temperature. The utility of the gills or projecting ribs on the pipes has been referred to. Fig. 172 \ is another pattern that can be had either plain * From the catalogue of Messrs. Rosser and Russel, 22, Charing Cross, London. t From the catalogue of Messrs. C. and F. Sanderson, of Mansfield. t From the catalogue of T. A. Heaps and Co., Westgate, Hudders- field. 272 Warming Buildings by Hot Water. or with arrangement for inlet ventilation ; these upright pipes are of hexagonal section, and for ventilation the air tube is passed right through each water pipe. Fig. 171. Fig. 172. Radiators do not vary very greatly in price in the different makes, but they all run a little more expensive than coils, Saturation of Air. 273 Fig. iy2A. which extra expense, however, is fully compensated for by the non use of a coil case, which is not considered requisite. In completing the list of radiators it will be well to show one of American make, Fig. 1 72 A*. This has an excellent appearance, and its construction bears considerable evidence that the people of that country are in advance of us in the manu- facture of such appliances. The proportion of heating surface to the quantity of water held, how- ever, is not so favourable for quick results as some of our designs, but of course quick results are not always required, as the disadvantage of quick cooling is always an accompani- ment, as already explained. This radiator is made in three heights, and of any length desired. With those radiators that have a connection with a fresh air inlet, it will be understood that the warming of the fresh air introduced does not render the general radiating effect of the appliance less effective ; for instance, those which have air passages right through the water tubes still radiate heat and communicate heat to the surrounding air from their outer surfaces almost the same as if the inner tube did not exist, * From the catalogue of H. Munzing, American Merchant, 199, Upper Thames Street, London. This firm has an ingenious " Hot Water Regulator " for controlling the flow of water in a service pipe, so that the speed is checked when the temperature is high, but allowed to become normal as the temperature is lessened. This action is automatically brought about by the linear expansion of the service pipe as heat is imparted to it by the water within. It is a useful idea, and if not ufc present, there will be undoubtedly a greater demand for such a device at some future day. T 274 Warming Buildings by Hot Water. but it must be always remembered that the inner air tube adds to the total radiating surfaces, and a much more power- ful boiler would be needed for, say, 12 ventilating radiators than for an equal number of non-ventilating ones,* but this would not apply with nearly so much force to those that merely have fresh air passing over their outer surfaces, as Fig. 172. When air is passed over heated surfaces (not necessarily a high temperature) it absorbs heat and becomes, as a matter of course, warmer than it existed outside ; this is the result aimed at, but it introduces an objectionable feature of a some- what peculiar nature, but which fortunately is easily overcome by a simple but proper provision. The objection is as follows : Air that is suitable and pleasant for respiration has to be moist to a varied extent, the variation being in ratio with the temperature, so that cold air suited for breathing may have a percentage of moisture that would be an unpleasantly small quantity if the air was warm or hot : this is quite a recognised feature connected with any system of imparting warmth to air artificially, and it is usually overcome by using evaporating pans or dishes in connection with the heating medium, and some radiators (also stoves) are adapted for this by having water troughs or receptacles made a part of them, these recep- tacles being also capable of holding other liquids than plain water if specially required. The warmed air, in passing by these water dishes, takes up water sufficient for ordinary purposes, and assistance to this end is given by the fact that the water is undergoing evaporation slightly by the heated surfaces around it. If the radiator was of the ventilating kind, and a disinfectant or air purifying material was re- quired to be used, the substance could well be placed at the air inlet so as to be carried in with the air before it was warmed, as the heat imparted usually intensifies the effect of the material ; but probably this could be better judged by the user. * The makers' lists give the surface of the various kinds, so that the boiler power is easily ascertained. Valves and Cocks. 275 This method of warming the inflow of fresh air has none of the objections usually attributed to a hot-air apparatus that has a stove as the heating medium, as we get no odours, no danger, and no objectionable features with the air warmed, except its slight want of moisture, and this is not noticed except in living rooms, and not always then ; it would, as a rule, be very noticeable to any one suffering with bronchial affections. These ventilating radiators can still be used for ventilating purposes when the apparatus is cold, but its action might not be so strong then. This will be again referred to under ventilation. Every radiator requires to have an air-vent on the highest point for reasons already explained, and radiators should not be fixed too closely to any wall or woodwork unless in an unimportant position, as the ascending current of air that is experienced from all radiators or coils will cause a dirty smudge-like mark where the current strikes or impinges, this mark being caused by the fine dirt material that is carried up by and in the air, and impelled against the brick or wood surface in question. A description of air cocks and vents is given on p. 49. The stop-valves used in this work differ in character from those for horticultural works, as firstly, they require to be quite water-tight when closed, as a very small opening would permit of a tolerably free circulation setting in past it, and secondly, cost has not such an important meaning in these works as the valves are so much smaller, J-inch, i-inch, and I J-inch being very usual sizes, and larger are seldom required, except by those firms whose specialty is large undertakings, and then larger sizes would be in more common use, but at the same time the question of cost is not considered so much as the question of good quality in such instances. There is a screw-down valve, known as "Feet's patent," very commonly used, as it has the good qualities of a perfectly full and straight way through it, and the price, for a good quality tap, is much less than a plug cock. Fig. 173 illustrates the valve in question, but it has to be pointed out T 2 276 Warming Buildings by Hot Water. Fig. 173. that a valve of this description, if left closed for a consider- able time, will become stuck fast and immovable, as the faces of the metal parts will oxi- dise together, and a deal of trouble will then be experienced; but if the valve has regular use it will be found satisfactory. The construction of this valve permits of the stuffing- box being taken out and put in order without emptying the pipes, as this part can be taken away and the valve still fulfil its use, although it could not be worked while the stuffing- box was absent. A full way stop-cock is also very commonly used in this work, this being a plug cock of ordinary appear- ance, but the passage through the plug, instead of being a mere slot, is a full circular hole as large as the bore of the pipe, so that there is no check to the circulation, and the passage right through from end to end is straight. This cock is worked with a key, not screw down, and an illustration on a later page will show how a double-ended key can be used with cords or chains if desired when the tap is near a ceiling, but this arrangement is not of great value in these works, as the cocks require but very little attention. This is an expensive cock. There are very many other cocks that are used in these works, but very few have the advantage of a straight way through them, which is desirable, and not all have a full way, which should certainly be looked for, otherwise a i^-inch cock may only fulfil the duty of a i-inch one. 277 CHAPTER XV. QUANTITIES. Hood's rule and suggestions, and their application Calculations of cubical capacity Varied circumstances to be considered Table for rapid calculations. HOOD was unfortunate in adopting his rule, p. 238, for living rooms and public places, by allowing five cubic feet of warmed air per minute to each person occupying the place when it had its full complement of people in it. This allow- ance, as a rule, was insufficient, and very uncertain, and Hood recognised the fact, as in a later paragraph he points out that the rule does not allow for variation in cubical contents, and, accordingly, he compiled a Table for rapid calculation based upon cubical contents ; but one or two authors go to quite unnecessary lengths to point out and dwell upon the fault of the rule referred to, ignoring the fact that Hood pointed out the fault very clearly himself. It will be quickly recognised that allowing so much air per person will hardly suffice, as if we take ordinary living rooms, how these vary in size in one house, yet the same number of people use them all or many of them, and the quantity of pipe for one room would not be suited for another room if their sizes disagreed to any noticeable extent. Or, if we speak of a church, this may be the same length and width as a lecture hall, but there would probably be a great dis- similarity in height. We should get more exact results by calculating upon the wall surface, as we do with the glass in glasshouse work, but even this would not give us exactness. The only means of ascertaining the quantities of pipe or radiating surface in this work is to calculate upon cubical 278 Warming Buildings by Hot Water. capacity, allowing so much pipe per 1000 cubic feet, the quantity of pipe varying in ratio with the temperature re- quired. As, however, we spoke of a want of exactness in Hood's rule or the other suggestion made, it is necessary to point out that no desirable degree of exactness attends this method, for circumstances vary so greatly, the variation, how- ever, being chiefly confined to position, and to quantity of glass, as the cubical contents tables are based upon the existence of very little glass practically none at all and upon the position of the room or building being normal, that is, not very exposed, not naturally damp, and that which lends itself to being heated successfully. The table now about to be adduced is therefore only to be adhered to when the conditions are what may be called normal : no particular exposure to bleak winds, no per- sistent dampness, no unusual degree of ventilation (except in drying closets, where free ventilation to carry off moisture is as needful as heat, but which is allowed for), and particularly no unusual quantity of glass, windows, or lights, &c. If any of these irregular conditions exist allowance must be made for them ; no rule can be laid down as to the degree of allowance needed ; it must be left to the engineer's judgment,* and if in doubt let the error be on the side of too much rather than too little pipe. The following table is based upon the temperature of the water in the pipes being about 180 F. and the coldest external temperature being 20 F. The quantities can be considered correct under ordinary conditions, but care must be taken to see that no unusual circumstances exist ; if they do more pipe must be allowed, and this allowance should be liberal, to secure the best results, and as this table represents very nearly the least quantity of pipe that will do the work, it is better, when * The writer had occasion to heat a room about 20 feet long by 18 feet wide, in which there were three windows, averaging 9 feet by 7 feet (high casements), one window on each of three sides, as this room projected out from the main building. The room faced the north ; and what with the exposure and the quantity of glass, double the regular quantity of radi- ating surface was only just successful in heating the place when the weather was bitter. Quantities. 279 possible, to increase the amount even up to 20 per cent, par- ticularly when the apparatus is attended to by a person who has many other duties to perform, and may not give a full amount of attention to the fire, by which the heat of the water in the radiating pipes will not be kept up to 1 80. The quan- tities given are for four-inch pipe (one foot being equal to a square foot of surface) ; for three-inch pipe add one-third to the quantity, and for two-inch pipe double the quantity. Temperature required. Quantity of 4-inch pipe required for every 1000 cubic feet capacity in a brick-built apart- ment or building. Some of the uses for which the temperatures may be required. The different uses varying the quantities. o 50 feet. 6 Coach-houses, &c. 55 7 Stores, workshops, &c. 60 8 to 9 Churches, public places, and sleeping apartments. 65 10 Living rooms, &c. 70 35 Drying rooms for paper, herbs, &c., &c., to which 75 45 there is free ventilation. This temperature when 80 60 empty and dry. 100 no no 140 f Drying rooms for very damp substances, for drying linen, general laundry work, &c. Full ventila- 120 1 80 tion. This temperature when empty and dry. To keep these latter high temperatures the boiler requires different and proper attention, as the water should be kept nearly at boiling point, pipes in channels or trenches covered by a grating, or encased in any way, must be increased in quantity by 25 per cent, to attain the same results.* When air is warmed before it enters, by contact with pipes in closed channels or chambers beneath the floor, a greater allowance of pipe is needed. But this will be spoken of more fully hereafter. * This is an allowance nearly always necessary in church work, and it also occurs frequently in living rooms, when even the best radiators may be considered unsightly, and coils have to be placed beneath the floor. 280 Warming Buildings by Hot Water. CHAPTER XVI. EXAMPLES OF LOW-PRESSURE APPARATUS FOR BUILDINGS. IT is proposed to adopt the same method with these examples as with horticultural works, viz. to give a few varied ways of carrying out the work, commencing with the smallest ; as those who refer for information may be as much in want of such description as of particulars of larger works. This is indeed more likely to be the case when we remember that there are more small undertakings entered into than large in building works ; the reverse applies more to glass-house work. In these examples, also, it must not be taken that they represent copies from which works could be undertaken, but are repre- sentative methods only, to show the general principles that have to be followed out, very many circumstances governing the way in which the pipes have to be carried, the position of the radiating media, &c., &c. Illustrated examples make these works much more readily understood by the unskilled, which is one of the chief reasons for introducing them here, although it may never fall to a reader's lot to erect an apparatus precisely like any one of them. Fig. 174 represents a little apparatus that is frequently fitted, with the object of giving some warmth to a room adjacent to that in which the fire is a library or ante-room, which does not have sufficient use to need a fire in it regularly, yet which should not be without warmth. Sufficient heat could be obtained this way to keep a small billiard room from becoming very cold, although it would not be sufficient to make it anything like comfortably warm unless the weather was quite mild. This illustration represents a three-pipe coil of f-inch pipe, Examples of Apparatus. 281 to be placed at the back of an ordinary living room grate fire, the pipe continued from there to a radiator or short length of hot-water pipe in the adjacent room in question, in a manner something similar to that shown. The top pipe of the coil Fig. 174. is continued as a flow pipe, and the lower is connected with the return, two unions being inserted at the points shown just above the coil, so that this latter article can be disconnected if desired, and taken out without disturbing the grate or the general service pipes. It may be necessary to take the coil out at some time, as no means can well be provided for cleaning it, and the accumulated sediment will eventually bring about its destruction, but under ordinary circumstances the coil should last in good order for, say, five or six years, provided it was made of good quality tube (steam quality). The amount of work this little coil in the fire is capable of doing cannot well be fixed, as it will depend entirely upon the size of the fire and the way the fire is attended to, but a fire-box 1 5 inches wide, which holds a good body of fuel, wholly sur- 282 Warming Buildings by Hot Water. rounded with fire-brick (an important feature in keeping a very hot fire), will successfully heat from twenty-five to thirty-five feet of radiating surface. This, however, brings us to consider what is sometimes a drawback to this arrangement and what limits the size of the coil, as otherwise a larger coil could be used with pro- portionately greater results. In introducing a coil of water pipes into an open grate fire we bring about a cooling influence, so that, in the case of a small sized or thin fire, holding but a small body of fuel, we have the greatest difficulty in keeping the fire alive ; and sup- posing the fire can be kept going, that part around and in contact with the pipes will be deadened and nearly black, the fire itself loses its cheerful appearance, and the heat contributed to the pipes will be but little. If the fire is of good body these drawbacks still exist, but in a much reduced form, and the application is practical, although in limited sized grates, even with deep fires, it is better to reduce the size of the coil to two pipes, or even one pipe passed straight through the lower part of the fire at the back would heat a small radiator, supposing only a small amount of radiating surface was needed. A small radiator could be used to assist in heating a large room which was not quite sufficiently heated by its own fire-place. It will be understood that the reason why the coil has such a deadening effect on the burning fuel is not only due to the great heat absorptive power of the water, but we may say chiefly to the fact that the description of grate referred to is an open one, and not a closed stove ; with this latter much greater results could be effected ; see coil boiler, p. 169. This apparatus requires some arrangement for filling ; the illustration shows a vase-shaped vessel on top, which can be fitted to act as a filling cistern, and would serve as an air-vent also, although it would be desirable to have an air cock at some other high point on the radiator, to allow free vent for the air when first filling ; it would not be needed afterwards. If the fire was a very large one i-inch pipes might be used with increased effect, or, if it was so small that only one straight Examples of Apparatus. 283 pipe through could be allowed, this might be I inch. In any case they should rest against the back brick and be low down in the fire. The illustration shows the radiator behind, and above the level of the fire. If it was on the same level the pipes would have to be carried sharp through the brick behind ; this would not be quite so simple, but facilities could still be arranged for disconnecting on the other side of the wall. It might be mentioned here that all coils and radiators can be connected in through the bottom at each end, as Fig. 175- Fig. 175, if desired, and by this means no portion of the pipe, or the points of connection, will be visible, the pipes passing under the floor ; but this cannot always be done conveniently, neither is it always a good arrangement if there is a stop-cock to the coil, as there would be no place for the cock to be put in sight. The cock, however, could be worked by a key through a hole in the floor. The next illustration, Fig. 176, is an apparatus on just a little larger scale, and which would most probably be worked from a small independent boiler.* This represents two full- sized radiators (or stacks of pipe if desired, which, however would have to be encased or hidden) in a large entrance hall. The positions would be fixed by various conditions, staircase, doorways, &c. If fitted with marble tops, radiators can be used as tables for visitors' hats, but it would not be desirable * Sometimes one or two small radiators can be attached to a domestic supply apparatus, see p. 329, and note the objectionable features that the practice introduces. 284 Warming Buildings by Hot Water. to utilise them for this purpose if they have iron tops, as the heat might affect the shellac material of which the hats may be partly composed. Fig. 176. These two radiators are supposed to be exactly on the same level, but one is further away from where the pipes come up through the floor than the other, but if the difference in distance is not very great there is no need for stop-cocks, as a trifle more rise to the pipes leading to the distant one will equalise their working, and this rise can generally be arranged without difficulty. If possible, it will be best, as every engineer under- stands, to carry the horizontal service pipes* along beneath the ceiling of the floor below, and not just beneath the floor boards upon which the radiators rest. This latter way would probably involve cutting the joists a great deal, would not admit of but a trifling rise to the pipes, and entail much more work. If it is desired to give one radiator a better rise in the pipe than the other (both radiators on the same level) it can be effected as Fig. 177. This could be very easily done in running the pipes along the ceiling below, assuming it is only cellarage or kitchen offices there. * As mentioned in horticultural works, horizontal pipes are spoken of as those which are carried nearly horizontally ; there should be, correctly speaking, no pipes in these works that are exactly horizontal. Examples of Apparatus. 285 The cold supply would have to be provided for by a small cistern. This could be placed in a cupboard, or in any out-of- the-way corner, but it need not be more than twelve inches above the radiator tops unless Fig. 177. it be desirable to put it a little higher to get it into a non- - conspicuous position. It may * ' be connected into any of the return services, but there should be the necessary dip or inverted siphon somewhere in its length (see p. 55), as near as possible to where it is connected into the return pipe, and the less length the cold supply pipe is the better, to avoid the unnecessary cost and the risk of stoppage by accumulated dirt. The cistern should have a cover to keep dust from entering. Each radiator requires an air-cock. The pipes in this apparatus might be I inch from the boiler to the junction, and f inch from there to the radiators. These sizes would be quite effective, but if they were i^ inch and i inch respectively it would be better, unless the distance was very short, or lowness of cost was of importance. The very smallest boiler would probably be found sufficient for these. Fig. 178 shows a little larger apparatus which we may suppose heats two rooms of unequal size, somewhat widely separated, so that the service from one could not be continued across to the other, and which therefore have separate services to each, the boiler being situated somewhere between. In this apparatus, as in the two last, the rooms to be heated are only a few feet above the boiler. This, however, makes no difference in the actual working of the apparatus, and if the rooms were two or three floors above the boiler the arrangement would be carried out the same, except, perhaps, that with a low apparatus which would also use less pipe in the mains, we might use a little larger pipe than otherwise, first, as the motive power is less, and, secondly, as a difference in size does not make a great difference in cost when the quantity is limited. In the preceding apparatus the flow pipes were shown 286 Warming Buildings by Hot Water. Examples of Apparatus. 287 entering one end of each radiator, and from the other ends returning to the boiler. Now, this principle can usually be adopted only when there is a distinct service pipe to each radiator, as there shown, and as also shown in the left-hand room in this apparatus ; but in the right-hand room the two radiators are shown both directly connected with the main. If we cause the water to pass through one radiator before it can reach the next, as Fig. 179, we must expect this latter one to Fig. 179. be longer in becoming hot, and although there is, as a rule, no grave objection to doing this with just two radiatois, it would certainly be objectionable if there were more than two ; for if there were, say four, as in the left-hand room, the last one would probably come poorly off for heat, this depending, how- ever, upon the size, i. e. the radiating surface and contents of each radiator. If the stacks of pipe were of fair size most unequal results would be caused. As just mentioned, there is a distinct branch flow and return service to each radiator in the left-hand room, and they would be connected as in the apparatus shown preceding this Fig. 1 80. (Fig. 176). In the right-hand room radiators should be con- nected differently, as Fig. 180, the flow pipe rising into, and then proceeding from, each radiator, but without stopping the 288 Warming Buildings by Hot Water. free passage of water through the main flow passing beneath them. If preferred, the connections could be made to the return, instead of the flow ; the same results would be obtained in either case in this instance. Sometimes the radiators are connected to both flow and return, as Fig. 181 ; this, in the writer's opinion, is an Fig. 181. TT objectionable practice. The objection is not so great, perhaps, with two radiators, but in a long straight run of horizontal pipe with several coils or radiators in connection with it, the circu- lation has commonly been known to " short circuit," that is, to circulate through the first and second coil, leaving the water beyond this point in effect stagnant. There is every facility for the water to circulate through one coil and return to the boiler to the prejudice of those beyond it, if any incidental circumstance inclined the apparatus to act in that way. With the method of connecting wholly to one pipe, this result is im- possible, and there need be no fear of the water not heating in the radiators, as you cannot anyhow get cold water to rest above hot water if there is free communication between the two. This argument will not apply so strongly when the mains or services which are connected to the radiators are vertical (not a common occurrence), as will be gathered from the examples that follow this : In the example under discussion there is no need to put stop-cocks to each radiator or coil, the four in the left-hand room, although it is just possible they may start heating a little unequally, will, when in full work, act regularly and satisfac- torily. The same remark applies to the two on the right. There is, however, a necessity for stop-cocks, one in each main Examples of Apparatus. 289 flow, to divert the circulation in either direction as required, or in case one direction acted too freely and the other too sluggishly, as- is very possible, particularly if on one side the apparatus extended a floor higher than on the other. The best and most convenient place for these cocks would be down by the boiler, as shown. If desired or necessary, the main in the left room could be run all round instead of up the centre, as illustrated ; the radiators would then be connected, as Fig. 180. If the room was very large, as we may suppose, the radiator that first received the hot water would distribute the greatest heat, but this quality could be utilised by arranging for the radiator to be in the coldest part of the room, if the room was colder at one part, or had draughts entering at some point. It should also be mentioned that if either of these rooms were living apartments and highly decorated the best of radiators might be considered unsightly. In this case they, or plain coils, can be placed under the floor in boxes. In placing coils in boxes they would be braced up to the joists which support the floor of the room to be heated, as Fig. 182, as it is supposed that no provision has been made and Fl - l82 - exists for the coils to come im- mediately below the line of floor boards (by trimming a space within the joists), and that no provision exists for running pipes beneath the floor in a straight line with gratings over. With a coil against the joists as shown, the box* forms a projection on the ceiling underneath, which is only admis- sible if this lower room be very unimportant a kitchen or servants' office. If it should happen to be a kitchen the box must be very air-tight or the odours of cooking will be upstairs with great rapidity when the apparatus is hot. A grating * These boxes can be made of wood, or lath, or wirework, cemented over and whitened with the ceiling below. U 2 go Warming Buildings by Hot Water. (brass for preference) must be inlet into the floor of the room to be heated, and this grating should be of good size, as it has to act both as an inlet and an outlet to the air that is warmed, and its pattern should be as open as possible, and strong to bear walking upon. The box could be arranged for admission of fresh air if desired, but in any case it must not be forgotten that radiating media beneath floors, &c., are of less efficiency than those exposed. The coils that lie on their sides beneath floors must be slightly tilted, the pipe connections being made at the lowest point. They must also have the necessary air vents, but these may be small pipes carried down to the floor below, terminating with a cock, which, of course, will allow of the air being dis- charged in the same way as if the cock was screwed directly into the coil. The cold supply would be provided for by a fair-sized cistern, placed at any point just above the highest radiator, and connected into any of the returns with the necessary siphon. Air cocks must be fitted to every radiator, and in an apparatus of this size (and in the preceding one also, if con- venient) an expansion pipe of, say, i-inch pipe, should be provided ; off the main flow, just over the boiler, would be a good place ; this pipe extending to above the level of the supply cistern. The object of this is to allow free escape of steam if the apparatus be over-heated, as may very likely happen in this case, as the boiler would probably be tended by a lad employed in the house. The over-heating would not be a source of danger even without the expansion pipe ; but if this did not exist the boiler would relieve itself by way of the cold supply pipe and flood the place. The pipes in this apparatus not extending a very great distance, as usual in a residence, might be I i-inch for the short piece of flow just on top of the boiler to the junction shown a few inches above, i^-inch flows (and returns) from thence as far as they constitute mains, and the branches from the mains I inch, or even J-inch if the radiators be rather small and within, say, 9 feet of the mains in question. Examples of Apparatus. 291 Fig. 183 represents an apparatus which we may suppose is devoted entirely to heating three landings, or short corridors, situated one above the other as shown. The chief object in Fig. 183. showing this is to illustrate a feature that is very prominent in nearly all works that extend some distance in height, viz. the connection of the radiating media wholly to the return of the mains. It is usually contended, and Hood bears out this U 2 292 Warming Buildings by Hot Water. contention, that if an apparatus like this were erected with all the coils connected to the flow, there would be a probability of the circulation starting up the wrong pipe from the boiler, owing to the much greater quantity of water there would be to move in an ascending direction (in the flow and its attach- ments) than there would be in the contrary way down the return. On this account the greater bulk of water would be expected to offer some extra resistance to the upward flow of water, and so cause it to choose the passage that offered the freest way. This argument is sound, but based very greatly upon theory. The chances are that this might have happened sometimes,* but certainly not if a good distance existed between the flow and return at . the points where they are con- r |0 nected into the boiler. How- U U ever, as a risk may sometimes exist, the argument may be be- lieved in, especially as we can get quite as good, and almost as quick, results by utilising the return pipe ; therefore in an appa- ratus like this the principle should be adopted, as also in any other apparatus of a similar character, supposing it to be possible. If circumstances permitted, a saving of pipe might be effected by running the return pipe as Fig. 184, and, as a matter of course, we should, by decreasing the length of the pipe, cause the results, particularly with the lower radiators, to be much more quickly arrived at. With this apparatus a tank is shown at the highest point, this being a very practical arrangement ; it need not be large, * The writer has never tested this argument, as the return pipe acts well, and leaves little room for improvement. Examples of Apparatus. 293 say, 20 gallons, and the supply cistern at side arranged to fill it just a few inches up ; this gives room for expansion, and prevents water being ejected if the apparatus over-heats. This tank might have a loose-fitting cover, or it might be a close tank with a good sized steam pipe carried from the top of it as shown, this pipe being turned into a roof, or better still, through an outer wall. Each of the radiators or coils in this apparatus should have a stop-cock. These need only be f -inch, unless the coils happen to be fairly large ones, when I inch would be better. One cock will not entirely prevent the radiator getting warm after a time, but this is of no importance, as the cocks are only provided to check the circulation when the coils may be giving off too much heat, or if it is found that the top radiators heat much more than the lower ones. None of the radiators would require to be shut off entirely, as it is to be supposed, if no heat whatever was required, the fire could be let out. Two cocks could, of course, be put to each radiator if required. A very desirable thing in an apparatus of this size is to cover the mains (particularly the flow, which conveys all the heated water a good distance without its doing any work) ; if they are not covered (see p. 120) there will be a great loss of heat, and there will be a proportionate decrease of heat at the points where it is wanted, and for the purpose that the apparatus is erected to fulfil. The fact of all coils being connected to the return makes it more than usually necessary for the mains to be protected, as the water, when it is hottest, has to travel a good distance before it can do any good. It is only at the radiating media that radiation should be per- mitted. An air vent would be needed upon each radiator at the highest points as usual. The size of pipes might be i^-inch for the mains, or ij-inch would suffice if the corridors were but short, or with only one radiator each. For the coil connections I inch or f-inch, according to the size of the coil ; the cold supply f -inch, with the usual dip or siphon ; and the expansion pipe 294 Warming Buildings by Hot Water. might be \\ inch, turned down at the end to prevent dirt falling in. For the last mentioned reason also the supply cistern should have a lid. Fig. 185.* In Fig. 185 we have an apparatus in which we cannot utilise the return pipe in the way laid down in the last * This illustration will only permit of the " flow " pipes being shown. Examples of Apparatus. 295 example, as, in the first place, this undertaking is on too large a scale, and we can never adopt the method when radiating pipe is used, as shown on three floors, instead of coils or radiators. This illustration is intended to represent four floors of business premises^ heated from one boiler, and with one main flow and return only. The recognised objection to this example is the vertical mains, for in these the circulation is very rapid, and inclined to pass by the horizontal connections, and not through them. This objection is well founded, but only in a limited sense, as it only exists when the apparatus is being heated up, at which time it would be, perhaps, considerably longer before the radiating surfaces were fully hot, than it would be if some means existed for diverting or causing the first heated water to enter the horizontal services in question. When, however, the whole apparatus is once heated the objection is disposed of, and it may be concluded that it will not readily recur, as an apparatus on this scale would not have the fire put out except for mild and warm weather. Therefore, in general, the objection in question cannot be held to count, as all the radiating media will be found to heat properly, but not so quickly at first lighting as might be expected. A suggested remedy is to use an elbow and T-piece in the flow at each branch service, as seen in Fig. 1 86, but this does not recommend itself on the score of convenience, nor sightly workmanship. The illustration shows the lower floor heated by hot water pipes ; 3 inch would probably be best, in a channel beneath the floor-level covered with a grating. This needs no further explanation except to point out that the usual extra allowance of pipe for trench work must be made. The grating just over the stop-cock should be easily removable, as the cock would be placed in the trench. If there is much foot traffic across the grating at any one point, and it is found slippery and unsafe, a mat could be placed over it just there. The whole of the gratings should be removable for cleaning the pipes, and the 296 Warming Buildings by Hot Water. trench must not fit the pipes at all closely. All these latter points have been explained before. On the next floor a set of radiators are supposed to be adopted, these being shown connected to the flow of the branch service. In this case there is no objection to their being on the flow, although the results would be almost as good if connected to the return. A stop-cock would be needed in the flow, at about the point shown, with some easy means of using it, and a stop-cock might be fitted to each radiator if circumstances made it desirable. The two top floors, which we may consider to be store or work rooms, are heated by plain pipes, 3-inch or 4-inch, exposed and carried round whichever way is most convenient to avoid doorways, &c. The flow of these pipes would be connected to the main flow, as on the two other floors, and returned into the main return ; each branch flow having a stop-cock, somewhere close to where it is connected with the main, as shown. Each branch service of radiating pipes would require an air vent at its highest extremity, and each radiator would need an air cock as usual. The size of main and branch pipes must be proportionate to the increased size of the apparatus. Accurate sizes can hardly be given, as it depends entirely upon the quantity of pipe and radiating surface; suggested sizes for this example are 3-inch mains, which might be reduced to 2^ or 2 inch above the second floor ; 2-inch connections between the mains and radiating pipes on first floor; ij- inch branch service to supply the radiators, but only I inch from this branch service into the radiators ; i^-inch connec- tions between the mains and radiating pipes on the two top floors. It is very necessary to point out that it would be decidedly better if two distinct sets of mains could be carried up ; this would give more regular and quicker results than the one set of mains already referred to, which were only shown as an example, and upon the supposition that only one set was permissible. If the two sets cannot be conveniently carried Examples of Apparatus. 297 in two directions, which is not absolutely necessary, they can be carried up together, the branches from one set taking one side of the building, and the other set the other side. There is one well-known engineer in London who, when- ever he can, carries a distinct flow and return from the boiler to each floor, and the practice ensures excellent results, but is not usually possible for various reasons, such as cost, the appearance of the stack of pipes,* &c. No one, however, could find fault with the way in which the apparatus would work. If the mains are doubled or trebled in number, they need not be so large, the size decreasing with the increase in quantity. The size must be left to the judgment and ultimate experience of the engineer, as no suggestion can be made that will be found accurate in every case, and it must be borne in mind that the sizes already given may require varia- tion under varied circumstances. In this respect no written information can be thoroughly reliable as being applicable to all cases. Sometimes one main return can be made to do duty for two flows, or even for three if the return be of a little larger pipe, there is no objection to this ; neither would there be any drawback to one flow serving for two returns if the services are wholly connected to the latter. One 2-inch pipe would readily serve two pipes of the same size, as at all times the circulation is very rapid, this being the reason that the connections between mains and radiating pipe may be small, as already mentioned. All non-radiating surfaces should be covered with some poor heat-conducting material. In dealing with churches, chapels, lecture-rooms, and public halls, we have commonly to consider some of the features that exist in horticultural works, chiefly that of low motive power. In nearly all the works mentioned small main and connecting pipes are generally prohibited. If a * The pipes would be smaller proportionately with the increased number. 298 Warming Buildings by Hot Water. church, there will probably be one set of 4-inch or two of 3-inch mains from the boiler to the trench pipes, or if the heat is distributed by stacks of pipes, coils, or radiators, the mains will then probably require to be 3-inch, unless the place be of but moderate size. In these works a result usually sought to be attained is the quick heating of the place, that is, in the shortest possible space of time after the fire is lighted, as it is not usual to keep such apparatus going day after day * when the place is not in use. Consequently, it has become customary to arrange for warmth to be quickly supplied, almost at any moment, or at least in a few hours after the fire is lighted. This end is arrived at by using smaller radiating pipes (in proportionately larger quantity), as it will be seen that although two 2-inch pipes have the same radiating surface as one 4-inch, they do not hold so much water, and the less the bulk of water the quicker it becomes heated, if we suppose a boiler of equal size to be used in each case. It might be profitable for some one to introduce a pipe of special shape for this work, having a greater radiating surface in proportion to its contents, but much judgment would be required to secure success, as too small a quantity of water would cool (i. e. lose its heat) before it had completed its circuit, and it would not do to have some part of the return pipe cold. The pipe could be of a shape that would not readily collect dust. It is not intended to suggest that all such works are carried out in small pipes, but only those in which a particular wish has been expressed for rapid results. For instance, in a public hall or lecture room only used at irregular periods. The majority of church works on a good scale have the usual 4-inch pipes, and the fires are lighted the day before the place is required for use, if the fires are not kept alight perpetually, as is necessary when services are held daily or three or four days a week. The major portion of church work is carried out in trenches, * Many churches are an exception to this, as services are held almost daily. Examples of Apparatus. 299 as exposed pipes cannot always be tolerated. The question of cost, too, frequently governs this, as trench work is rather costly. But this arrangement is not always practicable, as it may be difficult to get the boiler low enough. In such a case the flow pipes are carried along the walls of the building and the returns brought back down the centre in a trench. In heating an old church, however, another difficulty may present itself in the fact that trench work may be found impossible, as vaults may exist along the aisles ; in such a case exposed 'pipes or radiators, or coils beneath the floor at certain points, have to be resorted to. It must not be forgotten that, although we obtain heat more quickly with small pipes, or any pipes hold- ing a small quantity of water, we shall just as quickly lose the heat as the fire goes down. Sometimes it is more convenient to adopt a combination of two or more methods, say trenched pipes and coils, as although in many cases the former of the two is perhaps best for the body of the building, it would be very desirable to place a coil or coils in the entrance lobby or way, or wherever the cold air may be found to have free ingress and cause draughts. Coils or radiators will generally be found best for cloak or ante-rooms, vestries, &c. Suggested methods for carrying hot water pipes either in continuous runs or in mains and branches, have been shown, and also the connecting up of a series of radiators or coils ; if, however, it be desired to connect up three parallel rows of pipes in trenches, it can be carried out as Fig. 1 87. This shows the mains with a fairly good rise up to the further branch a very desirable arrangement where possible. It must also not be forgotten that the branches in the trenches must have the customary rise to the furthest extremities, as fully explained with glass house work, and all the needful precautions as to expansion, joints, &c., &c., require consideration, as has also been fully treated. The apparatus just suggested should have an expansion pipe from the boiler or main flow, as the services would have air cocks, not air pipes. The supply cistern, of a sufficient size, must be placed in some convenient spot a little 300 Warming Buildings by Hot Water. higher than the highest point of the radiating pipes (or coils) and connected into a return pipe ; the main return would pro- bably be convenient for this. There would be no need for stop-cocks or valves, unless some special circumstance had to be considered. As just mentioned, it is sometimes impossible to lay the pipes in trenches in church work owing to the existence of vaults, &c., and if exposed pipes along the wall were con- Fig. 187. sidered particularly objectionable, it could be arranged for stacks of pipes, laid flatways, to be placed in shallow pits here and there, if there was a possible way of carrying the con- necting pipes from one to another. These pits would probably have to be put in the aisles, but even there they are unpleasant in effect, as the seats near them receive a more than comfort- able share of heat. They are covered with gratings, and act in the same way as coils placed beneath a floor, p. 289, and may have fresh air conducted to them if desired. In any case the pipes must be calculated at a less heat-giving value than those that are exposed ; about the same allowance as for pipes in trenches has to be made. CHAPTER XVII. HIGH PRESSURE APPARATUS. Phenomena of Ebullition Heating of water in sealed vessels The high pressure system Size of pipe Boiler coil Motive power Expansion pipe and its use Filling Joints Stop-cocks Testing Advantages and precautions Frost Non-freezing fluid Uses of this system Proportions Temperature and pressure table Modification of H.P. apparatus Regulating valve The application of the Building Act- Example apparatus. IT is, of course, common knowledge that the temperature at which water boils is governed by the pressure of the atmo- sphere. When the water is heated in open vessels, or in any apparatus that is open at the top, as a general result the boiling commences at 212, this being when the atmospheric pressure is 15 Ib. to the square inch, viz. at sea level. If we boil water at some distance above the level of the sea, on a mountain or very elevated piece of land, we shall find that ebullition takes place at a lower temperature ; on the other hand, if the boiling takes place below sea level, in a deep mine, the water reaches a higher temperature than 212 before boiling commences. In all these cases the heat of the water at boiling point represents its greatest heat, and it cannot, in open vessels, be made any hotter. This is the case with low- pressure heating works : by urging the fire we can get water at 212 temperature, but no higher.* This goes to show that in open vessels, or any apparatus open at the top, and under the free influence of the atmosphere, the boiling and consequent maximum temperature is limited to about 212. The high pressure system, and any modified form of it, * This is correct in a sense, but see Appendix if further information on this point is desired. 302 Warming Buildings by Hot Water. have their principle based upon the fact that in a sealed vessel or appliance one that has its contents entirely excluded from the influence of atmospheric pressure it is possible to raise water to a temperature far exceeding 212, and without introducing any objectionable features, except such as the great expansive force exerted by the water and other quite natural phenomena which have to be provided Fig. 188. r ' A i i r for. At present there are comparatively few firms who make a specialty of these works, but undoubtedly the number will increase when some of the prejudices that exist (chiefly in the mind of the public) have been disposed of. This j system was introduced about 1837, but it always seems to take a great time for introductions of this character to gain a firm footing, even though they possess merit, as this undoubtedly does. Fig. 193 illustrates a small apparatus of this kind, the illustration being given here to sim- plify the explanation. No boiler is used in this system, as, firstly, it would be a source of weakness ; and, secondly, it would not present such valuable heating surface as a coil of small pipe. There is no need to fear that failure may ensue owing to the small pipe being choked with deposit or dirt, as the apparatus being made perfectly air and water-tight (to withstand a high pressure) that is obviated, it being impossible for any such accumulation to occur. The pipe, forming the boiler, is coiled into any form to suit the shape of the fire-box, very usually square or oblong as shown ; the lowest pipe is connected with the return, while the top pipe is continued as the flow. The pipe constituting the boiler, that used as services, and that which acts as radiating medium, are all of the same size and material, the whole being alike from top to bottom except the expansion pipe that will be referred to. High Pressure Apparatus. 303 Sometimes, when the work is of such description or magni- tude that two or more flow pipes are considered necessary, the pipes forming the boiler are made up in two or more sets, inter-coiled with one another ; or some engineers prefer to use branch services from the one boiler coil, no rule being laid down in this respect. From the boiler upwards the customary flow and return services are carried wherever required, governed by the same rules and features that have been spoken of fully in low pressure work ; but as the temperature of the flow pipe is very high, and that of the return pipe rather low (comparatively, as with these small pipes the water loses heat very rapidly, also see p. 70) the speed of circulation the motive power is very great, consequently a few dips in the pipes are not considered such great drawbacks as with low pressure works, and not so much thought is always given as to whether a doorway or such obstruction exists in a room, for the pipes can be readily dipped under it if it is any particular con- venience so to do. The great objection to dips in low pressure pipes is that on one side the pipe gets air-locked, as has been explained ; but this cannot happen with high pressure works, as they are first pumped full of water and all air thus expelled, and then sealed up, after which no fresh air can be absorbed by the water and carried into the pipes, as happens in the other cases. At the extreme top of the apparatus, just above the highest point at which the water circulates, is fitted an ex- pansion pipe, a piece of a larger sized tube usually (as shown), or it may be a continuation of the small pipe, only in a greater length, as this expansion chamber has to bear some relative proportion to the size, i. e. the contents, of the other parts of the apparatus. The utility of this chamber makes it necessary to explain one of the chief features in the system, viz. the great expansive force exerted by water at a high temperature, as without confinement under pressure this temperature would not be reached. It must be borne in mind that it is the pressure wholly and solely that permits of 304 Warming Buildings by Hot Water. the increased temperature being attained. At normal atmo- spheric pressure the highest temperature for water is 212; at pressures above that of the atmosphere, water can be heated beyond 212 to a certain fixed extent, as is given in the rule in the Appendix. When water undergoes an increase in temperature, there also takes place an increase in bulk, and this increase may be considered irresistible, for water is not elastic, and an appa- ratus, if quite filled with water and sealed up, would be fractured long before its contents acquired a great heat. To obviate this the expansion tube is provided. In the illustra- tion it will be noticed that the filling opening is situated just above the highest point of the circulation, but just below the expansion pipe ; when the water is passed in by this filling tube, the air is, by the entry of the water, expelled, it passing out through the expansion tube which is kept open at the end when charging. When the whole of the apparatus is charged it will thus contain water up to the level of the filling opening, but there will be none in the expansion chamber, and this is the condition it should be in when the cap or plug is secured, and the hitherto open end of the expansion tube closed, so that before the fire is lighted there is no water, nothing but air in the tube. Upon the application of heat to the boiler the water undergoes the above-mentioned expansion, and having no means of relieving itself in the lower part of the apparatus, it begins to force itself up into the expansion chamber, partially filling -it. In saying it forces itself up into the chamber, a correct term is used, as it cannot enter freely by reason of the air that has been left confined there, and offers resistance to its entry ; but the water possesses the greater force, and compresses the elastic air into less space, and this bulk of air expands or contracts as the temperature of the water, and its consequent expansive force, is lessened or increased. In acting in this way the air does great service on account of its perfect elasticity, as when compressed it exerts pressure upon the water, and by the rule stated permits of High Pressure Apparatus. 305 its gaining the high temperature required, yet by its nature it does not readily permit of a fracture, it acting so excellently as a spring or cushion. It will be seen from this that the size of the expansion chamber could be varied, and so to a modified extent regulate the heat of the water, but this has not been found of practical service, and where it is wished to limit the heat a reduced boiler coil can be resorted to, or a kind of valve used, which will be referred to presently. This valve is much in favour, as it prevents the apparatus overheating, which it is apt to do if tended by inexperienced persons. The pipe used in this work is of small size compared to low pressure works, and is made of wrought iron of a special strength,* the size, material, and strength, all being those best suited to withstand the great strain that has to be borne. The pipe which is almost universally used measures J inch diameter inside, and I T 3 F diameter outside, having a substance of metal of inch bare, being stouter than the steam quality tube referred to on p. 262, and propor- tionately more expensive. The joints are made without Fig. 189. any packing material, one end of the pipe being finished with a conical edge, as Fig. 189, the opposing end being finished flat ; this would not be sufficient only that one end has a * The special pipe for this work is readily obtainable from any good manufacturers. X 306 Warming Buildings by Hot Water. contrary thread (screw) to the other, right and left handed, and -the socket is tapped in the same way, so that in turning the socket the pipes are caused to approach each other, the ends ultimately meeting, and the conical edge impressing itself into the opposite flat edge, and so making a sound joint. A sound joint is very necessary as will be understood, but it has to bear a still greater strain when testing, as it is customary before sealing up to test the whole apparatus to a pressure of from 2000 to 3000 Ibs. to the square inch, so as to ensure its being sound when working, for it should be remembered that the coil in the furnace is considerably weakened by the heat it is subjected to, and that iron is unable to withstand so great a strain when hot as when cool. The small quantity of water that an apparatus of this kind holds, and the rapid circulation together effect very rapid results, and on this account it is especially adapted for very many purposes, but it must not be overlooked that hot water systems which attain their maximum heat rapidly, just as quickly become cool as the fire goes down. This, however^ is no drawback, as it can be readily obviated by constructing the furnace so that it will hold a full charge of fuel, which, with a usual amount of attention to the damper, &c., will heat the boiler coil regularly for a considerable time. The smallness of the pipe also serves another useful purpose, as by its means we are enabled to introduce radiat- ing surfaces in positions where a large cast pipe would be objectionable, or, perhaps, impossible. For instance, in this work the heat-distributing pipes are very commonly placed behind skirtings, in a shallow wood case beneath a window. Also in similar positions (inaccessible with a large pipe) where they can be used for warming inlet fresh air, as Fig. 190. In calculating for these small pipes it does not become necessary to allow three or four of these to do the work of one 4-inch pipe of a low pressure apparatus, as the higher temperature compensates to a very great extent for the reduced size, i. e. radiating surface, and in many of these High Pressure Apparatus. 