(SECOND EDITION) STANDARD LIGHTING WITH INCANDESCENT ELECTRIC LAMPS COMPILED BY A STAFF OF EXPERTS Endorsed by the Lighting Department of the Joint Com- mittee for Business Development in the movement to " Electrify" and by the Society for Electrical Development. The movement for Business Development is being promoted by the following national organisations: National Electric Light Association; Electrica[ Supply Jobbers' Association; National Association of Electrical Contractors and Dealers; National Council of Lighting Fixture Manufacturers; Lighting Fixture Dealers' Society of America; Illuminating Glassware Guild; Illuminating Engineering Society; Electrical Manufacturers' Council; The American Institute of Electrical Engineers. In the preparation of this text, the aim has been to present information of real, practical value both to the purchaser and to the in- staller of lighting equipment. Analysis of available information revealed that in the transactions of the Illuminating Engineering Society and in the publications of the manufacturers of lighting equipment was to be found the most exhaustive, clearest, and most up-to-date discussion of many of the more important lighting problems. These publications have, therefore, been freely used in the compilation of this handbook. Acknowledgement is gratefully made to S. E. Doane, G. H. Stickney, D. W. Atwater, A. B. Oday, Ward Harrison, A. L. Ppwiell, S. G. Hibben, H. A. Smith, R. E. Harrington, A. S. Turner, C. A. Atherton, M. Luckiesh, Earl A. Anderson, J. H. Kurlander, G. A. Clewell, H. H. Magdsick and J. R. Colville for permission to use material prepared by them and for constructive sug- gestions in the presentation of the subjects. INDEX TO CONTENTS PAGE 269. PUBLISHED BY H. C. CUSHING, JR., 8 WEST 4OTH ST., NEW YORK, U.S. A, Copyright, 1922 by H. C. GUSHING, JR. TABLE OF CONTENTS Page ILLUMINATION FUNDAMENTALS PART 1 5 Amount of Light Diffusion of Light Color Quality of Illumi- nation Shadow Uniformity of Illumination Illumination of Vertical Surfaces Desirable Wall Brightness Maintenance. ILLUMINATION DESIGN DATA PART II 14 Definitions Foot-Candle Illumination Type of Lighting Unit Location of Outlets, Mounting Height, and Number of Lighting Units Lamp Size Computed Illumination Values Illustrative Prob- lem Guide to the Selection of Reflecting Equipment, Chart Spacing Mounting Height, Table Foot-Candles Illumination, Tables Coefficient of Utilization, Table Room Index, Tables Lumen Output of Mazda Lamps, Table Computed Illumination Values, Table. STORE AND SHOW WINDOW LIGHTING PART III 46 General Classes of Store Lighting Amount of Illumination Required Lighting Units or Luminaires Lamps Recommended for Use, Table Entrance Doorway Lights Night Lights Wiring and Control Color Matching and Color Quality Showcase Lighting Illustrative Problems Show Window Lighting Show Window Equipment Show Window Illumination Calculations. INDUSTRIAL LIGHTING PART IV 63 Requirements Light on the Work Daylight Intensities, Table Illumination of Surrounding Surfaces Color Quality of Light Glare Specular Reflection Shadows Locations of Outlets Work Bench Lighting Chart for Effecting Lighting Improvements 115 vs. 230 Volt Lamps. LIGHTING OF OFFICE BUILDINGS AND DRAFTING ROOMS PART V 89 Introduction Method of Lighting Comparison of Lighting Systems Spacing of Outlets Wattage Required Drafting Rooms. SCHOOL LIGHTING PART VI 98 Introduction Illumination Values Diffusion Classrooms General Considerations Blackboards Comparison of Various Lighting Sys- temsCorridor Laboratory Auxiliary Outlets. RESIDENCE LIGHTING PART VII 105 Introduction Systems of Lighting Kitchen Butler's Pantry Laundry and Work Bench Den or Sewing Room Living Room Dining Room Hall or Reception Room Bed Room Bath Room Porch Grounds Garage Wiring Recommended Sizes of Lamps, Chart. CHURCH LIGHTING PART VIII 125 General Requirements Methods to Avoid Feasible Schemes for Lighting Ritualistic Churches Evangelical Churches Special Lighting Requirements Chancel Choir Loft Windows Wiring. LIGHTING OF PUBLIC BUILDINGS PART IX 135 Armories Gymnasiums Main Exercising Floor Swimming Pool Running Track Exercising Rooms Shower and Locker Rooms Art Galleries Paintings Statuary Museums Libraries Municipal, County, and State Buildings Banks. LIGHTING OF HOSPITALS AND DENTAL OFFICES- PART X 1 54 Wards Private Rooms Corridors Operating Rooms Wiring and Signal Systems Dental Offices. FLOODLIGHTING PART XI 166 Equipments Typical Installations. LIGHTING FOR OUTDOOR SPORTS PART XII 182 Tennis Courts Clock and Court Golf Motorcycle and Bicycle Racing Outdoor Arenas Bathing Beaches Trap Shooting Ranges. LIGHTING FOR INDOOR RECREATIONS PART XIII 191 Pool and Billiard Parlors Bowling Alleys Indoor Tennis Courts Squash Courts Skating Rinks. MAINTENANCE OF INTERIOR LIGHTING SYSTEMS- PART XIV 199 Extent of Lighting Depreciation Value of Light Wasted Systematic Maintenance Suggestions for Restoring a Lighting System, Chart. MODERN PRACTICE IN STREET LIGHTING PART XV 207 Principal Business Streets Thoroughfares Residence Streets Outlying Districts and Alleys Highways Summary of Modern Practice, Table Necessity of Maintenance. ELECTRICAL ADVERTISING PART XVI 2ig Forms of Electrical Advertising Exposed Lamp Signs Enclosed Lamp Signs Bulletin and Poster Boards Building Outline and Mar- quee Lighting Flood-lighted Advertising Sign Maintenance. CODE OF LIGHTING PART XVII 233 The Code of Lighting for Factories, Mills and Other Work Places prepared and issued by the Illuminating Engineering Society. PART I ILLUMINATION FUNDAMENTALS In the last year of the war and in the year immediately fol- lowing, more progress was made in the application of artificial lighting than in any ten-year period preceding. Continual im- provements in lamps and reflecting equipments, the constantly increasing availability of electric service, and the growing knowl- edge of illumination fundamentals, had, over a period of years, been paving the way for a sudden, sharp advance in lighting practice. In no field of lighting was the progress so remarkable as in industry, for here the value of good illumination could be most easily measured in terms of dollars and cents. Tests con- ducted under actual working conditions demonstrated that startling increases in production were possible when antiquated lighting systems were replaced with new ones which produced lighting comparable with the daylight lighting of well designed modern factories. Most executives believed in good lighting, they acknowledged its importance, but what they did not know, and what had not been satisfactorily demonstrated, was that what were then considered good lighting installations we're not sup- plying enough light ; in other words, were not good lighting. Once the traditional illumination levels were broken through and levels 3, 4, and 5 times as high tried out in service, the handi- cap imposed by previous standards became apparent. Artificial lighting in every field moved forward. Amount of Light We do not know today how much light is right for the many applications. We do know that 3 or 4 foot-candles will enable one to see more detail than will 1 foot-candle; that 10 foot- candles will reveal more than 3 or 4; that 50 foot-candles will increase perception over 10; that 100, or even more, will some- times produce still further improvements when the eyes are taxed to the utmost. We know that vision is quickened when the illumination is increased from 2 or 3 foot-candles to 10, 50, or to 100 or more. We know that persons with defective vision, and this means a surprisingly large proportion of the people, are even more greatly handicapped by poor lighting than are those with good vision, and that they respond more markedly to improve- ment in the lighting. Again we know that bright and cheerful surroundings are stimulating, that they inspire cleanliness, that they make for order and neatness. In these simple fundamental facts we find the reasons why, in industry, higher levels of illu- mination increase production without imposing strain upon the employees, why they automatically reduce accident hazard, de- crease spoilage, and improve morale ; why, in the office, they enable more work to be performed with fewer headaches, less mistakes, and better tempers; why, in the store, they attract customers, facilitate the examination of material, and make for quicker sales ; and why, in the home, they facilitate reading, working or studying at night. Diffusion of Light With the 10 to 1 increase in efficiency of the incandescent lamp, since its invention scarcely two-score years ago, has come the generation of large volumes of light in a small space. This means, of course, light sources of great brilliancy. A bright source does not in itself insure adequate lighting, in fact, unless skillfully handled, it presents a positive menace to vision. Objects are seen by the light which comes from them to the eye; light which comes directly from the light source to the eye or is reflected from the source to the eye by some polished surface is not only useless in illuminating the object viewed but if of high intensity or of large volume, it produces a blinding ef- fect which seriously interferes with seeing and may result in permanent injury to the eyes. "Glare" is the term applied to light which obstructs vision in this way. Glare blinds the driver of an automobile when approaching another with improperly adjusted headlights at night; it handi- caps the workman who is trying to see fine details with a bril- liai:: light source near his line of vision; it produces acute dis- comfort in the conference room where men sit facing inade- quately shaded windows for a long period of time; it is annoying in the home where wall brackets containing unshielded lamps are seen against dark backgrounds ; it blinds the ball player, who tries to follow the ball against the sun. In hundreds of ways it is constantly interfering with vision and handicapping us in work and play. Specular reflection, that is, the reflections of light sources in polished surfaces, while sometimes an aid to vision, is often, because of its insidious nature, more harmful than direct glare. Under proper control, it facilitates the reading of the micrometer scale or the inspection of a polished surface ; in excess, it be- comes reflected glare, dulls perception, and paves the way for accident. As moderate specular reflection, it brings out the texture of materials and assists the housewife in her sewing; as reflected glare, it blurs the printed page and causes eyestrain in reading. In small amounts, coming from the pavement to the eye it discloses the inequalities of the road to the motorist at night or reveals the pedestrian in silhouette; in large amounts, as from snow in sunlight, it produces painful and serious injury to the eyes. Fortunately, once the danger in direct glare and the advan- Had only one row of units been employed in lighting this store, as is quite commonly the case with small stores, the center aisle would have been brightly lighted, but much less light would fall on the counters where most needed and a customer would inevitably cast a shadow on the merchandise. Note the soft even illumina- tion shown in this illustration where correct principles have been followed tages and disadvantages in specular reflection are understood, the means for eliminating the bad and retaining the good is readily available. The answer lies in proper diffusion of the light. The reflecting equipments now regularly manufactured provide any degree of diffusion considered desirable. The to- tally indirect type which directs all of the light to the ceiling, whence it is diffused throughout the room, represents the ut- most in diffusion; the semi-indirect type, which directs a large proportion of the light to the ceiling, but transmits some through the bowl, provides a degree of diffusion which is pre- ferred by many; so-called light-directing semi-enclosing, or to- tally enclosing, units are available in designs which provide good control of the light and satisfactory diffusion; enclosing globes of the proper size and density provide diffusion of the light but afford little control of its distribution. Open reflectors of proper design eliminate glare from the lamp filament but afford no protection against reflected glare in polished surfaces. Such re- flectors, however, when designed for, and used with, bowl- enameled lamps constitute an equipment which is almost ideal for the large majority of industrial applications. They are in- expensive, easy to maintain, allow considerable control of the light distribution, provide good diffusion, and eliminate objec- tionable specular reflection while at the same time producing sufficient glint for the reading of a scale or the examination of textiles. Color Quality of Illumination Since an object is seen by the light which comes to it from the source and thence by reflection to the eye, it follows that color in the object is seen only when the light contains rays of that color. For example, a red object will appear black under light in which red rays are lacking or a blue object will appear black when blue rays are absent in the source. Daylight is composed of all the colors in proportions seen in the rainbow The light from Mazda lamps contains all the colors composing daylight but if the spectra, or rainbows, of the two were to be compared it would be seen that the Mazda lamp was richer than daylight in the orange-red region and weaker in the blue. For ordinary purposes, the light from clear Mazda lamps is sufficiently like daylight to answer all requirements, but where color discrimination is a factor, as in sorting or grading pro- cesses for example, and in the laundry where scorch marks must be readily distinguishable, or where the artificial light is used to supplement daylight, as in an office, daylight lamps, which screen out the majority of the excess orange-red rays, find wide application. For purposes of color matching, dyeing, process printing, and the like, where extreme accuracy is necessary in the observation of colors, a still further correction of the light is necessary. For this service so-called color-matching units, which provide a light of true and unvarying north-sky quality, are available. The high efficiency of present incandescent lamps which makes practicable the approximation, or the duplication, of day- light on a large scale also permits the modification of light to any desired extent for obtaining striking and unusual effects in display windows, in decorative lighting, and in the home. Equipments designed especially for the control of color are readily available. Shadow Contrary, perhaps, to popular opinion, a certain amount of Correct lighting for every service conforms to certain fundamental prin- ciples. Note the evenness of illumination, the absence of sharp shadows, and the bright and cheerful appearance of the interior shadow is desirable in artificial lighting. Objects illuminated by perfectly diffused light appear flat and uninteresting, con- tours are lost, and it is difficult for the eye to form a correct judgment of the shape of an object. On the other hand, deep, black shadows are troublesome and are a source of constant danger because of what they may conceal. Shadows having a sharp edge or a series of sharp edges, which result from several small light sources near one another, are particularly annoying in office work, where they dance about the pencil point most disconcertingly. In general, in interior lighting, only soft illuminated shadows with gradually fading outlines should b^ tolerated. The number of shadows cast by an object and their length depends upon the number and the position of sources directing light toward the object; the softness of the shadow depends upon the area of the surfaces from which the light comes and upon the number of directions from which light is received. Indirect and dense semi-indirect units which make the ceiling serve as the principal light source, and large units of the direct-lighting type, therefore, make for soft shadows, small units of the direct type make for sharp shadows. As a general rule, lighting units which are satisfactory for the application from the standpoints of light diffusion and low brightness will also prove satisfactory from the standpoint of shadow when a sufficient number are used to provide a satisfactory degree of uniformity in the light- ing of the work. Uniformity of Illumination Where the prime purpose of lighting is the production of artistic effects, uniformity of illumination may be undesirable. On the other hand, it is not an uncommon experience to find in industrial plants that, because of too great a spacing between units, some workmen are supplied with only one half or one third as much light for their work as are others. Many office employees are forced to work under the same handicap. There are cases on record where the suspected incompetency of an employee with respect to his co-workers has been traced to the unsuspected cause of poor lighting. Definite relations exist between the height at which units are mounted above the work and the distance by which they may be separated to provide reasonable uniformity in lighting, and light from a sufficient number of directions so that shadows will not prove troublesome. These relations have been reduced to simple tabular form for the convenience of the designer of lighting systems. In general, the permissible distance between units should not be more than one and one-half times the height of the light sources above the work ; closer spacings can do no harm and are often desirable but when this spacing distance is exceeded, the illumination between units falls off very rapidly. The user of light should consider carefully before allowing his desire to keep initial costs low, lead him to install a system in which the proper spacing distance is materially exceeded. 10 Illumination of Vertical Surfaces For many locations, such as offices and drafting rooms, light is required principally on horizontal planes, such as desk tops or table tops, and it has been the custom to calculate illumination on the basis of that delivered to horizontal surfaces with the assumption that the oblique surfaces of objects would be suffi- ciently lighted. This practice may result in inadequate illumina- tion. In a machine shop, for example, the lighting of the vertical surfaces of the work or of machine parts is fully as important as There is no necessity for imposing a handicap on any worker because of poor light. Though illumination requirements for drafting rooms are comparatively severe on account of close visual application, these requirements are met by the uniform, thoroughly diffused, shadowless illumination of high intensity shown here the lighting of the horizontal surfaces. As a matter of fact, most shops are lighted during the day by light from windows, which give a greater light on the vertical surfaces than on the horizontal. In all such cases where direct lighting is used, only those lighting units should be installed which show a reasonably good candlepower in the 50-70 degree zone as well as below these angles. A shop lighted by closely spaced automobile head- lights directing the light downward from the ceiling would furnish ample light on a horizontal plane but such lighting would be far from satisfactory. Desirable Wall Brightness The effectiveness of a lighting system depends not only on the effectiveness of the lighting unit, but also on the reflecting properties of the walls, ceiling, and surroundings, and upon the size and proportions of the room. It is, in fact, entirely pos- sible to find an installation of reflectors of poor design and in- ferior from the standpoint of glare, which is nevertheless, from the single standpoint of the percentage of light reaching the illumination plane, better than an installation where reflectors of good design are used, if the former are installed under favor- able conditions such as light walls, ceiling, etc., and the latter under unfavorable conditions. On the other hand, it must be borne in mind that a large expanse of wall surface finished so light as to reflect a large volume of light into the eyes is objec- tionable for offices, residences, and all rooms where the occu- pants are likely to sit more or less directly facing the walls for considerable periods of time. Such data as are available indicate that where the brightness of the walls is equal to, or greater than, the brightness of white paper lying on a table or desk, annoying glare will result. In fact, a wall brightness one-half that of the paper has been found unsatisfactory a brightness of one-fifth is, apparently, comfortable. With the usual types of lighting units, walls are not illuminated to intensities as high as those obtaining on desk or table tops, and walls which reflect less than 50 per cent, of the light which strikes them should not produce discomfort, providing, of course, that they are of a mat or semi- mat finish. Walls finished in buff, light green, or gray reflect about the proper proportion of light and their use is meeting with general favor. Walls finished in a high gloss are not satisfac- tory from a glare standpoint. Maintenance The experiences of those who have installed high levels of illumination prove conclusively that every foot-candle delivered at the work has a definite tangible value. The man who provides a system capable of delivering 10 foot-candles at the work and then allows the system to de- preciate until it delivers only 3 or 4 is losing not only 60 or 70 per cent, of the light he is paying for but, what is far more im- portant, he is losing the profit on the difference between the 12 output of his employees at this low level of illumination and their output at the higher level. If the depreciation of a lighting system were of the order of 2 or 3 per cent, or even 10 per cent, the matter would not be so serious a one, but surveys of in- stallations in service show depreciations of 50 per cent., 60 per cent., and more. Many users are not getting one third of the light their systems are capable of delivering. The lighting of the home should be flexible to permit lighting effects suitable to various occasions to be obtained, but in all cases, the funda- mentals of lighting hold. All bright lights should be adequately shielded from view, though enough light should be available for reading or sewing comfortably. 