Electrical 
 Fire Hazards 
 
 The Insurance Institute 
 of Hartford, Inc. 
 
 1918 
 
PRACTICAL INSTRUCTION 
 
 ON 
 
 "Electrical Fire Hazards" 
 
 By 
 
 THOMAS HENRY DAY 
 
 of the 
 
 New England Insurance Exchange 
 Boston, Mass. 
 
 Given before 
 
 THE INSURANCE INSTITUTE OF HARTFORD, INC. 
 Season of 1917-18 
 
T- 
 
 COPYRIGHT, 1918 
 
 The Insurance Institute of Hartford, Inc. 
 Hartford, Conn. 
 
Electrical Fire Hazards 
 
 Part No. i. 
 
 INTRODUCTION. 
 
 Electricity in motion, lights lamps, drives motors, refines 
 metals, raises to a high temperature all sorts of electrical 
 heating devices, energizes the telephone, telegraph and electric 
 bell. From one outlet we may supply an incandescent lamp, 
 a flat-iron, a coffee percolator, a toaster, an electric fan, a 
 heating radiator, a sewing machine motor, a broiler, a hot- 
 water heater and a number of other devices. Thus, we may 
 from one simple fixture use electricity in motion for light, 
 heat or power. Electricity at rest, has few effects of practi- 
 cal value. So we are to study electricity only as it moves, 
 that is, flows and does work. 
 
 WHAT IS ELECTRICITY? 
 
 Electricity has been described as juice. Since Benjamin 
 Franklin brought it from the sky with a kite, no better, or 
 more scientific definition has been made. In a word, we 
 cannot tell you what electricity is. Our interests, as Fire 
 Prevention Engineers, are concerned only in the event of im- 
 perfect installations and the use of improper devices and ma- 
 terials which would constitute a fire hazard and the National 
 Electrical Code, the recognized standard of electrical installa- 
 tions in this country and in Canada, is confined to such ques- 
 tions as w r ill provide proper methods and materials that such 
 hazard may be minimized. We might say that the National 
 Electrical Code was for the purpose of using electricity in the 
 capacity of a servant. Used as such, it is safe. When, how- 
 ever, it is permitted to become a master, it not alone becomes 
 a hazard, but a menace, as well. 
 
 ISTORY. 
 
 Electricity is not an invention. Like steam, it is a dis- 
 covery. Its discovery was not much, when viewed in the 
 light of the world at its birth, some 600 B. C. ; merely a piece 
 
of amber rubbed against the clothing of the Greek Thales; 
 merely the gaining of a strange property of first attracting 
 and then repelling light objects brought near it. Dr. Gilbert, 
 a physician to Queen Elizabeth, may be considered as the 
 founder of the science, as he appears to have been the first 
 philosopher who repeated the observations of the ancients. 
 The experiments of Sir Isaac Newton, before the Royal 
 Society, in 1676, excited surprise and comment. Sir William 
 Watson succeeded in firing gunpowder by the electric spark 
 and established the theory of positive and negative electricity. 
 
 A high place in the history of electricity must be allotted 
 to the name of Benjamin Franklin. His researches did much 
 to extend our theoretical and practical knowledge of elec- 
 tricity. In 1827, Dr. G. S. Ohm rendered a great service to 
 the science of electricity by publishing his mathematical 
 theory of the galvanic current. In 1831, Faraday began with 
 the discovery of the induction of electric currents, that 
 brilliant series of experimental researches which has rendered 
 his name immortal. 
 
 To attempt to trace the history of the dynamo-electric 
 machine would more than fully occupy the time generally 
 assigned to a single lecture. Suffice it to say, that the first 
 machine of this type was invented by Faraday, who modestly 
 described it merely as "A New Electrical Machine." 
 
 Later came the successful solution of the divisibility of 
 the electric light by the invention of the incandescent lamp. 
 
 The invention of the dynamo rendered the extended com- 
 mercial application possible of another invention, the electric 
 motor, which has been successfully developed and placed into 
 actual use to an extent that appears almost incredible. It has 
 been recently stated by the Society of Electrical Development, 
 that electricity is being used in over 5,000 different ways. 
 
 PURPOSE OF 
 ELECTRICAL INSPECTION. 
 
 A fire prevention engineer, or an electrical inspector, 
 should not endeavor to ascertain if the installation will meet 
 the demands of its intended uses. The function of inspection 
 is single, not manifold. The one purpose should be to examine 
 the installation, whether it be for electric light, heat or power, 
 that weak points, if any, which might cause a fire or be dan- 
 gerous to life, may be pointed out and corrected. I do not 
 
think it would be wise for the fire prevention engineer, or 
 electrical inspector, to engage in the engineering problems of 
 the installation he may inspect, but he should be capable of 
 passing on plans and the execution of the work that life and 
 property may be safely guarded. 
 
 The wisdom in refraining from engaging in the electrical 
 engineering problems of the installation, may be seen in the 
 several methods for determining the size of conductors to be 
 used for alternating current motors, there being different con- 
 siderations for the varying types of motors, the uses, the 
 power factor, the voltage and the starting and running loads 
 of the motors being different in the several types and locali- 
 ties. The method, protection and execution of the installation 
 is what should concern the fire prevention engineer, or electri- 
 cal inspector. 
 
 IRES CAUSED BY 
 LECTRICITY. 
 
 Among the problems, subsidiary to the question of in- 
 stallation, is the relation of electricity to the fire hazard. Vir- 
 tually all the precautions for the maintenance of conditions of 
 safety may be found in the provisions for adequate conductiv- 
 ity and efficient insulation, as fires by electricity are only 
 caused by one or both of two general ways. 
 
 OVERHEATING. 
 
 FIRST: By the overheating of conductors, wires, 
 switches and other devices which may result in a fire to sur- 
 rounding inflammable material and objects. Overheated 
 wires will ignite the insulation and the flame will travel along 
 the conductor, igniting other inflammable objects in its path. 
 That this overheating may be avoided, we should examine 
 very closely the types and sizes of fuses used. The old 
 fashioned link fuses should never be permitted unless en- 
 closed in cabinets of proper construction, except on switch- 
 boards located in rooms of fire resisting construction. The 
 so-called fuse wire should not be permitted, under any cir- 
 cumstances, because of the absence of the copper terminals. 
 Fuses of any type should never be installed in locations where 
 there are flyings of ignitable material, dust or gases, as, even 
 with enclosed fuses, the gases formed by the fusing metal, 
 in the fuse, do tear apart the fuse casing and the arc, also the 
 
Courtesy of Commissioner James E. Cole, Wire Dept., Boston, Mass. 
 
 Group of cut-outs, parts of fixtures and sockets burned out. These 
 cut-outs were for the old fashioned link fuses and had mica covers which 
 made them extremely hazardous, because when the link fuses operated 
 the mica cover was broken and thus permitted the molten fuse metal to 
 be expelled from the cut-out. The use of this type of cut-out has not 
 been permitted for a number of years. 
 
molten metal will ignite combustible material and cause fire. 
 
 All conductors are heated by any current however small, 
 but if the conductor is overloaded, and over-fused, it may be- 
 come hot enough to ignite the insulation. Hence it is import- 
 ant that wires should be of sufficient capacity to carry the 
 load, and all conducting parts of electrical appliances must be 
 properly proportioned. Overheating of conductors and de- 
 vices is thus one of the ways in which electricity may cause 
 a fire. 
 
 Assuming, for purposes of illustration, that the con- 
 ductors of a circuit were properly proportioned and were 
 properly protected by fuses when they were installed. With- 
 out consideration of possibilities the number of lamps is in- 
 creased or a larger motor replaces the original motor. When 
 this increased load is thrown upon the conductors, the fuses 
 "blow" and open the circuit, just what they were designed to 
 do. Someone increases the size of the fuse, or worse yet, 
 substitutes a copper wire, a hair pin, strips of iron, brass or 
 lead, and I have even found ten cent pieces in the cut-outs. 
 The lights burn brightly, or the motor runs satisfactorily. 
 Later, however, the wires overheat and the insulation is ig- 
 nited, thus setting fire to the surrounding objects. 
 
 It is important that we become familiar with the safe 
 fusing of wires, as the capacity of standard fuses are plainly 
 marked on the outside. The smallest wire permitted in any 
 circuit, and the one most generally used on lighting circuits, 
 is No. 14, B. & S. gage and this size wire should never bo 
 fused with a fuse larger than 15 amperes, for a motor circuit, 
 nor with a fuse larger than 10 amperes, for a lighting circuit. 
 
 As another example which may cause the wires to heat, 
 is that of a poor joint or splice in a wire. When a small 
 amount of current flows the heat is not appreciable, but as the 
 current increases, owing to the poor contact, the joint heats 
 and the insulation is ignited. All splices should be well made 
 and should be mechanically and electricallv secure before 
 soldering, that the opportunity for heating at the splice, will 
 be removed. Again, we may have this overheating by poor 
 connections. A binding screw is set up securely, but, owing 
 to the vibration of the building this contact becomes loose, 
 heating takes place and the insulation on the wire is ignited 
 because of the heating conductor. 
 
 A few examples of the foregoing, the result of actual field 
 experience, may be of service at this time. 
 
One fire was due to lights being added to old wiring until 
 some of the branch circuits were overloaded. This over- 
 load and poor workmanship resulted in a fire causing a loss 
 of $190.00. 
 
 A short-circuit occurred in a flexible cord pendant de- 
 stroying the cord and burning itself out at the ceiling 
 rosette. An investigation developed the fact that blown 
 fuses on the circuit were bridged with pennies. 
 
 Heating at a loose contact on a resistance used in start- 
 ing a 100 horsepower motor, and rubber-covered wire in close 
 proximity to the contact, offered conditions which started a 
 fire in a packing plant with a resultant loss of $200.00. 
 
 An amateur extension of wiring from a standard equip- 
 ment resulted in a short-circuit on an overfused circuit and 
 a loss of $7,500.00. 
 
 A fire originated from a short-circuit above a metal 
 ceiling and spread through the open partition into the attic 
 above. The original electrical installation was good, but 
 trouble was caused by overloading the circuits. The wiring, 
 as originally installed, was for i6-candle power lamps only, 
 but these were afterwards replaced by i5O-candle power 
 lamps without increasing the size of the w r ire in the circuits. 
 The branch circuits, which under the Rules should not be 
 fused above 10 amperes, were fused for thirty amperes and 
 the main fuse block was bridged with strips of lead. Naturally 
 the fuses failed to operate and the fire caused damage to the 
 extent of $8,000.00. 
 
 BY THE FORMATION 
 OF AN ARC. 
 
 SECOND : Fires are caused by the forming of an "arc". 
 An arc is always accompanied by heat, and if it is of sufficient 
 capacity may not only ignite combustible material, but may 
 melt metals, also. Arcs may be formed between the two 
 wires of a circuit when the w r ires are too close to each other. 
 An arc may also be formed between one wire of a circuit and 
 any grounded metal, or, between an ungrounded metal and 
 another grounded metal, the former being in contact with a 
 wire of a circuit. A wooden truss may be reinforced with a 
 long metal rod, which rod may be in contact with one wire 
 of a circuit and a grounded gas pipe, where, if a sufficient 
 amount of current was flowing, an arc would be established, a 
 hole melted in the pipe and the escaping gas ignited by the 
 arc. Perhaps a short-cut definition of the word "Arc" may 
 assist in remembering what I have said: "An arc is the 
 physical evidence that current is flowing." Permit me to 
 
again draw from field experience by way of illustrating how 
 fires may be started by an "Arc". 
 
 As an example of an arc between wires, I might cite 
 w r hat may happen behind the canopy of a fixture where the 
 wires of the fixture are joined to the circuit wires. The 
 wireman, through carelessness may fail to properly tape or 
 cover the joints, and as some canopies have very little space 
 in the rear when the canopy is pushed back, the wires come 
 in contact. When the current is turned on, an arc is estab- 
 lished between the conductors which, before the fuses may 
 open may set fire to the insulation and thus to the building. 
 
 As an example of an arc between one circuit wire and 
 grounded metal, I might state an experience where one of 
 the circuit wires became grounded on the gas pipe at the 
 fixture outlet, thus establishing an arc, setting fire to shavings 
 which accumulated when the house was built. The loss was 
 $25.00 
 
 A short-circuit due to defective insulation in a combina- 
 tion fixture created an arc of sufficient intensity to puncture 
 the gas pipe below the joint and ignite the gas, with a fire 
 loss of $50.00. 
 
 A metal ceiling was put in place over porcelain cleat 
 work in a basement kitchen without the knowledge of the 
 inspection department having jurisdiction. The insulation 
 of the wire broke down because of dampness and became 
 grounded on the metal ceiling. The arcing ignited the in- 
 sulation on the wire and the fire was communicated to wood- 
 work, doing considerable damage. 
 
 As a somewhat different example of an arc the following 
 is most interesting. 
 
 The property consisted of a group of buildings, some of 
 which were used as stores, some for light manufacturing, the 
 principal occupancy being a hotel. On the front of the hotel 
 is a fire escape which acted as an electric conductor. Among 
 the wires in front of the building are some street railway feed- 
 ers. These feeders were erected before the fire escape was 
 placed on the building and with the putting in place of the 
 escape, the feeders were encased in wooden sleeves where too 
 close to the iron work. During a noon hour one of these 
 250,000 circular mill feeders, unprotected because of damage 
 to the wooden sleeve, came in contact with a handrail support, 
 and an arc was formed which lasted until the cable fused and 
 fell apart, also fusing the handrail. The fire escape extends 
 from the first to the fifth floors with a platform at each floor. 
 Its supports are secured in the stone wall except at the top 
 where the rods extend through a wooden cornice, the wall 
 
Courtesy of National Fire Protection Association. 
 
 Shows points of contact (F) between electric wires and fire escape 
 and fused rod (G). 
 
II 
 
 Courtesy of National Fire Protection Association. 
 
 Fire Escape at second floor. Sho'ws trolley feeders (A) point of 
 contact with fire escape and fused rod (B). 
 
12 
 
 Courtesy of National Fire Protection Association. 
 
 Fire escape and cornice, fifth floor, showing fused iron rod. 
 
Courtesy of National Fire Protection Association. 
 
 Fifth floor interior. Shows nut and plate (D) at end of fused rod 
 unused gas pipe (E), roof drain (F). 
 
Courtesy of National Fire Protection Association. 
 
 One of the several sewer pipes damaged or fused by heat generated 
 by resistance caused Ly poor conductivity of leaded joints. Note the 
 charred sheathing. 
 
I : 
 
 Courtesy of National Fire Protection Association. 
 
 One of the cases where electric current jumped from sewer pipes to 
 adjoining water pipes, fusing both of them. 
 
i6 
 
 and then into wooden sheathing where the rod is held by an 
 iron plate and nut. The plate and nut were in contact with 
 an unused gas pipe and this in turn w r as in contact with the 
 roof drain. The current from the feeder passing to the fire 
 escape, traveled up the iron work to the fifth floor melting 
 the metal at several points where the contact was poor. At 
 the fifth floor the current passed into the building over the 
 supporting rod, and thence to the nut, plate, gas pipe and 
 sewer piping. The supporting rod was fused on the outside 
 of the building at the fifth floor. The heat caused by the 
 current through the resistance of the leaded joints of the 
 sewer pipes ignited adjacent wood sheathing. Small fires 
 were started in different parts of the fifth floor where sewer 
 and water pipes were located, the leaded joints of cast iron 
 sewer pipes being melted. In several places where the water 
 pipes were in contact with server pipes, arcs were formed 
 which melted both. 
 
 As an example of an arc between a metal pipe and an- 
 other metal pipe, the latter being grounded, an experience in 
 a house, in the Back Bay District, Boston, some years ago, is 
 of interest. The house where the fire started did not have 
 any electric light wires in it. In the basement, a gas pipe 
 rested on a water pipe, making a slight contact. Either in 
 the ground or in an adjacent building, a wire was in contact 
 with a gas pipe. Probably due to the resistance of the joints, 
 the water pipe was a better ground than the gas mains. An 
 "arc" was established between the gas and the water pipe, 
 which melted a hole in the gas pipe, set the gas on fire, and 
 ignited the woodwork in the basement ceiling. 
 
 REQUISITES FOR 
 
 A SAFE INSTALLATION. 
 
 That the installation may be safe, attention should be 
 given to the excellence of material, simplicity in design which 
 will permit of easy inspection, and repairs of all wiring and 
 appliances. Special attention should be paid to the mechani- 
 cal execution of the work, careful connecting, soldering, taping 
 of conductors, securing and attaching of fixtures and the use 
 of "approved fittings." 
 
 ELECTRICAL TERMS 
 THEIR MEANING. 
 
 Electric power may be transmitted by either direct or 
 alternating current. 
 
 DIRECT CURRENT: By the term "Direct Current" 
 we understand it to refer to an undirectional current. As ordi- 
 
17 
 
 narily used, the term designates a practically non-pulsating 
 current. It is of such character that what is usually called 
 the "direction" of the current is always the same, or, more 
 exactly, the magnetic effects of the current are not being 
 reversed. 
 
 ALTERNATING CURRENT: An alternating current 
 is one that reverses in direction at regular intervals. Such re- 
 versals of current direction are made automatically by an 
 alternating-current generator. The number of changes in a 
 second of time is called the frequency, or cycles, 25 to 60 
 being the commonest now in commercial use. 
 
 Both direct and alternating-current systems are in use for 
 light and power, but the alternating-current has replaced 
 many of the direct-current systems, except in most Street 
 Railways and in isolated plants. Where power must be trans- 
 mitted to a considerable distance, alternating-current is used 
 because of economic reasons. Incandescent lamps, heating 
 and other current consuming devices are interchangeable on 
 the two systems-. Motor and arc lamps, however, require 
 different designs for the two systems. The same amount of 
 current will heat a conductor to the same degree of tempera- 
 ture, whether it is a direct or alternating-current system. As 
 a whole, no distinction may be made as regards the fire hazard 
 between the two systems, except that a direct current arc is 
 more severe than an alternating current arc. The same degree 
 of care in workmanship, selection of materials, insulations, 
 fuses and other protective devices should be made for both 
 systems. 
 
 CURRENT: The practical unit of electric current is 
 called AMPERE. The flow of water in a pipe is measured by 
 the quantity of water that flows through in a second, as I gal. 
 per sec., 8 gals, per sec., etc. Similarly the flow of electricity 
 in a circuit is measured by the amount of electricity that flows 
 along it in a second. More current will, all conditions being 
 equal, do more work, and will always cause more heat in the 
 conductors and appliances. Furthermore, the heating effect 
 in conductors such as, metals, varies with "the square of the 
 current", i. e., if one unit of current produces a certain amount 
 of heat in a wire, twice as much current will cause four times 
 as much heat in the same wire, three times the current will 
 cause nine times the heat and so on. The instrument for 
 measuring current is called an ammeter. 
 
i8 
 
 VOLTAGE: The electrical unit of "PRESSURE" is the 
 "VOLT". A volt means the same thing in speaking of a 
 current of electricity that a pound pressure does in speaking 
 of a current of water. Just as a higher pressure is required 
 to force the same current of water through a small pipe than 
 through a large pipe, so a higher electrical pressure is required 
 to force the same current of electricity through a small wire 
 than through a large wire. Since it is the voltage which may 
 cause electricity to pass from its proper path and seek other 
 and perhaps dangerous paths, higher voltages require better 
 insulation on wires and in appliances. The voltage used thus 
 becomes an important factor in determining the protection 
 for safety. 
 
 DIFFERENCE IN POTENTIAL: The voltage (press- 
 ure) between two points in an electric circuit, which points 
 may be between the conductors of a circuit, or between one 
 conductor of a circuit and a path to earth, is sometimes spoken 
 of as the "difference in potential", or the "drop in potential" 
 or merely the "drop", between those two points. 
 