307 works a pipe of inch internal diameter, is allowed to do the work of one of 2-inch diameter of a low pressure system. It becomes somewhat necessary to run these pipes in unexposed places, not only because they are about as ill- looking as cast pipes, but also because of their heat, which would be felt severely Fig- 190- if touched by the hand, and in public places, however unimportant, this must be guarded against. Coils can, of course, be placed in the customary iron coil cases if it is not desired to place the pipes in channels ; but if channels are adopted this system stands at a little advantage, as a channel of an ordinary width will take six pipes (if needed) side by side, which is preferable to putting pipes be- ; neath one another, as they cannot then readily be kept free from dust, and the lower pipes do not render the service the top ones do. These channels, therefore, need only be about 3 inches deep. This system is never adopted for horticultural works,* as it would not give quite the satisfactory results that we get with low pressure, however well it might be tended. In the first place the greater temperature would necessitate keeping all plants and such life clear of the pipes to more than what would be considered a convenient extent ; also it would not give such an equable temperature owing to the heat of the pipes fluctuating so quickly with the fire,t and many plants are very susceptible to changes of this kind ; further, the great heat of the pipes (300 to 350 for general purposes) is apt to vitiate the air to a trifling, sometimes to a noticeable extent, by decomposing particles of organic matter that may * The writer has never met with an instance. Conservatories are, however, sometimes warmed from the house service. t The particular gain with large pipes in horticultural work, is that the greater bulk of water does not so readily show an increase or decrease of temperature as the fire varies, and the air of the greenhouse is of a regular heat. , X 2 308 Warming Buildings by Hot Water. fall and rest upon them, and although this would not appear in greenhouse work to quite the extent it might in building works, it would still be objectionable in the gardener's eyes. Much discretion must be exercised in introducing stop- cocks in this high pressure system (which has no regulation valve), as it can be readily judged that closing off a good portion of the apparatus, say one-fourth or a third, would practically convert the apparatus into one which had a boiler coil disproportionately large, and the fire would require to be reduced at once, otherwise a much higher temperature would be felt at the remaining circulating pipes with increased strain, and so injury might occur. There is no actual danger to be feared if an apparatus burst. There would be merely a fracture of the pipe, and a violent issue of water (which, if hot enough, would cause injury), but as water is so perfectly non-elastic, we get none of the ill results that would be experienced with steam. It is almost needless to add that an apparatus of this kind, holding so little water, if completed in severe weather, should not be charged unless the fire can be lighted immediately afterwards ; even then it is not a good practice to do so unless it can be charged with a non-freezing solution (see p. 252), for the frost would affect an apparatus like this very quickly, and by freezing its contents not only cause a fracture by its own effect, but cause mischief by stopping communication with the expansion tube. A non-freezing solution is of particular value in these works, as should the fire be left out for one day or the matter of a few hours in severe weather, the damage will be done ; or if a house was left unoccupied the apparatus could not escape unless emptied a very troublesome remedy, as will be understood. This high pressure system is of great use for drying rooms and closets, and it is even applicable to japanning ovens ; all these purposes are fulfilled more effectually by this apparatus than by the low pressure,* but japanning wants the highest temperature of all, viz. about 400. * A low-pressure apparatus would be useless for japanning purposes. High Pressure Apparatus. 309 The proportions of the apparatus, as customarily adopted, are as follows : they will bear variation for special reasons, but it should not be attempted to increase the proportion for furnace coil, nor to decrease the expansion tube, except for some very particular purpose, and under the advice of a com- petent engineer : For the furnace coil, the tube being of the same size as the circulating pipes ; 10 feet to every 100 feet of the other parts of the apparatus ; in other words, the furnace coil should be one-tenth of the whole of the pipe used. The air vessel should be not less than one-tenth of the whole also, so that the furnace coil and air vessel constitute two-tenths of the whole. The air vessel, as already mentioned, may be of pipe the same size as the rest, or, to economise space, a larger sized tube, but of very strong quality, may be used. The pressure and temperature table (Lardner) is as follows : Pressure in Ibs. per sq. in. Atmospheres. Temperature. Degrees Fahrenheit. Pressure in Ibs. per sq. in. Atmospheres. Temperature. Degrees Fahrenheit. 15 I 2I2'OO 240 16 398-48 30 2 250-52 255 17 403-88 45 3 275-I8 270 18 408-92 60 4 293-72 285 19 4I3-78 75 5 307-58 300 20 418-46 90 6 320-36 315 21 422-96 105 7 33i '70 330 22 427-28 120 8 34i'78 345 \ 23 431-42 '35 9 350-78 360 24 435-56 150 10 358-88 375 25 439-34 I6 5 ii 366-80 45o 30 457-16 180 12 374-00 525 35 472-64 195 13 380-66 600 40 486-50 210 14 386-96 675 45 499-10 225 15 392-90 750 5 510*62 3io Warming Buildings by Hot Water. The modified form of the high pressure apparatus, a form that will, no doubt, supersede the genuine and original system for residential and most building works, is practically identical with the other, except for the introduction of a regulating valve at a point that will be presently indicated, and, in the majority of cases, the absence of the expansion pipe. The construction of the boiler coil and furnace is the same ; the arrangement of services may be the same also, but the regu- lating valve permits of a free use of stop-cocks wherever desired without being liable to cause damage. This valve practically consists of a safety valve and inlet valve combined, the former permitting the apparatus to be relieved when the pressure is excessive (the valve can be set to open at any pressure desired*), by allowing some of the water to escape ; and the inlet valve permitting water to re- enter the apparatus when it has cooled and is upon the point of creating a vacuum by the contraction of the water as it loses heat, and, consequently, bulk. Fig. 191 will give an idea how Fig. 191. Fig. 192. this is effected. It must be clearly understood that this illus- tration does not represent a practical valve, but it will show * The preceding table shows that a valve weighted to 135 Ibs. to the square inch would limit the temperature to 350. High Pressure Apparatus. 3 1 1 the working action that is embodied in the various valves used. The valves vary considerably, as each engineer of these works usually has his own pet notion, more or less complex. The great enemy to their efficiency is the perpetual expansion and contraction brought about in the valve itself by the almost constant outflow of hot and inflow of cold water, as every variation at the furnace causes one of these actions to take place at the valve. There are exceedingly few valves that are perfect in this respect. The valve is placed in a moderately small cistern at the highest point of the apparatus,* as Fig. 192, above the circu- lating pipes, and although the same water that is expelled is afterwards drawn into the apparatus again, it will be found necessary to replenish the cistern occasionally. Fig- 193 The pipes have to be erected in a manner that conforms with the Building Act (see end of book). It is impossible in this book to give more than a briet explanation of this system, as its full treatment would fill a * Not necessarily the highest point, as will be understood. 312 Warming Buildings by Hot Water. volume by itself ; but for a variety of examples the reader is referred to Richardson's ' Treatise on Warming and Ventilating Buildings by the High Pressure System/ which, although not a modern work (1856), is worthy of every consideration.* Fig. 193 is an example of an apparatus heating a hall and two rooms leading from it. If desired, this system offers every facility for heating water equally as well as steam, and it could be used for heating ovens for cooking purposes. * To the best of the writer's knowledge there is not a modern work upon this subject in publication just now. ( 313 ) CHAPTER XVIII. WARMING BUILDINGS BY HEATED AIR. IT may be doubted whether this method of giving warmth will exist very much longer, so far as residence work is con- cerned, as, although it has certain features in its favour, as will be mentioned, there are few engineers who consider it preferable to heating directly from hot water pipes. With the latter we get more economical results and a warmth that is reasonably considered more agreeable than stove heat. The system of heating under discussion is, however, not confined to heating the air by stoves alone. Hood goes to great lengths to show what very ill results may accrue from furnishing offices or living apartments with air that has been heated by passing over and having contact with the heated iron of cockle stoves. Some of his remarks are very much to the point. He points out that " the effects produced on the hygrometric condition of the air by this mode of artificial heat is of much importance. Dr. Ure found that in a Government office in London the clerks were all affected by serious sensations of the same character, owing to the warmed air passing over stoves which, by carelessness, were sometimes allowed to get red hot, the air heated to 1 10 and rendered intensely dry, .... animal and vegetable matters in the air were decomposed, and a disagreeable smell was thus imparted. The apparatus was found so pernicious that it was removed. The author examined a school also thus heated, and the results were so serious to the children that they occasionally dropped off their seats in fainting fits, and they constantly required the relief of going for a few minutes into the fresh air. These pernicious effects are, however, much modified by tempering the air by the evaporation of water." 314 Warming Buildings by Hot Water. The cockle stove was merely a furnace with an iron casing, placed within another larger case, the space between the two acting as an air chamber, an inlet leading into it, and a warm air conduit from it. An improvement upon this, so far as maximum results were concerned, was to enclose a stove in a brick chamber and make use of some portion of the flue pipe, as Fig. 194. In both these methods, however, there existed Fig. 194. the probability of overheating, and a very deleterious effect is produced by passing the air over intensely heated surfaces, probably red hot, in instances like these. We have no information at present to show that air, either in its composition or nature, is affected by contact with heated surfaces of stoves, however high their temperature may be ; Warming Buildings by Heated Air. 315 from all we know at present the ill effects alluded to are entirely due to insufficient moisture, and vitiation owing to particles of organic matter* being decomposed when brought against the hot plates. The question of moisture has an important bearing in connection with this subject, as it has to be pointed out that although the vitiation and consequent ill odour might possibly be put up with, we cannot long afford to breathe such very dry air without noticeable injury to health, and that of a somewhat serious nature. The peculiar feature connected with the moistness of the atmosphere, and what causes all the trouble, is, that as we increase the temperature of the air we have to increase its moistness in a regular and bountiful proportion. Air at out- door temperature, having a certain and correct percentage of moisture, when warmed becomes dry and unpleasant, not because it has lost any of its moisture but because it has had none added to it proportionately with its increase of tempera- ture. Table II. in the Appendix shows the proportions at different temperatures, and unless this degree of moistness is attainable, the warmed air will be, to say the least, unnatural. This trouble can be remedied somewhat easily by intro- ducing water by some means, so that the air as it absorbs heat can at the same time, or immediately afterwards, pick up moisture ; this is commonly and generally satisfactorily accomplished by placing troughs or pans on and around the stove in the air chamber or some accessible place, or when the warm air conduit is large enough, arrangement is sometimes made to have strips of cloth hanging in it, a species of cur- tain (not sufficient to arrest or retard the passage of air) this being kept moist from a trough above. If we can efficiently moisten the air, the chief source of trouble with stove heated air is overcome, but there is always the likelihood of a dis- * A large proportion of the particles of matter floating in the air, and which we call " dust," is organic matter, wool, fibre, volatile substances, &c., readily affected by heat and producing more or less unpleasant odours and effects. 3 1 6 Warming Buildings by Hot Water. agreeable odour, and the uncertainty whether the air is at the correct heat for the amount of water, as we can have air excessively saturated, as well as insufficiently so. The different ill effects which have been alluded to are modified in a great measure by using " Gill " stoves, this form of stove having a number of plates, or gills projecting from it, similar in principle to the gilled pipe shown on p. 264 ; the idea is supposed to have originated with a Mr. Sylvester about 1830, and there is a deal of sense in it. The peculiarity of a Gill stove, is that it cannot very well be overheated to an objectionable or dangerous extent, and although we do not get air at so high a temperature, we get equal ultimate results of a more agreeable nature, as we get air at a lower heat, but in a proportionately greater quantity to produce the same total effect. The gills on this description of stove answer the useful purpose of increasing the radiating and air-heating surface ; but with this largely increased surface we do not get so high a temperature as we should do with the mere shell of the stove if the gills were absent. If it could be correctly so expressed we might say that we get the same measure of heat, but with a gill stove less temperature and greater volume, with a cockle higher temperature in less volume. The latter is more objectionable for heating air, from a health point of view, than the former. The reason the gills act as radiating surface, is due to the high conductivity of iron (of which they are composed), the heat being transferred from the interior to the outer limits of the gills with the greatest rapidity desirable. Fig. 200 shows a Gill stove fixed in a brick chamber, this chamber having a fresh air inlet and a warm air outlet, the latter being continued to wherever required. As shown, the stove should be fixed in such a way that all stoking, &c., can be done without in any way interfering with the air chamber. In many instances this chamber is made without any provi- sion for inspecting its interior ; this is a bad practice, as a door can readily be placed for inspection, and cleaning. The Warming Buildings by Heated Air. 3 1 7 air chamber should only exceed the size of the stove by from 3 to 6 inches, and the fresh air inlet should be situated and arranged so that the air introduced must have contact with the stove, and not escape into the warm air conduit without being warmed. Fig. 195- The position of the inlet and outlet for the air requires consideration for another reason, viz. that if the passage of warmed air from the air chamber to the outlets is induced by its less specific gravity only,* and is not impelled by mechani- cal means, it is very necessary that the inlet for cold air be at a low point, and the outlet for warmed air at a high one, otherwise we shall most probably get a reverse action, as we should with a hot-water circulating apparatus, for the acting principle is practically alike in both. There is no doubt that a great objection to this system exists in the general difficulty of application and the con- sequent cost. In a new building provision can readily, and to an extent, inexpensively, be made by building brick conduits for the warmed air to all the points desired. If provision is made in this way in course of construction a deal of trouble is obviated and the system comes within toleration, as its con- * With ordinary ventilation, see p. 326. 3 1 8 Warming Buildings by Hot Water. struction at this time would very likely be less than a hot water apparatus, and, provided the air can be moistened, very little trouble would be experienced, except that the vitiation of the air would continue, though not to nearly such a pro- nounced extent as with a cockle stove. In a building already constructed much work would probably become necessary, as it is next to useless having the warm air conduits of small size, and, as they have usually to be of iron, they cannot be carried here and there like small hot- water pipes. Both iron and earthenware are used for this purpose, wrought iron most usually on account of its less weight and the less number and strength of supports needed. The sizes of these conduits vary to some extent with the magnitude of the works, but even for small purposes they should not be less than 6 inch diameter, if round, or an equal area if square or any other shape, and for moderate and fair sized works 7 inch, 8 inch, and 9 inch will be required.* It would be hard to err on the side of having too large a pipe, unless these pipes were left uncovered and so could lose heat ; this, however, should not be done, as will be referred to presently. With a brick-built air chamber it would be best to continue the warm air conduit in brickwork also, as far as possible, and then let the pipes branch from it ; in that case the brick portion of the conduit might be of larger size. Brickwork, wherever it can be used, is always the best on account of its heat-saving properties, which should be con- sidered an important feature with the warmed air passages, particularly if the free passage of air in the direction required is due to its rarefaction, and not to any mechanical or blowing arrangement. Next to brickwork, earthenware pipes may be considered best, as these lose very little heat compared to iron, but they are cumbersome and introduce a deal of work * Nine inch is far from being the maximum size ; these sizes only apply to residence works, as for large public building the conduit for some distance is sometimes a passage way in brickwork large enough to be walked through. Warming Buildings by Heated Air. 319 if suspended, though not so much so if placed on stands on floors not a common practice. With exposed iron pipes we not only lose much heat, representing a loss of fuel and also a slower passage of air due to the decreased temperature, but we introduce a source of danger if the pipe be too near any inflammable material. The latter point, however, is regulated by the Building Act (see end of book) ; but at all times iron pipe conduits should be covered, otherwise the loss may cause a failure. The very best material for covering these conduits is silicate cotton, a sub- stance that cannot be too highly commended for this purpose. It can now be obtained in almost any form, either loose, or as a felting from (i to 6 inches thick), or woven in thick bands, &c., and its price is as low as could be desired.* From recent experiments made this material is found to be nearly as effica- cious as a poor conductor of heat, as animal wool and down, neither of which could be used (apart from their cost) by reason of their inflammability. A firm who make a specialty of stoves for hot-air works (or for ordinary direct heating) show one arranged as Fig. I 9 6.t There are several firms who supply ordinary fire-grates with an air chamber at the back arranged for connection with the outer air if convenient, or otherwise allowing for the air in the room to be warmed, in either case the warmed air entering the room from the top of the stove above the fire opening. These are very successful as a rule, and some makers take great trouble to make them as perfect as possible by introducing gilled plates in the air chamber for the purpose already explained, and also other improvements. It should be noticed that the material which parts the fire from the air chamber should not be fire-bricks only, as this * Frederick Jones and Co., of Kentish Town, London, who make a specialty of this material, quote I2s. 6d. per cwt., or io/. los. per ton, with a covering capacity of 1800 square feet I inch thick to the ton. t From the catalogue of Musgrave and Co., New Bond Street, London, W. 320 Warming Buildings by Hot Water. material is only too liable to become fractured, thus allowing smoke to pass in, which it very readily would do. The most novel arrangement of this kind, as applied to a grate, is that made by E. H. Shorland, of Manchester, em- bodying the principle suggested by Sir Douglas Galton in Fig. 196. FRESH Air which the air enters at a low point as usual, but when warmed is discharged near the ceiling of the apartment. By an arrangement provided with this make of grate the warmed air can be discharged at two different points, to two different Warming Buildings by Heated Air. 321 Fig. 197. INLET FOR WARM AIR rooms if desired. Fig. 197* shows in section how this result is effected, but it is rather necessary that this be done in the * From the Catalogue of E. H. Shorland, St. Gabriel Works, Man- chester. 322 Warming Buildings by Hot Water. construction of the building ; it could of course be done at any time after, but the expense would be great. This grate and the principle it embodies are greatly liked, and would be much more in demand if the cost could be lessened. Occasionally use is made of what is practically waste heat from the backs of fire grates and also kitchen ranges by con- structing sheet-iron boxes to fit as closely as possible to the back of the grate and from these boxes, which act as air chambers, carrying warmed air conduits, the necessary air inlet being provided as a matter of course. The evil of these box chambers is that they are not readily made perfectly air tight, and thus odours of smoke or fire, and perhaps of cook- ing, will pass through with the warmed air, and ruin the whole undertaking. This is more likely to happen as it is somewhat difficult to properly test the apparatus until the grate or range is fixed and in actual work, when it is almost too late to think of remedying a fault.* One of the most powerful stoves for hot air work is as Fig. ipS.f This kind of stove is capable of dealing with the largest works, theatres, churches, trade exchanges, also Turkish baths, &c. They are made in various sizes, each size requiring a proportionate air chamber and conduits. Fig. I99t shows the stove in position, a portion of the side brickwork being omitted to expose the stove. Before closing the subject of heating air from stoves, it might be mentioned that when a stove is fixed with a descend- ing flue (see Chimneys), carried beneath the floor upon which the stove rests, very agreeable and economical results * The writer once saw a brick air-chamber made behind a range, and this supplied a good volume of warmed air without any noticeable ill results. There was six inches of brickwork parting the range from the air chamber, and although this brickwork lessened the results, they were rendered more agreeable. The great fault in hot air works is in attempt- ing to get the utmost results with the least fuel, thus necessitating bringing the air in the nearest possible contact with the fire. f Convoluted stove. The illustrations are from the Catalogue of Constantine and Son, Stockton Street, Manchester. This firm issues a most useful pamphlet upon hot air works in connection with their stoves. Warming Buildings by Heated Air. 323 can be attained by utilising this horizontal part of the flue so that it will give heat to the room under the floor of which it passes. This cannot so well be done if the floor be wood, Fig. 198. as this would be a source of danger unless it was cut away and a concrete channel put in covered with stone, or an earthenware pipe flue could be laid in a concrete bed and Y 2 324 Warming Buildings by Hot Water. covered with a grating. If the floor be stone with earth beneath (a ground floor), advantage can easily be taken of the heat that a horizontal under floor flue is capable of giving off. Fig. 199. HORIZONTAL SECTION, CROSS SECTION. Considering the great and valuable percentage of heat that passes up every chimney (much more than is needed to keep up the draught), it would be profitable in house construc- tion to make a chimney from one room pass beneath the floor of the one above it ; the heat this one chimney would give off, Warming Buildings by Heated Air. 325 if properly constructed for the purpose would keep a room, particularly a bedroom, at an agreeable warmth without assistance, unless the weather was severe. This could not always be arranged perhaps, but it might be in very many instances with the . best of results. Provision must be made for sweeping at two different points. Stove-heated air can be had at almost any temperature, and is of valuable use for many purposes that could not be fulfilled by air heated by hot-water pipes. For general residence work the writer is inclined to recom- mend heating the air by low pressure hot-water pipes in pre- ference to any form of stove, as the temperature cannot readily become disagreeably high, neither is it dried to the extent it is by stove heat, nor vitiated, and provided no one raises any objection, the workman need have no hesitation in carrying his warmed air conduits in close contact with wood work if desired, or if he wished to prevent loss of heat the air pipe could be encased with wood, and surrounded with saw- dust or felt, without fear of ignition. In carrying out this work an air chamber has to be con- structed of sufficient size to take the quantity of pipes to be used, this air chamber having inlet and outlet air conduits as already explained. The boiler for heating the pipes can be placed outside the chamber or recessed within the wall ; and the supply cistern with which the boiler and pipes are supplied with water is placed outside also at a convenient point for inspection, and the pipes must have the necessary air vents. All this is fully treated of in the earlier chapters of this book. The hot-water pipes should be stacked moderately close and arranged so that no straight passages exist between them for the air to pass through without being warmed. It is always necessary that the air chamber have no excess of space anywhere within it that air may pass tnrough without being affected in the way desired, and the inlet and outlet openings should be arranged with this idea. If they must necessarily come at awkward points, the flow of air should be diverted with feathers or plates, that it may traverse all 326 Warming Buildings by Hot Water. possible space in the chamber before its exit into the warm air conduit. The quantity of pipe required should be calcu- lated at double that given on p. 279, no certainty of efficiency can be depended upon with a less quantity, and the air passages must be large enough to carry a proper volume of air for the size of the apartment operated upon, otherwise the effect of the heating media will be minimised. For the efficient working of any hot air apparatus it is absolutely necessary that there be a provision made for outlet ventilation in the rooms or places where the warm air conduits terminate, otherwise we must not expect the warmed current to flow in, not even if it were propelled by a blower. It is unnecessary to go into any great explanation to prove this, as it is such common knowledge. A hot air apparatus in which the flow of air is brought about by the lessened gravity of the heated air bears an exact resemblance to an ordinary chimney ; and this latter conduit of warmed air and gases would act very imperfectly indeed if its contents could not freely escape at the top. If we terminated a chimney in a closed room or chamber, it would not matter how high or how perfectly constructed the chimney was, it would not act, that is, it would cease to convey the hot gases and smoke from the fire at its other extremity. The ventilation referred to is, however, not of such importance if the room be small and has a fireplace (chimney opening) in it, as we have an exhaust ventilator of a fairly powerful character in this, quite sufficient by itself for a moderate or small-sized apartment, but for large rooms, even if a fireplace exists, further ventilation should be provided, and in public halls and places the subject requires full con- sideration. As a rule, the ventilating outlet should be of an area about equal to the warm air inlets, not necessarily exactly, but as nearly as possible. The warm air inlets are usually situated behind the skirting of one side of the room, with gratings in front that can be opened or closed. If in a hall or corridor they may be beneath the floor, with brass or iron gratings above. A warm air Warming Buildings by Heated Air. 327 apparatus exhibits its advantages when discharging the warm air through gratings in the entrance hall of a large residence, as the air distributes itself in all directions, and as the supply is never-ending it is soon felt all up in the house and in the rooms, if the doors be left open. The entrance hall and staircase in a residence has been likened to an artery, and the comparison is good, as by distributing warm air freely in the hall the whole of the house will be benefited. As an instance of this, a good-sized house, having a rather large square Fig. 200. entrance hall was heated by a gill stove, only measuring two feet long (18 gills), placed in an air chamber, the warm air conduit being branched, as Fig. 200, with four gratings in different parts of the hall, the stove being a few feet below. This little apparatus warmed the hall, staircase, landings and corridors all up the house thoroughly, and contributed to no mean extent towards heating the rooms. 328 Warming Buildings by Hot Water. The cold air inlet to the air chamber need only be a hole, situated at a low point, but it should be seen that the air be from a sweet, i. e. fresh source ; if it is not, a pipe must be used to lead it up to the chamber. Many an apparatus has the air inlet opening in the stoke-hole, which, it is needless to say, is bad in principle. Arrangement is made occasionally for filtering the air as it enters ; cotton wool will do this, but it will stop the flow of air to some extent, and it will only arrest suspended matter, dust, and also the dirt with which a fog is sometimes laden. It is a good plan to adopt if considered desirable, as it is such solid matters that vitiate the air by coming in contact with the heated surfaces. ( 329 ) CHAPTER XIX. HOT WATER WORKS FOR BATHS, LAVATORIES, AND OTHER DOMESTIC AND GENERAL PURPOSES. A Series of Papers contributed by the Author to ' The Builder] and reprinted by permission. Circulation Boilers and incrustation Pipes, taps, and other fittings and appliances Covering pipes and reservoirs for the conservation of heat Conversion of a tank apparatus to the cylinder system Twin boilers and services Improved and other systems ; peculiarities noticed from experiments, and their results in practice Coils and coil services Faults and sources of danger Accidents and sources of danger Safety valves, &c. Low-pressure boilers, also fitting high-pressure boilers for temporary low-pressure work. A SUPPLY of hot water throughout a house is no longer con- sidered a luxury, but merely a common comfort, a necessary, and expected as a matter of course by the majority of tenants of property at as low a rental as 3O/. This subject, however, is, of the various trades called into request in house construction, perhaps one of the most difficult for professional men to obtain reliable information upon, owing to several causes ; the chief difficulty being that, as little information has been written or published on this work, knowledge can only be gained by actual experience. The number of failures that occur in this work is greatly in excess of those in most other trades, by reason of its success or non-success (except in simple every-day jobs) being greatly dependent upon an acquaintance with natural laws, and it is unfortunately obvious that the majority of our mechanics have little knowledge in this direction. 330 Warming Buildings by Hot Water. CIRCULATION. It is but a comparatively short time ago that an attempt to utilise hot water for heating purposes was made by connecting a pipe or series of single pipes with a boiler, the hot water (from the boiler) being allowed to run into the pipes, and this was found to be a success in a limited way, as the water did not appear to grow cold as might have been anticipated. The good results obtained were due to the fact that water will circulate in a single pipe, as any one sufficiently interested can quickly determine by experiment, and it will be found that if the pipe be carried in a vertical direction from the boiler there will (supposing heat to be applied) at once set in two distinct movements in the water, that in the centre ascending, and that nearest the surface descending ; or, if the pipe be carried in a slanting direction, the water nearest the top of the pipe will be found travelling from the boiler, and that at the bottom of the pipe towards the boiler. Possibly, when this attempt was first made it was expected that the heat generated in the boiler would be transferred to and along the water in the pipes by conduction, as would be rightly anticipated if heat were applied to one end of a rod of metal ; but as water is an extremely poor conductor of heat the result obtained in the transference of heat from the boiler throughout the length of pipe or pipes was soon ascer- tained to be from another cause, viz. convection, and it is with this property that water possesses that we have to deal, as without it a hot water circulating apparatus could not exist. The single pipe system was but short-lived, it being almost immediately ascertained that by providing two pipes and connecting them at the extremity, a more rapid and efficient circulation resulted, as it did not necessitate a flow of water in two directions within one pipe, and it is from this early arrangement of two pipes that all our systems of hot water circulation for heating and for domestic supply purposes have been developed. Circulation. Fig. 201. Water is composed of two gases which exist in chemical combination (H 2 O) forming molecules, and water, therefore, consists of a vast number of extremely minute particles, we might say like a heap of sand, but differing from this substance by the fact that the particles have the property of gliding over, under, or around one another (when agitated) practically without the least friction or resistance. Of course water differs from sand also in the fact that we could not have a heap of it, as water, unless confined, instantly distributes itself in all directions ; but the comparison is used to make it understood that water is composed of particles or grains (molecules). When a boiler or vessel is filled with cold water and left undisturbed the particles may be considered to be quite stationary, but immediately heat is applied below, the particles nearest the heated surface become warm, and they, like all other substances, are expanded by the heat, and as an expanded particle does not gain in weight as well as size it naturally is made lighter, bulk for bulk, than its fellows. Immediately, therefore, the particles nearest the heated sur- face become expanded they are caused to rise by the superior weight of the cold particles sur- rounding them, and the cold particles that then come in con- tact with the heated surface become warmed and expanded, and rise also, and so the action continues ; so long as heat is applied a continuous stream of heated particles rising, and a continuous stream of colder particles replacing them, and this is the process of convection. When the fire is applied to a boiler having a system of circulating pipes in connection with it, the heated particles rise to the top of the boiler, and finding an opening (pipe) 332 Warming Buildings by Hot Water. Fig. 202. COLD WATER CISTERN / there, continue rising up within it until they reach the highest point in the circulating apparatus, above which they cannot rise, and it can be readily understood that for every particle that travels up the flow pipe there must be a corresponding particle come down the return pipe to replace it. The action is the same as in the boiler alone ; a stream of heated and lightened particles rising until it is impossible for them to rise further, and a corresponding stream of colder particles travel- ling downwards to replace the heated ones, until they come within the heated area, when they are ex- panded, and at once re- verse their direction, and follow their predecessors. This circulation proceeds at a much higher speed than is commonly ima- gined ; when first started the heated particles travel about 12 in. per second, and afterwards, when the water is well heated, at about double this rate. The earliest description of pipe apparatus to supply hot water for draw-off pur- poses above the level of the boiler was merely a large boiler in the kitchen range, a pipe Circulation. 333 from the house cistern down to the boiler, and a pipe from the boiler to above the level of the house cistern (Fig. 202) : from this latter pipe the draw-off services were taken, and it will be readily understood that (water always finding its own level) a draw-off service could be connected and hot water obtained at any point below the house cistern. There were several insurmountable objections to this arrangement ; in the first place, a very large boiler was neces- sary, as no tank could be used, and the largest boiler in an old open range could hardly exceed sixteen gallons capacity, a very insufficient quantity for a store of hot water, as can be judged by the fact that a tank of such small capacity is now never used for even the smallest of hot water supply purposes. A second objection was that with a long single service pipe a great quantity of cold water had to be drawn off before hot was obtained, and there were several other objections ; but, no doubt, amongst the chief reasons for the discontinuance of this system was the fact that these large boilers were very costly, and as, with the best provision, they were very difficult to clean out, they frequently became fractured, creating no small annoyance and expense, and as soon as it was understood that a smaller boiler and smaller fire (with the addition of a tank) would provide a much more reliable and abundant supply of hot water, the old system naturally fell into disuse. BOILERS AND INCRUSTATION. Information upon boilers for hot water supply must, to make the subject clearly understood, necessarily be preceded by an inquiry into the cause and effects of the incrusted deposit, or " fur," which accumulates so rapidly in these boilers (when what is known as " hard " water is used), as their shape, con- struction, and general character is, to a great extent, governed by a consideration of this subject. The origin of the term " hard," as applied to water holding lime in solution, cannot well be traced ; but most probably it 334 Warming Buildings by Hot Water. was first used in contradistinction to the sensation of softness that is experienced with distilled or rain-water, or nearly any water which has but a small percentage of lime in solution. Our supply of hard water (so far as concerns this paper) may be considered to be limited to that which proceeds either through or from chalk strata, and as this water is usually of a crystal-like clearness, it naturally becomes difficult for the uninformed to make it accountable for the hard stony deposit (limestone, in fact) that incrusts the inner surfaces of these and of steam boilers. To explain the course first, the generally accepted theory is as follows : Water which descends to the earth in the form of rain comes is contact with, and readily takes up, carbonic acid, either from the air in which this gas is present to a consider- able extent, in the vicinity of populated places, or from decaying vegetable matter in the open country. This water, charged with carbonic acid gas, percolates through the earth, and immediately it comes in contact with chalk (carbonate of lime, calcic carbonate) the acid enters into combination with the chalk, producing bicarbonate of lime (calcic bicarbonate), which is highly soluble in water ; in fact, might almost be considered as a fluid itself. It is very necessary to notice this peculiar difference between carbonate and bicarbonate of lime, as it is wholly accountable for the trouble now under discus- sion. The former, which we speak of as chalk, consists of lime having a certain quantity of carbonic acid gas held in combination with it, and this substance is, as just explained, but sparingly soluble in water. Bicarbonate of lime consists of precisely the same materials, but the quantity of acid gas is exactly doubled, and this renders it highly solu ble in water. It will now be understood that the supply of this hard water is confined to districts where chalk abounds in the soil, and the degree of hardness naturally varies with the nature of the ground. In the South of England, including London and many counties south of London, nearly all the water is more Boilers and Incrustation. 335 or less hard, but in the north of England the water is of quite a different character, and hard water is, to a great extent, unknown, so much so that vast quantities of boilers (for kitchen ranges) are made without manlids or any means of removing any incrusted deposit. When a new boiler is first charged with this hard water and sufficient heat is applied, the result is to drive off the pro- portion of acid gas, which goes to make the carbonate into bicarbonate of lime, and the latter is transformed into the former again, and, being insoluble, it is precipitated, forming a thin film or coating upon the inner surface of the boiler ; this precipitation does not wholly take place immediately heat is applied, but proceeds slowly until boiling takes place and steam is formed, when the chief precipitation is effected. It is almost needless to add that the greatest quantity of deposit is found at that part of the boiler where the greatest heat is felt, but this may be more fully entered into when describing boilers. The deposit which is effected when using a boiler but once is a very minute quantity, but when we remember that the same water does not stay in the boiler (when the apparatus is at work) more than a few moments, and fresh water is being continually brought to the heated surface by reason of the circulation, we can then understand why the deposit seems to accumulate so rapidly, especially as the heated and (wholly or partially) softened water is being continually drawn off for domestic uses, and entirely fresh takes its place. This would be a fitting opportunity to explain that with boilers used for heating purposes only, the deposit occasions no trouble whatever, as the same water is used over and over again, and a given quantity of hard water will only yield a certain amount of lime deposit, however long it may be boiled ; of course, in a heating apparatus there is a certain loss of water by evaporation from the filling cistern, but this does not usually amount to more than about a quart per week, as the water is not allowed to attain boiling temperature. But in a domestic supply apparatus the quantity of water used 336 Warming Buildings by Hot Water. does not usually come under 400 gallons per week, and in many residences, perhaps, a thousand or more gallons in this time. The average hardness of London water is about 16 per cent, and a range boiler in regular daily use will have a J-inch deposit of "fur" within it after six months' use. No rule, however, can be laid down to ascertain at what rate the deposit accumulates, as, although it is easy to find out the degree of hardness of the water, the result is chiefly governed by the efficiency or non-efficiency of the boiler in its heating capabilities, whether the water is nearly always boiling, or whether it seldom reaches this temperature ; and again greatly by the quantity of water used, as every drop of fresh water introduced (to replace that drawn from the taps) has its portion of lime to deposit. In the counties south of London, particularly Sussex, the water is very strongly impregnated with lime, so much so that an ordinary sized boiler will commonly become sufficiently incrusted in from twelve to eighteen months to bring about its fracture. See Fig. 203, which is the section of a boiler badly furred. The ill effects of this furring consist firstly (and most especially) in its causing the boilers to be- come fractured before about an eighth of their natural life of service has expired ; secondly, a comparatively thin coating of deposit will materially lessen the rapidity with which the water heats, as it is such a poor conductor of heat ; and, thirdly, the deposit also locates itself in the pipes, at first retarding the circulation, and eventually causing a stoppage, and becoming an element of danger unless attended to. Boilers and Incrustation. 337 The deposit partakes of a variable degree of hardness or solidity, that which is the most dense causing the boiler to fail the earliest, and that which is most porous permitting the boiler to render the longest service. With the different London waters the deposit is of a fairly similar character, being very dense and, in many instances, closely resembling ordinary limestone ; and when this has become of about 2 inches in thickness (about two years use, usually) it is sufficient to prevent the water having any contact with the boiler-plate, with the result that the iron is destroyed by the action of the fire, the same as if the boiler were empty. In instances where the deposit is of a more porous or of a scaly character, it naturally re- quires a thicker deposit to bring about this result. The failure of the boiler always shows itself in the form of a small crack or fissure (Fig. 204), not a hole in the common sense of the word ; and this fissure is rarely larger than I inch in length by -^ inch in breadth, for the simple reason that so soon as the fracture takes place water proceeds from it in a greater or less quantity, and this prevents the fire being ignited, and without the fire, of course, no further damage can be done. There are two remedies for this trouble, one being to soften the water by removing (i. e. precipitating by chemical action) the lime in solution ; or, secondly, by having the " fur " removed at regular periods. The first hardly comes within the province of these papers, yet it might be mentioned that whatever process is adopted, the softening must be done in a separate cistern, as it would not do to have the precipitated lime carried into the service pipes which run from the house cistern ; and each supply of Z 338 Warming Buildings by Hot Water. fresh water must be operated upon. It must be borne in mind that softened water is not agreeable for every purpose, although it may be beneficial to boilers. The best remedy and the least expensive is to employ a workman to clean out the encrusted deposit at regular periods. This remedy is, perhaps, sometimes a source of inconvenience, owing to the fact that when this cleaning takes place the kitchen range cannot be used, and, under the most favourable circumstances, this work cannot be done in less than two hours ; with some ranges it takes more than a day. The time occupied is to a great extent governed by the amount of trouble experienced in removing the manlid of the boiler. Special means should be provided to make the lid easy of access and removal ; but more than three-fourths of the kitchen ranges in the market have no provision of the kind, and the range has to be dismantled and partly unset for the purpose of exposing the boiler manlid. In "cleaning a boiler," as it is called, the workman has first to get at the lid of the boiler, then to unfasten and remove it ; the " fur " is then loosened with a chisel or other suitable instrument workmen often have some fancy tool of their own for this work, after which it is removed by the hands and the lid repacked and fastened, and whatever parts of the range have been removed, replaced. Of course, the quantity of "fur" that has to be removed will govern the time the work occupies to some extent, but the most troublesome cases seldom take more than two hours after the lid of the boiler is removed. In London and its suburbs it is found advisable to clean the boilers every six months regularly, in some instances they may be permitted to go twelve months ; but it must be borne in mind that the oftener the boiler is cleaned the longer will be its term of life or service, and the less quantity of fuel will be needed to heat the water. A good plan is to have the boiler opened after six months of ordinary use, and a glance will determine whether this period is a proper one for having it cleaned ; but in Sussex or in other localities where the Boilers ana Incrustation. 339 water is very hard, the period for first inspection should be reduced to three months ; but a person about to build or purchase a house in a district of which he has no experience, can always make profitable inquiry from those already resi- dent there. It should be borne in mind that filtration will not remove lime in solution. The subject of incrustation is being dealt with somewhat fully, as it is a question worthy of every consideration in the south of England. It is no exaggeration whatever to say that seven-eighths, or even more, of the fractured wrought-iron boilers in London (and the number is very large), owe their failure to this cause alone. The trouble is greatly aggravated by the fact that very few of the average householders have any knowledge of the subject. The water gives no evidence of having lime in its composition, and the Water Companies, who are clearly responsible, and who ought to issue informa- tion upon the question, are silent ; and the consumer and user of the water gains experience by paying for it when the boiler cracks. There are probably from eight to ten thousand pounds sterling spent annually in renewing boilers that have failed from this cause, in the London district alone, and the work is necessarily expensive, as in each and every instance a quite new boiler has to be fitted, it being impracticable to patch or repair the injured plate ; and to have a new front, the boiler must be made shorter, which, of course, cannot be thought of. To still further show how prolific of trouble the " fur " is, it might be asked if any one has ever seen a boiler, in the London district, for hot-water supply that has failed from actual fair usage, that is to say, really worn out ; it may be taken for granted that very few, indeed, have ever seen such a thing. In concluding this subject, it must be explained that the majority of the north of England waters are more or less soft, and differ in character from those of the south in a remarkable degree ; the little deposit some of them precipitate is of a muddy nature, which can be flushed out, and it is therefore z 2 340 Warming Buildings by Hot Water. usual in these districts to provide a pipe expressly for this purpose at the bottom of the boiler. It can be readily under- stood that different districts must yield waters having a difference in character, but wherever the deposit does not incrust upon the inner surface of the boiler, very little trouble need be anticipated. After exposing the troubles consequent on the use of hard water, it is only fair to point out that it has one advantageous effect upon iron boilers and pipes of considerable importance, viz. that it has a preservative effect and, most important, the water is never discoloured with rust. In districts where soft water prevails the rust question has caused almost more annoyance than the " fur " in hard-water districts. Soft water has a very vigorous chemical action upon both lead and iron, with the result that with iron boilers and pipes the water becomes discoloured by rust to such an extent as to be not only an annoyance but a source of serious trouble, and with lead pipes the result is likely to lead to an epidemic of lead poisoning, as it has done many times, and it is on this account that in the soft-water districts copper boilers, cylin- ders, &c., have to be resorted to, but, of course, at considerable expense. But one beneficial effect of hard water is that lime is a violent opponent to rust,* and the thinnest film of carbo- nate of lime entirely overcomes this trouble, and it is on this * A most interesting experiment was made at the Royal Institution some time ago with a view to determine whether the presence of carbonic acid in air or water was responsible for the rapid oxidation or rusting that is experienced when iron is exposed to either of these elements in the ordinary way. Two test-tubes were taken and filled with ordinary water, and into each was placed a common sewing-needle ; one tube was sealed up in this state, and the other tube was also sealed after having a small piece of quick-lime (oxide of calcium) placed in it. These tubes were placed away for twelve months, and at the expiration of this time examina- tion showed that the needle in the tube of ordinary water was a mass of rust, whereas the needle in the tube of water with lime in it was perfectly free from rust, bright, and equal to new, owing to the lime having taken up the carbonic acid (present in the water) to form carbonate of calcium. This clearly illustrates that hard water has one redeeming feature in connection with hot- water boilers and apparatus. Boilers. 341 account that copper, so largely used in the north, is quite the exception in the south for hot water purposes. This peculiarity that lime possesses in opposing the forma- tion of rust can be taken advantage of by coating any form of boiler or iron vessel with lime-white when the vessels in ques- tion are inclined to give trouble by discolouring the water with rust, a very common occurrence with the ordinary open- top side boilers of kitchen ranges the first month or two they are used ; and more than one cure has been effected to^ an iron-pipe apparatus, when rusting from the action of soft water, by running a tolerably strong solution of lime- white through it and so coating the interior of all the pipes, &c., with lime. This coating must be allowed to get thoroughly dry before charging the apparatus with water. BOILERS. Boilers for hot water supply, usually called bath or high- pressure boilers, may be divided into two distinct classes, viz. those that are fixed in and heated by the fire of a kitchen- range, and those that are independent. Neither of these boilers can be made in any great variety of shapes, like those for heating purposes, on account of the "fur" deposit question and all its drawbacks having to be considered. The advantages and disadvantages of some of the shapes commonly seen in kitchen ranges can be profitably discussed, but it will be found that nearly every range-maker, especially if he be a specialist, has a boiler of his own parti- cular pattern, and for which he naturally claims superiority. There is one object sought by all makers alike, and that is to obtain the largest possible effective heating surface, and so provide a more abundant or rapid supply of hot water than others ; but this cannot be carried to any great extent, as, in the first place, the boiler is most usually made to the range, not the range to the boiler, and, secondly, the interior of the boiler must be tolerably roomy and clear for cleaning purposes, no tube flues can be permitted, for instance. 