13 PART II ILLUMINATION DESIGN DATA To take the several essential factors entering into illumina- tion design properly into account has appeared so complicated a task that many designers have adhered to rule-of-thumb meth- ods which, while adequate in some cases, are likely to lead to unsatisfactory. results when applied generally. The method of design here presented will be found fully as simple as any of the common short-cuts. It has the decided ad- vantage that the technical considerations wjhich are important as influencing the result and which require the experienced judg- ment of the engineer have been taken into account in the prep- aration of the charts and tables and therefore automatically re- ceive due allowance in the lighting design. The data apply in interiors where standard types of reflecting equipment are used to obtain general lighting of substantially uniform intensity. The four steps to be carried out in the design of a general lighting system for a room are : 1. Decide the foot-candle illumination required. 2. Select the type of lighting unit best adapted to the loca- tion. 3. Determine the location of outlets, the mounting height and number of lighting units required. 4. Ascertain the size of MAZDA lamp which will provide the foot-candles desired. i. Foot-Candle Illumination Tables 3 and 4, pages 25 to 31, list the foot-candle values, cor- responding to present standards, for different classes of indus- trial operations, offices, stores, etc. The desirable illumination DEFINITIONS Lumen: The lumen is the unit of light flux quantity. The number of lumens re- quired to light a given surface is proportional to the illumination in foot-candles and to the area of the surface in square feet. The light output of MAZDA lamps is given in lumens. Foot-Candle : The degree to which a surface is illuminated is measured in foot-candles. One lumen will light a surface of 1 square foot to an average intensity of 1 foot-candle. Coefficient of Utilization (Percentage O f Lumens Effective) : The proportion of the lumens generated by the lamps which reaches the plane of work is known as the Co- efficient of Utilization. It is dependent upon the type of diffusing and reflecting equip- ment, color of walls and ceiling and also the proportions of the room, that is, the size and shape of the room and the height of the light source above the plane of work. These room proportions are classified in this section by Room Index tables. The plane of work, unless otherwise specified is ordinarily considered to be horizontal and 2J4 feet above the floor. Depreciation Factor: This represents a safety factor which provides added initial illumination sufficient to compensate for aeing of the lamps and the falling off in re- flecting efficiency of the reflectors, walls, and ceilings due to deterioration and the collection of dust and dirt. A depreciation factor should always be applied to the recommendations for foot-candles of illumination since these are always stated in terms of average service, or sustained illumination. 14 varies rather widely depending on the conditions in any par- ticular installation, such as the accuracy of the operation and fineness of detail to be observed, the color of goods worked on or handled and, in the case of stores, the advertising value re- sulting from the attractiveness of a well lighted interior. The foot-candle values recommended in the table are the minimum to .be adhered to if fully satisfactory lighting is to be assured. Under particular conditions considerably higher illumination is often desirable. 2. Type of Lighting Unit The selection of the type of lighting unit depends not only upon the requirements of the work but in some cases upon the construction of the room and the color of ceiling and walls. For example, semi and totally indirect lighting is unsuited to rooms with very dark ceilings. It is important to specify the type of lamp to be used since, for example, as shown in Table I, bowl- enameled lamps used in open reflectors, such as RLM standard domes, form a much superior lighting unit from the standpoint of glare, reflected glare, and shadows than clear lamp units of the same type. In general, clear MAZDA C lamps should not be used in open reflectors where the mounting height is less than 20 feet. Factors other than those listed in Table I may enter into the choice of the lighting unit in certain instances. For example, in stores, offices and other public installations, decorative effect is often an important item. The charts on pages 21 and 22 rate the various types of units comparatively to serve as a basis for judgment of the adaptability of a unit for a particular class of installation. 3. Location of Outlets, Mounting Heigjht, and Number of Light- ing Units Make a diagram to scale of the floor area of the room. If the units are of semi or totally indirect type, measure the ceiling height of room and refer to Table 2-b, page 24, for the permissi- ble spacing of units and preferred suspension distance of lighting units corresponding to this ceiling height. If the units are of direct lighting type, determine the mount- ing height and refer to Table 2-a for the permissible spacing cor- responding to this mounting height. If the units are mounted as close to the ceiling as possible (a minimum allowance of one foot is usually necessary to provide for the drop of the reflector 15 from the ceiling), a wider spacing is permissible and fewer units are therefore necessary for an even distribution of light. Con- siderations of shadows, appearance and arrangement of work may make a lesser mounting height desirable even though a closer spacing of outlets would be needed to keep the same uni- formity of illumination. Ordinarily lamps should not be mount- ed less than 10 feet above the floor unless a low ceiling makes it necessary. Having determined the permissible spacing proceed to locate the outlets on the diagram of the floor area. Locate the units as nearly symmetrically as possible without appreciably exceeding the permissible spacing for uniform illumination. At a greater height, a spacing closer than that in Table 2 results in greater freedom from shadows but increases the number of units re- quired and makes the installation cost more. If a spacing some- what closer than the permissible value is adopted, as is often the case, it is allowable, though not necessary, to refer back to Table 2 and select a lower mounting height corresponding to the new spacing. The distance between the outside row of outlets and the wall should not exceed one-half the spacing distance. For office spaces, or where work is carried on at benches or machines near the wall, this distance should be approximately one-third the spacing distance. 4. Lamp Size After the outlets have been located on the plan, the lamp size to be used may be determined by the following calculation: Area in Square Feet _ Total Floor Area in Square Feet Per Outlet Number of Outlets Lamp Lumens Foot- Candles x Depreciation Factor .D Jxequirea per = ^= ; ; Square Foot Coefficient of Utilization Lamp Lumens Area in Square Feet Lamp Lumens Required C Required per = , per Outlet X per Square Foot Outlet (From A) (From B) Foot-Candles Illumination decided upon. Depreciation Factor Safety factor or allowance for depreciation due to aging of lamps, dirt, dust, and deterioration of reflecting value of walls. Use 1.3 for fairly clean locations. Use 1.5 for dirty locations or where cleaning is infrequent. Coefficient of Utilization Proportion of the generated light from the lamps which reaches the plane of work. The Coefficient of Utilization for tlje jnstajlalion is determined as follows : 16 Table 5, pages 32 to 35, shows that the Coefficient of Utilization varies according to the type of fixture, the proportions of the room expressed by "Room Index," and the color of the walls and ceiling. From the "Room Index" Table 6, pages 36 to 42, find the Room Index corresponding most nearly to the dimensions of the installation. Then the Coefficient of Utilization for the installation of the type of lighting unit selected will be found from Table 4, in the proper column of wall and ceiling color opposite the correct Room Index. Having determined the lamp lumens required per outlet by the above calculations, the wattage of MAZDA lamps to be used may be found by reference to Table 7, page 43, which lists the lumen output rating for each size of MAZDA and MAZDA Daylight lamps. Locate in this table the size of lamp of the desired type which most nearly meets the requirement of lumen output. When the lamp lumens required fall nearly midway between two sizes, choose the larger rather than the smaller, unless it is cer- tain that the less illumination from the smaller will suffice. Computed Illumination Values The foot-candles of illumination in service, allowing a de- preciation factor of 1.3, obtained for systems having different Coefficients of Utilization and areas per lamp are worked out in Table 8, pages 44 and 45. Table 8 can be referred to as an approximate check on design computations made as outlined above. ILLUMINATION DESIGN FOR A FACTORY ROOM The floor plan of the factory space to be lighted is 60' x 120' as shown. The work carried on in the room is assembly of sewing machine heads. Height of floor to roof trusses is 12 feet. The roof is of sawtooth construction and the walls and upper structure are painted a medium color. A considerable amount of dark material is kept stacked along the walls of the room. Following the steps outlined on Pages 14 to 17 the lighting design is de- termined as follows: 1. Foot-Candle Illumination From Table 4, Page 27, 8 foot-candles are recommended for assembly, medium grade. 2. Type of Lighting Unit Consulting the Guide to the Selection of Reflecting Equipment of Table i, Page 21, Unit No. 2, the RLM dome with bowl- enameled lamp is selected based on efficiency and favorable showing from the standpoints of glare, reflected glare, shadows, and maintenance. 3. Location of Outlets, Mounting Height, and Number of Units The height of the benches and therefore the plane of work is 3 l / 2 \ above the floor. The maximum mounting height of the lamps above the floor is n' (12' height from floor to truss less i' allowed for reflector drop). Hence, maximum mounting height of units above plane of work is n' S 1 /* or 7^'. 17 From Tauie 2-a of Spacing-Mounting Height, Page 23, a 7^2' mounting height above plane for direct lighting units is found to indicate a per- missible spacing of approximately n' and since the section of the room near the walls consists of aisles and storage, 5^' may be allowed for the distance between the last row of outlets and the side walls. Reference to floor plan of the room shows that a id' spacing each way (outside units 5' from walls) would make a symmetrical layout in the 20' x 30' bays and this spacing is therefore adopted. Outlet locations for the entire space are marked on the plan as shown and 72 are found to be required. 4. Lamp Size (A) Area in Total Floor Area in Sq Ft ?2QO Number of Outlets in Room ' ~^ ' .0' 0-f a .0 fl .0- .0 A ' * " ir B H * ^r--=--^--^--| . M t=-^r===r* b__mi fl K .0 $ !0 8 * n t* * ; .0 aj tt 'Outlet for 1-150 waU bowl enameled MAZDA C lamp .equipped with an QLM 5t A- B B B+ B B+ A- 3 GLASS TOP DOME jk Boivl.F-nameled [.amp 90 to 180 8%i 0to90-55'/. B C+ A- A- B B+ B 4 DEEP BOWL A Clear Lamp 90 to 180' 0% ^5 r~4^\ 0to90-5% B+ B- C C+ D C A 5 DEEP BOWl Bowl-Enameled Lamp 0to90-S8Sl B C+ C B C+ C+ B+ 3 FLAT CONE Shielding Band -55 AK\ (r-,90'_54% B C+ C+ C-H D C B+ 7 FLAT CONE 3F Clear Lamp, l ,y to 180" W-k to 90 74^1 B B C D D C A+ I DIRECT LIGHTING OPEN GLASS REFLECTORS 8 LIGHT Sin OPAL A Clear Lamp! 90 to 180 ii'i 0* to 90 54% B+ B B-f C+ D B- B 9 LIGHT DENSITY OPAL Bowl-Enameled Lamp 90 to 180 36"* ^ms ^W^ O'to90 S% B B- A- B- B- B+ B~ 10 DENSE OPAL, Clear Lamp 90 to 180 15".) ?L5 to 90 67^ A+ B+ C+ B D C+ A- II DENSE OPAL Bowl-Enameled Lamp 90 to 180 16%l B+ B- A- B+ B- B B 12 MIRRORED GLASS Clear Lamp 90 to 180 0'* 0to90-68-H A B C C+ D C A- 13 MIRRORED GLASS Boul-Enameled Lamp 90 to 180- 0% M to 90 55^ B C+ C B- C C+ B- (4 PRISMATIC NDUSTRIAl ^^ A+ A- B+ C+ D C+ C- 21 TABLE 1 A GUIDE TO THE SELECTION OF REFLECTING EQUIPMENT LIGHTING UNIT EFFICIENCY BASED UPON ILLUMINATION ILLUMINATION ON HORIZONTAL ON VERTICAL MUDDLE IPPEARANCE OF LIGHTED ROOM DIRECT GLARE REFLECTED GLARE SHADOWS MAINTENANCE DIRECT LIGHTING ENCLOSING AND SEMI-ENCLOSING UNITS 15 TOHF B- B- B- B+ 16 B+ B+ SEMI-ENCLOSING Compo Reflector 19 A- A- 20 B+ B+ A- 21 B+ B+ A- SCIN-MDIRECT AND INDIRECT LIGHTING UNITS 22 LIGHT OPAL B- C+ B+ B+ A- 23 DENSE OPAL (or Light Opal and Bowl-Enameled Lamp) c+ A+ 24 B- B+ B+ 25 ENAMELED METAL REFLECTOR c+ A+ 26 A+ MIRRORED INDIRECT 27 28 C+ B+ B+ A+ A+ A+ A+ TABLE 2-a SPACING MOUNTING HEIGHT Direct Lighting Units, Including Semi-enclosing and Totally Enclosing Units, No. 1 to No. 21 Mounting Height Permissible Distance Between of Unit Permissible Outlets and Sidewalls Distance Above Plane of Work Above Floor* Between Outlets I n Usual Loca- tions Where Aisles & Storage Are Next to Wall In Offices or Where Work Benches are Next to Wall (H) (F) (D) (W) (W) 4 6^ 6 3 2 5 7> 7/4 31^ 2> 6 gi^ 9 4X 3 7 914 iox 5 3>4 8 iox 12 6 4 9 \\y 2 13X 6J4 4j^ 10 \iy 2 15 7/4 5 11 13K 16^ 8 5> 12 14X 18 9 6 13 15^ 19X 9J4 6X 14 16^ 21 10>^ 7 15 17>^ 22^ 11 7K 16 18X 24 12 8 18 20^ 27 13^ 9 20 22^ 30 15 10 22 24^ 33 16^ 11 24 26X 36 18 12 27 29^ 40X 20 13> 30 32> 45 22^ 15 35 37^ 52^ 26 17X 40 42X 60 30 20 *Plane of work (P) assumed to be 2 % feet above floor. When the plane of work is higher or lower than 2^ feet above floor, neglect column (F) and work from column (H). **Minimum allowance for (R) usually 1 foot. 23 TABLE 2-b SPACING MOUNTING HEIGHT i and Totally Indirect Lighting Units, No. 22 to No. 28 Ceiling Height Permissible Distance Between Permissible Outlet and Sidewalls Suspension Spacing Distance Between Outlets In Usual Locations Where Aisles and Storage In Offices or Where Work Benches Are Distance Ceiling to Top of Reflector** Above Plane of Above Floor* Work Are Next Next to Wall to Wall (H) (C) (D) (W) (W) (R) 5 7X 7X Zy 2 2X IX 6 8> 9 4> 3 iy* 7 9K 10X 5 3X ix 8 10# 12 6 4 2 9 nx 13^ 6>^ 4> 2X 10 12^2 15 iy 2 5 2X 11 13JS2 16^2 8 5> 2X 12 14> 18 9 6 3 13 15X 19^ 9^ 6>^ 3X 14 16X 21 10.K 7 3}4 15 17^ 22^ 11 7X 3X 16 18> 24 12 8 4 18 20^ 27 13X 9 4^ 21 23X 31^ 15i^ 10>4 5X 24 26X 36 18 12 6 27 29^ 40X 20 13^ 6X 30 32X 45 22^ 15 7X 35 37^ 52^ 26 17> 8X 40 42^ 60 30 20 n T P \ *Plane of work (P) assumed to be 2 K" feet above floor. When the plane of work is higher or lower than 2> feet above floor, neglect column (C) and work from column (H). **Suspension distances (R) in Table are based on best distribution of light and efficiency of utilization for standard units. In some installations other con- siderations may require a different suspension distance. 24 TABLE NO. 3 Present Standards of Foot- Candles Illumination for Stores, Commercial and Public Interiors Foot-Candles Recommended Range Department Stores and Large Specialty Stores Main Floors 10 6-12 Basement Store 10 6-12 Other Floors 8 5-10 Show Windows . . 10-100 Stores of Medium Size Clothing, Dry Goods, Furniture, Etc 8 5- 10 Exclusive Small Stores Light Goods .* 8 5- 10 Dark Goods 12 8- 16 Small Stores Art 8 5-10 Automobile Supply 6 4- 8 Bake Shop 6 4- 8 Book 6 4- 8 China 6 4- 8 Cigar 8 5-10 Clothing 8 5- 10 Confectionery 8 5- 10 Dairy Products 6 4- 8 Decorator 8 5- 10 Drug 8 5-10 Dry Goods 8 5- 10 Electrical Supply 8 5- 10 Florist 6 4- 8 Furrier 8 5- 10 Grocery 6 4- 8 Haberdashery 8 5- 10 Hardware 6 4- 8 Hat 8 5-10 Jewelry 8 5-10 Leather, Handbags and Trunks 6 4- 8 Meat 6 4- 8 Millinery 8 5- 10 Music 6 4- 8 Notions 6 4- 8 Piano 6 4- 8 Shoe 8 5-io Sporting Goods 6 4- 8 Tailor 8 5-10 Tobacco 8 5- 10 Variety Store 10 6-12 Armories, Public Halls 5 3- 6 Auditoriums 3 2- 4 Automobile Show Room 8 5- 10 Bank Lobby : 6 4- 8 Cages and Offices 10 6-12 Barber Shop 8 5- 10 Cars Baggage 4 3- 6 Daycoach, Subway 6 4- 6 Dining 6 4- 8 Mail 10 6-12 Pullman 6 4- 8 Street Ry .. 6 4- 8 25 TABLE NO. 3 (Continued) Present Standards of Foot-Candles Illumination for Stores, Commercial and Public Interiors Foot-Candles Recommended Churches Auditorium 3 Sunday School Room 5 Club Rooms 4 Dance Halls 4 Dental Office Waiting Room 4 Office . 15 Depot Waiting 4 Drafting Room 15 Elevators Freight and Passenger 4 Gymnasiums Main Exercising Floor 8 Swimming Pool 4 Shower Rooms 4 Locker Rooms 4 Fencing, Boxing, Wrestling 8 Halls, Passageways in Interiors 2 Hospitals Lobby and Reception Room 4 Corridors 3 Wards and 1 with local illumina t ion 3 Private Rooms ^{V no n loc . al lamination .... 6 J night illumination o. I Operating Table 75 Operating Room 10 Laboratories 10 Hotels Lobby 4 Dining Room 5 Kitchen 6 Bedrooms 6 Corridors I Writing Room 8 Indoor Recreations Basketball and Indoor Baseball 10 Bowling (On Alley, Runway and Seats) 5 (On Pins) 15 Billiards (General) 4 (On Table) 15 Racquet, Handball, Squash and Indoor Tennis... 15 Skating Rinks 5 Library Reading Rooms 8 Stack Room 4 Lodge Rooms 4 Lunch Room 8 Market 8 Moving Picture Theatre During Intermission 3 During Pictures o. i Museum (General) 5 (On Walls) 8 Range 2- 4 3- 6 3 ~ 3- 6 3- 6 10- 20 3- 6 10- 20 3- 6 5- 10 3- 6 3- 6 3- 6 5- 10 i- 4 3- 6 2- 4 2- 4 4- 8 O.I-O.2 50-100 6- 12 6- 12 3- 6 4- 8 4- 8 4- 8 1- 2 5- 10 6- 12 3- 6 10- 20 3- 6 10- 20 10- 20 4- 8 5- 10 3- 6 3- 6 5- 10 5- 10 2- 4 O. 1-0.2 4- 8 5- 10 26 6- 12 6- 12 3- 6 6- 12 TABLE NO. 3 (Continued) Present Standards of Foot-Candles Illumination for Stores, Commercial and Public Interiors Foot-Candles Recommended Range Office Buildings General Office 10 Private Offices 10 File Room. . . \ 4 Stenographer and Bookkeeping Rooms 10 Vault 4 Restaurants 5 Schools Auditorium 5 Class Rooms, Library, and Office 8 Corridors and Stairways 3 Drawing 15 Laboratories 10 Manual Training 10 Sewing Rooms 15 Study Room Desks 8 Blackboards 6 Studio Art and Photographic 10 Moving Picture General 5 Sets (Photographic Daylight) .. 500-2000 Telephone Manual Exchanges 5 3- Automatic Exchanges 10 6- Theatres Auditorium 4 x 3- Foyer 5 3- Lobby 5- Toilet and Washrooms 5 3- 4- 8 5- 10 2- 4 10- 20 6- 12 6- 12 IO- 20 10 6 12 6 6 TO Foot-Candles Recommended TABLE NO. 4 Present Standards of Foot-Candles Illumination for Industrial Interiors Range Offices Private, General 10 6-12 Drafting Room 15 10-20 Industrial Aisles, Stairways, Passageways and Corridors.... 