 Where such a condition or difference exists, current may 
 pass between them. We have said that "current passing along 
 a conductor produces heat" and when it jumps between the 
 conductors or between a conductor and a path to earth it 
 produces an "arc". 
 
 RESISTANCE : Resistance is the physical property of 
 a material by virtue of w r hich it opposes the flow of an electric 
 current. The Ohm is the practical unit of resistance. All sub- 
 stances offer resistance to the passage of current. A good 
 conductor offers little resistance, while a poor conductor may 
 offer considerable resistance and then be a good insulator. 
 Copper is one of the best conductors because of its low re- 
 sistance. Iron is about one-sixth as good a conductor as cop- 
 per, and thus the same size and length of iron wire would 
 have about six times the resistance of the same size of copper. 
 Wood, when dry, is a poor conductor, but a good insulator. 
 
 OHM'S LAW : Ohm's Law is a method of expressing 
 relationship existing between the electromotive force, current 
 and resistance, and is practically the basis of most electrical 
 computations. It is expressed in various forms, as follows: 
 
 
 
19 
 
 Electromotive Force E 
 
 Current Flow - or, C= - 
 
 Resistance R 
 
 Electromotive force equals the current flow multiplied by 
 resistance. 
 
 Electromotive force = Current Flow x Resistance, or 
 E = C x R 
 
 Resistance equals the electromotive force divided by the 
 current flow. 
 
 Electromotive Force E 
 
 Resistance = - or, R = 
 
 Current Flow C 
 
 C = Amperes. E = Volts. R = Ohms. 
 Electromotive force varies directly as the current and 
 resistance. 
 
 Resistance varies directly with the electromotive force 
 and inversely as the current. 
 
 Current varies directly with the electromotive force and 
 inversely as the resistance. 
 
 In this form, "Ohm's Law" applies only to direct-current 
 circuits or non-inductive alternating-current circuits, the lat- 
 ter, however, with some modifications. 
 
 POWER : The term "watt" is merely a unit of power 
 and denotes the power used when one volt causes one ampere 
 of current to flow. The "watts" consumed when any given 
 current flows under any pressure can always be found by 
 multiplying the current in amperes by the pressure in volts. 
 Thus, if an incandescent lamp takes 0.5 amperes when burning 
 on a no- volt line, the power consumed equals 0.5 x 110 = 55 
 watts. That is, power = current x pressure, or watts = 
 amperes x volts." Thus if the current in an incandescent 
 lamp is Y-2 ampere and the voltage across the lamp terminals 
 is no volts, the power is 55 watts. With alternating current, 
 the product of the volts and amperes does not give the power 
 consumed, there being another factor known as the power 
 factor. With direct current, if the current, as read by a 
 current meter, known as an ammeter, is 100 and the volts are 
 loo then the watts are 10,000 or 10 kilowatts. With alter- 
 nating current, this power factor may be as low as .60, so that 
 the power instead of being 10,000 watts, may be only 6,000 or 
 6 kilowatts. A horse-power equals 746 watts, so that a kilo- 
 watt equals i-% H. P. and is expressed as I K. W. 
 
 MULTIPLE CONNECTION: In this system the pres- 
 sure or voltage is constant, being that required for a single 
 
20 
 
 unit. The total quantity of current, however, or the amperes 
 will vary directly as the number of units to be supplied. When 
 devices are so connected that the current has a path through 
 each separately from one circuit wire to another, they are 
 connected in "multiple" or in "parallel." 
 
 SERIES CONNECTION : In this system the same 
 current traverses in succession, or in tandem, all the trans- 
 lating devices. The electrical pressure or voltage will vary 
 directly as the number in circuit, the current, amperes, remain- 
 ing unchanged, whether one or the whole number is being 
 supplied. 
 
 CUT-OUT : A cut-out is automatic in its action and may 
 be a fuse or a circuit-breaker. A fuse is an element designed 
 to melt or dissipate at a predetermined current value, and in- 
 tended to protect against abnormal conditions of current. A 
 circuit-breaker is a device designed to open a current carrying 
 circuit without injury to itself. Both in operation correspond 
 to the safety-valve on a steam boiler. 
 
 GROUND : A ground may be either an intentional or an 
 accidental connection between a part of an electric circuit and 
 the earth, or any metal or connecting substance which are in 
 electrical connection with the earth, such as water or gas 
 pipes, metal work of buildings, etc. 
 
 SHORT-CIRCUIT: This is a condition which shortens 
 the path below the normal over which the current is supposed 
 to flow when performing its designated functions. Such a con- 
 dition is frequently the result of accident or the failure of 
 some insulation, and since it usually allows excessive currents 
 to flow, a short-circuit may be dangerous and liable to cause 
 a fire through the heating of the conductor, thus igniting its 
 insulation, or a poor contact which may cause arcing and 
 burning at the junction of the conductor. 
 
 CONSTANT-POTENTIAL SYSTEM : A constant-po- 
 tential system is one in which the pressure, or voltage, be- 
 tween the circuit wires is approximately the same at all points. 
 With such a system, as the load on the circuit increases, the 
 current increases. 
 
 CONSTANT-CURRENT SYSTEM: A constant-cur- 
 rent system is one in which the current (amperes) is main- 
 tained approximately constant, regardless of the number and 
 character of the power consuming devices on the circuit. The 
 
21 
 
 arc and incandescent lamps are usually operated on a constant- 
 current system, principally for convenience of control and low 
 cost of installation. 
 
 TWO-WIRE SYSTEM : A two-wire system is a metal- 
 lic circuit formed by two paralleling conductors insulated from 
 each other. 
 
 THREE-WIRE SYSTEM: A three-wire system is a 
 double multiple, the two outside wires are considered only 
 when the wire is being figured, as when the system is under 
 full load the neutral wire does not carry any current. The 
 three-wire system has for its chief purpose the lessening of 
 the cost of the conductors, in that three wires may be used 
 instead of four, and bears no relation to the fire hazard. 
 
 Courtesy of The Insurance Field. 
 
 An oil insulated transformer. One of the hazards in a transformer, 
 is the heating of the coils due to the flowing of electrical energy. To 
 aid in reducing this hazard the coils are immersed in oil for insulating 
 purposes, which oil will ignite at a reasonably high temperature. In 
 transformers of the larger capacity the oil is cooled by water circulating 
 in a separate compartment. 
 
 TRANSFORMERS : A transformer is a stationary in- 
 duction apparatus which changes electric energy to electric 
 energy, through the medium of magnetic energy without me- 
 
22 
 
 chanical motion. By the means of alternating current, electric 
 power may be transmitted from the generating station to the 
 point where the power is to be utilized, and then transformed 
 with small loss to a voltage better suited to motors and lamps. 
 In some of the hydro-electric stations, the alternating current 
 is generated at 2300 volts, and in some instances 6600 volts, 
 which voltage is "stepped-up", through transformers, to 66,000, 
 and even to 250,000 volts and is transmitted at the higher 
 voltage to the place where it is to be used, where it is "stepped 
 down", sometimes to several voltages, through transformers, 
 to a safe, usable voltage. It is far more economical to transmit 
 pow r er at high voltage and the usable current in many of our 
 communities is generated, by water power, many miles away 
 from its application. 
 
 Part No. 2. 
 REQUIREMENTS. 
 
 In judging of installations, it must be kept constantly in 
 mind that conditions will not improve after the wiring and 
 appliances have been in use for some time. Requirements 
 are, therefore, made to anticipate in part such deterioration 
 which may be surprisingly rapid when inferior materials are 
 put in by careless workmen, used and abused by those having 
 little or no understanding of electrical affairs and no apprecia- 
 tion of the hazard. 
 
 The hazards of electricity were early recognized, and, on 
 October 19, 1881, the New York Board of Fire Underwriters 
 issued a resolution in the following form: 
 
 "RESOLVED : That the Committee on Police and Origin 
 of Fires are hereby directed to notify the owners and occu- 
 pants of all buildings in which uncovered electric light wires, 
 or in which arc lights with open bottoms or without globes 
 are found, that the wires must be covered, and the lamps 
 altered to conform to the rules of the Board within ten days 
 from date of notice, and request that the lights shall not be 
 used until the alterations are made; and in case the altera- 
 tions are not made within said time, the Committee are hereby 
 directed to notify the members of the Board of such failure 
 and the companies insuring said property are hereby recom- 
 mended to give notice to the owners and occupants of such 
 buildings that unless the request is complied with, and the 
 
23 
 
 alterations made within a reasonable time, that the insurance 
 on said property will be canceled." 
 
 Later, in January, 1882, the same Board issued simple 
 rules on the same subject. These rules were not alone ele- 
 mentary, but indefinite, as well. A reference to them, at this 
 time, will assist in showing the progress made since that issue 
 of rules. 
 
 "Wires to be thoroughly and doubly coated with 
 
 some approved material." 
 
 "All wires to be securely fastened by some approved 
 
 non-conducting material." 
 
 "When it becomes necessary to carry w r ires through 
 
 partitions and floors, they must be secured against 
 
 contact with metal or other conducting substances 
 
 in a manner approved by the Inspector of the Board." 
 
 "The conducting frame work of chandeliers must 
 
 be insulated and covered the. same as wires." 
 
 In May, 1882, the National Board of Fire Underwriters 
 issued its first set of rules, which were later adopted by the 
 Boston Board of Fire Underwriters. The first rules of the 
 New England Exchange were issued in August, 1885. From 
 this date to the early part of 1892, rules were issued by various 
 rating organizations and, consequently, different considerably. 
 Through the initiative of Mr. C. M. Goddard, Secretary of the 
 New England Insurance Exchange, rules were prepared, in 
 1892, by the Underwriting Boards in New England, Middle, 
 South Atlantic and Gulf States. From this grew the Electri- 
 cal Committee of the Underwriters' National Electrical Asso- 
 ciation, and later in 1911 the Electrical Committee of the 
 National Fire Protection Association. 
 
 While most of the members of the old Electrical Com- 
 mittee are now members of the Electrical Committee of the 
 National Fire Protection Association, the membership of that 
 committee has been enlarged, so that it now includes repre- 
 sentatives from the 'American Institute of Electrical Engi- 
 neers, the American Electric Railway Association, The 
 National Electrical Contractors' Association, the National 
 Association, the National Association of Electrical Jobbers, 
 the National Association of Electrical Inspectors, the National 
 Electric Light Association, the Chief Electrical Inspector of 
 the City of Chicago, also the Electrical Engineer of the City 
 of New York. To these 'have since been added the Electrical 
 
24 
 
 Engineer of the United States Bureau of Standards. Our 
 standard now enjoys the endorsement of the Federal Govern- 
 ment. So you will recognize that all Associations in any way 
 interested in the varied forms of the application of electricity, 
 that it may not prove a menace to life, limb and property, have 
 a voice in the making of the National Electrical Code. 
 
 GENERATING AND 
 SUB-STATIONS. 
 
 The modern electric generating and transformer station 
 is usually constructed of brick or concrete walls, with con- 
 crete floors, concrete roof and partitions of fire resisting ma- 
 terial, so that the amount of combustible material is small. 
 
 The practice has been, for some time, to erect large sta- 
 tions from which the current is transmitted at a high voltage 
 to a number of sub-stations, where the usable voltage is ob- 
 
 Courtesy of Grouse-Hinds Company. 
 
 Rear of switchboard in a fire proof generating station. In addition 
 to the wide, clear space between the wall and the rear of the switchboard, 
 attention is called to terminal fittings marked (A) on the ends of the 
 conduit. These terminal fittings, it will be seen, give a separately insulated 
 hole for each conductor. 
 
25 
 
 tained through transformers. For example, some of the cur- 
 rent used by the Hartford Electric Light Company is gen- 
 erated at the Falls Village, Conn., hydro-electric station and 
 transmitted at 66,000 volts, which is stepped down to 11,000 
 volts at sub-stations in Torrington, Bristol, Thomaston, New 
 Britain and Hartford. From the station at Hartford, the 
 current is again transmitted to a number of sub-stations and 
 again transformed to 2300 volts. From these sub-stations, the 
 current is now sent out to Windsor, on the North ; Manchester, 
 on the east; Rocky Hill and Easthampton, on the south and 
 Unionville and the Granbys on the west. Transformers are 
 located generally on the poles in the several communities 
 served in which the current suitable for use in lamps, motors 
 and other appliances, generally 110-220 volts is obtained 
 through being transformed from the higher to the lower 
 voltage. 
 
 As another example, reference may be made to the New 
 England Power Company, which has five hydro-electric sta- 
 tions on the Deerfield River in Western Massachusetts, and 
 
 Courtesy of Turners Falls Power & Electric Company. 
 
 66,000 volt, remote control, oil switches in the sub-station of the 
 Turners Falls Power and Electric Company at Amherst, Mass. From 
 this sub-station the distribution of high-potential current to a number of 
 places in the Connecticut Valley is controlled. When disconnecting the 
 conductors of a high-potential circuit an "arc" of considerable proportions 
 is created, to prevent which the switches are opened in oil, hence the 
 term, "Oil Switches". 
 
26 
 
 one hydro-electric station on the Connecticut River, in New 
 Hampshire. These stations are connected to a 66,000 volt 
 transmission line and are serving the electrical needs in por- 
 tions of six states, extending into New York, on the west and 
 the city of Providence, on the east. 
 
 The Turners Falls Power and Electric Company of Massa- 
 chusetts, utilizes the water power of the Connecticut, Deer- 
 field and Green Rivers for generating electrical energy, having 
 hydro-generating stations on each of the rivers named. The 
 energy is transmitted at 66,000 volts and is used in three of 
 the New England States. 
 
 The distribution system of a central station is somewhat 
 similar to the blood vessel relations to the heart of the human 
 system, except that it is a system of cables, wires and other 
 distributing means to carry electrical energy throughout the 
 system from the main source of supply. Any interruption of 
 this means of carrying energy means a congestion of the 
 system which reacts back on the entire system. That this 
 interruption may be reduced to an almost negligible possi- 
 bility, stations and their equipments are now most carefully 
 planned and installed. In doing this, the hazards are greatly 
 reduced. 
 
 It is also interesting to note that the capacities of the 
 generating units are increasing in size and potential, and we 
 have not, apparently, reached the limit in size. In the first 
 commercial Edison electric lighting station, which was started 
 in Appleton, Wis., on August 15, 1882, the generating ap- 
 paratus consisted of one dynamo driven by water power and 
 had a capacity of 250 ten C. P. incandescent lamps. This was 
 equal to I and *4 K. W. The Hartford Electric Light Com- 
 pany operates 10,000 K. W. generators, while the Chicago 
 Edison Electric Illuminating Company is using generators of 
 20,000 K. W. capacity. 
 
 In a modern generating station, the equipment is usually 
 good from the viewpoint of fire hazard. The chief troubles 
 often result from crowding the equipment and the installation 
 of temporary work, always conducive to trouble when it is 
 found necessary to enlarge the capacity of the plant. Ample 
 room for operating and for inspecting is essential. Accessibil- 
 ity of all portions of electrical equipment, the use of fireproof 
 materials throughout, the installation of protective devices of 
 approved design, arid of ample capacity and arrangement by 
 
28 
 
 which any trouble may be readily confined to a limited portion 
 of the equipment, are the chief requisites of a central-station 
 equipment from the viewpoint of the electrical fire hazard. 
 
 We will recognize that the engineering requirements in 
 special cases and the complexity and variety of equipments in 
 the modern station render it manifestly impossible to be 
 solved by a pamphlet the size of the National Electrical Code. 
 In general, generators and motors of themselves present less 
 hazards than the switchboards with the mass of wiring often 
 found on them, the transformers with their charges of inflam- 
 mable oil, the electrolytic lighting arrestors, or the large con- 
 ductors carrying heavy currents and presenting large surfaces 
 of inflammable insulations. It is, of course, extremely essen- 
 tial that the rules for safe wiring should be followed in all 
 stations, and in fact, we should go further than the rules in 
 order that every precaution may be taken to avoid interrup- 
 tion of service, often as serious with public corporations as 
 the destruction of the station itself. 
 
 GENERATORS. 
 
 Perfect insulation in electrical apparatus requires that 
 the material used for insulation be kept dry. While in the 
 construction of generators, the greatest care is taken that all 
 current carrying parts are well insulated, still, if moisture 
 is allowed to settle on the insulation, trouble is almost sure 
 to occur. For this reason, a generator should never be in- 
 stalled where it will be exposed to steam or damp air or in 
 any place where, through accident, water may be thrown 
 against it. A location under steam or water pipes or close to 
 an outside window should be avoided. No combustible ma- 
 terial should be permitted near a generator as the hot particles 
 of carbon from the brushes can ignite dust in grain elevators, 
 wood-working rooms and other dust of an inflammable nature. 
 A generator should be so located as to provide for ventilation, 
 since the cooler a machine can run, the more efficient it will be. 
 
 The frames of generators operating at a high potential, in 
 excess of 550 volts, should be grounded, since it is not practi- 
 cal to attempt to insulate them. Generators operating at a 
 potential less than 550 volts should either have their frames 
 insulated from earth or be permanently and effectively 
 grounded. 
 
30 
 
 In our former lecture it was stated that a constant- 
 potential system was a system in which the potential (voltage) 
 was always the same, the current increasing with the load. 
 It is, therefore, necessary for some form of protective device 
 to be provided so that these machines may not be overloaded. 
 
 CONDUCTORS. 
 
 All wiring in a generating or sub-station should be in- 
 stalled in the most substantial manner, and care and attention 
 should be given to simplicity and orderliness of arrangement. 
 It should be readily renewable and accessible. All conductors 
 should have ample current-capacity, and in their installation, 
 care must be given to securing excellent insulation and reliable 
 supports. Special regard should be given to the possibility of 
 injury to conductors by tools, belts, ladders or from any other 
 means which may cause a gradual wear of the insulation. The 
 conductors from generators to switchboards, resistances or 
 other instruments and thence to outside lines : 
 
 Must be in plain sight or readily accessible, or if properly 
 insulated, lead encased cable may be laid in approved non- 
 combustible conduits. 
 
 Where a number of wires are brought close together, as 
 is generally the case in dynamo rooms, especially on or about 
 switchboards, they must be surrounded w T ith a tight, non- 
 combustible outer cover (not to apply to low tension bus 
 bars). 
 
 Wires shall be carried as direct as possible from the 
 switchboard to the point at which they leave the building, 
 and if leading to aerial lines shall incline downward to prevent 
 the entrance of rain along the wires. 
 
 Must be separated from contact with floors, partitions or 
 walls through which they pass, by non-combustible, non- 
 absorptive insulating tubes such as glass or porcelain, with 
 distance between sufficient to prevent possible contact. Must 
 have no air space where they pass through floors from base- 
 ment to switchboard other than that of the insulating tubes. 
 
 Other than for exciters all constant potential leads, with 
 the exception of the neutral of a three-wire system and the 
 grounded side of a railway system, must be protected by ap- 
 proved automatic cut-outs at the station. 
 
 SWITCHBOARDS. 
 
 The danger of fire at switchboards lies in the large num- 
 ber of wires usually concentrated on them, and the use of 
 
devices and appliances which are possible sources of fire. A 
 switchboard may be made of hard wood in skeleton form, in 
 which case all switches, cut-outs, instruments, etc., must be 
 mounted on non-combustible insulating bases. Switchboards 
 are more generally made, however, of slate or marble, free 
 from metallic veins. If metallic veins are not guarded against, 
 they may cause great leakage of current, which will manifest 
 itself in heating the slate or marble. The slate or marble is 
 supported on metal frames. 
 
 Courtesy of Turners Falls Power & Electric Company. 
 
 View of the switchboard operating gallery in the high-potential 
 generating station of the Turners Falls Power and Electric Company, 
 Montague City, Mass. 
 