342 Warming Biiildings by Hot Water. If it were not for the trouble that fur occasions, the most efficient and economical form of boiler (?) known could be used, viz. a coil of pipe, which, if properly fitted, is all heating surface (ordinary range boilers have a little more than half their surface untouched by the fire) ; but with London water a coil fixed in this manner becomes furred up and split in eight or nine months, but even with this objection they are sometimes used, their cost not being great, provided their removal and renewal in an expeditious Fig. 205. manner can be arranged for. The most ordinary form of boiler is of a square shape, with a sloping front, and having an arched flue, as at Fig. 205. This is the shape that is almost invari- ably met with in the cheap makes of ranges, those used by the speculative builder, who considers lowness in cost of primary importance. It is not intended to convey that all boilers of this shape are necessarily attached to cheap ranges, but that is the shape invariably used in cheap goods of this sort. This is about the least powerful form of boiler made, as they rarely exceed 10 inches in length from front to back, and whatever the object is in making the front sloping it has a most prejudicial effect in decreasing the size of the fire at the bottom, with the result that the accumulation of ash more quickly chokes the boiler flue, and the less the body of fire the less bright it burns with less evolution of heat ; in fact, it must have been originally intended to have this front projec- tion at the top instead of at the bottom of the boiler, for this arrangement would certainly be more effective. Any one may perceive that a heating surface overhanging a fire gives better results than one projecting beneath. This pattern, which is very frequently (mis) called a saddle boiler, can have its efficiency or heating power in- creased by adding to its length from front to back, or by adding to its width, so as to give a greater area to the bottom heating surface, but both length and width, parti- Boilers. 343 Fig. 206. cularly the latter, are governed by the construction of the range fire-box. The most efficacious way to add to the power of the saddle boiler, spoken of in the last paper, by increasing its heating surface, is to extend it up the back of the range, making it what is known as a " boot " boiler, Fig. 206 ; nearly every make of range will permit of this, and the boiler then becomes one of the most powerful that can be used, and such a boiler fitted into a 6-foot range having a 14-inch fire will provide an abundant supply of hot water in a large residence with as many as twelve draw-off taps in regular use. Another form of boiler to be occasionally met with is similar to Fig. 207, having a tube flue through it, and when made " boot " shaped, the tube flue is sometimes continued up the leg portion. This shape has two obvious advantages over the so- called saddle boiler, the first being that the lower part of the flue is heating surface, which is not the case with a saddle, and the flue being raised up from the bottom of the fire prevents it being so quickly choked with ashes ; but it is commonly con- sidered that these advantages are outweighed by the disadvan- tage it has in being so difficult to clean out. Of course it is not an impossible task to clean out a boiler of this description, but it must be borne in mind that this work has to be entrusted to workmen who are no more perfect than those in other trades ; and although one man may give additional care to an awkward boiler in cleaning out the front angles the parts of the boiler needing most attention Fig. 207. 344 Warming Buildings by Hot Water. another man may be equally careless, with the most unfortu- nate results. There is an idea very prevalent that this cleaning process is a simple task that may be relegated to a labourer (fitter's assistant), but no greater mistake could be made ; it is work on which an experienced man should always be sent, as particular care must be exercised in removing fur from those parts which are subject to the greatest heat, especially the angles where the welds or joints in the plate exist ; and again, although a boiler is practically a box with an opening in the top, it is worth any one's while to insert his hand in a boiler when an opportunity occurs, to experience what a really awkward and difficult task it is to clean it out, remembering that the " fur " is usually hard like stone, and adhering to the boiler-plate. The trouble is greatly increased by many boilers being turned out with the innej edge of the manhole all rough and jagged with the filaments of iron that always appear on one edge of a hole that has been drilled, and there could scarcely be found a single hot-water fitter who has not scars upon his arms from this cause. There are numbers of people (not range-makers) who signify a preference for square boilers, that is, boilers having a flat bottom without any arched or tubular flue, but which have a flue put to them by Fig. 208. being placed on fire bricks, as Fig. 208 ; the argument in favour of these being, firstly, that with an arched-flue boiler a weld or joint has necessarily to be made around the front edge of the arch, whereas in a square boiler a joint need not be there, as the bottom front angle can be formed by simply bending the plate ; secondly, they contend that the narrow spaces on each side of the arched flue at the bottom of the boiler might quickly get solid with fur ; these arguments are considered strong ones by those who use them, but it can be as strongly maintained, firstly, that although a weld does exist in an Boilers. 345 arched boiler where mentioned, it is not proper for the weld to be weaker than the solid plate ; certainly boilers when " furred " occasionally open at the weld in question, but this is to an extent evidence of poor welding, as more than two- thirds of the fractures occur as at Fig. 204 (p. 337), in which the crack is shown at right angles to the weld, although close to it. Secondly, the narrow spaces referred to do not get furred so quickly as is commonly argued, and even if they did, a boiler has rarely, if ever, been known to crack there, and an argument in favour of these side water-spaces is that they add at least one-fourth to the available heating surface. All boiler-makers recommend that boilers to be of good quality should be made of plate not less than f-inch in thick- ness, and this is certainly a strength that can be used with confidence with the largest boilers for this purpose, including the independent kind ; but there is not the least doubt that boilers of -^-inch, or even J-inch plate, would do a deal of service, if not as much as the f-inch, for, as already explained, these boilers rarely fail from actual wear, and a f-inch plate will fail almost as quickly as the thinner ones, if the failure is brought about by the " fur." It is, however, not a desirable practice to use boilers of thin plate ; the f-inch is a serviceable and safe substance, and is (or should be) always used in the best quality of ranges. The quality of the plate is of the greatest importance, but this unfortunately cannot be judged from inspection, not even by the experienced ; good boilers are of the same appearance, and as rough as those of poor quality; and what might be ascertained from the colour or look of the metal is obviated by the makers coating the boilers with a preservative material, a kind of tar. A remedy for this can be suggested by recom- mending that such goods be only purchased from good and responsible firms. No reliable rule can be made as to what sized or shaped boiler must be used to meet certain requirements, for in no two residences will the demand for hot water be found to be 346 Warming Buildings by Hot Water. alike, and supposing the demand did not vary, the manner in which the fire is attended to in the kitchen varies greatly, in fact, the quantity of hot water depends to a very consider- able extent upon the amount of cooking done, as it is only when cooking operations are in full swing that the fire is assiduously attended to. It is, however, with every confi- dence that the " boot " shaped boilers can be recommended ; they are decidedly powerful, and although costing more than the saddle shape, they undoubtedly save their extra cost in the end, as they work so economically, and a given quantity of fuel will heat double the quantity of water with the former than the latter ; or, in other words, a certain quantity of water will be heated with half the fuel in half the time. Of course, this more expensive shape and size of boiler cannot well be specified for small i. e. 4 section). This consists of a circular or oval lid seen at the top of the illustration, and a "bridge" which is shown below it ; the pin through the centre with nut at the top securing the two ; this is the usual style, but occasionally an inside lid is met with, which merely consists of a nearly plain casting secured by two set- screws passed through the boiler-plate ; this is a very simple lid, and, if anything, preferable to the outside lid, which occu- pies space unnecessarily, and it will be readily seen that the pressure of water within the boiler tends to make the lid more secure rather than to cause it to leak. A form of manlid to be objected to, unless a very large hole has to be covered, is that which consists of a plain wrought plate secured by a number of set-screws. In the first place, the wrought plate is easily made uneven by the least improper or careless usage ; and, secondly, great care is needed in making the packing material equal in substance all round the hole, and the set-screws have to be most carefully screwed up to effect a sound joint ; and a still further objec- tion of some importance is that the strain exerted in tighten- ing up these screws causes the threads to strip after two or three times. Whatever form of manlid is used, its object is, of course, to stop up the manhole of the boiler in a thoroughly sound manner, as these boilers are often required to bear very high pressures (the inner surface of a manlid often has a pressure Boilers. 349 of 500 Ibs. upon it, i. e. 25 Ibs. to the square inch) ; and as boilers and manlids are not made with such perfectly true surfaces that they will fit together in a water-tight manner, a jointing material has to be used between the surfaces. This jointing usually consists of hemp, with a mixture of red and white lead of the consistence of putty ; this material has been used almost from the time boilers were first thought of, yet for general purposes nothing has superseded it to any note- worthy extent. The hemp is sometimes used in strands and sometimes chopped up and incorporated with the red and white lead mixture, but better than the hemp in hanks is a material called " gaskin," which is a soft, thick, cord-like substance. The particular advantage gained by using a cord is that dependence can be placed in making an even joint ; with loose hemp a perfectly even joint is almost impossible. A material now largely used by the majority of workmen and which answers very well, for the joints rarely fail, is ordi- nary cardboard of a moderate thickness. This the workmen obtain by breaking up a cardboard box or any other card- board article, and the only preparation needed is to first cut a collar of it to fit the manlid, then soak it well in plain water ; if only thin cardboard is obtainable two thicknesses is used ; a mixture of red and white lead has to be applied with this. There is now a species of sheet asbestos made expressly for this purpose, and it answers exceedingly well, but a little objection is that it has to be used in the form of collars. These must either be made to order or cut with considerable waste, but the material itself answers admirably. There is one other material deserving of mention, which is india-rubber, as it has several advantages peculiar to itself. This material is used in the form of collars or washers, several sizes of which can be found in stock at india-rubber ware- houses and frequently at ironmongers ; there is not such a difficulty in getting a size to fit with these as with asbestos, for the reason that any size can be stretched a little, if it is small or irregular, to the shape required, and, if necessity demands it, a circular collar can be made to fit around an 35 Warming Buildings by Hot Water. oval lid ; these collars should not fit loosely if it can be avoided. This material makes manlid packing a simple task. They do not need any preparation, no packing material, and they do not taint or render the water impure as the red and white lead joint often does, especially when a little too much of this material is used and squeezed into the boiler when the lid is tightened up. If care is used a rubber collar can frequently be used a second time, and to effect this the surface of the collar that comes in contact with the boiler- plate should be blackleaded to prevent its adhering (there is no great objection to its adhering to the lid). This material also has its disadvantage, arising however mainly from care- less or ignorant work on the part of the hot-water fitter. If the fitter screws his flow-pipe through the top of the boiler so that it projects to the least extent inside the boiler (as will be more fully explained later), or if he takes this pipe into the side of the boiler, it will to some extent cause a steam chamber to be formed close to the top surface of the boiler ; and as steam will not protect the rubber from the action of the fire heat, it will fuse or melt, and in perhaps not more than two or three hours after lighting the fire. Rubber collars are also very troublesome where there is a liability of water running short, as immediately they are subjected to a little higher temperature than boiling water they fuse. Notwithstanding this they are to be highly recommended, as their disadvantages are only apparent when bad work or dangerous circumstances exist. An inside manlid with a rubber collar is as near being perfect as we have arrived at yet. INDEPENDENT BOILERS. It is only quite recently that the importance of using independent boilers for hot-water supply has come to the front, the chief reason being that residences even of large size were considered complete in their hot-water arrangements if a supply was provided to a bath, lavatory, pantry, scullery, and housemaid's closet, and a good sized kitchen range will Independent Boilers. 351 furnish these with an abundant supply (or should do) ; but the desirability of having hot-water services conveniently situated for every practicable purpose is now receiving much attention by professional men, tradesmen, and clients, and unfortunately a good many failures are being experienced, as it naturally does not readily occur to one's mind that the kitchen-range boiler is going to fail in the useful work it has done for so many years. An instance occurred quite recently in which a 6-foot range with a boot boiler of the largest possible size that could be fitted to such a range, failed most signally, for investigation showed that the cylinder (hot-water reservoir) was a very full size, viz. 100 gallons, the pipes were a very full size, being ij inch throughout ; there were thirteen draw-off services, including three baths, and two taps in the stables, which have a great demand for hot water ; also a butler's sink, which when three-fourths full held about sixteen gallons ; and in addition the hall was heated by two radiators, and a linen- closet heated by a coil all from the kitchen-range boiler. The result made one believe that the boiler would not try to do the work, as the constant demand gave the boiler no opportunity to heat up a store of water. The introduction of an independent boiler of medium size entirely remedied this, as these heaters are so very powerful and so very rapid in results. It is intended to treat the question of radiators and coils somewhat fully when the time arrives, but it may be men- tioned here that these articles greatly oppose the efficient working of a hot-water supply apparatus, as of course they are made expressly to rob the hot water of its heat by dissi- pating or diffusing it, whereas with a supply apparatus it is most desirable to conserve every particle of heat within the pipes. Independent boilers have very many advantages, and wherever an opportunity to use them occurs they can be most strongly recommended. In the first place they have the im- portant advantage of requiring very little attention in use, and 352 Warming Buildings by Hot Water. the fire can be kept in for several hours with once feeding, so that water of a high temperature can be had at any hour in the night or early morning. This advantage alone is of the utmost value, preventing, for instance, the annoyance arising from the bath water not being hot in the morning owing to the servants rising at irregular hours, and should there be any heating coils in connection with the boiler these continue to give off heat when most needed, during the cold hours of early morning a special advantage if it is a small conser- vatory in which the coil is fixed. Small conservatories are often heated from the kitchen- range boiler, but cannot be at all successful, owing to the kitchen fire being out when the heat is most needed, viz. in the night and early morning. Another advantage, often overlooked, gained by the use of an independent boiler, is the fact that a kitchen range working without a boiler and one working with a boiler give very dif- ferent results indeed. A range without a boiler at the back of the fire works with nearly double the efficiency, rapidity, and general good results of one with a boiler, and the difference in consumption of fuel is most obvious ; a 5-foot range with a high-pressure boiler costs as much in fuel as a 5 -foot range without a boiler, but with a moderate-sized independent boiler ; further than this, the boiler fire can be urged inde- pendently of the range, and the cooking operations need not be regulated with any consideration for the water supply. Independent boilers can be fixed in any position where con- venient for stoking in a basement or cellar, or at the side of the kitchen range, and the smoke-pipe can be connected into the kitchen-range flue. If a vertical shape is selected, it will occupy but little room. Independent boilers can be had in every conceivable design and size, but there is not one yet made that is worthy of any particular recommendation for this work. There are great numbers of excellent boilers, so far as their ability to heat water is concerned, but as hitherto they have hardly ever been used for other than heating purposes only, manufacturers Independent Boilers. 353 Fig. 210. have not been called upon to consider the " fur " question ; this is the drawback to all the existing patterns, as there is hardly one which will admit of easy cleaning. Fig. 210 represents in section a vertical domed top cylin- drical boiler, one occupying little space, and having every con- venience for stoking, &c. ; but a circular boiler of this sort is most difficult to clean out, and it should have at least two man-holes and three or even four mud-holes (holes, about ij inches, at the lowest point for scraping out the loose "fur," as the hand cannot be inserted). This illustration shows a boiler having the water- way terminating at a level with the fire-bars, and an improvement is effected (but at a little more expense) by having the water- way continued to the bottom, as Fig. 211, the greater portion of the fur is then found below the fire-level, where no harm can be done, and what adheres to the flat boiler-plate surface around the fire is more easily removed than from the angle, as in Fig. 210. The fuel used with these boilers is usually coke, an econo- mical and clean fuel, and if the boiler is filled up to the top the charge is sufficient to last a number of hours, varying with the size of the boiler and the way the dampers are set or regulated. The speed of combustion is regulated by a valve at the furnace front, and it can be further regulated by having a valve damper fitted in the smoke nozzle or pipe. The coke fuel must be broken small, about walnut size, otherwise it will wedge or " bridge," and the fire burn hollow by reason of the fresh fuel not falling as the lower portion of the charge is burnt away. 2 A 354 Warming Buildings by Hot Water. A better shape for cleaning purposes is as Fig. 212, as it can have one large or two ordinary lids fitted at the top with mud-holes below, but unless fitted with a " hopper " top to take a charge of fuel, it cannot be kept burning for long Fig. 211. Fig. 212. without attention, and another slight objection is that this shape occupies more room than the cylindrical pattern. It remains for some one to introduce an independent boiler for hot-water supply of a character nearer perfection than we have at present, as, for instance, all small or medium-sized vertical boilers, when fitted with man-lids, have the objection- able wrought-iron plates secured by a number of set-screws, and several other little difficulties present themselves, owing to the necessity of removing the fur, an operation that was not anticipated when they were designed. In ordering an independent boiler the following informa- tion is required before the maker can proceed : State the position that the smoke nozzle is required in, whether on top or whether projecting from the back or either side (the furnace and stoking doors are always situated in front) ; state what size pipe is being used, and indicate where the return pipe is to be connected (the flow pipe should always start from the top) ; indicate where the man-lids should be put, so as to be easily accessible for removal ; state whether -j^-inch or f-inch plate is required (the latter is about one-fifth more expensive than the former), and it is much the better to mention that a valve The Tank System. 355 damper is required in the smoke nozzle, as few makers provide this unless specially ordered. Before proceeding to treat the various fittings, tanks, pipes, &c., used in this work, it will perhaps be best to describe the two most common forms of apparatus in general use, as by this means the explanation devoted to appliances will be rendered more clear. THE TANK SYSTEM. This is the style of apparatus that succeeded the simple arrangement described on p. 332, Fig. 202. Strange to say, it has never had any distinguish- ing name given it, and the Fig. 213. term, "tank system," is only now applied to distinguish it from the cylinder system. Fig. 213 is the general arrangement of this system, and one of the chief features about it, as the name implies, is the tank, which is always fixed, somewhere above the highest draw-off service, com- monly in the bath-room, or an up-stairs linen closet, or in the roof. If the tank is fixed anywhere below the draw-off services, it practically converts the apparatus into the cylinder system, as will be understood directly. As to the position of the tank, this needs some con- sideration ; in the first place it must be below the cold-water cistern ; occasionally it is fixed on a level with this cistern, but in principle this is bad and 2 A 2 356 Warming Buildings by Hot Water. should be avoided, as the least shortness in the cold-water supply interferes with the hot-water, and, what is worse, fixing the tank on a level with the cold-water cistern means necessarily that it is to be fixed in a cold position, in the roof or in a cistern room. This is one of the strong objections to this system, viz. that the tank being at the top of the building must be in a cold situation, and the efficiency of a hot-water supply apparatus is in ratio to the amount of heat it can keep within the water, not the amount of heat it can dissipate, or be robbed of by cold surroundings, which is the aim and object of a heating apparatus. To make this system at all economical as well as suc- cessful, the tank must be kept warm, or in a warm position. This can be done either by having the tank within a closet or in a warm room, or much better by casing and packing it with some poor conductor of heat sawdust, hair, &c. ; the insulation of tanks, pipes, &c., is fully treated on pp. 382 to 387. When the position of the tank is located, a service pipe, known as a " flow " pipe, is carried from the highest point in the boiler to the tank, where it is connected near to the top, either through the side, or through the bottom and projecting up inside, as shown in the illustration. This is the pipe up which the water finds its way from the boiler immediately heat is applied to it. To allow of the corresponding volume of cold water coming down to replace the hot, a second pipe, called the "return" pipe, is provided, starting from a low position in the tank, either from the bottom, as illustrated, or from a low point in the side, and from there it is carried down to near the bottom of the boiler, usually through the top, projecting down inside as shown. It should be noted that it is customary to speak of the "flow" pipe as proceeding from the boiler to the tank, and the " return " pipe as from tank to boiler. The flow pipe should always be connected from the very highest point in the boiler, and on no account must it be screwed through the boiler plate, so that it projects down The Tank System. 357 Fig. 214. inside in the least degree, otherwise an air chamber will be formed. It will be readily understood that if this pipe project through the top plate, as in Fig. 214, the boiler cannot be filled beyond the end of this pipe as shown, as the air cannot be expelled. As an example, supposing an ordinary glass tumbler had a hole drilled in its side, and the tumbler was then inverted and lowered into a vessel of water. The result would be that the tumbler would have the water rise up within it as far as the top edge of the hole, but little further (only so far as a certain compression of the air will allow), and the air in the upper portion of the glass cannot be expelled except by having another hole made at the top (or by shaking the glass violently). This formation of an air chamber in the boiler is a very prolific source of trouble, and it occurs with the greatest frequency either through carelessness or ignorance on the fitter's part. It frequently happens that the fitter connects the flow pipe into the side of the boiler, one of the worst of practices, and only to be tolerated under some very special circumstance : when this is done, the air is got out of the top of the boiler by packing the man-lid, but only partially securing it ; so that when water is allowed to run into the boiler, the air is driven out and the lid then finally tightened up. The particularly ill results experienced from the cause under discussion are that it is accountable for the violent noises and shaking that is sometimes experienced with new work (noises in old work are generally accounted for by furred pipes), as when the boiler is heated and steam generated the latter expels the air, and afterwards the steam itself has to escape, and as both the steam and the air have to be forced down through water to escape up the flow pipe, the violence exhibited cannot be wondered at. A further annoyance and source of trouble arising from this cause, and which is quite as objectionable as the noises, is the fact that as the water is 358 Warming Building^ by Hot Water. not always in contact with the upper boiler plate, the man-lid packing quickly gets destroyed and wants renewing, and this particularly with india-rubber man-lid collars. The flow pipe, as already said, is taken from the highest point in the boiler, and it is continued from there to the tank and connected about half or three-fourths the way up it. This pipe should nowhere be permitted to travel in a downward direction ; if possible, it should be kept gently rising all the way, but more often than not this is impossible, and the pipes that are not fixed vertically have to be carried horizontally, as along passages, beneath floors, &c. There is no positive objection to the pipes being carried horizontally, though it sometimes occasions a check in the circulation, and it is always best if possible to have the pipe more or less on a rising gradient in every part of its length. There are many conflicting notions as to whereabouts in the tank the flow pipe should enter. All are of opinion, of course, that it should be somewhere above the return pipe ; but beyond this there is no universally agreed position. Some contend that the flow should be immediately above the return, with not more than a 3-inch space between the two ; others consider it should enter at least three-fourths the way up the tank ; and there are various other opinions on the subject. There is not the least doubt that the flow pipe should ter- minate about 6 or 8 inches from the top of the tank, for, in the first place, we have to remember that if the quantity of hot water be ever so small, it will be found at the top of the tank (when once it has had time to reach the top of the house) ; and, secondly, and more important, all the draw-off services are taken from this pipe, and as water proceeds both up and down the flow pipe when a tap is opened (as will be shown more fully presently), it would be bad policy to have the upper extremity of the flow pipe anywhere near the bottom where the cold water enters. It is sometimes thought that having the flow pipe entering near the top of the tank (as just recommended) lessens the quantity of hot water at demand, but this idea is erroneous, as it will be seen that, supposing The Tank System. 359 the tank to be three parts full of hot water (the upper three parts, as a matter of course) when a tap is opened, this hot water commences to flow down the flow pipe, and as fast as it does an equal quantity of cold water enters the bottom of the tank from the cold-water cistern, and pushes, so to speak, the hot water up above it (as the cold and hot do not mix readily) and no cold water will issue from the tap until all the hot has passed out ; if the contents of the tank could be watched at this time, it would be found that no noticeable mixing of the hot and cold waters took place, but the quantity of the hot water would be seen gradually growing less at the top of the tank, and the bulk of cold water growing greater and greater, but creeping up from the bottom. All draw-off services are taken from this flow pipe, and it is usual to arrange the apparatus in the best way to avoid long draw-off services, as a long draw-off service means annoyance by having to draw a quantity of cold water (from the hot- water tap) before any hot is obtained ; and this is particularly noticeable at lavatory basins, which usually have small, slow- running taps, and it is not at all uncommon to meet with instances where a lavatory tap will have cold water issue from it for half a minute after being opened, before any hot is obtained. This is a serious objection in another way, as every drop of cold water that flows from a hot-water tap has been heated once, but allowed to get cold for no useful purpose, and no apparatus of this sort ought to admit of a portion of its heat being wasted in this way. It can easily be understood that the water in a long draw-off service remains stationary when the tap is closed, and hot water that is allowed to remain so quickly loses its heat and grows cool, so that when the tap is applied to for hot water this which is cool has to be run off before the hot water issues. Then when the tap is closed the pipe is again left full of hot water only to grow cool before the tap is opened again, and it is by no means uncommon for a single draw-off service on an ill-devised apparatus to waste as much as twenty gallons of hot water per day by this means, and it is by no 360 Warming Buildings by Hot Water. means rare for it to be largely accountable for the failure of an apparatus, as the waste may exceed the quantity of water actually used. A simple remedy, when a long draw-off service must necessarily exist, is to "return" it. This is effected by con- tinuing the service pipe back to where it started from, but connecting it to the return pipe, as Fig. 215. This will permit the water to keep circulat- Flg ' 2I5 ' ing in the draw-off service, and the annoyance is at an end. There is no need for the returned portion of this service to be as large as the draw-off service itself, as it is only required to just keep the water moving, and a drawback to having the returned portion of a large- sized pipe is, that when the tap is opened water will instantly flow towards it along both pipes, and so some of the water will be proceeding from the main return pipe, which is a very objectionable feature ; J-inch may be considered amply large enough for the return to any draw-off service, or even smaller in some instances, as there is no fear of this pipe getting furred up quickly. A bath service rarely requires this attention, as some cold water is nearly always needed here, and it is immaterial which tap it proceeds from. The return pipe is carried from the lowest point in the tank, either from the bottom, or from the side near the bottom, and from thence to about three-fourths the way down the boiler, either through the top or side ; but it may be mentioned here that it is best to carry these pipes from the top surface of the boiler, as bends and elbows, objectionable at any time, are particularly objectionable close to the boiler if hard water is used, as fur always seems to collect within them so much more readily than in straight pipes. It is usual for the return pipe to follow the flow down, and an endeavour is generally made The Tank System. 361 to prevent this pipe rising or ascending anywhere on its way down from tank to boiler, and no pipes are connected to this except the " returns " of draw-off services. In the illustration, Fig. 213 (p. 355, ante), it will be noticed that there is a pipe proceeding from the top of the tank, and carried from there to above the level of the cold-water cistern ; this is the expansion or steam pipe, and its use is to permit the free escape of any steam that may be formed, and also, as its name implies, to permit of the expansion of the water when heated. The difference in bulk between water at 32 (freezing) and water at 212 (boiling) is one in twenty, that is, twenty gallons of water at the former temperature would fill a twenty-one-gallon vessel when raised to boiling temperature. This expansion pipe is usually of I -inch tube, sometimes 3-inch when the apparatus is small, and its top extremity should be at least 3 or 4 feet above the cold-water level. It is necessary to terminate this pipe either over the cold-water cistern, or through a roof or outer wall, as a good deal of water drips from it, and if the boiler overheats a little hot water may be ejected by the steam as it escapes. It is most usual to carry this pipe over the cold cistern, as carrying a pipe through the roof necessitates a little greater trouble and expense, but at the same time a drawback exists in terminating the pipe over the cistern, as any hot water that is thrown out falls into and tends to warm the cold water, which is exceed- ingly objectionable in the hot summer months, and it is at this time that it happens most frequently, as the demand for hot water is then small, and the boiler has every opportunity to overdo its work. When possible it is best to carry the pipe through a wall, but see that it is not over any part of the premises where people may pass or stand under. The lower extremity of this expansion pipe should not project through inside the tank, for the reasons explained in regard to the flow pipe in the boiler ; this is very commonly overlooked, as, unless a flange is ordered to be put on the tank, it is difficult to avoid it. The trouble that may arise, however, is not nearly so great as in the other case, as in a 362 Warming Buildings by Hot Water. general way very little steam finds its way to the top of the house, it being condensed as it passes up the flow pipe ; but if the boiler heats well, or is a little too powerful for the apparatus, some annoyance must be experienced, and care should be taken to avoid dipping this pipe inside the tank whenever it can be avoided. We have now to speak of the pipe or service which brings the cold water to the tank as fast as any of the hot is with- drawn. The " cold supply," as this pipe is called, is brought from any low point in the cold-water cistern, and from there it is carried to and into the apparatus. There are many different opinions as to where this service should be connected, some recommending that it be taken into the return pipe near the tank, others that it be taken into various places in the tank, and advocates can be met with for taking this pipe down to the boiler. What has to be considered wholly and solely is that the inflowing cold water must not materially affect the temperature of the hot water, neither must it be possible to have cold water issuing from the hot taps before all the hot water is withdrawn. It is not necessary to go into particulars just now, but it may be taken for granted that the best place to bring in the cold supply is at the bottom of the tank, as far removed from the return and flow pipes as possible. The reason for this will be clearly understood presently. It will have been noticed in Fig. 213 (p. 355, ante} that the " cold supply " service pipe is carried down with a dip before entering the tank. This dip in the pipe is called the " siphon" (not by any means a correct term, as it is not called upon to answer the purpose of a true siphon, nor could it do so in this inverted form), and it answers the purpose of preventing hot water finding its way up the cold supply into the cold- water cistern, which it would quickly do if this pipe were carried straight from cistern to tank. This dip or " siphon " is usually about 10 to 12 inches deep, and its purpose is ful- filled by the fact that hot water, being of less specific gravity than cold, cannot descend and overcome the superior weight of the latter, and it will be understood, by referring to The Cylinder System. 363 pp. 330, 331, that when hot and cold water are set in motion by their different degrees of gravity, the hot water has no power to descend until it has lost its heat. This pipe is usually f inch or I inch diameter (all water pipes are measured internally), depending upon whether the apparatus is a small or a large one, and it should always be provided with a stop-cock, so that when needed the apparatus may be emptied without drawing off all the cold water in the house, or without plugging the cold-water cistern. The stop- cock should have two special features ; the first being that it should have a loose key, as it should never be interfered with except by those who understand its use (this tap should also have a distinctive label, as there are often several stop-cocks in a house), and the cock should particularly have a "full way," i.e. a i-inch cock should have a i-inch clear way through it, as an impediment of any description in the cold supply will materially interfere with the full flow of water from any and every part of the apparatus, and it will be seen clearly that it is useless having a I -inch service pipe if the stop-tap has only a J-inch way through it. It used to be the regular thing to fit up a small supply cistern, with a ball valve, at the side of the tank ; but few could ever explain why it was used, and as in the majority of instances it was not only useless, but an actual drawback in impeding the free inflow of cold water, it soon fell into disuse, and cannot often be met with now. An instance where this arrangement is a desirable one is when the cold cistern is situated at the top of the house (as usual) and hot water is only required on the ground floor, in which case, to save carrying the expansion pipe to the top of the building, a supply cistern may be fitted, as Fig. 216. THE CYLINDER SYSTEM. This more modern and much improved apparatus is sup- posed to be of American origin, and the chief feature in it, as can be judged by its name, is the cylinder which acts as the hot-water reservoir, and it is necessary to explain, first, why 364 Warming Buildings by Hot Water. a cylindrical reservoir is used with this system, instead of the more familiar rectangular tank. This apparatus, which is illustrated at Fig. 217, has the reservoir in quite a different position to that in the tank Fig. 216. Fig. 217. IKJ system, and the prevailing idea to be followed, and which is one of the chief advantages gained in erecting this apparatus, is to have the reservoir as little above the level of the boiler as pos- sible, so that all the draw-off services can be taken from above it, which is exactly contrary to the plan adopted in the last system explained. The reason that a cylinder is used in place of a tank is simply that the former is capable of bearing a much higher pressure of water than the latter ; and as a cylinder has quite commonly to withstand an internal strain of 25 Ibs. to the square inch, a tank would be totally unsuited, as the strongest of these latter, made of, say ^-inch plate, are not guaranteed The Cylinder System. 365 by the makers to withstand such a pressure as this ; but a cylinder of J-inch plate is always supposed to be tested to 25 Ibs. before it leaves the manufacturer's works ; and a tank or cylinder can always be worked up to the maker's tested pressures. Tanks are and can be used in place of cylinders sometimes when the pressure is light, but unless it is very light indeed some trouble is nearly sure to ensue, especially if the tank does not come from a good maker, as in making tanks it is supposed and intended that they shall not be fixed more than a very few feet below the cold-water level under any circum- stances. Of course, what leads people to use tanks if they have a reasonable excuse for so doing is the desire to economise, as they cost so much less than cylinders ; for instance, one of our best maker's lists prices a 4O-gallon tank, J-inch plate quality, at 2/. n^., whereas a 4<>gallon cylinder, |~inch plate quality, is priced at 3/. 6s. The practical difference, however, is not so very great, as it must be borne in mind that there is a very considerable variation in the pressures they will bear, and it is fairer to compare them in this respect when the dif- ference assumes quite another aspect ; for instance, a 4O-gallon tank tested to 10 Ibs. per square inch (^g-inch plate) is priced 4/. is., and a 4O-gallon cylinder, tested to 15 Ibs. (14 gauge), is 2/. 14$. only. To locate the position of the cylinder first, it is most usual to put this in one of the recesses that are nearly always to be found on either side of the kitchen chimney breast, or if it is impossible to place it here, it can be fixed up in another room, but it must be noted that the proper place for it is as close to the boiler as it can be got, in as warm a position as possible, and the bottom of the cylinder to be between, say 12 inches and 30 inches above the top of the boiler. Between the boiler and the cylinder is carried a flow and return service, as illustrated, and on precisely the same prin- ciple explained in the tank system, although much shorter ; but it should be explained here that cylinders are never sent out with man-lids at the side unless expressly ordered, as they 366 Warming Buildings by Hot Water. Fig. 218. have removable tops, as shown in Fig. 218; but without a side man-lid it is very awkward to reach the pipe connections inside at the bottom, if it is desired to do so. Most makers will put a side man-lid to the medium and better quality cylinders at same charge (in which case the top is a fixture) ; and this is much the most convenient arrangement, but it is necessary to specify this when ordering. It is also most necessary to have flanges put on in the required positions, as illustrated, as it is a poor job to connect the pipes without them. There is no extra charge for these, and there should be one for each flow and return pipe, one centrally on top, for the expansion (or rising main, as it is more often called in this system), and one centrally in the bottom for cold supply. From the extreme top of the cylinder is carried a service- pipe known either as the expansion pipe or " rising main." This is taken by the most convenient way to about 3 or 4 feet above the level of the cold-water cistern at the top of the house, and its upper extremity is terminated in any of the ways explained with the expansion pipe of the tank system. This pipe should be fitted and run in the same manner as a flow-pipe, that is, it should only be carried in horizontal or ascending directions (the former to be avoided if possible), and it is from this pipe that all draw-oft" services are taken, as illustrated in Fig. 217, p. 364, ante. When this pipe is of considerable length, or carried in a horizontal direction to any great extent, it is found desirable, and oftentimes abso- lutely necessary, to return it so that the water it contains may circulate and not become cold. This is a very simple matter indeed, as it is merely to connect a service-pipe at any convenient point, usually close to the highest draw-off service, and carry it down and connect it into the cylinder, in fact, make a secondary flow and return from the cylinder, fitted in general respects like the primary flow and return from a The Cylinder System. 367 boiler. One particular advantage of this secondary return is that it need not come back alongside the rising main ; it may be brought back by any other desirable route, which is a great convenience when the hot-water taps are Fig. 219. wanted scattered about ^ in different parts of the house, as there is no objection whatever to connecting draw-off ser- vices from this return pipe, as in Fig. 219. There is much differ- ence of opinion as to where the lower end of this return pipe should terminate ; every ima- ginable place is sug- gested, and it would be almost difficult to find two average fitters agree- ing exactly on this point. In the last illustration it will be noticed that the termination is made about a third of the way down the cylinder, and although this is a position that only a minority of fitters adopt, yet a very short explanation will show that it is the correct one to obtain the best results. In the first place, we have to aim at being able to withdraw every drop of hot water from the apparatus before having any cold water come from the taps, and in seeking to attain this we have always to bear in mind that when a tap is opened the water instantly rushes from all directions towards the tap in question (the arrows on the last illustration indicate the direction the water takes when a tap is opened, not the direc- tion in which the water circulates when the taps are closed^ 368 Warming Buildings by Hot Water. therefore it will be plainly seen that as the hottest water may be reliably looked for at the top of the cylinder, it would be bad policy to connect this secondary return any lower down than shown, and especially bad to connect it into the bottom of the cylinder where the cold water enters, as is most usually done. There would be no objection to connecting it even higher than illustrated, as every particle of hot water rises to the top of the cylinder before it leaves the apparatus ; it will also be seen that to connect this pipe into the primary return is equally bad. If it is not required to connect any draw-off services from the secondary return, this pipe may be reduced in size. The cold-supply service is brought down from the cold- water cistern to the cylinder, where it is usually connected in at the bottom, as illustrated ; some people, however, connect it into the primary return, and some consider that the boiler itself is the best place to bring the cold supply into ; in general good results the bottom of the cylinder is the most satisfactory ; but in another chapter will be shown a method of reducing the length of this cold-water pipe in many instances. The necessary siphon and stop-cock has to be put in this cold service the same as explained with the tank system. There is a rather important feature that should always appear in this system, but which somehow is very commonly overlooked, even by those who profess this work ; it is a means of emptying the cylinder when the boiler has to be opened for cleaning or any other purpose. It is not by any means an uncommon thing for a workman to find when he attempts to open and clean out a boiler, that there is no provision for emptying the apparatus, except by the draw-off services, which are all taken from the rising main above the cylinder, and he therefore has but two resources one to leave the boiler unopened and uncleaned, the other to take the man-lid off the boiler and let the contents of the cylinder flow into the kitchen, unless the cylinder has the top removed, and the contents siphoned out with a piece of tube into receptacles, which sometimes has to be done. The Cylinder System. 369 The proper thing is to have a short draw-off service fitted below the cylinder, either from this article itself or from the primary return, or from the lowest point in the cold-supply service ; but the tap of this emptying service must have a loose key, which should be kept with the key of the cold- supply stop-cock, so that neither of these taps may be used, except by a competent person, as already explained. The cylinder system has several advantages that the tank system does not possess, but the chief of these is the immunity that it ensures from any danger arising from shortness of water. It will be gathered from the description given that it is most necessary that all ordinary draw-off services be con- nected to the rising main (above the cylinder), making it impossible for the contents of the cylinder to be drawn off except by the special emptying service ; so that should the general supply of water run short, the fire can still be used in the ordinary way, even for a day or two, that is, until the whole of the water in the cylinder is disposed of by evaporation. This advantage alone is sufficient to recommend the system, especially in country residences, where the supply of water is wholly dependent upon an odd man's attention to a pump, and it is almost wonderful that accidents are so rare under these circumstances. One point requiring every consideration in hot-water supply is the pressure exerted by water, either in pipes or vessels, which are used as reservoirs. The pressure of water in pipes is generally calculated by the power it exerts in a pipe having an internal area of I square inch (this would be about a I J-inch round pipe) ; a pipe of this size, 2 ft. 4 in. long, placed verti- cally and filled with water, would be found to weigh i Ib. more than when empty, that is, it contains I Ib. of water ; or, in other words, a column of water, 2 ft. 4 in. high and I inch square, weighs 1 6 oz. It is usual to define the pressure of water as so many pounds to the square inch. The word " pressure " might very well be replaced by the word " weight " in some instances, as it is necessary to understand that the strain exerted only varies as the quantity of water varies, and you 2 B 370 Warming Buildings by Hot Water. cannot get variable pressures from a given quantity of water, as you can with steam or gas, as water is practically incom- pressible. Water in horizontal pipes exerts no appreciable strain, so that in calculating what pressure has to be withstood, it is only necessary to measure the distance the pipe extends vertically, and if the cold-water cistern is situated 35 feet above the cylinder, then this latter should be of sufficient strength to withstand a pressure of 15 Ibs. on every square inch of its internal surface. When a pressure of water is exerted from a pipe into a close vessel, that pressure is transmitted to and felt equally in all parts of the vessel in question, top, bottom, and sides, without diminution ; or in other words, if the supply pipe descends vertically 35 feet, the water within it will exert a pressure of 1 5 Ibs. to the square inch, and this pressure will be felt on every part of the cylinder internally ; and this makes it easily understood why these reservoirs need be so well and strongly made, the strain which some of them have to bear being very great. The following, taken from the list of a London maker, will show the great difference that exists between tanks and cylinders in resisting pressure, and it will be readily seen why a tank is not suited for the cylinder system of apparatus : Riveted and galvanised iron rectangular close tanks, for hot water : Thickness of plate T 3 g- in. i in. 14 g. 16 g. Tested to, per square in 10 Ibs. 5 Ibs. 3 Ibs. lib. Riveted and galvanised iron cylindrical tanks, for hot -water : Thickness of plate ^ in. | in. 14 g. Tested to, per square in 40 Ibs. 25 Ibs. 15 Ibs. In regard to the pressure of water from pipes into closed vessels, it should be remembered that the same strain is exerted upon the internal surface of the cylinder or tank with whatever sized supply pipe may be used, whether it be J-inch or ij-inch or larger. This result may be stated as follows. If the water within a pipe having an internal area of one square inch exerts a pressure of I Ib. for every 2 ft. 4 in. of its vertical Cylinders and Tanks. 3 7 1 height on every square inch within the cylinder, a pipe having an internal area of half this size will only exert half the pressure, i. e. half a lb., or a pipe having an internal area of two square inches will cause a pressure of 2 Ibs., but with the J-inch pipe the pressure of half a lb. will be felt on every half square inch in the cylinder, and with the 2-inch pipe the 2 Ibs. will be exerted on every two square inches, so that the total result is precisely the same. In purchasing tanks or cylinders it is very desirable to get them from makers who have a repute for good quality work. No doubt there are small firms who supply excellent goods, but to purchase tanks or cylinders at a low price will almost certainly prove to be false economy, and nothing is more annoying than to find, when charging a new apparatus to test it, that the tank or cylinder leaks at the joints or rivet holes. It is also unadvisable to use these reservoirs of too light a quality, i. e. those tested to a less pressure than they will have to bear. This is very often done with impunity, as of course, the makers' tested pressure does not indicate the bursting point, and where the pressure is only a pound or two over the makers' test marks no harm will ensue, but it is far better to have the reservoir a trifle too strong, as we have not only to think what it has to withstand now, but also that it will be expected to do the same work several years to come, when it is beginning to suffer from wear and tear. If a tank is of a large size, or unusual shape, it should have " stays " (rods extending from side to side) within it, as immediately pressure is exerted the sides are pushed out, and it has a tendency to become as round in shape as it can get. The following are sizes of tanks and cylinders customarily chosen as being suited for ordinary domestic purposes where no special requirements exist. With the smallest form of apparatus having two taps (scullery and bath), 25 gallons ; this size, however, will be found insufficient if the demand is more than moderate, by reason of a large family occupying the house, and 30 or 35 gallons would be found more suitable ; but regard must be had to the capabilities of the range- 372 Warming Buildings by Hot Water. boiler ; there are exceedingly few 3-foot ranges that have boilers capable of working satisfactorily with a larger reservoir than 25 gallons. In a little larger house, say nine or ten roomed, 40 or 45 gallons will be found a convenient size, the kitchen range being 4 feet (or 3 ft. 6 in. with a fair-sized fire and boiler) ; in larger property the size must be judged according to the number forming the household, and even the number is no sure index, as baths are indulged in much more by some people than others, and the style of living regulates the quantity of hot water required in the scullery, and it is the bath and scullery taps that make the greatest inroad upon the store of hot water. Sixty gallons is a full size for a resi- dence of some pretensions, and it is unusual to exceed this size in private residences, except in mansions of the largest class, and with a large staff of servants (in which case an in- dependent boiler would probably be required). Too large a reservoir is very objectionable, as it renders the work of the boiler almost futile ; it is not so much a great store of water that is required as a moderate amount that can be renewed quickly. PIPES, TAPS, AND OTHER FITTINGS AND APPLIANCES. The kinds of pipe commonly used in this work are wrought- iron steam-tube, galvanised ditto, wrought-iron gas-tube, and lead pipe. There are other kinds less commonly used, such as copper tube, &c. The tube which has preference in the south of England, and which can safely be recommended before any other, is that first mentioned on the above list. This pipe is in general appearance much like gas-tubing, except that its substance is much greater, and in quality of metal it excels the latter ; it can always be distinguished by its being coloured a dull red (except when it is galvanised), whereas gas- tube is always a natural black. Every one having a reputation to uphold uses the steam-tube ; and, although a great deal of gas-pipe is to Pipes, Taps y and Appliances. 