2 1-2 Assembling Rough 5 3-6 Medium 8 5-10 Fine 10 8-16 Extra Fine 10-50 Automobile Storage 3 2 ~ 4 Bakeries 8 5-10 Boilers, Engine Rooms and Power Houses Boilers, Coal and Ash Handling, Storage Battery Rooms 3 2 -4 Auxiliary Equipment, Oil Switches and Trans- formers 5 3-6 Switch Boards, Engines, Generators, Blowers, Compressors 6 4-8 27 TABLE NO. 4 (Continued) Present Standards of Foot-Candles Illumination for Industrial Interiors Foot-Candles Recommended Range Book Binding Folding, Assembling, Pasting, etc 5 3-6 Cutting, Punching, and Stitching 8 5-10 Embossing 10 8-12 Candy Making 8 5-10 Canning and Preserving 8 5-10 Chemical Works Hand Furnaces, Boiling Tanks, Stationary Driers, Stationary or Gravity Crystallizing 3 2-4 Mechanical Furnaces, Generator and Stills, Me- chanical Driers, Evaporators, Filtration, Mechan- ical Crystallizing, Bleaching 4 3-6 Tanks for Cooking, Extractors, Percolators, Nitra- tors, Electrolytic Cells 6 4-8 Clay Products and Cements -Grinding, Filter Pressing, Kiln Rooms 3 2-4 Molding, Pressing, Cleaning and Trimming 5 3~ 6 Enamelling 6 4-8 Coloring and Glazing 10 6-12 Cloth Products Cutting, Inspecting, Sewing Light Goods 10 6-12 Dark Goods 20 10-50 Pressing, Cloth Treating (Oil Cloth, etc.) Light Goods 8 5-10 Dark Goods 12 8-16 Coal Breaking & Washing, Screening 3 2-4 Construction Indoor General 3 2-4 Dairy Products 6 5-10 Electric Manufacturing Storage Battery, Molding of Grids, Charging Room, 6 4-8 Coil and Armature Winding, Mica Working, In- sulating Processes 10 8-16 Elevator, Freight and Passenger 5 3-6 Engraving 20 10-50 Forge Shops and Welding Rough Forging 6 4-8 Fine Forging and Welding 10 6-12 Foundries Charging Floor, Tumbling, Cleaning, Pouring* and Shaking Out* 5 3-6 * Since Pouring and Shaking Out are carried on in the same location as either Rough or Fine Molding, different illumination levels may be secured for these operations by cutting out some of the lighting circuits when space is used for the former. Rough Molding and Core Making 6 4-8 Fine Molding and Core Making 10 6-12 Glass Works Mix and Furnace Rooms, Pressing and Lehr, Glass Blowing Machines 8 5-10 Grinding, Cutting Glass to Size, Silvering 8 5-10 Fine Grinding, Polishing, Beveling, Inspection, Etching and Decorating 10 6-12 Glass Cutting (Cut Glass), Inspecting Fine 10-50 28 TABLE NO. 4 (Continued) Present Standards of Foot- Candles Illumination for Industrial Interiors Foot-Candles Recommended Range Glove Manufacturing Light 'Goods Cutting, Pressing, Knitting ..................... g 5-10 Sorting, Stitching, Trimming and Inspecting.... 10 8-16 Dark Goods Cutting, Pressing, Knitting .................... IO g_ I2 Sorting, Stitching, Trimming and Inspecting. ... 20 10-50 Hat Manufacturing Dyeing, Stiffening, Braiding, Cleaning and Refining ^ght ................................. ....... 6 4 _ 8 D ark ..... ....... ............................ 10 6-12 Forming. Sizing, Pouncing, Flanging, Finishing, Ironing Light ........................................ 8 5-10 ' Dark ......................................... 10 6-12 bewmg Light ........................................ 10 8-16 Dark ......................................... IO _ 5o ice Making Engine and Compressor Room ................... 6 4-8 Inspecting Rough ........................................... 6 4 _ 8 Medium ....................................... 10 6-12 Fine ............................................ IS 10-20 Extra Fine ................................ ..... 10-50 Jewelry and Watch Manufacturing .................. 10-50 Laundries and Dry Cleaning .......................... 8 5-10 Leather Manufacturing Vats ......... . ................................. 3 2-4 Cleaning, Tanning and Stretching ................ 4 3-6 Cutting, Fleshing and Stuffing .................... 6 4-8 Finishing and Scarfing .......................... 10 6-12 Leathing Working Pressing and Winding Light ........................................ 8 5-10 Dark ........................................ 10 6-12 Grading, Matching, Cutting, Scarfing, Sewing Light ........................... ............. 10 8-16 Dark .................................... . ____ 10-50 Locker Rooms ..................................... 4 2-4 Machine Shops Rough Bench and Machine Work ..... ............ 6 4-8 Medium Bench and Machine Work, Ordinary Au- tomatic Machines, Rough Grinding, Medium Buf- fing and Polishing ............................ 10 6-12 Fine Bench and Machine Work, Fine Automatic Machines, Medium Grinding, Fine Buffing and Polishing ..................................... 12 8-16 Extra Fine Bench and Machine Work, Grinding (fine work) .................................. 10-50 Meat Packing Slaughtering ................................... 5 3-6 Cleaning, Cutting, Cooking, Grinding, Canning, Packing ...................................... 8 5-10 29 TABLE NO. 4 (Continued) Present Standards of Foot-Candles Illumination for Industrial Interiors Foot-Candles Recommended Range Milling and Grain Foods Cleaning, Grinding or Rolling 5 3-6 Baking or Roasting 8 5-10 Flour Grading 16 10-20 Packing Crating 4 3-6 Boxing 6 4-8 Paint Manufacturing 6 4-8 Paint Shops Dipping, Spraying, Firing 5 3-6 Rubbing, Ordinary Hand Painting and Finishing. . 8 5-10 Fine Hand Painting and Finishing 10 8-16 Extra Fine Hand Painting and Finishing (Automobile Bodies, Piano Cases, etc.) 15 10-50 Paper Box Manufacturing Light 6 48 Dark 8 5 10 Storage of Stock 3 2-4 Paper Manufacturing Beaters, Machine, Grinding 4 3-6 Calendaring 6 4-8 Finishing, Cutting and Trimming 8 6-12 Plating 5 3-6 Polishing and Burnishing 8 5-10 Printing Industries Matrixing and Casting, Miscellaneous Machines, Presses 8 5-10 Proof Reading, Lithographing, Electrotyping 10 6-12 Linotype, Monotype, Typesetting, Imposing Stone, Engraving 10-50 Receiving and Shipping 4 3-6 Rubber Manufacturing and Products Calendars, Compounding Mills, Fabric Preparation, Stock Cutting, Tubing Machines, Solid Tire Op- erations, Mechanical Goods Building, Vulcanizing 8 5 10 Bead Building, Pneumatic Tire Building and Fin- ishing, Inner Tube Operation, Mechanical Goods Trimming, Treading 10 6-12 Sheet Metal Works Miscellaneous Machines, Ordinary Bench Work. . . 8 5-10 Punches, Presses, Shears, Stamps, Welders, Spin- ning, Fine Bench Work 10 8-16 Tin Plate Inspection 10 6-12 Shoe Manufacturing Hand Turning, Miscellaneous Bench and Machine Work 8 5-10 Inspecting and Sorting Raw Material, Cutting, Lasting and Welding (light) 10 6-12 Inspecting and Sorting Raw Material, Cutting, Stitching (dark) 10-50 Soap Manufacturing Kettle Houses, Cutting, Soap Chip and Powder... 5 3-6 Stamping, Wrapping and Packing, Filling and Packing Soap Powder 6 4-8 30 TABLE NO. 4 (Continued) Present Standards of Foot-Candles Illumination for Industrial Interiors Foot-Candles Recommended Range Steel and Iron Mills, Bar, Sheet and Wire Products Soaking Pits and Reheating Furnaces 3 2-4 Charging and Casting Floors ; 5 3-6 Muck and Heavy Rolling, Shearing, rough by gauge, Pickling and Cleaning 6 4-8 Plate Inspection 10 6-12 Automatic Machines, Rod, Light and Cold Rolling, Wire Drawing, Shearing, fine by line 8 5-10 Stone Crushing and Screening Belt Conveyor Tubes, Maine Line Shafting Spaces, Chute Rooms, Inside of Bins 2 1-2 Primary Breaker Room, Auxiliary Breakers under Bins ... 3 2-4 Screen Roms 5 3-6 Store and Stock Rooms Rough 3 2 -4 Medium 6 4-8 Structural Steel Fabrication 6 4-8 Sugar Grading 16 10-20 Telephone Manual Exchanges 5 3-6 Automatic Exchanges 10 6-12 Testing Rough 5 3-6 Fine 10 6-12 Extra Fine Instruments, Scales, etc 20 10-50 Textile Mills (Cotton) Opening and Lapping, Carding, Drawing, Frame Roving, Dyeing 5 3-6 Spooling, Spinning, Drawing in, Warping. Weav- ing, Quilling, Inspecting, Knitting, Slashing (over beam end) 8 5-10 (Silk) Winding, Throwing, Dyeing 12 8-16 Quilling, Warping, Weaving and Finishing Light Goods 8 .S-io Dark Goods 10 8-16 (Woolen) Carding, Picking, Washing and Combing 4 3-6 Twisting and Dyeing 6 4-8 Drawing in, Warping Light Goods 6 4-8 Dark Goods 10 8-16 Weaving Light Goods 8 5-10 Dark Goods 12 10-20 Knitting Machine TO 6-12 Tobacco Products 5- Toilet and Wash Rooms 4 3-6 Warehouse 2 1-2 Wood Working Rough Sawing and Bench Work 5 3-6 Sizing, Planing, Rough Sanding, Medium Machine and Bench Work, Gluing. Veneering, Cooperage 5-io Fine Bench and Machine Working, Fine Sanding and Finishing 6-12 31 TABLE 5. COEFFICIENTS OF UTILIZATION Find Rocm Index, from Table 6. DIRECT LIGHTING PORCELAIN ENAMEL REFLECTORS COLOR REFLECTION FACTOR CEILING VERY LKHT (70%) FAIRLY LIGHT (50%) FAIRLY BARK (30%) WALLS FAIRLY LIGHT (50%) FAIRLY DARK (30%) VERY DARK (10%) FAIRLY LIGHT (50%) FAIRLY DARK (30%) VERY DARK (10%) FAIRLY DARK (30%) VERY DARK (10%) REFLECTOR TYPE ROOM INDEX COEFFICIENTS OF UTILIZATION 1 R I M DOME ^k Clear Lamp 90tol8p-% 0to90-76% 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .34 .42 .46 .50 .53 .58 .62 .64 .67 .69 .29 .38 .43 .47 50 .55 .59 .61 .65 .67 .24 .34 .39 .43 .46 .51 .56 .58 .63 .65 34, .42 .45 .49 .52 .57 .61 .63 .66 .67 .29 .37 .42 .46 .49 .54 .58 .60 .64 .66 .24 .33 .39 .43 .46 .51 .56 .58 .62 .64 .28 '.37 .42 .45 .48 53 58 .60 .63 .65 .24 .33 .39 .42 .45 51 56 .58 .61 .63 2 RIM DOME ^Afct jiiiJKik. Bowl-Enameled Lamp 0to90-66% 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .32 .40 .43 .46 .48 .52 36 .57 .60 .61 .28 .36 .39 .43 .45 .50 .54 .55 .58 .59 .25 .34 .37 .41 .43 .48 .52 .53 .56 .57 .32 .39 .42 .45 .47 .51 .55 .56 .59 .60 .28 .35 .39 .43 .45 .49 .53 .54 .57 .58 .25 .33 .37 .41 .43 .47 .51 .52 .55 .57 .27 .35 .39 .43 .45 .49 53 54 57 .58 .25 .33 .37 .41 .43 .47 .51 .52 55 .56 3 GLASS TOP DOME jnHHtL 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .28 .34 .38 .41 .43 .47 .50 .51 .53 .55 .25 .31 .35 .38 .40 .44 .47 .49 .51 .53 .22 .29 .33 .36 .38 .42 .45 .47 .50 .51 .27 .33 .36 .39 .41 *5 .48 .49 .51 .52 .24 .30 .34 .37 .39 .43 .46 .47 .49 .50 .22 .28 .32 .35 .37 .41 .44 .46 .48 .49 .23 .30 .33 .36 .38 .41 .44 .46 .48 .49 .21 .28 .32 .35 .37 .40 .43 .45 .47 .48 Bowl-Enameled Lamp 90" to 180 8% 0to90-55% 4 DEEP BOWL Clear Cm* 90 to 180 0% 0to90-65% 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .31 .38 .41 .44 .47 .51 .54 .56 .58 .60 .26 .34 .38 .41 .44 .48 .51 .54 .56 .58 .23 .31 .35 .38 .41 .45 .49 .51 .54 .56 .30 .37 .41 .44 .46 .50 .53 .55 .57 .58 .26 .34 .38 .41 .43 .47 .51 .53 .55 .57 .23 .31 .35 .38 .41 .45 .49 .51 .54 .55 .25 .33 .37 .40 .43 .47 .51 .53 55 .56 .23 .31 .35 .38 .41 .45 .49 .51 .53 .55 5 90 tol80--0% to 90 58% 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .29 .35 .38 .41 .44 .47 .50 .51 .53 .54 .26 .33 .36 .39 .41 .45 .48 .49 .51 .52 .23 .31 .34 .37 .39 .43 .46 .47 .50 .51 .29 .35 .38 .41 .43 .46 .49 .50 .52 .53 .26 .32 .36 .39 .41 .44 .47 .48 .50 .51 .23 .30 .34 .37 .39 .43 .46 .47 .49 .50 .25 .32 .35 .38 .40 .43 .46 .47 .49 .50 .23 .30 .34 .37 .39 .43 .46 .47 .49 .49 6 FLAT CONE Shielding Band 9Q''tol80''-l% to 90 54". 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .27 .32 .35 .38 .40 .43 .46 .47 .49 .50 .23 .30 .33 .36 .38 .41 .44 .45 .47 .48 .21 .28 .31 .34 .36 .39 .42 .43 .46 .47 .26 .32 .35 .37 .39 .42 .45 .46 .48 .49 .23 .29 i .41 ,43 .44 .46 .47 .21 .27 .31 .34 .36 .39 .42 .43 .45 .46 .23 29 .32 .35 .37 .40 .43 .44 .46 .47 .21 27 .31 .34 .36 .39 .42 .43 .45 .46 7 FLAT CONE Clear Lamp 90 to 180 10% 0to90 74% 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .26 .32 .36 .41 .44 .50 54 .57 .62 .65 .20 .26 .30 .35 .38 .44 .48 .51 .56 .60 .16 .22 .26 .30 .33 .38 .42 .46 .51 .54 .26 .32 .36 .39 .42 .48 .52 .55 .60 .62 .19 .26 .30 .34 .37 .43 .47 .50 .54 .56 .16 .22 .26 .30 .33 .38 .42 .45 .50 .53 .19 .26 .30 .33 .36 .42 .46 .49 53 .55 .16 ' .22 .26 .30 .33 .38 .42 .45 .50 .53 TABLE 5. COEFFICIENTS OF UTILIZATION Find Room Index from Table 6. DIRECT LIGHTING OPEN GLASS REFLECTORS COLOR CEILING VERY LIGHT 00%) FAIRLY LIGHT (50%) FAIRLY DARK (30%) REFLECTION FAIRLY FAIRLY VERY FAIRLY FAIRLY VERY FAIRLY VERY FACTOR LIGHT (50%) DARK (30%) DARK 00%) LIGHT (50%) DARK (30%) DARK (10%) DARK (30%) DARK (10%) REFLECTOR nPE ROOM INDEX COEFFICIENTS OF UTILIZATION LIGHT DENSITY OPAL 0.6 .26 .21 .17 .24 .19 .16 .18 .15 J. x^ 0.8 32 .27 .23 30 .25 .22 .24 .21 ff 1m 1.0 36 31 .27 34 .29 .26 .27 .24 // \\|i 1.25 .40 35 .31 37 .32 .29 30 .27 . Clear Lamp 1.5 .44 38 .34 .40 35 32 32 30 90tol80-33% 2.0 .49 .44 .39 .45 .40 .37 37 .34 XU.// 25 .53 .48 .44 .49 .44 .41 .40 38 ]U|^[ 3.0 .56 51 .47 .51 .46 .43 .42 .40 -^<\\^- 4.0 .60 .55 .51 .55 .50 .47 .46 .44 to 90' 54% 5.0 .62 58 .54 .57 .53 .50 .48 .46 LIGHT DENSITY OPAL 0.6 .22 .17 .14 .20 .16 .13 .14 .12 y^v 0.8 .27 .22 .19 .25 .21 .18 .19 .16 w ^\\!^ 1.0 31 .26 .23 .28 . .24 .21 .22 .19 // *\ 1.25 35 .30 .26 31 .27 .24 .24 .22 q Bow'-Enameled Lamp 1.5 38 33 .29 34 30 .26 .27 .24 90 to 180 36% 2.0 .43 38 34 38 34 .31 30 .28 ^S^^f^ 25 .47 .42 38 .42 38 34 34 31 ~~^,,^~~ 3.0 49 .44 .40 .44 .40 37 36 .33 ^/TN^" 4.0 53 .49 .45 .48 .44 .41 39 37 0to90-^5% 5.0 .56 52 .43 .50 .46 .43 .40 .39 0.6 32 .27 .23 31 .26 .22 .25 .22 0.8 .40 35 31 .38 34 31 33 .30 1.0 .44 39 .36 .42 38 35 37 35 1.25 .47 .43 .40 .46 .42 39 .40 38 15 51 .47 .43 .49 .45 .42 .43 .41 10 90tol80-15% 2.0 .56 .52 .48 .54 .50 .47 .48 .46 >^|^v 2.5 .60 .56 .53 .57 .54 52 .52 .50 "\/\ \^" 3.0 .63 59 55 .60 .56 .54 .54 .52 /T"^\ 4.0 .66 .63 .60 .63 .60 58 .57 .55 0to90-67% 5.0 .67 .65 .62 .65 .61 .59 .59 .57 DENSE OPAL 0.6 .29 .24 .20 .28 .23 .20 .22 .20 s \. .0.8 35 31 .28 34 30 .27 .29 .27 // N\V 1.0 39 35 32 38 34 32 33 31 /// ^a 1.25 .43 39 36 .41 38 35 .36 34 Bowl-Enamcled Lamp 1.5 .46 .42 38 .44 .40 37 .38 36 90 to 180 16% 2.0 51 .47 .44 .48 .45 .42 .43 .41 /^/$% 2.5 .55 .51 .48 52 .49 .46 .47 .45 s\ / XT** 3.0 57 .54 .50 54 .51 .48 .48 .46 VIV 4.0 .60 .57 .54 57 .54 .52 51 .50 0to90-60> 5.0 .62 .59 .56 .58 .56 .54 .53 .52 MIRRORED GLASS 0.6 32 .27 .24 .31 .27 .24 .27 .24 dJJUlUht. 0.8 39 35 32 39 .35 32 35 .32 MMffljj/MMflL 1.0 .43 39 37 .42 39 37 39 37 1.25 .46 .43 .40 .46 .43 .40 .42 .40 I M CKaTL/lrm> 15 .49 .46 .43 .48 .45 .43 .45 .43 12 90 to 180-0% 2.0 53 .50 .48 .52 .50 .48 .49 .48 >^i^V 25 57 .54 52 .56 .54 .52 .53 .52 I . / lAi 3.0 58 .56 .54 .57 .55 .54 54 .53 S^**r v \^ 4.0 .61 .59 57 . .60 .58 .56 .57 .56 to 90-68% 5.0 .63 .61 .58 .61 .59 .58 .58 .57 0.6 .26 .22 .19 .25 .22 .19 .21 .19 0.8 32 .29 .26 31 .28 .26 .28 .26 1.0 35 .32 30 34 .32 .30 31 30 1.25 38 35 33 37 35 33 34 33 13 P 1.5 .40 37 .35 39 37 35 36 35 90 to 180 0% 2.0 .43 .41 39 .42 .40 39 .40 39 2.5 .46 .44 .42 .45 .43 .42 .43 .42 3.0 .47 .46 .44 .46 .45 .44 .44 .43 4.0 .49 .48 .46 .48 .47 .46 .46 .45 5.0 .50 .49 .47 .49 .48 .47 .47 .46 PRISMATIC INDUSTRIAL 0.6 .33 .26 .21 31 .25 .21 .24 .20 vO^- 0.8 .41 .35 30 39 33 .29 .32 .29 ^^'ll\\^ 1.0 .45 .40 35 .43 39 34 37 33 H/nlim 1.25 .50 .44 .39 .47 .42 38 .40 37 Jj/ll III 1 Ul)| 1.5 52 .48 .43 .50 .45 .42 .43 .40 1 i Clear Lamp i^ 90 to 180--187. 2.0 .58 .54 .49 .56 51 .47 .49 .46 >^}X\ 25 3.0 .63 .66 59 .62 54 58 .60 .63 .56 59 .53 .56 .54 .56 .51 54 y*^^^/ \ \ Ss ^^^i 4.0 .71 .67 .63 .67 .63 .61 .60 58 **0'to9V 73%^ 5.0 .73 ,69 .66 .69 .65 .63 .62 .60 33 TABLE 5. COEFFICIENTS OF UTILIZATION Find Room Index, from Table 6. DIRECT LIGHTING ENCLOSING AND SEMI-ENCLOSING UNITS COLOR REFLECTION FACTOR CEILING VERY LIGHT (70%) FAIRLY LIGHT (50%) FAIRLY DARK (30%) WALLS FAIRLY LIGHT (50%) FAIRLY DARK (30%) VERY DARK (10%) FAIRLY LIGHT (50%) FAIRLY DARK (30%) VERY DARK (10%) FAIRLY DARK (30%) VERY DARK (10%) REFLECTOR TYPE ROOM INDEX COEFFICIENTS OF UTILIZATION 15 DIFFUSING GLOBE Li E htOpal 90tol80-35% .0.to90 W 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .18 .22 .26 .29 .32 .37 .40 .43 .47 . .49 .13 .17 .21 .24 .27 .32 .35 .38 .42 .45 .10 .14 .18 .21 .23 .28 .31 .34 .38 .41 .16 .20 .23 .26 .29 .32 .35 .38 .41 .43 .12 .16 .19 .22 .24 .28 .31 .33 .37 .39 .10 .13 .16 .19 .21 .25 .28 .30 .34 .36 .10 .14 .17 .19 .22 .25 .28 .30 .33 .34 .09 .12 .14 .16 .19 .22 .25 .27 .31 .33 16 ONE-PIECE OPAL Flattened Reflecting to 90 45% 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .22 .27 .31 .35 .38 .42 .46 .49 .53 .55' .17 .22 .26 .30 .33 .38 .41 .45 .48 .51 .14 .19 .23 .26 .29 !33 .37 .40 .44 .47 .20 .25 .28 .31 .34 i.38 .41 .43 .47 .49 .16 .21 .24 .27 .30 134 .37 .39 .43 .45 .13 .18 .21 .24 .27 .31 .34 .36 .40 .42 .14 .19 .22 .25 .27 .31 .34 .36 .38 .40 .12 U7 .19 22 .24 .28 .31 .33 .36 .38 17 DIFFUSING GLOBE Large MetalRefleclor V jjj 90tol80-6% ^ to 90-58T. 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .22 28 .31 .34 .36 .41 .44 .47 .50 .52 .17 .23 .26 .30 .32 .37 .41 .43 .47 .49 .14 .20 .23 .26 .29 .33 .37 .39 .43 .45 .22 .27 .31 .33 .36 .40 .43 .45 .48 .50 .17 .23 .26 .29 .32 .36 .40 .42 .45 .47 .14 .19 .23 .26 .28 .33 .37 .39 .43 .44 .17 .23 .26 .29 .31 .35 .39 .41 .44 .46 .14 .19 .23 .26 .28 .32 .36 .39 .42 .44 18 SEMI-ENCLOSING Metal Reflector 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .22 .28 .31 .35 .38 .43 .46 .49 .54 .56 .17 .22 .26 .30 .33 .38 .41 .44 .49 .51 .13 .19 .23 .26 .28 .33 .37 .40 .44 .47 .21 .26 .30 .32 .36 .40 .44 .46 .50 .52 .16 .21 .25 .28 .31 .36 .39 .42 .45 .47 .13 .18 .22 .25 .27 .32 .36 .38 .42 .45 .15 .21 .24 .27 .30 .34 .37 .40 .43 .44 .13 .18 .21 .24 .26 .30 .34 .37' .40 .43 90tol80-20% to 9V 56^ 19 SEMI-ENCLOSING Compo Reflector 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .24 .30 .33 .37 .39 .441 .48 .50 .55 57 .18 .24 .28 .32 .35 .40 .44 .46 .51 .53 .14 .21 .25 .28 .31 .35 .39 .42 .47 49 .23 .29 .32 .35 .38 .42 .46 .48 .53 .54 .18 .24 .28 .31 .34 138 .42 .44 .49 ..50 .14 .20 .24 .27 .30 '.34 .38 .41 .45 .47 .17 .23 .27 .30 .32 .37- .41 .43 .46 .48 .14 .20 .24 .27 .29 .34 .38 .40 .44 .46. 90tol80-13% to 90 60% 20 TWO-PIECE GLASS Opal Reflector and Enameled Bowl ,^=^%l^>x 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .22 .27 .30 .33 .36 : 4 4 .46 .49 .51 .17 .23 .26 .29 .32 .37 .40 .42 .45 .48 .14 .20 .23 .26 .29' .33 .36 .38 '.42' .44 .21 .26 .29 .32 .35 % .43 .47 .48 .17 .22 .26 .28 .31 .35 .38 .40 .43 .45 .14 .19 .23 .26 .28 .32 .35 .37 .41 .43 .16 .22 .25 .29 .31 .34 .37 .39 .42 .43 .14 .19 .22 .25 .27 .31 .35 .37 .40 41 \y 90tol80-127o to 90 53% 21 ONE-PIECE GLASS Enameled Reflector 90 to 180-22% to 90 50% 0.6 0.8 1.0 1.25 1.5 2.0 2.5 3.0 4.0 5.0 .22 .27 .30 .34 .37 .41 .44 .47 .51 .53 .17 .23 .26 .30 .33 .37 .40 .43 .47 .49 .14 :20 .23 .26 .29 .33 .36 .39 .43 .45 .21 .26 .29 .32 .34 .38 .41 .43 .47 .48 .16 .22 .25 .28 .30 .34 .38 .40 .44 .45 .14 .19 .22 .25 .27 .31 .35 .37 .41 .42 .15 .20 .23 .26 .28 .32 .35 .37 .41 .42 .14 .18 .21 .24 .26 .30 .33 .35 .39 .40 34 TABLE 5. COEFFICIENTS OF UTILIZATION Find Rocvn, Index from Table 6. SEMI-INDIRECT AND INDIRECT LIGHTING UNITS COLOR VERY LIGHT (70%) FAIRLY LIGHT (50%) FAIRLY DARK (30%) ssr FAIRLY LIGHT (50%) FAIRLY DARK (30%) VERY DARK (10%) FAIRLY LIGHT (50%) FAIRLY DARK (30%) VERY DARK (10%) FAIRLY DARK (30%) VERY DARK (10%) REFLECTOR TYPE ROOM INDEX COEFFICIENTS OF UTILIZATION LIGHT OPAL 0.6 .18 .14 .11 .15 .12 .09 .09 .07 y Y < 0.8 .22 .18 .15 .19 .15 .12 .12 .10 v^ v 1.0 .26 .22 .18 .22 .18 .15 .14 .12 22 ^^^^X 1.25 .30 .25 .22 .25 .21 .18 .16 .14 1.5 .33 .28 .24 .27 .23 .20 .18 .16 90tol80-60'' 2.0 .38 .33 .29 .31 .27 .24 .21 .19 2.5 .41 .36 .32 .34 .30 .27 .24 .22 ""^^T^^^ 3.0 .44 .39 .35 .36 .32 .29 .25 .23 jVjQ 4.0 .49 .44 .40 .40 .36 .33 .28 .26 to 90-25 5.0 .51 .46 .42 .42 .38 .35 .29 .28 DENSE OPAL 0.6 .16 .13 .11 .12 .10 .08 .07 .06 (or Li e ht Opal and 0.8 .20 .17 .15 .16 .13 .11 .09 .08 Bowl-enameled Lamp) 1.0 .23 .20 .17 .18 .15 .13 .10 .09 / ? \ 1.25 .27 .23 .20 .21 .18 .16 .12 .11 >^ /Mil 1.5 .29 .26 .22 .23 .19 .17 .13 .12 ^^^ ^^^ 90 to 180 70?f 2.0 .33 .29 .26 .26 .22 .20 .15 .14 2.5 .36 .32 .29 .28 .25 .23 .17 .16 ^^JA^" 3.0 .39 .35 .32 .29 .27 .25 .18 .17 ^^^Xf^^ 4.0 .43 .39 .36 .32 .30 .28 .20 .19 to 90 10'* 5.0 .45 .41 .38 .34 .32 .30 .22 .20 ENAMELED 0.6 .18 .15 .13 .14 .12 .11 .09 .08 METAL REFLECTOR 0.8 .22 .19 .17 .18 .16 .14 .12 .11 Opal Glass Bottom 1.0 .25 .22 .20 .20 .18 .16 .14 .13 \\ 1.25 .29 .25 .22 .23 .21 .19 .15 .15 ^^i. ^=^/^~ 1.5 .31 .28 .25 .25 .22 .20 .17 .16 ^ ~_/ 90 to 180 61% 2.0 .34 .31 .29 .28 .25 .23 .19 .18 v*\iy~y^ 2.5 .37 .34 .32 .30 .28 .26 .21 .20 v^sl^x 3.0 .39 .36 .34 .31 .29 .27 .21 .20 /^fv\ 4.0 .43 .40 .38 .34 .32 .30 .23 .22 0to90 14% 5.0 .45 .42 .40 .36 .34 .32 .25 .23 rs 0.6 .16 .13 .11 .12 .10 .08 .07 .06 ._ ' I,, 0.8 .19 .16 .14 .15 .13 .11 .08 .08 ^^ ^f 1.0 .22 .19 .17 .17 .15 .13 .10 .09 Bowl-enameled Lamp 1.25 .25 .22 .19 .20 .17 .15 .11 .10 1C 1.5 .27 .24 .21 .21 .18 .16 .12 .11 25 90tol80-97. 