 A switchboard should be located well away from combus- 
 tible material and should be open on all sides, that every part of 
 the switchboard and its equipment may be accessible. There 
 should be a space of at least three feet between the top of the 
 switchboard and the ceiling, in order to lessen the danger of 
 communicating fire to the ceiling. When the switchboard is 
 back connected, there should be a clear space of at least 
 eighteen inches. Every precaution must be taken to keep 
 moisture or water from a switchboard, since this, of course, 
 will result in a short circuit, as we are forced to have more or 
 less unprotected contacts. While the front of the switchboard 
 is the operating side, the rear is the part where trouble is 
 
32 
 
 more likely to occur. The back of the switchboard should, 
 therefore, be easily accessible and neatness of arrangement 
 and reliable supports for all conductors be imperative. No 
 makeshifts should be permitted on a switchboard under any 
 conditions. Absolute cleanliness, especially behind the 
 switchboard, should be insisted upon. I can recall two fires, 
 where the switchboards were located near windows, caused 
 by snow being blown through broken lights of glass. 
 
 Courtesy of Turners Falls Power & Electric Company. 
 
 Bench board and operating desk in the generating station at Montague 
 City, Mass. 
 
 RESISTANCES AND 
 EQUALIZERS. 
 
 Must be of approved type and not located in proximity 
 to combustible material. Insulated wire for connection be- 
 tween a rheostat and its contact plate should have flame-proof 
 insulation. These devices, which are used in great variety of 
 sizes and designs, resemble the valve of a steam engine, in 
 that they are regulators. In central stations where current is 
 furnished over a large area, there is on some of the circuits, 
 especially the long ones, a considerable "drop", or loss of 
 potential. In order to keep the voltage at the point of supply 
 on these circuits at the proper value, the voltage at the station 
 must be raised. This, in turn, causes the voltage on these 
 circuits near the dynamo to become excessive. Equalizers, 
 

 
 Courtesy of Trumbull Electric Manufacturing Co. 
 
 A marble switchboard, well arranged with remote control, high- 
 potential oil switches on extreme left, automatic circuit breakers, knife- 
 switches, meters and equalizers, located on the face of the switchboard. 
 This switchboard is well away from the brick wall, thus making the rear 
 of it accessible. The ends are protected by substantial wire grills, to 
 prevent using the space back of the switchboard for storage purposes. 
 This switchboard is in the basement of the Amoskeag Bank, New 
 Hampshire. 
 
34 
 
 which are large resistances generally constructed of iron or 
 strips and capable of carrying a heavy current, are connected 
 in the circuits and adjusted at such resistances as to make the 
 voltage at the various points of supply uniform. They are 
 generally too heavy to mount on the switchboard and are, 
 usually, mounted above the switchboard on non-inflammable 
 material. They are, in reality, sources of heat and should be 
 so arranged and installed that even if overheated they cannot 
 cause injury to surrounding objects. The burning out of a 
 rheostat may cause a flame or flash, and oftentimes melted 
 solder or other material is thrown off, which, if it comes in 
 contact with combustible material, will start a fire. 
 
 LIGHTNING ARRESTERS. 
 
 The purpose of these protective devices is to prevent 
 lightning, or external high-voltage currents from foreign 
 circuits entering the station and causing fire or damaging ma- 
 chinery and instruments. Lightning cannot be "stopped" but 
 may be diverted to the earth. They should be connected to 
 
 Courtesy of The Insurance Field. 
 
 The latest form of lightning arresters which involves an entirely new 
 principle for protection against lightning, is that known as the Electrolytic 
 or Aluminum Arrester. This arrester is used chiefly on high tension 
 transmission lines. The above illustration is a cross section view of the 
 device, the "inverted dishes" are called aluminum cones. Arresters of 
 this type should preferably be installed out of doors. 
 
35 
 
 every overhead circuit connected with the station. The object 
 of a lightning discharge from its beginning is to find its way 
 to earth and if it can reach it more easily by some other path 
 than by first going to the generator it will ordinarily take that 
 direction. Electricity, no matter what its character may be, 
 will choose the path of least resistance. 
 
 A lightning Arrester of the Magnetic Blow-Out Type has for its 
 purpose the protection of circuits and apparatus against lightning and 
 other abnormal potential rises of short duration. In the above illustration 
 A and B are two copper 'wings separated from each other ; the lightning 
 coming in over the line B, jumps the narrow air space to A, from which 
 it passes, by a wire connected to a water pipe or other proper earthing 
 provision direct to ground. The electro magnets, C and D, are excited 
 by a current from the generator and serve to "blow-out" the arc between 
 the wings so that the generator current cannot follow to earth. The air 
 space between the wings where they come nearest together is made great 
 enough to prevent the generator current from jumping it of its own 
 initiative, it being 'well known just how far through air currents at 
 different voltages can jump; but if the arc is first established the gases 
 generated greatly lower the resistance of the path across the air space and, 
 were some means not provided for extinguishing this arc formed by the 
 lightning discharge, it would be maintained by the generator current after 
 the lightning discharge had ceased and therein is the main fire hazard 
 from this apparatus. 
 
 In order to increase the difficulties of the lightning dis- 
 charge reaching the generators, it is customary to introduce 
 directly in the wire at some point between the arrester and 
 the machine a coil of wire known as "reactance" or "choke 
 coil", the object of which is to choke this discharge back from 
 the machine to the easier path provided through the arrester. 
 While there are a number of types of arresters, the main 
 principle embodied is common to them all ; that is, a resistance 
 and an air gap across which the current must jump to reach 
 the earth. When the discharge jumps the air gap, an arc is 
 formed and if the arrester is not designed to promptly ex- 
 tinguish this arc, the generator current is likely to follow and 
 
36 
 
 if there is anything combustible in the immediate vicinity, fire 
 may readily ensue. 
 
 The arresters must always be connected with a thor- 
 oughly good and permanent ground connection, and this 
 ground wire must be run as free as possible from kinks, coils 
 
 Courtesy of The Insurance Field. 
 
 Choke coil for the purpose of diverting lightning discharges from 
 the line to the ground. 
 
 and sharp bends. The ground connection should not be con- 
 nected to gas pipes, as there is always a liability of a very 
 severe discharge, which, with a gas service, may result in 
 melting the gas pipe and igniting the escaping gas, thus caus- 
 ing an explosion or a fire. 
 
 TESTING OF 
 INSULATION RESISTANCE. 
 
 Except where circuits are intentionally and permanently 
 grounded, a "leak" to "ground" may be the cause of arcs at 
 any point in the system which may be dangerous. The amount 
 of leak varies, but is always dependent on the insulation re- 
 sistance. Where a small amount of wire is well installed, the 
 leak should be very small, but in the case of large installations 
 or where the wiring has been poorly done, the flow of current 
 to ground or between wires of opposite polarity may become 
 quite large. Wires lying on pipes or on damp woodwork, 
 crossed wires or live parts of apparatus mounted on wooden 
 blocks, all tend to cut down the insulation resistance and in- 
 crease the leak. The effects of poor insulation are; First, it 
 represents a useless loss of current, and second, and more 
 important, it means a possible cause of fire. All circuits, 
 therefore, should be so arranged that they may be tested as 
 to their freedom from grounds and leaks. 
 
37 
 
 3t iron v,iter pipe ' /' S <,, . 77 , .' " ^T ', fT 
 
 Courtesy of The Associated Factory Mutual Fire Ins. Co. 
 
 Method of connecting the lightning arrester, choke-coil, and ground 
 wire to outside line and earth ; also showing an oil switch and line to mill. 
 
 An oscillatory discharge of lightning taken by the author in the city 
 of Hartford, July 18, 1908. 
 
33 
 
 Part No. 3. 
 ELECTRIC MOTORS. 
 
 To trace the history of the electric motor would require a 
 volume in itself, and that too, one of no mean dimensions. The 
 early history of invention in the line of electric motors in- 
 clude a number of well known names, the most prominent of 
 which, as I now recall them, are Jacobi, Ritchie, Wilde, Dai- 
 Negro, and, coming down to the present day, the well known 
 inventors whose successful electric motors are now occupying 
 so important a field in various lines of work. 
 
 I am unable to recall an electric device which is so inti- 
 mately related to our every day industrial life as the electric 
 motor. Its development and popular use has increased far be- 
 yond my ability to relate. They are now very generally used 
 in manufacturing plants of all kinds ; they are to be found on 
 the farms, far back in the country, and in our homes perform- 
 ing simple tasks in an economic manner. Their use is in- 
 creasing, as is also their opportunity, due largely, I believe, 
 to the many hydro-electric developments, w T ith their far 
 reaching transmission lines. 
 
 Portable motors of small size have come into general use 
 for drills, portable tools, vacuum cleaners, washing machines, 
 sewing machines, massaging appliances and many other pur- 
 poses where their cleanliness, economy and adaptability to all 
 service recommends them. These portable motors, however, 
 do not come under the rules prescribed for stationary motors, 
 though their use involve^, similar hazards and some others 
 peculiar to themselves. 
 
 In some respects, a motor should receive the same con- 
 sideration as a generator, in that it should be located in a 
 clean, dry place, although motors are so constructed that they 
 can be operated .out of doors and even where moisture is 
 present. Except when unavoidable, motors should never be 
 located in a dusty or linty place, and when so located should 
 be enclosed in a separate room, which room should be largely 
 of glass, so that the condition of the motor may be noted 
 from the outside. 
 
 We are now having a number of 2300 volt installations 
 for power and the requirements for these are greatly different 
 from those for motors which operate at a potential of 550 
 volts or less. The wiring for motors of the lower potential 
 may be what is termed "open work", which consists of ex- 
 
39 
 
 posed wires supported on porcelain cleats or knobs. When 
 we purpose using motors of the higher potential, however, the 
 wiring must be in multiple conductor, lead-sheathed, cable, 
 installed in an approved metal conduit, unless the installation 
 be in a central or sub-station where the men employed would 
 be familiar with the life hazards involved, when the installa- 
 tion may be in open wiring. The lead sheathing of the 
 multiple conductor cable and the metal conduit must be 
 effectively grounded, that, in event of either becoming of a 
 potential, the current may be shunted to earth. 
 
 Courtesy of Crouse-Hinds Company. 
 
 The application of electricity in cotton mills has been the subject of 
 study by Electrical Engineers for many years. This is because of the 
 deposits of lint which settle on all wires, switches, cut-outs and other 
 fixtures, ready to burst into flame at the first spark. In the above method 
 of installation all live current-carrying parts are well protected from 
 dust and lint as well as from mechanical injury. 
 
 The conduit system must be connected to the motors, 
 starting devices, switches, circuit-breakers and all appliances, 
 that there will be no exposed wiring. There are no motors in 
 commercial use between 550 volts and 2200 volts, and, when 
 making the rules, it was not thought too much to ask that a 
 
40 
 
 form of construction and installation which would provide for 
 the greatest amount of protection to the wires and the several 
 appliances should be provided. 
 
 Care should be exercised at all times to have the wires of 
 the motor circuits of sufficient size that they can care for the 
 starting current, which is always in excess of the full running 
 load. For this reason the rule requires that the conductors 
 carrying the current of only one motor must be of sufficient 
 size to carry a current at least 25 per cent, greater than for 
 which the motor is rated. This requirement applies more 
 especially to motors connected to direct current systems. For 
 motors connected to alternating-current circuits, where the 
 starting load is some times 350 per cent, greater than the full 
 running load, attention must be given to proper protection, in 
 the form of fuses or circuit-breakers of the circuit wires. 
 Where the conductors "under the rule would be overfused in 
 order to provide for the starting current, as in the case of 
 many of the alternating current motors, the conductors must 
 be of such size as to be properly protected by these larger 
 fuses. 
 
 The use of motors operated on current taken either from 
 the trolley, or from a generator directly supplying the trolley 
 system, is prohibited, owing to the fact that the trolley system 
 is always a grounded system and the current is too dangerous 
 to bring inside buildings. One side of the circuit being 
 normally grounded, there is always a tendency for the current 
 that enters the building, if opportunity offers, to find some 
 path to earth and return to the generator by that path. This 
 increases the fire hazard. These circuits are also more likely 
 to suffer from lightning. In street railway repair shops, of 
 course, these motors are permitted because the trolley current 
 is one of the hazards inherent to the risk, and this is taken into 
 consideration in classifying the risk. 
 
 The protective devices for motors are especially neces- 
 sary, since the load is usually throw r n on or off, and this load 
 may be in excess of that for which the motor was designed. 
 
 These protective devices are either in the form of fuses 
 or circuit breakers, both being automatic in operation. 
 Circuit-breakers are to be recommended, as, when the 
 breaker opens, the service can more easily be put again into 
 commission. A reference to the rule will show that the start- 
 ing device for the motor must be located in sight of the 
 
motor, except where special permission is given to deviate 
 from this rule. As can be readily understood, it is not usually 
 considered safe for a motor to be started with the operator 
 not in sight of the motor, in the event of there being any 
 derangement of the shafting, pulleys, belting, etc., or should 
 the motor fail to start and thus heat, the operator will be in a 
 position to disconnect the circuit, through the switch, before 
 serious damage has been done. 
 
 Courtesy of Crouse-Hinds Company. 
 
 Method of installing conductors in conduit to a motor with the use 
 of a floor flange which adds rigidity to the conduit. 
 
 A starting device is an appliance for limiting the current 
 strength during the starting of the motor by inserting a re- 
 sistance in series with the armature. For motors connected 
 to direct current systems a starting-box, or rheostat, is used, 
 while for motors connected to alternating current systems, the 
 starting device is somewhat different and has somewhat the 
 form of a transformer. 
 
Courtesy of Trumbull Electric Manufacturing Company. 
 
 Installation of a starting rheostat upon a slate slab, thus protecting 
 combustible material from the heat in the starting device the protective 
 fuses and starting switches are on the left of the rheostat. 
 
 In a former lecture, reference was made to the need of 
 treating resistance, or rheostats, as being sources of heat and 
 should be located away from combustible material. This is 
 usually done by mounting the rheostat on a continuous piece 
 of slate or marble, the slate or marble then independently se- 
 cured to the wall, never using, how r ever, the same screw for 
 attaching both. Motor starters for direct current motors 
 should also be provided with a no-voltage release. This in 
 its simplest form is a magnet across the line which holds the 
 lever arm of the rheostat. When the current fails, the lever 
 arm is drawn back by a coiled spring. Another device, known 
 as the "overload release" is frequently attached to a rheostat, 
 its intended office being to release the arm of the rheostat 
 should the load become greater than that for which it was 
 designed. 
 
 I have mentioned that the starting devices for alternating 
 current motors differed from those for the direct current 
 motors. These alternating current devices are called auto- 
 starters. Instead of an ohmic resistance, an inductance is 
 used to keep the current from attaining excessive value while 
 the motor is coming up to speed. These devices are generally 
 so constructed that the operator cannot leave them in a posi- 
 tion where any current passes through the starting device. 
 They are usually oil immersed, so that in case of trouble there 
 is considerable combustible material. In general, motor 
 
43 
 
 Courtesy of Commissioner James E. Cole, Wire Department, Boston, Mass. 
 
 Rheostat used in connection with motor was defective, the greater 
 portion of the coils being open-circuited, motor not taking current until 
 contact finger was on next to last button of contact points. Motor was 
 started shortly before fire was discovered, and excessive sparking at 
 commutator, due to defective condition of rheostat, occurred. Fire was 
 caused by these sparks igniting oil, lint or other inflammable material in 
 vicinity of motor. 
 
44 
 
 5 t. /ire 
 
 pheostat properly mounted. 
 
 starters, either for direct current or alternating current cir- 
 cuits, present the hazards of switches and possibly overheated 
 coils, and must be so considered and treated accordingly. 
 
 RAILWAY 
 POWER STATIONS. 
 
 In the city of Meriden, Conn., years ago, there was an 
 ungrounded trolley system which had a double overhead 
 trolley. Such a system has been advocated and even tried in 
 several other places, but, in each effort, operating difficulties 
 presented themselves. The system had two overhead wires, 
 while the cars had double trolleys. With this arrangement, 
 the tracks had no part in the return circuit, and the current 
 was kept free from ground. Practically all of the railway 
 power stations now operate with a ground return, so that in 
 case of a ground on any feed wire, we will have a dead short- 
 
45 
 
 circuit. For this reason and on account of the load carried, 
 the protection device must be of the circuit-breaker type. 
 
 STORAGE OR 
 PRIMARY BATTERIES. 
 
 Batteries of large size are now to be found in common 
 use. These are practically always storage batteries, that is, 
 batteries which are recharged by having current from a gen- 
 erator supplied to them from time to time. It always gives 
 out direct current in the reverse order from which it is 
 charged. Primary batteries are very limited in their capacity 
 and are used chiefly for signaling systems when current from 
 generators is not available. Storage batteries are now found 
 in the high voltage generating and transmission stations 
 for the remote control of the hjigh voltage oil switches and 
 circuit breakers. They are also''used to assist a station during 
 what is called the "peak load". They are also used in most 
 of the telephone exchanges and on many of the automatic 
 fire alarm systems. A storage battery may very properly be 
 called a reservoir of energy, capable of producing trouble if 
 their output is not properly controlled. 
 
 The action of the current in charging the battery liberates 
 at time large quantities of hydrogen and oxygen, and if these 
 should accumulate in the right proportions they would form 
 an explosive mixture which might be exploded by any acci- 
 dental spark, for this reason, therefore, storage battery rooms 
 must be thoroughly ventilated. As practically all of the 
 batteries in use contain sulphuric acid, it is necessary to pro- 
 vide in the battery rooms for the protection against corrosive 
 vapors. The water and acid in the rooms require that the 
 wires should be especially well insulated. 
 
 TRANSFORMERS. 
 
 At this time, we are to consider the fire hazards intro- 
 duced by transformers as they concern central and sub-sta- 
 tions, in which stations the transformers must be so placed 
 that smoke from the burning out of the coils or the burning 
 over of the oil (where oil filled cases are used) could do no 
 harm. Most of the transformers used in central or sub-sta- 
 tions contain oil for insulation and, sometimes, for cooling. 
 As the amount of oil in large transformers is considerable, and 
 
46 
 
 as it will cause a very hot fire, should it become ignited, it is 
 necessary to so locate these transformers, that in case of a 
 burn-out, the burning oil or insulation will not endanger the 
 balance of the plant. In central stations, where there is other 
 equipment, the transformers are generally placed in trans- 
 former rooms, which rooms should be well ventilated to the 
 outside air to prevent the accumulation of explosive vapors, 
 which may be given off from the oil when hot, and to facilitate 
 keeping the room cool, thus preventing overheating of the 
 transformers. These rooms should be of fire resisting material. 
 
 Courtesy of Turners Falls Power & Electric Company. 
 
 66,000 volt transformers used by the Turners Falls Power and 
 Electric Company in its outdoor station at Chicopee, Mass. The supply 
 of electrical energy for these transformers is from the hydro-electric 
 generating station on the Connecticut River at Montague City, Mass. 
 
 Provision should be made to prevent the spread of the 
 burning oil, also for quickly emptying the transformer cases 
 of oil through the means of quick-acting valves which can be 
 operated outside of the transformer rooms. In many of the 
 high-potential transmission companies, the large capacity 
 transformers are now located out-of-doors and are called 
 "out-door stations", in which stations care should be taken to 
 prevent burning oil from flowing to any buildings which may 
 be near. 
 
47 
 
 OUTSIDE WORK. 
 