373 be found, it will generally be discovered in speculative work of a poor class. The difference in cost between steam and gas tube is about 30 per cent. There is very little galvanised tube used or needed in hard -water districts, as the only object of the galvanising process is to render the tube fairly rust-proof, and so prevent discoloration of the water and weakening of the pipe itself by oxidation. Now the lime which, as already explained, is the cause of the hardness of water, is one of the best of rust- preventives, and it fulfils its usefulness in this direction by coating the internal surface of the pipe with a thin film of carbonate in a very few days, and the rust difficulty is then quite obviated. In soft-water districts, however, some non- rusting tube has of necessity to be used, as water without lime in it always seems to act so vigorously in rusting iron, and the plain steam-tube in these districts causes a good deal of trouble by its being eaten away rapidly and discolouring the water to a greater or less extent. Galvanised tube, if well galvanised, overcomes the difficulty almost perfectly, but care has to be used in fitting it up, as it will not do to forge this pipe in any way (that is, heat it for bending or setting pur- poses), as the galvanised surface will be injured and rusting ensue, and wherever a pipe is cut and screwed, also, the interior of the socket-joints are all places where rusting cannot be helped. Pipes are sold which are galvanised on the outer surface only, but it is almost unnecessary to point out that this must be avoided, as no benefit is obtained by the extra outlay. Caution is also necessary to see that when galvanised steam- tube is ordered, the steam quality and strength is obtained, as this material is not kept in stock by every one, but galvanised gas-tube is. When galvanised tube has of necessity to be used, it is, of course, somewhat necessary to have the boiler galvanised also (or of copper), as the rusting takes place in these almost as badly as in the pipes ; but both galvanised pipes and boilers should only be used when circumstances make it requisite, as 374 Warming Buildings by Hot Water. the acid bath and subsequent galvanising process are con- sidered to be rather detrimental to the iron. Lead pipes and copper boilers and reservoirs are most commonly used in the North of England, particularly in the Manchester and Liverpool districts, where the soft water requires every consideration. Lead pipes certainly do not rust, but there are other disadvantages connected with this material ; for instance, it has been forcibly brought to people's attention that soft water has as vigorous an action on lead (the lead of commerce) as it has upon iron, and the lead which is separated or taken into solution by the water has brought about many serious epidemics of lead poisoning, or plumbism, in various districts, and this led to the introduction of tin -lined lead pipe, that is, lead pipe having its interior surface of metallic tin, which is not acted upon by soft water in the way described. Lead pipe has another drawback, and that is its softness, which permits of its being easily stretched or bulged and weakened by every strain that it is subjected to ; on this account it is almost impossible to use the sudden shutting plug-cocks with lead piping, as the jar or concussion that is occasioned every time a tap is shut soon does serious injury, weakening the pipe and necessitating repairs. This is most noticeable with the taps at the bottom of the house, where a considerable pressure of water may exist, and in these situa- tions the slow-closing screw-down taps should always be used with lead pipes. It must have been noticed by nearly every one that when a plug-cock is closed at all sharply, where a tolerable pressure of water exists, that a somewhat violent noise is heard in the pipe, and the pipe is sometimes shaken. It is when this noise is heard that the strain is exerted which injures soft metal pipes. It has to be remembered that water is practically an in- compressible substance, and in this respect resembles a solid body, so that when we suddenly stop a stream of water flowing under a high pressure within a confined area a considerable resistance must be expected, and this exerts itself chiefly in the vicinity of the tap where the greatest pressure is felt. Pipes, Taps, and Appliances. 375 Shutting a tap 50 feet below the cold-water cistern causes a pressure of about 2 1 Ibs. to be brought to bear on every square inch of pipe surface near the tap in question ; if the tap is closed slowly the strain is reduced to a minimum, but if closed sharply the strain assumes the character of a blow. The tin-lined lead pipe referred to overcomes this trouble to some extent, as tin is harder and of a more rigid nature than lead, but of course, not so much so as iron. The different strains brought to bear in this work have not only the effect of bulging and weakening lead pipe, .but also an even worse effect in causing the pipe to be stretched lengthwise, which ill effect is of greater frequency than the bulging. An instance of this recently came under notice (in London) in which lead pipe of a very fair weight had been used, but which proved to be a very marked failure, owing partly to insufficient hooking up and partly to a considerable length being carried up a high, straight casing in which it was difficult to give it good support The result was that the horizontal pipe sagged down between the hooks, and the vertical pipe became lengthened several inches by its own weight and the pressure of water within it, so that in a few months it was exactly as Fig. 220. In this instance the con- tractors were compelled to renew the whole apparatus in iron at Fi S- 22 - their own expense. When the flow and return ^ services are lead pipe it is gene- , rally necessary to have the ends nearest the boiler of iron, the former material being fusible at a moderately high temperature, and fusing is likely to occur if the pipes are furred or if the boiler is emptied (by a workman) immediately after the fire is extinguished and before the surrounding metal and brickwork have lost any of their heat. An important point which, up to the present, has only been just touched upon, is the size of pipes most suitable for IB II 37 6 Warming Buildings by Hot Water. different services and purposes. This, like many other matters connected with hot-water supply, is greatly regulated by the fur difficulty, which makes it necessary to use much larger pipes than are needed in soft-water districts. There is a definite limit as to the size of pipes ; and although com- paratively large pipes are always recommended for the two reasons about to be explained, yet to increase the pipes beyond a certain point is most disadvantageous. A large pipe is considered to be conducive to a freer cir- culation, that is, the water can travel from boiler to tank at a greater speed on account of the lessened friction, and it is certainly beneficial for the water to leave the boiler as fast as possible when it has absorbed heat ; but this advantage alone would not be generally considered of sufficient importance to warrant the great cost of larger pipes and the increased labour in fixing them. The reason which sanctions the greater outlay will be found, in nearly every case, to be the wish to lengthen the time in which pipes become furred up and require renewal. One-inch pipe is very largely used for the main flow and return services, and it is a size that will give excellent results so long as the passage within it remains an inch, and even when the incrusted deposit has reduced the bore to f inch there is very little to complain of (unless the apparatus is on an extensive scale) ; i-inch may, therefore, be considered a suitable size in soft-water districts for general domestic work ; but if the apparatus is of a large size, in an hotel or institution, Ij-inch, and in some instances I J-inch should be recommended. In hard-water districts, i^-inch is best for ordinary residence work, but if, in a tank system, the flow and return pipes are of considerable length, an economy may be permitted by reducing the size to i-inch, say 30 feet from the boiler, as the incrustation will be found in almost every instance to be much less at the tank end of a long pipe than near the boiler. In a cylinder apparatus, unless very small, the short flow and return from cylinder to boiler should always be i^-inch ; all other pipes in this system may be smaller. Pipes, Taps, and Appliances. 377 In the tank system the expansion pipe and cold supply for moderate sized work may both be f-inch, but for a good sized residence, where a fair demand for hot water exists, the supply pipe should be i-inch, and the expansion should be in- creased to I -inch also. The sizes of the draw-off services should be, I -inch pipe for baths, |-inch for scullery, pantry, house- maids' sinks and general purposes, J-inch for lavatory basins and any small purpose ; these sizes, for draw-off services, are usually adopted in both small and large works on any system. In the cylinder apparatus the primary flow and return should be I J-inch, as mentioned ; the rising main or secondary flow may be f-inch in small property, but never less than I -inch in work of a fair size ; if this pipe is returned (forming a secondary return) this may be J-inch or f-inch, according to the magnitude of the installation, and the cold supply should be either J-inch or i-inch (with a full way stop-cock), also accord- ing to the importance of the work in hand. The great objec- tion to a small cold supply service is that it reduces, i. e. checks the flow of water from the taps of the apparatus. When a pipe becomes furred, the bore becomes reduced in size, and would, if permitted, eventually become quite stopped, ending in an explosion at the boiler ; but an explosion from this cause has most probably never occurred, as, before any real danger exists, such violent noises and vibrations are noticed, that an experienced man is called in, owing to the apprehension of danger that arises. It is gene- rally when the bore has been reduced to about f inch (depend- ing, however, upon the power of the boiler) that the noises are first heard, and which are caused wholly by the steam being unable to escape freely ; usually the flow pipe gets the greatest share of the fur, in which case the violence arises by some proportion of the steam forcing itself into the return pipe. A i J-inch pipe will last nearly double the time a i-inch pipe will before giving trouble, as, in the first place, a J-inch deposit is longer in accumulating on a I J-inch than on a i-inch surface, and when the former has a J-inch deposit it is still fit for a great deal of service ; whereas the latter is upon the point 378 Warming B-itildings by Hot Water. of giving trouble. It should be mentioned that it is commonly the case for the supply of hot water to become lessened and somewhat uncertain when pipes are badly furred, commencing before the noises are heard. It is quite possible to have the pipes cleaned of fur when the occasion arises, but this necessitates their removal, and a somewhat lengthy job afterwards in heating and hammering them, and it will be found as cheap and decidedly better to replace them with new. TAPS. There is, as every one knows, an enormous variety of these in the market, but notwithstanding the many improvements and advanced ideas in this direction, a perfect tap, or a nearly perfect one, still remains to be introduced. There are numbers of these articles to be met with, that display excel- lence of quality and careful workmanship and finish, yet it is doubtful if any maker is prepared to supply a f -inch bib-tap for hot water, guaranteed to last more than twelve months without leaking, in a large residence where the tap is in fairly constant use at the scullery sink, for instance. The most usual form of tap to be met with, and one which is found to give fairly good results, is that having a plug through its centre and known as a plug-cock (Fig. 221). Fig. 221. Fig. 222. Fig. 223. These are made either with a nut bottom (a nut being screwed on to the plug at its lower end), as illustrated, or with a solid bottom, the plug being secured with a cap screwed on at the top, as Fig. 222, this cap forming a stuffing-box ; or there is another with a solid bottom, the plug being secured by a plate at the top (Fig. 223), this being called a "gland" tap. Taps. 379 Either of the two latter are preferable to the former, as those secured by a nut at the bottom sometimes leak at that point, which is impossible with the others. These three are the forms of tap alluded to in a former paper as " quick-shutting " (in contradistinction to the slow-shutting screw-down taps), and which cause the concussive noise in the pipe when shut off suddenly where a good pressure of water exists. There is a very simple remedy for this, which will at the same time check the violent outrush of water experienced when a great pressure exists ; this is effected by reducing the bore of the tap at what is called the "tail," the screwed portion that enters the pipe, as in Fig. 224. This is quite understood by the makers, many of whom keep '^224- these "checked " taps in stock. Workmen some- times do this themselves by cutting a circular piece of sheet brass or zinc, and, after making a suitable hole in it, solder it on to the end of the tail. Where there is a pressure of 1 5 Ibs. to 20 Ibs. (cold-water cistern situated 35 feet or 46 feet above the tap), the hole in the tail of the tap may be reduced to \ inch ; with a lO-lb. pressure a f-inch hole is ample. Screw-down taps overcome the concussion difficulty, by its being impossible to close them suddenly ; but these taps, however well made, require " re-leathering " periodically, that is, the seating or diaphragm, whether rubber, leather, or com- position, requires renewing somewhat frequently, and if the tap is not of good quality the thread of the screw-down arrangement wears or strips off quickly. This style of tap is now largely used, but it has an opponent in every servant that has to use it, as it cannot be opened or closed quickly, and in many busy houses a tap is oftentimes applied to a dozen or more times per hour, in which case the unscrewing and screwing usually leads to a loss of temper. There is a modified form of this tap now being made which can be opened or closed in one turn, or they can be had to open or close with a half turn, which is as quick as a plug-cock ; this overcomes the difficulty just referred to, but 380 Warming Buildings by Hot Water. a new disadvantage is introduced with them, as when the abrupt thread of the screw-down arrangement wears loose, a fair pressure of water will lift the seating slightly, and permit of leakage, and the thread of a screw-down tap is a trouble- some part to repair. It is now considered best, when purchasing baths or lavatory basins, to choose those that have the hot and cold taps fitted and attached to them, so that the connection of the pipes to the unions provided is all that is needed to complete them. This is a much better and neater arrangement than having the taps projecting from the wall over the basin or bath, and it not infrequently happens, when this is done, that the hot and cold taps will be found of different patterns, as the hot and cold draw-off services are so commonly fitted up by different tradesmen (hot-water fitter and plumber). When the taps are fitted to the bath or basin by the maker they are sometimes placed out of sight, only the handles being visible, these having porcelain discs upon them marked either " HOT " or " COLD," and altogether a very superior result is effected with very little extra cost. It has been the usual practice with makers, when supply- ing baths fitted with taps, to place the taps in question on, or nearly on, the rim of the bath, so that the water issuing has to fall about 18 inches ; there is no objection to this with the cold-water tap, but with the hot tap it is an objection, as the falling hot water throws clouds of steam into the room, making it very unpleasant, particularly if the room be small. This objection is overcome by having the hot-water inlet situated near the bottom of the bath (not in the bottom itself), so that it is quickly covered with water, which prevents the steam arising ; it is as well to have both hot and cold inlets thus situated, as the bath will then fill noiselessly. This arrangement must not on any account be confounded with the method adopted in the old pattern zinc and copper baths to be met with, into which the hot and cold water issues through the waste grating in the bottom of the bath ; the particular objection to this is that, when the bath is emptied Bath Taps. after bathing, a certain amount of soapy, objectionable sedi- ment is always left just in the waste outlet beneath the grating, and this substance is washed back into the bath by the inflowing water when the next person makes ready to bathe. It is very desirable to have fair sized service pipes carried and connected to a bath, and the taps should be as large as possible, say I inch, as a slow-filling bath is as much a source of annoyance as one that empties slowly. The majority of best quality and even many cheap-made baths are now fitted with the taps and with soap and sponge trays, all within the bath ; this is an excellent feature, pre- venting drip water and soapy matter finding its way to the floor, or if the bath is encased it prevents the woodwork being injured from the same cause. When the bath taps are placed on the wood bath rim there is invariably a collection of dirt there, unless they are very carefully cleaned, and in this latter case the cleaning leads to the polish being rubbed off the wood- work and creating an unsightly appearance around the taps. A very useful and not expensive adjunct to a bath is a shower apparatus ; the old form of Fig. 225. Fig. 226. this appliance was a most in- convenient and troublesome thing, as it consisted of a sus- pended vessel or reservoir which had first to be filled before allowing its contents to be showered down ; this, although cumbersome and unsightly, answered very well with cold water, but if a warm or tepid shower was required there was no way of testing the temperature except by climbing up and testing it with the hand ; otherwise the result would be most uncertain, if not risky. The more modern form of shower attachment is as Fig. 225, consisting of a board of polished wood (to match the bath 382 Warming Buildings by Hot Water. casing) on which is fixed the hot and cold taps and the shower rose ; the method of connecting the pipes is shown at Fig. 226, which illustrates the back of the board. It will be seen how simply the temperature can be regulated, so that, if desired, the shower can gradually be made to vary from warm to cold, and the shower can be continued any length of time. A further useful adjunct which can be attached to the shower board inexpensively is a small tap with a nozzle, to which can be secured a piece of india-rubber tube, and this, if fitted with a rose, can be used either for shampooing purposes or for rinsing out the bath after use. COVERING PIPES AND RESERVOIRS FOR THE CONSERVA- TION OF HEAT. There is no branch subject in connection with hot-water work deserving so much attention as this. It is no exaggera- tion to say that very shortly no apparatus for hot-water supply will be considered complete or finished if the whole system in not insulated, so to speak, so that almost every particle of heat absorbed by the water in the boiler will be obtainable from the taps, instead of nearly 50 per cent, of it being radiated from exposed surfaces, and worse than wasted. There are at this moment hundreds, if not thousands, of hot-water systems that, by being carefully covered, would be converted from miserably inefficient to highly satisfactory appliances, this in particular with the tank system, when the tank is so commonly fixed in a cold, draughty roof. An interesting instance of the success attending the covering of pipes occurred quite recently, in which a residence was fitted with a complete system of hot-water supply pipes on a scale sufficiently large for a good boiler in a 5-foot kitchen range, but owing to a delay experienced in obtaining the range in question, another of a smaller size, 3 feet, was fitted up and connected to the chimney and circulating pipes Conservation of Heat. 383 for temporary cooking and hot-water supply. It was not supposed that this little range with its boiler would do much in the way of water-heating, but to the astonishment of every one it gave a really abundant supply of very hot water in every part of the house as quickly in the morning and altogether as satisfactorily as a larger range would be expected to do. This desirable result was wholly brought about by the pipes and cylinder being everywhere carefully covered with a sufficient thickness of felt, so that however hot the water was within the pipes, no heat could be felt outside the covering, a sure indication that no heat was being dissipated. It really does seem opposed to all reasonable and work- manlike principles to allow such abundant opportunity for heat to be thrown away, while labour and fuel is being expended in the kitchen apparently for this object. If a fitter or maker of steam engines and appliances did not attend to this subject in a thorough and workmanlike manner he would be considered to have hardly mastered the rudiments of his business. The waste of heat is not always the only ill-result experienced, as in many in- stances the warmed air is very objectionable, and if a hot- water pipe is carried alongside a soil-pipe it is possible for a very unpleasant feature to introduce itself. It is a very customary practice for a hot-water fitter to carry his pipes up in the casing that is nearly always to be found passing from the bottom to the top of the house, this casing containing all the different pipes of the house, such as the cold service from the main, the cold service down from cistern, the W.C. cold- water services, and, very commonly, the soil-pipe. There is no objection to his making use of this casing if it is large enough to hold a few more pipes, and it is often used of necessity, as to carry pipes openly through well-decorated rooms is out of the question ; but to carry hot-water pipes up this case without felting them is an exceedingly bad practice, as they are not only brought into contact with very cold surfaces (they have frequently been found wired on to cold 384 Warming Buildings by Hot Water. pipes, four or five pipes in a bundle), but the heat radiated causes a draught or current of air to set in, as we find in a chimney. When a casing contains pipes that radiate heat, that casing, within a few moments after the heat is felt within it, is converted into a flue, as by applying heat to air it can be made to circulate to all intents and purposes like water. Air that is brought in contact with heated surfaces becomes heated and rarefied, and, being thus made lighter than the surrounding air, rises, and cold particles immediately flow in to take its place, they becoming heated and following the first particles, and so on, so that it resolves itself into a stream of warmed air, flowing out of the upper part of the casing, and cold air flowing in in corresponding volume below. This may be excellent in practice when hot-water pipes are used for effecting ventilation ; but it is fatal to hot-water services which are particularly required to keep the heat within them ; in many instances they are cooled at about the same speed as they would be if placed outdoors when a strong wind v/as blowing. It may be argued, that if the casing is stopped off at its two extremities, the trouble will be obviated, and so it would be if the casing was perfectly air-tight everywhere, and had no cold pipes within it ; but this is never the case, there are always numbers of crevices and apertures which permit of a tolerably free ingress and egress of air. The best material for covering these pipes and also the reservoirs is hair felt ; hair is a natural poor conductor of heat, and nothing supasses it for this purpose, especially as it is so easy of application. This felt, which is readily obtainable in sheets, is usually cut up in strips for pipe-work ; the strips are wound upon the pipe spirally, being secured here and there with cord or wire, but where spiral winding is impossible it can be tied on in lengths, which answers equally well but has not such a good appearance. The best and most complete arrangement for pipe-work, but which entails a little greater expense, is to have the felt Conservation of Heat. 385 wound on spirally in one direction, say from left to right, and well secured with cord ; then cover this with good canvas, also wound on, but in the opposite direction, and this secured with wire. It is most necessary, to secure the best results, to have the felt thick enough ; hair felt is sold in great quantities about Y S g inch thick, but this is not thick enough for good work. If possible have it \ inch thick, and a marked benefit will be had by using even thicker than this, or, say, two thicknesses of f inch. In felting cylinders, it is the best plan to take sufficient sheets of felt, and then sew the edges together to form one sheet large enough to go all round the reservoir. This sheet can then best be secured by bands of hoop-iron or brass passed round at top and bottom, and around the middle ; these bands being tightened up by having a bolt to draw the two ends together, as Fi S- 22 7- Fig. 227. After this circular pieces can be cut for top and bottom ; these pieces being sewed on to the top and bottom edges of the large sheet. Tanks can be covered in exactly the same way. Sometimes it is desired to encase the tank or cylinder with woodwork. This makes by far the neatest job, though more expensive, and it causes a little trouble should it be necessary to open the reservoir under some circumstances. If it is decided to have a casing, it is very important that the space between the woodwork and the reservoir be well filled- in with some poor conductor of heat, such as cow hair (plas- terers' hair), slag wool, or even dry sawdust answers very well when the casing can be filled from the top. If the casing is not " packed " with something it would be much better to be without it, as it would have a current of cold air passing up through it, the same as explained with the general pipe casing just referred to. If the hot- water service-pipes are carried up through the 2 c 386 Warming Buildings by Hot Water. house without entering the general pipe casing mentioned, and it is proposed to encase them for the sake of appearance, this casing must also be packed for the reasons explained, but this is frequently neglected with the worst results, as the casing of pipes is frequently done for appearance sake only, the question of radiation not being considered. Occasionally it is found practically impossible to carry the pipes up inside the house, in which case it becomes necessary to take them up outside, but in this instance, casing becomes an important necessity not only to prevent the failure that must ensue by loss of heat, but to also prevent danger from frozen pipes in winter. For outside work the case should be large enough to have one inch of felt between the wood and the pipes, and it should be very securely attached to the wall, as should it come away the pipes would be exposed, as they lay flat and tight against the wall. A method sometimes adopted for covering outside pipes is to run them within a larger pipe, such as is used for rain water, filling in the intervening space with sand or some other material. This plan is neat and convenient in the first instance, but it is very disadvantageous should a leakage occur, when it becomes necessary to displace most of the large pipes, or to break out one of the lengths. There are various materials in the market prepared and sold expressly for covering heated surfaces to prevent radia- tion and loss of heat ; these generally take the form of a cement, and are largely used for coating steam-boilers and tubes in which conservation of heat is so very necessary ; but these materials have not been taken to at all favourably by hot-water engineers. No doubt the chief reason is that they are a little difficult of application compared with felt and some other substances, and with these latter there is less trouble occasioned should it be necessary to expose and afterwards re-cover the pipes. . There is a material deserving of special mention on account of its excellent qualities, and which is used alike by steam and hot-water engineers. This is " silicate cotton," a Conversion of Tank Apparatus. 387 substance obtained as a waste product from blast furnaces ; it is of a fine, soft, woolly nature, and an excellent poor conductor of heat, as it is wholly composed of glass (silica). For packing pipe cases it excels hair, and its cost is very reasonable, being about I2s. per cwt. Asbestos is, of course, a suitable material for the purpose under discussion, but it is little used in hot-water work, probably on account of its cost. Sand, where it can be used, is also a poor conductor of heat, as this is chiefly composed of silica, the same as silicate cotton ; but it is not so easy of application as this latter material, which is a woolly glass. CONVERSION OF A TANK APPARATUS TO THE CYLINDER SYSTEM. It very frequently happens that when any extensive repair is being carried out, or from some other such cause, it is thought desirable to convert an old apparatus to the more modern system, and the change can usually be effected with- out very great expense, that is to say, at considerably less expense than erecting a new apparatus. The most usual method, when circumstances will allow, is to utilise the existing flow and return pipes of the tank system for the rising main and cold supply to the cylinder, respectively. Fig. 228 shows a small, ordinary style of tank apparatus, and Fig. 229 shows the same apparatus converted. It will be seen that the conversion requires the removal of the tank entirely by this method. The flow pipe which entered the tank has to be continued up to above the level of the cold-water cistern ; the cold supply service which was carried into the tank must be connected on to what was the return pipe, and this completes the alteration at the top of the house. In or near the kitchen the original flow and return services have to be cut, and the cylinder inserted as shown, the flow and return from the boiler being connected into the 2 C 2 388 Warming Buildings by Hot Water. cylinder in the usual way. The continuation of the flow pipe has to be connected into the cylinder at the top to form the rising main service, and lastly, the lower extremity of the cut return pipe (which is now connected with the cold-water cistern at the top of the house) has to be carried into the bottom of the cylinder, forming the cold supply. The stop- Fig. 228. Fig. 229. cock in this service, which we have left at the top of the house, can, of course, remain there, but it is much better to bring it down close to the cylinder, so that when a workman has to use it there is no occasion for him to traverse the house three or four times, certainly twice. The alteration at the top of the house can be lessened if desired by the non-removal of the tank, this article being left to increase the cold-water supply ; in this case the only change to be effected at the top of the house is to convert the flow pipe into a rising main carried to above the level of the cold cistern, as Fig. 230. It will be noticed that the conversion described (Fig. 229) does not provide for the rising main being returned ; this, if it is necessary, must be a distinct and new service, and it Conversion of Tank Apparatus. 389 becomes a necessity should there be any draw-off services that were " returned " ; as otherwise there will be no service pipe to return them into. This brings to notice the only dis- advantage of the cylinder system, which is that a good and complete apparatus has to have three pipes down the house, whereas the tank system needs only two ; but after all, the Fig. 230. Fig. 231. difference is not so very great, as the pipes above the cylinder do not require to be so large as the flow and return of a tank apparatus. Sometimes the conversion can be effected without inter- fering with the tank at all, but the circumstances have to be rather special. As an instance, let it be supposed that the existing tank system, which is to be converted, has a tank, say 25 or 30 gallons, which has proved to be rather insufficient for the demand ; or supposing the demand for hot water has increased and a larger kitchen range or a larger boiler is being introduced, then in either of these instances, instead of taking away the tank, it can be allowed to remain and a small-sized cylinder inserted below, as Fig. 231, it being arranged for the contents of tank and cylinder together to be, 390 Warming Buildings by Hot Water. Sa 7> 55 to 60 gallons, if the range is of fair size, or according to the general requirements. This arrangement can be but seldom resorted to, as most usually the tank will be found of ample size, and capable of fulfilling the demand, in which case to insert an additional reservoir would in all probability be more than the boiler could heat successfully, and a limited success in this work may be considered a failure. The illustration shows exactly what is necessary in a con- version of this character. There is no alteration whatever needed in the upper part of the house, except that it must be seen that the flow pipe in the tank terminates in a high position, say, within 3 inches or 4 inches of the top, and not on any account near the bottom of it. The insertion of the cylinder below differs a little from the arrangement last ex- plained, as will be seen by comparing the two illustrations, as the original return pipe still remains a return pipe, and instead of being connected high up into the side of the cylinder, it must be brought in at or near the bottom, as we cannot look for much hot water in this pipe, and it must be kept away from the draw-off services accordingly. When a conversion is effected, and it is found that a draw- off service is connected to the flow pipe below the cylinder, this service must be cut off and reconnected to the rising main above the cylinder, as it will now be understood that the chief advantage, the safety, of this system is effected by omitting all means of emptying the cylinder, except by the special cock with loose key that is provided for workmen's use and emergency. If, in the conversion last explained, anything would be gained by leaving the original return pipe untouched, this may be done, as no particular benefit will be effected by cutting this pipe and connecting the two ends into the cylinder ; it can be left as it existed before, running from the tank to the boiler, the cylinder being inserted into the flow pipe only. This makes the cylinder to all intents and purposes like a large bulge, an enlargement, low down in the flow pipe. Twin Boilers. 391 TWIN BOILERS AND SERVICES. There are at this moment hundreds, if not thousands, of houses, particularly in the West-end of London, that have the old-fashioned open ranges in their kitchens, these ranges having two boilers fitted in them. These are not exactly " twin " boilers, but they will serve to illustrate the use and occasional necessity of these articles. The object of having two boilers in these old ranges was twofold ; firstly, one boiler was considered and generally found to be incapable of providing sufficient hot water for the whole house, and it became necessary to put in two boilers with a proportionate increase in the size (width) of the fire, so that one could be used and kept distinct for kitchen supply, and the other for baths and the other taps in the house. This arrangement was so customary that makers of modern ranges are continually being asked if they are sure the one boiler in their ranges is sufficient for all purposes, and the enquirer is often incredulous if answered in the affirmative, as the boiler in a modern range may only be half the size of one of the boilers in their existing range. The only argument in favour of the two boilers in the range was that the demand for hot water in the servants' offices need not exhaust the bath supply, or vice versd, but this argument cannot hold good with a modern range, pro- vided it has a good boiler. The arrangement of two boilers, however, became so customary that great numbers of houses will be found to have a cistern at the top and another below, one for upstairs use, and one for kitchen supply (for both hot and cold water), but this is now quite unnecessary so far as the hot water is concerned. Sometimes instead of two boilers a single boiler of large size was used, this boiler supplying the kitchen under low pressure, and within this boiler was fitted a coil of pipes which acted as a heating medium for a hot-water circulating apparatus, that was in connection with them, for bath supply, 392 Warming Buildings by Hot Water. &c. ; this is a wretched arrangement, as, in the first place, hot water is a poor medium to heat water with, and secondly, every time a drop of hot water was drawn in the kitchen the coil was cooled to some extent by the cold water flowing in. The two boilers were better than this, but neither could possibly be recommended now. An occasion that arises for the use of twin boilers is when the cistern at the top of the house is insufficiently large for all purposes, and the cistern which we must suppose exists down below has of necessity to be relied upon. It will be obvious that the two cisterns cannot anyhow be made to supply one apparatus (if any part of the apparatus extends up above the lower cistern), and it becomes necessary to have two boilers in the fire, each doing distinct work with a distinct supply. This, fortunately, rarely happens, as it is an unsatisfactory arrangement, and an effort is always made to overcome the difficulty by adding to the storage capacity of the cistern at the house-top, so that it can meet all demands, and so need only one boiler. It is hardly necessary to mention that the arrangement of two boilers is much the more costly, and as it Fig. 232. Fig. 233. CD o o necessitates an increase in the width of the fire the consump- tion of fuel is greater, and the range has to be strengthened to withstand the greater wear and tear caused by the greater heat evolved, &c. Fig. 232 illustrates a pair of boilers to go at the back of a kitchen range, but to get a separate flue to each it becomes Two Boilers to one Apparatus. 393 necessary to have the fire of a most extravagant width, espe- cially if both boilers are not required all day. The difficulty is, therefore, overcome to some extent by making the boilers as Fig. 233, but here a disadvantage presents itself in the fact that no means can well be devised to work one boiler inde- pendently of the other. When a pair of boilers are really necessary, it is practically impossible to make them each of an exactly suitable size for the work each has to do. The consequence of this is that in all probability one boiler will overdo its work, and the other fail, and under any circumstances some annoyance will be felt by the boilers working unequally. A very marked instance of this is when one boiler is used for circulation, and one for steam cooking. The circulating boiler must, of course, be capable of good work, and the steam boiler has to be powerful. Yet this latter boiler may be only in use for two or three hours in the morning, and for the rest of the day the increased size of fire is a mere waste of fuel, and the water boiling furiously for no purpose. If it is at all possible to avoid using two boilers in one fire, it is much the best to do so. Coming within this subject is an arrangement for connect- ing and using two distinct boilers (say, in two different rooms) attached to one circulating apparatus ; this is often resorted to, and is frequently of great convenience, particularly where the demand for hot water varies to any great extent during the day or in different seasons. In some institutions, colleges for instance, the quantity of warm water required for early bathing is frequently veiy large, and complaints then occur of the kitchen-range boiler being quite unequal to meet this excessive demand, although quite able to supply sufficient at other times in the day. The remedy, in this instance, would be to introduce an independent boiler ; but on this occasion it would be best to still retain the services of the range boiler, as it will not only aid the other materially, but it will permit of the independent boiler fire being let out when the demand has slackened ; or there are cases where a second range of smaller size exists in the kitchen or scullery, and if fitted with 394 Warming Buildings by Hot Water. a circulating boiler it can be connected on to the apparatus which is worked by the large range, so that whichever is in use (or if both are at work) the supply of hot water does not cease. The usual way of connecting up the two boilers is as shown at Fig. 234, the flow pipe from each being joined at the nearest point, and the Fig. 234. return pipes in a similar manner ; if it is the cylinder system the pipes can be made to enter the cylinder from each side, or they can be jointed at the nearest point as just explained. It is sometimes re- commended under this arrangement to have a stop-cock inserted in each flow and return pipe (four in all), so that when one boiler is undergoing any repair or being cleaned, the stop-cocks in that pair of pipes can be closed, and so permit of the other fire being used, and pro- viding the customary hot-water and cooking conveniences. This is certainly very convenient, but the introduction of stop- cocks into the main (primary) flow and return pipes is a most objectionable and sometimes disastrous practice ; the least forgetfulness, or any conscious or unconscious trifling with the cocks, may lead to an accident, which is invariably fatal to any one who may be near.* Sometimes twin boilers can be avoided by carrying two distinct sets of pipes from one boiler, but it will be clearly understood that these two systems must be fed by one cistern * It is but a short time ago that a plumber a practical man lost his life through omitting to open these stop-cocks when testing a boiler, after having done some work which necessitated their being closed. He was killed instantaneously. Experimental Results. 395 (or two cisterns on the same level), with the expansion pipes both carried to an equal height, otherwise one will, of course, overflow the other the instant they are charged (unless an arrangement of stop-cocks is introduced, which, however, would not permit of the two systems being worked at one and the same time). An arrangement of this kind is of use when one or two small coils are to be heated, say, for an entrance-hall, from the kitchen boiler, it is then best if it can be possibly managed to take a flow and return service from the boiler, independent of the ordinary flow and return ; this coil service may have stop-cocks, provided none are inserted in the other pair of pipes, and this will permit of shutting off the coils when the tank or cylinder is to be heated up quickly, or when the heat from the coils is needed. This subject of coils in connection with kitchen-range boilers will be treated fully later on. There is no objection to carrying more than one rising main (secondary flow) service from the top of the cylinder, if hot water is wanted at a distance in different directions, these various services being either brought back into one return or each having its own return to the cylinder. At one of the H6tels Metropole, just erected, there are four i J-inch secondary flow pipes, as water is wanted in great quantity in different parts of the building ; the cylinder, however, is heated by steam, being made of copper and much like a multitubular boiler, but of course an independent boiler would heat it equally well if there was not steam to spare. IMPROVED AND OTHER SYSTEMS ; PECULIARITIES NOTICED FROM EXPERIMENTS, AND THEIR RESULTS IN PRACTICE. Perhaps one of the most interesting, as well as instructive, things that it is worth any one's while to erect, is a model hot- water apparatus ; its construction is simplicity itself, and to those who are at all interested it well repays the trouble. It would prove a most expensive undertaking to have the pipes especially made of iron, and the joints in themselves would 396 Warming Buildings by Hot Water. possibly deter the most ardent, and what would prove most fatal to this arrangement is that, when erected, results could only be tested by feeling the different parts of the structure, and judging by the temperature outside, the same as in an ordinary house system. If we make the reservoir of glass, and use a small-sized glass tube (say J-inch) for the pipes, we then have an apparatus that will permit of its interior phenomena being thoroughly investigated, every peculiarity, however trivial its action, being instantly noticeable ; and, provided the proportions are about true, every reliance can be placed on it as a model of the actual working of a system. Amber dust, obtained by , filing up a piece of broken pipe mouthpiece (provided it is amber), will render the movements of the water easily per- ceptible, as it is a material the particles of which will be found to remain perfectly still in still water, and only move as the particles of water propel them. The glass tube can be jointed with rubber tubing. Perhaps one of the most useful results noticed in an ap- paratus of this kind, and which has proved to be a result of almost every day utility to many who have noticed it, is that water proceeds both up and down a flow pipe in equal volume when a draw-off tap connected to that pipe is opened. This is a perfectly natural result, for any work on hydrostatics shows us that in an apparatus of this kind the water cannot very well proceed from one way only ; yet if a number of intelligent hot-water fitters were asked from whence does the water come that flows out of a tap when it is opened, whether up the flow pipe from the boiler or down the flow pipe from the tank (on the tank system), the chances are that not one would say that the water proceeds equally half each way. The consequence is that numberless mistakes occur, some of them very per- plexing to the uninitiated. To more clearly explain the phenomena in question, if we erect a double tube, as at Fig. 235, and insert a draw-off tap in it at any point, as shown, and we then open the tap, what takes place ? The water that issues from the tap does Experimental Results. 397 not wholly proceed from the pipe above the tap, neither does it wholly proceed from that portion of the pipe below, for it will be found that as the water flows so will the level of water in the pipes be lowered exactly equal in each pipe, and this is a sure indication that the pressure both down and up is exactly equal, the same as Fi S- 2 35- if the lower part of the tube were taken away, as in Fig. 236. This will make it clear that we must expect water from both directions when a tap is opened anywhere in the circulating pipes of a hot-water apparatus, as we have only to place a boiler at the lower end of the pipes (Fig. 235) and a reservoir at the top extremity to have | ij^ a tank apparatus almost complete. The commonest fault arising from an ignorance of this fact is the " returning " of a draw-off service on a tank apparatus. The draw-off service, of course, proceeds from the flow pipe, and is carried back and connected into the return, and the effect is that the water does not lie stagnant, as it does in a single pipe, and the hot water is brought right up to the tap, or nearly so ; everything is satisfactory up to this point, but im- Fig. 236. mediately the tap is opened a partial failure manifests itself, for water will instantly proceed in equal quantities from both flow and return pipes, and as it is the exception rather than the rule for the return pipe to be hot, the water that issues from the tap will not always be of a satisfactory tempera- ture, certainly not as hot as it might or should be. Should the whole apparatus be full of hot water so that the contents of the return pipe are nearly as hot as the flow, then, of course, the water drawn off will be of a satisfactory heat, but even this satisfaction would be short lived, for the instant water commences to 398 Warming Buildings by Hot Water. flow from the tap a corresponding volume of cold water enters the tank and quickly finds its way down the return pipe. An observance of this action of water proceeding from all directions to an open tap has led to the rising main of the cylinder system being returned and connected into the cylinder at a high point (as already explained), so that although the water makes its way up both pipes when a tap is turned on, yet as both proceed from the upper part of the cylinder no ill result whatever ensues. It was but a short time ago, and is very often now, the practice to return the rising main into the bottom of the cylinder or into the primary return, and many an apparatus has been cured of its inefficiency or been greatly improved by the mere alteration of this detail. The discussion of this particular action may not strike every one as being worthy of the importance that is being attached to it, but in practice it will be found that there is no effect which requires to be so continually under consideration when a problem in this work presents itself, and a knowledge of it is of the utmost value in a practical sense. It should be mentioned that the question of the friction or resistance that water experiences in flowing through pipes has not been overlooked, but it makes such a trifling difference to this particular subject that it is scarcely worth consideration ; yet, of course, if a tap were so situated that in one direction the water had only to flow a few feet, and in the other direc- tion a hundred feet, a marked difference would be noted, but so great an inequality seldom occurs. Another question intimately connected with this subject is whether the cold-supply service of the cylinder system could by any means be shortened by taking it into the secondary return or elsewhere, and the study of the results made visible in a glass apparatus has gone far towards settling the question. There has always been the objection of having to provide three pipes (rising main, return, and cold supply) in a com- plete cylinder apparatus, against the customary two of the Modified Cylinder Apparatus. 399 Fig. 237. m tank system, and this has led to various attempts being made to make one pipe answer the double purpose of secondary return and cold supply to the cylinder, but the majority of these attempts have been failures, or else so limited in their success as to be held in suspicion as unreliable. If we take the cold supply direct into the secondary re- turn, as Fig. 237, we shall have the worst possible results, especially with the taps at the top of the house, as immediately the taps are opened, a flow of cold water will set in direct from the cistern to the tap, as indicated by the arrows, and in this instance the friction element will be against the good results, as considerably less resistance of this character will be felt by the water that passes, as just explained, than by the pro- portion of the water that comes up the rising main, as this latter quantity has to pass right down the house and through the cylinder before it reaches the tap. An attempt was made to prevent the cold water passing to the tap by putting a deep dip in the pipe where marked * on the illustration, but this had no good effect ; in fact, the suggestion was somewhat absurd. The only means at present known of overcoming the diffi- culty that is worthy of recommendation, is to insert a " stop- back" valve in the circulation. These valves are made expressly to regulate a flow of water so that it may travel freely in one direction, but should it from any cause attempt to travel the opposite way it is instantly checked. This valve is by no means a modern idea, as it is used in various forms for different purposes, particularly in sewage work, &c., but its application to hot- water work is somewhat recent and by no means general yet. 400 Warming Buildings by Hot Water. Fig. 238 shows in section a valve of this sort, of simple construction, and the only particular care needed in its manu- facture is to have the flap A loosely hinged or jointed. In action the flow of water in one direction lifts the flap readily, but in the other direction it tends to close the flap tight. (The Fig. 238. Fig. 239. ^ flap shuts on to a turned surface so that it is nearly water-tight.) In fixing one of these valves it should be placed anywhere in a horizontal position between the point where the cold supply enters the return pipe and the point where the return is branched from the rising main, as Fig. 239, so that when the water is circulating it passes the valve, as indicated by the arrows, but when a tap is opened the valve is closed by the approach of the cold water from the direction of the cold-water cistern, and the whole of the water drawn has, perforce, to come up the rising main from the cylinder, while the corre- sponding volume of cold water passes down the secondary return. This arrangement answers very well, and under ordinary circumstances is reliable, as these valves have had a fair trial and no failures have been recorded ; they have the advantage, too, of causing little trouble should they get out of order ; as, supposing the valve got stuck shut, it would only convert the apparatus into one that has a single rising main not returned, and, provided a " connector " is inserted next to the valve, it could be easily taken out for inspection if needed. There are The Cylinder System. 401 three of these valves that have been in constant use and under the writer's notice the last four years, and none of these have ever required the least attention, for the only thing that could very well interfere with their free working is " fur," which, however, shows itself but little up in this high position ; and the constant flapping of the valve (for it keeps up a perpetual movement while the water is circulating) prevents its becom- ing fixed from this cause. When the secondary return is made to answer this two- fold purpose, it should not be connected high up in the cylinder, but near or into the bottom as a cold supply. It has been shown in some of the preceding illustrations that the primary flow pipe from the boiler is connected into the cylinder about 9 inches up, and that there is a piece of pipe (attached by an elbow) carried up inside, so that this flow really terminates about half the way up, as Fig. 240. This may Fig. 240. Fig. 241. appear to many to be rather an unnecessary and peculiar arrangement, which it really is, as the same purpose will be attained by letting the flow enter the side of the cylinder half the way up, and so make the stand-pipe inside unnecessary, as Fig. 241. The cost of fitting in either instance is about the same, but by the latter method a benefit is experienced by lessened trouble, as should the cylinder have a removable top and no 2 D 402 Warming Buildings by Hot Water. Fig. 242. man-lid, it will be found a most difficult task to attach the elbow and pipe inside, particularly if the cylinder is a high one. It matters not where a cylinder is purchased, if flanges for flow and return are ordered they will be put both within 9 inches of the bottom. Yet the poorest of hot-water fitters know that a primary flow pipe should always terminate at least half way up a reservoir of either description. Therefore, if care is taken to order sufficient flanges to be affixed to the cylinder in their proper places, a saving in cost may be effected also, as there is then no need for a man-lid or removable top, and this makes an average difference of about Ss. net (in the price of the reservoir), an economy worth practising for the little trouble it entails. There can occasionally be found an apparatus with the cylinder connected-up, as at Fig. 242, a method that can by no means be condemned, for it answers a useful purpose in giving hot water in the upper part of the apparatus a little quicker after first lighting the fire, as there is (as will be seen) a clear way for some of the water to circulate from the primary to the secondary flow with- out passing through the cylinder. In practice it is found that by this method one-half passes each way, but, of course, the half that passes into the cylinder loses its heat almost instantly until the apparatus (or upper part of the cylinder) is charged with hot water, consequently water of a high temperature will be obtained in the upper pipes quicker by this arrangement, but it will only be in small quantity. Occasionally advocates for carrying the primary flow pipe direct from the boiler to the highest point in the house (con- stituting it both primary and secondary flow) and having the return pipes connected into the cylinder only, as Fig. 243, are to be met with. This is a practice that should only be resorted The Cylinder System. 