2.0 .31 .28 .25 .24 .21 .19 .14 .13 2.5 .34 .31 .28 .25 .23 .22 .15 .15 V y^ix 1.5 .27 .24 .21 .20 .17 .15 .10 .09 27 mm 90"tol80-805 2.0 .30 .27 .25 .22 .19 .17 .11 .10 2.5 .34 .31 .28 .24 .22 .20 .13 .12 CvT/") 3.0 .36 .33 .30 .26 .24 .22 .14 .13 ^^1^-' 4.0 .40 .37 .34 .28 .26 .24 .15 .14 0to90-0 r /' 5.0 .42 .39 .37 .30 .28 .26 .17 .15 ENAMELED 0.6 .14 .11 .10 .10 .08 .07 .04 .04 METAL INDIRECT 0.8 .17 .14 .13 .13 .10 .09 .06 .05 1.0 .20 .17 .15 .14 .12 .10 .07 .06 W-^ ^^ a/ 1.25 .23 .20 .17 .17 .14 .13 .08 .07 AM x^g^je^ 1.5 .25 .22 .19 .18 .15 .14 .09 .08 yP CO 90tol80 74fr 2.0 ..28 .25 .23 .21 .18 .16 .10 .10 V I / 2.5 .31 .28 .26 .22 .20 .18 .12 .11 P^U^N 3.0 .33 .30 .28 .24 .22 .20 .13 .12 *^^M^y* 4.0 .37 .34 .32 .26 .24 .22 .14 .13 rggg^g S.O .39 .36 .34 .28 .26 .24 .15 .14 35 TABLE 6 ROOM INDEX For Finding Coefficient of Utilization from Table r j Direct Lighting-sou RCES 4 FEET ABOVE WORK PLANE 8i ROOM LENGTH FEET 10 12 14 16 18 20 24 30 35 40 50 60 70 80 100 120 140 170 200 8 10 12 ~14~ 1.0 1.25 1.25 1.25 1.25 1.5 1.5 1.5 1.5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.25 1.25 nr 1.25 1.5 1.5 1.5 1.5 1.5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.5 I7s~ 1.5 1.5 1.5 1.5 1.5 2.0 2.0 2.0 2.0 2.0 2.0 2.5 2.0 2.0 2.0 2.0 2.0 2.0 2.5 2.0 2.5 2.0 2.0 2.5 2.0 2.5 2.0 2.0 2.5 2.5 2.5 2.5 2.5 2.5 16 1.5 n~ 1.5 1.5 1.5 2.0 2.0 2.0 2.0 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 18 ~20~ 24 2.0 2.0 2.0 2.0 2.5 2.5 2.5 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 1.5 2.0 2.5 2.5 2.5 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 1.5 2.0 2.0 2.5 2.5 2.5 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 30 "3? 2.0 2.0 2.0 2.5 2.5 3.0 3.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 sTo~ 2.0 2.0 2.5 2.5 3.0 3.0 3.0 4.0 4.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 40 ^5,, I K,.||.., l.u i: I-'.,,, l,,r.i,, K <.l.,l,,- I liowl .iii.l Upper I'L.i. Fig. No. 1A Typical Store Lighting Luminairet G-Indirect Bowl H-Globe and Cover 1-PrUm.tic Reflector J-Enclosinf Globe K-Seml- Indirect Bowl L-Bowl *nd Reflector ti Fig. No. IB Typical Store Lighting Luminaires M Bowl and Reflector N Semi-Indirect, Enclosing O Enclosing, Light Directing P Semi- Indirect using for example, pendant crystal prisms around the reflector, will be found both attractive and appropriate equipment for lighting jewels and cut glass. The various semi-indirect and totally indirect luminaires are used where light-colored walls and ceilings permit, and when a soft, well-diffused light is desired. TIhe most popular luminaires for store lighting are the en- closing diffusing globes, the present style for reasons of effici- ency as well as decoration being those of the squat shape. These globes are nearly dust-tight and thus require only a relatively small maintenance, besides being capable of softening the dis- comforting brilliancy of the bare gas-filled Mazda lamps with consequent light absorption losses of not more than 20 per cent. 52 Table 2 Lamps Recommended for Store Use Luminaire MAZDA LAMP Wattage Type Finish Open Reflectors 25, 40, 50 50 100, 150, 200 75 Mazda B White Mazda (C) Mazda C Mazda C Clear or Diffusing Bulb Bowl Enameled Diffusing Bulb Enclosing Globes, Semi-Enclosing, Semi-Indirect, or Totally Indirect 75, 100, 150 I 200, 300, 500 $ 150, 200, 300, 500 Mazda C Daylight Mazda Clear Bulb Clear Bulb Window Reflectors 75, 100, 150 100, 150 Mazda C Daylight Mazda Clear Bulb Clear Bulb Floor and Table Lamps 40, 50 50 Mazda B White Mazda (C) Diffusing Bulb Show Cases 25,40 15,25 15 Mazda B (Tubular Bulb) Mazda B (Round Bulb) Mazda B (Candelabra) Clear Bulb Clear Bulb Clear or Diffusing Bulb Wall Brackets With Shade Without Shade 25, 40, 50, 60 75 15 25 25, 40, 50 50 Mazda B Mazda C Mazda B (Flame-Candelabra) Mazda B (Round Bulb) Mazda B White Mazda '(C) Clear Bulb Clear Bulb Diffusing Bulb Diffusing Bulb Diffusing Bulb Candelabra and Decorative Types 25,40 50 25, 40, 50 Mazda B (Round Bulb) White Mazda (C) Mazda B Diffusing Bulb Diffusing Bulb Entrance Enclosing Globes and Hemi- spheres 75, 100 Mazda C Clear Bulb 53 ENTRANCE DOORWAY LIGHTS A well-lighted store requires a brightly illuminated entrance, particularly on a brightly lighted street. Tihe air of welcome and activity is most necessary, and the passer-by who sees a window display should sub-consciously find the entrance clearly defined and attractive. Some merchants find it profit- able to light the side walk in front of their store or at least to use an electric sign which can thus serve a double purpose. An enclosing globe of the ceiling type or a close fitted ceiling hemisphere is recommended for entrance lighting. For the ma- jority of small stores a 75 or loo-watt Mazda C lamp will be sufficient for this purpose. Here, above all else, the luminaire should be dust and insect proof, and when the window's are washed this entrance light should also be cleaned. NIGHT LIGHTS As a protection against robbery after closing hours a lamp well placed and burning all night will illuminate the store suf- ficiently to allow the policeman or watchman to see the whole of the interior. This lamp is usually placed where it will bring into prominence the safe, vault, rear entrance, or specially valu- able stocks. As a rule a 5O-watt Mazda B lamp or a 75 -watt Mazda C lamp is used. An attractive means of supplementing the display window area and providing night illumination, is to keep a wall case in the rear of the store lighted throughout the night. In addition to displaying merchandise an illuminated wall case will sil- houette clearly the figure of anyone moving about in the store. The cost of burning the 5O-watt lamp would not exceed seven cents per night. COLOR MATCHING AND COLOR QUALITY The accurate identification of color is often necessary in merchandising. Clothing and Carpet stores, Haberdashery shops, and ladies apparel rooms especially, should be equipped with some means of reproducing daylight illumination. Mazda Daylight lamps will provide a means of approximating day- light quality, as will some enclosing cased-glass globes, one 54 layer of which is blue glass absorbing some of the red and yellow rays emanating from the regular Mazda C lamp. An effective means of displaying rugs is to install a dual lighting system, one circuit consisting of Mazda daylight and the other of clear bulb Mazda lamps. It is thus possible to show the rug as it appears under both daylight and artificial illu- mination. Merchants selling rugs under these conditions have less returned goods, and will find many dyes wihose tones are visibly enriched by light of a carefully chosen color quality. The Mazda Daylight lamp can be used very appropriately over mirrors in Clothing stores where suits and dresses are tried on. Flower, Fur, Hat, and even Jewelry stores can use them in connection with clear lamps to bring out blue colors in better relation to the reds and yellows. For very accurate color matching and identification, there are available specially designed units employing standard clear bulb Mazda C lamps, the light from which is filtered through a specially designed blue glass screen. One type of color matching unit is for counter use in the lighting of small merchandise, such as silks, ribbons, and neckties. There are also pendant types for suspending in front of mirrors in the examination of wearing apparel in clothing stores. Such color quality of illumination is unrivaled for displays of cravats, ribbons, colored buttons, spool silk and cotton, trimmings, and flowers. SHOW CASE LIGHTING Show cases, both the counter and wall type, are another means at the disposal of the merchant for displaying his goods. They are really miniature show windows and as such should be properly illuminated, else their heavy investment cost and their valuable space is not 100 per cent, capitalized. Show cases are for showing and not storing merchandise. Tf sufficiently illuminated, careful inspection may be made without moving and handling the various articles. There are two types of reflecting equipment preferable for show case lighting; first, the individual mirrored glass reflectors, and, second, the metal trough reflectors extending the length of the case. The illuminated show case shown in Fig. No. 2 illustrates how inconspicuously these latter units can be in- stalled in an all-glass case. The exception to the usual practice of concealing the units as much as possible is in the lighting 55 of candy displays, wax ornaments, etc., where tne merchandise is affected by the heat of the lamps. An attractive method of solving this problem is to use small ornamental lamps on top of the case and thus provide the illumination from outside. The chief consideration is to furnish more illumination in these cases than is supplied for the store itself in order that they will Fig. 2 stand out by contrast; approximately 15 to 25 foot-candles is usually the minimum value. For the lighting of show cases, 25-watt Mazda lamps on 18 to 24-inch centers will be sufficient. Attention is called to the tubular lamps available, and to the small decorative types whose use, clear or colored, should be better known and more extensive. 56 Plan A SHOE STORE THE INSTALLATION AND THE PLAN Interior Illumination Area of Store (48 x 25) 1200 Sq. Ft. Illumination Desired (Table i) Utilization Factor Depreciation Factor (20%) Number of Outlets 9 Ft.-Candles .36 .80 8 Lumens Required per Outlet = 1200x9 = 4690 . 36 x. Sox 8 Use 3OO-watt Mazda C Lamps Wattage per Square Foot of Floor = 2 Show Window Illumination loo-watt Mazda C lamps on i6-inch Centers. Wattage per Square Foot of Window Floor = 15 57 Plan B GROCERY STORE THE INSTALLATION AND THE PLAN v<200W n Interior Illumination Area of Store (40 x 12^) 500 Sq. Ft. Illumination Desired (Table i) 6 Ft. -Candles Utilization Factor 32 Depreciation Factor (20%) 80 Number of Outlets 4 500 x 6 Lumens Required Per Outlet = =r 2930 32x .80 x 4 Use 2oo-watt Mazda C Lamps. Wattage per Square Foot of Floor 1.6 Show Window Illumination Two roc-watt Mazda C Lamps. Wattage per Square Foot of Window Floor = 10. 58 SHOW WINDOW LIGHTING Merchants endeavor to locate their stores not only on busiest streets but on the busier side of the street. The more people that see the merchandise, the more the sales. Consequently in order to realize more fully upon the large investment in window space, it is essential to light up the windows as soon as dusk falls or perhaps even during the daylight, and to keep them working at 100 per cent, efficiency even after the store is closed, as long as pedestrians are abroad. This can be ac- complished by a key switch on the outside of the store, to be operated by a watchman or, in a more satisfactory way, by an automatic time-switch. There should be enough light so that the wlindows are not dim by comparison with those adjacent. The lighting must be designed to conceal the light sources from the vision of the spectators and in addition to so shield and place them that there is no direct reflection from the polished wood or glass back- ground of the window. The usual and an excellent method of concealing the lamps and reflectors is by a cloth or a painted glass valance. The prismatic glass reflectors are best suited for illuminating these transparent advertising valances. In case of deep windows with a long side bordering the entrance, or of open-back show windows, it is of equal importance to con- ceal the units from the back as well as the front by hanging behind them a second cloth valance. In another style of window lighting equipment the lamps sre mounted horizontally in shallow! metal troughs lined with mirrored glass. These can be very inconspicuously installed either at the top or bottom of the window and are easily con- cealed from the rear by having the trough deep, and the metal match the interior trim. Metal partitions fitted across the trough prevent a direct view of bare lamps when the observer is standing at the side of the window. The care that is given to window lighting approaches that of the theatrical stage. Spot lights are used to accentuate parti- cular features. Footlights of approximately one quarter the strength of the overhead lights are used to soften the shadows. For general use a system of alternate clear and Mazda daylight lamps is recommended. This will provide light close enough to daylight quality and yet warm enough for correct color im- 59 pressions of most merchandise. Windows trimmers are now employing colored light to produce the more studied artistic effects and to show merchandise to its best advantage, as de- scribed in the next section. The appearance of a show window arid the attractiveness of the display may be enhanced by the use of side wall brackets and stand lamps. Relatively small wattage lamps will be ample, as such equipment should not be counted upon to illuminate the window but merely to serve as an added attraction. The safe practice in lighting show windows is to use the equipment designed especially for that particular service. There is, however, an exception found in some small stores such as Grocery, Bakery, and Butcher shops. Here the windows do not usually have backgrounds, and displays of merchandise are not given as much decorative consideration as in other types of stores. But non-glaring light is needed and can be excellently provided by locating the outlets as shown in Plan B for the Grocery store. Three or four open deep-bowl glass reflectors mounted at the top of the window about 12 inches from the glass will illuminate the window, supplement the interior light-, ing and will not be objectionable from, the standpoint of glare. SHOW WINDOW EQUIPMENT The principal types of window lighting reflectors are shown in Fig. No. 4. In addition to these there is the trough re- flecting equipment previously metioned. Both the mirrored and prismatic units can be obtained in various styles suitable, as occasion demands, for high, deep, or shallow windows. In some instances adjustable holders are provided permitting the use of one reflector for various types of windows. For color effects the mirrored glass unit, Fig. No. 4 (B) is available With the detachable gelatin color screen shown. The prismatic reflector (A) is also furnished with screens of similar material that can be attached by clips to the bottom of the unit. The reflector (C) uses a glass color cap that fits over the lamp, while the trough reflector can be had with screens of natural colored glass, or gelatin. All of these color-producing devices are easily attached or changed. Combinations of the three primary colors, red, green, and yellow, ordinarily supplied will be sufficient for most needs 60 although with gelatin screens or lamp color dips, there becomes available a large variety of colors. ^ ABC Fig. No. 4. Show Window Reflectors SHOW WINDOW ILLUMINATION CALCULATIONS The planning of the lighting for windows, excepting the artistry and the color harmonies, need not involve the calcu- lations required in designing the general interior illumination. The majority of show windows are practically of a standard lype and with the specially designed equipment the illumina- tion may be determined simply by the proper spacing of the units. The general practice is to use loo-watt Mazda C lamps spaced 18 inches apart. Outside of metropolitan centers, or on dimly lighted streets, this spacing may be increased up to a maximum of 24 inches. For lower illumination a 75-watt lamp would be used. The tendency, however, is towlard higher valuer and in metropolitan districts loo-watt lamps with 12-inch spac- ing is considered good practice. In Plan A, page 57, loo-watt iamps are spaced on about i6-inch centers. As previously explained, in the open-back windows of Grocery, Bakery, and similar stores, the standard window equip- ment should not be used unless a drop curtain or shield is hung behind them. Here again the calculations involved in the gen- eral interior lighting are not necessary. A simple method of planning the lighting on a watt-per-square-foot basis is very convenient and will usually be found satisfactory. This pro- cedure may also be followed and will serve as a check in win- dows, using equipment as shown in Fig. No. 4. 61 Using 3 to 5 watts per square foot will produce a moderately high illumination, while 10 watts per square foot is a good average figure for lighting show windows. The present practice, however, in metropolitan centers, is to use 20 watts per square foot, unless spot lights are employed to supplement the over- head units. On this basis in Plan B, page 58, we will assume 10 watts per square foot. The floor area of each window is 20 square feet, which multiplied by 10 gives 200 watts per window. This is provided by 2 units of 100 watts each. WIRING AND CONTROL The lighting switches should be conveniently located and the wiring system so laid out that flexible and easy control is provided. This applies particularly to Furniture, Rug, and similar stores where certain sections are lighted only when a customer is inspecting merchandise. Switches should be lo- cated near the entrance to a room or department. In case of more than one entrance, three-way switches permitting control at two points will be found convenient. In the wiring of show windows two circuits controlling alter- nate units are frequently advisable. This will permit the use of part of the equipment during the late afternoon when the artificial illumination supplements the failing daylight, or will facilitate the alternation of colors if flashers be connected to one or more circuits. It is important to provide an ample number of convenience outlets, i.e., wall or baseboard receptacles, column outlets, etc., throughout the store. These will eliminate dangling wires and permit easy connections for fans, vacuum cleaners, portable and stand lamps, decorative festoons, department signs, and elec- trical display devices. Show windows should also be equipped with auxiliary outlets for fans, electrical displays, etc., and particularly with one or more receptacles at the front edge or corner of the window, top and bottom, for spot lights. The foresighted merchant must remember that the planning cf the lighting, and the part that light is to play in benefiting his sales, begins with the work of the electrical contractor, and with the placing of the outlets. 62 PART IV INDUSTRIAL LIGHTING Requirements of Good Industrial Illumination The requirements which must be met in the choice of re- flecting equipment and in the design of a satisfactory lighting installation for industrial plants are : 1. A steady light of sufficient intensity on all working- surfaces whether in horizontal, vertical, or oblique planes; 2. A comparable intensity of light on adjacent areas and on the walls ; 3. Light of a color and spectral character suited to the purpose for which is is employed; 4. Freedom from glare and from glaring reflections ; 5. Light so directed and diffused as to avoid objection- able shadows or contrasts of intensity; 6. A system which is simple, reliable, easy of main- tenance, and reasonable in initial and operating cost. Complete satisfaction cannot be expected from an installa- tion in which any one of these requirements has been neglected. Thousands of manufacturers have taken advantage of the abund- ance of light obtained from the high-power Mazda C lamps to duplicate daylight conditions in their plants, but others, either through carelessness or ignorance, have given no thought to the choice of proper reflecting equipment and installation. Naturally, such practice is not only wasteful of light, but the glare from the unshielded lamp filaments detracts in large measure from the effectiveness of the system and, in fact, may prove to be a positive menace to the safety and eyesight of the employees. Light on the Work Today, work of many kinds, including the most intricate operations and those requiring the utmost precision, must be carried on throughout the twenty-four hours. If artificial light :ould be had for the asking, no plant would be content with a lower standard of illumination by ni^ht than by day. Table i summarizes the minimum values of daylight that operators in typical factor : es consider sufficient. Each figure p-iven is the mean of a number of observations and the measurements extended over both clear and cloudy days. The aim was to secure data which represented good aver- 63 Table No. i Intensities of Daylight Illumination in Foot-Candles Values obtaining when daylight was deemed just sufficient for processes carried on. Factory Product Grade of Work Fint Medium Rough Engine lathes venETffM. x 10 6 15 7 2 15 3 0-5 9 Automatic engine lathes 1 4 2 30 1 2 2 30 1 1 15 Machine forgings 6 2 15 5 1 10 Special machinery 1 4 20 7 3 15 Lamps 10 5-16 9 11 15 Vacuum cleaners 17 7 25 1 1 3 20 Automobiles 5 2 11 5 2-8 5 3 11 Automobiles * 1 6 12 3 1 3 5 4 5 Storage batteries 5 16 3 0-5 5 Machine tools and patterns 6 2 16 9 3 35 Sheet iron equipment 1 1 20 5 1 12 8 2 15 Machine gears 7 3-16 8 5 18 5 1-15 Hardware 1 120 1 1 20 4 0-5 12 Printing machinery 5 1 15 3 0-5 5 Sewing machines 4 1 8 2 Cloth bags 5 3 10 7 3 10 Clothing 1 1020 4 7 15 Furniture 5 3 20 5 0-5 12 Average 1 4 18 7 3 1 5* 1 -5 - 10 *Saw tooth roof. age working conditions ; and factory processes were divided roughly into three groups in accordance with the relative nec- essity for accurate vision. It will be noted that in general the operations requiring closest attention