 The rules for Outside Work are intended to safeguard 
 risks which may be exposed to hazards of outside electrical 
 conditions and are to be applied to all systems and voltages, 
 but are not to be considered for installations for Light, Heat 
 or Power protected by the service cut-out and switch, which 
 will be explained during a later lecture. There are several 
 ways in which outside wires may be a menace to buildings. 
 First. By producing abnormal conditions on the inside 
 wiring, as when one wire becomes grounded, there already 
 being a ground on another wire of this circuit inside the 
 building: A short circuit of wires outside causing the fuses 
 inside to blow. Special care should be taken to prevent a 
 short-circuit between open wires occurring close enough to 
 woodwork of buildings to ignite it. Second. By the crossing 
 of a high-potential wire with a low-potential, the cross being 
 when one wire of the high tension circuit touches or comes 
 in contact with a wire of the low-potential circuit. As an 
 example, I might cite the case of a 2300 volt circuit in contact 
 with a no volt circuit, which no volt circuit was intentionally 
 grounded on a water pipe in the building which it served. 
 
 This cross was made possible by the sag of the wires on 
 the pole line during a heavy snow and rain storm. The other 
 wire of 2300 volt system was grounded on the limb of a tree 
 which was heavily covered with wet snow. This established 
 a high potential cross and the wires of the low potential cir- 
 cuit rose to the higher, 2300 volt circuit. There were arcs 
 established in the fuses which blew, and the fixtures and 
 sockets, which arcs caused a number of small fires throughout 
 the one building, there being but one building on that sec- 
 ondary system. 
 
 Another example is that of a telephone wire becoming 
 crossed with a wire of a lighting circuit, either of low or high 
 potential, and, unless the telephone was properly protected 
 where it entered the building, arcs or grounds would then be 
 easily established and fire ensue as a result. Third. By wires 
 coming in contact with buildings, starting arcs or grounds 
 through damp woodwork or conductors, flashings, etc. 
 
4 8 
 
 CARE IN 
 CONSTRUCTION. 
 
 For these reasons, it is extremely important for all out- 
 side wires to be run in a substantial and careful manner, 
 especially so as not to interfere with the operations of a Fire 
 Department in the time of a fire. We sometimes find men 
 who are careless in that particular, seeking to construct the 
 outside lines in the easiest possible manner, regardless of 
 looks or safety. We can now appreciate the placing of all 
 outside wires underground, the electric light and power cir- 
 cuits installed in one set of conduits, and w r hat is called 
 signaling wires in another set of conduits, both systems of 
 conduits being independent of the other, each system being 
 provided with separate manholes. These signaling systems 
 include the telephone, the telegraph, district messenger, fire 
 and police alarm, clock and burglar alarm systems. The 
 underground system is expensive to install and may only be 
 found in cities of the larger size. 
 
 The next best method is one we sometimes see, that of 
 having one set of poles for the electric light and power wires 
 and another set for the signaling wires, thus keeping the 
 several systems separate. The objection to a system of this 
 character is largely one of appearance, it requiring two sets 
 of pole lines, one on each side of the street. It is a general 
 practice, however, when the wires are not underground, to 
 run both the electric light and power wires and the wires of 
 the signaling systems on the same set of poles. In such 
 cases, the signaling wires should not be placed on the same 
 cross-arm with the electric light and power wires. 
 
 OUTSIDE WIRES. 
 
 Line wires may have either rubber insulating or weather- 
 proof covering. The standard practice has been, however, to 
 use the latter, which consists of three cotton braids, each 
 thoroughly impregnated with a water-proof compound. This 
 covering is depended upon for accidental contact but not for 
 insulation proper. The conductors for the extra-high 
 potential transmission lines, however, are without covering 
 of any nature, but such lines are not to be seen in congested 
 areas, except they be upon very high poles, when the lines are 
 at the top out of reach of linemen when working on other 
 lines. All tie wires, as at insulators, must have an insulation 
 
49 
 
 equal to that of the wires they confine. While rubber insula- 
 tion may be used, it is much more expensive and in a few 
 years would be no better than weather-proof. 
 
 It is the general practice to support the outside wires on 
 glass or porcelain insulators at least I foot apart on pole line 
 cross-arms. These insulators are called "petticoats" and will 
 nearly always have a dry space underneath their lower edges, 
 and even if not dry, the length of the path offered to the 
 current escaping, over the wet surface is so great that the 
 leakage is small. 
 
 Courtesy of Underwriters' Laboratories, Inc. 
 
 Two splices, found in a department store, made by the "handy-man". 
 Splices improperly made are extremely hazardous because of the in- 
 security of contact, the wires 'will heat and ignite the insulation, over 
 which the flame will travel. 
 
 All joints should be well made and soldered as an un- 
 soldered joint is liable to become loosened or corroded, in 
 either of which events the contact between the w y ires would 
 become imperfect. This would cause heating at the joint and 
 might result in the w T ire being completely melted off and a 
 dangerous arc being formed at the break. A good mechanical 
 joint is required for strength should the soldering give way or 
 become corroded by traces of acid in the soldering fluid or 
 flux used. 
 
Courtesy of The Insurance Field. 
 
 Outside lines well supported over roofs. 
 
 Where outside lines are supported on buildings, they must 
 be at least 8 feet above the highest point of roofs over which 
 they pass or to which they are attached, and roof structures 
 must be substantial^ constructed and wherever feasible, wires 
 crossing buildings should be supported on poles independent 
 of the building. 
 
 This is intended to insure that under no conditions could 
 the wires sag and touch the roof ; and also that persons walk- 
 ing on the roofs could not come into accidental contact with 
 them. Roof structures are sometimes found which are too 
 low or much too light for the work, or which have been care- 
 lessly put up. A standard structure which is to hold the wires 
 a proper distance above the roof in all kinds of weather must 
 not only be of sufficient height, but must be substantially con- 
 structed of strong material. 
 
 Where outside wires are brought into buildings, special 
 precaution must be taken. These wires are known as service 
 wires or services, and should be kept free from contact with 
 anything but their designed supports. Frequently these wires 
 
ISP^tPS^^^f 
 
 Courtesy of Grouse-Hinds Company. 
 
 A good method for bringing service wires underground from an 
 overhead line to the cellar of a building. The exposed end of the conduit 
 has a terminal fitting which prevents water flowing into the conduit. 
 
53 
 
 are found to be in contact with the building, signs, shutters 
 and awnings offering an opportunity for a fire, through the 
 medium of an arc. That portion of the service wire from the 
 last outside support into the building must have rubber in- 
 sulation as an extra precaution. One method used to bring 
 these wires into a building is to have them enter through 
 bushed holes, with the porcelain bushings slanting upward 
 toward the inside, the service to have "drip loops" also that 
 water may not follow the wires inside the building and es- 
 tablish an arc around the service cut-out and the wet wood. 
 
 Service wires secured to side of building by petticoat insulators and 
 entering building through terminal fitting which prevents moisture in 
 conduit through brick 'wall. 
 
 Another method is to install the several wires in a metal 
 conduit, this conduit extending from the basement where the 
 wires enter, up the side of the building well out of the reach 
 of persons. On the upper end of the conduit a fitting known 
 as a "pipe cap" should be installed, which fitting protects the 
 wires, in the conduits, from moisture. 
 
54 
 
 Where lead covered cables are strung overhead, the out- 
 side sheath should be permanently and effectively grounded, 
 as any breakdown of insulation between the conductor and the 
 sheath makes the cable practically a bare live wire, the danger- 
 ous condition of which is obvious. The ground connection 
 required by this section keeps the sheath at the potential of 
 the earth and prevents a dangerous flow of current from the 
 sheath at any other point. The ground wire should be of 
 sufficient size and so well connected to the sheath and to the 
 earth that it can safely carry the current necessary to melt 
 the fuses protecting the cables. 
 
 Weatherproof and Rubber- 
 Covered Wire at Service Entrance. 
 
 Details of service wires entering building. 
 
 Trolley wires must be of ample size for mechanical 
 strength and are usually No. O B. & S. gage copper or No. 
 4 B. & S. gage Silicon Bronze. Protection against crosses 
 must be ample and street railway trolleys and feeder cables 
 must be capable of being disconnected at the powder stations 
 or of being divided into sections so that, in case of fire on the 
 railway route, the current may be cut-off from that particular 
 section and not interfere with the work of the fire department. 
 
 ELECTROLYSIS. 
 
 Electrolysis is the chemical decomposition of a conduct- 
 ing substance caused by the flow of current through. One 
 specific form of electrolysis is the "eating away" or corrosion 
 of underground metallic structures due to the passage of 
 stray electric currents from them. The other important form 
 
55 
 
 of electrolysis is the decomposition of electrolytes by electric 
 currents ; electroplating and electrotyping are practical ex- 
 amples of this. If a current passes from one conductor (posi- 
 tive plate or anode, Fig. i, I) through an electrolyte to an- 
 other conductor (negative plate or cathode), the electrolyte 
 will be decomposed and the anode may, under certain con- 
 ditions, also b'e decomposed. 
 
 Example. If a current be forced from one platinum 
 electrode to another through a copper sulphate electrolyte, as 
 shown in Fig. I, I, metallic copper will be dissociated from 
 the solution and deposited on the cathode. The remaining 
 components of the copper sulphate will unite with the water 
 in the "solution to form sulphuric acid. This illustrates how 
 an electric current can decompose electrolytes. This principle 
 can be readily demonstrated (Fig. I, II) by using a couple of 
 dry cells as a source of energy, a couple of iron nails as 
 electrodes and a solution of blue vitriol (copper sulphate 
 a crystal the size of a walnut in a tumbler full of water) for 
 an electrolyte and a glass tumbler for a jar. 
 
 Electrolytes are solutions in water of acids, bases, 
 (alkalies) and salts. They are decomposed when an electric 
 current passes through them. The exciting solutions in 
 primary and secondary cells and the solutions used in electro- 
 plating and electrotyping are examples of electrolytes. 
 
 Electrolysis of underground metallic structures is illus- 
 trated in Fig. 2. Direct current railway systems practically 
 always use the track as a return conductor. The return 
 current "leaks" from the track, which is always in contact 
 with the earth, and often seeks a route of minimum resistance 
 through water mains, cable sheaths and other metallic under- 
 ground structures. Where these leakage currents enter the 
 buried metallic systems (A, Fig. 2) there is no trouble. But 
 at locations (B) where the stray currents leave, electrolysis, 
 wasting away of the metal, occurs. 
 
 The action is similar to that of an electroplating process. 
 The water main in the illustration B is the anode. The 
 chemical salts in the earth in the combination with the 
 moisture in it constitute an electrolyte. The ground plate 
 or connection at the generating station is the cathode. With 
 large railway systems the leakage may be very great, in which 
 case the consequent eating aw r ay of underground metals is 
 extensive. In some cases, a service water pipe may be eaten 
 entirely through in a month. This, you will at once recognize, 
 
I- Principle 
 
 E- Experimental Outfit 
 
 Fig. 1 Illustrating Electrolysis. 
 
 ... -500-Volt Direct-Current Oenc'a'cr 
 
 ..-Trolley Wire 
 
 ">,'.".': '"'* '* '-'.'^. ...*-'".B//r. V' WatrrMa : n-' Current-'' Rail-' 
 
 "=-.-.:::::::. ^- ,' ^Current mt * ' Lwvingtoil; Return 
 
 Earth-..' ^rrr..;--.,, ;'..>-',.- / ftw /h^ 
 
 / ~ ""--T.^ "..--'*"'' Water Main 
 
 Ground ' &t St&fior: 
 
 Fig. 2 Illustrating Cause of Electrolysis of a Water Main. 
 
 Copper Hanger Wires *^ 
 
 ''-Primary Cel 13, Source of - 
 Electric Current 
 
 Fig. 3 A Silver Electroplating Outfit. 
 Tract 
 
 ft'A*. 
 
 Courtesy of The Insurance Field. 
 
 If as shown in the above diagram the tracks of a street railway, a 
 line of water pipe and a telephone cable, all form conducting paths toward 
 the power house, the current on the tracks will divide itself up and the 
 greater part stay on the tracks, but part of it taking the pipe and part 
 the telephone cable. 
 
57 
 
 bears a very close and a very vital relationship to the public 
 fire protection systems. The most effective method of cor- 
 recting such electrolytic action is to minimize the tendency 
 for its occurrence. Just how this may best be accomplished 
 all engineers have not agreed, although a number of plans 
 have been tried. One method has been that of providing a 
 low resistance path back to the generating station by connect- 
 ing the station ground directly with the rails at various 
 locations with heavy copper return conductors and bonding 
 the rails. The double overhead trolley has been tried and, 
 while this did solve the problem, in so far as electrolysis was 
 involved, it introduced several other difficulties. The United 
 States Bureau of Standards is recommending a system of 
 transpositions, or reversals, and this method is being installed 
 in the city of Springfield, Massachusetts. This method, I 
 believe, had its origin in Germany, but most of us are not 
 concerned, at this time, in anything that had its origin in 
 Germany. 
 
 Whenever a current passes through a solution of a salt 
 of a metal, the metal will be extracted electrically from the 
 solution and deposited on the negative plate or cathode. Fig. 
 i illustrates a sort of electroplating process. Electroplating 
 consists in coating by electrolysis a baser metal with copper, 
 gold, silver, nickel or almost any other metal. 
 
 Example. Fig. 3 shows a silver plating outfit. In modern 
 commercial outfits low-voltage, direct-current generators are 
 practically always used as sources of current instead of 
 primary cells. The process is about as follows : The surface 
 of the object to be plated is thoroughly cleaned of all fatty 
 matter. The object is connected to the negative pole of the 
 source of electrical energy and thus constitutes a cathode. 
 The electrolyte is a solution of some chemical salt of the 
 metal to be deposited. For silver, cyanide of silver is used ; 
 for copper, copper sulphate, etc. To maintain the strength 
 of the solution, a piece or anode of the metals to be deposited 
 is attached to the positive pole of the electro-motive-force 
 source. (Note: Electro-Motive-Force is generally expressed 
 as E. M. F.) The current in flowing through the solution de- 
 posits the metal of the solution on the cathode. Certain 
 metals such as iron, steel, zinc and lead cannot be plated with 
 certain other metals, such as gold, silver and nickel, until 1 
 after they have first been given a thin plating of copper. 
 
 Electrotyping is an electrolytic process, similar to electro- 
 plating, whereby wood cuts, type and like objects can be 
 
58 
 
 reproduced in metal, usually copper. An impression of the 
 object to be reproduced is taken in warm plaster of paris or 
 similar molding material. The surface of the mold thus 
 made is thinly coated with some fine metallic substance, such 
 as powdered graphite, to render it conducting. The mold is 
 then immersed in a copper sulphate solution bath and its 
 conducting surface is so connected to the negative pole of a 
 source of electric current that it constitutes a cathode. It is 
 then treated much like any other object to be plated. When 
 the copper coating on it has become about the thickness of a 
 visiting card, it is removed and reinforced by pouring molten 
 metal on its back. If it is to be used for printing it is backed 
 so as to be the same height as type. 
 
 In the electrolytic refining of metals the process is some- 
 what similar to electroplating (Fig. 3). The impure metal 
 to be refined is suspended as an anode in a solution of its 
 salts. Current is forced through the solution from the anodes 
 to the cathodes. Pure metal only is deposited on the cathode. 
 The impurities of the anodes fall to the bottom of the tank 
 as the pure metal is extracted from them. The electrolytic 
 refining of copper is a very important process commercially. 
 
 HIGH TENSION LINES. 
 
 A reference has been made to high tension lines, more 
 especially to the overhead lines of this class which, unless 
 properly arranged, may increase the fire loss. 
 
 "Accidental crosses between such lines and low- 
 potential lines may allow the high-voltage current to 
 enter buildings over a large section of adjoining 
 country. Moreover, such high-voltage lines, if car- 
 ried close to buildings, hamper the work of firemen 
 in case of fire in the building. The object of the rules 
 is to so direct this class of construction that no in- 
 crease in fire hazard will result, while at the same 
 time, care has been taken to avoid restrictions which 
 would unreasonably impede progress in electrical 
 development." 
 
 The very best way to guard against accidental contact 
 and crosses between the high-tension lines and other circuits 
 is to have them follow different routes. This, however, is not 
 always possible, but it has been accomplished by mutual 
 agreement of the parties interested even when a change in 
 
59 
 
 Courtesy of Commissioner James E. Cole, Wire Department, Boston, Mass. 
 
 Collection of salts on wire in a damp basement, illustrating a form 
 of electrolysis. 
 
6o 
 
 one of the routes will be necessitated. When, however, these 
 lines do cross each other, special precautions must be taken 
 to prevent contact between the two lines especially should 
 one of them* break. The rules contain detailed specifications 
 for the safe construction of crossovers and other details of 
 high-voltage lines. 
 
 TRANSFORMERS. 
 
 Transformers should preferably be kept outside of build- 
 ings. In general, it is dangerous to locate transformers with 
 oil-filled cases inside, as it is entirely possible for a breakdown 
 of insulation to ignite the oil, which may result in a very 
 stubborn fire. For the same reason, the placing of trans- 
 formers on roofs is also objectionable. Sometimes we face 
 conditions which make it necessary to install these trans- 
 
 Courtesy of The Insurance Field. 
 
 Method of installing an oil insulated transformer iri^a vault of fire- 
 proof construction. Transformer, however, should never be installed in 
 a building unless in a fireproof vault as shown above. 
 
6i 
 
 formers within buildings. When this is done, the trans- 
 formers must be installed in a fire-proof vault, having a 
 standard fire door, with a raised sill across the doorway to 
 prevent burning oil from flowing into the building. These 
 vaults should be well ventilated to the outside air and, if 
 possible, should be drained that the burning oil may flow from 
 the vault without doing further damage. 
 
 GROUNDING OF 
 SECONDARY CURRENTS. 
 
 The grounding of secondary currents is for the purpose 
 of providing protection to human life from electric shock. 
 The grounding of the secondary leads to a harmless point all 
 stray currents from any source which may become crossed 
 with the secondary service. 
 
 As early as 1900 this practice was found to be beneficial 
 by actual experiment and test, and in 1905 the subject was 
 discussed in meetings of the national electrical engineering 
 societies. From that date the practice of grounding second- 
 aries became more or less general ; beginning with 1907 var- 
 ious engineering organizations recommended the practice as 
 desirable, and in 1915 such organizations as the American 
 Institute of Electrical Engineers, the National Electric Light 
 Association, and the National Board of Fire Underwriters 
 recommended that the practice be made mandatory. 
 
 The secondary voltage value should determine the ques- 
 tion of when to ground the service, and it is now standard 
 practice to ground all secondary service in the low r er voltage 
 group, up to and including 150 volts. 
 
 There are three points at which a secondary system may 
 be grounded, namely, 
 
 At the generating station, 
 
 At the transformer, 
 
 On the customer's premises. 
 
 If the generating-station grounding point is used, it is 
 necessary to have the overhead grounded wire running over 
 all the lines carrying the secondary system, which subjects 
 linemen and overhead workers on pole lines to an unnecessary 
 hazard, brought about by the presence of this grounded wire 
 within the zone of their operations on the pole. This practice, 
 from an operating standpoint is considered undesirable. More- 
 
62 
 
 over the breaking or disconnection of this wire removes all 
 protection. 
 
 If the second, or pole-transformer, point for grounding is 
 used, the overhead system is relieved of the hazard just de- 
 scribed and the secondary service receives considerable pro- 
 tection, as theoretically any stray current getting onto the 
 circuits will be led to the ground through the grounding wire 
 run from the transformer on the pole to the ground at that 
 point, but this method does not give the greatest protection 
 to the user of electrical energy. 
 
 The third and only complete method from the protection 
 standpoint is to ground within the customer's premises, so 
 that the location of the point of protection will be as near as 
 possible to the person subject to the electrical hazard, thus 
 protecting the user from the stray currents occasioned by the 
 crossing of wires from any cause, even though such cross 
 occurs immediately outside of the building served. Such 
 grounds are free from disturbance from any outside cause. 
 
