QUESTIONS AND ANSWERS ON THE NATIONAL ELECTRICAL CODE Published by the McGraw-Hill Book Company New York >Succes*ons to theBookDepariments of the McQraw Publishing Company Hill Publishing Company Publishers of Books for- Electrical World The Engineering and Mining Journal Engineering Record American Machinist Electric Raihvay Journal Coal Age Metallurgical and Chemical Engineering Power QUESTIONS AND ANSWERS ON THE NATIONAL ELECTRICAL CODE A KEY AND INDEX TO THE OFFICIAL CODE BY T. S. McLOUGHLIN FIHST EDITION SECOND IMPRESSION CORRECTED McGRAW-HILL BOOK COMPANY 239 WEST 39TH STREET, NEW YORK 6 BOUVERIE STREET, LONDON, E. C. 1912 Library COPYRIGHT, 1912, BY THE BOOK COMPANY THE. MAPLE. PKESS. YORK- PA PREFACE This is a key and index to the National Electrical Code, and attempts to classify and interpret the requirements of this Code in a manner to make the information more easily accessible and more readily understood. It recognizes the Code as the established authority, and undertakes to explain its method, purpose and influence. Eight sections cover the various classes of electrical fire risks. They are entirely distinct from one another, so that the reader interested in Electric Railways, for example, will find his subject assembled complete under Section Seven. Section 9 completes the enumeration of fire prevention precautions, with tables and specifications of materials. It contains the most important of the Code tables, includ- ing Table I, Allowable Capacity of Wires, and others fre- quently used. Tables 10 to 18 are original in form, and were compiled expressly for this book, By the employment of the question and answer form, with full face side headings in the language of everyday practice, it is hoped that the valuable information of the Code is made available for quick reference, and in a form that will leave no doubt in the reader's mind of the proper course to pursue in given cases. Definite answers to the questions arising every day are given, and the exact por- tion of the Code apply 'ng to the statement is quoted as an authority in practically every instance. The Resuscitation C art as given, is the latest form from the committee in charge of this work. The methods given may also be used in cases of drowning, asphyxiation, etc., where breathing has apparently ceased. It is the author's belief that measures for the prevention of injury or death from electricity have not been given the considera- tion they deserve. NEW ORLEANS, LA. August, 1912. CONTENTS PAGE NATIONAL ELECTRICAL CODE AND ITS SPONSORS 1 LIFE HAZARD 5 EXPLANATORY 7 SECTION ONE GENERATORS IN GENERAL. (Questions 1-70) 9-20 Generators in general; Central station wiring; Central station conduit; Switchboards; Lightning arresters; Motors in general; Alternating work; Storage and primary batteries. SECTION TWO TRANSFORMERS. (Questions 71-83) 21-26 Transformers in general; Low-potential transformers; High-po- tential transformers; Extra high-potential transformers; Low voltage transformers; Grounding. SECTION THREE OUTSIDE WORK. (Questions 84-136) 27-38 In general; Grounding in general; Wires conducted; High ten- sion pole line; Underground conductors. SECTION FOUR SIGNALLING SYSTEMS. (Questions 137-183) 39-48 Wiring in general; Outside wires; Pole lines; Wires in Cables; Wires supplying current to apparatus; Protectors and instru- ments; All other systems except telegraph instrument circuits; Reactive coils and condensers; Ground wires in general; Wire- less telegraph apparatus. SECTION FIVE Questions 184-215 49-54 Arc lamps in general; Constant current systems; Incandescent lamps in series. SECTION SIX IDE WORK. (Questions 216-770) 55-137 Wiring in general; Knob and tube work, all kinds; Protection of wires from mechanical injury; Exposed knob and tube work; Knob and tube concealed; Non-metallic flexible tubing; Wooden vii 254484 viii TABLE OF CONTENTS PAGE moulding work; Metallic protective systems in general; Interior conduits, all kinds; Lined metal conduit; Armored cables; Grounding armored cables; Metal mouldings; Grounding metal moulding; Regulators, resistance boxes, rheostats, auto- starters; Auto starters; Switches; Circuit breakers; Fuses; Rosettes; Cabinets; Panel boards; Theaters and moving picture shows; Outline lighting; Electric signs; Decorative lighting systems; Electric heaters; Mercury vapor lamps; Fixtures; Sockets; Flex cord; Electric cranes. SECTION SEVEN ELECTRIC RAILWAY SYSTEMS. (Questions 771-868) 139-152 SECTION EIGHT MARINE WORK. (Questions 869-910) 153-162 SECTION NINE NATIONAL CODE REQUIREMENTS ON WIRE AND MATERIAL. (Tables 1-31) 163-210 Number of wires in rigid conduit, Table 32; Rulas for resusci- tation from electric shock. INDEX . .211 THE NATIONAL ELECTRICAL CODE AND ITS SPONSORS The National Electrical Code is a set of rules and require- ments governing such electrical wiring and apparatus as the Insurance Companies believe affect their fire risks. It is the standard authority in the whole United States and Can- ada and South American countries. Records show that the greatest fire losses ever paid by the insurance companies for authenticated "electric fires" resulted where it was disregarded. Despite a popular and convenient error, however, it does not ensure a good job from the user's standpoint. The Code addresses itself first, last and all the time to the fire risks; makes recommendations on the life risk; but is not officially concerned at all with economy, convenience, correct illumination or the ordinary every-day reliability of the work, except incidentally. Wiring may be far too small for bright light, and yet fully meet Code requirements. Designers and supervisors who use the National Electrical Code and its inspection systems as a free engineering bureau that will serve all purposes, are therefore sadly abusing their clients' confidence. Short-sighted central stations, passively permitting their lines to be loaded up with in- stallations too small for present and future need, although approved under the Code, sooner or later regret their inactivity. Revised editions of the Code have been appearing every two years in about the month of December, since the first issue in 1897. The revisions are made by an electrical committee of the National Fire Protection Association, after being chosen from a large number which are usually read and discussed at a biennial open meeting held in New York City. This usually takes place in March and is largely attended by interested electrical men of all kinds. This committee is responsible for the technical composition of the Code. The revisions are slowly and cautiously made. The address of the secretary of the committee is 141 Milk Street, Boston, Massachusetts. It has a total of 22 members. 2 QUESTIONS AND ANSWERS ON THE I^s membership 'is composed of five official representa- tives from the following: American Institute of Electrical Engineers; National Electrical Contractors Association; National Electric Light Association, chiefly Central Station men; American Street Railway Association, Electrical Engineer of the Municipal Department of Electricity, New York City; and 17 affiliated or kindred insurance organizations, among whom are the Underwriters' Labo- ratories; the National Board of Fire Underwriters; the National Electrical Inspectors Association, and the Western Association of Electrical Inspectors, both chiefly insurance inspectors. The Canadian Fire Underwriters Association of Montreal, Canada; one from Chicago, Illinois; one from the Fire Prevention Bureau, New Orleans, one from the South Eastern Underwriters Association, Atlanta, Georgia; one at Syracuse, New York; And the remaining eight are from New York, Boston, and Philadelphia insurance organizations. The Associated Factory Mutual Fire Insurance Companies, 31 Milk Street, Boston, issues its own form of the Code and its own List of Approved Fittings. Interpreters of the Code throughout the country are partially relieved from the exhaustive and sometimes incon- venient tests desirable upon insulated wire, apparatus, and devices, by the incorporated organization known as the Underwriters Laboratories, 207 East Ohio Street, Chicago, Illinois. It has representatives in all the principal cities of the United States and semi-annually issues a list of its approvals, obtainable free on application by those inter- ested. It makes a charge for its examination and tests necessary before approval is issued. These charges also can be had on application. It announces that it is not in business for profit and that its chief financial support is received from the National Board of Fire Underwriters, which directs it. The object is declared as follows: " To bring to the user the one best obtainable opinion on the merits or demerits of appliances in respect to the fire hazard." Its great importance to the electrical world at large lies in the fact that it is recognized by the great majority of insurance interpreters of the Code as the only official approval available. Practically all the standards OFFICIAL NATIONAL ELECTRICAL CODE 3 for general use are established through its approvals. An important and recent accomplishment, made with the co- operation of the best known wire manufacturers, was the establishment of a needed new standard for rubber-covered wire, which must, under 1911 specifications, have at least 20 per cent, of real rubber or equal in its insulating compound. The National Board of Fire Underwriters, 137 William Street, New York City, is the supreme and parent body of the insurance world. Its members are high officials of leading insurance companies and it keeps a benign and fatherly eye upon insurance risks as a whole throughout the United States. It sends out a corps of its engineers to cities and upon their reports conclusions are reached rating them as first, second or third class, etc. Electrical fire hazard is one of the items of this rating. The National Board officially endorses the code and is the finality in the insurance family of National Board, Under- writers Laboratories, National Fire Protection Association, "and their sisters and their cousins and their aunts." In the last analysis it is therefore responsible for the issuance of the Code, the approval of the kind of material it pre- scribes, and the fire risk character of the installations complying with the Code. The Code is a gift horse from the Board to the country. The enforcement of the Code is attained more by the natural wish of those concerned to secure safe work than any other consideration. Fire insurance policies contain a more or less uniform rider obligating the assured to comply with the Code, which the policy holder "signs up" along with all the other clauses. Insurance Companies at centers throughout the country usually group themselves in one form or another, and establish their own inspection department of electricity, to carry out the intention of the rider. In stubborn cases, violations of the Code are penalized, upon due consideration, by extra charges upon the assured, and in acutely dangerous places by cancellation of the policy. Charges are made in accordance with the degree of fire hazard incurred by the violation as advised by the Electrical Inspector, or as deemed expedient to meet the situation. Zealous insurance 4 OFFICIAL NATIONAL ELECTRICAL CODE electrical inspectors sometimes greatly disturb the tran- quility of an insurance agent. Mistaken interpretations by inspectors sometimes prove a hardship; but where skilled engineers or contractors have the work in hand, it is usually argued out to a correct conclusion. There are Code students in all branches of the business. Municipalities of New York, New Orleans, Chicago, Boston, Philadelphia and other cities and towns have ordinances adopting the Code and sometimes providing penalties by police power for enforcement. Such changes as are made in the Code by these municipalities usually make more positive the fine