were ordinarily best lighted, for wherever possible such machines are located near the windows. Just below the data on horizontal illumination there are given in each case the results of readings taken in two vertical planes, toward and away from the windows. Obviously, the minimum intensity of either daylight or arti- ficial light to be supplied is that which w*ill permit comfortable vision, conserve eyesight, and eliminate accident hazard. Many states, through their Industrial Commissions, are beginning to require the employer to make such minimum provision. In the States Codes, intensities for various classes of operations are spe- cified, depending on the nature and fineness of the detail to be 64 observed, the closeness of application required, and the reflection factor of the working surfaces. These intensities are designed to protect the operative who must work for long hours under these conditions day after day. However, these governmental requirements are not such as to ?ssure the most economical production, a factor of vital interest to the manufacturer, and to obtain which considerably higher in- tensity values are found necessary. It is difficult to recommend the exact intensity required in a given plant from the economic Fig. i Successful Application of Properly Directed and Diffused General Lighting to Interiors of this Nature is Gradually Eliminating the Drop Cord System standpoint. This figure necessarily depends upon numerous factors such as the cost of producing light, the number and wages of the employees, and the value of their output, all of which vary widely in different establishments. For good vision, the color and fineness of the materials worked upon are important considerations in determining the amount of light which should be supplied. An object is seen by the light which it reflects rather than by the light falling on it; hence textile mills manufacturing dark colored fabrics require higher intensities than those mills which produce light colored goods. Manufacturing processes involving fine machine work c-r fine assembling require more light than industries where a comparatively low degree of accuracy suffices. The greater alertness and better morale of the workmen in brightly lighted surroundings are at once apparent in the greater production of the plant. WML PfiNGE OF DAYLIGHT INTENSITIES INOOOftS-4tSO WTIFICIAL INTENSITIES FOR Extra, fine Work 8to 60 fine Work 4tolZ Medium Work 3t*9 Rough Work 2U6 Passageways. Etc.. Indoors. Outdoor Work FOOT-CflNDLE INTENSITY 10 20 JO 40 50 10 20 JO CO Fig. 2 Artificial Lighting Intensities Compared with Interior Daylight Values There is a growing conviction that no one should be called upon to work continuously at any occupation under an intensity of less than one foot-candle regardless of how rough the opera- tion may be. Table 4, of Part II, Illumination Design Data, lists the present standards of intensity for different classes of work. There is no doubt that the use of higher values than are there listed will prove profitable in many cases. It is a notable fact that in those factories in which the most study has been devoted to lighting, the highest intensities have been adopted, based upon ihe experience that each increase has led to still more economical production. Tests by Wm. A. Durgin in four Chicago plants where accu- rate cost and production records could be kept, showed that with illumination of the order of 10 to 12 foot-candles, the production increased from 10 to 35 per cent at a cost for lighting of only 'Electrical World, March 1, 1919. Electrical Review, March 22, 1919. 66 i to 5.5 per cent of the pay roll. These shops were engaged in various metal machining and assembling operations and the pre- \ious lighting systems were, in one case, individual lamps on drop cords, and in the other three instances, general lighting sys- tems in which the illumination ranged from 2 to 4 foot-candles. In a consideration of the amount of light necessary for fac- tory illumination, the criterion must be the intensity on all work- ing surfaces, whether in horizontal, vertical, or oblique planes. At one time, consideration was largely confined to light on the horizontal ; yet most factory work involves the perception of ob- jects in their three dimensions, and the illumination of all sur- faces is important. Except in especially unfavorable locations, such as near the dark side wall of a room, any of the systems of lighting usually employed can be expected to provide an intensity of illumination on any vertical plane equal to about one-half of that measured in a horizontal plane at the same point. This fact should be kept in mind particularly in designing a lighting system to comply with the State Codes, which usually specify only the value to be pro- vided on the principal plane of the work, which may be vertical, horizontal, or oblique. The intensity values used in industrial lighting as compared with the usual range of daylight intensities existing in factory interiors are shown graphically in Fig. 2. Illumination of Surrounding Surfaces Moderate intensities of illumination in aisles and other spaces intermediate between the working surfaces, on the walls, etc., are necessary to safety, good vision, and a stimulating atmosphere. Light side walls are conducive to a cheerful impression of bright- ness throughout the room. Sources which direct considerable light to the vertical planes, and light wall colors, aid materially in accomplishing this. The eyes of the workman looking up from his well illumi- nated machine or bench are not adapted for vision at low inten- sities ; hence, if adjacent objects and aisles are only dimly lighted, he will be compelled either to grope about, losing time and risk- ing accident, or to wait until his eyes have become adapted to the low intensity. Glancing back at his work, he again loses time while the pupils of his eyes adjust themselves to the increased amount of light which reaches them. If long continued, this 67 condition leads to fatigue, as well as to interference with vision, and to accidents. The general illumination of all intermediate and surrounding areas should be sufficient to allow no marked contrast with the brightness of the working surfaces. It is considerations such as these that have led to the almost universal adoption of the general or overhead system of lighting in modern industrial plants ; they also constitute strong argu- ments for the use of reflecting equipments which direct a part of the light toward the side walls and ceiling. Color Quality of Light As daylight intensities represent the standards which are to be sought in the artificial lighting of industrial plants, so does the color of daylight constitute the standard which should be ap- proached in artificial illumination. Through centuries of use the human eye has adapted itself to function best under a color of light found within the range over which natural light varies, and light within this range will also be found most pleasing and stim- ulating. Color discrimination forms one of the most important aids to vision. It defines outlines and edges and serves to identify ob- jects which may be similar in other respects, such as form, tex- ture, and reflection factor. The ideal illuminant therefore emits rays of all colors. While the exact proportions are not the same, still, all of the colors in daylight are contained in the light emitted by MAZDA C lamps, and objects retain their natural appearance when viewed under this light. The MAZDA daylight lamp with its specially selected blue-green glass bulb gives a light which is a further step toward daylight color and extremely valuable in the manufacturing processes requiring closer color identification cr better revelation of detail through color contrasts. For dye making and color matching, where extreme accuracy is required, several equipments w'ith special absorbing screens are available which duplicate the standard north-sky light with exactness. Under certain conditions, on the other hand, as in a foundry, the criterion for the choice of an illuminant is the penetrating power of the light. The appearance of the sun through smoke, haze, or fog evidences the fact that the shorter wave lengths, or 'he rays near the blue end of the spectrum, are absorbed or dis- persed while the longer w r ave lengths pass through. Hence, under such conditions, light in which red and yellow rays pre- 68 dominate is the most effective, and a clear-bulb MAZDA C lamp will give better service than a MAZDA daylight lamp. Glare Glare has been characterized as light out of place. It has been more fully denned as brightness within the field of vision of such a character as to cause discomfort, annoyance, interference with vision, or eye fatigue. Either definition establishes the fact that glare is undesirable. Fig. 3 An Installation of Mirrored-Glass Reflectors in a Foundry The degree to which glare is experienced depends upon six principal factors : i Total candlepower emitted by the source in the direction of the eye ; 2 Distance from the source to the eye; 3 Intrinsic brilliancy of the source; 4 Contrast in brightness between the light source and the working surfaces and surroundings; 5 Proximity of the light source to the line of vision ; 6 Length of time during which the source of glare is present within the field of vision. 69 It is a matter of common experience that of two sources of equal candlepower, that wihich has the greater intrinsic brilliancy or candlepower per square inch is the source of greater discom- fort. Too frequently, however, the consideration of glare is as- sumed to be entirely a question of intrinsic brilliancy. Of greater importance than this is the question of total light flux entering the eye. A lo-inch opal globe equipped with a 5OO-watt MAZDA C lamp hung approximately 10 feet above the floor and 10 feet from the observer, will prove fully as glaring as a bare ^5-watt MAZDA C lamp in the same location. Although the in- trinsic brilliancy of the opal globe unit is only two or three times that of a candle, its total candlepower hence the quantity of light which reaches the eye at this close range is so excessive that its effect is just as bad as that of the filament of the lower candlepower MAZDA C lamp which has an intrinsic brilliancy 400 times as great as that of the globe. On the other hand, the same 500-watt unit at twice the mounting height might be en- tirely unobjectionable because of the greatly reduced quantity of light which would then reach the eye. Contrast also is an important factor in causing glare. An un- shielded MAZDA lamp hung over a bench near a window causes no glare when viewed against the background of sky by day, yet the same source contrasting sharply in brightness with its back- ground at night will be the cause of extreme discomfort, accen- tuated by reason of the fact that it is close to the line of vision. The afternoon sun has only a fraction of its noonday brightness ; nevertheless, on account of its proximity to the horizon, it is much more likely to be glaring. Some sources which are not immediately recognized as glar- ing may cause fatigue when within the field of vision for a con- siderable period of time. The effect of looking out of a window for a moment is usually not at all unpleasant. But working all day at a desk facing the same window would be decidedly tiring. Specular Reflection Wherever highly polished surfaces are present, the reflected images of a light source as seen in these surfaces are more likely to be a cause of discomfort than the lighting units themselves. Glare caused by specular reflection from working surfaces is par- ticularly trying- because of the necessity of directing the eyes toward those surfaces, and further, because the eyes are by na- 70 lure especially sensitive to light rays entering from below. In choosing lighting equipment, it must be borne in mind that, al- though a given reflector may afford adequate protection against direct glare from the lamp filament, it will not protect against glaring reflections unless the lamp is shielded in such a manner that the filament cannot be seen when the unit is viewed from directly beneath. In many industrial operations including the inspection of finished surfaces, a moderate degree of specular re- flection or sheen will be found essential. Fig. 4 Freedom from Drop Cords is Essential where Motors are Moving Along in Progressive Assembly Shadows Differences in brightness of surfaces, that is, light and shadow, are essential in observing objects in their three dimen- sions. Without such differences, except as variations in color are present, no outlines, edges, or contours would be defined; one could not tell whether an object were rectangular or circular in cross section, whether the faces were flat, convex, or concave. On the other hand, in the factory it is usually necessary to work on surfaces in many planes ; hence, while dense, sharp shadows would define edges and outlines most distinctly, they might also be so dark as to interfere with work in the shaded areas. From successful trials of indirect lighting in offices, some fac- tory managers have drawn the conclusion that the indirect sys- tern is ideal for all locations, and that it is simply the matter of operating cost and maintenance which has prevented the univers- al application of this system. However, the distinction must be recognized that in offices close scrutiny is limited to plane sur- faces and that printed words and figures are rendered legible by differences in color and contrasts in brightness with the back- ground, and here specular reflection and shadows are of no aid to vision, but usually do harm. For satisfactory general illumination in industrial plants, there must be no shadows so dense as to make vision difficult where the direct light from one or two sources is cut off, nor so sharply defined as to cause confusion between a machine part and its shadow. In general, lighting should be so designed that shadows are present, but they should be soft and luminous. ***** * For a guide to the selection of lighting equipment and for the method to be followed in making illumination calculations, the reader is referred to Part II, Illumination Design Data. Operations of fine detail may be well lighted by an overhead system. Here the average of 10 Foot-candles is provided by 10' x 10' spacing of 150 and 200 Watt Mazda C Lamps in RLM Reflectors Table 2 Good Lighting for Factories Good Lighting requires three things: 1. Light of Suitable Quality. 2. Light of the Proper Direction. 3. Light in the Correct Amount. Good Lighting Suitable Quality r Absence of Glare. j Absence of Reflected Glare. [ Proper Color. T^. ,. ( Shadows Soft and Luminous. Proper Direction { Uniform Distri bution. [Lighting for Safety. Correct Amount \ Lighting for Economical Production. I Proper Cleaning of Units. Table 3 Bad Lighting for Factories Cause Effect Remedy Bare Lamps. Glare, eye strain, The modern efficient wasted light, harsh type of reflector shadows. such as RLM Standard dome. Miscellaneous local Glare, eye strain, General overhead sys- lights dangling on danger of accident, tem. drop cords. particularly about belting and moving machinery, short circuits, breakage. General System- "Spotty" lighting ; Proper relation be Units too far apart areas between tween mounting or too low. lamps receive very height of un'ts and little light; shad- spacing distance. ows are very black. Clear lamps where Reflected glare, eye Bow 1-E n a m e 1 e d polished surfaces strain. MAZDA C lamps, are present on ma- or equipment to terial or machinery. diffuse downward light from filament. Too little illumina- Time lost by work- Larger lamps in suit- tion. man, particularly a b 1 e reflectors on detail work ; eye spaced closer to- strain ; accidents ; gether if necessary. no incentive to keep place cleaned up. Sharp, black shadows. Accidents; time lost; RLM Standard dome eye strain. reflectors properly spaced. Bowl- enameled MAZDA. C lamps. Gloomy and cheerless Unpleasant contrast Liberal use of white appearance o f b e t we e n light paint accompanied room. sources and back- in some cases ground ; dispirited where location is workmen. suitable by use of glass reflectors. Dusty, dirty, or Loss of 40% to 60% Institute a regular broken equipment. of the light paid for. cleaning schedule. 73 LOCATION OF OUTLETS IN TYPICAL FACTORY INTERIORS The following illustrations show how direct lighting units may be advantageously located according to bays in the usual industrial interior. The reader is referred to Page 79 for a dis- cussion of bench lighting. Design No. Ja. Bays J2 x 16 ftl Design No. Jc. Bays J x 16 ftl Ceiling Height Not Less than 9 ft. Ceiling Height Not Less than Jg ft. (See also Design 11).) -L r . f. Ja '1 a I 1 I -t II " ( * 3 '^^ 6 L^ * Ii ) Wall A -^ II i I 1 i il \ D D U4 Q |] Q D || D( "1 II \ l| jl \ L D j D V | 1 i I n / 11 / a a a a n n / / n ll 'i a ll a L a [ ' "1 ~ ~ I 1 r -f-- n |f '' / ii *** a ,| D T | a , a |iy ^ ^_ K . _^&^ n .? i n y =]( U JL X SPECIFICATIONS 1 -^ 3J -3!~^-*^3E~^^ SPECIFICATIONS Location 4 Units per Bay as Shown (48 Location 2 and 1 Units per Bay as Shown Sq. Ft. per Outlet). (128 Sq. Ft. per Outlet). Mounting Height Good Practice, 8 # ft. Mounting Height Good Practice, 11 ft. above Floor; Preferably, somewhat above Floor. , Higher. Design No. Jd. Bays J2 ^ 16 ft ' Design No. p. Bays ft x IQ ft. Height-Not Less than 14 ft. Ceiling Height Not Less than 9 ft. (See also Design ja.) II | l| || II 1' " Wall A- /*' '-*' 3 . j, |l I l^-j! I 1 u_6' - 6 ' *p n- / ' | || || a a Ii a 4- a Fa a il a ll J II il " r Ii a a - - n a N 1 Ii a B| a 1 |i D a a ii i ! J 1 " J,/ i 1 j i { j ^y T T r l ii a a a a a | a I, n 1 1 n i n | a-i- a/ a a 'i a i a n ' 3 ^/ H ll II II y^ ii LX SPECIFICATIONS Location 4 and 2 Units per Bay as Shown (64 Sq. Ft. per Outlet). Mounting Height Good Practice, 8J4 ft. SPECIFICATIONS Location 1 Unit per Bay as Shown (192 Sq. Ft. per Outlet). above Floor; Higher. Preferably, somewhat Mounting Height Good Practice, 14 ft. above Floor. 74 Design No. a. Bays 12 x 20 ft< Ceiling Height Not Less than JQ ft. Design No. a. Bays lg x lg ft. Ceiling Height Not Less than 9 ft. 6 a !| a 4- ji a a l| a b II 'I' K 1 1| '' a ail Q-MID all a ail D I, a all a a a 'a il a Dll a SPECIFICATIONS Location 4 and 2 Units per Bay as Shown (80 Sq. Ft. per Outlet.) Mounting Height Good Practice, 10 ft. above Floor. Preferably, somewhat Higher. /*'n4- D a- '~ T1 r Tjpi ii D l| D P D i! <0|, 1 h D D!l D D l! D !' || i D IT" || D L). a n a a 1 i i D o ji a a ,| a D I = ^= -I _ i"z!b"- ^J SPECIFICATIONS Location 4 Units per Bay as Shown (64 Sq. Ft. per Outlet). Mounting Height Good Practice, 8^ ft. above Floor; Preferably, somewhat Higher. Design No. 2&- Ba ys 12 x 20 ftl Ceiling Height Not Less than 12 ft Design No. 3b. Bays lg x lg ft. Ceiling Height Not Less than ]_]_ ft. Where interior is not likely to be subdivided into smaller rooms, 4, 2 and 1 units per bay may be used in the same man- ner as in Design 6b. There will then be one outlet per 114 sq. ft. of floor area. =-=_-^-_^ J- =-^r ^= = J = =.-=.*. . ~T< ^~-~, SPECIFICATIONS Location 2 Units per Bay as Shown (120 Sq. Ft. per Outlet). Mounting Height Good Practice, 11 ft. above Floor. SPECIFICATIONS Location 2 Units per Bay, "Staggered," as Shown (128 Sq. Ft. per Outlet). Mounting Height Good Practice, 10 # ft. above Floor. 