 It has been clearly demonstrated that an unreliable 
 ground is most undesirable from a protection standpoint and 
 that a ground of minimum resistance and maximum perma- 
 nency gives the most complete protection. Therefore, the 
 practice of grounding to active underground water-piping 
 systems affords the most perfect ground connection and by 
 placing such connection immediately within the walls of a 
 building served ahead of any w r ater meters or accessories a 
 protective connection is secured at the point nearest to the 
 user of the electrical energy and at a point which can best be 
 guarded for permanency of the connection. 
 
 Several years' experience throughout the United States 
 with thousands of cases of connections as just described 
 proves conclusively that a connection of this nature is in no 
 way harmful to the water-piping systems. It is fortunate that 
 this fact is recognized by nearly all of the water-distributing 
 companies throughout the country, because the continuity 
 of a good ground connection is essential for continued pro- 
 tection, and the locating of the protective connection just 
 within the walls of a building, as described, makes the guard- 
 ing and inspection of such work easy of accomplishment. 
 This, combined with the desirability of having the ground 
 connection as near as possible to the user of the current, 
 makes this point of grounding the most logical for good re- 
 
63 
 
 suits. This is a standard method and is fast becoming the 
 general practice in this country. 
 
 The ground wire should be a continuous wire without 
 joints, and of sufficient length to be connected to the service 
 side of the main line fuses. The ground wire should be at 
 least as large as the largest wire used for service mains 
 (except that a wire larger than No. oooo is not necessary), but 
 in no case should it be less than No. 6 B. & S. gage. When 
 a building is wired in metal conduit, armored cable or metal 
 raceways, the ground wire for such metal installations must 
 never be connected to the ground wire of the secondary 
 circuit. 
 
 Part No. 4. 
 
 INSIDE WORK. 
 
 In a former lecture, the intimate relationship of electricity 
 to our industrial life was shown through its application in the 
 form of power by means of the motor. The rules which we 
 will consider this evening, are for a more intimate relation- 
 ship, even into our home life, as well. We must never lose 
 sight of this fact, electricity used with discretion is the safest 
 form of energy and the rules are for the purpose of maintain- 
 ing this confidence. We should always bear in mind that 
 householders are not electrically trained, and their attention 
 is distracted from the electrical features by the other activities 
 and processes occurring about them. To the householder, of 
 course, electrical features of his household are mere incidents. 
 For this class of user of electricity, the greatest amount of 
 safeguarding, physical and educational, must be thrown about 
 the electrical wiring and equipment. 
 
 This class of rules, however, does not apply to household 
 installations and equipments alone, but contains all of the 
 rules for wiring for light, heat and power as contained within 
 buildings. They do not include the rules for Signaling Sys- 
 tems, such as telephone, telegraph, fire and police alarms, and 
 similar equipments, as these circuits do not present hazards 
 in themselves, being hazardous only from being crossed with 
 light, heat and power wires, or on account of lightning dis- 
 charges. 
 
 The present methods for wiring inside of buildings are 
 the result of experience extending over the period between 
 
6 4 
 
 the earliest applications of electricity to the present time. 
 Methods have changed as the possible dangers were recog- 
 nized, and as improved means of guarding against them were 
 devised. The net result of this experience has been on the 
 one hand an elaboration of rules and an approach to a few 
 standard systems of construction, and on the other hand the 
 production of an almost endless variety of materials available 
 for electrical purposes. 
 
 The earlier installations were laid on timbers under floors, 
 in partitions and over walls without supports, in channels cut 
 for them in wood casings or supported by wood cleats without 
 regard to protecting the wires from injury or the adjacent 
 combustible materials from being ignited by overheated wires, 
 or by arcs. It was the very best type of installation possible 
 at that time. These crude methods, however, have been most 
 wholly abandoned and it is generally conceded that the best 
 protection against electrical fires lies in the adoption of the 
 most approved methods even when the first cost of an installa- 
 tion is increased to some extent. 
 
 In buildings of the better and larger class, such as our 
 large office buildings, our present day apartment houses, 
 factories, churches and theatres, the electrical installations re- 
 ceive the same degree of careful study and planning as does 
 the general planning of the building and plans are frequently 
 made by electrical engineers acting under the instructions 
 from the architect. The possible efficiency of the installation 
 is most carefully considered, the extent of the equipment, the 
 amount of electrical energy necessary, the method of distri- 
 bution and the installation of the wires are very completely 
 arranged, that the greatest efficiency and economy may be 
 gained. This economy must not be entirely confounded with 
 the first cost; it applies to the operation of the completed 
 installation. With the smaller installations, we have our 
 greatest difficulty, inasmuch as we do not have this careful 
 planning and supervision, and the wiring oftentimes is an 
 afterthought. Frequently the work is given to the lowest 
 bidder, without regard to his understanding of the problems 
 involved or his method of solving them, and naturally we 
 have cheap construction. However, the general tendency is 
 for an improvement of all electrical installations, and with the 
 supervision which is being given by municipalities and by the 
 underwriters, as a whole, our installations are remarkably 
 
6 5 
 
 safe, and the comparatively few fires at the present time are 
 caused by defective electrical installations. 
 
 SERVICES. 
 
 The method of bringing service wires into a building re- 
 quires care and attention. We have explained the two 
 methods which are most generally used. One, you will recall, 
 was where each wire entered the building through separately 
 bushed holes, and the other was where the low-potential wires 
 entered through a metal conduit, which usually extends into 
 the basement. Rarely do we find high tension wires entering 
 buildings, and when they do, special rules which provide for 
 multiple conductor, lead sheathed cable, installed in unlined 
 metal conduits with the view of protecting the conductors 
 against moisture, are followed. 
 
 At the nearest readily accessible place to where the ser- 
 vice wires enter the building, must be installed the protection 
 of the system in the form of service fuses and service switch. 
 This switch is usually of the knife blade type and must be so 
 installed that all of the wiring within the building may be 
 entirely disconnected from the outside wires. The service 
 fuses must be placed between the service switch and the out- 
 side wires unless the switch is installed in a metal box or 
 cabinet. 
 
 The purpose of the service fuses is to protect all of the 
 wiring inside the building from overloads, and should never 
 
66 
 
 Courtesy of Metropolitan Engineering Company. 
 
 The three preceding pictures illustrate installation of meters, plug 
 and open link fuses and wires in apartment houses. These installations 
 had a number of hazardous conditions and were typical of the conditions 
 of electrical installations prior to the adoption of the National Electrical 
 Code. 
 
67 
 
 be installed, unless in a dust-tight cabinet, where there are 
 flyings of inflammable materials or so that the molten metal 
 of the ''blowing" fuse will ignite combustible and inflammable 
 material. 
 
 Service fuses and switches are in several forms, from a 
 pair of small "plug" fuses and "knife" switch mounted on a 
 porcelain or slate base to those of large capacity mounted ""on 
 slate or marble switchboard placed in a room specially ^de- 
 ned for the purpose, to which the lighting and power mains 
 are connected with separate fuses and switches to control and 
 protect the power and lighting circuits. 
 
 UNDERGROUND 
 CONDUCTORS. 
 
 It is practically necessary for underground conductors to 
 enter a building through the foundation wall, in the basement. 
 Where underground service enters building through tubes, 
 the tubes must be tightly closed atf'outlets with asphaltum or 
 other non-conducting material to prevent gases from entering 
 the building through such channels. It is not desirable to 
 have more than one underground service from a subway to 
 supply more than one building, as it is not advisable to have 
 several buildings fed through one building thus making it 
 necessary to enter the building having the general service in 
 order to cut-off the current in another building. 
 
 GENERAL RULES- 
 ALL VOLTAGES. 
 
 No wdre smaller than No. 14 B. & S. gage is permitted, 
 except for fixtures and flexible cord. This limitation is not 
 because of the carrying capacity of the wire, but it has been 
 found that wires smaller than No. 14 are not mechanically 
 strong enough to be safely used. 
 
 SPLICES. 
 
 We have had your attention drawn to the need of having 
 our joints and splices properly made. While this may seem 
 to be elementary, it is very important. A poorly made splice 
 offers a resistance to the flow of current, which resistance will 
 heat the wire and the heated wire will then inflame the insula- 
 tion. For general wiring, the underwriters have never found 
 
68 
 
 Courtesy Metropolitan Engineering Company. 
 
 Installation of cut-out and switches in 
 the cellar of a large apartment house. 
 
 individual metal cabinets in 
 
69 
 
 the equivalent for good soldered joints when all the possible 
 effects of corrosion, alternate heating- and cooling, vibration, 
 and mechanical strains are considered. After soldering, wire 
 joints or splices must be covered with an insulation equal to 
 that at other places on the conductors. This is usually done 
 by winding the splices or joints with a good rubber tape over 
 which is wound a "friction tape" of fabric impregnated with 
 compound. 
 
 WIRES. 
 
 Rubber insulated wire must be used for all concealed work 
 and when installed in damp places or in metal raceways, such 
 as conduits, thin wall conduits and armored cables. For 
 "open work" in dry places where the voltage is not over 550, 
 slow-burning insulation may be used, as it fulfills every re- 
 quirement for such work, is less expensive and will not carry 
 fire. 
 
 A good installation of open 'wiring; the wires being well supported 
 by cleats and knobs against contact with building and pipes. Wires are 
 also protected against contact with each other through means of porcelain 
 cross-over tubes, which tubes are prevented from sliding along the wires 
 by cleats secured at each end. 
 
 When not installed in conduits or other metal raceways, 
 the wires must always be separated from contact with walls, 
 floors, timbers, and partitions by non-combustible, non- 
 
absorptive, insulating bushings, such as glass or porcelain, 
 and must be kept free from all contact with pipes or any 
 conducting material. This requirement is without regard to 
 the type or extent of the insulation on the wires, the purpose 
 being that the insulation of the conductors from each other 
 and from other conducting materials must be sufficient to 
 furnish the necessary protection in case the insulation on the 
 wires is defective or becomes injured in any way. 
 
 In damp or wet places, the relative arrangement of the 
 pipes and wires should be such that the wires cannot touch 
 the pipes and so that water cannot drop from the pipes on 
 the wires. On this account it is recommended that wires be 
 above rather than below the pipes. 
 
 Two methods for protecting wires on side wall against mechanical injury. 
 
 CARRYING CAPACITY. 
 
 The Code prescribes the maximum current which shall 
 be carried on copper conductors of the different sizes. These 
 are arranged in table form and are the result of long study 
 and many careful experiments. A reference to this table, 
 which in Rule 18, of the Code, will show that Table A, which 
 applies to wires having rubber insulation, is lower than Table 
 B, which is for wires having insulation other than rubber. 
 This difference is because the rubber insulation will deter- 
 
iorate under high temperature. These tables, please remem- 
 ber, are to be used for inside work only. It has been stated 
 that for any given size of wire, a current about three times 
 as great as that given in Rule 18, will cause all ordinary in- 
 sulations to smoke, this being the margin of safety provided, 
 and is none too large considering that often wires must be 
 installed in places having fairly high temperatures, such as 
 boiler rooms, bake houses, drying rooms and lumber kilns. 
 This table of carrying capacity of wires is sometimes confused 
 with the question of drop, some installing wiremen thinking 
 that if they use a w r ire large enough so as to keep inside of 
 the allowable capacity, as stated in the table, it w r ill be ample, 
 regardless of the distance the circuit is run. 
 
 Courtesy Underwriters' Laboratories, Inc. 
 
 Fire caused between the ceiling and floor by an arc between the wires 
 for the electric light and a gas pipe. 
 
 DROP. 
 
 Since it requires power to keep a current flowing, there 
 must be some power used in keeping the current flowing- 
 through the line wires of any system. Of course, all power 
 used in this way is wasted and is therefore, called Line Loss 
 or Drop. As an example, let us consider a dynamo supplying 
 current to a motor, 500 feet away from the dynamo, and we 
 
72 
 
 will suppose the motor requires 50 amperes of current at a 
 pressure of 220 volts. From Table A, Rule 18, we find that 
 No. 6 wire could be used. But, as I have stated, some power 
 is lost in driving the current of 50 amperes through the 1,000 
 feet of line wire and, if the wire is small, its resistance will be 
 large and so more power will be lost on the line wires. So 
 you can see that the part of the dynamo voltage required to 
 drive the working current over the supply wires is called 
 "drop". Suppose, in an installation similar to the one I have 
 endeavored to make clear, it is specified that the drop shall 
 not be over I per cent, of the total voltage. One per cent, of 
 
 Courtesy of General Electric Company. 
 
 AN OIL SWITCH. 
 
 For high-tension work oil switches are used almost exclusively, and 
 in low-tension 'work they are also extensively used on account of the 
 compactness of construction and the reliability of the operation. The 
 arc being completely enclosed, this switch can be used in places where 
 there is dust or gas. The characteristic features of this type of switch 
 are: knife blade contacts submerged in oil; live parts carried on porcelain 
 base affording a permanent insulation between adjacent poles, and between 
 the frame and live parts; compactness and accessibility; enclosure of all 
 live metal parts. Each contact jaw has attached to it an arcing piece 
 which takes the final break, thus preventing any burning of the jaws. 
 The contact making parts are enclosed in a sheet metal oil tank which 
 has an insulating lining. The above pictures show the oil tank assembled 
 and separated from its supports. 
 
73 
 
 220 volts is 2.2 volts. The current in the line equals the 
 voltage to force the current over the line divided by the ohms 
 resistance of the line. 
 
 2.2 
 
 In this case, 50 = - - , or the resistance of the 
 
 resistance 
 
 2.2 
 1,000 feet of wire must not be more than - - ohms or .044 
 
 50 
 
 ohms. From the wire table of resistance as prepared by the 
 U. S. Bureau of Standards and the American Institute of 
 Electrical Engineers, we find that a No. oooo wire will be 
 required. Thus the necessity of keeping the loss of power 
 low on the line may necessitate the use of a larger wire than 
 would be needed for safety under the rules. There are cases, 
 of course, where the distance between the dynamo and the 
 load is short and where a smaller wire than that required 
 on account of the heating effect might be used and keep the 
 "drop" within reasonable limits. 
 
 SWITCHES, CUT-OUTS AND 
 CIRCUIT BREAKERS. 
 
 Even in the earliest stages of electric wiring, it was evi- 
 dent that some means must be provided for protecting electric 
 conductors, appliances, and machinery from excessive currents 
 and overloads. For this purpose, short lengths of metal con- 
 ductors having a low fusing point were placed in circuit with 
 the conductor, and were so designed that a slight increase in 
 current above the normal amount would melt the fuse and 
 open the circuit. The practice, to-day, is to use fuses of the 
 plug and cartridge type, and, under some conditions, the open 
 link fuse, which corresponds to the earliest form of fuse. 
 Circuit-breakers, which are automatic in their operation, are 
 used, instead of fuses in installations of the larger size. A 
 fuse and a circuit breaker differ somewhat, in that a fuse is 
 an element designed to melt or dissipate at a predetermined 
 value and is destroyed when its intended function has been 
 performed. A circuit breaker is designed to open a current- 
 carrying circuit, the same as a fuse, but without injury to 
 itself. A circuit breaker may be automatic or manually oper- 
 ated. 
 
74 
 
 Courtesy of General Electric Company. 
 
 EXPULSION FUSES. 
 
 The above pictures represent an expulsion fuse in and out of circuit. 
 In this device there is a short fuse wire mounted between two terminals, 
 one of which is attached to the end of a long lever. When the fuse is 
 blown this terminal is released and a spring acts upon the lever to in- 
 crease the gap between the terminals to the necessary length to put out 
 the arc. 
 
 It is quite necessary that switches and cut-outs should 
 never be installed in the vicinity of easily ignitable material 
 or where exposed to inflammable gases or dust of any charac- 
 ter, or to the flyings of any combustible materials, such as 
 would be found in cotton mills, wood working plants, flour 
 mills, grain elevators, gas houses, starch making plants, 
 bakeries, etc. In the case of switches, especially of the knife- 
 blade type, when the switch is thrown, there is more or less 
 of an arc, which will ignite flyings of combustible materials 
 or gases. While our present day enclosed fuses should blow 
 without a flash, it is not considered safe to permit them in 
 these locations, owing to the possibility of the fuse "going 
 bad", as it were, when it is called upon to operate through an 
 overload on the system which it protects. 
 
75 
 
 Courtesy of General Electric Comj 
 
 A power installation in which the starting device, which is a compen- 
 sator, is protected by automatic circuit breakers designed for use on 
 alternating current. The above is a good type of installation, all of the 
 wires being in conduit and there being no exposed current carrying parts. 
 
 CONSTANT CURRENT 
 SYSTEMS. 
 
 These systems are but little used in buildings to-day, the 
 high-efficiency lamps having almost entirely replaced them. 
 They are in general use, however, for the lighting of our 
 streets. The potential of these circuits range from 2,200 volts 
 to 4,000 volts, and it is, therefore, necessary for such wires to 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 A two-pole knife switch, which should always be mounted on a 
 slate base. 
 
7 6 
 
 be well insulated. The present make of arc lamps are en- 
 closed, and therefore there is little danger from sparks of hot 
 carbon falling from the lamps, as was the case a number of 
 years ago, when this method of lighting was so generally 
 used, the lamps at that time being of the open or unprotected 
 type. 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 Steel cabinet for the installation of cut-outs. 
 
 CONSTANT POTENTIAL 
 SYSTEMS. 
 
 In the Rules we will find the Constant Potential Systems 
 to have been divided into three classes, known as low potential 
 systems, which are of 550 volts or less ; high potential systems, 
 which are between 550 volts and 3,500 volts ; and extra high 
 potential systems, which are above 3,500 volts. 
 
 The most common in use for lighting and power are no 
 volt two-wire systems, 220 volt three-wire systems, there 
 being no volts between the neutral and either of the outside 
 wires. These two systems are used on both direct current and 
 alternating current, although alternating current has very 
 largely replaced the direct current systems. The street rail- 
 ways use a direct current system, with a ground return, which 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 A combination three-pole plug, double branch cut-out and knife 
 switches. Cut-outs of this type are intended to be used for voltages not 
 greater than 125. 
 
77 
 
 systems range from 500 volts to 600 volts. Most of our power 
 circuits are for 220 and 550 volts alternating current systems, 
 although the use of 2,300 volt alternating current motors is 
 being increased, whereas but a few years ago they were but 
 frequently seen. 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 A combination two-pole cut-out and switches, double branch, for use 
 with voltages not greater than 125. 
 
 AUTOMATIC CUT-OUTS. 
 
 These are the devices which are intended to protect the 
 circuits and appliances throughout the installation from 
 overloads, and where practicable, should be grouped so as to 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 Two and three wire single branch combination cut-out and switch, 
 intended for use on voltages not greater than 125. 
 
 make their inspection and maintenance easier, and also on 
 account of usually being able to find a safer location than 
 when they are scattered over a building. It is also better to 
 install the cut-outs in cabinets, so that a "blowing fuse" can 
 cause no trouble, other than disconnecting the circuit. 
 
 For general wiring, the rules require that no set of small 
 motors, small heating devices or incandescent lamps, nor more 
 than 16 medium size or 25 candelabra size sockets or lamp 
 receptacles requiring more 660 watts, shall ultimately be 
 dependent upon one cut-out. The purpose of this rule is to 
 secure such a subdivision of the fuses that no very large cur- 
 rents can flow for any long time over any part of the small 
 wiring without opening a fuse and thus the effects of a short- 
 circuit, or other accident will be very much minimized. 
 
Courtesy of General Electric Company. 
 
 AUTOMATIC CIRCUIT BREAKER. 
 
 The above is a circuit breaker intended to be used on a Direct Current 
 circuit. It is a device which automatically opens the circuit, without injury 
 to itself, in event of abnormal conditions in the circuit. In circuits of 
 large capacity a circuit breaker is more desirable than large fuses because 
 of the expense in replacing the latter. A circuit breaker is without the 
 hazards of the fuse, there being no molten metal when it operates. 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 Three pole knife switch, the supply end having terminals for 
 cartridge fuses, which fuses may be used on voltages as great as 250. 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 Combination two pole knife switch and cut-out, installed in a cast 
 iron box having hinged cover. Generally installed at point where service 
 wires enter the building. 
 