print suggestions and also the language of the rules; and recently include life hazards. Credit for the plan of the original National Code of 1897 and for the successful conduct of its affairs for many years, as far as it can be given to any one man amongst many, is generally conceded to belong to that veteran insurance man, Mr. C. M. Goddard, Boston, Massachusetts. LIFE HAZARD Failure of a lighting company to ground secondaries will soon become an invitation for litigation. Fortunately, progressive practice is ahead of discussion and many secondaries are now grounded throughout the United States, especially in centers. The highest conservative opinion obtainable is found in the official expression of the American Institute of Electrical Engineers, which has declared in favor of grounding up to 250 volts as being good engineering practice and highly desirable. Whenever a person turns on the current into any kind of an ordinary light, heat or power circuit, or portion of a circuit, he should be careful to see that he is in no manner in circuit with the earth. This may happen by touching a water pipe; by moisture or dripping water; touching a gas or radiator pipe and in several other ways. If he is in circuit with the earth, he should not touch any metal of the electric system, especially if an alternating current system fed by high tension primaries. Before cleaning such fixtures, the main switch or other cut off should be opened. Therefore all cellar lights, bath lights, and current con- suming appliances reached from a ground floor of earth or concrete should be controlled by the highest grade of switches with non-metallic insulating covers and insulated handles or buttons. If knife switches are used, the handles should be the only portion touched. The lights should never be turned on at ordinary metal shell sockets, while standing upon or in circuit with the earth. Porcelain or high insulation sockets should be used if no switches are available. Precautions of this kind are as important to guard life as many of the others so readily undertaken to prevent fire. Both dangers (i.e., of life and fire) are aggravated by the presence of the clumsy, unharmonious, and altogether unnecessary combination gas-electric fixtures. 5 EXPLANATORY The rule and paragraph of the rule in the National Elec- trical Code from which the answer is taken is specified in almost every answer, and is called a Reference throughout the book. The Code rule number at the end of the answer is imme- diately followed by the Code section letter (and number if any). Example: The question comes up on a theater or similar job "How many fuses may exit lights have between them and the service fuses? By referring to our index we find this question under Theater and Moving Picture Wiring: Exit lights, page 106 or under another heading if we happen to think of same instead, such as Fuses on exit lights in theater, page 106 We easily locate the question (No. 521) on page 106 and see that the answer is "Not more than one set and in cabinet. o8-t.)" If we wish to follow up the reference, which is Code rule 38- 1, we find the same information contained in the following: t. Auditorium. All wiring must be installed in approved conduit, metal moulding or armored cable. Exit lights must not have more than one set of fuses between same and service fuses. Exit lights and all lights in halls, corridors or any other part of the building used by audience, except the general auditorium lighting, must be fed independently of the stage lighting, and must be controlled only from the lobby or other convenient place in front of the house. All fuses must be enclosed in approved cabinets. Jobbers, Contractors, Purchasing Agents and others check- ing up stock may use the tabled form of Code requirements as presented in Section Nine to advantage. The essential differences between all kinds of flexible cords, for example, are at once apparent. 7 8 EXPLANATORY The author has created a classification or grouping re- sembling, but not in all cases the same as that used by the Code. Each of the nine sections carries its own explanation. As a ready reference book it may be used to advantage either in conjunction with the Code, or without it. The purpose of this question book is to endeavor to pre- sent typical and simple, every-day questions that arise in practical work, and, by answering them in a condensed form, help busy men to correct and quick interpretation of the Code to meet their present needs. The compiler believes it will be useful to architects, en- gineers, insurance men, salesmen, electrical workers, exami- nation boards, college students and the trade in general. He promises an improvement with each issue. Such engineering features or questions as appear to be within the range and scope of this work will appear in suc- ceeding editions. SECTION ONE GENERATORS, IN GENERAL Central Station Wiring. Central Station Conduit. Switchboards. Lightning Arresters. Generator Care and Attendance. MOTORS, IN GENERAL Alternating Current Work. Electric Fans. STORAGE AND PRIMARY BATTERIES SECTION ONE Section One includes Central Station, Dynamo, Motor and Storage Battery Room, Transformer Sub-stations ques- tions. References principally taken from Class "A." GENERATORS Under this heading will be found questions upon genera- tors of all classes, including Constant Current, Constant Potential, Low Potential (550 volts or less), High Potential (550 to 3500 volts inclusive) ; and Extra High Potential or over 3500 volts. IN GENERAL Following questions apply to all kinds of generators ex- cept where specifically indicated, as in No. 6. 1. Are Generators allowed in wet places? No. (i-a.) 2. Can a Generator be located in a gas house, powder factory, lint room of a textile mill, or similar place? No. (i-b.) 3. Give reading of name plate required by Code on gen- erators. Maker's name ; capacity in volts and amperes ; nor- mal speed in r.p.m. ( i-e.) Applies equally to motors, with ad- dition for varying speed alternators. See question No. 61. 4. Is slate, marble, porcelain or other approved material obligatory for terminal blocks? Yes. (i-f.) 5. When are properly filled hardwood, porcelain, or micanite bushings obligatory on generator frames for lead wires? Only when rubber bushings are subject to chemical action from oily vapors or other agencies, (i-g.) 6. Must Constant Potential Generators (Alternators and their exciters excepted) be protected from an excess of their own current, and how? Yes, by approved design circuit breakers, safety fuses or other similar devices, (i-d.) 11 12 QUESTIONS AND ANSWERS ON THE 7. Is single pole fuse or circuit-breaker sufficient on a two-wire direct-current generator. Yes ; provided it is not in series winding lead, (i-d.) 8. Where two generators are coupled in a three-wire direct current system, or where equalizers are used with 3 wire generators how must excess current protection be given? By a fuse or safety device in each outside lead from armature ; or by a double pole, double trip circuit -breaker used for each outside generator lead and equalizer con- nection, (i-d.) Following contemplated changes will perhaps be enforced in essentials in 1913 Code. "For two wire D. C. generators, single pole protection will be considered as satisfying the above rule, provided that the safety device is so located and connected, that the means for opening the same is actuated by the entire generator current, and the action thereof will completely open the generator circuit. If a generator, not electrically driven, has one terminal grounded, the safety device above mentioned must be placed in the grounded lead For three wire, direct current generators, compound or shunt wound, a safety device must be placed in each armature lead and so connected as to receive the entire current from the armature. Fuses will not be acceptable. The safety devices must consist of either 1 A double pole, double coil overload circuit breaker. 2 A four pole circuit breaker connected in the main and equalizer leads and tripped by means of two overload devices connected one in each armature lead. The safety devices above required must be so interlocked that no one pole can be opened without simultaneously disconnecting both sides of the armature from the system." 9. Must Generators of 550 volts or less be insulated from ground where possible? Yes. (i-c.) 10. When a standard filled wooden base frame (depended on for insulation) is omitted, and wooden floors are relied oh, what requirement is made for 550 volts or less? Floor must be kept filled and clean and dry. (i-c.) Note No. 1 : A heavy soaking application of linseed oil is acceptable as a filler under ordinary conditions. 1 1. When insulation of frame from ground is impracti- cable on 550 volts or less, what must be done? Written permission secured from Insurance Depart- ment having jurisdiction; and frame must be permanently and effectively grounded, (i-c.) 12. Must generators over 550 volts be grounded? Yes, permanently and effectively, (i-c.) OFFICIAL NATIONAL ELECTRICAL CODE 13 13. What is the safeguard suggested by the Code for high potential generators and machines of any kind? "If desired, high potential machines may be surrounded by an insulated platform, made of wood, mounted on insulating supports, and so arranged that a man must always stand upon it in order to touch any part of the machine." (Fine print note i-c.) Applies equally to motors. Central Station Wiring. Following questions apply to Central Station work of all kinds as designated in question or by heading. For require- ments for wiring conditions the same as in ordinary build- ings, see Section Six (6), principally Code Class "C" references, for example see No. 249. 14. What insulation is required on 550- to 3500-volt (or over) wires? Rubber covered. (2-b. and 44 -a). Read Tables 5, 6, 7, 8. 15. How must open work 550- to 3500-volt wires be run? Rigidly supported on glass or porcelain insulators, kept 8 in. apart, and i in. from surface wired over at least. (44-c.) Exceptions for motors. See 53. 1 6. In Central Station exposed circuits, what extra pro- tection is required for conductors? Must have heavy braided non-combustible covering, (Type letter S-BW wire covers this in dry places) [2-b.] Read No. 53. [See Table No. 2, Section 9.] 17. What is the type letter prefix for expressing a National Code standard lead-covered cable for interior work, any voltage? R.S.L.(so-j.) Example: zero to 600 volts expressed R.S.L.-6oo. zero to 1500 volts expressed R.S.L.-iS. zero to 2500 volts expressed R.S.L.-25. Prefix applies to both the taped and braided kinds. 1 3. What must be done where wires are bunched close together, as at switchboard? Must be provided with a non-combustible type outer cover. (2-b.) Note No. 2: Flame proof cable covering, or type S. B. W. wire acceptable. 14 QUESTIONS AND ANSWERS ON THE 19. Give rule for conductors from generators to switch- board, rheostats or other instruments. Must be in plain sight or readily accessible. They may be placed in a run -way in the brick or cement pier on which the generators stand. When such conductors are subject to moisture, lead -covered cable or iron conduit, with approved type wires, must be used. (2-a.) 20. Is it obligatory to strip back flame-proof covering required on switchboard cable to obtain the insulation dis- tance between conductors required? Yes. (2-b.) Note No. 3: For distance required, see table No. 29, Sec. 9. Central Station Conduit. 21. What special kind of conduit is required where groups of wires between rheostat contact plates and resist- ances are liable to mechanical injury or moisture? Approved lined conduit, or its equivalent. (4-c.) Note No. 4: Equivalent may be secured by use of unlined conduits reinforced with flexible tubing. 