403 to on special occasions, as we have to bear in mind that the store of hot water in the cylinder is not added to, except by the pipe which has been all round the house, and probably lost the major portion of its heat. By this means, however, hot water is obtained at the taps very quickly, though it is a late hour before there is any in storage of a high temperature ; but, as an instance of its successful application, might be mentioned the case of a large residence where trouble had always been experienced in Fig. 244. obtaining hot water at the bath in the early morning as the bath-room was situated a great distance from the kitchen (i 60 feet run of pipe), and a considerable time was needed with an ordinary kitchen-range boiler to get really hot water at this point, it having first to pass through the cylinder ; a change was therefore effected, as Fig. 243, and the trouble was at an end, as the hot water reached the bath-room in much less time, and, as the pipe was of great length, it held enough in itself for one bath without depending upon the reservoir ; but this successful instance must not be construed into a recom- mendation of the method described. Another arrangement of connecting-up the pipes to the cylinder and the boiler is as Fig. 244, known as "Dyer's system." With this apparatus we must content ourselves with 2 D 2 404 Warming Buildings by Hot Water. a description only, as it does not come within the province of these papers to discuss the merits or demerits of individual systems. It will be noticed that in this the primary flow has communication with the secondary flow, as already explained. The cold supply is carried down and connected into the cylinder at the bottom, and is continued and connected into the boiler at the bottom also, and the secondary return is con- nected into the cold supply at a low point as shown. A prevailing notion amongst the majority of hot-water fitters, particularly with some of the stubborn ones, who have been faithfully practising for years what they were taught in their boyhood, is that on no account must the Fig. 245. flow pipe descend anywhere in its course, nor must any circulating pipe descend below the boiler; nor must, in fact, any pipe take a course that is irregular with the ascent of the flow pipe and descent of the return, which has become traditional, and from which a departure would be i looked upon as an offence against all accepted principles. In theory, several of the best authorities agree that under what we may term common circum- stances a circulation can be effected about three- fourths the distance below the boiler that the circulation extends above it, as Fig. 245, and the result is arrived at as follows : First, it is necessary to impress upon the mind that the cir- culation of water is brought about by the fact that cold water is heavier than hot, not that hot water is lighter than cold. This is a distinction with a considerable difference, so far as it affects this argument, for it can be seen plainly that heated water has no inclination to rise unless it is lifted or pushed, so to speak by a superior force. If we take a vessel of warm water the con- tents will not rise out of it, but if we take an exactly equal quantity, by measure, of hot water and cold water, and place one in each pan of a pair of scales, we should then find that the pan The Cylinder System. 405 of hot water would rise for the simple reason that the superior gravity of the cold water caused it to do so. Now, in an ap- paratus as at Fig. 245, when heat is applied to the boiler its contents become rarefied, or lightened, and a circulation will set in as indicated by the arrows ; if, in a short time, we apply the hand to the pipe, we shall find that, starting from the top of the boiler, the pipe is of a less and less temperature as we pass round it towards the bottom of the boiler (in the direc- tion indicated by the arrows). The difference in temperature may be due to two causes, firstly, loss of heat by radiation from the pipes, which, of course, is greater the further we get from the starting-point, and, secondly, the boiler may not have had time to heat up the whole of the contents of the apparatus to boiling-point (for we cannot have a uniform heat everywhere in a circulating apparatus until this temperature is reached, which seldom happens), consequently this makes plain to us that the pipe which ascends from the bottom of the apparatus up into the boiler has the coldest and heaviest water in it, and this is the obstacle that more or less interferes with a good circulation being effected below a boiler. If the lower part of the apparatus extends a greater distance below the boiler than the upper part extends above it, we are given to understand that no circulation will take place, and although this is not strictly correct, it cannot be practically applied in h Fl S- 2 4 6 - hot-water supply work, and, what is more, it is but very rarely required. It very frequently hap- pens that a fitter would find it very convenient if he could make a dip in his flow (and return) pipe, as Fig. 246, for instance ; but, accord- ing to all accepted ideas, it would possibly ruin the apparatus, but this is not the case, although it might give a good deal of trouble. The trouble experienced in this instance is the diffi- culty in dislodging the air from the upper part of the service, 406 Warming Buildings by Hot Water. a a a, for it will be found that in such a place the air will remain with the greatest persistency, and to remove it effectually an air-cock would have to be provided for periodical use, as, although we may allow the air to escape when first charging the apparatus, it does not wholly overcome the difficulty, as there is always a certain amount of air carried into the pipes with the water, and this will collect at any such point and require removing regularly, which we cannot expect servants to do. If it was not for the collection of air at this point, there would be no objection whatever to dipping the flow pipe in the manner indicated, as it would be found that a dip of a few inches only would make no appreciable difference in the circulation. An instance of a descent in circulating pipes to which no objection can be raised is when it becomes desirable to carry a returned draw-off service close to the tap. It has been the general practice when returning draw-off services to connect the returned portion at the point where the pipe turns down to the tap, as Fig. 247, leaving some 6 or 8 feet of single pipe Fig. 247. Fig. 248. in which the water lies stagnant ; this in many instances is not very objectionable, but, should it be desired, the pipe may be returned from a point close to the tap, as Fig. 248, and the circulation under this arrangement will be very good ; or where the pipe rises to the tap, as Fig. 249, the circulation will be found quite perfect. In the case of a lavatory basin, it is always a satisfaction to find hot water issuing immediately a The Cylinder System. 407 tap is opened ; the majority of these have but small taps, and annoyance is always experienced here if any cold water has to be drawn off before the hot arrives. As a general rule, there is only one objection to dipping the circulating pipes (provided the dip is not a very deep one), which is, that it probably leaves some portion of the pipes, as at Fig. 249. Fig. 246, and the dislodgment of the confined air will give infinite trouble, and, on this account, any plan of carrying the pipes in irregular directions requires considerable thought before = being put in practice, for it must be borne in mind that a collection of air in pipes will quite impair the efficiency of the apparatus and bring about noises and erratic results. In a heating apparatus, air-cocks for releasing confined or collected air figure very prominently, as they require fairly regular use ; but a heating system is commonly under the care of some one who has a knowledge of the air-cocks and their use, which cannot be looked for from the maidservants in an ordinary residence. Attention may here be drawn to a feature in the cylinder system which has not been mentioned before, but which is of considerable importance in rendering general good results. This is the insertion of a stop-cock in the secondary return, which should be closed at night to stop the circulation and so retain the store of warm water in the cylinder (which is usually in a warm position), and which can then be relied upon to provide a tepid bath before the fire is lighted in the morning. If the upper circulation is not stopped, we have the water travelling around the house dissipating its heat in all directions, to no purpose, as the circulation will not cease of its own accord until the water is cold. The best position for this tap is in the kitchen or some- where where it can be easily used, as Fig. 250 ; no harm can 408 Warming Buildings by Hot Water. ensue, as, should it be left closed, it only converts the secondary flow into an ordinary single-rising main, and the effect is that a quantity of cold water would have to be drawn before hot Fig. 250. Fig. 251. was obtained in the morning. If the cock has to be put near a ceiling it can have a cross-key with cords or chains, as Fig. 251. COILS AND COIL SERVICES. The attachment of a small quantity of hot-water pipes or a coil or radiator to a supply apparatus is much in vogue, but it is really not a practice that can be recommended very strongly unless special circumstances render it necessary. In the first place, a coil service and a supply service for draw-off purposes are directly at variance with each other in the objects that they are intended to attain. With the former the sole aim and purpose is to radiate, dissipate, and transfer the heat from the water to the air, whereas with the latter every effort is usually made to conserve the heat within the pipes, so that it may all be had with the water from the taps, and not to dif- fuse it with a proportionate reduction in the temperature of the water ; consequently, if a heating appliance of any descrip- tion is connected on to an existing apparatus, a reduction in the quantity or the temperature of the hot water must be anticipated. If we include such an appliance in a new Coil Services. 409 apparatus, we must, of course, put a boiler of a power more than sufficient for the taps only. It is very commonly desired to heat a small greenhouse or conservatory by one or two pipes heated from the kitchen boiler, and this arrangement is just as commonly carried into effect ; but it has a most fatal objection, which is that when the heat is most needed, in the early morning hours, the fire is out and the water cool. This objection is not so noticeable with a coil in the house, as the loss of heat brings about no serious harm and no particular inconvenience at night, when the occupants are at rest ; but, at the same time, if the coil was in connection with a stove that kept the fire going all night, a good deal of comfort 'would be felt from the warm tempera- ture in the early morning, when the cold is greatest and felt the most. If the kitchen range has a convertible open and close fire, this goes far towards overcoming the difficulty just referred to, as an open fire, if fed the last thing at night, will frequently remain burning until morning, and, although the combustion is slow, it keeps up the temperature very well, as but a small fire will do this when no water is being drawn off. In concluding the objections to the arrangement now under discussion, it should be mentioned that a boiler which is sufficiently powerful to give a good supply of hot water and satisfactorily work the heating appliance in winter will pro- bably prove a source of worry in the summer by furiously overdoing its work, as the coil would be then shut off and the demand for hot water considerably diminished. The oldest form of coil is that having box ends, as, in fact, many are made now, but the joints between the pipes and the box ends were made and secured by a rust, or a composi- tion joint which was a great source of trouble to make up. These rigid joints did not do very well, as the expansion and contraction brought about occasional leakages, and under the best of circumstances, the erection was abnormally ugly, requiring an expensive casing solely to hide it. This casing itself introduced two obstacles to the success of the coil, the 4 1 o Warming Buildings by Hot Water. Fig. 252. first being that it obstructed and absorbed a deal of heat ; and secondly, and worse, it made it difficult to keep the coil clean, and it is surprising what a preventive of heat-radiation a coating of dust is, it being composed chiefly of poor con- ductors of heat (minute particles of wool, fibre, straw-like materials, and stone grit). More recently two or three forms of expansive joints (the packing medium being a rubber ring or collar) have come into use, and are a decided improvement, as, although costing a little more, the joint does not give way, and the labour of erection is reduced to a minimum. Fig. 252 ~~j (in section) is one of the best-known \ of the joints as applied to two I lengths of pipe. It will be noticed that the pipes may have perfectly plain ends, no sockets being needed ; and if the pipe ends are a little rough or irregular a good joint can still be made. Fig, 253 shows a coil made up with this joint connecting the pipes to the box ends. A more recent introduction, which is very suitable for houses, as no casing or other device for hiding it is necessary, Fig- 253. Fig. 254. is termed a "radiator" (Fig. 254). These are now being made in various designs and forms by different manufacturers, and as they can be coloured to match the surrounding decora- tions their appearance need not be objectionable. The majority of these radiators have the pipes in a vertical position, and an object retained in view by the manufacturers Coil Services. 4 1 1 is to give as large a heating surface as possible with the smallest quantity of water, so that they can be heated up quickly. Of course, they just as quickly grow cold when the fire is out, but this is not a serious matter in a residence where the kitchen fire is always alight from 7 a.m. to 10.30 p.m. The small quantity of water is an advantage, as a coil of ordinary pipes which holds so much water is like attaching a second reservoir to an apparatus, and it greatly imperils the efficiency of the boiler, and takes a great deal of time to heat. As a general rule, it may be considered that two medium sized radiators is as much as ever should be attached to a domestic supply apparatus ; to attach more than this will only be at the risk of rendering the supply of hot water at the taps inadequate in temperature, and it is only when a boiler is more powerful than is necessary for the supply of water drawn off that this can be done. There has been some controversy as to which gives the best results, a coil or radiator of vertical pipes, or of horizontal pipes. From experiments made it is found that the water will circulate through each at about the same speed, but with horizontal pipes there will be found a difference in tempera- ture between the top and bottom pipes, whereas with the vertical pipes the circulation is regular through all pipes, and it is quite the exception for one pipe to heat differently to the others, supposing no obstruction exists ; but it has to be pointed out that with vertical pipes, if air accumulates, pre- venting the pipes filling right up, the circulation will be checked, but at the same time this only indicates that the air- cock wants opening, which instantly remedies the trouble. A strong point in favour of vertical pipe coils is that they do not get coated with dust so quickly. There are various ways of connecting these appliances to the circulating pipes ; some on to the flow pipe only, some on to the return (the secondary return to a cylinder, not the return of a tank system), and some on to both flow and return. 4 1 2 Warming Buildings by Hot Water. To commence with the first arrangement, Fig. 255 illustrates a radiator connected to a flow pipe with a stop-cock beneath to divert the whole or part of the water through the coil as required ; if there Fig. 255. were no stop-cock at this point the apparatus would still heat, but not so rapidly ; and it is usually found desirable to have the cock so that it can be " set " to permit of the coil having a fair share of the circulation without inter- fering seriously with the house supply. The setting of the cock is necessary, as requirements differ so greatly, some people needing hot water at a later hour or in less quantity than others, or considering the coil of the most im- portance ; and in some instances the coil is closed off while the cylinder or tank is being heated up, and so on. If desired, the cock beneath can be quite closed, so that all the water has to pass through the coil, which will heat it up quickly, but it must not be expected to have hot water at the taps past the coil so quickly in the morning as when this tap is partially opened. In many cases, however, it can be done, and although the flow of water has to first rise up to the coil and then descend, the circulation will not be impaired. The stop- cocks at the sides of the coil are for wholly stopping off the cir- Fig. 256. = culation when not re- quired. Two stop-cocks are necessary if the coil is required to be quite cold, or if the coil is provided with a tap to empty it and prevent its rusting when not in use. It will be noticed that the arrangement just Coil Services. 413 explained introduces an objectionable feature, viz. stop-cocks in the flow pipe. Sometimes it can be arranged, as at Fig. 256, by which a little better results are obtained, as the flow pipe has not to Fig. 257. Fig. 258. 1 HI 1 !lji)l ^ t 1 -> J Fig. 259. descend ; but the gain is so slight that it is not worth while going to great trouble to effect it. When it is desired to connect the coil with both flow and return, it is done in a similar way to a returned draw-off service, as at Fig. 257 or Fig. 258, with stop-cocks, as shown, and this arrangement has the advan- tage of having no cocks in the primary flow or return services. If a coil is attached to the secondary return of a cylinder apparatus, it can be arranged as at Fig. 259, but in this case the cocks can be adjusted to allow the whole of the current through the coil, supposing there are no draw-off taps past it i. e. be- tween the coil and the cylinder, at E, for instance. It is usually found that if two stop-cocks are not provided for shutting off the coil (one in the pipe to it, and one in the pipe from it) the coil will not remain quite cold, and although its temperature will not be high, the warmth is usually objected Warming Buildings by Hot Water. to in the hot summer months, when the least artificial heat is considered intolerable. It is found in the majority of cases that one stop-cock, although closed, does not wholly prevent a feeble circulation setting in up the open pipe, although this is generally aggravated by the stop-cock being placed in the wrong position. If the cock is placed in the pipe that leaves the ooil, as shown at Fig. 257, the coil will not heat, except to a trifling extent, as we have to remember that, although a slow circulation will set in up a single pipe, it is next to impossible for it to take place in a directly descending one. The radiators referred to are generally supplied by the makers completely fitted, so that the connection of flow and return pipes is all that is needed. This makes an agreeable improvement upon the old pattern coils, which had to have all the pipes fitted and jointed on the premises. Of course, this convenience is paid for in the increased cost of radiators over plain coils. An example of a case in which coils were attached to a supply apparatus, and to which no objection could be raised, was in a residence only occupied during the summer months ; in this case the coils did not come into use during the occu- pation, so that the supply of water for domestic purposes was not interfered with, but when the house was left in charge of two servants all the winter very little hot water was required to be drawn off, and the coils had practically the full benefit of the fire. There was one coil placed in each of five bed- rooms for the purpose of keeping them aired, which they very effectually did. In an instance such as this, and whenever it is at all possible, it is best to take a distinct service to the coils, not in any way connected with the flow and return of the supply apparatus, as this in the majority of cases will save putting stop-cocks in the flow pipe to divert the current ; and if two distinct services are taken from the boiler they both start about equally, and should the coil service rob the supply then there is no objection to putting a stop-cock in this (coil) service, to check, adjust, or stop the circulation in this direction. If a distinct flow and return is not practicable, Coil Services. perhaps the flow pipe can be so run, and the return branched into the other return, but in either case it is desirable to have stop-cocks in both pipes to totally prevent circulation, and by this means the coils and coil services can be emptied (by a cock provided for the purpose) in the summer months, to save the extensive rusting that would go on. There remains to be mentioned two small heating appli- ances that can, without any objection, be attached to a supply apparatus, as they need but very little boiler power to operate them, and they are articles of great utility in many instances. The first is a coil for heating a linen-closet (or, in other words, airing linen in a cupboard or closet), which is usually made up of J or I -inch ordinary wrought pipe, as Fig. 260, and six Fig. 260. Fig. 261. or eight pipes, 3 feet long, are sufficient for a large-sized cup- board, say 9 feet high, 6 feet broad, and 4 feet deep. This coil does not particularly need any stop-cocks, as it is generally used all the year round. The other appliance to be mentioned is a towel-rail made of tube (decorated in colours or nickel-plated), as Fig. 261. This serves the purpose of drying and airing towels, and if it is severe weather the warmth both to the towels and in the dressing or bath room is agreeable. This does not need stop- cocks, unless desired. One very essential feature in any description of coil or radiator is an air- cock or tube for giving free escape to the air 4i 6 Warming Buildings by Hot Water. with which the apparatus is charged before it is filled with water, and also to discharge the air that is perpetually accu- mulating in every description of hot-water apparatus. These air-vents require to be fixed at the highest point on every coil, as air being so much lighter than water is always to be found in the extreme highest positions. The objection urged against an air-cock is, that it wants regular attention (every few days at the least) which makes it unsuited for domestic purposes, and the remedy for this is to have an air-pipe, which, being open at the end, gives free dis- charge to the air as fast as it accumulates, and requires no attention ; but an air-pipe is not always convenient, as, if there is a coil situated on the ground-floor, and the general apparatus terminates at the top of the house, then the air-pipe must be carried up to the top also, or it will overflow ; it is, in fact, a secondary expansion pipe. If air-pipes are used, they require to be just as many as air-cocks ; one air-pipe may be branched into another, but on no account must an air-pipe descend anywhere ; in fact they should not be carried horizontally, but ascending in a greater or less degree every- where from beginning to end. If a single coil is attached to a supply apparatus upon the tank principle it can either be connected to the flow pipe wholly or to the flow and return, as already explained ; but with an apparatus upon the cylinder system we are better situated as regards this, as we can connect it to the flow (secondary), or flow and return (secondary), or to the return only (secondary) ; this latter arrangement being the best by far, and which is not applicable with the tank system, as in this latter case the return takes a great time in getting hot, and when it is so it is continually being cooled down whenever a tap is opened and cold water enters the tank. In connecting a coil to the secondary return of a cylinder apparatus we gain an advantage in only using water that has practically done its work, it having passed all the draw-off ser- vices and only having to pass through the coil on its way back into the cylinder ; this is worth every consideration, as if a hot- Coil Services. 417 water apparatus is designed to supply hot water there should be no obstacles or impediments placed in the way of its doing the work thoroughly, and to place a coil between two draw-off services means, as a matter of course, that the service nearest the boiler will have hot water some time before the one the further side, and if this one on the further side is of the least importance the coil will prove a source of annoyance to this extent. If the coil is placed in the return, the whole of the return water (which in a cylinder apparatus is very hot) can be made to pass through it, but a means of cutting it out must be provided for the hot weather. In many of our suburban residences, it occurs that the kitchen is on the same floor as the entrance hall, and it is desired to place a radiator in this hall (one of the most efficient places for such a thing) with a view to warm some of the cold air that is perpetually pouring in here. A difficulty arises in the fact that if we place the radiator on the floor it will be below the boiler, a difficulty commonly supposed to be insurmountable, but such is not exactly the case, for we have Fig. 262. already shown that in the usual way a pipe may descend (dip) and ascend to a certain extent, and it is so in this case. It is not necessary to deal with the theory that supports this suggestion here ; the subject is fully treated in the chapter devoted to Circulation, pages 28 to 46, and also in 2 E 4i 8 Warming Buildings by Hot Water. Chapter IV. page 60. In practice it will be found that this arrangement is permissible, and will give fairly good results, sufficient to prevent its being deemed a non-success. It is necessary, to effect this, that the general apparatus Fig. 26^. extend up two or three floors, as usual, in which case it may be connected up as at Fig. 262 or Fig. 263, illustrating the cylinder and tank systems respectively. FAULTS AND SOURCES OF ANNOYANCE. To enumerate all the faults that may meet even a single individual's experience would occupy a great deal of space, but there are some of a very common character that it may be profitable to call attention to and describe. One is the con- nection of a draw-off service (or services) to the return pipe instead of the flow. This, although of frequent occurrence, can only be the work of an utterly ignorant or careless man, or one who has been accustomed to heating work in which the return pipe has very commonly all the services connected to it. This fault is usually recognised by one tap yielding water of a very different temperature to the others, but if all taps should be Faults. 419 from the return-pipe a difficulty may be experienced in judging whether the boiler or other part of the apparatus is at fault, unless the pipes are all exposed so that the error in connexion is obvious. Another, and only too frequent, cause of failure is a boiler of insufficient power. This can usually be detected in a measure by the fact that hot water is only obtained some hours after the fire is lighted, or only some time after the early demand has temporarily ceased say, between breakfast and luncheon hour. There are great numbers of ranges con- demned on this account, as but few range-makers even now seem to comprehend that an efficient supply of hot water is as essential as efficient cooking facilities, and the most miser- able boilers are often provided with what otherwise may be first-class ranges. The only remedy is to introduce a good boot boiler, or an independent boiler if needed. Sometimes the work of a boiler is rendered next to futile by reason of the pipes being exposed to such an extent as to cause a serious loss of heat by radiation. This happens when the pipes are carried along cold galleries or stone corridors, or if they are carried in vertical casings which are not packed or filled with some poor conductor of heat (as has been already explained), or what, perhaps, is the most frequent cause of this trouble, the tank being situated and exposed in a roof where it is robbed of its heat as fast as it is possible to do so. Another frequent cause of trouble is omitting to terminate the return-pipe in the boiler at a lower point than the flow, although every care is exercised to terminate the flow at a higher point than the return in the tank. This arrangement is adopted by many, who profess that it gives equally good results as making the return lower than the flow in the boiler ; and, certainly, if the apparatus is once started right and kept going without cessation, no trouble would afterwards arise, but when starting with cold water in every part of the appa- ratus there is no knowing which pipe will act as the flow and which as the return, for as both openings are at a level, and as there is no influence brought into action to cause the first 2 E 2 420 Warming Buildings by Hot Water. particles of heated water to travel up one pipe in preference to the other, there will be no knowing which pipe will act as the flow or which as the return ; and, further than this, the pipe that acts the part of a flow one day will, possibly, be the return on the next, and would give rise to a complaint that although hot water could be had one day, the supply was bad another day ; and there is every likelihood of the servants being blamed for this, as it would be attributed to non-atten- tion to the fire or non-cleaning of the flues. The mere fact of one pipe standing higher than the other in the tank makes no difference whatever when starting an apparatus charged with cold water. The chief use and object of the flow pipe reaching a high position in the tank is to enable us to draw off the hot water without having the inflow- ing cold water mixed with it. Sometimes a fitter is unfortunate enough to lose his bear- ings, so to speak, and ends up his work by crossing his pipes, that is, connecting the flow pipe from the boiler into the tank as a return, and the return pipe Fig. 264. from the boiler into the tank as a flow ; this can only happen in a large and complicated apparatus ; and although the water will circulate very well there is the disadvantage of having the flow pipe proceeding from \ #* ** 1 the bottom of the tank, where the cold ^Jy supply enters ; and when a tap is opened we do not get the hottest ^ n B * B *$1~ water by many degrees, for the water /4V/' will flow as indicated by the arrows at '"'or' Fig. 264. This is usually easy of remedy by transferring the stand-pipe in the tank from one pipe to another. This could only happen with the tank system, and it will be noticed that some of the faults under discussion are distinctly peculiar to this system, while others apply to the cylinder principle. It frequently happens that, for the sake of economy, the Faults. 421 cold supply to a cylinder is branched from an existing house service, instead of bringing down a distinct cold supply service for the purpose. This is frequently a saving of expense, but it has two drawbacks, one of them of a rather objectionable nature. The first is, that supposing we open a cold tap and a hot tap at one and the same time, as we often do at a bath or lavatory, both taps will run at an annoyingly low speed (unless a high pressure exists) as both services are fed by one supply-pipe from the cistern ; whereas with an apparatus that has a distinct cold supply, as it should have, the water will issue from both taps at an equal force, as in this case each outlet has its own distinct supply from the house cistern. This objection would not be felt, of course, if the cold and hot taps were never opened together, or if the one cold house service was of unusually large size. The other and more objectionable feature with the one service pipe supplying the cylinder as well as the cold taps is, that if any of these latter are near the cylinder, warm water will be drawn (unless a stop-back valve is provided). We have already explained that a very long draw-off service may be looked upon as a fault by reason of the waste of water it entails, but an instance once came to notice in which this practice caused sufficient trouble to amount to a complete failure. In this case an apparatus existed upon the tank system, with the reservoir at the top of the building as usual, and an attempt to gain the safety of the cylinder system was made by taking away all the draw-off services from the flow pipe and substituting a single draw-off service taken from the top of the tank and carried down the house to the different places where hot water was required, as Fig. 265, so that this single service was about 1 20 feet long in all. The house being a high one, the waste occasioned neutralised the efforts of the boiler. On new buildings a method is largely practised of running pipes on the walls before they are plastered, the plaster after- wards being laid over them. This has certainly two good features, one being that the pipes present no unsightly 422 Warming Buildings by Hot Water. Fig. 265. Ik T/fNt T U appearance, and the plaster and brickwork prevent to a great extent loss of heat by radiation ; but immediately the pipes require exposing for any purpose whatever a great expense becomes necessary, as it must impair the decorations, which may be costly. While the apparatus is working satisfactorily, it matters not whether the pipes are in view or hidden, but there are so many purposes for which the pipes require inspecting that trouble of a more or less serious character must arise at some time with pipes that lie beneath or in the plaster. Closely allied to this is the trouble occasioned by omitting to put " connectors " (union pieces) into the service-pipes at convenient points, so that when a pipe requires disconnecting at any particular place it may be necessary to take the pipes down for some distance, or else cut the pipe. This is a frequent source of trouble, and it often retaliates on the workman himself, as should he leave a leak to pick up (i.e. rust up), and the leakage refuses to remedy itself in this manner, then the workman has to return to disconnect and reconnect his pipes. This unworkmanlike practice of leaving leaks to remedy themselves is only too prevalent, for workmen are apt to leave leaks of too serious a nature with the hopes of their stopping of their own accord, and this induces a client to think that bad workmanship may have been introduced into the whole undertaking. A leak that only permits of one drop of water falling, say every ten minutes, will remedy itself (in plain iron pipe) very soon by the mere oxidation of the metal, and the joint will be as good after this has taken place as any perfectly made one ; but it is much better to remedy all leaks in a Faults. 423 workmanlike way, as otherwise it is apt to lead to carelessness in this particular direction. It is possible for great trouble and annoyance to arise from a very trifling cause. As an instance, we may mention a piece of loose material in the pipes. This may arise from the workman omitting to look through his pipes the last thing before using them, or it is usual for workmen, when leaving an unfinished job at night, to stop up the open ends of their pipes with a plug of hemp or other such material, which, if not carefully removed, may leave sufficient in the pipe to give the greatest trouble imaginable. There is no fault so difficult to locate and remedy as that of what we may call a " floating obstacle," and it is a fault that may not show itself except at irregular intervals. Sometimes a stoppage will occur by a fall of " fur," which will collect at one of the angles ; this rarely occurs if the pipes are not interfered with, but if old pipes are being altered or worked upon in any way, it is one of the most common results to expect, as the jar of the tools and the hammering so often necessary in loosening old sockets, also loosens the incrusted deposit as a matter of course. The most common place for the loosened matter to collect is just by the taps, as the rapid passage of the water carries it to this point, and after working on old pipes in a hard-water district one or more of the old taps have nearly always to be removed to clear the pipe. When noises are heard in the pipes of a hot-water supply apparatus they may arise from various causes, many of which are peculiar to new work and of which we have already spoken. In old work they are nearly always attributable to furred pipes, which, when sufficiently obstructed, prevent a free escape of steam, which, consequently, has to attain sufficient strength to force its way out with more or less violence ac- cording to the resistance it experiences. When the pipes are clear the rapid circulation of the water carries the steam with it to the point where it can escape easily, i.e. to the expansion-pipe, but when the pipes 424 Warming Buildings by Hot Water. are closed the circulation is retarded, and the steam requires to make its exit faster than the water can convey it. This trouble is always conspicuous by its gradual growth, but when professional assistance is called in, it is, of course, usually at its height, as the occupiers of the building nearly always allow it to go on until the noises are positively alarm- ing, when it is necessary to take down the furred portion of the pipes and replace them with new. In almost every in- stance the pipes nearest the boiler will be found in the worst condition. ACCIDENTS AND SOURCES OF DANGER. An apparatus of the kind under discussion may be said to be perfectly safe in a general way, but like everything else it is subject to accidental circumstances, which in this instance are often sources of real danger. The element of danger is steam, but this is quite harmless if it is not confined, and has free exit and escape. The expansion-pipe is provided expressly to ensure safety, but if it becomes stopped by any means, its safety is instantly disposed of ; but the stoppage of the expansion-pipe only will not usually bring about an explosion, as before this can occur the pressure exerted will relieve itself by way of the cold supply service, supposing this pipe to be clear, and, in fact, if there is any possible way for the steam to escape by the exertion of pressure, it will go this way before there is any likelihood of the boiler bursting, as we must remember that the boiler and pipes, &c., are of a strength that requires a very great power to bring about their rupture. It is on this account that such accidents are so usually fatal to life, as when an explosion does occur, the force, which is of a rending nature, is most destructive. We may sum up the causes of accidents, by explosion at the boiler, as follows : I. Frost. This is the general cause of such accidents, and it is really wonderful that the number is so very small from this cause. In the first place, some portion of the cold supply Sources of Danger. 425 service to the cylinder is generally in the coldest place imaginable, such as the roof or a room just under the roof, and it follows, as a matter of course, that the expansion pipe is terminated in a similar position. Now, here we have the only two open pipes of the apparatus, with their extremities in a position most favourable for their being stopped by frost ; we may take it for granted that in a simple form of apparatus, the contents of the reservoir will be brought down to a low temperature in four or five hours after the fire is extinguished at night, particularly in severe weather, and this leaves two or three hours (the coldest of the twenty-four) for the pipes to become frozen if it is possible for them to become so, and it must be remarked again that accidents of greater frequency from this cause ought almost to be expected. There is not the least doubt that many and many a kitchen fire has been lighted in happy ignorance when it has been almost suicidal to do so; but there are, fortunately, many small things unknowingly done by servants and others that tend to obviate danger. For instance, there is no danger until steam is formed, and under a very high pressure ; this can only happen if the boiler is a rapid heating one, and no water is drawn off. If we draw water we relieve the pressure, and, what is more, reduce the temperature probably, and the opening of the tap will most likely give indication that some- thing is wrong. Then another source of safety is present in the fact that there is every possibility of the ice in the expan- sion-pipe melting (by the warmed water in the apparatus) before any steam is generated. The conclusion we must arrive at in this matter is that all pipes in connection with a hot-water supply apparatus that are situated in cold positions, particularly in roofs, should be well covered with some poor conductor of heat, such as hair felt or any woollen material or other substance that will pre- vent loss of heat by radiation. Next in priority to frost as a source of danger is the practice of putting stop-cocks in the main (primary) flow and return pipes ; this practice has already been referred to fully, 426 Warming Buildings by Hot Water. and needs no further notice here, except to say that it should be condemned to the utmost of every one's power. Another possible cause of explosion is a shortness of, or exhausting, the water supply unknowingly ; we say unknow- ingly, as should the failure in supply be noticed, every one has sufficient sense to take some steps to avoid possible accidents. This cannot very well happen with the cylinder system of apparatus, and it cannot very well occur anyhow without the shortness of water becoming quickly apparent at the taps, but it was only quite recently that a serious accident from this cause was only escaped by the fortunate existence of a safety valve, as it appears the water had been drawn nearly all away overnight, and the fire had been lighted for some hours in the morning without any one noticing the want of water, so that what little remained had been evaporated, and when the daily supply of water came in, some portion of it did its best to flow into the red-hot boiler, with results that need no describing. The force exerted in this instance was so great that the safety valve did not merely open but had the upper portion twisted up like a piece of crumpled paper. The last source of danger there is to explain is " furred " pipes. This question has been practically exhausted in the previous papers, but it might be repeated that an accident from this cause, though possible, is highly improbable, as before any real danger need be feared the noises and violent shakings and vibrations must warn every one to give the matter attention promptly. SAFETY VALVES, ETC. There are at present but four kinds of safety valves made for range boilers, viz. spring, dead-weight, lever, and diaphragm. The spring valve shown in section at Fig. 266, is, perhaps, the one mostly used, owing chiefly to its occupying but little room ; it consists of an outer case A, a screw cap B, pin C, seating D, and a spiral spring. The seating is held in place by the spiral spring, which Safety Valves. 427 presses upon it at one end, and at the other end against the screw cap ; this is where the utility of the screw portion of the cap manifests itself, as by unscrewing the cap we slacken the pressure exerted by the spring, and by screwing the cap down the spring exerts a greater force. The seating has the under side of it covered with a special compound of a rubber character so as to easily effect a water- tight joint, and the outer casing is perforated to allow of the ultimate escape of the steam when the seating is lifted. When fixing these valves, and the apparatus is charged, it is usual to unscrew the screw-cap until the valve leaks, then screw it up again until the leakage ceases, and afterwards give it one extra turn to keep it quite sound under ordinary conditions. Undoubtedly, the proper place for a safety valve is in the boiler, but it is very desirable to have the valve in sight, and this precludes the idea of having it fixed directly into the boiler itself ; therefore, the next best arrangement is to have it fixed somewhere in sight, and connected directly with the boiler by a fair-sized pipe ; there is no great risk of this pipe becoming stopped, not even by fur, as the water does not circulate within it, and if it is taken from the top surface of the boiler, there is not a great likelihood of the opening to the pipe being " furred " up, unless the boiler is allowed to get into a very bad state indeed. There is an idea rather prevalent that as good a place as any for the safety valve is on the cylinder (of the cylinder system). No doubt the advocates of this method have strong arguments in favour of it ; but it must be borne in mind that cylinders never burst. It is the boiler that is the seat of danger, and where the pressure is exerted to the greatest extent ; and, what is more, some of the accidents are due solely to something that occurs between the boiler and the cylinder stop-cocks, for instance. It was said just now that cylinders never burst neither 428 Warming Buildings by Hot Water. do they ; they collapse, which is a very different thing, and which a safety valve would in no way obviate, as the valves in question are provided expressly to relieve a pressure that is exerted from the inside, whereas a cylinder collapses from an external cause viz. atmospheric pressure, and an inlet valve would be the proper thing to obviate this. The collapse of cylinders is of as great a rarity as the bursting of boilers, and it is brought about usually in this way: Supposing a cylinder for some reason is allowed to get empty, and a fire is still kept in the range (a most unlikely thing), if there is any water in the boiler this will boil, and the steam will, of course, enter the cylinder ; now it is well known that there is no better means of driving air out of any confined space than by injecting steam into it, and consequently while the steam is entering the cylinder in fair volume, very little air will remain there. While things are in this condition, if cold water is introduced the steam is condensed, and a vacuum is formed, when the pressure of the atmosphere crushes in the cylinder like cardboard. It takes but little calculation to arrive at the force exerted by the atmosphere, as we only have to find the number of square inches on the external surface of the container and mul- tiply by 15 to have the total pressure in Ibs. With a medium-sized cylinder this pressure would be about 1 5 tons. The next form of safety valve in general favour is the " dead-weight," as Fig. 267. The body of the valve is similar in form to the one last described, but the seating is held down by weights placed and bearing upon the central ^ ^ pin. This is a good valve, but unfortunately takes up a good deal of room, and is not of sightly appearance, otherwise it is to be recom- mended on the score of reliability. This valve is still more unsuited to place directly into a range boiler, but it can be connected by means of a pipe, as described with the last. After it is fixed sufficient weights are placed on to just pre- r ig. 267. n Safety Valves. 429 Fig. 268. FiV. 260. vent leakage, then an extra weight is added to keep it quite sound under ordinary conditions. Next in rotation comes the lever valve, as Fig. 268. This is similar in internal construction to the two preceding, but the pin which bears upon the seating is held down by a weighted lever above, as shown ; this is another reliable valve, but is even more cumbersome and unsightly than the dead- weight, consequently it is rarely seen affixed to range boilers, but it is a valve that must be familiar to every one, as it is much used on all sorts of steam boilers. It is a very safe valve. The last to be described is an arrangement by which an excessive pressure bursts a thin sheet of copper, thus releasing the undue strain. Fig. 269 illustrates this valve. As the thickness of the copper must be proportional to the pressure on the boiler, it is necessary when ordering these to state what pressure of water exists, or, in other words, how far the cold-water cistern is above the boiler, and the maker inserts a diaphragm of suitable strength or lightness. Should the valve come into opera- tion, it can easily be put in order again by the mere insertion of another diaphragm. Fusible plugs are, perhaps, the most in- genious form of safety valve ever introduced, but, owing to certain drawbacks, exceedingly difficult to overcome, they are not used as freely as they would otherwise deserve to be. A fusible plug, as its name implies, is a plug or piece of material arranged to be fitted in the boiler in such a manner that, although infusible at the temperature of boiling water (212, or thereabouts), it would immediately melt if the boiler was without water, and by its melting leave an aperture for the free escape of steam, should water afterwards flow in, and so prevent an explosion and disaster. These plugs are pieces of soft metal, usually a disc, enclosed 430 Warming Bmidings by Hot Water. in a brass or gun-metal socket/this socket being screwed inside the boiler (to prevent injury by the poker or stoking tools), and it is further made so that part of it is easily removable to replace the plug when it may require renewing. These plugs, however, can not only be used as an element of safety when danger from shortness of water arises, but, if properly made, will answer the purposes of a safety valve when any dangerous symptoms arise with a full boiler, in the following way : When a hot-water apparatus is working under normal conditions, with the expansion and cold-supply pipes open, it may be assumed that the water does not ever reach a higher temperature than 212, this being the boiling- point at sea-level, where the pressure of the atmosphere is 15 Ib. to the square inch. If by any means the two pipes just mentioned become tightly closed, the atmospheric pressure will not regulate the boiling and consequent temperature, and before we have an explosion it is probable the pressure exerted in the apparatus will be 100 Ibs. to the square inch, this pressure permitting the water to have a temperature of 330 (approximate). This fact is utilised by making the fusible plug of an alloy (bismuth, &c.) that will melt at, say 280 ; the superheated water will then effect its fusion and the approaching danger be obviated. This, however, as will be clearly understood, needs the plug to be most carefully made if it is to be relied upon. The great objection to the fusible plug, in the South of England, is the " fur " deposit from hard waters. If the plug gets even a thin coating of this material it must suffer, as the deposit being a low conductor of heat, the water is prevented from absorbing the heat from the plug as fast as it receives it from the fire, and under these circumstances it will be found that the plug will more frequently fail when no danger is to be feared, than the reverse. With soft water there is no objection to be raised, but, notwithstanding this, fusible plugs have never gained favour, and are most commonly used as auxiliaries to ordinary valves, or to meet some special condition that may exist. Low-pressiire Boilers. 431 LOW-PRESSURE BOILERS, ALSO FITTING HIGH-PRESSURE BOILERS FOR TEMPORARY LOW-PRESSURE WORK. Boilers that have to supply water upon or below their own level only are commonly designated " low-pressure " boilers in contradistinction to those that are called high-pressure and have to supply water to the floors above. These boilers partake of infinite variety in shape, and they are constructed of a great variety of materials, as not only can we have them of welded wrought iron and copper, but also in cast iron and galvanised wrought sheet. Cooking ranges that have but one oven are usually fitted with a boiler at the opposite side of the fire, this boiler being generally of cast iron, having an open top with a loose cover, and being of the shape and size that the manufacturer con- siders most suitable for the purpose to which it is adapted. Of all materials common cast iron is the most unreliable, as nearly every one knows, owing to its liability to crack if suddenly or unequally cooled at any time ; the next best material is galvanised sheet iron, but this has a disadvantage in its being apt to laminate, that is, peel or flake, from which it soon perishes, and although it is not likely to crack, its failure will occur almost as soon as the former material, although it will not be so sudden. A more reliable material is a good quality of soft cast iron, this material making ex- cellent boilers ; and range-makers who use this metal have but a small demand for new boilers, as only the greatest neglect will bring about a fracture. Next in lasting proper- ties is welded wrought iron ; this is given to lamination, although not to the extent of sheet iron, and, even if it were, its life would still be a long one, as they cannot very well be made of a less thickness of plate than \ inch. Last and highest in the scale of excellence is copper ; this is necessarily costly, but gives the best results, although if made of very thin sheet it will not do much better than some of the others. The materials that permit of general use, and which are 432 Warming Buildings by Hot Water. Fig. 270. generally satisfactory, may be said to be the good quality cast and the welded wrought irons. When any of these boilers require renewing, a most diffi- cult task commonly presents itself, as no means are provided for removal and replacement without dismantling the range, occasioning sometimes eight to twelve hours work more than there need be, and the cost is of course, proportionately increased, both in labour and material, whereas the work charged should never exceed a matter of shillings, if suitable provision is made. Every range-maker knows that new boilers are needed sometimes, and it is the most simple thing imaginable to make the provision, as, instead of having the boiler screwed on to the hot-plate itself, there should be a loose panel to which the boiler can be attached, so that by removing the tap (and the union, if it is connected to a self-filling apparatus) the boiler can be lifted right out, as Fig. 270. The best method of preserving the life of these boilers is to have a self-filling apparatus fitted up and attached to them, so that their being supplied with water is not dependent upon the attention of servants, for, even with the most careful, forget- fulness must sometimes occur ; and, if not forgotten, the boiler is not always kept quite full, which leaves the part which experiences the greatest heat, viz. one side at the top, without any water behind to protect it. In fitting up a self-filling apparatus, or when connecting an existing apparatus to a new range, there is a most serious error commonly perpetrated in not allowing the boiler to fill sufficiently ; it is quite the usual practice for workmen to regulate the ball-valve so that the boiler fills up within about 3 to 4 inches of the top, and this leaves totally unprotected the upper portion of the boiler where the flame and heat im- pinge with the greatest intensity, and the result is that a new IZI ffi Low-pressure Boilers. 433 boiler is needed much too soon. The average workman's argument in favour of this is that " room must be left for boiling," and further that the steam which rises from the water when it boils will serve to protect the metal the same as water. Both these arguments are quite wrong, as in the first place the difference in bulk between very cold and very hot water is only about one in sixteen, so that \ inch is sufficient room for expansion, but to allow for ebullition as well it is best to regulate the ball-valve so that the water fills up to from I inch to i^ inch of the top (when cold), this will be ample, as the water in these boilers never boils very furiously. Steam will not protect the iron, as, while it is at a high temperature, it is a gas without appreciable moisture. Fig. 271 shows (in sectional elevation) a boiler fitted with a self-filling apparatus in an ordinary approved manner, and the flame passing from the fire is also shown impinging directly upon the upper part of the boiler side, as just ex- plained, and where it is so necessary that there Fig- 271. should be water. One of the most com- mon complaints a range- maker has is of peculiar character, although an explanation will make it quite clear to any one ; yet strange to say, only a small minority of our range-fitters know the simple means of remedying the trouble. The complaint in question is that the " boiler won't heat," meaning, of course, that the water in the boiler does not get hot as it should do ; now, this complaint may be correctly stated in some instances, but as it occurs with the greatest frequency with quite new ranges, it is obvious that there is some special cause for it. A more accurate description of the fault will be found in the majority of cases to be "that there is hot water in the 2 F 434 Warming Buildings by Hot Water. boiler, but it will not flow out at the tap," and it is sometimes described in this way by the person who complains. It will be noticed in the preceding illustration that the cold-supply service is connected into the side of the boiler near the bottom, and this is strictly correct, but it will be noticed that the tap is also at the bottom of the boiler, generally within a very short distance of where the cold water enters. The action that takes place when a tap is opened is that the contents of the boiler nearest the bottom commence to flow out, and at the same instant cold water commences to flow in ; now, as the cold water is heavier than the hot that may be in the boiler, it will be found that a steady flow will set in from the cold-supply pipe to the tap across the bottom, hardly disturbing the heated water above, and unless remedied in the way about to be described there will be no means of getting the hot water out unless we stop the inflow of cold each time the tap is opened, or else ladle the water out at the top of the boiler. There is, fortunately, a very simple means of remedying this, as all we have to bear in mind is (as already explained on two or three occasions), that the hot water, whether there be much or little, will be found at the top of the container. Therefore with all boilers Fig- 272. Fig. 273. that are self-filling, the tap should be inserted within 3 or 4 inches of the top, when the range is first made ; or, with ranges already made, the diffi- culty can be overcome by attaching an elbow and short piece of pipe to the end of the tap, standing up inside the boiler, as shown at Fig. 272. The elbow and pipe simply require to be screwed on tightly ; these joints need not be perfectly water-tight, and it is the easiest remedy imaginable, except with f-inch cocks, as we cannot get iron elbows and pipe of this size. This tap *n j - 1 -.-JL. ._ _ J-T \i i ' ' / ' ' / & = ^A0 * Low Pressure Boilers. 