 The performance of melting or blowing fuses is extremely 
 variable, their behavior determined by the conditions and 
 surroundings. If there is a slight overload, as sometimes 
 occurs from substituting 60 watt lamps for 40 watt lamps, for 
 example, the temperature of the metal will gradually rise until 
 
79 
 
 its melting point is reached, when it will open the circuit 
 quietly. If, on the other hand, a sudden abnormal rise of 
 current is induced, say by a short-circuit, the fuse will tend to 
 disrupt quickly and violently. An important thing to remem- 
 
 Courtesy of General Electric Company. 
 
 A LINK FUSE. 
 
 Fuses are the most elementary form for automatically opening 
 circuits under abnormal conditions. They were first made entirely of 
 metals or alloys having a lo>w melting point. 
 
 ber is that the carrying capacity of a fuse should never ex- 
 ceed the safe-carrying capacity of the smallest wire made 
 dependent on it for protection. An exception to this rule may 
 be noted for three-wire systems with a grounded neutral. It 
 is felt that with* such systems we may omit the fuse in the 
 neutral, or permanently grounded wire, provided both wires 
 of the ultimate branch circuits controlling the lights are 
 properly protected by fuses. When cartridge fuses are used, 
 the capacity in volts and amperes will be found printed on a 
 label pasted on the outside of the tube. With plug fuses, the 
 capacity in amperes will, on 125 volt fuses, be found stamped 
 on the round metal contact in the base of the plug, or on its 
 cover, and on the 220 volt plug fuses printed on a label similar 
 to that used on the cartridge fuses. 
 
 Courtesy of Trumbull Electric Manufacturing Company. 
 
 A three pole knife switch with terminals for cartridge fuses of the 
 knife-blade type, installed in a substantial metal cabinet. 
 
8o 
 
 Courtesy of General Electric Company. 
 
 A PLUG FUSE. 
 
 A fuse is an "electrical safety valve", in that it serves to protect a 
 circuit from any harm resulting from an undue overload. Small capacity 
 fuses form an inexpensive means of protecting small circuits. In a plug 
 fuse the element is 'with the plug and never exceeds thirty amperes 
 capacity. With a very few exceptions lighting circuits should never have 
 larger than ten ampere fuses. Plug fuses should never be used on voltages 
 greater than 125, because of the short distance between terminals. 
 
 Courtesy of General Electric Company. 
 
 A LINK FUSE. 
 
 The simplest form of fuse consists of a strip of metal fixed between 
 two end pieces to fit around the terminals. When a fuse operates the 
 metal melts because of heating and the molten metal will quickly ignite 
 inflammable material. For this reason a "link fuse" should never be 
 permitted except in a dust proof cabinet or on a switchboard in a fire 
 proof room. 
 
 Courtesy of General Electric Company. 
 
 AN ENCLOSED FUSE. 
 
 The enclosed fuses are made up of paper or fiber tubes filled with 
 some material which is fireproof and which seems to suppress the arc 
 formed when the fuse, embedded in this material, opens the circuit. They 
 are made for all capacities, those in use in the mains from the storage 
 batteries in the submarines of the United States Navy being for 2,300 
 amperes. Because of the action of the powder, in suppressing the arc, 
 these fuses were first called "non-arcing fuses". 
 
 Courtesy of General Electric Company. 
 
 AN ENCLOSED OR CARTRIDGE FUSE. 
 
 The above illustrates an enclosed or cartridge type of fuse, in which 
 the space surrounding the fuse wire is filled with powdered material. 
 Because of the distance between the terminals this type of fuse may be 
 used on all commercial voltages without danger of arcing when the fuse 
 operates. 
 
8i 
 
 SWITCHES. 
 
 Service switches are generally of the knife-blade type, 
 and are mounted on either porcelain, slate or marble bases. 
 They must be so installed that current may be entirely cut 
 off from the inside wires for repairs, or in case of fire, or other 
 accident. A single-throw switch is one having one set of 
 contacts, a double-throw being where there are two sets of 
 contacts. Single-throw switches must always be installed so 
 that gravity will tend to open rather than close them since 
 otherwise they might fall and, by only partly closing, cause 
 arcs and burning. Whenever practicable, knife switches 
 should be so wired that the blades will be dead when the 
 switch is open. Switches for the control of motors, and where 
 the current used is in excess of 20 amperes, are usually of the 
 knife-blade type. 
 
 Surface Snap Switches are those which are in most com- 
 mon use and generally have a round porcelain base, with a 
 metal cover and an operating handle in the center of .the 
 cover. In use, they are generally mounted on side walls and 
 the wires are brought into them from the back. It is not 
 possible to fasten them securely to a lath-and-plaster wall 
 unless some block is provided for the screws to be driven 
 into. For this reason a %" block must be fastened between 
 the studs flush with the back of lathing to hold tubes, and 
 to support switches and fixtures, as the case may be. When 
 this cannot be done, wood base blocks, not less than y^" in 
 thickness, securely screwed to lathing, must be provided for 
 switches, and also for fixtures which are not attached to gas 
 pipes, conduit, or other form of support. The switches can 
 thus be securely and firmly screwed to the blocks and the 
 wires connected to them. When the switch wires are run 
 exposed, the snap switches should be mounted out from the 
 wall on porcelain sub-bases, so that the wires may enter the 
 switch from the back without coming in contact with the 
 wall on which the switch is mounted. 
 
 Flush switches are of the type which are inserted in the 
 wall, only the face plate, with its handle or buttons, showing. 
 That is why they are called flush switches. Inasmuch as their 
 operating parts are concealed in the wall, they should always 
 be set in enclosed iron boxes, so, should the switch go wrong 
 and arc, no flash or flame can extend outside of the metal en- 
 closure. The same general requirement applies to all small 
 
82 
 
83 
 
 fittings, such as receptacles, there being the handy devices 
 into which an attachment plug, with a flexible cord connected 
 to it, is inserted for the use of a table lamp, fan motor, small 
 cooking utensils and similar appliances. 
 
 Courtesy of.Trumbull Electric Manufacturing Company. 
 
 Three pole knife switch and cut-out installed in a metal cabinet, the 
 door of which is so arranged that the switch cannot be closed when the 
 door is open. 
 
 Sometimes it is desired to control the same lights from 
 different places, as in the case of hall lights being controlled 
 from two or more floors. This is a practical thing to do by 
 the use of three and four way switches. These switches are 
 always to be considered as single pole and are to be so con- 
 nected that only one main wire of the circuit feed is carried 
 into either switch. These switches, as I have indicated, being 
 single pole, should never be used on circuits of more than 
 660 watts. 
 
 ELECTRIC HEATERS. 
 
 Under this heading are included all devices in which use 
 is made of heat developed by the current, usually by causing 
 it to pass through coils of wire. Perhaps it may be said, with 
 some force of truth, that this branch of the application of 
 electricity has developed more forms of practical applications, 
 in the last few years, than all of the other branches. These 
 electric heating devices are in many forms, from the house- 
 hold chafing dish to the large broilers and ranges in the grill 
 rooms of the modern hotel. A few years ago, I ate my meals 
 in a restaurant, in the small town of Houlton, Aroostook 
 County, Maine, in which everything served had been cooked 
 by electricity. We have curling irons, which of course I do 
 
not use, for reasons which are obvious ; pads to take the place 
 of hot water bottles, which are without the danger of bursting 
 and thus spilling the hot water on the patient; radiators in 
 several forms ; radiant grills ; toasters, percolators, egg codlers, 
 hot water heaters, flatirons and an almost endless variety of 
 devices, all of which present the same hazards as other heaters 
 of equal capacity, except that the match hazard or the ex- 
 plosion hazard, where gas is used for cooking and heating, 
 are eliminated. 
 
 It is essential that these devices be protected by fuses in 
 the branch supply circuits and also be controlled by switches 
 which will indicate whether or not the current is "on" or 
 "off." They should never be concealed without special per- 
 mission, and when concealed should be arranged in such a 
 manner that the heater could burn up without damage to sur- 
 rounding objects. 
 
 Experience has shown the fire underwriting interests that 
 the portable heating devices are much more hazardous than 
 
 Courtesy of Commissioner James E. Cole, Wire Dept., Boston, Mass. 
 Dining room in a residence in Boston, Mass. 
 
Courtesy^of CommissionerJ'James'E. Cole, Wire Dept., Boston, Mass. 
 
 Butler's pantry in same residence. 
 
 Fire caused by defective installation of electric plate warmer, with 
 a total fire insurance loss of $180,198.06. 
 
 those of the stationary type. This is not because of a possible 
 defective installation, since the stationary heaters may be 
 suitable protected, while it is not always possible with those 
 of the portable type. The electric flatiron is perhaps the 
 cause of more trouble and danger from fire than any other 
 form of heater, a fact due entirely to use and management 
 rather than to installation difficulties. The temperature of 
 the iron required for ironing of damp fabrics is necessarily 
 high and if the iron is left with current on and is not in use 
 it will become red-hot in from ten to twenty minutes. If it is 
 left on a table or on clothing, a fire is to be expected. 
 
 All portable heaters, if they require over 250 watts of 
 energy should have approved "heater cord" which consists of 
 stranded copper conductors with a thin rubber and a thick 
 asbestos yarn covering over each, with good braid over all. 
 In factories, shops, clothing manufactories and manual train- 
 ing schools, where a large number of flatirons and other port- 
 able heaters are used, the circuits supplying them should be 
 
86 
 
 so arranged with switches that any department or section can 
 be cut-off when not in use. 
 
 Unless flatirons are small, they should not be used on the 
 ordinary lighting circuits, as they would overload such cir- 
 cuits and cause heating of the smallest w T ire on the circuit, 
 
 Courtesy of Crouse-Hinds Company. 
 
 Method suggested for the installation of an electric flatiron, the 
 fitting having a snap switch and fuses for the protection of the flexible 
 cord and flatiron. Within this fitting will be seen the tell-tale lamp, the 
 glow of which indicates whether or no current is flowing through the iron. 
 
 which wire is in the lighting fixtures. The lighting fixtures 
 and sockets are not substantially enough constructed to per- 
 mit of the rough usage which they will receive if these devices 
 are connected to them. * Electric flatirons should, in all in- 
 stances, be provided with approved stands to receive the irons 
 when not in use. 
 
Courtesy of Crouse-Hinds Company. 
 
 A luminous radiator connected to circuit wires in conduit by the 
 means of flexible cords, an attachment plug and receptacle, the latter 
 secured to a receptacle fitting. Heating devices of this type should be 
 kept well away from the woodwork of the room. 
 
88 
 
 METHODS OF WIRING. 
 
 Various methods have been standardized for the install- 
 ing of wires for low potential systems, which at the present 
 time includes all systems of 550 volts, or less. We shall con- 
 sider these methods separately. 
 
 OPEN WORK: This method of wiring is used very 
 extensively on ceilings in mills, factories, stores, and for heavy 
 conductors for feeders, mains, etc., in tunnels and in similar 
 places. Where the appearance of exposed wiring is not ob- 
 jectionable, this is one of the safest, cheapest, and best meth- 
 ods of wiring. In fact, if properly done, its appearance is far 
 from objectionable. 
 
 In dry places, up to 300 volts, it is permitted to support 
 the wires on porcelain cleats which raise the wires */2 inch 
 
 Courtesy of Crouse-Hinds Company. 
 
 Open wiring entering conduits through terminal fittings, which have 
 a separately insulated opening for each wire. 
 
89 
 
 from the surface wired over, the wires being 2^2 inches apart, 
 and for voltages between 300 and 550 the distance is to be 
 one inch, the wires being kept four inches apart. The distance 
 between supports should not be greater than 4 l / 2 feet, and if 
 the wires are liable to be disturbed, this distance should be 
 decreased. For such work, the so called slow-burning in- 
 sulation may be used. In damp places, w r ire having a rubber 
 insulation must be used and the supports must raise the wires 
 at least one inch from the surface wired over, the wires to be 
 kept 2 l /2 inches apart in systems up to 300 volts, and four 
 inches apart for systems between 300 and 550 volts. The 
 distance between supports to be such as will prevent the wires 
 being disturbed, but never less than 4^ feet. 
 
 MOULDING WORK: Moulding is now called "race- 
 
 Courtesy of Crouse-Hinds Company. 
 
 A well arranged conduit installation from a distributing cabinet to 
 the various outlets. The use of the peculiar fittings make possible the 
 absence of long bends, thus keeping the conduits close to each other. 
 
90 
 
 ways" and is sometimes used where the use of cleat work 
 would be objectionable from the standpoint of appearance, and 
 where it would be impracticable, difficult or expensive to in- 
 stall concealed wiring. Raceways, either wood or metal, 
 should never be installed in a damp place nor should they be 
 concealed. Wire having a rubber insulation must be used 
 and splices in the w r ire should not be made. Where taps or 
 extensions of wire are necessary, fittings for this purpose 
 should be used. In metal raceways, single circuits should be 
 limited to 1,320 watts and the several lengths of the raceways 
 should be electrically bonded and effectively and permanently 
 grounded. 
 
 CONDUIT WORK: The requirements of a good con- 
 duit are first, it should be fire-proof. There exists in every 
 electric conduit for light or power the elements necessary to 
 cause fire, and every precaution should be taken to prevent 
 the conduit from igniting and burning. In the second place, 
 it should be moisture proof, while, in the third place, the 
 conduit should be strong mechanically. It should resist nails, 
 
 Courtesy of Crouse-Hinds Company. 
 
 Installation of conduits with special fittings for electric flatirons in 
 a tannery-. 
 
hard blows, and should not easily be flattened by being walked 
 upon or by having wheelbarrows run over it. Lastly, the 
 conduit should withstand a "short-circuit" on the wires which 
 they contain without disrupting. Wires having a rubber in- 
 sulation should be used in conduits and the conduit system 
 should be grounded. 
 
 ARMORED CABLES: As the name implies, this 
 method consists of the wires being protected by a flexible 
 steel armor which is wound over the rubber insulated wires. 
 It is much more convenient to install, for concealed wiring, 
 than rigid conduit, to which it is inferior in one respect, since 
 the wires cannot be withdrawn should it be advisable to do 
 so. As in conduit, the armored cable systems should be 
 grounded. 
 
 Customary way of fastening flexible steel-armored cable 
 in junction or outlet box. 
 
 CONCEALED KNOB AND TUBE WORK: This 
 method of wiring is used where first cost is of the greatest 
 importance. In this method, the wires are run concealed 
 under floors and in partitions supported on porcelain knobs 
 and insulated where they pass through floors and beams by 
 porcelain tubes. The knobs are used where the conductors 
 run parallel to the joists and for vertical runs, and the tubes 
 are used w r here the w r ires pass through the joists and plates 
 or heads of partitions. Flexible tubing is used at outlets to 
 protect the wires. Here again rubber insulation is required 
 and the wires are to be supported on knobs which raise the 
 wires one inch from the surface wired over, the supports be- 
 
92 
 
 ing not greater than 4^ feet apart. While this method may 
 be open to objections, mechanical injury by artisans installing 
 their own work or making repairs, it is reasonably safe, and 
 does tend to drive out the match hazard. It is much safer 
 than kerosene or gas which it replaces. 
 
 One Inch Separation 
 From Surf ace Wired Over 
 
 Rubber- Insulake/ 
 Conductors 
 
 .. 
 
 , " Insulated 
 Conductors 
 
 >/s 
 
 I Undesirable Arranqement 
 
 - Desirable Arrangement 
 
 FIXTURE WIRING: Fixtures should be wired with 
 rubber insulated wire, except where the lighting units develop 
 excessive high temperatures, and should be insulated from 
 the gas piping and other grounded metal work of the building. 
 Under some conditions fixtures may be installed without in- 
 sulating from the grounded metal parts of the building, pro- 
 viding the insulation of the fixture wire is the same as that 
 of the circuit wires and specially designed sockets are used. 
 The ordinary wire cannot be used in the average lighting 
 
 Showing Application of "Plaster or Mud Tubes.' 
 
93 
 
 fixture because of the thickness of its insulation, so a wire 
 having a thinner insulation is permitted. 
 
 SOCKETS : Sockets used in stables or other damp 
 places, should, preferably be of the porcelain type. The or- 
 dinary key socket should be considered as a single-pole 
 switch and should never be installed where there are inflam- 
 mable gases or vapors which could be ignited by the spark 
 when turning off the current by the key, or switch, in the 
 socket. In such cases, the lamp should be in a vapor proof 
 globe as a protection to the lamp and a keyless socket used, 
 such socket to be controlled by a switch which must be 
 located beyond reach of the gases and vapors. 
 
 Qfl 
 
 FLEXIBLE TUBING ON OUTLET WIRES. 
 
 FLEXIBLE CORD: The proper and intended use of 
 flexible cord connected with electrical installations has been 
 of very great value in aiding the application of electricity and 
 nothing has caused as much harm as through its misuse. The 
 ordinary flexible cord consisting of two stranded conductors, 
 each conductor insulated with rubber and surrounded with a 
 cotton or silk braid, is intended to be used, other than in a 
 fixture, on devices which hang freely pendant in the air. It 
 
 Socket 
 
 Method of installing short pendent in damp location. 
 
94 
 
 should never be run over ceilings, down sidewalls or parti- 
 tions, or through the floors. Nor should it be used for port- 
 able devices nor in show windows. For portable purposes a 
 flexible cord similar to the one I have described, but sur- 
 rounded by a tough braided outer covering, should be used 
 that the conductors may be protected from the mechanical 
 abuse which frequently results. Flexible cords should never 
 be used in damp places, nor should they be hung on nails, 
 metal work or stapled to wood work. Adjusting devices that 
 tend to destroy the insulation of the flexible cord should not 
 be used. 
 
 Method of installing a lighting fixture on a gas pipe, showing the 
 protection of the circuit wires with flexible tubing, the insulating joint 
 and the insulating tubing on the gas pipe above the joint. 
 
 ARC LAMPS, LOW POTENTIAL CIRCUITS : The 
 progress made in the high-efficiency incandescent lamp has 
 made the arc lamp almost unnecessary for interior lighting. 
 When, however, arc lamps are to be used, common practice 
 provides for these lamps to be supplied from the ordinary 
 no or 220 volts circuit. They should be considered the same 
 as if supplied by series circuits, it being necessary to provide 
 them with globes, spark arrestors and wire netting. 
 
 Part No. 5. 
 
 In our preceding lectures, an effort was made to point out 
 electrical hazards which might be found in most any type of 
 installation. This evening, we will endeavor to make clear 
 hazards which can be found in such installations having 
 special features of use, materials and appliances. 
 
95 
 
96 
 
 VAPOR LAMPS. 
 
 An enclosed mercury vapor lamp consists essentially of 
 two separate elements, the tube or light-giving part, and the 
 operating mechanism. The tube is of clear glass of varying 
 length, from 21 inches to 55 inches, with electrodes at each 
 end and containing a small quantity of metallic mercury. The 
 air is exhausted and the tube then sealed. The mercury is 
 held in the large bulb at one end of the tube, and serves as 
 the negative electrode, the tube being always so suspended 
 that this bulb is the lowest part of the tube. The positive 
 
 Courtesy of Crouse-Hinds Company. 
 
 Installation of electric lights in a location where inflammable gases 
 are present, the lamps being located in vapor proof globes. 
 
 electrode is a small iron cup at the other end of the tube. The 
 current is conveyed to the electrodes through platinum wires 
 sealed in the glass. The current, passing from the positive 
 electrode to the negative, vaporizes some of the mercury and 
 causes the vapor to become luminous. That these lamps, 
 which are essentially intended to be used on direct-current 
 systems, may be used on alternating-current systems, an auto 
 transformer is used. The quality of the light is peculiar, it 
 
97 
 
 containing no red rays and has a peculiar bluish-green color. 
 The auto-transformer and resistance used with these 
 lamps should be treated as possible sources of heat and must 
 always be enclosed in non-combustible cases and must have 
 all openings in their casings covered with fine wire gauze 
 when installed in locations where there are flyings of lint or 
 other combustible materials. 
 