22. How must the unlined metal conduit where used on 550 to 3500 volts motors be installed? With approved outlet bushings and otherwise as re- quired for the highest grade of conduit work. (8-b.) Read question No. 53. Note No. 5: Pot heads and approved devices are acceptable instead of bushings. 23. How must conduit be bonded in motor leads? To metal casings of all fittings and apparatus on the inside of secondary or high tension circuit. (8-b.) Switchboards. 24. What is the limit upon approved enclosed fuses ac- cepted for protection of instruments or pilot lights on switchboards? Two amperes. (2-e,) 25. May busbars be of bare metal? Yes. (2-b.) 26. Are link fuses approved for switchboard work? Yes. (2 3 -c.) 27. Is wood acceptable for a switchboard? Yes, if rilled hardwood in skeleton form. (3-b.) OFFICIAL NATIONAL ELECTRICAL CODE 15 Note No. 6: "Skeleton form" is a form of wooden construc- tion where appliances are mounted on their own bases, of non- combustible material, and are applied to the switchboard by separate supports. 28. What extra requirements apply where wood is used for switchboards? Not only must appliances be separated from board by non-combustible, non -absorptive, insulative material, but wires and current -carrying parts must also be separated in similar manner. (3-b.) 29. Must switchboards be kept from moisture? Yes. ( 3 -d.) 30. How must the circuit connecting ground detectors, pilot lights and potential transformers on switchboards be run? With not less than No. 14 B. & S. wire; conductors must be protected by approved fuses ; must not carry over 660 Watts. (2-e.) 31. When may switchboards be placed against the wall with no space between? Only when wiring is entirely on face of board. (3-c.) 32. Is it compulsory to use ground detectors, except on permanently grounded wires, in a power plant? Yes. (7-a.) 33. May switchboards be built up to the ceiling? No, 3-ft. space, if possible, is demanded. (3-a.) 34. Can space back of board be used for storage pur- poses or filled with rubbish? No. ( 3 -a.) 35. If wired on back, how much clear space is obligatory between wall and current- carrying parts of apparatus on board? Eighteen inches. (3-c.) Lightning Arresters. 36. Give number and location of lightning arresters re- quired on power plant? Must be placed on each wire of every overhead cir- cuit connected with the station. Must be located in readily ac- cessible places away from combustible material, and as near as possible where wires enter building. (5 a and b.) 37. What does the term "readily accessible" in answer to question No. 36 mean? 16 QUESTIONS AND ANSWERS ON THE Easily, but not necessarily quickly reached. 38. How much insulation from ground or other conduc- tors must choke coils and attachments part of lightning arrester systems measure? At least equal to insulation resistance of other points of circuit in the station. (5-d.) 39. How much conductivity must ground connection with wire or metal have for lightning arrester? Equal to No. 6 B. & S. copper. (5-c.) 40. May ground wires be run inside iron pipes? No. (5-c.) 41. Must ground connections be in a straight line? Yes, as near as possible. (5-c.) 42. Can any lightning arrester not under list of approved fittings be used? No. (82-a.) Generator Care and Attendance. 43. Is a competent man required where generators are operated? Yes. (6-a.) 44. How must oily waste be kept? In approved waste can. (6-b.) 45. How often must it be removed? Daily. (6-b.) MOTORS IN GENERAL Note No. 7: Motors in general take practically the same classification and same questions apply as far as grounding and general protection is concerned as generators. Following questions apply to motors as indicated, also 22, 61 and made on 248 exception. 46. How must all motors be marked? Name plate with maker's name; capacity, volts ai amperes; and normal r.p.m. (8-h.) 47. How must single-phase motors be protected? By approved fuses, or at least on one side with cir- cuit breaker on the other. (23-f.) 48. What special protection is required for motor circuits? Unless subject to competent supervision or on main OFFICIAL NATIONAL ELECTRICAL CODE 17 switchboard, an approved fuse must be used, even if auto- matic overload circuit -breakers are installed. (23-f.) Note No. 8: Competent supervision must not be confused with an occasional inspection. 49. What protection is required for all motors and their resistance boxes? Plainly indicating "on or off" switch, properly in- stalled and cut-out with proper fuses. (8-c.) Exception: Electric crane motor. Also that automatic circuit -breakers instead of main switch and cut-out are acceptable, when of proper size, kind and adjustment. For alternating -current motors see also questions No. 57 to 62. 50. What type of motor is recommended in dusty places instead of wooden boxing enclosure. Enclosed. (8-f.) 51. Is a water-proof cover, such as oil or canvas, neces- sary when motor is not in use? Yes. Readily accessible dust-proof and ventilated enclosure such as one constructed with glass sides so that motor may always be visible, may be required by insurance department having jurisdiction. (8-f.) 52. Must base frames on less than 550 volt motors be permanently grounded? Must be thoroughly insulated from ground wherever feasible. Insurance Department having jurisdiction may require grounding if insulation is unpracticable. (8-a.) 53. What kind of protection must be given motor wiring, on high potential systems? Metal sheathed approved multiple conductors ; metal sheath permanently and effectively grounded; and con- duit construction complete except that at outlets approved outlet bushing shall be used instead of boxes. (8-b.) Read Nos. 22 and 23. 54. May ordinary adjustable speed motors, alternating or direct current, be started on a weakened field? No. (8-j.) 55. When may single-pole switches be used to control motors? When motors are i /4 h. p. and less and voltage does not exceed 300. (8-c.) Forbidden when used for : Service switches, out-door sign, 2 18 QUESTIONS AND ANSWERS ON THE 3 -wire neutral, (except in 2 -wire tap of not more than 660 watts.) [2 4 -c.] 56. What is the limit for a set of small motors grouped on one set of fuses in a circuit whose 3- or 2- wire maximum is 250 volts? Six amperes. (23-d.) Alternating Current Work. Read also reading matter over Table No. One, Sec. 9. 57. What portion of table of wire sizes, using rubber- covered wire, given under section nine (9) (and National Code Class "C") applies? Carrying capacities under Table "B" except when time element circuit breakers only are used. (23-6.) 58. How are sizes of wire determined for varying speed alternating-current motor leads or branch circuit? "The current used in determining the size of varying speed alternating current motor leads or branch circuits must be the percentage of the 30 -minute current rating of the motor as given for the several classifications of service in the following table : (8-b.) Classification of services Percentage of current rating of motor Operating valves, raising or lowering rolls, tool heads, etc. Hoists, rolls, ore and coal-handling machines. Freight elevators, shop cranes 200 180 160 Passenger elevators 140 Rolling tables pumps 120 59. When conductors would be over-fused for real starting current under Section 9, Table 1, [reference National Code Class "C, "] is an exception made, and how? Yes, wires must then be increased or adjusted to such a size as to be properly protected by the fuses against undue heating. (8-b.) Note No. 9: As a general rule, fuse and circuit opening devices must always be guaged to protect the wire first and the apparatus next from undue heating. (8-b.) 60. How much more than actual motor rating must an alternating current motor circuit or lead carry? OFFICIAL NATIONAL ELECTRICAL CODE 19 Minimum same as direct current 25 per cent. (8-b.) Note No. 10: In alternating current work, circuit may require guaging enormously above a full load rated current, for a start- ing load. Until types and standards are arranged by agree- ment or evolution, each case will be treated on its own merits. A reliable manufacturer's guarantee of the time duration of the starting current may be used as a basis of calculation in large installations. Or, actual experiment will reach a correct conclusion. 6 1. How must all varying (or variable) speed alternating- current motors be marked? With maximum current they can carry for 30 minutes, starting cold. Exceptions : Railway service motors. (8-h.) Electric Fans. 55 and 56 apply. 62. How must electric fan motors be insulated from the ceiling? By insulating hooks or substantial insulators inter- posed between fan and ceiling. (8-g.) 63. May flexible cord be used in wiring ceiling fans? Yes. (32-d.) Read also No. 673, Section 6, Division 5. 64. What kind of portable cord must be used for rotary fans? Type letters "P.O." also "P. Wp." and "P" according to conditions. See tables Section 9. STORAGE AND PRIMARY BATTERIES 65. Must the same regulations where light and power current is taken from secondary batteries or primary batteries be observed in producing the same results in voltage and amperage? Yes. (zo-a.) 66. What provision is required for a storage battery room? Must be thoroughly ventilated, (ic-b.) 67. What kind of wire must be used where acid fumes exist? Either weather proof or rubber insulated. (26- i and j.) 68. Is it necessary for secondary batteries to be mounted 20 OFFICIAL NATIONAL ELECTRICAL CODE on non-combustible, non-absorptive insulators, such as glass or thoroughly vitrified and glazed porcelain? Yes. (lo-d.) 69. Are metal connections, liable to corrosion, such as zinc, acceptable for cell connections in secondary batteries? No. (lo-e.) 70. How must wires be treated in storage or primary battery rooms where the acid fumes are apparent? Rigid support, rubber -covered wire or weather-proof. (26 i and j.) Section 6, Division i, Question 254, also applies. SECTION TWO TRANSFORMERS IN GENERAL LOW POTENTIAL TRANSFORMERS (Air Cooled.) HIGH POTENTIAL 550 TO 3500 VOLTS EXTRA HIGH POTENTIAL OVER 3500 VOLTS Tests In General. LOW VOLTAGE TRANSFORMERS GROUNDING 21 SECTION TWO TRANSFORMERS IN GENERAL Questions apply to transformers of all kinds and classes, except where specifically indicated by heading or other- wise. References are from Code Classes, "A," "B," "C" and "D." For questions upon secondary and primary wires read No. 84-104 inclusive; 107-136 inclusive, and Section No. 3, references Code Classes "B" and "C." Note No. 11: Only experienced men should undertake any work on transformers while current is on. Following questions apply to stationary transformers inside of buildings and attached to same. 71. Where must station transformers be installed? So that smoke from coils or oil boiling over can do no harm, (n-a.) 72. Must central and substation transformers be grounded? Yes, casings. Exception: Thoroughly insulated transformers used to supply current exclusively to switch- board instruments, (n-b.) 73. May transformers be installed in ordinary buildings without permission of the insurance department having jurisdiction? No. (i4-a.) And Rules 36 and 45. LOW POTENTIAL TRANSFORMERS Low Potential is Code classed (550 volts to 10 volts) either when First, primary current does not exceed 3500 volts, or Second, if primary wires 3500 volts to 5000 volts are installed either (a) Completely underground. Italics page 42 in Code. (b) According to Section No. 3, Code Class "B" for outside work, rule No. 13 requirements. Motor allowance 605 volts, (Italics, page 42 Code.) Following questions apply on transformers whose pri- maries or secondaries do not exceed 550 volts. Air Cooled. 23 24 QUESTIONS AND ANSWERS ON THE 74. May apparatus or fittings embodying air-cooled transformers be used without special examination and ap- proval? No. (36-a.) (Italics.) Note No. 12: special examination and approval is secured at a standard laboratory, per 36-a. italics. 