75 Design No. 30. Bays lg x Jg ft. Ceiling Height Not Less than ^4. ft. Caution: Any design showing less than 2 units per bay is not recommended for fine operations unless at least 2 rows of units are installed. Otherwise, light will not reach the work from a suf- ficient number of directions. Where there is much overhead belting or overhanging machinery to cast troublesome shadows, use Design 3b. SPECIFICATIONS Location 1 Unit per Bay as Shown (256 Sq. Ft. per Outlet). Mounting Height Good Practice, 14 ft. above Floor. Design No. ^a. Bays Jg x 20 ft> Ceiling Height Not Less than 1Q ft. SPECIFICATIONS Location 4 Units per Bay as Shown (80 Sq. Ft. peil Outlet). Mounting Height Good Practice, 10 ft. above Floor; Preferably, somewhat Higher. Design No. 4.0. Bays Jg x 20 ft * Ceiling Height Not Less than ft. Wall A SPECIFICATIONS Location 4 and 2 Units per Bay as Shown (107 Sq. Ft. per Outlet). Mounting Height Good Practice, 10^ ft. above Floor. Design No. 40. Bays Jg x 20 ft - Ceiling Height Not Less than \ ft. .3* VlallA -*H^H ?H fi D !! iii 1 f i h LailjJ- *T a "N a i| D-L' t r . - L D 1 a T a p D ji a i SPECIFICATIONS Location 2 and 1 Units per Bay as Shown (213 Sq. Ft. per Outlet). Mounting Height Good Practice, 14 ft. above Floor. Design No. 4<1. Bays \Q x 20 ft Ceiling Height Not Less than \^ ft. Caution: Any design showing less than 2 units per bay is not recommended for fine operations unless at least 2 rows of units are installed; otherwise, light will not reach the work from a sufficent number of directions. Where there is much overhead belting or overhanging machinery to cast troublesome shaidows, use Design 4c. SPECIFICATIONS Location 1 Unit per Bay as Shown (320 Sq. Ft. per Outlet). Mounting Height Good Practice, 16^ ft. above Floor. Design No. fta.. Bays 20 X 20 ft Ceiling Height Not Less than JQ ft Design No. fp>. Bays 20 x 20 ft> Ceiling Height Not Less than J2 ft - SPECIFICATIONS Location 4 and 2 Units per Bay as Shown (133 Sq. Ft. per Outlet). Mounting Height Good Practice, 12 ft. above Floor. Design No. gc. Bays 20 x 20 fti Ceiling Height Not Less than ^3 ft. Where nteror is not Ikely to be subdi vided into smaller rooms, 4, 2, and 1 units per bay may be used in the same manner as in Design 6b. There will then be one outlet per 178 sq. ft. of floor area. SPECIFICATIONS Location 4 Units per Bay as Shown (100 Sq. Ft. per Outlet). Mounting Height Good Practice, 10 ft. above Floor; Preferably, somewhat Higher. SPECIFICATIONS Location 2 Units per Bay, "Staggered," as Shown (200 Sq. Ft. per Outlet). Mounting Height Good Practice, 12 { / 2 ft. above Floor. 77 Design No. 5volts will automatically divide into H5-volts across each lamp circuit, and the lamps will operate at normal voltage. If the load becomes unbalanced, the side hav- ing the greater load will have less resistance, and the tendency will be for the voltage to divide unequally between the two cir- cuits, the voltage across the heavily loaded side becoming less than half the 23O-volts impressed across the two circuits. If this condition obtained, the lamps in the heavily loaded branch would receive less than normal current and wlould give less than their normal candle-power, whereas those in the lightly loaded side would receive more than normal current and would burn out at less than rated life. However, the balancer set takes care of this unbalancing. Under conditions of perfectly balanced load, the two machines composing the motor-generator set run idly as motors, taking only enough energy to offset the no-load losses. Fig. ii Simplified Wiring Diagram of Balancer Set Installation The instant that the load becomes unbalanced and the voltage between one main and the neutral starts to fall below the volt- age between the other main and the neutral, the tendency of the machine on the low voltage side is to slow down and run as a motor the same as before the unbalancing occurred. This is pre- vented, however, because of the mechanical connection between the two machines, and, since the generated voltage of the ma- chine on the low-voltage side is higher than the voltage im- pressed across its armature, it becomes, automatically, a gener- ator, and, within its capacity, holds the voltage of the heavily loaded circuit at normal or nearly so. The best regulation is se- cured by cross connecting the fields of the machines that is, by connecting the field for one armature across the circuits of the other armature and vice versa. 86 The current which the heavily loaded side carries in excess of that flowing through the lightly loaded side must be earned by the neutral. This neutral current divides at the motor-generator set, half of it, plus the current necessary to offset the losses ot the generator, flowing through the motor and the remainder flow- ing through the generator. If it is considered advisable to pro- tect the balancer against possible overload, a circuit breaker may be arranged to open both sides of the circuit between the bal- ancer and the source of supply or to open all three circuits be- tween the balancer and the lamp load; the precautions taken to guard against a break in the neutral of any 3-wire system should, of course, be applied. The action of a balancer coil for alternating-current circuts is very similar to that of the motor-generator set. The coil is sim- ply a 23O-volt auto-transformer with a mid-voltage tap. As long as the load is balanced, the coil floats on the line. When the load becomes unbalanced, the voltage tends to rise on one half of the coil and tends to drop on the other. Since both halves of the coil are on the same magnetic core, the voltages of the two halves, within the capacity of the coil, must be almost exactly equal. Hence, the voltages of the two lamp circuits are main- tained nearly equal. Since the current which the balancer must carry is determined by the degree of unbalancing, the capacity of the apparatus re- quired in any given case depends upon the magnitude of the lighting load and upon how nearly the conditions of installation will allow the circuits in the panel boxes to be made to balance. Obviously, the greater the number of properly connected cir- cuits, the smaller the chance for serious unbalancing to occur. In practice, the size of the balancer installed ranges from about TO per cent, of the total connected load to 20 or even 25 per cent., depending upon the size of the lighting load and upon how well the circuits may be divided. The capacity of the balancer set as used here is in terms of the current flowing in either machine multi- plied by the total impressed voltage of 220-250 volts, or the cur- rent flowing in the neutral multiplied by half the impressed volt- age. In addition to effecting maximum lighting economy and ob- taining superior service performance, the user of 110-125 volt lamps receives the benefits resulting from the use of a. more high- ly standardized product. Lamps of the 220-250 volt range are manufactured primarily to supply a small demand which does not justify the stocking of quantities of lamps to fill emergency re- quirements. Furthermore, improvements are less readily incor- porated because of the greater manufacturing difficulties present- ed by high-voltage conditions. 88 PART V LIGHTING OF OFFICE BUILDINGS AND DRAFTING ROOMS Introductory With too low an intensity of lighting the eye is soon fatigued, particularly when engaged in clerical work. With glaring light sources or glaring reflections from the work or surroundings, the efficiency is seriously impaired. With dancing or shifting shadows on the typewriter or ledger, eye strain is introduced. These effects are particularly serious in the clerical or steno- graphic office where a high percentage of women are employed, lor they are by nature particularly sensitive to such effects. Properly installed high intensity lighting in the office will increase production and reduce the number of absentees. A careful consideration of the subject shows past standards of intensity to be too low. An analysis of the standards recom- mended in typical textbooks and handbooks shows the average values set down as desirable to be between three and four foot- candles. It is possible, of course, to see to read or typewrite with less than one half foot-candle, but severe eye strain is introduced, and no one would think of insisting on prolonged work under such conditions. Where, then, is the economic or critical limit to in- tensity? One hesitates to say, and can merely report that the most progressive firms are using, and the leading specialists are recommending, from 10 to 15 foot-candles for general clerical work. What the standard will be a decade from now cannot be accurately foretold. One often hears the criticism that a certain place is over- lighted, and a much quoted report of some medical men who in- vestigated office lighting conditions in lower New York City, characterized the majority of them as "over-lighted." A sub- sequent casual investigation revealed this same general group of buildings to be even below the standards then prevailing for good office lighting. Glare is the element of lighting which causes the layman to refer to a place as over-lighted. These offices were in general glaringly lighted. Glare is the element we must guard against if the advantages of higher levels of illumination are to be realized. 89 Method of Lighting A few years ago each desk had a portable lamp directly above it and a few overhead units. This is what is termed a combina- tion of local and general illumination. It was a necessary con- dition, since the lamps were not efficient enough to warrant supplying a sufficiently high intensity throughout the entire Night View of Totally Indirect Lighting in a Small Private Office. In this installation each outlet supplies 3 75-watt MAZDA C lamps which are placed in inverted mirrored-glass reflectors concealed in a spun metal housing. The intensity of illumination is approximately 9 foot-candles room. An office with a multiplicity of drop lights is unsightly, the cost of wiring is high, and there is a heavy expense when wiring is changed as the position of the desks are shifted. The employees are likely to change the location of lamps by tying the wire to some stationary object, a practice which is objec- tionable from a standpoint of safety and forbidden by the wiring codes. Local lighting is objectionable as there is a great liability of glaring reflections from the desk surfaces and glazed paper; the clerk loses time shifting the light about, breakage of lamps is increased, and there is often marked contrast between the brightly lighted desk area and the rest of the room which does not make an efficient condition. Now, therefore, general illu- 00 initiation is practically standard. Overhead units alone are used lighting the whole room uniformly so placing the lamps that they are well out of the ordinary angle of view, equipping with diffusing glassware, and arranging them in such a manner that dense shadows are avoided. This scheme also permits the use of larger lamps, which, as a general thing, are more efficient than the smaller sizes. Since fewer outlets are required the cost of wiring is reduced. A great deal of careful investigation nas proved, without doubt, that general illumination is a real economy, all things considered, in comparison with local lighting. Comparison of Systems of Lighting Direct lighting with efficient reflectors is unquestionably the most economical, as far as current consumption is concerned, of the three methods, for with it the color of walls and ceilings have less effect on the resultant illumination. Direct lighting, if im- Semi-Indirect Lighting in Small Office properly arranged, may produce glare either from the light sources themselves or by reflections from the objects lighted, or it may distribute the light unevenly and as a result produce dense shadows. It is not generally as decorative as the other methods. Nevertheless, thousands of satisfactory installations of good direct office lighting are to be seen, employing translu- 91 cent glassware rather than opaque reflectors, thus avoiding the undesirable condition of a dark ceiling and the gloomy appear- ance of the room. Many forms of semi-enclosing glassware of the direct type are giving very satisfactory service. Totally indirect lighting is probably the most "fool-proof" from the standpoint of a glaring installation. The light is usually Semi-indirect Installation in Small Office evenly distributed and comfortable. Objections have been raised that there is a total absence of shadow, making the room appear flat. If the system is properly designed, however, this is not true. Semi-indirect lighting is an intermediate practice; it is more efficient than totally indirect and much better for the eye than the average direct lighting system. Semi-indirect lighting is net glaring if the proper unit is chosen; it can be made very deco- rative, the light is quite evenly distributed, and such shadows as are produced are very soft and do not become annoying. The fact that the place where the light originates is readily discein- :ble, has a psychological effect on the average individual and makes many people feel more at ease under semi-indirect light- ing than under totally indirect. 92 A semi-indirect unit, first, should be of quite dense glass; in other words, transmit but a small portion of the light, if the best conditions for the eye are to be obtained. If light density glass is used, the bowl becomes very bright and the system loses many of its advantages, dropping back to the direct lighting class where a number of fairly bright objects are in the field of vision. Second, the fixture or hanger used should be of such a length and the socket in the proper relative position to the bowl that the light is directed in such a maner as to illuminate the ceiling evenly. Many cases can be noted where the lamp is placed too low in the dish, concentrating the emitted light in a fairly narrow ?ngle resulting in a ring or circle of very bright illumination on the ceiling directly above the unit with the spaces between units Common Sense Office Lighting of a Modern Type. ISO-watt clear MAZDA C lamps are used on loft, centers, 4 outlets per bay. The resultant illumination is slightly over 9 foot-candles comparatively dark. At other times to get rid of this effect, the lamp is raised so high that from some parts of the room the filament becomes visible, introducing glare. On the introduc- tion of the Mazda C lamp with its rather concentrated filament, this feature became of more importance than formerly. 93 Third, the glass used should be smooth inside and, preferably, outside, as roughed glass collects dirt very readily and is difficult lo clean. Needless to say, all lighting fixtures should be regu- larly and carefully cleaned to keep the illuminating efficiency at a maximum. Fourth, the means of suspension of the bowl should be such that there is absolutely no danger of the glassware falling and it is desirable to have some convenient means of cleaning. The primary purpose of the fixture is to support the lamp and glassware and in most commercial installations should be as simple as possible, of plain, well finished metal. In a decorative interior, such as a director's office, the ornateness of the fixture is of more importance and its artistic value should be given due consideration. Fifth, in the commercial office the decorations of the glass- ware, if any, should be very simple, for any appearance of ex- cessive ornateness would be out of keeping wjith the character of the room. Deep crevices in the glass, although they may be decorative, are objectionable from the standpoint of dust accumulation. With indirect or semi-indirect systems it is very essential that the ceiling be light in color, white or slightly cream, to se- cure the maximum efficiency of reflection. Spacing of Outlets In practice a rough general rule, "never space outlets much further apart than the ceiling height," works out quite satis- factorily. In planning the location of outlets, it is desirable to space these symmetrically with regard to the bays or columns. The number of outlets per bay will, as stated above, depend on the ceiling height. Standard construction is tending toward 2O-foot bays in office buildings and for the ordinary heights of ceiling 4 outlets per bay are to be preferred. If the bays run larger than this it is often advisable to increase the number of outlets to 6, as future demands may necessitate the dividing of the large space into two or more small offi'ces. The 6 outlets per bay ar- rangement often meets these conditions without necessitating any additional wiring. In some cases additional outlets are pro- vided, but not fitted with fixtures (the outlet box rnerely being covered with a neat cap) to make provisions for the future and 94 avoid the necessity of opening the ceiling for rewiring. In cases where an unsymmetrical arrangement of outlets is necessary, they should be located relatively nearer the windows than the inside wall for the predominating light will then come from the same direction as daylight. In wiring large offices lamps should be controlled in rows parallel to the windows rather than in groups perpendicular to the windows. In this manner the center of a wide room which has the first demands for artificial light, can be turned on be- "ore light is required nearer the window. A High Intensity of Illumination if Provided in this Room by 300-watt Clear MAZDA C Lamps in Deep Bowl, Dense Opal, Inverted Reflectors. This type of illumination gives diffusion and eliminates dense shadows It is very rarely that an office can be lighted satisfactorily by one outlet, and even a small clerical office should have from 2 to 4 outlets, depending on its size. Wattage Required Good practice in office lighting where equipment employing clear bulb lamps is used calls for from \y 2 to 3 watts per square foot depending upon the effectiveness of the equipment em- ployed, the size and proportions of the office, the color of the ceiling and walls, etc. Equipments of the enclosing light-direct- ing type in either opal or prismatic glass, the semi-enclosing 95 type, and the semi and totally indirect type, are adapted to the use of either clear or daylight lamps. The use of daylight lamps is preferred by many because of the fact that the artificial light then blends with daylight and the transition from one to the other is made less noticeable. Where daylight lamps are used, about 50 per cent, more wattage is required for the same ilumina- tion, than is required where clear-bulb lamps are employed. In small rooms, since a greater proportion of the light striken the walls, a smaller proportion of the illumination will be ef- fective than in a large room with the same size lamps and same equipment. For private offices, it is often very satisfactory to provide a relatively low intensity of general illumination by some deco- rative central unit and use a localized light of satisfactory dc- sign for the desk. This should be located in such a manner ?.s to prevent glaring, annoying reflections. In any office where glass tops are used on the desks, particular attention must be paid to the type of lighting fixtures to avoid reflections. Drafting Rooms Although the lighting requirements of the drafting room are somewhat exacting, they may be readily met if due care be taken in the selection and location of lighting units. The ideal con- dition is an even distribution of well diffused light of a high intensity. Shadows must be minimized as they make it difficult to follow the fine lines when one is working close to the T square or triangle. A high intensity of illumination is necessary. Five foot- candles is the minimum and should be supplied only for rough work. For the most exacting work, such as tracing from blue prints, from 10 to 20 foot-candles will be required. The discussion given under office lighting applies to the drafting room. The requirements are even more exacting as the work is of a higher grade and must be accurate. Semi-indirect systems, where dense glass is employed, or totally indirect sys- tems, are probably the best suited, using from 1.5 to 3.5 watts per square foot. Direct general illumination of a high intensity using rather close-spaced semi-enclosing units is also used, where the ceilings are so dark as to preclude the use of indirect systems, and found satisfactory. The units should be located with reference to the 96 drawing tables and so arranged that the maximum light will come from the proper direction. Lamps must be hung well out of the angle of vision and every effort made to avoid glare. In both the direct and semi-indirect systems of illumination due note must be taken of the usual arrangement of boards relative to the windows, locating the lamps so that, as far as possible, the direction of predominant light is the same as that of daylight. A system which is quite frequently found is the use of a dif- fused general illumination (i to 2 foot-candles) supplemented Lighting of the Drafting Room by a local lamp for each drawing board. This unit may be of several varieties, fixed or movable, attached to the wall or to the drawing board, opaque or diffusing reflector, and various sizes of lamps; but in any case it is open to the usual objec- tions of local lamps, namely, liability of glaring reflections, loss of time in shifting the lamps, and relatively high maintenance cost. Tracing may often be satisfactorily accomplished by having the top of the tracing table made of etched glass, and lamps with suitable reflectors placed below the glass, illuminating the work from beneath rather than from above, PART VI SCHOOL LIGHTING Dr. Wm. M. Howe of the .New York State Department ot Education, states : "I believe that, in time, any school service mat does not prevent most of these ocular defects, with which we are meeting so often, will be considered inefficient and dere- lict in its duty to school children. There is something intrinsic- ally wrong in any educational system that permits from eight to fifteen per cent of our children to acquire defective vision within the few years of their school lives. Few children, as you know, are born with defective eyes." Proper lighting of the school house should not be considered an expense but an economy. If, due to defective vision, a pupil is forced to spend one extra year at school, the cost of teaching this one student for a longer period than normally, will much more than offset any of the expenditures necessary for proper lighting. Statistics reveal that these cases are legion. Illumination Values It is self-evident that the proper amount of light must be supplied for any kind of work. The correct foot-candles are nec- essary in order that everything which is to be seen may be eeen clearly and without fatigue. No matter what system is used, unless enough light actually reaches the desks, then the lighting system is inadequate. The following table indicates the minimum intensity of illu- mination it is desirable to provide in the school house. Classroom 5 10 foot-candles on desks Study Room 5 10 foot-candles on desks Office 5 10 foot-candles on desks Cloak Room i 3 foot-candles on floor Corridor 2 4 foot-candles on floor Laboratory 6 12 foot-candles on tables Auditorium 4 8 foot-candles on floor Drawing 10 20 foot-candles on tables While such values as given above will produce satisfactory results, the higher, rather than the lower intensities are recom- mended. With the higher intensities, an increased degree of perception is obtained. If increased production in industrial plants and offices can be profitably brought about by high level lighting, why should not increased speed and accuracy of ac- complishment on the part of the pupils likewise be worth while? 