 HIGH POTENTIAL 
 VACUUM TUBE SYSTEMS. 
 
 While this form of lighting is not in general use, the Code 
 has made provision to safeguard the several hazards involved. 
 In theory it is similar to the Geissler tube and resembles the 
 mercury vapor lamp in that it consists of a conducting vapor 
 enclosed in a tube and owes its illuminosity to the incan- 
 descent particles of matter in the vapor stream. These tubes 
 vary in length from 40 to 200 feet of continuous glass tubing. 
 The conducting gas is supplied to this tube-nitrogen, emitting 
 a yellow light, gives the highest efficiency, while carbon 
 dioxide gives a white light differing little from daylight. 
 When the tube is fed with air alone, the light is a pale pink 
 color. 
 
 The terminals of the tube are brought to a terminal box 
 and sealed upon carbon electrodes which serve the purpose 
 of conducting the electricity to the gas. This terminal box 
 contains a step-up transformer with its high side connected 
 to the tube, and a regulating device to control the density of 
 the vapor in the tube. This glass tube must be so installed 
 as to be free from mechanical injury or liability to contact 
 with inflammable materials. The high potential coils and 
 regulating apparatus must be installed in a steel cabinet not, 
 less than % i ncn m thickness ; same to be well ventilated in 
 such a manner as to prevent the escape of any flame or sparks, 
 in case of burnout in the various coils. To protect against 
 dangerous shocks, any openings in the box near the high- 
 voltage parts should be effectively screened or protected by 
 other suitable means. 
 
 GAS FILLED 
 INCANDESCENT LAMPS. 
 
 This is the highest development of the incandescent elec- 
 tric lamp. Nitrogen or Argon gas is used in the bulbs which 
 
9 8 
 
 greatly increases the illuminating power of the lamp and de- 
 creases the consumption of energy. In the old carbon filament 
 lamp, 3^2 watts of energy were required for each candle- 
 power the lamp gave. The old commercial unit, the 16 candle- 
 power lamp required 55 watts of energy, whereas, the so-called 
 gas-filled lamp, in some instances, requires but J/ watt for 
 each candle-power. To achieve this result, a hazard was in- 
 troduced in the intense heat which is given off by these lamps. 
 They must never be used in a show window or in other locali- 
 ties where inflammable material is liable to come in contact 
 with the lamp equipment except when used in connection with 
 approved fixtures where the temperature of any exposed 
 portion of same does not exceed 200 degrees Fahr. If the 
 lamp is above 200 watts normal capacity, it must never 'be 
 used in the medium based sockets or receptacles. If above 
 100 watts, must not, if provided with a shade, reflector, fixture 
 or other enclosure above the socket, be used in either medium 
 or Mogul base types of sockets or receptacles having fibre or 
 paper linings. When the temperature from these lamps ex- 
 ceeds 120 degrees Fahr., the fixtures within buildings must be 
 wired with conductors of approved slow-burning or asbestos 
 covering. Where fixtures are placed outside of buildings, 
 approved rubber insulated wires is required. 
 
 OIL TRANSFORMERS. 
 
 Must not be placed inside of any building, except central 
 and sub-stations, unless by special permission, and only then 
 when they are installed in fire-proof vaults, as described in a 
 preceding lecture. 
 
 TRANSFORMERS, AIR COOLED. 
 INSIDE USE. 
 
 There are several types of air-cooled transformers which 
 are permitted within buildings because of their low capacity 
 ratings. Some electric lighting companies have a low-poten- 
 tial contract system in which no recording watt meter is used. 
 A special potential, however, is desired that the consumer may 
 not use more current than has been contracted for. That the 
 desired potential or voltage may be obtained, an air-cooled 
 transformer, called an auto-transformer, is installed within 
 the building, stepping the potential down from no volts to 
 
99 
 
 55 volts and sometimes to 27 volts. These transformers must 
 always be considered as possible sources of heat and should 
 be enclosed in iron cases. They must, also, be mounted on 
 slate or marble bases and should never be installed in closets 
 where there will be combustible and inflammable materials. 
 
 Electrical transformers for stepping down alternating- 
 currents of the usual lighting circuit to a much lower potential 
 for operating electric toys and the ringing of the ordinary 
 house bells are in general use. It can be said that small 
 electrical devices used on a few volts may have no limitations 
 as to cheapness. But it is quite otherwise with the toy trans- 
 former that is connected to the no volt circuit. It is of the 
 utmost importance that toy transformers be made as fool-proof 
 as possible. They must never be connected to systems of 
 greater than 125 volts, nor should the low-voltage rating ex- 
 ceed 25 volts. The input measured by a watt meter in the 
 high voltage side, when the low-voltage terminals are short- 
 circuited, must not be more than 25 watts. 
 
 DECORATIVE LIGHTING SYSTEMS. 
 
 Decorative lighting by means of incandescent lamps is 
 often desired either inside or outside buildings. The chief 
 hazards of such work lie in the use of inferior materials hastily 
 ' put together and poorly located and fused. The voltage of 
 such systems should never exceed 150 volts and not more 
 than 1,320 watts of energy should ever be permitted to be 
 dependent upon a single cut-out. It would be improper to 
 take current for such systems from ordinary outlets, since by 
 so doing, the wires to the outlets would be overloaded and 
 the proper fuses for the wires will have to be replaced by 
 others of too great capacity to furnish safe protection. The 
 supply should be taken only from points on the circuit where 
 the correct fusing and wiring can be provided for. 
 
 The wires are often made to serve as supports for mer- 
 chandise of very inflammable material and the conditions are 
 excellent for a rapidly spreading fire if any electrical failure 
 should occur. Incandescent lamps frequently lie against in- 
 flammable material and the fact that such an installation is 
 "temporary" does not lessen the hazards as long as it is in 
 operation and should not in any sense be considered as an 
 excuse for allowing practices which are known to be danger- 
 ous. 
 
100 
 
 ELECTRICALLY OPERATED ORGANS. 
 
 There is an electrical fire hazard in those parts of elec- 
 trically operated organs which are employed for the control 
 of the sounding apparatus, such as the reeds, pipes, drums, 
 etc., and the keyboards on the consols. The electrical energy 
 may be from a battery or a self-excited generator rated at not 
 over 15 volts. The conductors, which may be bunched in a 
 cable, must have either rubber, cotton or silk insulation. 
 When in cable form, unless installed in conduit, the outside 
 covering must either be flameproof or covered with a closely 
 wound fireproof tape. The circuits must be so subdivided and 
 protected at the generator by approved enclosed fuses of not 
 over thirty amperes capacity that every wire will be protected 
 by one or more such fuses. By such fusing at the required 15 
 volts, each circuit would then be limited to 450 watts. 
 
 THEATRES AND 
 
 MOTION PICTURE ESTABLISHMENTS. 
 
 These risks, with their electrical installations, require 
 careful attention because of the fire and life hazards involved,, 
 the latter being of the greatest importance. In the fully 
 equipped theatre, we have not alone the fire hazard from 
 electrical causes, but the hazards of scenery, dressing rooms, 
 paraphernalia and the numerous devices for producing stage 
 effects. What are termed moving picture establishments, in 
 many instances, are without the dressing rooms, scenery and 
 the other hazards of a theatre, but have a hazard, while not 
 electrical, of the greatest concern. These moving picture 
 enterprises have often been established in rooms originally 
 intended for stores and the equipment has been of the poorest 
 character. This condition has been greatly improved as ex- 
 perience has been gained and has been made the subject of 
 legislation by state, municipal and insurance interests. The 
 requirements for the electrical equipments in both of these 
 amusement enterprises are the same. In brief, they provide 
 for the following: 
 
 FIRST : There shall be two services of supply for the 
 lighting of the building, one to care for the equipment on the 
 stage and the general lighting for the auditorium; the other 
 service, which must be entirely independent of the service for 
 the general equipment, for the supply for the emergency or 
 
ioi '/; ^ v 
 
 exit lights. This provision bears but little upon the fire 
 hazard, but is intended to provide illumination sufficient for 
 the audience to pass from the building under any and all 
 conditions liable to exist, even when the general illuminating 
 system has been rendered useless. This would aid in pre-> 
 venting a panic. 
 
 SECOND: The wiring on the stage and the concealed 
 wiring in the building must be in metal conduits or armored 
 cables. Should, however, any of the wiring be exposed in the 
 auditorium, stairways or lobbies, such wiring may be in 
 conduit, armored cables or metal raceways. All of the stage 
 equipment, as well as the house lighting, except the emergency 
 or exit lights, are controlled from a switchboard located on 
 the stage. If the switchboard is on the level of the stage, a 
 railing is required across the front of the switchboard to pre- 
 vent performers coming in contact with the exposed live 
 parts of the equipment. The dimmers, footlights, borders and 
 all equipment are designed and installed with the view of pre- 
 venting contact with scenery or injury through the regular 
 use of the equipment. The proper installation of all the stage 
 devices, many of which are used for special effects, is such an 
 important feature of the safety of the theatre that special 
 rules are established for portable conductors for lights on 
 scenery, for festoons, and for many special effects. 
 
 MOTION PICTURE MACHINES. 
 
 The motion picture machines in use to-day represent the 
 combined experience of a number of efforts and are to be 
 found in use in most of the theatres for entertainment and in 
 a number of our institutions of learning for educational and 
 scientific purposes. It might be described as an intricate 
 stereopticon having an arc light in a metal housing, as an 
 illuminant. It does not, as many suppose, reproduce photo- 
 graphs of motion but does show a number of separate and 
 distinct pictures, but the speed with which these pictures are 
 shown upon the screen deceives the eye and they appear as 
 if in actual motion, rather than separate pictures with even 
 the light being withdrawn from the screen, between the 
 pictures, for a small fraction of time. This deception, or 
 optical delusion, is accomplished by a revolving shutter by 
 which the light on the screen is cut off during the movement 
 of the film and consists of three wings, one of which is rela- 
 
Courtesy of Nicholas Power Company. 
 
 Power's Cameragraph No. 6B with motor drive, 
 represents the progress made in this science. 
 
 This machine 
 

 Courtesy of Nicholas Power Company. 
 
 Mechanism showing the automatic shutter, film shields, drive crank 
 and film of Power's No. 6 Cameragraph. 
 
104 
 
 tively wide and obstructs the light on the screen during the 
 movement of the film, the other two relatively narrow and 
 adapted to interrupt the light twice while the picture is on the 
 screen, so as to prevent flicker. The pictures on the film must 
 be in absolute synchronism with this shutter. This is 
 accomplished by sprocket wheels over which the film passes 
 from the upper magazine through the head of the machine to 
 the gate, or aperture, through which the condensed light rays 
 strike the film. The film continues over other sprockets to 
 the lower magazine. The magazines, sprockets, revolving 
 shutter and gate at the aperture are all connected by gears 
 and belts to the source of power which is generally a small 
 motor. 
 
 The hazard is in the film which is made of Nitro-Cellulose 
 and is extremely inflammable, igniting without contact with a 
 flame at about 210 degrees Fahr. These films are on metal 
 reels and are from 500 feet to 2000 feet in length. The com- 
 mercial film is i- ll /32 inches wide having perforations on both 
 sides, such perforations corresponding to the sprocket wheels, 
 which have 5.4 teeth to an inch. There are 16 pictures on I 
 foot of film. These films should always be kept in metal cases 
 having tight fitting covers and should never be exposed or 
 operated unless in a booth constructed of fire-resisting ma- 
 terial, which booth must be ventilated to the outside air that 
 gases from a burning film may be quickly dissipated by the 
 means of an electric exhaust fan. All openings should be 
 equipped with automatic shutters suspended from a fusible 
 link. While it was not unusual in the earlier days of the 
 motion pictures to have the films take fire, the hazard has 
 been so well safeguarded, largely through a more intelligent 
 class of operators, that rarely do we hear of such fires. 
 
 The booths in which the moving picture machines are 
 operated are generally made of an angle iron frame, the sides 
 and tops of which are covered with asbestos building lumber, 
 generally called transite, % inch thick, securely bolted to the 
 frame. The floor is covered with the same material,. tys inch 
 thick. 
 
 FILMS. 
 
 The non-inflammable film, which does not burn with a 
 flame and which does not easily ignite, has not been the com- 
 mercial success hoped for and is but little used in the standard 
 
sized machines operated in the theatres and in other public 
 places. There is, however, a smaller equipment which is per- 
 mitted to be used without the booth required for the larger 
 equipments. These miniature equipments require a special 
 sized film, and will not take the films of the commercial size. 
 These equipments must never consume more than 600 watts. 
 The films used are of an approved slow-burning type having 
 a permanent distinctive marker. 
 
 Courtesy of Nicholas Power Company. 
 
 Complete equipment of Power's Cameragraph No. 6, which is a hand 
 driven machine. 
 
io6 
 
 Courtesy of H. W. Johns Manville Co. 
 
 A standard booth for a moving picture machine equipment. This 
 consists of frames of angle iron, covered with transite, or asbestos 
 lumber, the frames being bolted together. At the bottom of 4 sides of 
 the booth are openings covered with wire cloth of fine mesh for ventilating 
 purposes. A metal vent pipe extends from the top of the booth to the 
 outside air. 
 
 MOTION PICTURE FACTORIES, 
 STUDIOS AND EXCHANGES. 
 
 The greatest hazard of the moving picture industry is to 
 be found in the Factories, Studios and Exchanges because of 
 the great amount of film used and, frequently, the limited 
 time used in handling them. A Moving Picture Factory, 
 Studio or Exchange is considered as that building or portion 
 of a building in which moving picture films are manufactured, 
 exposed, developed, printed, rewound, repaired, stored, etc. 
 The electrical equipment must be on lines similar to those 
 required for a theatre, the lamps to be so installed that they 
 could not come in contact with a film. All current-breaking 
 devices for the electrical equipment must be enclosed in ap- 
 proved dustproof and fireproof cabinet, while all motors must 
 be of the induction type. Where Direct Current motors, how- 
 ever, must be used, they must have enclosed commutators. 
 The films must be kept in safes, vaults or cabinets, which 
 must be ventilated to the outside air. All scrap or waste shall 
 be kept under water, in self-closing standard metal cans or 
 their equivalent and any cement having collodion and amyl 
 acetate or similarly inflammable compounds shall not exceed 
 
the quantity required for one day, inside of the building, and 
 shall be limited to one gallon. 
 
 Courtesy of the H. W. Johns Manville Company. 
 
 A moving picture booth of the portable type. 
 
 OUTLINE LIGHTING. 
 
 This is a form of decorative lighting, which is most gen- 
 erally installed in a permanent form, in which rows of incan- 
 descent lamps are used on the exterior of buildings to outline 
 some pf the architectural features. The former method of 
 lighting the dome on the Capitol, at Hartford, was through 
 outline lighting, in which each lamp had its distinctive place. 
 Such systems are sometimes installed inside of buildings when 
 the regular rules for inside installations are to be followed. 
 Outline lighting on the outside of buildings, however, may 
 have special characteristics. Only systems under 550 volts 
 may be used in either open work or in conduit. When open 
 work is used, the rules for wiring in damp places should be 
 followed. These rules, you will recall, require that the wires 
 be 2^2 inches from each other and I inch from the surface 
 wired over. The circuits for outline lighting should have 
 their own separate switches and fuses, which must, if installed 
 on the outside of buildings, be installed in approved weather- 
 proof cabinets. The switches must never be of the single-pole 
 type and circuits must be so arranged that not more than 1320 
 watts will be dependent upon one cut-out. 
 
io8 
 
 / 
 
 ELECTRIC SIGNS. 
 
 The subject of electric signs has developed into a science 
 of itself. It is not my purpose to pass upon the general 
 hazards of large signs and the obstruction they offer to fire- 
 men. Signs should be substantially built because of their 
 exposure to the high winds and other elements. Preferably, 
 they should be constructed of metal. The wires should have 
 rubber insulation and should be soldered to the terminals of 
 receptacles. The flashing or animating is accomplished by a 
 machine known as a "flasher", which is really a number of 
 switches operated by a motor-driven drum. 
 
 The location of a sign flasher should be such as to remove 
 it from chance of accidental injury or tampering, to permit 
 the direct and well arranged running of circuits to it, and to 
 render it accessible for cleaning, adjusting and inspecting. A 
 flasher should never be installed in a closet or other inaccess- 
 ible place, and should be installed in a strong metal cabinet. 
 
 Courtesy of Crouse-Hines Co. 
 
 The building pictured above is the City Hall at New Orleans, La. 
 Every lamp in the outlining is held in a receptacle, mounted on a fitting 
 which protects the 'wires and lamps from the weather. The circuit wires 
 are installed in rigid conduits and because of the nature of the fittings used 
 the lamps are not enclosed in sealed globes. 
 
Courtesy of Hanlon and Murphy. 
 
 Connecticut River Bridge at Hartford, Conn. 
 
 CAR WIRING. 
 
 In the rules for the wiring of electric cars, and the equip- 
 ment of such cars, two provisions are to be considered. The 
 protection of car bodies and woodwork over all of the electri- 
 cal apparatus such as motors, resistance, contactors, heaters, 
 and the like, and over such of the conductors as are not in- 
 stalled in conduit. The other provides for wires, cables, and 
 methods of making joints and connections in them, to the 
 location and type of fuse and circuit-breakers to be used, to 
 special forms of conduit and moulding, and to details of the 
 lighting, heating, and air-pump circuits. As all of these re- 
 quirements are somewhat outside the range of this course, I 
 would suggest that the current issue of the National Electrical 
 Code be studied in detail. 
 
 CAR HOUSES AND SHOPS. 
 
 Car houses and car repair shops have electrical hazards 
 which can be greatly minimized by close adherence to the 
 special rules which are determined chiefly by the fact that the 
 railway circuit is grounded and this requires different treat- 
 ment than the ordinary light and power circuits. The trolley 
 wires must be securely supported on insulating hangers, the 
 hangers to be so spaced that should a trolley wire break, con- 
 tact with the floor cannot be made. There should be an 
 emergency switch outside of the building, that all the trolley 
 wires in the building may be cut out at one point, and the 
 
no 
 
 trolley wire be dead at all points within 100 feet of the build- 
 ing. It is also desired that the lighting and power systems be 
 so installed that one main switch may control the installation 
 independently of the main cut-out switch outside of the build- 
 ing. That the amount of current may be limited, it is de- 
 sirable that the installation be fed through an automatic 
 circuit-breaker. It is now the practice to install the wires of 
 the lighting and power circuits in a car house or a car repair 
 shop in metal Conduits. 
 
 LIGHTING AND POWER 
 FROM RAILWAY WIRES. 
 
 It should be remembered that the trolley wires of a rail- 
 way system have a grounded return and that the wires are 
 exposed to lightning. For this reason, in other than railway 
 properties, it must be noted that under no circumstances 
 should current for electric lighting or power be taken from 
 trolley or third-rail railway circuits with a grounded return. 
 The inevitable fluctuation in voltage would frequently require 
 overfusing of the circuits to prevent blowing of fuses under 
 normal conditions. Then a circuit, grounded to earth, with 
 so much capacity behind it should be kept out of factories and 
 buildings of all kinds, Except, as noted, in railway properties. 
 
 GARAGES. 
 