75. Can transformers be placed inside ordinary buildings if the primaries or secondaries exceed 550 volts? No. . (36-b.) 76. How must transformers be mounted? At least a foot away from combustible material, or separated by wider marble or similar slab. (36-c.) HIGH POTENTIAL 550 TO 3500 VOLTS Questions apply to transformers supplying secondaries of over 550 volts and less than 3500 volts; more particularly to the transformers themselves. 77. How close to point at which primary wires enter enclosure must transformer be located? Close as possible. (45 -a.) 78. Is it necessary to place 550 to 3500 volt transformers in a fire-proof and locked enclosure? Yes. (45-b.) 79. Does the Code limit access to transformer room or enclosures to responsible parties? Yes. ( 4 5-b.) 80. Must transformer house be practically air- tight? Yes, except that it must be thoroughly ventilated to outside air if possible through chimney or flue. (45 -c.) EXTRA HIGH POTENTIAL OVER 3500 VOLTS Primary wires forbidden in all buildings except power and sub-stations. Secondaries, unless primaries are underground, or they otherwise comply with Rule No. 13 Code Class "B" for outside wiring, take high potential requirements. (47 -a and 48-a.) Read questions No. 118 to 135 inclusive. Tests in General. 8 1. What tests must transformers sustain? OFFICIAL NATIONAL ELECTRICAL CODE 25 "Must be constructed to comply with the following: 1. Shall be run for a sufficient time to reach a prac- tically constant temperature at full rated load, and at the end of that time a rise in temperature, as measured by the increase in resistance of the windings, shall not exceed 50 C. (122 F.). 2. When heated to normal full load operating tem- perature, the insulation of transformers shall withstand continuously for one minute a dif- ference of potential (alternating) between prim- ary and secondary coils and between the primary coils and the core according to the following table: Primary or Secondary Test Voltage Voltage Not exceeding 400 volts 1,500 From 400 to 550 volts 2,000 Over 550 volts To follow the standardization rules of the American Insti- tute of Electrical En- LOW VOLTAGE TRANSFORMERS Transformers fed by low potential circuits and delivering 10 volts or less. Should bear approval of standard Labor- atories to use. For primary wiring, questions inside ordinary building, see Section Six, [or Code Class " C," Inside Work.] For second- aries Section No. 4. [Signal System or Code Class "E,"] under which ordinary bell wiring is permitted. GROUNDING 82. Must high potential transformers be grounded or insulated from ground? Must either be permanently and effectively grounded or permanently and effectively insulated. (45 -c.) 83. Must transformers outside of buildings be grounded? 26 OFFICIAL NATIONAL ELECTRICAL CODE Following note from Code Class "B" (outside work) applies : "Where transformers are to be connected to high voltage circuits, it is necessary in many cases for best protection to life and property, that the secondary system be permanently grounded, and provision should be made for it when the trans- formers are built." 14. SECTION THREE OUTSIDE WORK IN GENERAL Grounding in General. Underground Conductors. Wires Conduited. High Tension (Constant Potential) Pole Lines Over 5000 Volts. In General on 5000 Volts Constant Potential. 27 SECTION THREE OUTSIDE WORK Light, Power and Heat. (For Signalling Systems, see Sec- tion 4, Code Class "E"). Unless indicated by heading or otherwise, questions ap- ply to all kinds of outside work. References principally from Code Class " B" Questions Nos. 84, 85, 88, 96, 97, and with Rule 12 are applicable to all systems and voltages. IN GENERAL 84. In splicing two pieces of wire, either inside or out- side wiring, what precautions, must be taken? Must be spliced or joined so as to be both mechanically and electrically secure without solder, as by making a West- ern Union joint. Joints must then be soldered and the whole covered with an insulation equal to that on the conductors. Approved splicing devices also acceptable. (i2-e.) 85. What kind of insulation is required for outside wir- ing up to service connection for electric lighting, heat or power? Both approved weather-proof and rubber-covered are acceptable. (i2-a.) 86. Where is rubber-covered wire obligatory on pole line services? From first support on building to cut-out or main block and service switch; and from main block up to a point on the outside of the building where the wires will be free from danger of contact with awnings, swinging signs, or building attachments or appurtenances. (i2-a.) 87. How far apart in order to prevent moisture must service wires not run in conduit be kept? Not less than i ft. apart. (i2-b.) 88. How should aerial service wires enter buildings? Through separate tubes, such as glass or porcelain, slanting upward toward inside of building for aerial work; properly extended iron conduit for enclosing wires of the service is approved on low potentials. (i2-f.) 29 30 QUESTIONS AND ANSWERS ON THE Note No. 13: A properly fitted iron conduit would have an approved service head which is secured by any device or arrangement whereby the service wires properly emerge through a bushing or heading. 89. Can service wires be allowed to come in contact with trees or any other substances? No. (i2-b.) 90. Where wires are to be attached to buildings by wooden blocks, upon which insulators are mounted, how must blocks be treated? Painted with at least two coats of water-proof paint. (12-b.) 91. How high must outside wiring be run over highest point of flat roof? At least 7 ft. (12-0.) 92. How high must they pass over ridged and pitched roofs? At least i ft. (i2-c.) 93. What kind of insulators must be used on wires ex- posed to the weather for lighting or power? Petticoat insulators of glass or porcelain; porcelain knobs or cleats or rubber hooks will not be approved. ( 1 2 -d. ) 94. When outside wires, such as services, are so sheltered that they are not exposed to the weather, what kind of in- sulators may be used? If low potential (maximum 550 volts) glass or porce- lain knobs separating wires at least i" in. from surface wired over may be used instead of petticoat insulators. Wires must be supported at least every 4 1/2 ft. (i2-d.) 95. How often must wires on exterior walls of buildings for light, heat or power be supported? Every 15 ft. minimum and oftener if liable to dis- turbance. (i2-d.) 96. Can electric light or power wires be placed on the same cross-arm with telephone or telegraph wires? NO. (12-g.) 97. What distance between line wires is required on telegraph, telephone or similar wires and electric light and power wires on the same pole? The distance between the two inside pins of each cross arm that carries an electric light or power wire under these circumstances must be not less than 26 in. (i2-g.) OFFICIAL NATIONAL ELECTRICAL CODE 31 98. Define service wires under the Code? Wires from street lines to building and into the main cut-out and service switch. (i2-a.) 99. Where outside wires are run in conduit, either from an underground system or combined with a pole line sys- tem, what kind of wire is obligatory for service wires? Rubber-covered. (i2-a.) Grounding in General. Read also 118, 119, 120. "Companies and Departments in charge of water works are urged to allow the attaching of ground wires to their piping systems, in the full confidence that the integrity of such piping systems will be in no way effected, whatever may be the voltage." National Fire Protection Committee recommendation, March 1912 Note No. 14: Alternating current secondary systems, grounds, as indicated by general terms of questions on this subject, involve considerations of life hazard to the greatest extent. 100. What condition is imperative under fine print note of Rule 15 whenever a low potential (550 volts or less) cir- cuit is grounded. That there is no passage of current over ground wire under normal conditions of service. (Fine print, Rule 15.) 101. May neutral wire be grounded on direct current three- wire systems when carried in underground work? Yes, if grounded at each distributing point through the box and at the central station, (is-a-2 and is-a-i.) 102. Is the ground connection with underground water and gas systems of the neutral wire on direct current three- wire system mandatory under fine print notes? Yes, ground connection must include all of available underground water and gas-pipe system. (i5-a-i.) Com- mittee's recommendations for 1913 Code low potential is mandatory. 163. Is it necessary to ground a direct current neutral on a three- wire system? Code declares neutral wire may be grounded and that such grounding must be permanent and effective at the cen- tral station, (is-a-i.) 104. May insurance department having jurisdiction re- quire grounding if they deem it necessary on alternating current secondary systems, and direct current neutrals? 32 QUESTIONS AND ANSWERS ON THE Yes, under the fine print notes, Rule 15 -a, following 3; and b-3. Committee recommendations for 1913 Code make alternating mandatory at less than 150 volts maxi- mum ground difference between ground and any point in the circuit. 105. When two-wire direct-current systems have no ac- cessible neutral point, shall they be grounded? No, under i5-a-3, fine print note. 106. What kind and size of wire is required upon grounds in a three- wire direct-current system at central stations? At central stations copper no less than neutral line wire size and elsewhere no smaller than No. 6 B. & S. 107. What size ground wire is required for secondaries of alternating current systems? No less than 6 B. & S. (is-d.) 1 08. How often must neutral wire be grounded in alter- nating current overhead systems? Every 500 ft. (i5-b-3) 109. On a three-phase system, how big must the ground wire be made? Carrying capacity equal to any one of the three mains. no. Where ground connection is inside any ordinary building, or the ground wire is inside of, or attached to, any building, must ground wire be of copper and rubber covered? Yes, Natl. Electrical Code standard. (Type letter R S for o to 600 volts.) (15 -c). in. When is protective covering, such as conduit, re- quired for ground wires? When exposed to mechanical injury. Reference, fine print note. (i5-e.) 112. What direction must ground wire take? As nearly straight as practicable. (15-6.) 113. Can staples be used for fastening ground wires on building? No. (is-c.) 114. Can ground wires be attached to building or pole by cleats or straps or on porcelain knobs? Yes. (i 5 -e.) 115. Is it necessary for ground connections for central OFFICIAL NATIONAL ELECTRICAL CODE 33 stations, transformer sub-stations and banks of trans- formers to be made permanent and effective, and in- clude the lead sheath of underground cables, as well as all available underground piping system? Yes. (i 5 -f.) 1 1 6. Can individual transformer in building services use the water-piping systems run in the buildings for ground connections? Yes. (is-g.) Caution. In cases of connections for electric light, heat or power to ground upon water-piping systems, a properly made grounding should be established on the street side of the meter. (i5-g.) 117. How must ground wires be run inside a building? Porcelain bushings through walls or partitions; in basements may be supported on porcelain insulators; other- wise run in approved moulding, or conduit. (i5-g.) 1 1 8. When three- wire, 110 volt, 220 volt or other second- ary service wires are grounded, where must ground be made? At neutral point, (is-b-i.) 119. Is the grounding on one side of a two- wire secondary service permitted? Yes, provided the difference between grounding point and any other point in the circuit will not exceed 2^0 volts. 120. Is grounding of alternating current secondaries required? Fine print note under rule 15 -a -3, declares ground- ing optional with insurance department having jurisdiction. Wires Conduited. 