98 As an unfortunate result of our ecomonic system, students are usually compelled to work under less light than is provided in industry for similar operations. In reality, more light is needed because the pupil in the process of learning has to give rloser visual attention than a workman to whom a process be- comes more or less automatic. Diffusion The harmful effects of glare cannot be over emphasized. The jikelihood of glare from light sources is becoming greater and greater with the development of higher efficiency lamps with their increased intrinsic brightnesses. We therefore always reduce the brilliancy of the light by means of diffusing globes, shades or reflectors which either ef- fectively enlarge the light sources or actually hide them from Diffusion also softens the shadows so that severe contrasts are less likely to occur. It is not desirable, however, to go to such an extreme diffusion that we entirely eliminate shadows, for they are very essential to show the contour or shape of ob- jects. Over-diffusion or flat illumination is trying to the eyes and unpleasant. Not only must we take care of the light sources themselves in providing diffusion, but the walls and objects in the room must be given attention as well. Dull rather than polished sur- faces are desirable here, and even a depolished or waxed 'finish is more desirable than varnished or highly polished surfaces on the desk and other furniture, as the latter produce mirrorlike effects in reflecting the light sources. In this connection, attention should also be given to the desirability of mat rather than glossy finished paper for paper with a glossy finish likewise reflects light in an annoying manner. GENERAL CONSIDERATIONS The Classroom In most interiors we space outlets symmetrically throughout the room, but with the schoolroom, as with the machine shop, the shadow effect is very important, so we have the maximum light coming slightly forward and from the left to diminish the head and hand shadow's ; as far as possible the direction of day- light is imitated, sometimes much improved. 99 To accomplish this we arrange outlets as shown in Fig. I, "favoring the window side." More outlets are required for direct lighting than for the in- direct systems, in order that multi-directional light may be pro- vided. It is always desirable to hang units as high as possible to keep them out of the field of view. No lighting units should come below a line extended from 1 the eye of a student in the rear seat to a point two feet above the blackboard. ;t *o _ e'-o* .[. '? ic'-o" . -4_ s'-o"-. ff"^ 4-4 YO* n* Fig. WINDOW 9IOC Of ROOM 3Z'-0" Typical Arrangement of Outlets for the Average Size School Room (24 x 32 ft). The Size of Lamp Specified Represents Good Practice Fulfilling the Intensity Requirements Set Forth in the Text. A Four 2OO-Watt Clear MAZDA C Lamps in Dense Glass Semi-Indirect Units, Totally Indirect Equipment or En- closing Diffusing Globes. B Six loo-Watt Bowl Enam- eled MAZDA C Lamps in Etched Prismatic or Dense Opal Deep Bowl Direct Lighting Reflectors Blackboards There is a likelihood of glaring reflections from blackboards and they should, therefore, always have mat rather than pol- ished surfaces. It is sometimes possible to get rid of this re- flection by tilting the boards slightly. Blackboards on which rolored chalks will be used and those that are more than twenty feet away from the pupil should be especially lighted to an intensity approximately 60 per cent higher than the intensity in the rest of the room. This can be accomplished by the use nf properly screened and judiciously placed local units similar to the systems commonly used on outdoor signs and billboards. For clear vision, blackboards should not be located between windows. Comparison of Various Lighting Systems Direct, semi-indirect, and totally indirect systems are all 100 employed for school lighting. Each has certain advantages and disadvantages which are outlined below. A number of factors must be taken into consideration which may be briefly stated as below : Quality of illumination produced. Convenience of maintenance. Appearance of the installation. Efficiency of the system. Ability to provide the desired intensity. Cost of installation. Certain systems may appear to be most desirable from the- oretical considerations, but may not work out well in practice. Obviously, the type of lighting unit to select is the one which will give a desirable quality of illumination in as efficient a man- ner as possible, over a long period. The proper maintenance of a lighting system in any class cf service is of very great importance. Even greater emphasis must be laid on this question in the school, for supervision is at best meager and periods between cleaning are of consider- able length. These conditions should not exist but neverthe- less, we must recognize that such is the case and take this into consideration when planning the lighting. Totally indirect lighting produces a very high quality of illumination, but requires a relatively large wattage for a given intensity. With such a system, there is little possibility of glare and the light is very soft and comfortable to work under. Glar- ing reflections are at a minimum. The inverted bowls, however, tend to accumulate considerable dirt and unless cleaned fre- quently the light output is materially reduced. Semi-indirect lighting is an intermediate step, most of the light from the lamps being directed to the ceiling, with a slight amount transmitted through the glassware. It is slightly more efficient than totally indirect lighting, the resultant illumina- tion is well diffused, and such shadows as are produced are very soft and do not cause annoyance. The best forms of semi- indirect units for school work employ dense glass or some other means of reducing the brightness of the lighting unit. Ther* have recently appeared on the market, a number of totally enclosing, semi-indirect units which are relatively easy to clean and therefore offer special advantages. 101 In many of the older installations, open bottom, direct light- ing units are used. Such a system is obviously efficient from the standpoint of light utilization, but the diffusion is not of the highest quality, shadows and contrast are likely to be rather se- vere, and direct and reflected glare become serious, particularly if ( lear bulb lamps are employed. The use of this form of lighting is only advisable where costs must be kept at a minimum and Class Room Lighting where secondary consideration is given to the quality of illumi- i.ation. Where direct lighting is deemed advisable, dense opal or etched prismatic reflectors should be used. These transmit but a small portion of the light, and they, therefore, are not very bright. The diffusing bulb or bowl enameled Mazda C lamp should always be employed with open reflectors in preference to the clear lamp, as these finishes produce better diffusion, reduce reflected glare and soften 'shadows. The flat type reflectors should never be used in a schoolroom, lor it is almost Impossible to conceal the filament from view when using this style of shade. Opaque reflectors are, of course, gen- erally unsuited, as the ceiling would be very dark when these are used. IO2 In view of the above analysis, the enclosing, diffusing, direct lighting luminaire seems to be, at the present state of the art, the most generally applicable equipment for classroom lighting. ]f the proper type is chosen, a well diffused illumination, quite free from direct or reflected glare, is produced. Although the major portion of the light is directed downward, a considerable amount is transmitted upward, thus giving a cheerful appearance to the room and a character of illumination closely akin to that produced by semi-indirect units. It is apparent that such equip- ment does not depreciate as rapidly with the accumulation of dirt oS do other fixtures producing the same general quality of illu- mination. This should not be taken to mean that cleaning can be neglected, for it is always of prime importance. A typical specification for a suitable school lighting unit of ihe diffusing enclosing type, might be drawn up as follows: Class Room Lighting The glassware shall be of thin blown- opal or cased glass giv- ing good diffusion with low absorption. It shall be of such a size that the brightness, with recom- mended size of lamp, is not uncomfortable even when the unit is viewed for long periods of time. It shall be of such a shape that a horizontal section is greater than a vertical section. 103 The supporting holder shall be sufficiently strong and of such a type as to preclude any possibility of the glassware falling. The method of support shall be such that the globe can be icadily removed for cleaning. Similar specifications can be readily drafted for other forms of equipment. Corridor The lighting can be accomplished with relatively low watt- age lamps, on fairly wide spacings, provided diffusing glassware is employed. Uniform illumination is not necessarily essential. Smaller sizes of the same general type of equipment as used in the classroom can be utilized for the corridor. A row of outlets, symmetrically spaced along the center line of the ceiling, is gen- erally to be preferred, although sometimes the structure is such as to make ceiling outlets inadvisable. In these cases, brackets or wall fixtures must be employed. In general, 75 watt Mazda C lamps on 15 foot centers are adequate. With corridors over 8 feet wide, larger lamps are necessary. Laboratory The laboratory requires a relative high level of illumination m order that the progress of experiments may be carefully watched. The general layout suggested for the classroom is sat- isfactory for the laboratory. In the chemical department, how- ever, acid fumes will attack metal parts of ordinary fixtures and soon make them useless. For this reason porcelain enameled re- flectors and porcelain receptacles or sockets are well adapted. The RLM standard dome reflector with bowl enameled Mazda C lamp makes an excellent lighting device for such rooms. It is efficient, durable, inexpensive, and diffuses the light satisfactorily. Auxiliary Outlets The stereopticon and motion picture machines, as well as many electrical devices, are becoming important factors in our educational system. Every classroom should have an outlet to which these can be attached. The auditorium should have a well equipped motion picture booth for exhibiting standard films. The Mazda lamp for motion picture projection, with its economy and convenience of opera- tion, is a boon to the school. 104 PART VII RESIDENCE LIGHTING introduction When w;e realize the amount of time that we are dependent on artificial light, it is not surprising that devices which give proper illumination are receiving more and more attention. In the home, the useful and decorative phases of lighting must be com- bined, neither one being emphasized at the expense of the other. The decoration of a room may be absolutely spoiled or given the final touch of perfection by the lighting effect. Time, care, and considerable money are spent in establishing harmony of the furniture, hangings, and room finish, and avoiding any discord between the styles of furniture used. But of what use are these refinements in the matter of the decorations and furniture unless the lighting is such that these elements can be appreciated? It must be remembered that, as a general rule, it is during the hours when we need artificial illumination that we wish the house to appear at its best. Comfortable lighting makes pleasant sur- roundings enjoyable, but with poor illumination the carefully planned details of the room are ineffective. Fortunately, with the wide range of sizes of efficient lamps and the number of styles of standard lighting equipment available it is possible to have extremely effective lighting. The intensity of light desired for any particular purpose can be obtained with- out the objectionable feature mentioned above. No longer is it necessary to have only one light source in a room. The more reasonable way is to have a lighting system that can be readily adapted to the requirements of the people rather than making it necessary for them to adapt themselves to such lighting as happens to be available. As an example of this, let us consider the living room of an average home. In this room many recreations are enjoyed. Reading requires more light than talking, but music is more en- joyable in what is known as a "half light." If then, we are able to have the room softly lighted by decorative table lamps with the help of wall brackets, we can produce a general atmosphere of quiet contentment, the portable lamps furnishing illumination tor those reading beside them. For a comfortable game of bridge, it is a necessity that each player be able to see his cards easily, without holding his hand to avoid shadows. The most efficient 105 way to furnish equal light for all is to make use of a ceiling himinaire of the semi-indirect type, which will light the whole room to an even intensity. The advantages of variable lighting are readily appreciated, not only in the living room, but in all other rooms of the home. Systems of Lighting There are three general ways of lighting a room, i.e., by di- rect, totally indirect, or semi-indirect illumination. With lumi- naires of the first class, shades are used that send the dominating light directly down where it is to be used. The dining room dome, the shower fixtures, the pendant wall brackets, and the or- dinary table lamp, all are examples of this type of lighting. Just the opposite effect is obtained by using the indirect sys- tem because, in that, all the light is directed to the ceiling which in turn acts as a large reflector and distributes the light through- out the room. No dense shadows are created because the light, being reflected from such a large surface, is well diffused. This type of lighting can be obtained from special portable lamps, with inverted reflectors on the tops of bookcases or in wall urns, as well as from ceiling luminaires. Now, if the inverted bowl instead of being opaque allows i^ome of the light to be transmitted through it, still reflecting a greater portion to the ceiling, we have an example of semi-indi- rect lighting, another form of this being a translucent reflector on an upright wall bracket. Kitchen The unfortunate part of the ordinary kitchen luminaire is its inability to be adapted to much improvement. The combina- tion gas and electric stem luminaire places the lamp so low that the only thing it can do is to cast the shadow of the worker on the work. The designer of such a luminaire seems to have the mistaken idea that the light is wanted on the floor in the center of the room rather than on the stove or sink. Then, too, the glass- ware that is used is ineffective. There is really little that can be done to improve this luminaire save by the substitution of diffus- ing bulbs for clear lamps. If satisfactory lighting is desired, this luminaire should be replaced by one which carries the lamp close to the ceiling and is furnished with a glass reflector that will as- sist in distributing the light around the sides of the room. Of course, if the room is large, this ceiling- light will have to be aided in its efforts by wall brackets in the darker parts. The shades 106 used should be of dense opal glass with smooth, easily cleaned surfaces. For places of average dimensions, a 75-watt white Typical Luminaires for the Kitchen Which Will Provide Suitable Lighting if Properly Applied or a TOO- watt bowl enameled MAZDA C lamp in an 8-in. diameter reflector should be used in the ceiling unit, while 25-watt all irosted MAZDA B lamps in 6-in. reflectors will serve on the brack- et luminaires. Such a combination will do away with objec- tionable glaring reflections that a bare light source will give when bright pans are used. When the ceiling is painted a light color, a semi-direct system of lighting is effective. With this installation, only the ceiling Jnminaire is necessary and yet the shadows are reduced to a mini- mum. A loo- or I5o-watt clear MAZDA C lamp in such a lumi- naire will provide adequate intensity in the typical kitchen. A wall switch near the doorway is a mpst desirable feature, but its absence will not prevent the use of a luminaire hung out of reach, for chain pull sockets with a length of cord and lumi- nous indicator may be used to control the light. Whatever form of lighting is employed, it is highly important that convenience outlets for the iron, percolator, or fan be pro- vided. The position of the outlet to which the iron will be con- nected merits consideration' and should be such that the mini- mum of shadows is cast on the board both in the daytime and at night. 