435 needs an elbow specially made for the purpose, or a J inch one can be used by soldering it on to the back-nut of the cock as Fig. 273, or a piece of lead pipe, if properly secured, will answer. The stand-pipe should terminate at top, about 4 inches below the water-level, as we must allow for the water issuing from the tap in greater quantity than it comes from the ball- valve. When a range has two ovens and has a low-pressure boiler, this requires most usually to be fixed at the back of the fire occupying the same position as a high-pressure boiler would ; this boiler must of necessity be boot-shaped, as a tolerably large space must be allowed for ebullition, as the water in these boils so violently ; if a good space is not left, then the annoyance of boiling water being ejected from Fig. 274. the steam pipe is ex- perienced. Fig. 274 shows the usual method of con- necting up a low-pres- sure boot boiler. The cold supply is carried in near the bottom as usual, and the draw-off service is taken from about 4 or 5 inches below the water-line, so as to avoid draw- ing cold water until the hot is exhausted, as just explained. The ball-valve should be regulated so that the boiler fills within about 4 inches of the top, so as to leave ample room for any violent motion of the water; and there is no objection to this large space in this instance, as only the lower part of the boiler comes in contact with the fire. The real object of the large space is to permit a free escape of the steam above the water, as should any particles of water be thrown by their motion into the mouth of the escape pipe, the steam will, instantly eject them into the chimney, sometimes a pint of 2 F 2 436 Warming Buildings by Hot Water. Fig. 275. water at once. All pipes that are run behind ranges should be iron, never lead, as there are numerous enemies to this latter pipe, and should a leakage show itself the range has to be removed before a repair can be effected ; this also applies to ranges with side boilers, when it becomes necessary to carry a pipe round the back or beneath the range. It will be noticed in the drawing that there is a " set " or crank in the steam escape or expansion pipe. This answers a very useful purpose in preventing any small quantity of water from being ejected, as when the water (unless in quantity) is propelled up the steam pipe, this obstruction will prevent its free passage and escape into the chimney under ordinary circumstances. These boilers should be of welded wrought iron. Sometimes a low-pressure boiler is used for supplying > hot water above its own level by regulating the ball valve to a height that will allow of the water rising up within the expansion pipe, as Fig. 275. This will answer, cer- tainly, but if the boiler is a rapid heating one, a good deal of annoyance will be experienced by the steam forcing water out of the pipe, even if this pipe is carried to an unusual height ; or should the steam experience any diffi- culty in escaping, it will probably make its way through the cold -supply cistern, causing this to overflow. This arrange- ment cannot be recommended. It is better to have the water drawn from the level of the boiler, or else have a small tank and circulating pipes fitted up. The ball valve, which is an essential feature in the self- filling apparatus of a low-pressure boiler, is frequently a source Low-pressure Boilers. 437 of complaint ; for, as every practical man knows, a ball valve anything near perfection has not yet been made ; but perhaps of the different varieties those that are constructed upon an equilibrium principle give the best results. Ball-ttto&r are now losing favour, as they act so slowly in rilling a boiler. While the level of the water is low the cock admits an abundant supply, but as the level rises the supply decreases gradually, so that when the water is within I inch of its accustomed level the water is only dribbling in, and this slowness in filling gives every opportunity for the fire to injure the boiler plate, besides being objectionable in other ways. The fitting up of a high-pressure boiler before the circu- lating apparatus is erected, so that the boiler has to be used for low-pressure purposes temporarily, sometimes for a few months, is of common occurrence, and can usually be arranged without difficulty or great expense. This can be done in two or three ways, but the least expensive method Fi S- 2 ? 6 - costs the most to re- convert when the hot- water circulation is ready, and vice versa. The least expensive method is to fit in the high-pressure boiler and construct the flue to it at the back of the range, and then to carry a flow and return service from the 'boiler just through the chimney jamb (as Fig. 276) ; these two services being capped off until required for circula- tion. From the flow pipe is carried a steam escape pipe as shown, but the boiler is fed and drawn from in the same manner as a low-pressure boiler. The flue under the boiler requires to be stopped while it is used for low-pressure pur- 438 Warming Buildings by Hot Water. Fig. 277. poses; this is best done by a piece of fire-brick cut to shape, as it is easily removable, leaving the flue clear when needed. When the conversion is made, the flue is cleared as just explained, the flow and return services are uncapped and connected, the steam escape and cold-supply pipes are both stopped off, and the draw-off tap can be left as an emptying service if the tap has a loose key; it is then ready for use, provided the circulating appa- ratus is complete. Another method is to com- plete the apparatus from boiler to cylinder, but supplying the cylinder temporarily with a supply cistern, as Fig. 277. This is without doubt much the best arrangement, if the conversion is to be made after- wards, as when it is done the work is reduced to a minimum in fact, it is hardly neces- sary to put the fire out, as all that is needed is to complete the apparatus above the cylinder, the draw-off tap below answering for the emptying service. By this arrangement very little expense is incurred but what is necessary to the complete apparatus. In conclusion, let it be the ambition of every one to do this work really well. There is no branch of mechanics which will permit of careless labour so little as this, and workmen have an opportunity of displaying ability and discernment to a far greater extent than in many other trades. ( 439 ) CHAPTER XX. COMBUSTION ; ITS APPLICATION TO WARMING PURPOSES BY GRATES, &C. Stoves and grates Value of radiant heat Smoke Slow combustion, advantages and disadvantages Utility of the " Blower " to grates Dr. Arnott's principle and its unique value Fire-brick and poor heat- conducting materials Grate backs and other improvements Process of combustion Carbonic acid and oxide Bituminous fuels Products of perfect and imperfect combustion Carbon and hydro-carbon Soot. THE prevailing idea as regards the combustion of coal fuel, is that all introductions and improvements in grates, stoves, and fuel burning appliances, should tend to increase results with a given quantity of fuel, or in other words be more economical than preceding patterns in attaining the desired effect. This argument is very good in its application to mechanical requirements, and decidedly so with hot-water works, but it does not apply generally, that is to every purpose, if it did the open grate, even in its most approved form, would not exist. The process of combustion is rarely effected in a perfect manner with a bituminous fuel (ordinary coal) owing to the existence of the volatile matters in its composition which are loosened and released before the temperature is sufficiently high to ignite them. The combustion, however, is more perfect in any form of furnace or close stove than in an open grate. Yet supposing the combustion was carried on equally in both appliances, the results would be far less in the latter than in the former owing to several causes, chiefly that only radiant heat is obtained from the glowing coal, for the air is not heated ; and all flame is next to useless for radiating purposes, although it is of great value for contact work. This latter is readily ascertained from an ordinary gas flame. 440 Warming Buildings by Hot Water. With any form of boiler or stove it is possible (by its pro- per construction) to utilize nearly the whole of the heat evolved from the fire or at least all that is capable of useful effect, and the gases that ultimately pass into the chimney need only be of a comparatively low temperature. As a rule this is the result aimed at by all boiler-makers and most stove-makers. It might be roughly computed that an efficient hot-water apparatus, in which no waste of heat occurred from the mains, would heat, say, ten rooms in a residence with the fuel that would be consumed in four or five rooms with ordinary open grates ; or if the grates be of an approved modern type slow combustion, with the best form of fire box for effectiveness, we must take a little lower estimate, but still the hot-water ap- paratus would be decidedly the most economical. Hot water engineers urge other features in favour of their speciality as against open grates, such as less attention, &c., but their other chief point is equable temperature, heat projected towards the body from all sides, and not from one point only as with a grate, (this objection with the grate can only apply if the whole of the room has not attained its proper degree of warmth). This is always considered a very strong case for the hot- water engineer, but at present it is more than counterbalanced (in the public mind) by the advantages possessed by the open grate and which have not yet been referred to. Chief and foremost of these is the fact that wholly radiant heat is decidedly the most healthful and congenial to human life owing to the peculiar effect it has in passing through the air without raising its temperature* and in this it acts most naturally, for sun heat is received in the same way. It will always be found that the most agreeable sense of warmth is that which fully heats (and sometimes a little overheats) the body, but which leaves comparatively cold air to breathe, and the open grate fulfils this, particularly as it in itself constitutes an effective source of ventilation. But the average grate, * In hot water works, particularly when the pipes are not exposed, the heat is chiefly contributed by heating the air. Combustion. 441 although representing a desirable means of heat-distribution effects its purpose very imperfectly, so far as the combustion of fuel is concerned and the results obtained for the fuel consumed. If it were that this valuable feature did not exist with open fire places it is still possible they would survive, for a real difficulty would be experienced in discarding the many pleasant associations that are connected with the very ap- pearance of the fire ; its cheerfulness would be missed for a long time ; it is even a very common practice to have fires in living rooms that are heated by other means, but which means are checked sufficiently to prevent overheating when the fire in the room is alight. The material which goes to make flame, smoke, and soot deposit, is as every one knows, fuel in a new but wasted form and on this account it is rather surprising that coke is not more freely used in open grates as there are several features in its favour, the abatement of smoke not being the least. A coke fire carries quite as good an appearance as one of coal, for the latter fuel does not please the eye less when it is in a glowing coked condition without flame, in fact, it is generally at this time that the fire looks its best and it is decidedly at this time that the greatest heat is radiated, and coke fuel, if used in a proper form of grate, quickly assumes this desired state with- out the preliminary stages that coal has to go through. The difficulty that would be experienced in using coke for the ordinary grates or the modern "slow combustion" variety, would be in getting the coke up to a bright heat, as this fuel is not successful if put upon a low fire with no means of causing it to draw up quickly, and the difficulty would be even increased when first lighting the fire ; but the whole trouble can be so readily overcome by using a blower, a most desir- able adjunct to any grate ; for we at no time desire a grate to be a long time lighting or burning up.* * There are several grates made with blowers more or less a success mechanically, but this attachment should be more universal, whatever fuel be used. 442 Warming Buildings by Hot Water. This brings to notice the particular and a really pro- nounced objection to the majority of our modern " slow com- bustion " grates which are slow always, and when first lighted in the morning do little else but pour smoke into the chimney for some time, and the same thing happens whenever the grate receives fresh fuel in fair quantity. Speaking of " slow combustion " which is effected by decreasing the quantity of air that is allowed to pass through the fire * calls to notice the principle introduced into Dr. Arnott's grate. It is unnecessary to describe the grate it- self as it was somewhat complex, and on this account and the trouble of fixing, fell into disuse, but why the peculiar and valuable feature of the grate was lost sight of cannot be understood and it certainly shows a want of perception some- where. The peculiar feature referred to was the ability to keep the fire (of ordinary size) alight a great number of hours without attention, the construction of the grate being such that the fuel could be surrounded as if it were in a box with only the top open. The effect of this was not to extinguish the fire as might be supposed but to render it stagnant or stationary, that is to practically prevent ingress of air to cause combustion, yet not to permit the fire to go out. This result is quite possible, and practicable from a manu- facturer's point of view, as there is one maker adopting the method at this moment in an eminently successful way, yet valuable and appreciated as the principle is, this maker stands alone, for the manufacture of grates moves slowly so far as practical improvements are concerned.! In Dr. Arnott's * This is usually done by making the bottom of the fire of solid fire- brick (iron would not do, by reason of its rapid heat-conductive pro- perties), or else by placing a grating at bottom, and preventing air passing through it by closing tightly the front space between the bottom edge of the front bars and the hearth. This latter is the best, and generally recom- mended plan, as it permits of the accumulated ash being easily disposed of. t In the beautifying of grates and stoves the different makers show a praiseworthy interest ; but there is a deal of this ingenuity expended upon useless and almost barbarous appliances. The dog-grate is the worst contrivance of this sprt, yet, if stood into a nicely tiled opening, makes the most beautiful looking fire-place imaginable. Combustion. 443 grate the fuel could be kept alight from twelve to twenty hours without attention, and in the other one just referred to, the fire will with the greatest regularity keep alight fourteen hours without attention, the result being effected in the same way in each case, viz., by keeping the passage of air from passing not only through the bottom of the fire, but also having means provided to prevent air passing through the front of the fire, the top only of the fire being exposed and the fuel receiving from the top just sufficient air to keep the fire alive ; but com- bustion can hardly be said to go on, the fire appearing to be asleep. It will be seen that this is of particular advantage for very many purposes, such as for sleeping or invalids rooms (for the fire continues to give out a moderate heat) for any apartment that is left for three or four hours ; and with a grate like this there is no reason why any room should be allowed to get bitterly cold as they commonly are in the early morning. For the proper combustion of coal it is essential that the fire box be bounded on both sides and the back by fire-brick, and not by iron ; fire-brick is well adapted for the purpose but any material would do if it could be used in blocks or slabs and had a heat-conductive power equal to or lower than that of fire-brick. Nothing that conducts heat rapidly should ever be used, or the fire in contact with that part will be dead and unlike a fire and this occurs to a great extent even if the iron is backed up with brickwork. If it were possible to utilize silicate cotton * in this way it would be eminently suc- cessful and probably it would overcome the trouble that is constantly present with fire bricks, which so readily become fractured, for they are not in the least of a fibrous nature. The shape and position of the g fire bricks in a grate very greatly influence the results obtained in radiation of heat, and also, to some extent, the utilization or lessening of the other- wise wasted flame and smoke products. It is doubtful whether * The heat of an ordinary grate fire would be sufficient to fuse this material in its ordinary state. 444 Warming Buildings by Hot Water. the dog-grate * is more wasteful of heat (consequently fuel) than the old form of register grate which has a semi-circular opening immediately over the fire-box at the back, so that if a good fire is established the flame, and a decidedly major por- tion of the heat evolved, passes directly from the burning mass through this opening into the chimney. This result (with this grate) is entirely due to the opening being so close down to the fire, and to the back of the fire sloping backwards so that the products can have the freest possible escape into the chimney, and the heat received into the room is practically confined to that which may be emitted from the front of the fire only. Added to this the closeness of the chimney opening to the top of the fire causes a much higher speed of combustion than is needed,f and the closer the chimney opening is down to the fire the less opportunity there is for the utilization of gaseous products, and the radiant heat which is required in the apartment is to a great extent expended uselessly, as the apartment does not get the benefit of it. There is a great diversity of opinion as to the best shape of the back brick to an open fire grate. There is an agree- ment as to the effect that is required, which is to prevent the heated products and also the radiant heat from having a straight passage into the chimney, and this is effected by * Also commonly called a " fire basket." f As a rule, the speed of combustion in open fire grates is greatly in- fluenced by the distance between the fuel and the entrance to the chimney. If we use a blower which reaches right down to the front bars we practi- cally bring the chimney entrance down also, so that no air can pass into the flue without passing through the fire, and this effects the highest speed of combustion. If, on the other hand, we make the space between the fuel and the chimney opening two feet, which may be considered the maximum distance, we get the slowest speed of combustion (supposing the construction of the fire-box is of approved design), and, as we increase or decrease this space, so it will be found that a lower or higher speed of combustion is attained ; in other words, the greater opportunity we give for air to pass into the chimney without affecting the fire, the slower will be the speed of combustion. This means of reducing the rate of com- bustion has however to be resorted to with care, as unless a blower is provided some of the smoke may come into the room when the fire is first lighted, or when it is heavily fed with fuel. Combustion. 445 causing the back brick to lean forward and overhang the fire- box, so that nearly all heat and heated matters have to come in contact or be influenced by this projection. This projec- tion has another good effect in partially choking the entrance, or what is commonly called the throat, of the chimney. There is no gain whatever in allowing such a great volume of air to pass up the chimney more than is needed to convey the smoke, as this helps to cool the chimney and reduce its efficiency,* and although an open grate is looked upon as a powerful outlet ventilator its power should be somewhat limited, otherwise the draughts at the doors and window crevices, &c., will be objectionable. In reducing the throat of the chimney, care is needed, for although a small opening might suffice when the fire is bright and the products of combustion lessened (gases only, no smoke) this small outlet might not suffice if the fire was giving off smoke freely, and there is no necessity whatever for making the opening unreasonably small, as the chimney throat what- ever its size (within practical limits) makes no actual difference to the speed of combustion, unless, as before mentioned, there is a clear straight way from the fire thereinto and no device exists for preventing a free escape of heat and heated products. Figs. 278, 279, 280 and 281 show in side section several different modern backs, all designed with the object of bene- fiting by the heat evolved from the fire to the utmost possible extent, but it follows as a matter of course that as they vary so greatly in shape they must vary in results also. From experiments made and many results noted, the writer is of opinion that Fig. 281 is the most effective shape besides being free from some various little disadvantages in wearing properties that other shapes possess. The reason for speaking in favour of Fig. 281 is that to reap the fullest possible benefit of otherwise wasted heat, and * If the chimney is a fairly tall one, its efficiency could not so very readily be spoiled in this way, although this is the usual cause of dog- grates smoking. 446 Warming Buildings by Hot Water. heated products the back brick of a grate must be made to perform two offices, first, absorption of heat from flame con- Fig. 278. Fig. 279. Fig. 280. Fig. 281. tact, to the greatest possible extent. This can only be obtained by giving the greatest possible surface for the flame to impinge and act upon, this absorbed heat being radiated from the intensely heated fire brick into the room.* Secondly the projection of the brick causes the heat that is radiated from the top of the fire (which represents a valuable amount, the top being frequently the hottest surface) to be deflected into the room instead of passing into the chimney. It will be found from any simple experiment that a surface overhanging a bright fire will cause a very sensible and instantly noticeable increase of projected heat,f due to * Radiated heat proceeds in straight lines from the heated body ; thus an overhanging brick sends a really great amount of heat towards the floor, where it has a most useful effect, for the top of a room only too readily gets warm to the prejudice of the lower portion, the warmed air so quickly rising ; and we have to remember that the currents of cool air which proceed towards the fire and pass up the chimney, are more inclined to seek the floor than a higher level. t The common form of register grate, with a flap to close the opening just over the back of the fire, can be made to demonstrate this, by nearly closing the flap, so that it leans over towards the front ; a piece of cinder will hold it in this position for a short time. Combustion. 447 the radiant heat that would have been directed up the chimney, being turned from its course, or deflected, by the overhanging surface in question. This deflection takes place in practically the same way as light would be reflected, if the surface were a mirror. Fig. 282 shows these two particular ways in Fig. 282. which the overhanging brick utilizes radiant heat and heated products, the unbroken lines representing radiated heat from the hot fire-brick * and the dotted lines the deflected radiant heat from the fire. The brick should overhang the fire at least half way, or three- fourths if possible, the exact distance cannot be stipulated, but it may come as far as it can be got so long as a space of not less than from 2-J to 3j inches is left between the top front edge of the brick and the iron curtain or canopy in the front of the grate, this space extending the whole width of the fire-box. The size of this space or throat would of course vary with the size of the grate, but the principal care is to see that it is not made too small to admit of the smoke being carried off when the fire is first lighted or fed heavily with coal. As Fig. 281 and 282 show, the brick should continue to lean forward for a few inches above the lower edge of the curtain or canopy of the grate, and then it should turn back somewhat abruptly as shown. If the mass of fuel is thin, even if it be surrounded with fire brick, combustion does not take place at all perfectly ; on this account a grate fire has to be of a required thickness although the effect required only proceeds from the front and the top. At the same time a fire of an unusually large mass is a source of waste by the formation of carbonic oxide, as will be explained. * These back bricks get to a very high temperature, appearing quite clean when in use, as the heat is too great for soot to be deposited. 44 8 Warming Buildings by Hot Water. Combustion * is effected by the chemical union of oxygen and carbon, the oxygen being furnished by the air and the carbon by the fuel, the union being affected with the utmost rapidity, but not until the combustibles have reached a tolerably high temperature. If we use coke, charcoal, or anthracite coal we may look to get practically perfect com- bustion, as the gases which leave the fire will be found to be carbonic acid, nitrogen, and last, but not least, heat ; this latter, however, can hardly be called a product, it is more a result, and the nitrogen is neither, as it is simply the atmos- pheric air which passed into the fire but which has been robbed of its oxygen. As the air (which consists of an admixture of oxygen and nitrogen) enters the fire, the oxygen readily separates itself and unites with the carbon of the fuel for which it has an affinity and which we must suppose is in a glowing state, and the union of oxygen and carbon produces a gas known as carbonic acid (or carbonic di-oxide) the proportions being two atoms of oxygen to one of carbon (C O 2 ). This is the effect if the layer of fuel on the fire bars be fairly thin as is recom- mended in feeding boiler furnaces ; but if we get a large and thick mass of fuel the carbonic acid which is formed almost immediately it enters the fuel, undergoes a change (if it can- not leave the fire at once) and it takes up another atom of carbon and becomes carbonic oxide (C 2 O 2 or CO) which is a combustible gas and can be noticed burning with a rather beautiful blue flame on top of thick coke fires. The wasteful effect of carbonic oxide formation is due to its taking up or robbing the fire of carbon but evolving no heat when it burns and is re-converted into carbonic di-oxide in the air at the top of the fire. When oxygen combines with carbon, great heat is evolved, but when carbonic acid takes up carbon and when it parts with it again no useful effect is produced and the carbon is lost. In a thick coke fire we may consider that the combustion produces carbonic acid for about three to four inches from where the air enters, and from this point the con- * So far as it relates to this chapter. Combustion. 449 version into carbonic oxide is effected and continues to the top where it is consumed in union with the air it finds there and becomes CO 2 again as Fig. 283. Now combustion as perfect as that just explained cannot be effected with any bituminous coal, as the volatile compound, bitumen, contained in it, defeats this end. Bitumen is a substance we may say wholly composed of hydrogen and carbon, this compound not exist- ing in the coal in a separate form but being thoroughly incorporated in it, so that coal might almost be con- sidered as bitumen itself, but having an unusual proportion of carbon in it. The percentage of hydrocarbon in coal varies greatly, being very abundant in cannel and prac- tically absent in anthracites, the latter being very nearly pure carbon,* The effect of bitumen, which might be considered as solidified tar, is to bring about the results due to imperfect combustion such as smoke and smoky flame, by reason of its being so readily released, or distilled off by heat before the temperature is sufficient to ignite it. If this substance remained in combination with the coal until a fairly high temperature was reached, it would be ignited immediately it released itself and combustion would be perfect or nearly so* Many may have noticed this result in some hard coals, which flame, but produce a less per centage of soot, but this advan- tage is always accompanied by a difficulty in getting the fire to light.! The production of soot is reduced to an agreeable extent by using a blower to a grate, when the fire is first lighted or heavily charged with fuel, as by this means we much more * All coal fuels are more or less charged with impurities, sulphur in particular, and earthy salts, which go to make ash. t As a rule, a difficulty in lighting the coal is due to its less percentage of bitumen, but not always. 2 G 450 Warming Buildings by Hot Water. rapidly induce a high speed of combustion and an intense heat, a greater quantity of oxygen is caused to come within the area of combustion and in a few minutes a fire can be got bright and fairly free from smoke, when the blower can be removed. In the modern form of slow-combustion grate unprovided with means of hastening the lighting of the fuel the quantity of smoke poured into the chimney from a newly lighted fire is stupendous and, strange to say, the objection is quite recognised, as no good comes of the waste, and only loss of time, loss of heat and fouled chimneys result. Slow combus- tion has excellent qualities when a fire is bright, but at other times it is not only objectionable, but really amounts to an evil.* When hydrogen exists in a fuel we have another product of combustion, that is one more than we get by burning coke (see p. 448), as, of the two substances hydrogen and carbon which constitute bitumen, the latter (if consumed) goes to form carbonic acid or oxide, the same as with the carbon of coke, but the former released from the carbon undergoes com- bustion and combination with oxygen and forms water, in the proportion of two atoms of hydrogen to one of oxygen (H 2 O). This water leaves the fire in the form of a gas but quickly as- sumes the recognised appearance of water, as it becomes cooled. The presence of water in the products of combustion can be ascertained in a very few moments by holding any cold surface just over the burning materials when the water will be condensed upon it. This is most effectually tested by hold- ing a slab of iron or an earthenware tile or plate for a few seconds over a gas flame, when moisture will be found on the * If a group of houses be noticed any winter morning, all the chimneys which are in use will be seen to be smoking heavily for about one hour the first thing, after which time the smoke is greatly reduced, as the fires have become bright, and the material surrounding the fires become hot, then at intervals the smoking starts again as the fires are fed ; but all this smoke could be reduced to a comparatively trifling amount by the use of a blower. Chimneys should be kept clean when a blower is used, but at the same time the blower aids in this by reducing the smoke (soot). Combustion. 45 1 surface where the products of combustion have impinged upon it. The colder the surface the more quickly the moisture will appear. Hydrogen aids very materially in igniting the carbon and by its presence coal can be lighted readily from a few pieces of wood without a keen draught or superabundant supply of oxygen as we get when a blower is used ; but after this the presence of hydrogen is objectionable, not only on account of its volatile propensities, but from the fact that it produces water which carries such a deal of heat with it. If we use a damp fuel we reduce the resulting heat greatly as water has great capacity for heat and carries it off from the fire abundantly. The amount of heat absorbed by one pound of water to raise its temperature one degree would have the same effect upon about thirty pounds of mercury. 2 G 2 452 Warming Buildings by Hot Water. CHAPTER XXL CHIMNEYS. Draught in chimneys, cause and effect Causes of sluggish draught- Stoves v. grates Sizes and areas of chimneys Suggested sizes for horticultural works Residence chimneys A common, but little known cause of trouble Pipe chimneys Descending chimneys " Pilot " stoves. BEFORE speaking of the relative sizes of chimneys it is necessary to deal with the draught which entirely controls the successful purpose for which the chimney is erected. There is much similarity between the cause which promotes this upward current of air, and the cause of circulation in a hot-water apparatus, for both result from a difference in weight of two columns of fluid the column which has the greater weight compelling that which is of less specific gravity to rise and escape from its influence and force. In a perfectly new and cold chimney no draught whatever exists, but after the chimney has existed a little time a draught of slight strength will commonly manifest itself, due to the still air in the new building getting just a trifle higher temperature than the air outside,* and a difference in tem- perature of a fraction of a degree is sufficient to induce a fairly quick current ; by this reason it is a common experience to find a noticeable draught in the chimneys of a building where no fires have as yet been lighted. When a fire is lighted at the base of a new chimney it is not unusual for a little smoke to come out into the room as the weak draught alluded to is insufficient to take away any volume of gases and smoke, but this smoking does not usually last more * This cannot be said to apply during hot weather, when the circum- stances would be reversed. Chimneys. 453 than a few minutes and a rapid and efficient draught sets in permanently. If a chimney, which has had some use, is left unused for a time, it is really surprising how long a period a good and capable draught will keep up within it. This is not, how- ever, due to the difference in temperature within and outside the building, but is brought about by the heated brickwork of the chimney itself. When the heated air and products are passing up a chimney it follows that the surrounding brick- work absorbs heat and becomes of a good warmth, and if the fire is extinguished the brickwork will transfer sufficient heat to the air in contact with it to keep up the draught with very efficient strength for many days. A draught of sufficient speed to prevent smoke coming into the room when a fire is lighted will exist for quite a long period, this draught being almost wholly due to the heat given out by the brickwork, for this material parts with its heat very slowly. The efficiency of a chimney draught is increased by add- ing to the height of the chimney, also by raising the temperature of all air and gases entering it. If the air of the room and the gases within the chimney differ by, say, 50, there will be a difference in specific gravity of about one-tenth so that in a chimney 20 feet high under these circumstances we should have a force exerting itself to urge the contents of the chimney upwards, equal to the weight of a column of air 2 feet high, and this, it will be found, is sufficient to cause a draught that leaves nothing to be desired. With a chimney of even half this height we shall still have efficient results (surroundings being favourable), but as the majority of chimneys exceed 20 feet, there is never any trouble ex- perienced unless some influence is brought into play that counteracts the results here mentioned, or retards and prevents these results being ever attained. The efficiency of the average chimney is so actual, that the opposing influence has to be fairly strong to cause any real trouble. There has to be something radically wrong for a chimney to be unsuccessful in carrying away the products of combustion. 454 Warming Buildings by Hot Water. One rather prolific source of trouble in this respect is the admission of cold air into the chimney, that is air which has not passed through the fire nor even been near enough to it to be warmed. This can happen in one or two ways, a hole in the chimney being one, as it not only admits air that has a seriously cooling influence, but as we may suppose the hole would be at some point above the fire (not being likely to be below it) we shall find the fire will suffer from a want of draught for the chimney will be inclined to draw its air through this hole to the prejudice of that opening which is provided at the base for the smoke to be taken through from the fire. It is, however, rather unnecessary to speak further of this as everyone should know that no holes, passages, or even crevices should exist in a chimney, the only two recognised apertures being permissible, one at the fire place at bottom and the outlet at top. The common way by which cold air enters the chimney to such an extent as to prejudice or imperil its efficiency is by having the opening over and around the fire larger and out of proportion with the fire itself, as we get in a dog-grate, which is a fire basket set into an opening about three times larger than it ought to be. Unless the chimney is a very high and effective one the products of combustion will not be carried away at all satisfactorily. The best way of illustrating this is by describing a very old offender in this respect, the old pattern open kitchen range. These ranges when placed in an opening of ordinary height almost invariably smoke and they then require partially closing across the top by a blower to effect their cure, the good effect being brought about by the blower causing the air which enters the chimney to come under the influence of the fire and be warmed.* At no time do we get a good working draught with these ranges owing entirely to the great air space which exists just over the level of the fire, and the smoke and gases always seem to be acted upon by some depressing influences and seek every opportunity to ooze out into the * A blower extending a little way down the opening would oftentimes cure a dog-grate of smoking. Chimneys. 455 kitchen even with a good chimney, for a kitchen chimney is usually one of the highest, from 40 to 60 feet, if the residence be a fairly large one.* If we displace this open range and insert one of a modern closed character, what a different result. There is no need to make the slightest alteration to the chimney itself, yet we get a marvellous change in the nature of the draught. It no longer seems weary in its efforts to force the smoke or part of it up the chimney, but open all the dampers and the draught will cause a roaring noise in its mad race through the flues, drawing great tongues of flame around the ovens. The change is all the more wonderful when we remember that with the open range we merely wanted the smoke to go straight up into the chimney as it would be natural for it to do, but with the closed range we require the draught and products to first travel horizontally, then downwards, and then horizontally again, before ascending, and it does it more than willingly. The great difference in these two examples is due to there being an unreasonably free flow of cold air into the chimney in one case, and a total exclusion of cold air in the other ; of course any intermediate course can be adopted as desired. The trouble with the dog-grate, open range, or any form of fire place in which cold air has too free an ingress into the chimney, is not always experienced when once the fire has got hot and the chimney gained as much as possible in temperature (which, however, it is seriously prevented from doing by the never ceasing inflow of cold air). At first lighting, such stoves are of the greatest annoyance, but this could be minimised or perhaps entirely obviated if a deep blower were used at such times, as by excluding cold air for a * In many modern-built houses the kitchen is placed in a "back addition," a piece tacked on to the main building, and these back additions are not always as high as the main building, in which case the chimney is not only shorter than usual, but its top comes below its surroundings, and trouble must ensue. Why houses are built in this way and there are avast number is hard to conceive. Every chimney of a building should terminate well above the building ; but this will be referred to again. 456 Warming Buildings by Hot Water. time there is an opportunity for the chimney to get warmed, and further, the fire gets into a hot, possibly a glowing, condi- tion and the trouble is probably over. A blower does ex- cellent service with chimneys in which from some cause or other, the draught is sluggish, this sluggishness always being particularly objectionable when first lighting the fire. SIZE OF CHIMNEYS. In horticultural works there is no fixed rule as to the size a chimney should be, except that sort of rule which is generally called judgment There would be difficulty in compiling a table for the purpose, as the area of a chimney is regulated not only by the size of the boiler, but also by its own height. A high chimney inducing a keen draught need not be made of so large an area as a low one, as is most com- monly the case. Firstly, as to the height, it is only necessary that the mini- mum height be given, as there need be no fear of ill results in increasing the height if a stronger draught is wanted. If circumstances permit, it will be found best to exceed these heights, as they represent the actual minimum, which must only be expected to give just passable results. The object in showing the least height for these chimneys is that in horti- cultural works one of even moderate height can scarcely be tolerated. Unless the works be for a professional grower, the chimney is considered a most unsightly object indeed. Of course, where the houses and gardens are worked for profit only, almost everything is sacrificed for profitable results an almost opposite state of things to what exists in a gentle- man's private grounds. It is usually laid down that with horizontal boilers the chimney should always be of a height equal to the aggregate length of the flues which pass up and down the boilers, so that a saddle boiler 4 feet long, having the flues once up and down it, should have a chimney 8 feet in height This will suffice as a minimum. If the flue traversed the length of the boiler three times the chimney should be 12 feet high. Under Chimneys. 457 exceptional circumstances these heights could be reduced a trifle although it is unusual for 8 to 10 feet to be inadmissible. If the boiler be a large one, say 8 feet long, flued once up and down, it would be 'possible to work it with moderate efficiency with 12 or 14 feet of brick chimney, but this should only be attempted if the circumstances are really exceptional. With a vertical boiler which has flues carried vertically up and down it, a little larger allowance of chimney must be made, as the draught experiences more resistance or work in having to travel in a directly downward direction than it does in passing along a horizontal way ; in such a case twenty-five per cent, greater height of chimney should be given as the minimum.* In internal area it is more difficult to fix upon exact sizes, as we cannot show any relationship to the area of fire bars ; for it will be seen that the area of fire bars varies with the character of the boiler, and again a boiler used with coal fuel should have a larger sized chimney than one burning coke, as the fouling by soot reduces the actual area. For general purposes the following sizes will be found efficient : Area of Chimney square shape if possible. square inches. For a Trentham boiler, 8 or 10 ft. in length 400 For a saddle or similar shaped boiler, about 6 ft. long .. .. 320 ,, ,, about 4 ft. 6 in. long .. 250 ,, about 3 ft. long or smaller 200 Other boilers can be computed from this with sufficient accuracy, but if there is the least doubt let the error be towards making the chimney a little larger not smaller, as unless done intentionally, it would be unlikely that the chimney would be made too large.f * Boilers of a portable character, having no flues, can do with less chimney than any ; a short piece of pipe suffices if surroundings are favourable. f These remarks are based upon the supposition that the chimneys are of brickwork, this being usual with horticultural works. With pipe, chimneys other considerations occur which will be spoken of presently. 45 8 Warming Bidldings by Hot Water. The sizes just given will be found rather full, as they are based upon the chimney being low, in fact, of the minimum height just referred to. If the chimneys are carried higher these areas can be reduced. As an instance it may be sug- gested that if a chimney is carried up double the minimum height, the area might be reduced one-fourth below the approximate sizes just given. When the chimneys are low they require to be of good size, quite roomy, and on no account must that point where the boiler flues join the chim- ney be choked, or have abruptly square angles. In building works, the height of the chimney is rarely in- sufficient, as even with the attic fire places we generally get about 10 feet from the grate opening to the outlet at top, at the least, and this is sufficient as we have no horizontal passages for the smoke to pass along (nor should we get the smoke to travel in that way as the grates are open). At the same time we have to remember that with open grates a better working chimney is needed than with closed stoves or boilers ; but 10 feet is sufficient if the chimney terminates well above the building and the grate is of the recognised ordinary pattern. The internal area of the chimneys of grates in a residence varies from 9x9 9 X 14 to 14 x 14,* not a great difference as the size and character of the grates do not differ much. It is very odd to notice that although a builder in erecting a house always adheres to these sizes, correctly, if he has to fit up a stove or heating appliance with a chimney wholly or partly of iron pipe, he is nearly certain to use a pipe of too small a size. This is rather a sweeping assertion, but it is most notice- ably correct in quite the majority of instances for although, as just mentioned, the bricklayer puts a 14 X 14 or 14 x 9 inch chimney as being necessary for a fair sized grate, it is most unlikely that he would think of using a round iron pipe of 16 or 14 inch diameter. If this grate or stove had to be stood out and connected in this way, it is more probable that he would consider a 7 or 8 inch round pipe ample, these latter * Not usually larger in modern residences. Chimneys. 459 sizes having areas considerably less than he would give to the brick chimneys of attic grates.* Of course smoke-pipes are at any time objectionable- looking objects f and on this account are kept as small as possible to the prejudice of the stove, especially after soot has been deposited, which practically reduces the internal diameter. As a rule a smoke-pipe should never be less than 6 inches, the exceptions to this being small coke stoves such as the " Tortoise " and many other makes which will work with from 4 to 5 inch pipes, but for any stove burning about as much fuel as a dining-room grate the size should be nearer 7 or 8 inch, and if it be a grate, that is open, and not wholly closed, a 9 inch pipe should be used, this size being fully a third less than the brick chimney a builder would provide for it. There is no objection to making an iron smoke-pipe of a square section. The chief trouble experienced with the low chimneys of horticultural works is down draught due to their being lower than some surrounding object or objects, and the same remark applies to any residence chimney if it does not reach up as high as, and well above, the main building (as is often the case with the chimneys of what are called " back additions "). This trouble is usually difficult of cure, as the downward deflection of the wind from over the higher object is not always steady ; if it were, a revolving elbow or lobster back cowl on top of the chimney to turn its back to the wind would be a perfect remedy, and it is often tried with success. If, however, the downward current of air is influenced by other surroundings it will act like a wind maelstrom, or in some such irregular * The writer met with an instance in which a large hall stove (one that could be converted from a close stove to an open grate, and con- sequently needed a larger chimney than one wholly closed) failed to work, and it was found to be connected with the brick chimney by a 4-inch round pipe. When the workman was remonstrated with he actually excused himself as being unaware that the stove wanted a specially large pipe. The stove had a 9-inch circular nozzle on it. f These pipes will bear tasteful decoration in light water-colours, which last and keep very satisfactorily. 460 Warming Buildings by Hot Water. and conflicting way that the major portion of the wind-guards and patent tops may prove useless. With horticultural works * if this is the case resort is usually had to the most simple chimney top, a conical cap, and better attention is given to the fire when the wind is in an objectionable quarter. When a chimney of a building is troubled with down draught no half measures can be adopted as a small issue of smoke into a room causes injury to its contents and renders it uninhabitable. If the down-draught is of an intermittent character it is almost invariably caused by the chimney being insufficiently high, and the trouble is noticed when the wind is in some particular quarter, and a certain remedy can only be looked for in making the chimney higher. It is not sufficient that the chimney top be as high as the building, it must be higher than the highest ridge or trouble will ensue in almost every case ; it should generally be 6 feet higher, if possible. Occasionally a chimney of good height and correct in general details will smoke and entail a really great deal of trouble in ascertaining the cause, as nothing is visible from an ordinary inspection. Even in this case it may proceed from several causes, such as the displacement of a brick between it and another chimney, f It is usually very difficult to ascer- tain the exact position of such a fault, but the trouble itself can be discovered by placing a sack on the chimney top and watching if smoke still continues to go up the chimney. Or the trouble may proceed from a fissure caused by unequal settling down of the house ; but generally it will be found to be due to a deficiency of air ingress to the apartment where the fireplace is situated. This latter source of trouble is very common, yet little * Down draught does occasionally occur with these works, but usually the glass houses are well away from both high buildings and trees, and then the chimneys act normally. f It is a wonder this does not occur oftener. Chimneys are divided from one another by 4! inches of brickwork, and the sweeps' appliances must exert a great force when they encounter a bend in the chimney. Chimneys. 46 1 understood by the average workman for it is somewhat puzzling unless the actual phenomena connected with the action of a chimney are clearly understood. The trouble is occasioned by a want of provision for the proper inflow of air into the apartment where the fire is, and without which a proper flow of air (the draught) up a chimney cannot take place, as although a chimney acts excellently as an exhaust or outlet ventilator it has none of the properties of an exhaust pump, and its up current of air stops immediately the supply from which it maintains itself is stopped. In the usual way the supply of air to the fire is furnished by the crevices around the doors and windows, and it is when these are quite new and well fitted and kept closed that the trouble frequently shows itself, or when the tenant goes to great care in stopping all round these places with draught tubing, &c., to exclude draughts effectually. Of course if the door was left open the trouble could not occur but when fires are required open doors are generally vetoed.* The effect of this is to make the chimney act as if it were possible for some chimneys to be devoid of the cause which promotes a draught ; the smoke goes up most sluggishly (there being no agent to hasten and carry it) and some curls and oozes out into the room. Sometimes a very different effect is produced, as although the door by which the room is entered and the windows are tight closed, there may be com- munication between this room and another where there is another fireplace. In such a case (if there are no air entrances in that room) one chimney will help itself to the air it needs from the other, the strongest chimney having a fairly normal up- draught and the other having (while the doors are closed) a permanent down draught. A lighted taper held at this fireplace will show that this down-draught is supplying * The writer met with a failure of this sort, but for which a local man recommended a certain kind of top to the chimney, " never known to fail ; " but it did fail in a most pronounced way, yet the man must have had great faith in it, as from first to last he never went into the room where the troublesome fireplace was. 462 Warming Buildings by Hot Water. the room and the other fireplace with air, and carries with it a most strong and objectionable odour of soot, if the chimney has been used. It is needless to add that the down draught will not permit of a fire being lighted in that particular grate, unless the conditions are altered. In many of the vast buildings now being erected, the joinery work is very good and as the apartments are arranged in " flats," the rooms opening from one into another, this trouble is a common occurrence, the fireplaces being so far removed from the usual source of air, i. e. the entrance halls and corridors. Unless provision is made for supplying the chimneys with air they are almost compelled to have recourse to one another for it. It will be understood that the remedy for this is to provide inlet ventilation. It is much needed for other reasons in rooms that are so ill provided with air as this. The Tobins tube ventilators act well as they project the air towards the ceiling but it must be mentioned that if no efficient outlet ventilation is made for the vitiated air and products that rise to the ceiling, this inflow of air will tend to bring them down to be respired again, assuming that it is a living room that is being treated. This chapter will not permit of the subject of chimneys being treated at all exhaustively, but there is one other point that may be explained with profit to the reader, this being the occasional desirability or necessity of conveying smoke and products downwards from a fire, and horizontally under a floor, before they ascend normally in the chimney. This is commonly called, working a stove with " a descending flue," but the portion that actually descends is always very small, rarely more than 3 or 4 feet with a tall stove, but the hori- zontal portion under the floor may exceed this measurement very considerably. The necessity for this arises when a stove, perhaps of a highly finished character, is stood in an entrance hall, in a position several feet away from a chimney, and in which a smoke-pipe carried in mid-air or across the ceiling could not Chimneys. 463 be dreamed of. In such a case an elbow placed on the back of the stove and the pipe carried downwards and under the floor level is resorted to with every success, the only necessary provisions being a sufficient height of chimney, a non-com- bustible floor, and access to the underground pipe for sweep- ing. Sometimes the horizontal pipe is carried right through the floor, and suspended to the ceiling beneath but in that case, and in fact, in all instances the pipe should be sur- rounded 'with some material (non-inflammable) which will prevent loss of heat, as we must under these somewhat un- usual circumstances keep the chimney as efficient as possible. This can be resorted to almost with impunity with close stoves so long as the vertical chimney is in height, double the length * of the horizontal and descending flue, but in every case the joints must be made perfectly air-tight. With stoves or portable grates which have open fires more care is needed as will be understood, and a greater allowance of vertical chimney must be allowed in proportion to the length of the horizontal pipe. As a rule these latter articles should not be so fixed unless the chimney is 2j or 3 times the length of the horizontal and descending portions and the necessity for perfectly tight joints becomes even more marked. The descending and horizontal flues require most particularly to be of full size that is equal in area to the vertical chimney, and on no account should it be attempted to use small pipes with stoves or grates under these circumstances (see p. 459). When the horizontal flue is of moderate or of full length, it usually becomes necessary to make some provision for warming the vertical chimney or inducing a strong draught in it before the stove can be lighted, as it must be remembered that however efficient a chimney may be when receiving hot gases from a fire, this efficiency is very materially reduced when the fire is out and the draught is only due to the heat imparted to the air by the warmed brickwork. A draught caused by this * One and a half times will commonly do if the chimney is of ordinary efficacy. 