121. How must conduited services, etc., be treated? Wires in conduit must in general comply with Section No. 6, Inside work, Code Class "C" for unlined conduits. (i2-b.) (Where applicable.) 122. Where the situation or convenience requires the service to enter a cabinet, is it necessary for the conduit to enter the cabinet, as usual in conduit work? Yes. (28-b.) 123. How must conduit work exposed to the weather be protected? Must be water -proof. (i2-b.) 3 34 QUESTIONS AND ANSWERS ON THE Note No. 15: An approved device or arrangement by which water will be kept from entering pipes meets this requirement. High Tension (Constant Potential) Pole Lines Over 5000 Volts. Note No. 16: The Code is suggestive rather than mandatory its language on this subj of life, as well as fire hazard. . in its language on this subject. It involves grave questions , as well a The following fine print note, appearing under Rule 13, and opening the subject, is explanatory: Overhead lines of this class unless properly arranged may increase the fire loss from the following causes: 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 carried close to buildings, hamper the work of firemen in case of fire in the building. The object of these rules is so to direct this class of construction that no increase 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. It is fully understood that it is impossible to frame rules which will cover all conceivable cases that may arise in con- struction work of such an extended and varied nature, and it is advised that the Inspection Department having juris- diction be freely consulted as to any modification of the rules in particular cases. In General on Over 5000 Volts Constant Potential. 124. What precaution must be taken in arranging routes, on 5000 volts constant potential pole lines? Avoid exposure to contacts with other electric cir- cuits. (13 -a.) 125. Where lines come nearer to other pole lines, than a distance equal to the heighth of the taller pole lines; or where they must be carried on same poles with other wires, what must be done? Extra precautions to reduce break -down liability to a minimum, such as use of wires of ample mechanical strength, widely spaced cross-arms, short spans, double or extra heavy cross-arms, extra heavy pins, insulators and thoroughly supported poles. The high pressure companies' own signalling wires (such as telephones) are excepted in their own buildings. (13 -b and c.) 126. When on same poles with other wires, how high above them must high tension be located? At least 3 ft. (13-0.) OFFICIAL NATIONAL ELECTRICAL CODE 35 127. When crossing another line, what pole construction is required? Poles of heavy and substantial construction. (i3-d.) 128. Should end insulator guards be placed on cross- arms of 5000 volt wires carried above other lines? Yes, whenever feasible. (i3-d.) 129. If high-pressure lines cross below other lines, what construction should be followed? The wires of the upper line should be dead -ended at each end of the span to double -grooved, or to standard trans- position insulators, and the line completed by loops, (is-d.) 130. What forms of construction are then obligatory? One of the f ollowing three : "i. The height and length of the cross-over span may be made such that the shortest distance between the lower cross-arms of the upper line and any wire of the lower line will be greater than the length of the cross -over span, so that a wire breaking near one of the upper phis would not be long enough to reach any wire of the lower line. The high -pressure wires should prefer- ably be above the other wires. (i3-d-i.) "2. A joint pole may be erected at the crossing point, the high -pressure wires being supported on this pole at least 3 ft. above the other wires. Mechanical guards or supports must then be provided, so that in case of the breaking of any upper wire, it will be impossible for it to come into contact with any of the lower wires. (13- d-2.) "3. Whenever neither of the above methods is feasible, a screen of wire should be interposed between the lines at the cross-over. This screen should be supported on high tension insulators or grounded, and should be of such construction and strength as to prevent the upper wires from coming into contact with the lower ones." (13- d-3-) 131. What kind of suspension wires are suggested for use in preventing liability of contact between high-pressure wires located on poles above other wires? 36 QUESTIONS AND ANSWERS ON THE Same as those employed for suspending aerial tele- phone cables. They should be supported on high -potential insulators, have ample strength, and be carried for one strand on each side of the joint pole. Fine print of Rule 13 over No. 3. 132. When suspension wires are not used, how should guard wires be installed? Carried above and below the lower wires for one span on each side of the joint pole. Should be so spread as to catch and hold a falling high-pressure wire out of contact with lower wire. Fine print, Rule 13 over No. 3. 133. How should guard wires be supported or (alterna- tively) grounded? Supported on high -potential insulators or provided with grounding ample to carry off any possible current that may be delivered by high-pressure wires. Construction must be such that guard wires will not be destroyed by any possible arcing at point of contact. (13 d-2 fine print note.) 134. When neither suspension nor guard wires are feas- ible, what other method is advised? A screen of wire interposed between lines at the cross-over; screen treated as outlined in last two questions. Must further be of such construction and strength as to pre- vent top wires from falling on lower wires. (13 d-3.) 135. How high must 5000 volt lines or over be carried when near a building, and how far from same? When within 25 ft. of building at height not less than front cornice; this height must be greater than that of the cornice, as wires approach building in accordance with fol- lowing self -explanatory table. "Distance of wire Elevation of wire above from building. cornice of building. Feet. Feet, 25 20 2 15 4 10 6 5 8 2 1/2 9 !'It is evident that where the roof of the building continues nearly in line with the walls, as in Mansard roofs, the height and distance of the line must be reckoned from some part of the roof instead of from the cornice." (13--) Underground Conductors. 136. Give the Code requirements for underground con- ductors. OFFICIAL NATIONAL ELECTRICAL CODE 37 "a. Must be protected against moisture and mechanical injury where brought into a building, and all combustible material must be kept from the im- mediate vicinity. "b. Must not be so arranged as to shunt the current through a building around any catch -box. "c. Where underground service enters building through tubes, the tubes shall be tightly closed at outlets with asphaltum or other non-conductor, to pre- vent gases from entering the building through such channels. "d. No underground service from a subway to a build- ing shall supply more than one building except by permission from the Inspection Department having jurisdiction." (Rule 17.) SECTION FOUR SIGNALLING SYSTEMS WIRING IN GENERAL, APPLIANCES INCLUDED Outside Wires. Pole Lines. Wires in Cable. Wires supplying Current to Apparatus. Protectors and Instruments. ALL OTHER SYSTEMS EXCEPT TELEGRAPH Instrument circuits. Re -active coils and condensers. GROUND WIRES IN GENERAL WIRELESS TELEGRAPH APPARATUS Grounding wireless telegraph apparatus. 39 SECTION FOUR ALL SIGNALLING SYSTEMS Section Four includes signal systems in general. Wireless telegraph and its grounding are also included. References to questions are Code Class "E." Read 150, 96 and 97. (Wiring for telephone, telegraph, district messenger and call-bell circuits, fire and burglar alarms, and all other systems which are hazardous only because of their liability to become crossed with electric light, heat or power circuits.) Questions applying upon the low potential 110 to 220 volts or higher wiring for the wireless telegraph apparatus will be found under Section No. 6, [references Code Class PC."] Other requirements for Generators are treated by ques- tions in Section No. 1, [Code Class "A."] ^^ Where entire circuit is underground questions with ref- erences 85-b to m inclusive do not apply. Questions with references 85-j to p inclusive apply where apparatus will not carry 10 amperes indefinitely. ^e^Questions with references 85-f to i inclusive apply where apparatus will carry 10 amperes indefinitely. WIRING IN GENERAL, APPLIANCES INCLUDED 137. May two wires of a system enter building through one tube? Yes, promulgated in list of approved Electrical Fittings, April 1912. 138. Is it obligatory that the wiring in a building test free from ground? Yes. 139. Is an all-metallic circuit required for all signalling systems except telegraph? Yes. (85-f.) 140. Must single pole cut-outs designed for from 251 to 600 volts and containing fuses rating not over 10 amperes be provided for each wire of a circuit at entrance? Yes. (8 5 -g.) 41 42 QUESTIONS AND ANSWERS ON THE 141. What is the smallest sized copper wire allowed inside of a building on signalling system? Sixteen, B. & S. (85 -h.) 142. Are entrance cut-outs allowed in the vicinity of easily ignitable stuff or combustible surroundings of any kind? No. (85-g.) 143. What general questions apply to inside wiring for these systems? All on o to 600 volts, Section 6, Code Class "C" for insulation and support. (85 -h.) See Question No. 284 and 249. No. 141 modifies. Following applies to all systems whether wires from central office to building are overhead or underground. 144. When the entire system is inside of a building and is not in the vicinity of light or power wiring may staples be used? Yes. (8s-n.) Note No. 17: All -these inside wires may use staples. For the safest and most reliable work insulated staples or buttons are used. 145. How must wires bunched together in a vertical run within a building be protected? In non-combustible flexible tubing unless run in a fire -proof shaft with fire stops at each floor. (85-0.) 146. How may signal and electric light and power wires be run in the same shaft, and what special provision is made? One must run in tubing or separated from the other at least 2 in. (85-0.) 147. Can signal wires be run in the same tube with electric light or power wires? No. (85-0.) 148. How must 10 ampere capacity instruments be mounted? On non -combustible and non -absorptive, approved material. (85-!.) 149. How far apart must holes for bases carrying fuses be located or counter-sunk? To measure 1/2 in. space over circuit between head of screws and nearest live metal parts. (85-!.) OFFICIAL NATIONAL ELECTRICAL CODE 43 Outside Wires. Outside wires should only be run on roofs of buildings by special permission of Insurance Department having jurisdiction. (8s-a.) 150. When are telephone, telegraph, district messenger and call-bell circuits and fire and burglar alarms subject to regulation at all under the National Electrical Code? Whenever electric light, heat or power circuits are in the vicinity. (Rule 85, first italics.) 151. Can outside wires be placed on the same cross arm with electric light or power wires? No. (85-a.) 152. Should outside wires in signalling systems of any kind be permitted in the same duct, man-hole, or hand-hole or conduit systems with electric light or power wires? No. (85 -a.) 153. Do single man-holes or hand-holes separated into sections by means of partitions of brick or tile meet require- ments of 152? Yes. (8s-a.) Pole Lines. 154. Give distance required between two inside pins of each cross-arm where attached to pole bearing electric light or power wires? Minimum 24 hi. Code recommends signal wires be placed on lower cross-arms beneath such wires. (85-0.) 