107 Another way to make the kitchen as comfortable and as easy to work in at night as it is in the daytime, is by the use of Mazda daylight lamps. The daylight quality of the light not only makes a cleaner looking kitchen, but, just because it is like daylight, stains are more readily visible and therefore the kitchen actually is cleaner. Butler's Pantry If the outlet is not already in place, it is preferable to have it installed directly over the sink. A direct lighting opal reflector, 5O-watt MAZDA lamp, close ceiling luminaire, with pull chain socket, may well be used here. When the outlet is already in the center of the room, this type of lighting is not advisable be- cuse of the shadows that will be cast by the worker on the sink. Under such conditions, semi-indirect lighting is preferable and a harp type holder may be used that suspends an opal glass re- flector under the lamp. A convenient outlet near the sink is desirable for attaching a small motor for polishing silver or other time-saving devices. Laundry and Work Bench As a usual practice, the washing machine is installed in the basement and artificial illumination will probably be necessary whenever the machine is used. High level illumination is a de- sirable factor here and MAZDA daylight lamps make it easier to detect stains on linen. The 100- or I5o-watt bowl enameled MAZDA C lamps in RLM Standard dome reflectors make an effi- cient luminaire giving the desirable quality of diffusion and dis- tribution. The type of direct luminaires suggested for the kit- chen is also applicable where the laundry is "finished off." The location of convenience outlets for the washing machine and ironer should be considered with respect to the position of the light source. For hand ironing, an outlet on a drop cord is preferable to one in the side wall or baseboard in giving greater latitude in the work. The lights for the cellar proper should be so distributed as to "iluminate the foot of the stairs, the furnace, coal bins, and cold pantries. If the ceiling is finished in a light color, flush or sur- face receptacles with diffusing bulb, low wattage lamps without reflectors will give a wide spread of light at a low cost of in- stallation. At least one of the cellar lights should be controlled from the 108 head of the stairs and it is desirable to have some sort of a pilot device to indicate whether or not the lamps are burning. Den or Sewing Room The lighting requirements of these two rooms are so similar that they can well be discussed together. For close Work, either m sewing or keeping records, a high intensity of illumination is necessary. For ordinary purposes, however, we do not want to have the whole room as light as this. A combination of lighting is desirable, a central diffusing luminaire to furnish general illu- mination of moderate intensity, and a portable luminaire for the close work. A Simple Means of Obtaining Semi-indirect Effects from a Direct Light ing Luminaire and the Efficient RLM Standard Dome Reflector for Lighting the Basement and Garage. The porcelain enamel resists attacks of moisture Living Room The living room is the scene of the social life of the house, and the lighting of such a room should receive special attention. It must be agreeable and bring out the especial points of the dec- orative scheme. It will not be a full success if it makes people look tired, old, or unattractive, by bringing out sharp facial shad- ows. Into this room novel effect may be introduced that vary the monotony of ordinary lighting. Small lamps burning inside translucent vases render them luminous and show beauties that would otherwise not be noticed. The possibilities in the way of special effects can be utilized only when an adequate number of convenience outlets are available. Ingenuity will soon indicate many expedients by means of which the little touches of color, 109 that aid so much in the appearance of the room, can be intro- duced at will. For general lighting, when only one outlet is available, a semi-indirect luminaire will more nearly meet the average re- quirements than any one type. A lamp of sufficient size can then ie used to furnish the necessary intensity and the light will be comfortable and devoid of glare, provided a proper design is chosen. A 100- or 150-watt Mazda C Lamp will usually provide a de- Adaptability is the Keynote of the Lighting Shown in This Room. ISO-watt MAZDA C lamps are used in inverted reflectors in the portables. 15-watt all frosted MAZDA lamps in the brackets are concealed by shields harmonizing with the wall coverings sirable intensity of illumination with semi-indirect luminaires in rooms of average dimensions. There are innumerable period styles of luminaires suitable for the living room. A few typical examples are indicated in the ac- companying sketches. In choosing luminaires of this nature, the cardinal points in regard to distribution of light, contrast, and direct glare must be kept in nuind. Very rarely is it feasible to use lamps without some sort of a shade or diffusing medium. With a suitable number of wall and convenience outlets it is" no good practice to light the living room without a central or ceiling luminaire, and, in this event, table and floor lamps may be used to advantage. The Styles of Portable Lamps Giving Good Results Are Innumerable. These are just a few suggestions All portable lamps should be chosen with particular thought given to the shades. It is always objectionable to be forced to look at a lamo and the shades must conceal the light sources from one sitting near them. The materials used should be dense enough that the filaments do not show through and as pointed out before, it is always desirable to use diffusing bulb lamps in any kind of direct luminaire. With skillful selection, a shade will become an integral part of the color scheme of the room in the evening, as it is during the day. Sometimes, however, a color is used that harmonizes well enough with the drapes and iurniture covering but when the shade is lighted, the effect is far from desirable. This danger is most likely to be present when green or blue color schemes are employed. The best solution for such a condition is to have the exterior layer of in particularly thin material, such as chiffon or georgette crepe and the lining a rather heavy rose, buff, or cream. The resultant light will be toned by the lining and ghastly effects eliminated. A wall switch is the most desirable for controlling the lights in the living room, and it is generally advisable to have the A Few Styles of Direct, Semi-Indirect and Totally Indirect Ceiling Luminaires Suitable for the Living Room Under Various Conditions Glass shades for candle fixtures are now available in very rich and decorative designs central outlet and wall brackets on separate circuits. Absence of a wall switch will not make it impossible to use semi-indirect illumination, for small switches can be neatly concealed in the canopy fitting and operated by a fine cord. The living room re- quires the maximum number of convenience outlets for at- taching the portable lamps, electric fan, phonograph motor and special decorative lighting effects. Various Means for Lighting the Living Room from the Sidewalls Dining Room This room has lighting requirements peculiar to itself; rarely This Night View of the Dining Room illustrates the Even Illumination and Absence of Shadows Characteristic of Semi-indirect Lighting is it used as anything but a place to eat. The interest therefore is primarily centered on the table and this interest may be increased by having the table lighted to a higher intensity then the rest of the room. 113 It is a matter of personal taste which way the dining room shall be lighted, whether by direct or indirect methods. The eld style dome, while often crude and inartistic, provided a most desirable distribution of light. The table was the brightest spot in the room;, yet enough light was transmitted through the glass to illuminate the corners of the room, preventing too great a contrast. There are several requirements which must be fulfilled where a dome is employed. It must be hung high enough that one can see the person on the opposite side of the table and yet not so high that the lamps are visible. This will place the bottom) of the dome about 56 inches above the floor. A dome can often be made more effective by using a small direct lighting reflector inside of the fabric or glass to send the light downward and conceal the lamp from view. A num- ber of styles of domes have recently appeared on the market much more artistic than those produced in the past, and hence more generally applicable to the home where harmony is sought. A 5O-watt White Mazda lamp will give the desirable intensity on the table top when a dome is employed although in in- dividual instances, higher or lower values are considered more pleasing. Some people prefer the room more uniformly illuminated and this can be accomplished by the use of the semi-indirect system. By choosing the proper density of glass, a suitable amount of light will be transmitted, the table receiving more light than the surroundings. For this system), 75-, 100-, and i5O-watt Mazda C lamps are applicable, depending on personal preferences as to intensity and on the color of surroundings. It is often possible to provide two circuits in a semi-indirect luminaire, one giving the low illumination for setting the table. Luminaires should not serve as sources of current for cook- ing devices. A convenience outlet should be installed under the edge of the table, and this in turn, attached to a floor plug. A baseboard convenience outlet near the buffet or serving table permits the percolator, toaster, or grill to be used without the unsightly collection of cords dangling from overhead, as is too commonly the case. Hall or Reception Room Every room in the house has a particular meaning and, as 114 the hall is the first one entered, a feeling of hospitality should prevail. Lighting can be of great assistance in attaining this end. There are two kinds of halls just as there are two varieties Some Well Designed Dining Room Units. It is of interest to note the tassel at the bottom of the semi-indirect bowl. This conceals half of an attachment plug for use with cooking devices. The wicker dome carries an opalescent reflector indicated by dotted lines of porches. One is merely a space between the front door and the rest of the house, the other is of the reception room type. In the first class a moderate intensity of illumination suffices and a 25-watt Mazda lamp in a suitable diffusing globe close to the ceiling will furnish enough light for removing one's "5 wraps. The upstairs hall has generally the same requirements and may be similarly lighted. The methods of lighting the living room are quite generally applicable to the hall of the reception type. Urn shaped en- closing globes ?re also harmonious with many interiors. The control for hall lighting is important. Three-way These Examples are Typical of the Variety of Luminaires that are Suitable for the Reception or Formal Hall switches are most desirable, one near the entrance doorway and the other at a convenient point in the second floor hall. The slight additional expense in installing these is more than offset by the security and comfort gained. Bedroom The general arrangement of lighting outlets in the bedroom will depend upon the placement of the furniture. In most 116 cases it is desirable to provide a low 1 intensity of general illu- mination from a central luminaire, preferably of the semi-indirect type, although frequently silk-shaded direct luminaires are suitable; from 40 to 75 watts are desirable in this unit. It should be controlled by a wall switch near the entrance doorway to avoid stumbling about in the dark in search of the key-socket. Dainty Decorative Luminaires Suitable for the Boudoir are Numerous. One should be chosen which blends with the color treatment of the room. Candle fixtures shaded with richly colored glass give good illumination together with pleasing color effect A higher intensity of illumination is required at the mirrors or dressing table and this can be obtained by wall brackets or pendant dresser lights harmonizing with the central unit as well as the rooml decoration. A pendant dresser light should be placed slightly in front of the person using the mirror. A con- 117 venience outlet near the bed makes it possible to attach a heat- ing pad, or portable lamp for reading in bed. Another near the dresser is useful for attaching an electric curling iron, heater or fan. The harmony of equipment in the boudoir is very important. Where the closet is in such a position that it does not re- ceive light from the room itself, a simple type of receptacle should be provided close to the ceiling with a low wattage, dif- fusing bulb Mazda lamp. A door switch for such a position is a convenience and an economy. The Day View of This Bedroom Gives a Good Idea of How Different Materials May be Used in the Lighting Equipment and the Results be Harmonious. The fact that all lamps are concealed from view is indicative of comfortable conditions Bathroom The mirror is the point of particular interest in this room and the lighting must be planned with this in mind.' The face must be well illuminated before it can be viewed in the mirror. Wall luminaires, one on each side, will provide satisfactory illumination for shaving. The I5~watt diffusing bulb Mazda lamps in either pendant or upright shades may be used. A iamp in a simple diffusing globe close to the ceiling may be used for general illumination where additional light is neces- sary. Care should be taken in locating the lighting outlets in 118 the bathroom in order that shadows of the occupant of the room will not be cast on the window. Convenience outlets are nec- essary for the electric heater, curling iron, hot water mug, or vibrator. Neatness and Simplicity are Expressed in Such Luminaires as These Applicable to the Bathroom, Closets and Passageways Respectively. Parchment, Silk, and Glass are Media for Directing and Diffusing the Light. Here they are Applied in Neat Dresser Luminaires Porch In order that the home may invite one's friends and repel intruders, the porch should be well illuminated. A porch often serves merely as an entrance, but may act as an outdoor living room. Of course in these two cases radically different lighting will be employed. In the first type, only a small amount of illumination is required for safety and to enable one to see the name plate, doorbell or button. A lo-watt Mazda lamp 119 will burn for a long period at a very low cost and serves ex- cellently on the porch in a weatherproof enclosed type globe, lantern fixture, or luminous house number. An outlet is also necessary at the rear porch or service entrance. In the large porch or sunroom, much novelty can be introduced. In- direct lum'inaires of metal or actual wickerwork lined with cretonne or tinted glassware are suitable in introducing a touch of color harmony. Artificial or natural flowers or vines can be effectively applied. Convenience outlets on the porch for attaching portable lamps or other devices should be of the The Indirect Light Sources in This Sunroom Are Inconspicuous by Day and Add to the Decoration When Lighted. 4O-watt lamps in metal reflectors are concealed by the artificial flowiers in the wire baskets weatherproof type and located in such positions that they will not collect moisture. Grounds While the subject of lighting the grounds is particularly of interest to those having suburban homes, there are still many parts of cities where the street lighting may be supplemented by a lamp at the entrance of the driveway. This light acts as a welcome to guests, as a means of protection, and also will contribute to the appearance of the property. The use of an ornamental standard that matches the architectural style of the 120 house, with an opalescent glass globe or lantern type luminaire, is good practice. A 5O-watt [Mazda lamp in this will enable the driver of an automobile to see the entrance clearly. When the driveway is of considerable length, it becomes necessary to place lights at least at sharp curves or particularly dark spots. The size of the lamps used will depend upon the surroundings but Mazda lamps ranging from 25 to 75 watts should fulfill all requirements. It is necessary that these lamps be used on standards that will raise them above the direct line of view of the driver. The glassware used should minimize glare in the driver's or pedestrian's eyes. The Luminaire for the Porch Need Not be of a Crude Afterthought Nature, but can be Distinctive at a Small Additional Cost Garage Electric light is a necessary adjunct to the garage in reduc- ing the fire hazard, promoting safety and making adjustments and repairs in a satisfactory manner. General illumination should be furnished by one or more overhead luminaires, de- pending on the size of the structure. Bowl enameled Mazda C lamps in steel reflectors, porcelain enameled, of the dome type, are desirable for this service. They should be controlled by a wall switch near the entrance. Several convenience outlets are also necessary with a number of re-enforced cords, Mazda mill type lamps and wire guards, as portable lights. In working on the engine and transmission, such equipment proves of value. 121 Wiring The standards for proper wiring from a protective basis are established by local underwriter's codes and ordinances. These must be adhered to. The choice between different systems is governed largely by economic considerations and need not be discussed here. Attention should be directed to the desirability of making the initial installation complete. A given amount of installation work can be done at much less expense when doing the original work than at a later date. The mistake is often made of omit- ting convenience outlets and wall switches in order to keep Layout of Outlets for a Typical Small House down the cost of wiring. This will certainly be regretted when one begins to appreciate that some of the real advantages cf electric service are lost. The statement can be made with a reasonable degree of cer- tainty that "one cannot have too many outlets." The errors in practice are all in the other direction. A satisfactory layout ior the average home would be such as pictured above. A feature which should be incorporated in each house wired in the future is the use of the Elexit or the standardized lu- minaire receptacle. This device makes it possible to "hang a fixture like a picture" and one can change bracket or ceiling iuminaires at will, without the often prohibitive delay and ex- 122 pense of calling in an electrician to make any connections. It will be as simple to move a fixture from one room to an- Q < N Q < a "8 i "2 1 g I 'S g I I il J - o < I ? I its It ll (O Si LAMPS Large 15'x20' . Q K f- 2 s l 03 i II" 1 ill IS s rpi ill Hli other as it now is to move a table lamp. A person living in a rented home need not be content with the lighting that hap- 123 pens to be installed but can use his owin distinctive, individual fixtures, just as he does his pictures, draperies, and furniture. The special wiring devices which add materially to the con- venience of the installation are almost innumerable. Among them might be mentioned : T;he switch handle or small indicator on a pull chain sockei provided wuth luminous material which glows in the dark, mak- ing it possible to locate the control readily. Switches with small lamps concealed in their mechanism which serve to indicate that the attic or cellar lights are burn- ing. Buzzing devices serve the same purpose. Switches which can be attached to the ceiling or concealed in a canopy where wall switches are missing and it is not deemed advisable to do any extensive wiring. Three-way switches for controlling the light front two points. Two or more circuit switches in one mechanism to produce various degrees of lighting by pushing or turning the button a certain number of times. Switches which operate automatically when a closet door is opened or closed. Master switches for lighting the whole house from the owner's bedside in case of emergency. Convenience receptacles which can be installed in the wall, baseboard, floor, or under a table. These should be of the standard type to take a plug with ^-inch parallel blades spaced J/2-inch apart so that all plugs are interchangeable. Bell ringing transformers which do away with maintaining batteries for this purpose. Toy transformers which can be used to provide a low volt- age circuit that can be safely used in the nursery for children's electric toys. Sockets to convert candlesticks so that they will serve as electric lamps. New devices of this nature are constantly being developed and the adaptability of electric service continually broadening in scope. 124 PART VIII CHURCH LIGHTING General Requirements No set rules can be laid down for designing church lighting as the structures vary widely in type and the artistic effect plays such an important part. In other words, this class of lighting cannot be standardized as that for the industrial plant, office, or store. In attempting to discuss the subject, one can only outline the conditions likely to be encountered and schemes which have proven satisfactory in service. The illuminating engineer must co-operate with the architect and bear out the latter's ideas with respect to the lighting effect to be attained, and specify such location of units, types of fix- ture and distributions of light as to meet these criteria. If care is taken in selecting and locating the lighting fixtures, these edifices can be very satisfactorily lighted, for they seldom have brilliant interior finishes to cause glaring reflections; the ceilings usually are high, thus permitting hanging the lamps out of ordinary view. Observation of actual installations reveals that, if our homes were as poorly lighted as many of our churches, it would soon have a serious effect on our vision. As We are in the church for only a few hours every week, the matter is not given suffi- cient thought. In the church, in contrast to the theatre, or assembly hall, the lights are turned on the entire time that the congregation is present, and particular attention must be paid to the arrange- ment of lighting units, concealing the lamps from view or equip- ping them with diffusing glassware. As pointed out, the lighting units should be in architectural conformity with the structure, yet utility of the lighting must be given consideration. By this is meant first, use every pre- caution to prevent eyestrain, which leads to drowsiness and at-