464 Warming Buildings by Hot Water. latter means alone is not so strong that it can overcome serious obstacles and draw a volume of almost cold smoke downwards and along a horizontal flue. Usually a door, pro- bably a sweeping door, is placed at the base of the vertical chimney,* and the required effect can be brought about by thrusting some lighted straw or shavings in at this point, or if the works are on a somewhat extensive scale a small close stove called a " pilot " is fitted at this point, but this stove should only be lighted up when the other fire is being started and after that it should be well shut off by a tightly fitting damper. Where it is possible the underground flue is best made of earthenware pipes laid in concrete ; an earthenware pipe makes the very best of flues, and house chimneys are often made in this way the pipe being imbedded in the brickwork. * If possible this should be a little below the point where the horizontal flue enters. ( 465 ) CHAPTER XXII. VENTILATION. Ventilation by natural or mechanical means Quantity of air per person Table of quantities for various requirements Ventilation to living rooms Extract flues Table of velocities at different temperatures Air propulsion Relation of inlets to outlets Points of entrance for cold or heated air. THIS subject cannot very well be disassociated from that of heating, especially when the latter applies to building works ; and in places where large numbers of people congregate the subject of heating has of necessity to be considered in union with the subject of this chapter, for the ample ventilation needed in such instances will imperil the efficiency of the heating apparatus unless anticipated, and allowed for. The first practical consideration in ventilation is as to the quantity of air that should be taken from an apartment per minute (or per hour) per each person occupying it ; to carry away all or the necessary quantity of impure and vitiated gases, &c., and so keep the air within the space fresh, agree- able to the occupants, and not prejudicial to health. Very usually this is put about the other way, that is, the quantity of fresh air is spoken of as being introduced per person, but it must be submitted that this is not so correct, as we shall get more certain results if we exhaust the room of the quantity laid down, provided of course there be inlets for fresh air, and that the exhaust be carried from a point where the vitiated air will readily pass into it. There are, however, two ways in which ventilation is carried out, viz. by natural means or by some mechanical force ; in the former the exhaust system applies wholly, by withdrawing air by means of flues, but with the latter the term exhaust cannot always be held to apply, as in many instances, fans or 2 H 466 Warming Buildings by Hot Water. air propellers are used to force air into an apartment, and the outlets are thus compelled to act, so to speak, by the force exerted through the inlets. If we speak of the quantity of air required per person, we shall err, as from the suggested quantities about to be given, it will be seen that from 10 to 30 cubic feet is allowed to each person. No individual needs this quantity for respiration ; it represents the quantity that should be taken from the place per minute to carry away all noxious matters, that which is carried away being replaced by fresh air, which is afterwards rendered unwholesome and carried away in its turn. The actual quantity of poisonous gases and exhalations given off by a person, or from gas-burners (the only two causes that have usually to be dealt with) is small, and no great degree of ventilation would be needed to remove it, if there was a means of carrying it off by itself, but this is impossible, for these matters so readily mix themselves with the purer air, and make it all of an equal degree of impurity, that they require constant and abundant renewal. There is a very great diversity of opinion as to what quantity of air should be allowed to each person, or to each gas-burner, in an apartment (small or large). The quantities that we get from various writers range all the way from 3 to 30 cubic feet for a man undergoing no particular exertion, and ranging as high as 70 cubic feet for places where the occu- pants are in exertion, causing exhalations, and respiring to the fullest natural extent, as in ball rooms, &c., and for places where the exhalations from the persons of the occupants may be of a noxious character, as in some wards of hospitals, or in workshops of some particular trades. The quantities given are subject to variation in other ways, as for instance, women and children do not need such a great allowance as that given, which is for men ; the usual propor- tion is two-thirds for adult females and one-half for children of either sex. This allowance would apply to schools or any places devoted to women or children, but the minimum figures only apply to those who are in health, not engaged in active Ventilation. 467 work or exercise, and the air not being tainted from any other cause. If, in allowing any of the quantities now gfven, the air of the room had a perceivable odour, however faint, it should be considered that the ventilation is inefficient. In public places and apartments where no particularly odoriferous calling is followed, every trace of odour should be removed, and in doing this we may safely consider that all objectionable or poisonous gases of an inodorous character have been re- moved also.* Odours are more readily contributed to the air by living beings in summer than in winter, and in these figures allowance is made for this. The following Table shows approximate quantities of air per person that should be taken from a room occupied to its maximum capacity, the air inlet being sufficient, general conditions normal, and no extraneous sources of vitiation. Cubic feet per minute.f For ordinary living rooms, occupied by both sexes of all ages, average 20 For sleeping apartments, ditto 15 ,, schools scholars of full age 15 ,, ,, infants 12 ,, ,, dormitories 12 ,, workrooms, male workers, moderate exertion, air not vitiated by materials used \ 25 to 30 ,, ditto, ditto, but strong exertion 30 to 35 ,, meeting rooms, public halls, lecture rooms .. .. 20 to 25 ,, ballrooms 351040 ,, theatres, dining halls, &c 20 to 25 ,, hospitals, ordinary wards or exercise rooms ..' .. 20 ,, ditto, other wards where the dressing of wounds is done, and for infectious complaints 35 to 50 * Carbonic acid, the chief objectionable product of combustion, and which we get from gas-burners, and also in quantity from our lungs (which are rightly likened to fires, as the same process of combustion goes on), is inodorous. Almost the chief object of ventilation is to remove this gas. t An anemometer is used to test this. J In workrooms where odours, &c., arise from materials used, no rule can be resorted to. Judgment or experiment must decide. In instances where the ventilation is rapid, great care is needed in disposing the inlets to prevent draughts, and also the outlets, that the vitiated air may have instant escape, and not be carried about the room, and brought within other areas, in finding its way out. In hospitals the outlets should be numerous, as also the inlets. 2 H 2 468 Warming Buildings by Hot Water. The figures quoted are in addition to any natural means of ventilation that may exist, such as crevices around doors, &c., the occasional opening and shutting of doors or windows, or the existence of fireplace flues. It must be noted also that the quantities are approximate only, so very many circum- stances being likely to exist to vary the amount to some extent. If others' calculations are found to disagree with these, it must be remembered that most probably no two ventilating engineers will be found to agree exactly in this respect, even if conditions are normal. If draughts are skil- fully avoided and warmth (in winter) not sacrificed, it would be almost impossible to err on the side of too great a quantity of air, but of course an increase of ventilation, or what is the result of ventilation, usually means an increase of expense, both at first outlay and afterwards. The methods of ventilation are practically confined to two, viz. flues which act naturally in withdrawing air from an apartment as a chimney does, the flue or flues having a draught by the warmth imparted to them by the vitiated air, or being warmed by a stove or a gas-burner, in which case the draught is more powerful ; or, on the other hand, the change of air may be effected by mechanical means, by a blower, fan, or air propeller, driven by steam or any other motive power,* the air being either extracted from an apart- ment or forced into it, either way being efficient, although the writer is in favour of the former as being more certain of attaining the results required, viz. the withdrawal of the bad air. In ordinary living apartments, the needed change of air is almost always effected by the fireplace chimney, and the badly fitting doors, &c. Sometimes ventilators are provided, but it is no uncommon thing to find them papered over or stopped in some way, for their cooling influence is objected to when the room is large and the fire only just capable of heating it without too lavish a degree of ventilation. Sometimes it is * There can be obtained a small hydraulic motor suited for this purpose, which can be fixed at any point conveniently, a supply pipe to it, and a waste pipe from it, both small, being all that is needed. Ventilation. 469 considered that to conserve the heat of a room, saves the fuel, but the conservation of the heat in a general way can only be effected by retaining the noxious elements that we should make an effort to remove. The power of an ordinary open grate chimney is very great, and amply sufficient for an ordi- nary room if under common circumstances the objectionable gases, &c., could be removed from their place of lodgment in the upper part of the room, by it, but this is not usually the case, and the aid of a ventilator is needed. Still, referring to an ordinary living apartment, if we wish for an outlet ventilator to act as an outlet, with certainty ', we must place it in a flue or chimney * which might be termed an air extractor. If we place it in an outer wall it will most probably act as an inlet, if its construction will permit it, as, assuming there is a fireplace in the room, the chimney will most likely at once take part of its air supply from this opening. As a rule all openings into a room, if they are not very numerous, or very large, will act as air inlets if there is a good chimney leading out of it, and this result is more certain when a fire is burning, and the draught is at its strongest. It would be difficult to make any simple rule as to the proper sized ventilators to be used for this purpose, as it would depend upon the number occupying the room when it contained its full complement (this, however, would permit of easy calculation), but more greatly upon the draught in the chimney. The extracting powers of ventilating flues, which are practically chimneys, will be spoken of presently, but com- plex calculations are hardly needed for such ordinary purposes as these. We are supposing a good chimney exists in a room ; this is always sufficient to induce a free inflow of fresh air (inlets existing, either by crevices or provided) to keep it well supplied for respiration, and if by some simple means we take away the collection of heated and vitiated air near the ceiling the desired end will be attained. The size of a ventilator for * Of course chimneys which have down-draughts cannot be utilised in this way. 470 Warming Buildings by Hot Water. this purpose * may be as follows : Rooms about 10 feet by 10 feet, two, or perhaps three occupants, say, two gas-burners ; ventilator 9 inches by 3 inches inside measure. Rooms about 1 6 feet by 12 feet, three or, perhaps, four occupants, say, three gas-burners ; ventilator 9 inches by 6 inches inside measure. Rooms about 20 feet by 16 feet, four, or, perhaps, five occupants, say, four gas-burners ; ventilator 9 inches by 9 inches (or equal area). Larger rooms than the latter can have a single ventilator to carry off the upper air referred to, if the number of people be small, but when the rooms get larger than this two ventilators should be provided (if there is con- venience for two) or some special means provided for carrying off the air from two or more points in the room ; this is sup- posing that the room be really large and occasionally occupied by a large company and having many lights to add to the volume of carbonic acid. Low rooms require more attention than high ones. Rooms in which there is no fireplace and its accompany- ing chimney require very different treatment, for we lose a valuable assistant to ventilation when this is absent, and in treating such, the rule as to quantity of air per person, &c., on p. 467, must be considered in the first place, then the means of withdrawing the fouled and of introducing the fresh air in the proportion that the rule gives. Where it is possible the most economical results (both in cost and attention) are effected by natural ventilation by means of flues provided in the building, which act as ex- tractors in the same way as chimneys. These, however, will not be so effective, that is, give such an extensive result as chimneys, unless they are artificially heated. This can be done if the circumstances require it, by gas or a stove, at comparatively little cost and with little attention. To arrive at the working value of a ventilating shaft, we cannot do better than have recourse to another of Hood's * The ventilator to be inserted into the chimney of the roonvthrough the chimney breast, as near as possible to the ceiling. Ventilation. valuable tables, which he has compiled upon actual effective results, making all needed allowances. The temperature of the outer air and the temperature of the vitiated air passing into the flue need only be ascertained to put this rule to practice. It will be noticed that the doubling of the height of the ventilating shaft does not double its extracting power ; this is due to loss of heat by the ascending air, and friction. The following Table shows the quantity of air in cubic feet, extracted per minute by a ventilating shaft of which the area at the entrance (and not less at all points) is one square foot, the fresh air inlets being equal in area or a trifle larger : Height of Ventilating Shaft in Feet. Excess of Temperature of Air entering the Ventilating Shaft, above the External Air. 5 10 15 20 25 30 10 116 164 200 235 260 284 15 142 202 245 28 4 3i8 348 20 164 232 285 330 368 404 25 184 260 318 368 410 450 30 201 28 4 347 403 450 493 35 218 306 376 43 6 486 53i 40 235 329 403 465 518 570 45 2 4 8 348 427 493 55i 605 50 260 367 450 518 579 635 As an example of the above let us suppose a ventilating shaft 30 feet high and the difference in temperature of the two airs to be 1 5, then the discharge would be 347 cubic feet per minute, or if the height be 40 feet and the difference in temperature 20 then the discharge would be 465 cubic feet per minute. Let it be clearly understood that the height of the ven- tilating shaft will be governed by the height of the building, not by the requirements, for unless this be done we must not expect efficiency. These flues are governed by precisely the 472 Warming Buildings by Hot Water. same rules as fire chimneys and may be subject to down- draughts and other ill effects from the same causes, which would utterly destroy their efficacy (see Chimneys). If flues are carried horizontally to any extent their efficacy is lowered. In calculating the area of an extracting flue it must be remembered that it is at its greatest efficiency in winter, when the outer air which actually causes the draught in the shaft is coldest, the greater degree of specific gravity between the two giving the greater effect, as the table shows. Consequently the area should be calculated upon summer ventilation. At the same time, however, we do not get air vitiated by gas to the extent in summer that we do in winter unless the rooms be chiefly occupied late in the day or night. If the area of the ventilator for the summer be too great for the winter this can be regulated by the mechanism of the ventilator itself, as it is not supposed that the shaft terminates in the room by a mere hole. In very hot weather, in crowded places, the extracting shaft is not usually sufficient if left to operate by the mere dif- ference in the temperature of the fresh and vitiated air, for at this time the difference is very little. Even if the area of the shaft was made unusually great it would not suffice for such a number of people as we get in a theatre, so it is better to have the shaft of reasonable size and heat and rarefy the air pass- ing into it. In theatres this is usually done by the central sun-burner, and the ceilings of such places are constructed of a shape adapted to a good end, curving upwards towards the centre where the extracting opening is. This arrange- ment of ceiling is undoubtedly a great advantage and goes far towards giving perfect results. Occasionally, in very large undertakings, an independent shaft has been erected, that is at the side, but not necessarily within the building, and the air within the shaft rarefied by a large coke fire at the base, which would induce a strong up- draught within it like a chimney. Into this shaft would be connected the extracting flues from various rooms or places, Ventilation. 473 and the draught of the shaft would confer its power upon these flues and make them of proportionate power in convey- ing the vitiated air as required. This plan, and, in fact, any plan of utilising one shaft for many minor ones has the disad- vantage of causing these latter to work unequally, supposing they do not all proceed from the same level. It is better wherever possible to have separate shafts for different floors of a building, or if one shaft, let it be divided in some way (lengthwise), and so be converted into two or more as needed. The mechanical means of ventilation are confined to those contrivances which propel air, either propelling the exhaust outwards, in which case the air passes into and through the air inlets naturally, or propelling the fresh air inwards, in which case, the outlets act by the pressure of the incoming air forcing outwards that which is already in. There are several forms of these contrivances, the modern patterns being termed " air propellers," * and are open fans, in contradistinction to those which expel the air through an orifice and are very usually termed " blowers." It is unnecessary in this short chapter to enter into the effected value of the vanes, their size, shape, or angle, as it is not supposed that the engineer himself proposes to make these appliances, and the maker's guaranteed values can be looked to for this. When the quantity of air is known the maker can be relied upon to furnish what will propel this amount effectually, the general conditions being correct. When an air propeller is used, the height of the vitiated air shaft, or openings, is not of such moment as with flues actuated by the rarefaction of air ; down-draughts, &c., not producing very noticeable ill effect. The air inlets are next to be considered ; they must have relation to the outlets or the effectiveness of one or the other will be imperilled. The air inlets must be fully large, the minimum being the same area as the outlet or outlets, but a little larger is always preferable. The inlets are spoken of in this plural sense, as it is nearly always necessary to have more than one, although perhaps the air may be in some instances conducted to the apartment by a single conduit. If we bring * The Blackman air propeller is of high efficiency. 474 Warming Buildings by Hot Water. the whole of the air in at one point we may not succeed in equally distributing it, so that at some parts of a large apartment, the air may tend to be stagnant to some extent, at any rate, more than at other parts, depending upon various circumstances, and what is worse, if the inflow is in good volume, for a large place, we should introduce a draught that would be intolerable, for although air readily diffuses itself in the usual way, we shall not get this agreeable diffusion when the air has attained momentum. Thus it is necessary in practically every case to break up and distribute the incoming air to the greatest extent possible. If the inlet air be warmed by any of the processes de- scribed in the previous chapters, the draughts would lose some of their objectionable features, or at least they would be mini- mised, but still the inflow should be broken up and made as equal as possible at all parts, for reasons that will be now understood. It is understood that heated air (inflow) can be induced to travel simply by its rarefaction, but the force it exerts in thus urging itself into the room is not sufficient to make simple openings in walls act as outlets, there must be extract ventilators.* There is a greater diversity of opinion than ever as to where inlets should be situated, high up, low down, or midway. A great number are in favour of introducing the new air at a high point, the contention being that if low, draughts are created, dust carried up and the lower part of the room and the body kept cold as the warmed air immediately rises and passes away, and the cold air as immediatly flows in, and so it proceeds perpetually, the lower part of the room never having a chance to get warm. This is very good as regards inflow of cold air and in winter, but if the air be warmed, or if it be sultry weather, the argument is rather at a loss. If we introduced warmed air near the ceiling and the extract shaft opened at that point also, it would be to the prejudice of the lower part of the room, as we may consider * In ordinary living apartments of medium and small size, the fire- place chimney is the active ventilator, as already explained. Ventilation. 475 the room would not be so air-tight that cold air would not be entering somewhere. If the room be heated by hot-water pipes, the introduced air might be cold, and in this case if brought in over the pipes (being warmed by them) it should come in at a low point through gratings in the floor or the skirting ; but if the air is not warmed it should be brought in near the ceiling or through ventilating tubes (Tobin's tubes), which project the inflowing air towards the ceiling and avoid draughts. If these tubes are not used the cornice can be adapted for the pur- pose in view, but the air must be led to enter at many points, and even at these points it should encounter some obstacles to break its momentum, to spread it, or reduce it to threads. The particular objection raised to bringing in cold air near the ceiling, is that so soon as it has lost its momentum, it com- mences, by its superior gravity, to sink (this is desirable), but it has, by coming in contact, also cooled some of the carbonic acid * and other bad gases which always rise to the ceiling, and by so increasing their gravity bring them down also, to be again respired ; in other words, it brings down some of our breath to be breathed again, a thing that every one would certainly consider wrong. There is much to be said in favour of bringing in the fresh air (if cold) at an intermediate distance just above people's heads, but in doing this, there must be no inrush, it must be brought through fine perforations, and then it should be first deflected to and fro to break the current f If the place be large some must necessarily be brought centrally, and this cannot usually be done except through the floor, in which case it should be warmed but still distributed to as great an extent as possible to prevent currents, which are as disagreeable, if not so dangerous, with hot as with cold air. * Of carbonic acid and air, at the same temperatures, the former has the greatest weight, and would fall more quickly than air. See Appendix, Table XIII. t We cannot very sensibly break up a strong current except by distributing in several directions simultaneously ; it is better to do it by increasing the number of points of inlet. 476 Warming Buildings by Hot Water. There are just a few advocates for introducing (in ordinary living apartments) warm air, heated in an air chamber at the back of the fire grate, at the ceiling, the whole of the extract work being done through the grate entrance to the chimney. By this arrangement we may suppose that all vitiated matters from the occupants are carried downwards as exhaled, by the perpetual down current of air that must be supposed to exist, and so far the results would be efficient But what becomes of the oftentimes greater bulk of noxious gases that are caused by burning gas ? These must be carried down too, and it may be imagined that a person sitting close to the fire would have all the ill products that were generated, carried past him in their passage to the chimney. Even if this were desirable, it would be somewhat neutralised by the cold air that must enter (though in less quantity than when no inlet of fresh air exists) from the usual sources, ill-fitting doors, &c., as this supply keeps low until heated. In general we may consider successful ventilation to be the withdrawal to the utmost extent of everything that is not breathable, no possible opportunity to inhale products of either combustion or respiration (one and the same thing), and to effect this a sufficiency of new air must be introduced at the same time, but without draughts, and without disagree- able sensations of coldness, &c. ( 477 ) CHAPTER XXIII. THE METROPOLITAN BUILDINGS ACT. ITS APPLICATION TO HOT-WATER, STEAM, AND HOT-AIR WORKS, AND TO CHIMNEYS AND SMOKE-FLUES. THE object of this paper is firstly to be a ready reference for those engaged in these works, as reference should be made with all new undertakings, unless the whole information be committed to memory, which is neither convenient nor usual, except a person be engaged in all branches of these works perpetually. Another reason for treating this subject is to make as clear as possible what the Act requires, and to point out the unreasonable and perplexing features, and also the arbitrary constructions that surveyors can put upon the read- ings, if so desired. The various sections are as follows : M.B. ACT (18 & 19 VICT., CAP. 122), 1855. Sec. XX., sub-sec. 1 1 : There shall be laid level with the floor of every story, before the opening of every chimney, a slab of stone, slate, or other incombustible substance, at the least 12 inches longer than the width of such opening, and at the least 1 8 inches wide in front of the breast thereof. Do. ; sub-sec. 12 : On every floor, except the lowest floor, such slab shall be laid wholly upon stone or iron bearers, or upon brick trimmers ; but on the lowest floor it may be bedded on the solid ground Do. ; sub-sec. 13 : The hearth or slab of every chimney shall be bedded wholly on brick, stone, or other incombustible substance, and shall be solid for a thickness of 7 inches 478 Warming Buildings by Hot Water. at the least beneath the upper surface of such hearth or slab. Do.; sub-sec. 17: No timber or woodwork shall be placed : In any wall or chimney breast nearer than 12 inches to the inside of any flue or chimney opening. Sec. XXI. The following rules shall be observed as to close fires, and pipes for conveying heated vapour or water ; that is to say : 1. The floor under every oven or stove used for the purpose of trade or manufacture and the floor around the same, for a space of 18 inches shall be formed of materials of an incombustible and non-conducting nature. 2. No pipe for conveying smoke, heated air, steam, or hot water shall be fixed against any building on the face next to any street, alley, mews, or public wall. 3. No pipe for conveying heated air or steam shall be fixed nearer than 6 inches to any combustible materials. 4. No pipe for conveying hot water shall be placed nearer than 3 inches to any combustible materials. 5. No pipe for conveying smoke or other products of combustion shall be fixed nearer than 9 inches to any combustible material. And if any person fails in complying with the rules of this section he shall for each offence incur a penalty not exceeding twenty pounds, to be recovered before a Justice of the Peace. AMENDMENT ACT (45 VICT., CAP. 14), 1882. Sec. XVI. From and after the passing of this Act the restrictions imposed by the twenty-first section of the Metro- politan Building Act, 1855, with respect to the distance at which pipes for conveying hot water or steam may be placed from any combustible materials shall not apply in the case of pipes for conveying hot water or steam at low pressure. The Metropolitan Buildings Act. 479 From Sec. XX., sub-sections 11, 12 and 13, we learn that every grate, stove, or cooking range in a building shall stand upon a hearth of non-combustible materials, which hearth must measure at least I foot wider than the opening in which the appliance is placed, it must extend at least I foot 6 inches beyond the front of the chimney breast, and it must be at least 7 inches thick. In fixing the width and front extension of the hearth, the supposition was that the stove, grate, or range would occupy the whole width of the opening, as is most usually the case, and it would not extend or project out beyond the level of the front of the breast. This latter is frequently departed from, but no provision is made to meet it. In the strict letter of the Act, no objection could be raised to a stove which, if placed in the opening, projected well into the room, even close up to the floor boards,* no mention being made of the hearth extending 18 inches in front of the stove ; and although a measurement of 18 inches for both the width and front extension is mentioned in the first sub-section of Section XXL, this could not be held to apply, as it restricts itself to trade and manufacturing purposes. District Surveyors, however, hold that the Act intends the front and side exten- sions of the hearth to be beyond the heating or cooking appliance, and their decision is a sound one, although not directly implied in the Act. Now, as the thickness of the hearth, 7 inches, is sufficient for what this portion of the Act refers to, viz. grates for warming rooms, and kitchen ranges, as the thickness mentioned, whether of stone, brickwork or concrete, will ensure solidity and the like, but, for this small purpose the Act clearly says that this hearth must not be supported on wood-work. A little enquiry would elicit the fact that there are countless numbers of hall stoves, stoves in other situations, and portable kitchen ranges fixed and working, standing out in the hall or room, not within a chimney opening, but having connection with the chimney by a pipe. If any of these stoves are on a * A Fire Insurance Company might reasonably object. 480 Warming Buildings by Hot Water. ground or basement floor with the hearth just beneath, there may not be any wood beneath them, but if the floor has rooms or cellars beneath, there can be every assurance that the hearth (or what in this instance is called a base) rests upon wood-work. Not one person in a hundred would dream of cutting through the floor, the joists, and the ceiling below, and go to the great cost of inserting iron or other incombustible supports for the base upon which the stove is to stand, when perhaps the value of the little stove may be one pound.* In the first sub-section of Section XXL, just referred to, and which applies to trade and manufacturing purposes, an aggre- gate thickness of 1 8 inches is mentioned without any sugges- tion as to the nature of the supports. In this case (in which we may suppose far greater heat is experienced) it can be assumed that wood may exist beneath this 1 8 inches of material. Usually small stoves and the portable cooking ranges are fixed on a stone or concrete base, resting upon the wood floor, this base being 7 inches thick, I foot wider than the stove or range each side, and projecting beyond the extreme front of the stove or range 18 inches. This complies with the require- ments of practically all the Fire Insurance Companies. Sur- veyors will commonly pass it (although they can object if they wish to be arbitrary), and it can be looked upon as perfectly safe. It will be noticed that it complies with the terms of the Act in every way except as to what the hearth is supported upon. The extension of the hearth in front of a grate or stove which must be 18 inches, at the least, should have a fender or a curb, or a boundary of some incombustible material pro- vided ; without this, the extension named is insufficient for safety, more especially in a kitchen where firstly a fender or * Perhaps this sort of thing is left to the discretion of the district surveyors ; this would suffice if their discretion was always the same, and always practical and unbiassed, but in no two districts do the surveyors have a discretion that is of the same degree or character ; it is hardly to be expected, and it is tremendously awkward to the stove and range fixer, who has bu s i ness m a ii districts, and for him the Act might as well not exist. The Metropolitan Buildings Act. 481 curb is not always used, and secondly the live fuel which drops from the fire, having a little distance to fall, readily bounds or is projected into the room, sometimes to a consider- able distance.* With living-room grates, fenders or curbs are always used, and thus no harm results, but in kitchens the front extension of the hearth should be 3 or 4 feet ; there can be no objection to this, as supposing the kitchen is not on the ground floor, the additional cost would not be at all serious even in small property. In sub-sections 3, 4, and 5 of Section XXL, pipes for the conveyance of hot air, steam, hot water, and products of com- bustion (pipes from coal or coke-burning stoves, &c.) are dealt with. Now heated air and steam (at high pressure) are treated alike as to the least distance they must be from wood- work, viz. 6 inches, but although hot air is decidedly able to cause ignition to ordinary combustible substances, steam at high pressure would not even scorch or discolour them unless it were superheated. Thus the distance for steam pipes, even with steam at high pressure, could well be reduced ; and as to residence work, where high pressures are not attained, the lessened distance would be a boon in reducing, firstly, cost in supporting the pipes, and, secondly, their unsightliness. With hot-air pipes, 6 inches is barely sufficient close down by the furnace. With a stove of the " cockle " variety, it is possible by careless firing to raise the temperature enormously, and although 6 inches is sufficient distance to prevent actual ignition, it will permit of the materials getting into such a state that a lucifer match would complete the mischief. If they be papered surfaces the paper may split and curl off and come in contact with the pipe, and similar results might accrue from other substances. As the pipe gets away from the stove the heat becomes lessened (unless it be covered with some non-inflammable and poor heat-conducting material, * Nearly every one has had experience of this, floor-cloth and mattings being burnt with holes, and in houses where the ranges are large the floor- boards in front of the fireplace have numbers of burnt marks upon them. This is just as likely to happen and cause serious results at night, if a fire is left the last thing. 2 I 482 Warming Buildings by Hot Water. when it would be rendered safe in another way) and a 6 inch limit would suffice after, say, the first 1 5 feet* Sub-section 4, which required a space of 3 inches between hot- water pipes of every description and adjacent woodwork, has been partially amended, as was very necessary and will be referred to again directly. Sub-section 5 deals with pipes (made of any material) which convey smoke and products of combustion in other words, stove-pipes. The limit of 9 inches space between a smoke-pipe and inflammable material is decidedly insufficient with horizontal pipes carried beneath ceilings ; \ although perfectly safe when working normally they would be highly dangerous if allowed to get foul (for there is no restriction as to the length of time which they are to go unswept) and so caught alight. In such a case as this, the pipe, if of sheet iron,J would get red-hot and remain so some time, as the soot collects so abundantly in horizontal flues and more particularly in sheet-iron pipes, with which, the outer cooling influence augments the deposit considerably. It seems a little odd that so low a limit should be set when sub-section 17 of Section XX. says, "No timber or woodwork shall be placed : In any wall or chimney breast nearer than 12 inches to the inside of any flue or chimney opening," thus increasing the distance to 12 inches ; and this space being of solid brickwork would keep the woodwork from reaching a temperature of 1 00, from an ordinary house chimney, such as here meant, even if the chimney were on fire. With a chimney pipe of sheet iron we have a more dangerous thing than a hot-air pipe, from its liability of getting fouled by bituminous fuels. When this soot deposit gets fairly alight we experience a heat as great as from fire, sheet-iron enclosure being as nothing, and on this account a * If the air in the pipe was heated by hot- water pipes no space at all would be needed, although the Act makes no distinction. f Match-lined in particular. \ If an earthenware pipe, as sometimes used, it would most probably fracture, and so be more dangerous. The Metropolitan Buildings Act. 483 pipe of this description should be treated as a stove, so far as distance from inflammables is concerned.* The Amendment Act of 1882 contains the clause given on p. 482, referring to pipes conveying steam or hot water, it having been urged that sub-section 4 of Section XXI. of 1855 was unreasonable, and, if insisted upon, created un- necessary expense and trouble and thereby caused a deal of friction in the working of the Act. It was not thought desirable to extend the Amendment to all such pipes, that is, not to those for high-pressure steam, or to those of Perkins' high-pressure circulating apparatus, or to any erected upon this system or its modifications ; consequently the Amend- ment and its liberty from all restrictions only applies to hot- water and steam pipes at low pressure. This Amendment has been acceptable, but has introduced one of the most annoying and perplexing things that could be imagined, as no really practical meaning can be attached to the words " low pressure." Surveyors are here again all inclined to put different meanings to it ; some are as lenient as others are vexatious. There is no doubt that when this clause was framed it was understood that " low pressure " was a common term bearing a commonly understood mean- ing, and it is possible that in and about England there are districts where the term may have a regularly accepted construction, but it can be confidently asserted that an accepted meaning is not universal, nor is it general. Some surveyors contend that "low pressure" applies to steam or hot-water apparatus that have a maximum attain- able temperature of 212. This contention, with all respect to those who hold it, is utterly absurd, as it is hardly possible to have a hot-water apparatus f that would not register a higher * It will be understood these are merely suggestions ; the Act gives the least distance ; when a doubt is felt the Act places no limit to a greater distance, and as a rule 15 inches is better, usually making no difference in cost of works. t This does not refer to a sealed apparatus, but to the ordinary domestic kind, either for warming or draw-off purposes with open expansion or air pipes. 213 484 Warming Buildings by Hot Water. temperature than this down close to the boiler. If the ap- paratus only extended 10 feet high we could get 220 close to the boiler, and with increased height we could get increased temperatures (see High Pressure and Table I. of Appendix). If we are bound to 212* the Amendment is useless : only in open vessels or a boiler with an open and empty expansion pipe from it, can we say 212 is the very highest we can get. If we had a closed boiler and arranged to fill up the expan- sion pipe but a few inches we should come outside the Amend- ment if that is its meaning, for by these few inches a certain weight would be pressing on the water below and the tem- perature would rise, only a fraction of a degree, and perhaps hardly perceptible, but nevertheless positive. The water in a vessel must be absolutely free from pressure or weight exerted upon it to ensure its keeping down to 212 when it boils ; indeed, if perchance the vessel itself was a very high one we could get a greater temperature at the bottom of it, without filling up a pipe. It has been explained more than once in this book, that with a hot-water apparatus extending up one or more floors of a building a great pressure or strain is brought to bear, particularly in its lower parts, by the pressure, or rather the mere weight, of the water that it contains. The boiler, which is the lowest point and has the greatest strain, has to with- stand and bear a pressure of I Ib. to the square inch for every 2 feet 4 inches | that the apparatus extends above it, calcu- lating vertically to the highest point to which it contains water, this strain being exerted whatever be the size or quantity of the pipes, &c. Now, if we have an ordinary domestic apparatus in a large house extending up and con- taining water to say 50 feet above the boiler, we shall get a pressure at the lowest point of fully 21 Ibs. to the square inch, * As a general rule hot-water apparatus, either for domestic supply or for heating, and having an open expansion pipe, are passed by surveyors as coming within the meaning of the term " low pressure." t Exact measurement is given in footnote under Low Pressure Building Works. The Metropolitan Buildings Act. 485 and by referring to Table I. in the Appendix we shall find that water having this pressure upon it * will reach 260 before it boils and ceases to rise in temperature. In a hot-water ap- paratus with an open expansion pipe the temperature would vary throughout its height, being highest at the bottom and decreasing upwards. This is a long explanation perhaps, but a desirable one in order- to make the peculiarity of the term " low pressure " understood. Sometimes, in fact commonly, a surveyor or other authority will call any apparatus having an open ex- pansion pipe, low pressure, and coming within the meaning of the Amendment ; this is very reasonable, but does not convey any exact interpretation. In its application to steam pipes the trouble is just as great perhaps even more so. For what is the universal meaning of steam at " low pressure " ? There is none. It may mean exhaust steam, commonly used for heating, the service ending in an open pipe, and therefore causing no pressure in the proper meaning of the word. More pro- bably there was some limit of pressure intended which would be properly considered to be low. However, as the writer is informed,! different people who survey such works, and, so to speak, administer the Act, allow 4 pressures varying from 5 Ibs. to 30 Ibs. as being within the meaning of the Amendment ; but no reasons are assigned for the limitation of pressure that is made. From somewhat lengthy experiments made by the writer, it was found that a temperature of 600 communicated to iron directly from the fire was insufficient to ignite paper, shavings, or splintered pieces of wood (deal) ; the paper was discoloured, but after subjecting it to a still higher temperature, about 650, ignition did not take place. Thus so far as fire from ignition * It matters not how the pressure is exerted, the effect is the same. f The writer is greatly indebted to Mr. Arthur Harston, F.S.I., for much valuable information and many practical suggestions, it having fallen to that gentleman's lot to unravel many knotty points and have great experience in this direction. 486 Warming Buildings by Hot Water. was concerned there was perfect safety ; but it will be under- stood that these materials were rendered in a very prepared state for being lighted if an already lighted substance was brought into contact Even if woodwork, &c., were allowed to get into this state it would be no greater, if as great, a source of danger as the baskets or boxes of straw and shavings that lie about in nearly every residence cellar and in some lumber rooms, &c. From these experiments a very certain conclusion could be drawn that a temperature of 350 would be perfectly safe for steam or hot-water pipes in contact with woodwork, and this temperature would not be a dangerous assistant to a fire arising from any other cause. These temperatures would then cover any domestic supply or heating apparatus (with an open expansion pipe) that is likely to be erected ; it would also cover those high-pressure works in which a regulating valve is used, and it would also cover all steam works where the steam is not superheated. The reason for advocating the exemption of pipes up to this temperature is that in many works, in fact all those in residences and the like, the 6-inch and 3-inch distances of Section XXL are very objectionable, adding to the cost very materially. Where the pipes are in sight special brackets have to be provided, creating unsightliness, and where the pipes are carried behind or beneath woodwork the provision for the needed space entails a great amount of work and expense in very many ways.* It is noticeable that the Act and its Amendment make no mention of covering these various pipes with any material to conserve their heat and so permit of their nearer approach to woodwork when circumstances make it particularly ad- vantageous and desirable, as very often happens. Perhaps when the Act was drawn a hesitation was felt in naming a material, but no doubt need be felt now, as we have the very * With the high pressure system, the pressure not limited by a valve, the space might be safely reduced to i inch, and prove a great convenience and advantage in many ways. The Metropolitan Buildings Act. 487 thing in silicate cotton ; non-inflammable, therefore suited for water or stove pipes ; cheap, and therefore applicable to all works ; very easily applied ; having many minor features to its credit, and being in favour everywhere.* If it were ever de- sired to reframe the Act, it would be a great boon to make a provision this way, allowing certain reductions in distance if this material were used in a certified thickness ; as, for instance, if it were thought undesirable to allow high pressure water and steam pipes to have actual contact with wood, a quarter inch of silicate cotton interposed between the pipes and wood- work would make them perfectly and absolutely safe. En- gineers would not object, as a covering of this material to their pipes ensures better results in the apparatus, as has been fully explained elsewhere. Smoke and hot-air pipes would come within its application, and in some cases ensure decided advantages.! * It has been mentioned elsewhere that from experiments quite recently conducted in America, silicate cotton, of all non-inflammable substances, had the least heat-conductive properties. t An experiment was made with a thickness of silicate cotton of i inch, rather tightly packed, placed tight against a surface at bright red heat, about 1550, for 30 minutes ; at the end of this time the outer side of this material was only about 180, almost bearable to the hand. No currents of air existed to have a cooling influence. 0II7IBSITT ( 488 ) APPENDIX. TABLE I. TEMPERATURES THAT CAN BE ACQUIRED BY STEAM OR WATER AT CERTAIN PRESSURES J OR, A TABLE OF THE FORCE EXERTED BY STEAM OR WATER WHEN IN CONFINEMENT, AND AT TEMPERATURES ABOVE 212 F. Heat in Pressure. Heat in Pressure. Heat in Pressure. degrees of Fah. Atmo- spheres. lb. per sq. in. degrees of Fah. Atmo- spheres. lb. per sq. in. degrees of Fah. Atmo- spheres. lb. per sq. in. 212 I 15 275 3 45 393 15 225 216 16-5 294 4 60 399 16 2 4 220 17-7 3 08 5 75 404 17 255 22 5 I9'5 320 6 90 409 18 270 230 21-5 332 7 105 414 19 285 235 23-6 342 8 120 418 20 3 00 240 25-8 351 9 135 439 25 375 245 28' i 359 10 ISO 457 30 45o 250 2 30-9 367 ii I6 5 473 35 525 255 33'6 374 12 180 487 40 600 260 36-1 38i J 3 195 5ii 50 75o 265 39*o 387 14 2IO 53i 60 900 270 43'i TABLE II. QUANTITY OF VAPOUR CONTAINED IN ATMOSPHERIC AIR AT DIFFERENT TEMPERATURES, WHEN SATURATED. Temperature of the air. (Fah.) Quantity of Vapour per cubic foot in Grains Weight. Temperature of the air. (Fah.) Quantity of Vapour per cubic foot in Grains Weight. Temperature of the air. (Fah.) Quantity of Vapour per cubic foot in Grains Weight. o 20 I-52 4 3'94 76 9-38 22 1-64 50 4-19 78 9*99 2 4 1*76 52 4-46 80 10-59 26 1-89 4'77 82 11*29 28 2-03 56 5-06 84 11*98 30 32 2-16 2-31 g 5-40 5-76 86 88 12-68 13-36 34 36 2-43 2-62 62 64 6-12 6-50 90 92 I4-93 38 2-80 66 6-91 94 15-81 40 2 -99 68 7'3I 96 16-76 42 3'2I 70 7'77 98 17-83 44 3'45 72 8-27 100 19-00 46 3-69 74 8-80 The capacity of air for water is about doubled by each increase of 27 F. Appendix. 489 TABLE III. EXPANSION OF AIR AND OTHER GASES BY HEAT, WHEN PERFECTLY FREE FROM VAPOUR. Temperature (Fah.) Expansion. Temperature (Fah.) Expansion. 32 1000 100 H52 35 1007 no 1178 40 102 1 120 "94 45 1032 I 3 1215 50 1043 140 1235 55 1055 150 1255 60 1066 160 1275 65 1077 170 1295 70 1089 180 1315 75 1099 190 1334 80 1 1 10 200 1354 85 1121 210 1372 90 1132 212 1376 95 1142 TABLE IV. VELOCITY OF CHIMNEY DRAUGHT AT DIFFERENT TEMPERA- TURES, THE EXTERNAL AIR BEING AT 32 F. Temperature of warmed air. (Fah.) Relative Velocity. Temperature of warmed air. (Fah.) Relative Velocity. Temperature of warmed air. (Fah.) Relative Velocity. 86 4'93 230 7-48 o 374 8-14 I0 4 5-5I 2 4 8 7-62 392 8-17 122 5'98 266 7*73 410 8-12 I 4 6'35 284 7-83 428 8-23 I 5 8 6-66 302 7-92 446 8-25 I 7 6 6*92 320 7'98 464 8-26 194 7-13 338 8-05 482 8-27 212 7'33 356 8-09 At the temperature of 482, or just thereabouts, the velocity ceases to increase, and at higher temperatures it actually decreases, owing to the very great expansion of the air. 490 Appendix. TABLE V. SPECIFIC GRAVITY AND EXPANSION OF WATER AT DIFFERENT TEMPERATURES. Tempera- ture, Fahr. Scale. Expansion. Specific Gravity. Weight of i Cubic Inch in Grains. Tempera- ture, Fahr. Scale. Expansion. Specific Gravity. Weight of i Cubic Inch in Grains. o 30 00017 999 8 252-714 121 01236 9878 249-677 32 oooio 9999 252-734 124 01319 9870 249'473 34 00005 '9999 252-745 127 01403 9 86l 249-265 36 00004 '9999 252^53 130 '01490 9853 249^53 38 'OOOOO2 '9999 252-758 133 01578 9844 248-836 39 ooooo i-oooo 252-759 136 01668 9836 248-615 43 00003 9999 252-750 139 01760 9827 248-391 46 oooio 9999 252-734 142 01853 9818 248-163 49 '00021 '9997 252-704 H5 01947 9809 247-931 52 '00036 9996 252-667 148 02043 '9799 247-697 55 00054 '9994 252-621 151 02I4I 9790 247-459 58 00076 9992 252-566 154 "02240 9780 247-219 61 ooioi 9989 252-502 157 02340 9771 246-976 64 00130 9986 252-429 160 02441 9760 246-707 67 00163 9983 252-349 163 02543 "975 1 246-483 70 OOlQS 9981 252-285 166 '02647 9741 246-233 73 00237 9976 252-I62 169 02751 973i 245-982 76 00278 9972 252-058 172 02856 9721 245-729 79 00323 9967 25^945 175 '02962 9711 245-474 82 00371 9963 251-825 178 03068 9701 245-218 85 OO422 9958 251-698, 181 03176 9691 244-962 88 00476 9952 251'564 184 '03284 9681 244-704 9i 00533 '9947 251-422 187 03392 9671 244-446 94 00592 9941 251-275 190 03501 9660 244-187 97 00654 '9935 25I-I2I 193 03610 9650 243-928 100 007l8 9928 250*960 196 03720 9640 243-669 103 00785 9922 250-794 199 03829 9630 243-410 106 00855 9915 250*621 202 03939 9619 243-I5I 109 00927 9908 2 5 "443 205 04049 9609 242-893 112 oiooi 9901 250-259 208 04159 '9599 242-635 H5 01077 9893 250-070 212 04306 9585 242-293 118 01156 9885 249-876 Appendix. 49 1 TABLE VI. EFFECTS OF HEAT. Fahr. Q Temperature of a blast furnace 3280 Cast iron melts 2786 Gold ,, 2016 Copper ,, 1996 Silver ,, 1873 Bronze ,, (copper 15, tin i) 1750 Brass ,, ( 3, zinc i) 1690 i> ,, ( 2, 2) 1672 Bronze ( 7, tin i) 1534 ( 3. !) 1446 Metal, dazzling white heat (Pouillet) 2732 white 2552 ,, dark orange ,, ,, 2012 ,, cherry red ,, 1652 ,, dull red ,, 1292 incipient red 977 Charcoal burns 802 Zinc melts (Davy 680) Daniell 773 Mercury boils (Dalton) .. .. , 660 Lead melts 612 Steel becomes dark blue 600 ,, ,, a full blue 560 blue 550 ,, purple 530 ,, ,, brown with purple spots 510 ,, ,, brown 490 ,, ,, a full yellow 470 ,, a pale straw colour 450 ,, ,, a very faint yellow .. 430 Bismuth melts 476 Tin melts 442 Tin 3 + Lead 2 + Bismuth i, melts 354 Tin 2 + Bismuth 2, melts 283 Sulphur melts 218 Bismuth 5 + tin 3 + lead 2, melts 212 Wax melts 149 Acetic acid congeals 50 Olive oil ,, 36 Milk freezes 30 Vinegar freezes 28 Mercury congeals .-. 39 492 Appendix. TABLE VII. HYDRAULIC MEMORANDA. A cubic foot of water weighs A ,, ,, ,, contains A ,, inch weighs A cylindrical foot of water weighs A ,, inch ,, An imperial gallon contains An ,, ,, 55 An ,, ,, weighs A column of water 12 in. high, I in. square weighs .. A ,, contains A ton of water contains " j> Cubic feet X 6 (nearly exact) Gallons X "16 Expansion of water heated from 40 (its point of greatest condensation) to 212 Expansion of water in freezing 62'32lb. 6 ' 232 gals. 03616 Ib. 48'961b. 0284 Ib. 277-274 cub. in. 16045 cub ' ft- 10 Ib. 434 Ib. 0434 gal. 35 '84 cub. ft. 224 gal. = gaL = cub. ft. I in 24 I in 12 TABLE VIII. QUANTITIES RELATING TO PIPES. Diameter of Pipe (inside measure). Gallons per foot. Weight of Cast Hot Water Pipe, each 10 feet in length. inches. * gallons. 0084 Ib. I OIQI I 0339 I* 0529 K| 0764 2 1358 54 4 '2122 3 3056 81 4 '5433 109 5 8490 6 I -2226 8 2-1762 10 3-4010 12 4-9 If the decimal point is removed one place to the right, the number will be gallons per 10 feet ; if point be removed two places to the right, it will give gallons per 100 feet. Appendix. 493 TABLE IX. WEIGHTS OF ROUND IRON. (Compiled by Messrs. J. E. & S. Spencer, London, and published in the Correspondence Columns of The Ironmonger.} To arrive at the Weight of a Tube, the difference between the weight of a solid bar of the outer and inner diameter will give the weight. Example: A tube 4 inches external diameter, 3! inches internal ditto (sub- stance of metal \ inch.) Weight of 4 inch iron 41-888 Less weight of 3^ inch iron 32*071 Weight of tube mentioned 9-817 Diam. Weight. Diam. Weight. Diam. Weight. Diam. Weight. Diam. Weight. i 4 164 ft 2-457 I 7*455 2|f I5-I58 3* 25-566 A 207 I 2*618 Ifi 7-734 2 T V i5'555 3* 26*080 T 5 2 5 6 *$ 2*784 If 8*018 HI 15-956 3T 3 26-599 H 309 irV 2-955 III 8*307 2i 16*362 3^ 27-123 1 368 'A 3-132 HI 8*601 2il 16-774 3i 27-653 H 432 I* 3-3I3 III 8*900 2 T 9 a 17-191 3A 28-187 TV 'SOI I* 3-500 H 9*204 2|| 17*613 3 T 5 28-726 ft* *575 I T 3 6 3-692 ill 9'5i3 2f 18*040 3ii 29'27I ft 6545 t 3*889 ' 9-828 2|i 18*472 31 29*821 tt 738 Ii 4-091 i 10*147 2i^ 18-909 3M 30*375 T 9 e 828 ly-f 4*298 2 10-472 2 19-351 3-^e 30*935 H 923 I* 4'5io 2sV 10*802 2f 19-799 3M 3I-500 1 1*023 Hi 4*727 2 T V 11-136 2|f 20-251 34 32*07I 11 I-I28 if 4-950 a* 11-477 20*709 3H 32-646 tt 1-237 iM 5-177 a* 11*822 Ht 21*172 3T 9 a 33-226 II I-352 IT'S 5*410 a* 12-172 2| 21-639 3if 33-812 f 1-473 1 5-648 *A 12*528 2|| 22-112 3ff 34-402 U I-598 I* 5-890 2^ 12*888 2if 22*590 311 34-998 H 1-728 * 6*138 2i 2M 23-074 3tt 35-599 11 1-864 'T 9 6*392 A 13-624 3 23-562 311 36-205 7 8" 2-004 lit 6-650 2 T 5 a 14*000 3A 24-055 31 36-816 If 2*150 If 6-913 2H 14-381 3A 24-554 311 37-432 H 2-301 I|* 7*182 2| 14*767 3A 25-058 3lt 38-053 494 Appendix. TABLE IX. Continued. Diam. Weight. Diam. Weight. Diam. Weight. Diam. Weight. Diam. Weight. 3tt 38-679 41 62'2l8 5lf 91-326 6lf 126-001 711 166-246 31 39*311 4M 63-019 5tt 92-295 6fi 127-139 8 I67-552 311 39 '948 4H 63-824 5M 93-267 7 I28-282 8^ 168-864 3tt 40-589 4H 64-634 6 94-248 7^ 129-430 8 T y 170-180 3H 41-236 5 65-450 6^ 95-232 7 T V I30-583 8A I7I-502 4 41-888 5A 66-271 6 T V 96-222 7A I3I-74I 81 172*829 4A 42'545 5^ 67-096 6^ 97-2I6 7i 132-904 8* I74'l6l 4 T V 43-207 5A 67-927 6| 98-216 7* 134-072 Mr 175-498 4^ 43-875 51 68-763 6^ 99-221 7^ 135-246 ** 1 76 ' 840 41 44'547 5A 69-605 6 T \ 100-231 1-h 136-425 i 178-188 4A 45-224 5 T 3 6 70-45I 6^ 101*246 7i 137-609 *A 179-540 4 T 3 e 45-907 5ft 71-302 6i 102-266 7A 138-797 *& 180-898 4ft 46-595 5* 72-I59 6^ 103-291 7 T 5 6 139-991 811 182*260 4i 47-288 5ft 73-020 6 T 5 a 104-321 m I4I-I90 8f 183-628 4<& 47-886 5T 5 * 73-887 6H I05-357 71 I42-395 8H 185-001 4A 48-689 511 74-759 6| 106-397 7il 143-604 8 T V 186-379 4M 49-397 5t 75-636 *H 107-443 7^ 144-818 8H 187-762 41 50* no 5 76-5I8 6 T V 108-494 7M 146-038 81 189-150 4H 50-829 5^ 77-405 6M 109-549 7i 147-263 811 190-544 4^ 5I-552 5M 78-297 6i IIO-6II 711 148-492 8 T 9 a 191-942 *H 52-281 Si 79-194 ^H 111-677 7T 9 6 149-727 8H I93;346 41 53-016 5K 80-097 6 T 9 e 112-748 7lf 150-967 8| 194-754 4ri 53*753 5Ta 81-005 6H 113-824 71 I52-2I2 811 196^168 4 T 9 * jj^ 0*972 Copper 8*950 Steatite .. .. 2*800 Coral 2*680 Steel .. .. 7*810 Glass, flint .. .. .. .. 3 -330 Sulphur .. 2*050 Gold .. .. 19*340 Tellurium .. 6*650 Graphite .. .. 2*300 Tin Gun-metal 8*460 Titanium.. .. 5'3oo Tungsten . . . . 17*600 Iridium 21*150 Uranium.. .. 18*400 Iron, cast 7*210 Wood, ash .. 0*845 wrought 7*840 beech .. 0*852 Ivory .. 1*920 elm .. 0*800 Lead 11*360 cork .. 0*240 Lime 3*i8o Zinc 7-146 Lithium 0*593 Zircon .. .. 4'3oo Magnesium 1*743 TABLE XII. SPECIFIC GRAVITIES OF LIQUIDS. WATER AT 39*2 F.= i -ooo. Ammonia (solution) .. .. 0*875 Naphtha .. .. .. 0*860 to 0*900 (liquid) 0*730 Oil, almond (59 F.) .. .. 0*918 Beer 1-023 to 1*034 ,, castor 0*969 Benzol (C 6 H 6 ) 0*850 cod-liver . . 0*928 Bromine (at 32 F.) .. .. 3*187 linseed (53 F.) .. .. 0*939 Cyanogen (liquid) 0*866 olive .. .. 0*918 Essential oil of bitter almonds 1*049 Tar .. I '120 to '150 turpentine .. 0*864 Water, distilled *ooo Hydiochloric acid (liquid) .. 1*270 rain .. *OOI (solution) .. 1*210 sea *026 Mercury (at 32 F.) .. .. 13*596 Wine .. 0*990 to -038 Milk 1-030 2 K 49 8 Appendix. TABLE XIII. SPECIFIC GRAVITIES OF GASES AT 39- BAROMETER = 29-9 INCHES. F. Air = 1*000. Air l ' '4*40 Aqueous vapour 0*633 Ammonia 0*589 8-50 Azote 0-972 Carbonic acid 1*529 22*80 oxide 0-967 14-00 Carburetted hydrogen, heavy 0*978 14*00 light 0*557 8*00 Chlorine 2*470 35*50 Coal gas, about 0*500 Hydrochloric acid 1*247 18*25 Hydrogen 0*069 1*00 Nitric oxide 1*039 I5*oo Nitrous I'S 2 ? 