155. What kind of insulation is required for wires attached to wooden buildings and parts of buildings? Rubber -covered unless cabled. (85 -c.) 156. Are iron wires permitted to enter a building from pole line? No. (85-d.) 157. What kind of wire is required from pole lines to enter a building, and quote requirements? Approved rubber -covered copper from last outside supports or protectors (type letter R. S. is approved); drip loops; entrance through porcelain or approved tubes slanting upward from outside. (85-c-d-e.) Wires in Cable. 158. What special exceptions are made for all wires in cable? 44 QUESTIONS AND ANSWERS ON THE Need not be rubber-covered copper; and need not meet other requirements of previous Question. (85, second italics.) Wires Supplying Current to Apparatus. 159. How must such wires be insulated and supported? According to Question 284 dnd Section 6 or National Code requirements for Class "C" for inside wiring 0-600 volts. (85 -h.) 1 60. Must porcelain supports be so arranged from entrance of building to the protector that no contact will be made at any point up to the instrument? Yes. (8s-k.) Protectors and Instruments. 161. What does the term "protector" include? Fuses : current to ground shifting devices (lightning arrester,) magnetic cutouts and heat coils. (85-m-i.) 162. What kind of cut-out and fuse must be installed on a telegraph system circuit to protect each wire? Two thousand volts potential approved single pole cut-outs containing fuses not exceeding i ampere. (85-m-i.) 163. When 10 amperes, 251 to 600 volt fuses are installed in main entrance on telegraph systems, may the 2000 volt 1 ampere fuses be placed between switchboard and instru- ment? Yes; and instrument located as near switchboard as possible. (85-m-i.) ALL OTHER SYSTEMS, EXCEPT TELEGRAPH Instrument Circuits. 164. How must instruments be mounted? So that all live parts will be thoroughly insulated from wall on which protector is attached; and be properly mounted on non-combustible approved supports. (85-m-i.) 165. Is a 500 volt maximum lightning arrester required for protection? Yes. (85-m-2.) 1 66. How must its grounding be arranged? So that chance of accidental grounding is minimum. (8s-m-2.) OFFICIAL NATIONAL ELECTRICAL CODE 45 167. What fuse protection is required in protectors? Fuse to open circuit properly in case of cross with light or power wires. (85-01-2.) Note No. 18: Fuses should be provided to comply with requirements as indicated in Section Six, Division 3, Question No. 478, or under Code Class "C" for whatever voltage threatens or is in vicinity of protector. Code ad vises heat coils necessary in all circuits normally closed through magnet winding that cannot indefinitely carry at least 5 amperes current. (See 85-01-2.) A heat coil or sufficiently sensitive instrument which will operate before a sneak current can damage, the instrument pro- tector is guarding should also be included in protection. (85-m-2.) 168. How must fuses be placed? Protecting arrester and heat coils. (85-01-3.) 169. Is it required that protector terminals be marked "line," "instrument" and "ground"? Are abbreviations acceptable? Yes. (8s-m- 3 .) Reactive Coils and Condensers. 170. How must reactive coils be constructed and installed and treated? As sources of heat and mounted on non-combustible, approved material. (80 -a.) 171. How must condensers be treated? Like other apparatus operating with equivalent volt- age and current; must have non -combustible cases and sup- ports; be isolated from combustibles and treated as sources of heat. (8o-b.) GROUND WIRES IN GENERAL 172. What is the smallest size and kind of ground wire for protective devices permitted? Eighteen B. & S. rubber -covered for from o to 600 volts; with preservative compound permissibly omitted for from o to 600 volts. (85-!-! and 2.) 173. How must ground wires be run? Straight as possible to good permanent ground; con- nection to ground device shall be made as near as possible 46 QUESTIONS AND ANSWERS ON THE to earth; water or gas pipes are acceptable grounds, connec- tion in latter cases must be made between meter and street main. (85-1-3.) 174. Where obtainable, is it required that preference be given to water pipes over gas pipes? Yes. (85-1-3.) 175. Where a ground rod driven in the earth is used, how must grbund wire be attached? By an approved ground clamp fastened to a thor- oughly clean surface on rod or pipe; or pipe thoroughly cleaned and tinned with resin flux solder; ground wire tightly wrapped around and thoroughly soldered thereto. (85-1-30 176. May steam or hot- water pipes be used for a protector ground? No. (85-1-3.) WIRELESS TELEGRAPH APPARATUS Following questions apply to wireless telegraph appa- ratus, except where installed on shipboard. 177. Of what kind of wire must aerial conductors be made? No limitations specified by the Code. 178. What must be done in order to protect system from high-potential surges? Transformer inserted having a ratio giving 550 volts maximum or less or two condensers in series across line; connection between condensers permanently and effectively grounded. Condenser capacity should not be less than i hah* micro farad. (86 -e.) Grounding Wireless Telegraph Apparatus. 179. What is smallest size of conductors that may be used for a permanent ground? Four B. & S. (86-a.) 1 80. How should ground be made? By copper plate buried in ground connection or with usual copper wire hi direct line to water pipe street side of connections. (86-c.) 181. Is it necessary that grounds upon aerial conductors are cut off from all apparatus within the building? OFFICIAL NATIONAL ELECTRICAL CODE 47 Yes. (86-b.) 182. Give another method of acceptable grounding for aerial conductors? Short gap lightning arrester may be inserted in ground wire circuit. Gap on this arrester to be not over .015 in. between brass or copper plates; plates not less than 21/2 in. parallel to the gap, by 11/2 in. and with thickness not less than 1/8 in.; whole mounted on non-combustible, ap- proved insulating materials. (86-c.) 183. Wherever aerial conductor is grounded to water pipes or other satisfactory earthing, what size switch must be employed joining aerial to the ground connection? Not less than standard 100 ampere knife switch. (86-d.) SECTION FIVE ARC LAMPS IN GENERAL Multiple Incandescent Arcs CONSTANT CURRENT SYSTEMS (Principally Series Arcs) Incandescent Lamps in Series. 49 SECTION FIVE ARC LAMPS IN GENERAL Following questions apply to all kinds of arc lamps, ex- cept as specifically indicated otherwise, as in Question No. 195. References principally from Code Class "C," Constant Potential. 184. Are stops to prevent carbons from falling out in case clamps get loose required? Yes. (74-a.) 185. Is it necessary to insulate exposed parts? Yes. (74-b.) 1 86. How must arc light terminals be designed? So supply wire contact is not loosened by lamp mo- tion during trimming. (74-d.) 187. Is it necessary for spark arresters to close the top hole of the globe from the escape of carbon flakes? Yes. (75-a.) 188. Is a cut-out necessary for each individual lamp; or each series of lamps? Yes. (33-a.) 189. What size is required for branch conductors for arc lamps? Fifty per cent, excess normal current required for each lamp. (33-a.) 190. Must resistances and regulators for arc lamps be en- closed in non-combustible material? Yes. (33-b.) 191. Can incandescent lamps be used as resistances? No. (33-b.) 192. Are spark arresters required for arc lamps when in vicinity of inflammable materials? Yes. [33 -c.] 193. Is wire netting required around globe of series arc lamp in vicinity of inflammable material? Yes. (33 -c and 2i-c.) 194. How far above sidewalk must outside arcs be hung? Eight ft. (33-c.) 195. How must inside arc lamps be installed? 51 52 QUESTIONS AND ANSWERS ON THE Out of reach or protected from mechanical injury; when arranged for lowering and raising, if conductors are larger than 14 B. & S. shall be stranded. (33-d.) Multiple Incandescent Arcs. 196. Are multiple or incandescent arcs (generally fed by ordinary incandescent circuits) subject to the requirements for series arc lamp spark arresters? No, where they have tight inner globe. (21-0.) CONSTANT CURRENT SYSTEMS Principally Series Arcs. Following questions apply upon constant-current sys- tems unless otherwise specified or indicated. References principally taken from Code Class "C" (Inside Work), Constant Current Systems. Questions under Wiring in general, as applicable, Section No. 6, Code Class "C" also apply. Wire Table 1 for sizes of wire, Section No. 9, Reference Code Class "C," Rule 18, also governs. 197. What kind of wire must be used for series arcs on the inside of building? Rubber-covered. (20 -a.) 198. What kind of series arcs entrance or service switch must be used, and how installed? Double contact mounted on non-combustible base; free from moisture; and convenient of access for police or fireman. (20 -b.) 199. May wires for series arcs be concealed or encased? No, unless by requirement of Inspection Department having jurisdiction. (20 -c.) 200. How far apart must series arc light wires and cir- cuits be run except at points where they enter their appli- ances, such as lamps, cut-outs, etc.? Eight inches. (20 -d.) 201. Must arc light wires on side wall and other wires subject to mechanical injury be protected? Yes, see Question No. 279, Section 6, Methods (20 -e) equally applicable. 202. Must series arc lamps be kept isolated from in- flammable materials? OFFICIAL NATIONAL ELECTRICAL CODE 53 Yes. (2 1 -a.) 203. Are broken, cracked, or insecurely fastened globes acceptable? No. (2i-b.) 204. Is a wire netting around a series arc globe and approved spark arrester required? Yes (2i-c.) 205. What is the largest size mesh allowed in arc-lamp wire netting; is netting obligatory? One and one-fourth inches.; yes. (21-0.) Excep- tion : "Enclosed Arc" lamps with tight globes. (21 -c.) 206. Where exposed to flyings of easily inflammable materials, what substitution for spark arrester is required? Carbons completely enclosed in tight globes. (2i-c.) 207. How must arc lamps not hung from hanger boards be supported? Insulating supports other than their conductors must be used. (2i-d.) 208. How must switches on constant-current devices, such as series arc lights, operate? Automatically close main circuit and disconnect branch wires or branch arc when turned off. (65 -b.) 209. Are both hand and automatic shunted switches required for constant-current systems? Yes. (74-c.) 210. How must hanger boards be built? "a. Hanger -boards must be so constructed that all wires and current-carrying devices thereon will be exposed to view and thoroughly insulated by being mounted on a non- combustible, non-absorptive, insulating substance. All switches attached to the same must be so constructed that they shall be automatic in their action, cutting off both poles to the lamp, not stopping between points when started and preventing an arc between points under all circumstances." (73-a.) 211. May series lamps be attached to gas fixtures? No. (46 -b, also 22 -d.) Incandescent Lamps in Series. Christmas minatures ex- cepted, See Decorative Lighting. 212. Must automatic cut-out be provided for each lamp in a series circuit? Yes. (22-a.) 54 OFFICIAL NATIONAL ELECTRICAL CODE 213. How must incandescent lamps in series circuits be suspended? From a hanger board by rigid tube. (22-b.) 214. Are multiple series or series multiple systems approved? No. (22-0 and 46-a.) 2 15. May incandescent lamps in series circuits be attached to gas fixtures? No. (22-d.) SECTION SIX (INSIDE WORK) Light, Power and Heat. For Signalling Systems, see Section Four. (Code Class "E.") Section Six includes installation questions upon all classes of inside work. References principally from. Code Class "C" (Inside Work) and Code Class "D" (Fittings, Mate- rials and Details of Construction, for all systems and volt- ages). For tables and information on material and fittings, see Section Nine. Wiring in General. 55 SECTION SIX WIRING IN GENERAL Question 84, reference 15-c, applies. 216. What is the wire table giving allowable carrying capacity for rubber-covered wire and other insulation? See Table No. i, Section 9. 