 In garages, in which vehicles carrying volatile inflam- 
 mable liquid for fuel or power are kept, for whatever purpose, 
 we have a hazard which is not directly of an electrical nature 
 but which may be greatly increased through an imperfect 
 electrical installation. All feed and circuit wires should be 
 installed in conduit or armored cables and all outlet, switch 
 and junction boxes should be located at least 4 feet from the 
 floor. All cut-outs, switches, receptacles and any device hav- 
 ing a current breaking part must be placed at least 4 feet from 
 the floor, that the vapor from gasoline, due to leaks, cannot 
 be ignited by the arc caused by breaking the circuit. All 
 portable lights must have keyless sockets of moulded compo- 
 sition or metal sheathed porcelain type, which sockets must 
 ,be equipped with handle, hook and substantial guard. Motors 
 and dynamos, not a part of a vehicle, if not located at least 4 
 feet from the floor must be of the fully enclosed type. 
 
Ill 
 
 ELECTRIC CRANES. 
 
 The chief hazard of electric cranes is to be found in the 
 collector wires, which wires must necessarily be bare. These 
 wires must be so mounted on insulating supports, that even 
 with extreme movements the wires will be separated at all 
 times at least ~L l / 2 inches from the surface wired over. In the 
 horizontal runs of the collector wires, they should be so 
 supported that the wires will be at least 6 inches apart. Owing 
 to the intermittent load on the motors the resistances are 
 heated considerably, requiring location for ample ventilation. 
 The motor frames, and the entire frame of the crane and the 
 tracks must be permanently and effectually grounded. 
 
 LIST OF APPROVED FITTINGS. 
 
 You will recall that during our first lecture reference was 
 made to the list of Approved Fittings. No care in installing 
 electrical equipments will entirely compensate for the use of 
 inferior or defective devices. The National Board of Fire 
 Underwriters has for many years maintained a system of 
 tests and examinations of electrical appliances, and issues 
 twice a year a "List of Electrical Appliances" which contains 
 a classified form under the names of their manufacturers all 
 of the standard and special fittings and materials which have 
 been approved. 
 
 These tests and examinations are made and the approvals 
 are issued by the Underwriters' Laboratories. The con- 
 structional details of electrical fittings and materials together 
 with the chief tests to which they are subjected, prior to 
 approval, are contained in what is known as Class "D", of the 
 National Electrical Code, to which 82 pages are devoted to 
 the specifications of electrical fittings and materials, that, in 
 so far as the manufacturers are concerned, electrical installa- 
 tions may be free from fire hazards. 
 
 SIGNALING SYSTEMS. 
 
 The rules for signaling systems govern wiring for tele- 
 phone, telegraph, (except wireless telegraph apparatus) 
 district messenger, call bell circuits, fire and burglar alarms 
 and similar systems which are dangerous and hazardous only 
 because of their liability to become crossed with electric light, 
 heat or power circuits, or from lightning. When on pole lines 
 
112 
 
 with wires for electric light and power, the signaling wires, 
 being smaller and more liable to break and fall, should gener- 
 ally be placed on the lower cross-arms. When run under- 
 ground, they should never be in the same duct or man-hole 
 with electric light or power wires, owing to the possibility of 
 the two systems becoming crossed. When these systems 
 enter a building from an overhead pole line, they should be 
 provided with proper protection at the point where the wires 
 enter the building, there being a secondary hazard to these 
 signaling systems, owing to the fact that in the extent and 
 ramification of all electrical wires there are liabilities of mis- 
 hap when, through accident, there is contact of the wires of 
 different systems, and lighting or power currents are imposed 
 upon the delicate apparatus of the telephone system ; and this 
 hazard is set aside by the operation of protectors. 
 
 PROTECTORS TO SIGNALING SYSTEMS. 
 
 At the ends of the telephone lines destructive results from 
 such foreign currents are prevented by apparatus which is 
 sub-divided into the various functions which it performs, for 
 there has not been thus far any single device of defending the 
 telephone instruments against the whole range of commercial 
 foreign currents and lightning to which they are subjected. 
 
 The first element consists of a fuse made of an alloy which 
 forms part of the circuit, and is contained in a tube of vulcan- 
 ized fiber. These fuses w r ill deflagrate when exposed to cur- 
 rents of 7 to 10 amperes, the capacity of the fuse varies 
 according to the type of apparatus. 
 
 Courtesy of The Insurance Field. 
 
 Standard protector used by the American Telephone and Telegraph 
 Co. a-a are the enclosed fuses, b-b, heat coils. If a grounded current 
 of a pressure greater than 300 volts enters the building, it will jump the 
 air space between the lightning arrester C to the ground plate D. 
 
The next element consists of a pair of small blocks of 
 carbon whose larger surface measures about one-half inch, 
 and one of these blocks is connected to the telephone circuit. 
 The corresponding block of the pair of carbons is separated 
 from it by a perforated sheet of iron and is electrically con- 
 nected with the earth. A small cavity in one of the opposite 
 faces of the carbon is filled with a button of solder such as 
 used in automatic sprinklers, and which melts at 160 degrees 
 Fahr. The distance between these carbons or the thickness 
 of the mica, is .0055 inch, being such that electricity at over 
 350 volts will pass from the carbon connected with the tele- 
 phone circuit across this space to the opposite carbon and 
 thence to the earth, thereby relieving the telephonic apparatus 
 of electrical tension exceeding 350 volts. 
 
 Courtesy of The Insurance Field. 
 
 At "a" in _ the above picture is shown a heat coil mounted between 
 the line and instrument terminals b & c, the spring c being thereby 
 held at a tension. As soon as the fused metal in the coil melts, spring c 
 is released and flies back, opening the line to the instrument and coming 
 into contact with ground connection d, lets the current from the outside 
 line be carried straight to earth over the ground wire. If this is a heavy 
 current it will blow the fuses which have been placed in the line ahead 
 and cut the wires out of circuit. The lightning arresters are shown at f. 
 
 Thus, if the foreign current exceeds the carrying capacity 
 of the tubular fuse, its deflagration opens the circuit at that 
 point. If, however, it is less in volume than the carrying 
 capacity of the fuse, and over 350 volts tension, it leaps across 
 the thin space separating the carbons, and thence passes to 
 earth. The resistance of the small arc in the space between 
 the carbons is sufficient to slightly warm the carbons, and 
 cause the fusible metal to flow from its recess and fill the space 
 between the carbons, and thus establishes a conductor of low 
 resistance to earth. This diminished resistance generally 
 causes a sufficient increase in the current imposed upon a line 
 to cause the tubular fuse to deflagrate and open the circuit, 
 
H4 
 
 if it did not do so on the first occurrence of the contact which 
 imposed the foreign current on. the telephone circuit. 
 
 Courtesy of The Insurance Field. 
 
 A type of protector used where heat coils are unnecessary. 
 
 In order to protect the fine wires of the telephonic ap- 
 paratus from injury by currents which are too small to operate 
 the tubular fuse, and of too low tension to pass to earth 
 through the carbon cutouts, a third element known as the 
 heat coil is employed, in which a fine German silver w 7 ire 
 which forms a part of the telephone circuit will be heated by a 
 current on % ampere to a temperature sufficient to release a 
 conductor ordinarily secured by fusible solder, and pass the 
 current to earth. The result of this protective apparatus is 
 to guard against mishaps to the apparatus resulting from 
 foreign currents and lightning. 
 
 WIRELESS TELEGRAPH APPARATUS. 
 
 Another form of signaling system has come into popular 
 use in the form of wireless telegraphy. This consists of a 
 number of bare wires supported through insulators on wooden 
 spreaders, which spreaders are supported overhead, generally, 
 from wooden masts, and because of the exposure to the 
 elements, are liable to high potential surges from high-poten- 
 tial transmission lines within the range of the apparatus and 
 from lightning. When these equipments are not in use, they 
 should be effectively connected to earth that the surges and 
 lightning discharges may have an easy path to ground. 
 
 MARINE INSTALLATIONS. 
 
 These installations are on vessels and must be well pro- 
 tected against moisture, since the salt air and fogs destroy 
 ordinary fittings and materials. The rules for this type of 
 installation differs from the standard rules in that special care 
 is necessary to guard against the effects of constant and 
 
Aenol 
 
 To Receiving Set 
 
 lOOMmpere 
 ^ Knife 
 Switch 
 
 No.4 8*5 
 Gouge Copper 
 Wire 
 
 Ground or 
 
 Water 
 'Pipe, 
 Street Side. 
 
 To Sending Set 
 
 Grounding aerial by knife switch on outside of building. 
 
 severe vibration, dampness and extreme hard usage to which 
 installations of vessels are always subjected. Wires arc- 
 usually installed in conduit or in moulding. Lead encased 
 cables have been used in the wiring of battleships, but such 
 method of installation has not been a success owing to the 
 cracking of the protective lead covering which permitted 
 moisture to enter and in a short time the rubber insulation 
 was destroyed. 
 
 ELECTRICAL FIRE HAZARDS 
 (A Review.) 
 
 In electric power installations, attention should be given 
 
 to the following features : 
 
 Switchboards of wood or wood-skeleton type, treated with 
 oil, varnish or insulating compound, are of antiquated 
 type, and should be replaced by those of modern design, 
 constructed entirely of non-combustible, non-absorptive, 
 insulating materials. Switchboards built of planks closely 
 nailed together are especially dangerous. 
 
 All switchboards must be provided with a reliable ground- 
 detecting device and necessary circuit breakers or fuses of 
 a standard type. 
 
 Observe that terminals of underground conduit or ducts at 
 both generator and switchboard are properly sealed and 
 so located as to prevent the entrance of water or dirt 
 therein. All such terminals should extend above floor 
 line the full limit of available space. 
 
(d) Fuses require constant supervision and should be preferably 
 
 of the enclosed type. 
 
 (e) Space behind switchboard must be kept free from rubbish or 
 
 combustible materials. 
 
 (f) All outgoing lines should be provided with approved lightning 
 
 arresters. 
 
 (g) The arrangement and spacing of cables should be observed. 
 
 Even in instances of lead covered cables an arc may melt 
 off the lead and burn the insulation. Cables should not 
 be too closely bunched or grouped; extensive damage to 
 insulation may result from fire in bunched cables. 
 
 (h) Old-fashioned oil switches with open top and w r ooden interi- 
 ors, where found, should be replaced with approved de- 
 vices. 
 
 (i) Current transmitted from high-voltage lines should enter 
 transformers properly installed outside of buildings, or in 
 a well ventilated fireproof vault properly cut-off. Oil- 
 filled transformers should always be surrounded by a 
 curbing of sufficient height to contain as much oil as is 
 contained in the transformers themselves, and ample 
 drainage should be provided at floor level. Note that oil- 
 filled transformers should never be installed inside of main 
 building, if possible to avoid it. 
 
 (j) No oils or volatiles of any kind should be kept in generator 
 room except the daily supply of lubricating oils in metal 
 receptacles. There should be no accumulations of dry or 
 used waste in generator room. Adequate standard metal 
 waste cans and hand fire protection should be installed. 
 
 ELECTRIC MOTORS. 
 
 All motors should be installed in a dry and well lighted 
 location, to which free access may be had at all times. 
 
 (a) Motors should be equipped with a substantial metal drip pan 
 
 to catch all waste oil. 
 
 (b) All motors, regardless of size, should be protected by proper 
 
 fuses or circuit breakers, and switches at each motor 
 should be of a type that will positively cut-off all current 
 when motor is not in operation. All starting boxes and 
 controlling devices, except in specially authorized cases, 
 should be in immediate sight of motor. 
 
 (c) All motors installed in dusty and dirty places where readily 
 
 ignitable material is present, should be of enclosed type or 
 be placed in enclosures constructed preferably of non- 
 combustible material with ample amount of fine wire 
 screen to afford good ventilation. 
 
 (d) To avoid such locations where possible, it is advisable that 
 
 motor should drive machinery through the medium of a 
 shaft fitting tightly in a wall bushing, motor being on 
 opposite side of wall or partition. 
 
(e) All 'rheostats and starting boxes, unless mounted on switch- 
 
 boards, should be mounted on slate or other non-com- 
 bustible insulating material, unless mounted on substan- 
 tial brackets which will separate them one foot from com- 
 bustible material, or unless mounted on cement or con- 
 crete walls or floors. 
 
 (f) Motors must be of sufficient capacity; must be kept clean, 
 
 must be regularly oiled and otherwise given proper care, 
 and commutators kept smooth. 
 
 (g) Motors should be in care of a competent man who should 
 
 periodically inspect them. 
 
 ELECTRIC LIGHTING HAZARDS. 
 
 All equipments for electric lighting, heating, etc. should 
 conform to the following, which are suggestions for field 
 practice. 
 
 (a) All wires must be properly supported, insulated and protected 
 
 against mechanical injury, so that system may be kept 
 / free from grounds and short circuits. Observe whether 
 ground wires for conduit and secondary systems remain 
 undisturbed and that connections of ground wires to 
 conduit and water pipe or other grounded metal work are 
 also undisturbed and in good order. Telephone, bell, and 
 other signal wires should also be observed and be made 
 free from contact with electric light wires. Crosses out- 
 side are frequently as dangerous as inside of buildings. 
 Recommend that wires be made rigid and free from 
 sagging. 
 
 (b) Wires must be of ample capacity to prevent overheating; all 
 
 joints must be properly soldered and taped so as to insure 
 perfect contact ; wires must be protected by fuses of proper 
 size and of approved type against overload and short 
 circuits. 
 
 (c) If installed in the vicinity of easily ignitable material, cut- 
 
 outs must be enclosed in standard cabinets. If not of 
 metal, cabinets must be properly lined. Door, latch, and 
 hinges should be kept in proper order. Cut-outs and 
 switches must not be installed in rooms subjected to in- 
 flammable vapors, nor in rooms wherein hazardous pro- 
 cesses are conducted, unless by special permission and 
 provision for special safeguards. 
 
 (d) Where volatile vapors or dangerous explosives are prevalent, 
 
 suggest conduit system of wiring and the use of vapor- 
 proof globes. Switches and cut-outs controlling these 
 circuits should be installed outside of the room where any 
 hazardous process is conducted, unless by special per- 
 mission and provision for special safeguards. Where 
 necessary, suggest the use of metal guards about swinging 
 globes. 
 
n8 
 
 (e) See that all fuses are of standard type and in good condition. 
 
 Suggest the removal of substitutes, such as nails, hairpins, 
 and the like. Observe contact parts of cartridge fuse 
 blocks. 
 
 (f) Observe if all fixtures are properly connected and supported; 
 
 ascertain if any circuits are overloaded by attachment of 
 too many lamps. 
 
 (g) All pendant lamps must be provided with approved cord, and 
 
 be free from contact with furniture, nails, pipes, machinery, 
 and other fixtures. Lamps of a portable type must be 
 equipped with approved reinforced cord, to insure pro- 
 tection against abrasion. Heavy guards are recommended 
 for lamps attached to portable cords. 
 
 (h) Condemn the use of paper and other combustible shades on 
 lamps. Where shades are necessary, suggest those of a 
 non-combustible type. Recommend the removal of any 
 temporary attachments, artistic displays, and extensions 
 improperly made. 
 
 (i) Electric heating devices should be protected against danger 
 of communicating fire to adjacent materials, as to con- 
 struction, connection and mounting. Note the installation 
 of special apparatus such as electric welding machines, 
 electric furnaces and ovens, cloth cutters, etc., etc., and if 
 such apparatus appears carelessly or improperly installed, 
 notify or confer with the inspection department having 
 jurisdiction. 
 
 (j) Lighting and power from railway wires must not be permitted 
 under any pretense on the same circuit with trolley wires 
 with a ground return, except in railway cars, electric car 
 houses, power houses, passenger and freight stations con- 
 nected with the operation of electric railways. 
 
 (k) Obsolete types of electrical equipments are occasionally met 
 with, especially hazardous features of which are wooden 
 cleats, rosettes, and fuse blocks, knife switches of unsafe 
 dimensions, often mounted upon wooden bases and 
 wooden case rheostats. Wires and flexible cord in such 
 instances will be found to have very inferior insulation. 
 Equipments of this character should usually be replaced, 
 as in most cases they may be considered as beyond possi- 
 ble repair short of a new installation. 
 
 Bibliography. 
 
 Associated Factory Mutual Fire Insurance Companies: Rules 
 for electric light and power equipments, consisting of the 
 National Electrical Code, with supplementary notes. Ed. 
 of 1915. Inspection Department, 31 Milk Street, Boston. 
 
 Ralph Sweetland : Electrical Hazards. Four lectures delivered 
 before the Insurance Institute, Boston, Mass., 1911. The 
 Insurance Library Association, 141 Milk Street, Boston, 
 Mass. 
 
Tig 
 
 Washington Devcrcux: Electrical Key, for use of electrical 
 inspection bureaus in advising electrical contractors, 
 wiremen, etc., of corrections required so that installations 
 will conform to the National Electrical Code. Published 
 by the author, Phila., Pa. 
 
 Horstman & Tousley: Modern Electrical Construction. 2nd 
 Edition. Frederick J. Drake & Co., Chicago, 1908. 
 
 National Board of Fire Underwriters: Rules and Require- 
 ments for electric wiring and apparatus as recommended 
 by the National Fire Protection Assoc. Edition of 1915, 
 with changes suggested for the 1918 edition. Boston, 
 Mass. 
 
 Dana Pierce : Underwriters' requirements for safe electrical 
 installations. Volume 3, Cyclopedia of Fire Prevention 
 and Insurance. 
 
 A. M. Schoen : Manual of electricity. A reference book for 
 the use of fire underwriters. Louisville, Ky., 1911. The 
 Insurance Field Co. 
 
 C. J. H. Woodbury: The Electrical Fire Hazard. Boston, 
 Mass. 1905. Alfred Mudge & Son. 
 
 C. J. H. Woodbury : History of the National Electrical Code. 
 1906. National Electrical Contractor. Utica, N. Y. 
 
 Terrell Croft: American Electricians' Hand Book. A refer- 
 ence ' book for practical electrical workers. 1914. 
 McGraw-Hill Book Co. 
 
 W. H. Timbie: Essentials of Electricity. 1914. John Wiley 
 & Sons. 
 
 W. H. Timbie : Elements of Electricity. 1914. John Wiley & 
 Sons, N. Y. 
 
 C. E. Knox: Electric Light Wiring! 1907. McGraw Pub. Co., 
 N. Y. 
 
 W. E. Barrows: Electrical Illuminating Engineer. 1908. 
 McGraw Pub. Co. 
 
 Newton Harrison: Electric-Wiring, Diagrams and Switch- 
 boards. 1906. The Norman W. Hanley Publishing Com- 
 pany, N. Y. 
 
 Albert Blauvelt: Electrical Fire Hazard: How to judge it 
 and what to do. 1895. Rollins Publishing Co., Chicago. 
 
 Edwin J. Houston : Electricity, One Hundred Years Ago and 
 To-day. 1894. McGraw Pub. Co. 
 
 Nicholas Power: "Power's Cameragraph." 1910. Catalogue, 
 
 Nicholas Power Co., N. Y. 
 
 A. E. Watson : A Handbook of Wiring Tables. 1904. Bubier 
 Pub. Co. Lynn, Mass. 
 
 American Institute of Electrical Engineers: Standardization 
 Rules. 1915- New York. 
 
 W. J. Canada: The Hazards of Domestic Electrical Appli- 
 ances. Quarterly National Fire Protection Assoc., Octo- 
 ber, 1917- 
 
I2O 
 
 Chester H. Thordardson : The Toy Transformer and its 
 Hazards. Quarterly National Fire Protection Assoc. 
 October, 1917. 
 
 Underwriters Laboratories: Electrical Data, March, 1916. 
 February and July, 1917, Chicago. 
 
 National Board of Fire Underwriters: Storage and Handling 
 of Nitrocellulose Motion Picture Films, as recommended 
 by the National Fire Protection Assoc., 1915, Boston. 
 
 F. A. Talbot : Moving Pictures : How they are made and 
 worked. 1912. J. B. Lippincott Co., Phila. 
 
DEPT. 
 
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