22*00 Nitrogen 0*971 14*00 Oxygen 1*105 l6 ' Sulphurous acid 2*247 32*00 TABLE XIV. LINEAR EXPANSION OF METALS BY 180 OF HEAT, THAT is FROM 32 TO 212 FAHR. LENGTH OF A BAR AT 212, WHOSE LENGTH AT 32 IS 1*000000. Bismuth .. .. Brass .. .. Copper .. Gold .. .. Iron , soft forged " -,1, round, wire-drawn cast.. Lead 00139167 00185540 00172244 00151361 00125833 00122045 00123504 00110940 00286700 Pewter, fine .. .. .. '00228300 Platinum '00085655 Silver '00190868 Solder (lead 2 + tin i) .. -00250800 Spelter (brass 2 + zinc i) '00205800 Steel, untempered.. .. '00107875 ,, tempered yellow "00123956 Tin, English '00217298 Zinc '00294200 Appendix. 499 HIGH-PRESSURE HEATING. This mode of heating was introduced in a practicable form, in fact invented, by A. M. Perkins in 1845, a patent having been granted him in that year. His name has become so associated with the apparatus, that it is now more commonly known as Perkins' System than by any other title. No one has brought it to such a degree of perfection, nor adapted it successfully to so many uses as the firm that bears the inventor's name (A. M. Perkins & Son), and it is worthy of note that many of the apparatus erected so many years ago, are now in use and doing good service. The firm still carries on business, and continues to carry out the principles of the original invention. WARMING BUILDINGS BY HEATED AIR. In warming buildings or apartments by heated air, when the quantity needed is large and requires to be frequently changed (as in Fig. 200A. M7J Turkish Baths, Public Halls, Drying Rooms in Manufactories, &c.), it becomes necessary to propel the air by mechanical means. 2 K 2 500 Appendix. Fig. 200A* illustrates the Blackman Air Propeller or Fan. This is one of the most efficient of these appliances, and apart from the efficacy that is gained in proportion to size, it can be regulated in speed so as to propel a large volume of air without disagreeable sensations of draught. In this respect diffusion is a better word than propulsion, as this latter would apply more correctly to the older forms of air pumps that were used for this purpose. With these no such agreeable result could be obtained without considerable pains and expedients. When this fan is used in conjunction with heating works, it is placed in a brick passage and causes the warmed air to flow through the conduits in a steady stream, with scarcely perceptible draught, although the volume delivered is all that could be desired. The utility of these fans is further referred to under Ventilation. WARMING BUILDINGS BY HEATED AIR. Fig. iQ7f represents the "Gurney" Stove, placed in a vault to warm the air supply of a building. The Gurney stove embraces in a most successful and practical manner the utility of gills or flanges attached to heating surfaces. Reference has been made in several places to the particular gain effected by these additions, but nowhere can they be referred to with such opportunity of explaining their good effect as here. Let it be imagined that quite half of the air introduced into a building upon this system has to pass through a stove chamber, and in this space is a stove with nothing but a plate of iron between the glowing fuel and the air to be warmed. This must result in the air being rendered much too dry for at least comfortable respiration, and in addition, a surface at this heat scorches and perhaps carbonises all particles of solid matter that settle upon it. As our air is always laden with dust, chiefly organic matter, the result is an odour of an unpleasant and stuffy character. In certain places, as Turkish Baths, &c., these features are nothing, but when a residential building, or a church, or closed * From the Catalogue of The Blackman Ventilating Company, Fore Street, London. f From the Catalogue of The London Warming and Ventilating Company, 105 Regent Street, London. Appendix. public place is so heated, complaint must occur. With a gilled stove, having the lower ends of the gills dipping into a water trough, all these disadvantages cease to be, and we can neither get a dis- agreeably high temperature to the heating surfaces of the stove (see page 8) nor a dryness of the air. This stove (a battery of them) has Fig. 197. the reputation of successfully warming St. Paul's Cathedral when all other attempts had failed. The Gurney stove is made for use in exposed positions for ordinary warming purposes, as well as in stove chambers for heated air works. Its sizes vary from 5000 to 120,000 cubic feet, these figures denoting the area a single stove is capable of heating. EXAMPLES OF HORTICULTURAL WORKS. Perhaps the most simple form of apparatus that is ever erected in connection with a boiler heated by solid fuel, is as Fig. 56.* This is simply a flow and return service run along the side of a greenhouse as shown. It is very useful and much in demand for amateurs' works, * The " Loughborough " Boiler, from the Catalogue of Messenger & Co., Loughborough. Appendix. as the pipe-joints are simply made by unskilled hands. By the addition of bends the pipes can be carried around two or more walls of the house as required. Fig. 56. SILICATE COTTON. Messrs. D. Anderson & Son, of Bow, London, and of Belfast, furnish this material. The price averages i2s. 6d. per cwt. or io/. IQS. per ton. A ton gives a covering capacity of about 1800 square feet, one inch thick. INDEPENDENT BOILERS. Fig. I02A* is the improved "Severn" Boiler, a very effective form of vertical independent boiler, it having, in addition to the customary water-way sides and top, an intervening water-way bridge that the flames and heated gases impinge upon. In addition there are a series of vertical tubes in a flue chamber behind as shown. A. bridge or any device of this kind which intercepts the free exit of flame has a pronounced effect in increasing a boiler's efficacy. Flame, as has been explained elsewhere, has a decided tendency to avoid con- tact with surfaces if it can, and flame without contact does very little useful work. The tubes behind, lying as they do directly in * From the Catalogue of Mather & Kitchen, Derby. Appendix. 503 the path of the escaping heated products, add very greatly to the effectiveness of the boiler, utilising what would otherwise be waste heat Fig. 1 02 A. Fig. 96A. INDEPENDENT BOILERS. Fig. 96A* is the " Very " Boiler, which can either be used in an independent character, or fixed in the thickness of the greenhouse * From the Catalogue of Jones & Attwood, Stourbridge. 504 Appendix. wall. The position of the pipe holes is very ingenious, and in the majority of cases must prove of greater convenience than top or back connections. This boiler has no water-way to the front, and there is really little value in having it if it is to be exposed to the weather. If fixed in the thickness of a wall, the front would very probably be exposed in this way. BOILERS FOR BRICK SETTING. Figs. 137 and 138* illustrate a somewhat unique form of horticul- tural boiler, it so much resembling a multitubular boiler such as is used for steam generation. It is a most effective type of water heater, as in addition to the cluster of tubes through which the heat Fig. 137- products pass when first leaving the fire box, there is a range or saddle of about 14 tubes which fulfil the part of a return flue. This double arrangement of tubes presents a really great area of effective heating surface, and apart from the rapid results obtained, it effects an economy in space which is frequently valuable. It will be seen * From the Catalogue of John Bellamy, Byng Street, Millwall, London. Appendix. 505 that the tubes do not interfere with that very necessary feature in horticultural works, viz. the ability to bank the fire so that it will go the night without attention. The setting of this boiler is very simple as shown. Fig. 138. BOILERS FOR BRICK SETTING. Fig. 140* is the " Chilwell Nurseries " Boiler (Foster & Pearson's patent). This is a horizontal tubular boiler, consisting, as shown, entirely of tubes, fastened into box ends, the flames and heated gases circulating through and around them. Theoretically, and to a great extent practically, no more effective boiler can be made than one of tubes. Boilers for steam generation and boilers for every other known purpose when required to be highly effective are invari- ably provided with tubes, either tubular flues or tubes containing water. The advantage is in the fact that a tube is all heating surface. Any other form of heating surface has usually some part idle, but not so with a tube which is effective from end to end. Notwithstanding this, tubular boilers (consisting entirely of tubes) are not so largely used as would be expected. It is not due to any * From the Catalogue of The Beeston Foundry Company, Limited, Beeston, Notts. I i fi Appendix. 507 recognised fault, and no hesitation need be felt in recommending or using them. Doubtless they have suffered at the hands of unskilled fixers, for perhaps this form of boiler more than any other, is liable to suffer in this way. It is very necessary that a tubular boiler be set upon a good principle to render it effective. This means that the fixer should be skilled at his work and know (as skilled boiler fixers do) what is the effective action of flame and heated gases, as well as of radiant heat from the glowing fuel. In the hands of a good setter every boiler is at an advantage, but a tubular boiler is especially so. Good work with these yields very excellent results. The particular boiler being referred to gives every opportunity for good results to be obtained, as it is made in two sections with the middle bridge provided. In many such boilers the bridges and deflecting feathers have all to be planned out and built by the fixer, which calls for much skill. This is a cast-iron boiler, and the illustration shows the method of fixing. PIPE JOINTS. A good form of expansion joint is Richardson's patent, as shown in section at Fig. 146.* The lengths of pipe have specially formed ends which, when clipped together, compress an india rubber collar Fig. 147. ^rfc*" Fig. 146. between them as shown. Only one collar is needed, and a very sound joint is effected capable of withstanding pressure. * From the Catalogue of The Meadow Foundry Company, Limited, Mans- field, Notts. 508 Appendix. PIPE JOINTS. Another form of expansion joint expressly adapted to withstand high pressure, is Jones's patent, Fig. 147.* The illustration makes detailed explanation unnecessary. PIPE JOINTS. Fig. 148 | is Messenger's Pattern Expansion Joint, differing from the others in detail, but of similar effectiveness and capable of bearing pressure when required. All joints, which necessitate Fig. 148. special end castings to both ends of the pipes, prevent cutting or shorten! Q on the job, but all lengths are kept in stock by the different makers to fulfil any requirement. RADIATORS. Fig. 170 J shows another form of ventilating radiator, introducing the use of ribbed or gilled pipes as illustrated. The air passage is between the front and back rows of pipes, with outlet at top and suitable provision for inlet at bottom. The inlet of fresh air is provided for by a passage cut through the wall and fitted with air- brick, as usual. The utility of the gills or external ribs to the pipes has been referred to (page 8, Fig. i). They practically extend the radiating surface as explained. * From the Catalogue of Jones & Attwood, Stourbridge. t From the Catalogue of Messenger & Co., Loughhorough. j From the Catalogue of The Beeston Foundry Company, Limited, Mans- field, Notts. Appendix. Fig. 170. 509 Fig. 171. 5 1 o Appendix. RADIATORS. Fig. 171 * is a neat pattern radiator, made in all sizes like others. It is a somewhat severe design, as illustrated, but lends itself well to decoration. It is capable of very good treatment in this way. They can be had fitted with marble or ornamental tops if required, and certainly, for reception rooms in residences the expense of marble tops is well repaid in the good appearance obtained. The section of the pipes is a good one, admitting of rapid results being attained, as they hold but a limited amount of water. RADIATORS. Fig. i72Bf is one of Korting's patent gilled pipe radiators. The plan of these admits of their being made in any length ; in fact, an Fig. I72B. engineer could stock the sections and make them up as required. They can be had with the gills of square shape as shown, or oval. The makers also supply gilled pipes for horizontal work. * From the Catalogue of Longden & Co., 447 Oxford Street, London ; and Sheffield. t From the Catalogue of Korting Bros., 86 Queen Street, London, E.G. INDEX. Absorption of air by water which varies in temperature, 37 of heat, 10 Action of flame against cool surfaces, H3 Air cocks, 51, 260 Air in boilers, 36 in pipes, 47 its interference with the cir- culation, 47 its lodgment in horizontal pipes, 49 occasional difficulty of dis- lodgment, 48 Air tubes, 49 necessary precautions in erecting, 49, 50 Air vents, 260 example positions, 82, 83, 84 Apparatus for building works : dis- tinction from horticultural works, 254 heating two glass-houses upon different levels, 80 Appendix, 489 Appliances for horticultural works, 217 Area of fire-bars, 155 Atmospheric moisture, 26, 130, 273, 489 affected by hot-air apparatus, 315 B. Ball valves, 98 Banking up boiler furnaces, 250 Blow-off cock, 195 Boiler flues, ill effects of soot and dirty flues, 141 size of, 190 Boiler flues, value of flame, 141, 184 pits, 195 Boilers, 133 action of flame in flues, 17, 141 air in, 36 area of heating surface, 138 of fire-bars, 152-155 cast-iron, 213 Vt wrought-iron, 151 charging with fuel, 100 cleaning, 195, 211 provision for, 172-176 "Climax, "203 Colonial, 202 copper, for domestic hot-water works, advantages of, 346 Cornish, 215 "Delta, "205 domestic hot-water supply, 341 Excelsior, 206 1 heating surfaces, direct and in- direct, 133 Hood's standard value of heating surfaces and its features, 138 Hood's suggestions, 135, 136, 138, 139 "Imperial," 204 independent, 156 care in fixing, 100 necessary in fixing gas boilers, 163 cast-iron, and their advan- tages, 177, 178 Challenge, 178 chimneys to gas, 165 coal and coke burning, 167 coil, 169 - dome-top, 175 Finsbury, 170 Index. Boilers, independent, Fletcher's gas, with flame contact studs, 160 upright gas, 161 for domestic hot-water works, 35 horseshoe, 171 Ivanhoe, 174 Keith's gas, 162 Loughborough, 170 non-use of outer surface, 156 objections to gas, 165 precautions with gas, 166 saddle, with terminal end and cross tube, 176 with water-way ends, 176 Star, 167 Toope's, and apparatus for window conservatories, 159 gas, 158, 159 Viaduct, 1 80 kitchen, cleaning out hard deposit, 338 Loughborough, 97 low-pressure, for kitchen ranges, 431 makers' lists based upon Hood's standard value of surfaces and the allowance needed, 138 : man-lids for kitchen-range, 348 necessary features in ordering, 102 new standard value for heating surfaces, 145 particular efficiency of direct- heating surfaces, 136 provision for cleaning, 148 " Python," 213 regulation of draught, IOI relation of fire-bar area to the radiating surfaces, 153 saddle, 136, 182 building arch over, 196 ' capabilities of, 139 its advantageous features, 184 method of setting, 185 suggested square-shape, 183 with top flue, 201 with top flue and water-way ends, 202 Boilers, saddle, with water-way ends, 137, 199 with water-way feathers, 192 setting, securing furnace front, 197 several small, in preference to a less number of large ones sometimes preferable, 90 shallow drainage, 118, 150, 204, 205 size of chimneys, 457 size of water-way, 147 stoking and attention, 135, 249, 250 suited for building works with heavy pressure of water, 257 thickness of plate, 152 top feeders lessen efficiency, 140 to prevent kitchen, rusting, 341 Trentham, 215 upright, 137 value of flue surface, 184 of indirect heating surface, compared to direct, 140 WagstafFs, 207 water-way below fire-bars, 172 Weeks' tubular, 210 with cross tubes, 200 Boiling-point of water wholly governed by pressure, 301 Box ends, 112, 113 Branch services, 107, 121 Brick-setting to boilers, 185-216 Bridge, fire-brick, at back of boilers, 188, 194 Building Act, The, its application to hot-water and hot-air works and chimneys, 477 Amendment Act, 483 Building works, 254 ' example apparatus, 280 example apparatus to heat a church, 300 example of apparatus to heat a large room or hall and another room j the boiler situated centrally, 286 example apparatus to heat four floors of a warehouse or other building, 294 Index. 513 Building works, example apparatus to heat one small room from a coil in a fire-grate, 280 example apparatus to heat three corridors above each other, 291 example of apparatus to heat two radiators in a hall or room with an independent boiler, 285 C. Calculating table for ascertaining quantity of pipe in building works, 277 Calculations to obtain quantity of pipe for horticultural works, 238 Causes affecting circulation, 87 Channel pipes, allowance for, 245, 279 Channels, pipes in, in, 114, 120 Chimneys, 452 cold air passing in, ill effect of, 455 common faults in fixing portable stoves, 458 defective draught, 454 descending from stoves beneath floors, 463 down-draught, 459 draught, cause of, 453 faults in, 461 pilot stoves, 464 sizes of, for boilers, 457 for fire grates, 458 smoking : causes of, 460 to gas boilers, 165 to horticultural boilers, 146 velocity of draught (table), 490 Circulating below the boiler, 74 experiments with a model apparatus, 76 Hood's theories and suggestions, 77 into tank, 79, 8 1 Circulation of water, 28, 331 action if both pipes start level, 71 causes of erratic results, 91 causes retarding circulation, 87 Circulation of water horizontally from side cf boiler, 70, 97 effected by slightest differ- ence in temperature, 35 friction, 87 friction, the writer's views, 62 Hood's theory, 30 its governing principle, 42, 43 its relationship to convection, 28 motive power, 32-35 causes varying, 32 theoretic table, 33 obstacles in pipes, 91 practically no limit as to distance, 89 retrograde or reversed circu- lation, 65, 68, 69 reversed circulation, 92, 93 Tredgold's theory, 28 uncertain results, 94 velocity, 62, 89 Cleaning boilers of "fur," 338 horticultural boilers, 172, 173 Coal, 247 Coil boilers, 169, 208 boiler, in high pressure apparatus, 302 cases, 266 Coils, 265-268 beneath floors, 289) connecting, 267 dust on, ill effects of, 267 jointing, 266 Jones and Attwood's joint, 266 objections to, 266 Coke, 248 Combustion, 439 action of, in grates, 441 carbonic acid and oxide, 449 effect of bitumen in coal, 449 hot water pipes v. grates, 441 hydrogen, its effect and products, 451 ' imperfect in grates, 441 peculiar action in Dr. Arnott's grate, 442 Index. Combustion, peculiar wasteful action in thick fires, 449 phenomenon of, 448 products of, 449 in gas boilers, 163, 164 Condensing stoves, 164 Conduction of heat, 3 diffusion; its peculiarities, 8 its action, 5 , its importance in these works, 6 non-conduction, 7 -=- poor conductors of heat and their uses, 121, 386 where poor conductors needed, 6 Conductive property of fluids, 3 properties of solids, 4 Connecting pipes to boilers, 36 . distance between floor and return pipes, 73 Conservation of heat, 120, 157, 319, 382 Convection of heat, 17, 331 r accounts for draughts in chimneys, 27 as opposed to conduction, 17 -. experiment to determine, 18 governed by mobility of fluid, 23 its action determined and illustrated, 19 its application to liquids and gases, 1 8 its application to the atmo- sphere, 24 its effect upon atmospheric moisture, 26 its peculiar molecular action, 17 Cool house, 123 Copper boilers for domestic hot water supply, 346, 347 Covering boilers, 157 pipes for the conservation of heat, 382 =r-m to conserve heat, 120 Cross tubes, 177 D. Dampers, 101 self acting, 172, 214 Deposit, hard, in boilers, cause and effect, 334 in boilers, 148 its removal, 150 in pipes, 56, 57 Descending circulation, 74-81 Diffusion of heat, 316 Dipped pipes, 60-69 means of ascertaining possi- bility of, 6 1 Dirt deposit in pipes, 56, 57, 105 Draught in chimneys, 27 (horticultural), 153 Duplicate services, 89 Dust on radiating surfaces, 253 Eccentric results, 91 Evaporating pans, 273 Example apparatuses ; irregular forms, 60 Examples of horticultural apparatus, 96 Expansion box, 57, 98 joints, 58, 225-229 of air and gases by heat, 490 of metals by heat, 498 of pipes by heat, 57 of water by heat, 52, 54, 304, 491 pipe, when needed, 260 tube or chamber, in high pressure apparatus, 303 Expansive force of heated pipes, 58, 59 Exposed pipes, 7 F, Faults, 91 Feathers, position of in flues of saddle boiler, 189, 191 Fire bars, area of, 152-155, 187 water, 198 '- bricks, 6 grates, 439 Fittings for horticultural works, 217 Fixing boilers, 185-216 Flame, action of, 141 Index. 515 Flame contact: theory of, and Mr. Fletcher's application, 142 heats by contact only, 141 peculiar action of, 17 Floors, coils beneath, with gratings over, 289 Flow and return pipes, arrangement of, 93 best position for the vertical portion of the return pipe in horticultural works with low motive power, 41 branch services, 107, 121 different suggestions as to direction of pipes to assist motive power in horticultural works, 42-46 ' duplicate services, 89 multiple services, 216 point at which one ter- minates and the other begins, 40 position of flow as re- gards the return, 39, 40 Flow pipe, point for connection, 36 - rise in, necessary, 38 two or more flows, 37 vertical, as far as possible, 37 Flue cleaning, 251 Flues, boiler, size of, 190 to boilers, 136 to saddle boiler, method of making, 193 Forcing house, 12 1 pits, 128, 129 Fractured boilers, 38, 335 Friction of water in pipes, 87, 88 Frost, 251, 308, 425 Fuel, 247 size of, 101 =* waste of, 253 Furnace bars, area of, 152-155 fittings, 234 Furred boilers, 334 Fusible plugs, 429 G. Gas boilers, 158-162 stoves, condensing, 164 Gilled pipes, 8, 264 Gill stoves, 316 Grape house, 122 Grates, Dr. Arnott's principle, 442 features sought to be attained in modern, 443 fire bricks an essential feature, 443 *- good effect of a blower, 450 heat radiation and heat deflection by the frfe bricks, 447 imperfect combustion of fuel in, 441 shape of the back brick and its importance and effect, 445 Shorland's radiating, warm air and ventilating, 321 slow combustion, 441 Greenhouses, 123 H. Hard water, cause of hardness, 334 = its effect upon boilers, 334 peculiarities of, 335, 336 prevents boilers rusting, 340 Heat, i absorption, 10 conduction, 3 conservation of, 120 convection, 17 diffusivity, 8 effects of, 492 loss of, 382 radiation, 9 reflecting powers, id transmission of, 3 Heated gases, effect of, 16 peculiar action of, 17 Heating air by hot-water pipes, 325 buildings, 254 by warmed air, 313 surfaces, new standard value for, 145 of boilers, value of, 138 to boilers, 133 Heating up, time occupied in horticul* tural works, 243 High pressure apparatus, examples, 302, 311 Index. High pressure apparatus, its principle and application, 301 jointing pipes, 305 method of modifying or regulating the pressure and tem- perature, 310 size of pipes, 305 utilised for bread baking, 312 utilised for drying rooms and for japanning-ovens, 308 utilised for ventilating purposes, 307 Horticultural apparatus, chimneys, 146 examples, 96 example for a conservatory, 106 for five houses adjoin- ing, with melon pits, 116 for several houses, with boiler placed between them, 125 for small conservatory, 99 for small greenhouse, 97 for two glass houses adjoining, 109 necessity of moist atmosphere, 130. 131 Hot-air apparatus, 313 affecting moisture of atmo- sphere, 315 Constantine's stoves, 323 decomposition of organic matters present in the air, 313 example stove and heating chamber, 314, 317, 320, 321, 324 heating air by hot-water pipes, 325 heating an entrance hall by air passing over a small gill stove, 328 inlets for the warmed air, 327 Musgrave's stoves, 319 possible ill results, 313 ventilation absolutely neces- sary, 326 Hot air conduits, 317 Hot-house, 121 Hot-water pipes, 217 Hot-water pipes and fittings, list of, 218 works, domestic, bath fittings, 380 boilers, 341 circulation, 331 coil for linen closet or for airing towels from domestic supply apparatus, 415 coils or radiators con- nected to domestic supply apparatus, 409 cold -supply service, connection and size of, 363, 368 conversion of a tank to cylinder apparatus, three methods, 387 copper boilers, 346 cylinder, position of, , pressure upon, 365, 369 cylinders and tanks, sizes of, 372 cylinder system, 364 difference between cy- linders and tanks in resisting pressure of water, 370 different features no- ticed from experiments, 396 earliest form of appa- ratus, 332 emptying service to cylinder system, 368 expansion pipe, 361, 366 faults and sources of danger, 418 fitting high - pressure boilers for temporary low-pressure purposes, 431 flow and return pipes, and connecting same, 356, 365 frost, 425 furred pipes, 377 importance of covering pipes to prevent loss of heat, 382 independent boilers, advantages gained by using, 352 1 low-pressure boilers, 431 Index. 517 Hot-water works, domestic, man-lids and packing, 349 . modified forms of cylin- der apparatus, 402, 403 peculiarities, 395 pipes, suitable sizes of, 376 precautions needed with lead pipe, 374 returned draw-off ser- vices, 360 rising main service, or secondary flow, 366 safety valves, 427 secondary flow and re- turn of cylinder system, 366 self-filling apparatus for range boilers, 433 shower-bath apparatus, 38i tank system, 355 taps, pipes, and fittings, 372-382 twin boilers, 391 water supply to low- pressure boilers, 433 H -pieces, with valves, 124 Hydraulic memoranda, 493 Incrusted deposit of lime from hard waters, 334 Independent boilers, 156-181 covering needed, 7 Indiarubber jointing material, 225-229 Irregular forms of apparatus, 60 J. Jointing pipes, 222-229 another expansion joint, 228 Fisher's patent joints, 229 high pressure, 305 Jones and Attwood's joints, 227 K. Kinetic theory of heat, 2 Lime as a rust preventative, 340 (bicarbonate) in water, 334 deposit from hard water, 334 List of cast pipes and fittings, 218 of wrought pipes and fittings, 263 Loss of heat from independent boilers, 157 M. Main pipes, 116, 125 advantages of several, 296, 297 for building works, 258 sizes of, 118, 119 vertical, suggested objection to, 295 Man-lids for kitchen range boilers, 348 packing, 349 Material theory of heat, I Melon pits, 116 Mobility of fluids, 23 Moistness of atmosphere, 273, 489 affected by hot air apparatus, 315 Motive power, governing sizes of pipes, 259 in building works, 258 low in horticultural works', 35 N. Noises in pipes of domestic supply apparatus, 423 O. Obstruction in pipes, 91 Overflow pipes, 53 Overheating, 250 P. Packing man- lids, 349 "Feet's "stop valve, 275 Perkins' high pressure system, 30?! Pipe bearings, 58, 103 joints, 58, 222-229 Pipes, cast, for horticultural works, 2iJ 518 Index. Pipes, cast, gilled, 264 list of, 218 decorating when exposed in build- ings, 261 difference in heating properties between large and small radiating pipes, 88, 89, 298 dipped and carried beneath obstacles, 60 domestic hot water supply works, 372 evaporating trough, 130 gilled radiating pipes, 8 in channels, in, 114, 120 or trenches, allowance for, 245> 279 mains, 116 obstruction in, 91 r position of, 123 size of, 121, 124, 259 weight of, 217 Pipes and fittings, wrought, for building works, 262 _* _, qualities of, 262 Pits, for melons, &c., 116 for pine apples, &c., 128 Planning horticultural works, 96 care needed, 91 Poor conductors of heat, 121 Pressure and temperature table (water), 309 effect of, upon the boiling-point of water, 301 of water, 255 alike with any sized pipe or any quantity of pipes, 255 in pipes, 369 Products of combustion from gas boilers, 164 Quantities for building works, 277 Hood's original rule and its effect, 277 for horticultural works, 238 table, Hood's rule and its applica- tion, 238 rapid, 241, 245, 277 R. Radiation of heat, 9 action, 9 clean surfaces, 253 dark rays, 1 1 direction of rays, 15 effect of atmosphere, 13 of colour, 1 1 of water vapour, 13 its chief peculiarity, 14 luminous rays, II polished v. unpolished sur- faces, 10 re-radiation, 15 tables of radiating power of substances, 10 theory, 9 what part of the substance effects this, II Radiators, 268 "Cannon's" patent (single and ventilating), 269 Heaps' patent, 271 ornamental pattern, 270 Sanderson's patent, 271 the " Universal," 269 ventilating, 273 Rapid calculating table for quantities of pipe in building works, 278 for horticultural works, 245 Reflection of heat, 10 Retrograde circulation, 65 Return pipe, descent in, 39 duplicate returns, 38 position of, 94, 189, 192 Reversed circulation, 65 Ring expander, 226 Roller bearings for pipes, 58 Roots of vines, shrubs, &c., 132 Rust, opposed by lime in the water, 340 Safety valves, 427 Saturation of atmosphere, 130 Self-acting damper, 172 Setting boilers, 185-216 Shallow drainage, 150 Index. 519 Silicate cotton, 319 Sizes of main pipes, 119 Slide valve, 231 Smudge mark above heated pipes, &c., 274 Soot doors, 237 wasted fuel, 441 Specific gravities of solids, liquids, and gases, 497, 498 Stoking, 100, 135, 249 Stop cocks, 229, 275 valves, 95, 113, 229, 274, 275 Stoppage in pipes, 91 Strain exerted by pressure of water, 255 Supply cisterns, position, size, &c., 52, 53,54 useful form for small works, 57 Supply service between cistern and pipes, 55 Supports for pipes, 103 T. Tables: conductive powers of sub- stances, 4 corresponding degrees of Centi- grade and Fahrenheit thermometers, 497 effects of heat, 492 expansion of gases by heat, 490 of water by heat, 491 force exerted by steam or water in confinement and above 212 tempera- ture, 489 hydraulic memoranda, 493 linear expansion of metal by heat, 498 of quantities for building works, 279 quantities for horticultural works, 238, 245 quantity of vapour in atmospheric air at different temperatures, when saturated, 489 quantities relating to pipes, 493 specific gravities of gases, 498 Tables : specific gravities of liquids, 497 of solids, 497 gravity of water at different temperatures, 491 temperatures for pressures (steam or water), 489 to ascertain weights of tube, 495 to convert one thermometric scale into another, 497 velocities of chimney draught, 490 Tank apparatus (heating), 79, 81 Taps, draw off, 378 Thermometric scale, 497 Throttle valves, 95, 230, 231 Trenches, pipes in, in, 114, 120 Trench pipes, allowance for, 279 Tropical house, 12 1 Trough pipes, 130 245 TT. Uncertain working of an apparatus, 91 V. Valves, 95 and cocks, 229 in branch services, 122 in H piece, 124 regulating, for high pressure system of heating, 310 Ventilation, 465 methods, 468 necessary with hot air works, 326 position of inlets, 475 quantities table, 467 the efficient action of an ordinary fire place, 469 Tobin's tubes, 475 working value of a ventilating shaft, table of, 471 Vine roots, 132 520 Index. w. Warming by heated air, 313 Water, absorbs air in heating and cool- ing, 37 absorption of air by variation in temperature, 91 expansion by heat, 52 pressure and temperature table, 309 pressure exerted at temperatures over 212 when in confinement, 489 Water bars, 198 boiling, pressure governs tempera- ture at which boiling takes place, 301, 429 pressure of, 255, 369 soft, its action, 340 supply to tank apparatus, 86 to hot water works, 52 Water-way below fire bars, 172, 173 Weights of tubes, 493, 494 Wind, its effect upon glass houses, 240 LONDON : PRINTED BY WILLIAM CLOWES AND SONS, LIMITED. STAMFORD STREET AND CHARING CROSS. APPARATUS FOR WARMING AND VENTILATING, &c. SUPPLIED BY THE FOLLOWING FIRMS: PACK ANDERSON, D., & SON, LIMITED .. .. .. .. .. 4&5 BEESTON FOUNDRY Co., LIMITED.. .. .. .. .. 16 BELLAMY, JNO. .. .. .. .. .^. .. .. 24 BOWES SCOTT & WESTERN . . Facing Title CANNON, W. G. . . . . , . . . . . . . . . 20 COALBROOKDALE Co., LIMITED . . . . . . . . . . 6 CONSTANTINE, J., & SON ,. .. .... .. ,. 21 CARTON & KING .. .. .. .. ., .. .. 22 GENERAL IRON FOUNDRY Co., LIMITED .. .. .. .. 9 GRAHAM, WM., & SONS .. .. .. .. .. .. 27 GRAHAM & FLEMING .. .. .. .. .. .. 14 HARTLEY & SUGDEN, LIMITED Facing Half Title and Inside Back Cover JENKINS, R., & Co. .. .. .. .. .. .. ro JONES & ATTWOOD . . , . . . . . Facing Inside Back Cover KEITH, JAS. . . . . . . . . Inside Front Cover and Page Facing KORTING BROS. .. .. .. .. .. .. .. 17 LLOYD & LLOYD .. .. .. .. .. .. .. 23 LONDON WARMING AND VENTILATING Co., LIMITED .. .. 19 LONGDEN & Co. .. .. .. .. .. .. .. 18 LUMBY, SON & WOOD, LIMITED .. .. .. .. .. i MACFARLANE, WALTER, & Co. . . . . . . .. , . 7 MATHER & KITCHEN .. .. .. .. .. .. 15 MEADOW FOUNDRY Co., LIMITED.. .. ,. .. .. 12 MESSENGER & Co. .. .. .. .. .. ... .. 13 MUNZING, H. .. .. .. .. .. .. ,. 8 PERKINS, A. M., & Co., LIMITED . . . . . . . . 2 & 3 THAMES BANK IRON Co., LIMITED .. .. .. .. u 2 M ADVERTISEMENTS. CO 2 M 2 ADVERTISEMENTS. PERKINS' PATENT HOT-WATER PERKINS' PATENT SYSTEM THIS System is safe, economical, effective, simple, durable, and not liable to get out of order, and can be worked without skilled labour. This System has been applied in many thousands of cases in every description of Building, both public and private, during the last 50 years. It can be applied to heating Public Buildings, Churches, Chapels, Schools, &c.; Workshops; Private Houses, large and small, &c., &c. It can be applied to Disinfecting Closets, and Japanning and Drying Closets for manufacturing purposes, where heat up to 600 degrees Fahrenheit is required. It can also be applied for melting substances in open pans or on hot plates. For further Particulars apply to the flDn'gfnal 3|nfjentot#, ^atenteeg anfc Manufacturer^ A, M. PERKINS & SON, LIMITED, 43 REGENT SQUARE, GRAY'S INN ROAD, LONDON, W.C. ADVERTISEMENTS. HEATING APPARATUS. OF HOT-WATER HEATING. THE FOLLOWING ARE A FEW CASES, AMONG MANY THOUSANDS, WHERE PERKINS' PATENT SYSTEM HAS BEEN APPLIED :- Marlborough House. St. James's Palace. Board of Trade. Standard Department. Cambridge University Library. Exeter Cathedral Library. Sir John Soane's Museum. Middle Temple Library. Society of Arts, Adelphi. Mudie's Library. St. George's Chapel, Windsor Castle. Christ Church, Crouch End, N. Christ Church, Bromley, Kent. St. Mary's Church, Hadley, Middlesex. Hove Parish Church, near Brighton. St. John's Church, Putney. Easton Church, Thetford. Sunningdale Church, Berks. Wesleyan Chapel, Beverly Road, Hull. Wesleyan Chapel, Melton Mowbray. Euston Hall, Thetford. Culmington Manor, Salop. Addington Park, Croydon. Skelwith Fold, Ambleside. Elvethan Park, Winchfield. Babworth Hall, Notts. Tredenham House, Farnboro'. Franks Hall, Farningham. Haseley Manor House, Oxford. Nuneham Rectory, Oxford. W. H. Smith & Son, Strand, W.C. Stanford, Charing Cross, S.W. Broadwood & Co., Gt. Pulteney St., W.C. Cow & Co., Streatham, S.W. Mawer & Collingham, Lincoln. Winsor & Newton, Rathbone Place, W. India Rubber, &c., Co., Silvertown, E. Peter Brotherhood, Belvedere Road, S.E. Smith & Son, Stratford. Williamson & Son, Guildford. PERKINS PATENT STEAM OVENS. 43.ReqerU Square Grays Inn Road. LONDON. W.C. ADVERTISEMENTS. D. ANDERSON & SON, L TD BELFAST : Lagan Works. LONDON : 812 Qld Fo^d Bd. ? Bow ? E. GLASGOW: 118 Broomielaw. ADVERTISEMENTS. D. ANDERSON & SON, I -A. T IE 3XT T HAIR FABRIC SPEAKS FOJ* ITSELF As the handiest, cheapest, and most efficient method of using Dry Hair non-conducting covering for Steam and Water Pipes. BELFAST : Lagan Works. LONDON : 812 Old Ford Bd., Bow. B. GLASGOW: 118 Broomielaw. ADVERTISEMENTS. THE COALBROOKDALE CO., LTD., Hydro-Caloric Radiator and Inlet Ventilator FT TT t t t ftEQTIOII 1MML Price List and Heating Surface in superficial feet of PATENT HYDRO-CALORIC RADIATOR AND INLET VENTILATOR For Warming on Low Pressure Hot Water System: 7t Sizes of 2 ft. 8 in. high, including Stand. 2 ft. ii in. high, including Stand. 3 ft. 2 in. high, including Stand. 3 ft. 5 in. high, including Stand. o's fcH Stands. Heating Surface. Price. Heating Surface. Price. Heating Surface. Price. Heating Surface. Price. Inches. Sup. Ft. . Sup. Ft. . Sup. Ft. 2 Sup. Ft. . 8 24 x 5 16} 2 18 20 6 22 12 35* x 5 24* IS 27 Z J5 29* 3=5 32 z i 15 44 x 5 31 1 34 37 2 40 18 52* x 5 37 K 41 3 45 CL. n- 49 ex. All tested before leaving works, sent Berlin blacked, if not otherwise ordered. Inlets and outlets tapped up to i inch at each end or in any position under base. Description and other particulars on application. Price for other designs on application. Works: COALBROOKDALE, R.S.O., SHROPSHIRE. Telegrams " DARBY, COALBROOKDALE." Show Rooms: VICTORIA EMBANKMENT, BLACKFRIARS, LONDON, E.G. Telegrams " SEVEKNDALE, LO'NDON." ADVERTISEMENTS. CASTING? HOT WATER_ PIPES Q) ^ AND CONNE LOGUES LISTS ON APPUCATION ARACEN MACFABLANE'S CONDUCTOR PIPES, for Rain-water, Stove, Soil, and Ventilating purposes. Plain and Ornamental. MACFABLANE'S EAVE GUTTERS, for Rain-water, Building Cornices, Boundary Walls, Sheds, Valley Roofs, Water Conduits, &c. MACFABLANE'S TERMINALS, FINIALS, CROSSES, BANNERETS, WEATHER VANES, FLAG-STAFFS, BELFRIES, &c., in every style. MACFABLANE'S RAILING, CRESTING, BALCONIES ; FRIEZE, ALTAR- SCREEN, GALLERY FRONT, and TOMB RAILS, &c. MACFABLANE'S CONSERVATORIES, VERANDAHS, PORCHES, ARBOURS, COLUMNS, PILASTERS, BRACKETS, SPANDRILS, &c. MACFABLANE'S LAMP PILLARS, STANDARDS, and BRACKETS, for Streets, Squares, Gateways, Stations, Bridges, &c. MACFABLANE'S DRINKING FOUNTAINS, for Streets, Schools, Squares, Parks, Gardens, Stations, Market- Places, &c. MACFABLANE'S URINALS, in Cast Iron, for Streets, Courts, Schools, Railways, Factories, Public Works, and Institutions. MACFABLANE'S WATER-CLOSETS, in Cast Iron, for Schools, Railways, Factories, Public Works, and Institutions generally. ELECTRIC LIGHT PILLARS AND BRACKETS. WIRE WAYS. GLASS ENAMELLED SOIL PIPES A SPECIALITY. WALTER MACFARLANE & CO., Architectural, Sanitary, and General Ironfounders, GLASGOW. ADVERTISEMENTS. H. MUNZING, AMERICAN MERCHANT, 199 UPPER THAMES ST., LONDON, E.C Headquarters of HOT-WATER, STEAM, and GAS-FITTERS' PATENT AMERICAN TOOLS, GUN-METAL AND IRON YALYES, MALL-IRON TUBE FITTINGS, RADIATORS, PIPE-HANGERS, &C., &C WRITE FOR LATEST DESCRIPTIVE CATALOGUE. ADVERTISEMENTS. THE GENERAL IRON FOUNDRY COMPV, LIMITED, MAKERS OF HOT" WATER PIPES and Connections (see Illustrations at page 222 in this book). Cast-iron Saddle Boilers, Riveted and Lap Welded Boilers of every description. Improved Hot-Water Pipes and Coils with Indiarubber Joints, Heating and Ventilating Radiators, Circulating Cylinders and Tanks, Ventilating Gear for Greenhouses, WroughtJron Tubes, &c. ESTIMATES GIVEN FOR MATERIALS ANP FIXING COMPLETE, Illustrated Price List Post-free on Application, SANITARY CASTINGS, Soil and Socket Main Pipes, Gully Grates, Man-Hole and Air^Tight Doors, Ventilators and Valves, Ventilating Lamp Posts (Wimbledon Pattern), Baths, Lavatories, Sinks, &c. Rain-Water Goods of every description. STABLE FITTINGS. Illustrated Price List on Application. ESTIMATES GIVEN FOR MATERIALS AND FIXING. STOVES, RANGES, Chimney- Pieces, Mantel Registers, Tortoise and other Heating Stoves, Kerbs, Firerlrons, &c. WINDOWS AND CASEMENTS in Cast and Wrought Iron, SQLE MAKERS OF MOLINE'S PATENT WROUGHT -IRON WINDOWS, Illustrated Price Lists can be had of all goods manufactured by the Company, 43 UPPER THAMES STREET, AND BROKEN WHARF, LONDON, E.G. 10 ADVERTISEMENTS. ESTABLISHED 1856 R. JENKINS & CO., ROTHERHAM. Registered Design. Air Cock, for Hot-Water, Pipes, Radiators, &c. WROUGHT IRON AND STEEL WELDED BOILERS OP SUPERIOR QUALITY AND DESIGN. WHOLESALE AGENTS FOR JENKINS' AUTOMATIC AIR VALVES FOR RADIATORS, &c. Wentworth Boiler. Bath and Range Boilers. Independent Box Boiler. For HEATING by WATER or STEAM. "Dome Top." Section " Duplex." For Harness Rooms with Independent _ _ Open-Fire Front. Cylinder Boilers. Illustrated Catalogue, forwarded on receipt of Trade Card. ADVERTISEMENTS. Contractors to H.M. War Department, Science and Art Department, THE THAMES BANK IRON CO., UPPEE GEOUND STEEET, BLACKFEIAES, S.E. TELEGRAPHIC ADDRESS: "HOT WATER, LONDON." TELEPHONE No. 4763. MANUFACTURERS OF WARMING APPARATUS OF EVERY DESCRIPTION. HAVE THE LAE6EST AND MOST VABIED STOCK IN THE TRADE OF HOT-WATER BOILERS, PIPES, AND CONNECTIONS. AWARDED GOLD AND SILVER MEDALS, LONDON, 1883, 1886, AND 1892; FOR BOILERS, &c., AND GENERAL EXCELLENCE OF CASTINGS. Hot-Water and STEAM RADIATOR suitable for WARMING MANSIONS, CHURCHES, INSTITUTIONS, OFFICES, &c., &c. MADE IN OTHER DESIGNS. Contains a VERY LARGE HEATING SURFACE. No Coil Case Required. Can also be Supplied with Marble Top. MADE IN VARIOUS SIZES, EITHER ONE OR Two Rows OF LOOPS. PRICES ON APPLICATION. CAST IRON SOIL PIPES. Socket Pipes for Gas or Water. Flange Pipes for Steam. VALVES OF EVERY DESCRIPTION. LAMP COLUMNS. GULLY GRATES. GUARD POSTS. SIDE ENTRANCES. STABLE FITTINGS, &c. &c. PRICE LIST GRATIS. ILLUSTRATED CATALOGUE-ONE SHILLING. ADVERTISEMENTS. Sole Manufacturers si THE MEADOW FOUNDRY CO., LTD. MANSFIELD, NOTTS. Great Reduction, FOR HOT WATER OR STEAM., ADVERTISEMENTS. MESSENGER & COMPANY, HOT-WATER ENGINEERS, LOUGHBOROUGH, LEICESTERSHIRE, LONDON OFFICE: 163 Falmerston Buildings, Old Broad St., E.G. THE LOUGHBOROUGH BOILER. Requires no sunk stokehole. Plans and Estimates prepared for Heating Public Buildings, Churches, Residences, Conservatories, &c,, upon the most economic and efficient principles, Being Founders of Hot- Water Pipes, as well as Heating Engineers, MESSENGER & GO. are able to quote the lowest prices for an absolutely reliable apparatus. THE CHATSWORTH BOILER. With terminal Water-way End and Return Flue through top. Illustrated Catalogues of BOILERS, RADIATORS, and other Heating Appliances free on application. Sole Manufacturers of the celebrated Loughborough" Boiler, of which thousands are in use in all parts of the country. ADVERTISEMENTS. See Pages 175, 176, 200, 202, 203, 204 of this Treatise. WELDED BOILERS ! WELDED BOILERS ! ! &7LEMINC (SUCCESSORS TO S. T. CROOK'S EXECUTORS), PREMIER WORKS, HALIFAX, ENGLAND. TELEGRAMS: GRAHAM FLEMING, HALIFAX. TELEPHONE No. 39. Inventors and First Makers of WELDED HOT WATER BOILERS OF VARIED DESIGNS AND SIZES. TESTED IN HYDRAULICS OR STEAM. Complete Illustrated Catalogue on Application. THE ORIGINAL MAKERS. ESTABLISHED 1854. ADVERTISEMENTS. SPH 2 N l6 ADVERTISEMENTS. THE BEESTON FOUNDRY Co., LD BEESTON, near NOTTINGHAM. BEESTON VENTILATING RADIATOR Made in over 200 different sizes. Makers of Pearson's Patent Valves. Makers of Hot-Water Pipes Connections. Makers of the Beeston Boiler. THE BEESTON FOUNDRY Co.. LD ADVERTISEMENTS. BROS., ENGINEERS, 86 QUEEN STREET, CHEAP8IDE, LONDON, E.G Telegraphic Address: "KORTINa, LONDON." PATENT RADIATORS & GILLED PIPES, Suitable for warming and ventilating by hot water, live or exhaust steam, have the largest heating surface of any Radiators in the mar- ket. Vertical Radiators in two patterns, 2J, and $ ft. high. Easy combina- tion of any number of sections. Coil Gases to suit. Gilled Pipes in 3 and $ in. diameter, maximum length 6i ft, All flanges faced on strip. Very large surface fitted into small space. PRICES ON APPLICATION. 2 N 2 i8 ADVERTISEMENTS. LONGDEN & CO., PHENIX FOUNDRY, SHEFFIELD. SOLE MAKERS OF THE "SUNBEAM" PATENT RADIATORS. Prepared either for steam or hot water. All joints are screwed. No India-rubber or other packing used. Nearly 10,000 Radiators of our make in use in Great Britain. Made in circular and other forms. Trade SUNBEAM. Mark. LONDON OFFICE: 447 OXFORD STREET, W. These Radiators are used in the following places : National Portrait Gallery, Edinburgh ; Natural History Museum, South Kensington ; New Assize Courts, Bir- mingham and Nottingham ; Guildhall, Gloucester ; Hove Town Hall ; Ventnor Royal Hospital for Consumption ; Polytechnic Institute, Regent Street, London ; St. Paul's Schools, West Kensington, London ; Coats' Memorial Church, Paisley ; and many other public and private edifices. ADVERTISEMENTS. The London "Warming and Ventilating Company (T. YEOMANS, Manager.) 105 REGENT STREET, LONDON, W. Contractors to H.M. War Office, Home Office, Admiralty, &c., &c. PATENT "REi/ERTIVE" and other open and close Stoves, suitable for Drawing, Dining, Bil- liard, Bed- rooms, Halls, &c., specially adapted for burning most successfully ANTHRACITE (ABSOLUTELY SMOKELESS) COAL. Effecting a saving in fuel of more than 30 per cent., with increased heat. Warmth under perfect control, and heat deflected into room, with minimum escape of same up chimney. Estimates Free. Illustrated Catalogue on Application. "GURNEY" stoves for Warming Churches, &c., as specified by leading Architects, and as used in St. Paul's, Salis- bury, Exeter, Gloucester, Lin- coln, Llandaff Cathedrals, York Minster, St. George's Chapel, Windsor, &c. Twenty Cathe- drals, and over 10,000 Churches, Schools, Government and other public and private buildings successfully warmed by our system. Many Prize Medals Awarded. ECONOMICAL, EFFICIENT. CHEAP, DURABLE, SAFE. Gurney Stoves burn more economically with ANTHKACITE Coal than with any other fuel. 20 ADVERTISEMENTS. ADVERTISEMENTS. 21 CHURCHES, CHAPELS, SCHOOLS, AND Public Buildings, CAN BE THOROUGHLY WARMED AND VENTILATED WITH LITTLE FUEL BY THE CONVOLUTED STOVE EFFICIENCY IN ALL OASES GUAKANTEED, Testimonial from Sir ISAAC HOLDEN, Bart., M.P. OAKWORTH, KEIGHLEY, July 7, 1893. GENTLEMEN, Having had several years' experience of your Convoluted Stove, in several Chapels and Schools, and in warming four detached houses, and also in heating my private Turkish Bath at Oakworth, I can bear testimony to its value, and can strongly recommend it as an efficient Air Warmer. Your system of drawing fresh air to the apparatus from the outside, thus ensuring a constant change of air, ought to be universally adopted, not only in Turkish Baths, but also in Private Houses, Churches, Chapels, and Public Halls. With kind regards, ISAAC HOLDEN Messrs. J. CONSTANTINE & SON, Manchester. The Royal Exchange and Free Trade Hall, Manchester ; Mr. Charrington's Great Assembly Hall, Mile End Road, London ; are warmed in all parts by this apparatus, with less fuel than any other buildings of the same dimensions. SEE PAGES 322 TO 324. Illustrated Circular with Testimonials free, and Tenders on application to J. CONSTANTINE & SON, ConboIuteD @>tobe SBorfes, STOCKTON STREET, CLARENDON STREET; OR 23 OXFORD STREET, MANCHESTER. 22 ADVERTISEMENTS. CARTON & KING, Exeter Foundry, EXETEE. MANUFACTURERS OF BOILERS, HOT-WATER COILS, & RADIATORS. FITTERS OF Apparatus for Warming Public Buildings, Mansions, Dwelling Houses, Churches, and Schools. Horticultural Hot-Water Engineers. Heating of Vineries, Conservatories, Forcing Houses, &c. Domestic Hot-Water Supply Apparatus lor Baths, Lavatories, &c., from Special Boilers or Kitchen Ranges. MANUFACTURERS OF DEVON KITCHEN RANGES. The "Exonian," The "Rectory," The "Medium," The "Cottage/' MAKERS OF WARM AIR DISTRIBUTING GRATES AND SLOW COMBUSTION GRATES, CATALOGUES SENT ON APPLICATION. JTJST PUBLISHED. In demy Svo, cloth, 600 pages, and 140 Illustrations, 6s. SPONS' MECHANICS' OWN BOOK; A MANUAL FOR HANDICRAFTSMEN AND AMATEURS. CONTENTS. Mechanical Drawing Casting and Founding in Iron, Brass, Bronze, and other Alloys Forging and Finishing Iron Sheetmetal Working Soldering, Brazing, and Burning Carpentry and Joinery, embracing descriptions of some 400 Woods, over 200 Illustrations of Tools and their uses, Explanations (with Diagrams) of 116 joints and hinges, and Details of Construction of Workshop appliances, rough furniture, Garden and Yard Erections, and House Building Cabinet-Making and Veneering Carving and Fret-cutting Upholstery Painting, Graining, and Marbling Staining Furniture, Woods, Floors, and Fittings Gilding, dead and bright on various grounds Polishing Marble, Metals, and Wood Varnishing Mechanical movements, illustrating contrivances for transmitting motion Turning in Wood and Metals Masonry, em- bracing Stonework, Brickwork, Terracotta, and Concrete Roofing with Thatch, Tiles, Slates, Felt, Zinc, &c. Glazing with and without putty, and lead glazing Plastering and Whitewashing Paper-hanging Gas-fitting Bell-hanging, ordinary and electric Systems Lighting Warming Ventilating Roads, Pavements, and Bridges Hedges, Ditches, and Drains Water Supply and Sanitation Hints on House Construction suited to new countries. E. & F. N. SPON, 125 STRAND, LONDON. New York : SPON & CHAMBERLAIN, 12 Cortlandt Street. ADVERTISEMENTS. L & L : TUBES & FITTINGS ^ LARGE STOCKS Highest Quality for Gas, Steam, Hot Water, fto. AND STEEL BOILER TUBES GALVANIZED TUBES & FITTINGS. LLOYD & LLOYD, Albion Tube Works, Birmingham, Coombs Wood Tube Works, near Halesowen. London!: 90 Cannon St. & 157 Upper Thames St. Liverpool: 63 Paradise Street. Manchester: 42 Deansgate. 24 ADVERTISEMENTS. JOHN BELLAMY, JEncjineer, ^anfc, anb Boiler MANUFACTURER OF WROUGHT IRON TANKS & CISTERNS. Of any Size, Shape, or Gauge. GALVANIZED OR PAINTED CISTERNS For Water, Oil, or other Purposes. Stayed for any Pressure. GALVANIZED CIRCULATING CYLINDERS. Specially made by machine. Ends pressed by Hydraulic and Hydraulic Riveted throughout, in similar way to High Pressure Boiler Work. Can be made to any size and for varying- pressures up to 400 Ibs. per sq. in. SUITABLE FOR STEAM, AIR, OR WATER PRESSURE. IRON AND STEEL STEAM BOILERS, Lancashire, Vertical, Locomotive, Multitubular, Cornish, or any other type, HOT WATER BOILERS. ? BELLAMY'S IMPROVED HORTICULTURAL BOILER. Hig! class - <"-*"" SOLE ADDRESS BYNG STREET, MILLWALL, LONDON, E. Telegrams : " BELLAMY, LONDON." Telephone No. 5157. ADVERTISEMENTS Twelfth. Edition, Revised and Improved, Is. SPONS' TABLES AND MEMORANDA FOR ENGINEERS. Selected and arranged by J. T. HURST, C.E., MEM. OP THE SOCIETY OP ENGINEERS, MEM. PHTS. SOO. OP LONDON, SURVEYOR WAR DEPARTMENT, AUTHOR OP 'ARCHITECTURAL SURVEYORS* HANDBOOK,' * HURST'S TREDGOLD'S CARPENTRY,' ETC. 64mo, Boan, Gilt Edges. EXCAVATORS' MEMORANDA BRICKLAYERS* Fire-Clay Flue Linings Weight of Bricks and Tiles MASONS' MEMORANDA Weight of Limes and Ce- ments Purbeck Paving Yorkshire Marble Slabs SLATERS' MEMORANDA Weight of Slates CARPENTERS' MEMORANDA Deal Standards Purlins Roof Scantlings Floors Rafters PLASTERERS' MEMORANDA SMITHS' & FOUNDERS' MEMO- RANDA Size of Heads, Nuts, &c. Rivets Shrinkage of Castings Corrugated Iron Zinc Weight of Round and Square Iron Flat Bar Iron Round Cast Iron Various Metals per ft. sup. Sheet Iron CONTENTS : Weight of Hoop Iron Chains, and size of Cast Iron Pipe Heads, Nuts, and Washers Cast Iron Socket Pipes Wire Size and Weight of Nails per M Spikes Weight of Cast Iron Balls Corrugated Iron Roofing Nails Shoes for Door Frames Relative Weight of various Metals Proportion of Wheels Cast Iron Pillars Relative Strength of Cast and Wrought Iron Pillars Safe Load for Stone Pillars Floors Strength of Rolled Iron Beams Fire-Proof Floors Wrought Iron Roofs PLUMBERS' MEMORANDA Weight of Sheet Lead Lead Pipes PAINTERS' AND GLAZIER'S MEMORANDA SUNDRY MEMORANDA Weight of Metals per foot cube Earth, Stone, &c. per ft. cube Timber Liquids Men and Animals Forage Water Oil Coal Ropes Railway Curves Measurement of Heights Railway Road Crossings Measurement of Distance MENSURATION Circumferences of Circles Areas of Circles Regular Polygons MONEY TABLES, English and Foreign WEIGHTS AND MEASURES Weight and size of casks Size of Paper French Measures Maltese Comparison of English and Foreign Measures This work is printed in a pearl type, and is so small, measuring only 2 in. by If in., by in. thick, that it may be easily carried in the waistcoat pocket. " It is certainly an extremely rare thing for a reviewer to be called upon to notice a volume measuring but 2| in. by If in., yet these dimensions faithfully represent the size of the handy little book before us. The volume which con- tains 118 printed pages, besides a few blank pages for memoranda is, in fact, as true pocket-book, adapted for being carried in the waistcoat pocket, and containing a far greater amount and variety of information than most people would imagine could be compressed into so small a space The little volume has been compiled with considerable care and judgment, and we can cordially recommend it to our readers as a useful little pocket companion." Engineering. E. & F, N, SPON, 125 STKAND, LONDON. 26 ADVERTISEMENTS. Crown 8vo, cloth, with numerous Illustrations, Price 6s. each, by post 5. 4d. WORKSHOP RECEIPTS, FOB THE USE OF jKatwfaxtimrs, Jfteljanirs, antt Stentifir FIRST SERIES. CONTENTS : Bookbinding Bronzes Candles Cement Cleaning Concretes Dyeing Electro-Metal- lurgy Enamels Engraving Etching Firework Making Freezing Fulminates Furniture Creams, Oils, Polishes, Lacquers, and Pastes Gilding Glass Cutting Glass Making Graining Gurns Horn Working India-rubber Ink Japans Lacquers Marble Working Matches Mortars Paper Hanging Painting in Oils Photography Polishes Pottery Silvering Soap Solders Taxidermy Treating Horn, Motber- o'-Pearl, and like substances Varnishes Veneering Whitewashing, &c. &c. SECOND SERIES. CONTENTS: Acldlmetry and Alkalimetry Albumen Alcohol Alkaloids Baking-powders Bitters- Bleaching Boiler Incrustations Cements and Lutes Cleansing Confectionery Copying Disinfectants Dyeing Staining and Colouring Essences Extracts Fireproofing - Gelatine. Glue, and Size Glycerine- Gut Hydrogen Peroxide Ink Iodine lodoform Isinglass Ivory Substitute* Ijeather Luminous Bodies Magnesia Matches Paper Parchment Perchloric Acid Pigments Paint and Painting Potassium Ozalate Preserving. THIRD SERIES. CONTENTS : Alloys Aluminium Antimony Barium Beryllium Bismuth Cadmium Cassium Calcium Cerrium Chromium- Cobalt Copper Didymium Electrics (including alarms, batteries, bells, carbons, coils [induction, intensity, and resistance], dynamo-electric machines, fire risks, measuring, micro- phones, motors, phonographs, photophones, storing, lelephones) Enamels and Glazes Erbium Gallium Glass Gold Indium Indium Iron Lacquers Lanthanum Lead Lithium Lubricants Magnesium Manganese Mercury Mica Molybdenum Nickel N isbium Osmium Palladium Platinum Potassium Rhodium Rubidium Ruthenium Silenium Silver Slag Sodium Strontium Tantalum Terbium Thallium Thorium Tin Titanium Tungsten Uranium Vanadium Yttrium Zinc- Zirconium. FOURTH SERIES. Waterproofing 1 : rubber goods, cuprammonium processes, miscellaneous preparations Packing: and Storing 1 articles of delicate odour or colour, of a deliquescent character, liable to ignition, apt to suffer from insects or damp, or easily broken Em/balming and Preserving" anatomical specimens Leather Polishes Cooling- Air and Water, producing low temperatures, making ice, cooling syrups and solutions, and separating salts from liquors by refrigeration Pumps and Siphons, embracing every useful contrivance for raising and supplying water on a moderate scale, and moving corrosive, tenacious, and other liquids Desiccating" : air- and water-ovens, and other appliances for drying natural and artificial products Distilling": water, tinctures, extracts, pharmaceutical preparations, essences, perfumes, and alcoholic liquids Emulsifying 1 as required by pharmacists and photographers Evaporating-: saline and other solutions, and liquids demanding special precautions Filtering-: water, and solutions of various kinds Percolating- and Macerating Electrotyping Stereotyping by both plaster and paper processes Bookbinding 1 in all its details - Straw- Plaiting and the fabrication of baskets, matting, &c. Musical Instruments: the preservation, tuning, and repair of pianos, harmoniums, musical boxes, c. Clock and Watch Mending-: adapted for intelligent amateurs Photography : recent development in rapid processes, handy apparatus, numerous recipes for sensitizing and developing solutions, and applications to modern illustrative purposes. FIFTH SERIES. Diamond Cutting Labels Glass Manipulations Laboratory Apparatus Cement, and Lutes Cooling ing Evaporating Magic Lanterns Desiccating Metal Work Distil'ing Modelling Filtering- Casting Protecting Metal Surfaces Fireproofing Taps Lacqueurs- Tobacco Pipes Ink Tying Copying Evaporating Magic Lanterns Desiccating Metal Work Distil'ing Modelling Filtering- Plaster Casting Protecting Metal Surfaces Fireproofing Taps Lacqueurs - Tobacco Pipes Ink Tying and Splicing Electrics Tackle Packing and Storing Walking Sticks Musical Instruments Illuminating Agents Percolation Explosives Stereotyping Netting Pumps and Siphons Repairing Books- Preserving Boat Building Waterproofing Scientific Instrument Making Boot Mending Velocipedes. E. & F. N. SPON, 125 Strand, London. New York: SPON & CHAMBERLAIN, 12 Cortlandt Street. ADVERTISEMENTS. 27 WM. GRAHAM & SONS, Trig Lane, Castle Yard & 35 Upper Thames St., Telegraphic Address: " BAYNARD," LONDON. HOT-WATER ENGINEERS AND FITTERS. BOILERS, PIPES, TUBES, COILS, COIL OASES WITH IRON AND MARBLE TOPS, AND HOT-WATER FITTINGS. Ventilating Gearing for Greenhouses. Boiler, 3 ft. by 10 in., with 24 ft. 2 in. Hot-Water Pipe, 1 Syphon, 2 Spigots, 1 Air-Cock, Supply Cistern, Wrought-iron Tube for connecting: same, and Rubber Rings for jointing, prepared ready for fixing, ^34* ASTON TUBE WORKS, ASTON, near BIRMINGHAM. Telegraphic Address: "PLUME," BIRMINGHAM. TUBES AND FITTINGS FOR GAS, STEAM, WATER, AND HEATING PURPOSES. Tube Orders over 2 nett value DELIVERED FREE to any Railway Station in England. EVERY TUBE TESTED before leaving the Works. HEATING APPARATUS. Telegrams " HEAT, Stourbridge." MEDALS 1875 and 1881. SPECIALLY ADAPTED FOR Churches, Schools, Hospitals, Libraries, Public Halls, PATRONISED BY H.M. GOVERNMENT, H.M. Commissioners of Prisons, H.M. Post Office Authorities, London School Board, And other Public Bodies throughout the Country. W. JONES' Treatise, 'HEATING. BY HOT WATER: (SECOND EDITION.) 200 Pages and over 90 Illustrations. BOUND IN CLOTH. Price 2/6 net. Post-free 2/9. Mansions, Hotels, Billiard Rooms, Offices, Factories, . &c., &c. Illustrated Catalogue Free. . Estimates for Warming every description of Building, either by HIGH Pressure LOW Pressure, or STEAM. SUCCESS GUARANTEED. HEATING APPABATUS FOR GREENHOUSES, &c., A SPECIALITY. PATENTEES AND MANUFACTURERS, STOURBRIDGE. HARTLEY & SUGDEN, LTD, WROUGHT-IRON AND STEEL WELDED & RIVETED BOILERS, OF EVERY DESCRIPTION, FOR HOT-WATER HEATING APPARATUS. PATENT "CLIJNAX" BOILER. ELEVATION. CROSS NEW INDEPENDENT " CHATSWCT , LER ELEVATION. SECTION. New Illustrated Catalogue on application.