217. What type letter applies for National Code standard plain rubber-covered, low-potential (up to 550 volts with maximum allowance of 605 for motors) conductors? Type letter R. S. See also Table No. 5. 218. How much must the complete covering slow burn- ing wires measure? In accordance with Tables Nos. 2 and 3, Section 9. 219. Where is underwriter's wire (type letters S-B) par- ticularly acceptable? In hot dry places, as back of a large switchboard or wire tower. (5 2 -a, fine print note.) 220. What is the safe carrying capacity for insulated aluminum wire? Eighty-four per cent, of that given in the tables for copper wire with the same kind of insulation. (i8-a.) (See Table No. i, Section 9.) 221. How close must stranded conductors be computed? In stranded conductors, the sum of the circular mills of the individual wires must not be less than the total circu- lar mills of the conductor size required by more than 11/2 per cent. (49-a.) 222. Is it necessary in applying a stranded conductor to use all strands under the clamp? To within 11/2 per cent, of the actual circular mills required for the proper size of wire. (49-a.) Read 455. 223. What is the smallest size of wire allowed for interior wiring, fixture wire not included? No. 14 B. & S. (i6-a.) 57 58 QUESTIONS AND ANSWERS ON THE 224. Does the Code allow larger amperage on weather- proof and slow-burning wires than on rubber-covered? Yes. See Table No. i, Section 9. 225. Is a concession given for alternating current motor wiring under this table? Yes, see Table No. i-B, Section 9. 226. Can primary wires of over 3500 volts (extra high potential system) be brought into or over any buildings ex- cept power stations and sub-stations? No. (47 -a.); applies also outside work, Section 3. 227. How must secondary wires, whose immediate pri- maries are over 3500 volts, be installed, and is there any exception? Must be treated as extra high potential. Exception made whenever primary wires are installed entirely under- ground in city, town or village limits ; or in accordance with questions on over 5000 volts, Constant Potential, Section 3, Code Class "B." U8-a.) 228. Is tape on type letter R.S.L. lead-covered cable or wire acceptable instead of a braid? Yes, if it increases diameter over insulating wall as much as 1/64 in. (5o-j.) 229. On to 600 volt multiple conductors, is thickness of lead same as required for a single conductor, acceptable? Yes, in sizes of bunch conductors, the same diameter. (5o-j.) 230. What is the maximum wattage allowed in house and similar wiring for one fused branch circuit, two wires? Six hundred and sixty watts. Not applicable to grounded circuits of street railways systems. [23-d.] 231. How should wires be bushed through brick walls? By non -combustible, non -absorptive, insulative tubes, continuous through holes. Water -proofed iron pipes or con- duits bushing hole as a container for short length tubes thus affording continuity of protection for wires is acceptable. 232. Are holes and open spaces at outlets allowed, such as caused by broken plastering? No. (26-u and 28-d.) 233. Where change in size of wire is made, as at a branch circuit, is a cut-out with proper fuse required? OFFICIAL NATIONAL ELECTRICAL CODE 59 Yes, unless cut-out fuse already in larger wire will protect smaller. (23 -b.) Note No. 19: Fuses must protect wires as the first con- sideration and be guaged accordingly. 234. What does the term "nearest accessible place" as applied to the required location of main cut-outs mean? Nearest practical point for the cut-outs to be located for fusing or attention, and the nearest practical point for the service wires to enter the building. In underground service this would often be within easy hand reach from floor. In overhead, conditions might justify approval where the aid of an ordinary step ladder is needed. For an unprotected fuse block a range of from 6 to 12 ft. from floor is customarily permitted, and selected. 235. What does the term "nearest readily accessible place" mean as required for the location of all service switches? Nearest practical place where switch can be located within about 5 ft. from floor, or within quick hand reach. A residence second story is an approved location. 236. What is meant by the term "readily accessible" in the requirement that armored cable and other grounding connections for metallic protective systems must be exposed to view or readily accessible? Must be easily, but not necessarily quickly reached. A connection in an ordinary house cellar to an exposed water pipe is an example. 237. When may fuses be omitted in the neutral of three- wire direct-current or single-phase systems, at the main block? When the neutral is properly grounded on the outside. (23-b.) Read Section 3, Grounding in general. 238. When fuses are omitted in the neutral of inside wiring (grounded services outside) at the main block, may they be omitted in all the two- wire house circuits taken off the three- wire house mains? No. (23-d.) 239. May three- wire circuits be continued or tapped from a grounded (outside) system of house mains for use as lamp circuits, when neutral is solid? No. (23-d.) 60 QUESTIONS AND ANSWERS ON THE 240. What kind of circuits are required for lamps, or other 660 watt house circuits, when taken off grounded (services outside) three- wire house mains? Two-wire (if fuses are omitted in neutral). (23-d.) 241. When a non-grounded, three-wire system is used, oi less than 250 volts between outside wires, for house wiring, may three-wire circuits be taken off the house mains for; supplying lamps? Yes, but limitation of 660 watts still applies for each side of such circuit. (23-d.) 242. May tungsten lamps, carbon lamps, and fan motors be used on the same house circuit of not exceeding 250 volts? Yes, provided the limit of 660 watts is not exceeded. (23-d.) 243. May an electric meter be installed before a main switch or fuse? No. (24-a.) 244. When voltage is over 250 between two outside wires of a system, how must both wires of a branch or tap lamp circuit be protected? By proper fuses. (23-d.) 245. If fuses are provided for three-wire circuits at the juncture with three- wire fused house mains on a grounded neutral (outside) system; and electric lamps or other houst circuit appliances are attached to it to a maximum of 66( watts, total, does this comply with Code? Yes, if maximum voltage between outside wires ij not over 250 volts. (23-d.) 246. May circuits be three-wire from either a groundec neutral (outside) or a non-grounded neutral where ove: 250 volts is used between the two outside wires? No. (23-d.) Note No. 20: Distinguishing terms: A house main has n current-consuming device, such as a lamp, attached, j circuit is attached to a main, and is usually, but not neces sarily, a smaller wire, and directly supplies the lamps, sma motors, etc. 247. In dry places, when it is impossible or impractlca to place the whole of a circuit on the insulating supports what construction must be followed? Metal Conduit or approved armored cable. (26 and t.) Read 302. OFFICIAL NATIONAL ELECTRICAL CODE 61 248. What is the limit for fuses in branch cut-outs, and what exception is made? 55 volts or less 12 amperes Over 55 but less than 125 volts 6 amperes 125 to 250 volts 3 amperes (23-d.) Exception: Small motors grouped under single set fuses are allowed 6 amperes, voltage not over 250. Limited to 1320 watts per circurt load. (39-h and 83-g.) Read 615 and 620. SECTION SIX DIVISION ONE KNOB AND TUBE WORK ALL KINDS Protection of Wires from Mechanical Injury. Exposed Knob and Tube Work. Knob and Tube Work Concealed. Non-metallic Flexible Tubing. Wooden Moulding Work. 63 DIVISION ONE Treating of knob and tube work of all kinds ; knob work open; knob work concealed. Also of non-metallic flexible tubing, and wooden moulding. Following questions unless specifically designated by head- ing or otherwise, apply in general on low potential 10 to 550 volts. Motors allowed 10 per cent, or 605 volts, at gener- ator or transformer. Questions with References 16 to 19 inclusive apply all systems and voltages. Constant-current system questions are under Section No. 5. Both knob and tube work ex- posed and knob and tube work concealed rely on air-gap insulation in addition to the wire insulation (except at supports and unavoidable contacts where porcelain tubes are generally used). Correctly installed in suitable places they have proven safe and durable. Unlike the metallic protective systems, this class of work never has the cover- ings over the wires grounded. In this it is a non-grounded system. KNOB AND TUBE WORK ALL KINDS - Note No. 21: Knob and tube work in so-called open or exposed wiring, and concealed knob and tube work all rely upon air-gap insulation for durability and protection against grounding, except at the supports, usually of porcelain. This system seldom deteriorates. Grounds are required on inside work of this kind only where a regular conduit system appears, making a "mixed" job. Following apply to both open and concealed knob and tube work, and are principally installation questions. Ref- erences Code Class "C" (Inside Work) and Code Class "D" (Fittings) . 249. How far apart and how far from surface wired over must wires be kept in? 5 65 66 QUESTIONS AND ANSWERS ON THE 1. Open work, dry places. 2. Open work damp places. 3. Concealed work. In accordance with the following : Distance Distance Distance Code I Voltage from between between rule and! surface wires supports section 1 Open work 0-300 V 2| *f 26-h. 1 dry places 301-550 \" 4" 44' 26-h. 1 1 Open work 0-300 V w 44' 26-j. j damp places I 301-550 I" 4" 4*' 26-j. 1 Concealed work 0-300 1" 5" 41" 26-r. I 1 Distance between supports to be shortened for rigid support if necessary. (26-h and r). Fine print note advises this rule will not be interpreted to forbid placing of neutrals of three -wire systems in the center of a three -wire cleat where difference between out- side wires is not over 300 volts, and that the outside wires are separated 2 1/2 in. (62-6.) See also No. 284. Knobs must always hold wire i" from surface. (64-6.) 250. Are wires run near water tank or pipe considered subject to moisture? Yes. (26-f.) 251. Can wires be run on knobs or upper edges of joist in unfinished attics? No. ( 2 6-f.) 252. How must conduit or cable be installed on a mi: knob and tube and cable or conduit job? Just as for a complete and continuous conduit 53 properly begun and terminated. (26-t.) Note No. 22: A mixed knob and tube job where condt must be grounded should not be confused with a mere protectu from mechanical injury where the protection need not tx grounded. OFFICIAL NATIONAL ELECTRICAL CODE 67 253. How must wires be kept away from contact with gas or water pipes? By permanent separation, with continuous and firmly fixed non-conductor where crossing, such as porcelain tube fixed at both ends with friction tape to wire ; or by approved device for same. (i6-e.) 254. What insulation must be used inside of buildings on wire subject to action of corrosive vapors? Either rubber-covered or weather-proof. (26-1.) 255. What insulation should be used for wires subject to unusual heat? Slow -burning. (52 -a, fine print note.) 256. Under what conditions may slow-burning wire be ^ used inside of buildings under ordinary circumstances? When not subject to moisture and run open in cleats and knobs. (26-g.) 257. Must stranded wires be soldered? Yes, except in flexible cords, must be soldered before being fastened under clamps and binding screws and terminal lugs. (i6-c.) Exception: Where approved solderless ter- minal connection is used. 258. Is it obligatory to keep wires from contact with walls, floors or timbers? Yes. (i6-d and 26-r.) 259. In wet places, is an air space between wires and pipes in both concealed and open work obligatory? r 260. How must conductors be run to avoid contact with pipes they may cross in both concealed and open work? It is recommended over rather than under pipes sub- ject to moisture. (i6-f.) 261. Are approved bushings or flexible non-metallic tub- ing necessary over wires entering cabinet and how must they be installed? Yes, they must tightly fit entrance holes hi cabinets and be well secured in place. (26-a.) 262. Must wires in entering completely fill up entrance holes in bushings? Yes. (26-a.) 263. How must wires in general be mounted? 68 QUESTIONS AND ANSWERS ON THE Non-combustible, non-absorptive insulators, such as glass or porcelain. (i6-b.) 264. How must porcelain cleats grip the wires? Firmly without injury to the covering. (62 -a.) 265. What kind of split knob or single wire cleats are required for wire larger than No. 4 ? Must have two supporting screw holes. (64-b.) 266. Can solid knobs be used on wire sizes smaller than No. 8? No. Exception per 283. (i6-b.) 267. Are solid knobs of proper size allowed for support of wires No. 8 or larger? Yes. (i6-b.) 268. What kind of tie wires are required? Must have insulation equal to the wires they fasten. (i6-b.) 269. Are nails fitted with leather heads or proper washers allowed for split or wire gripping knobs or cleats? Yes. (i6-b.) 270. How long must a nail for a knob or cleat be made? Must project into the wood work not less than hah* length of the knob; and fully thickness of a cleat. (i6-b.) 271. How much surface separation must at all times be maintained between screws or nails for knobs and the con- ductors? At least 1/4 in. (64-b.) 272. Is it obligatory that solid knobs be smooth grooved for containing a wire? Yes. (6 4 -a.) 273. Can wires for electric light, heat or power for con- cealed or open work be fastened or attached by staples? No. (26-b.) 274. How must approved split knobs be made? In two pieces, viz. : a base and a cap arranged to hold wire firmly in place without injury to covering. (64-a.) Protection of Wires from Mechanical Injury. 275. Is it obligatory to protect wires where subject to mechanical injury? Yes. ( 2 6-e.) 276. What kinds of protection are approved for the installation of electric conductors in elevator shafts? OFFICIAL NATIONAL ELECTRICAL CODE 69 Approved lined or unlined metal conduits, flexible metallic conduits or armored cables, all properly installed. (i6-g.) 277. In crossing floor timbers in cellars or in similar conditions, how must open work wires be installed? Attached by insulating supports, such as glass or porcelain, to underside of a wooden strip not less than 1/2 in. thick and 3 in. in width; or guard strips each side of and close to wire are acceptable if strips are at least 7/8 in. thick and as high as the insulator they protect from mechan- ical injury. (26-6.) 278. Is it obligatory for all side-wall protection to extend 5 ft. above the floor? Yes. (26-6.) In metal moulding systems in resi- dences, offices, and similar locations, this is sometimes reduced by consent, to 3 in. above floor. (2p-b.) Note No. 23: Npn-metallic flexible tubing or metal moulding is not applicable as a sufficient protector of wires from mechanical injury. (26-6 and 2Q-b.) Protection Against Mechanical Injury. 279. Describe approved methods of protecting exposed work on side walls from mechanical injury. Method No. i: Box wires leaving an air space of I in. around the conductors, boxing closed at the top; wires come through bushed holes. (26-6.) Suggestion : Bushing should be rigid. Method No. 2 : Install metal unlined conduit or pipe, reinforcing insulation of each of the circuit wires with an approved flexible tubing extending continuously from first support below to first support above the conduit or pipe. (26-e.) Method No. 3 : Continuous single lined metal con- duit terminated with a lined and bushed conduit box at each end. Continue ordinary circuit wires through the conduit. No extra braided wire is required. (26-6.) Method No. 4 : Same as No. 3, using unlined conduit and boxes and the extra braided conduit wire, type R-D (see Section 9) within the conduit system ; if circuit wires are of the ordinary open work type R-S, make a tap in the box from the ordinary wires to the extra braided conduit wires. (26-6, -28) (e and f excepted) also apply here. 70 QUESTIONS AND ANSWERS ON THE Note No. 24: Approved fittings may be used instead of boxes; They should have ample room for joints. Flexible steel conduit may be used instead of rigid conduit or pipe, in Methods 2 and 4. 280. Is it necessary to ground short section of iron pipe or conduit used in side-wall protection? No. (28-f.) 281. Can twin wires be used in knob and tube work, either concealed or open? No, use of twin wires is limited to conduit work or where flexible conductors are necessary. (26-d.) Exposed Knob and Tube Work. Following questions apply to so-called "open knob and cleat work" exposed to view. 282. What kind of insulations must be used? Approved rubber; slow -burning weather-proof, or slow-burning insulation, i.e., type letters R-S, S. B. W., and S.-B. (26-g.) 283. How must wires at ends of runs be supported? By solid porcelain or glass knobs; or strain insu- lators. (i6-b.) 284. How far from surface wired over and how far apart must porcelain or other supports keep the wires in dry places? In accordance with the following : Voltage Distance from Distance between Distance apart surface wires to 300 1/2 in. 2 1/2 in. 4 1/2 ft. 301 to 550 1 in. 4 in. (26-h) Read 249. 285. When wires are liable to disturbance, what must be done to secure rigid support under all conditions? Wires must be supported oftener than the required 41/2 ft., and as frequently as necessary to secure results. (26-h.) 286. In buildings of mill construction, when mains are not less than No. 8 B. & S. and are not liable to disturbance, how far apart can they be run and what special privilege is given? May be separated about 6 in.; run from timber to timber, and be supported at each timber only; not breaking around. (26-h.) 287. How close must the last support of a line be placed to the final socket rosette or similar outlet? OFFICIAL NATIONAL ELECTRICAL CODE 71 Twelve inches (26-h.) 288. What is the distance required between electric light and bell and signal wires running parallel? Not less than 2 in. unless separated by a firmly fixed non-conductor continuous and creating a permanent separa- tion. Insulation on the wire is not acceptable as a sufficient compliance with this rule. (i6-e.) Applies all systems and voltages. Inside work. Knob and Tube Work Concealed. Following questions apply to so-called concealed knob and tube work, 300 volts maximum. 289. Will flexible tubing over wires be accepted instead of bushings where wires enter a cabinet? Yes, if extending from last porcelain support into the cabinet. (26-a.). 290. Can wires be laid in plaster, cement or similar finish? No. (26-b.) 291. Can wires be fished in concealed work or otherwise any great distance? No. (26-0.) 292. What special provision is made for the fishing of wires? Only permitted where conditions are such that in- spector having jurisdiction can satisfy himself of its necessity and that rules have been complied with. (26-c.) 293. What kind of insulation is required for concealed knob and tube work? Approved rubber-covered. (26-q.) 294. How must wires be run for concealed knob and tube work? On non - combustible, non - absorptive insulators. (26-r.) Exception per 292, 247 and 302. 295. How far apart must wires be kept? Five niches minimum. (26-r.) 296. How far from surface wired over must concealed work insulators keep the wires? One inch. (26-r.) 297. Are wires separated by timbers or studding and run singly approved? Yes. (26-r.) 72 QUESTIONS AND ANSWERS ON THE 298. Must separation from walls, floors, timbers and other woodwork in the building be preserved? Yes. (26-r.) 299. How must wires passing through cross timbers of; plastered partition in concealed work be protected? By additional tube extending at least 4 in. above tim- ber. (26-r.) 300. In concealed work, how must outlet box or plate be installed? Flushed with finished surface. (28-d.) Non-metallic Flexible Tubing. Note No. 25: Non-metallic flexible tubing is applied as an extra protective covering rather than a conduit. 301. Where must flexible tubing be used in concealed knob and tube work? Must be used at points where wires come together, such as knob and tube outlets, and at distributing centers when 5 in. separation cannot be maintained. (26-r.) 302. May continuous lengths of flexible tubing be used as a part of a concealed knob and tube system where wires are to be fished? Yes, when the wires cannot be placed on porcelain supports or knobs without damage (as in old buildings) ; lim- ited to 300 volts ; must not be exposed to moisture. (26-5.) 303. In dry places, is flexible non-metallic tubing ap- proved for fishwork in a concealed knob and tube system? Yes, on maximum 300 volts if impracticable to use the insulating supports. (26-5.) 304. How far must flexible tubing project at combina- tion fixture outlets? Flush with outer end of gas cap. (26-u.) 305. How must flexible tubing be marked? With distinctive manufacturer's marking entire length of tube. (63-!.) 306. Are tubings whose lining is removable in continuous lengths of over 3 ft. approved? No. (63-d.) 307. Is a moisture-proof compound necessary for the out- side cover of a flexible tubing? Yes. (63 -e.) 308. When kinked or flattened or straightened out, is a OFFICIAL NATIONAL ELECTRICAL CODE 73 flexible tubing, which closes sufficiently to prevent inser- tion of the wire, approved? No. (6 3 -h.) 309. How tough and tenacious must tubing be made? To withstand severe tension without injury. (63 -g.) Wooden Moulding Work. Limited to 300 volts or less. 310. Can any ordinary approved rubber-covered wire, Type R. S., suitable for knob and tube work, be used in wooden moulding? Yes. (26-k.) 311. Are joints in wires or taps from wire to wire direct allowed on wires in moulding of any kind? No, approved devices, such as "moulding branch blocks" must be used for taps or branching connections. (26-k.) 312. Is there any limitation on the number of circuits to wooden moulding? None given by Code. 313. May wooden moulding be used in damp or concealed places? No. (26-k.) 314. When may wooden moulding be used? Only in exposed dry places where difference of potential between any two wires on same moulding is not over 300 volts. (26-!.) 315. Is the painting of wooden moulding with two coats of water-proof material obligatory? Yes, unless soaked with a moisture repellant. (6o-a.) 316. Is it necessary for moulding to be made in two pieces? Yes; backing and capping. (60 -b.) 317. Can soft wood be used for moulding? Code suggests hard wood only. (60 -b.) 318. Is it required that wooden mouldings be marked with manufacturer's name and marking? No, specifically required for metal, but no require- ment for wood. 319. On alternating current systems, must two wires of a circuit be drawn in the same wooden moulding channel? Not required by the Code. Customarily in the separate grooves. 74 OFFICIAL NATIONAL ELECTRICAL CODE 320. What must be the thickness of: First, back? Second, sides? Third, tongue between conductors? First, 3/8 in. from the bottom of groove through the backing. Second, 1/4 in. through side from groove. Third, tongue thickness 1/2 in. between conduc- tors. (60 -b.) SECTION SIX DIVISION TWO METALLIC PROTECTIVE SYSTEMS IN GENERAL Interior Conduits All Kinds. Lined Metal Conduits. Metal Conduits Unlined. Metal Conduits Flexible. Armored Cables Armored Cables Grounding. METAL MOULDINGS [Limited to 300 Volts, 660 Watts] Metal Moulding. Grounding. 75 SECTION SIX DIVISION TWO Metallic Protective Systems, under which is grouped: conduits of all kinds; lined metal conduits; unlined metal conduits; flexible metal conduits; armored conductors; metal moulding. METALLIC PROTECTIVE SYSTEMS Note No. 26: The author has grouped rigid and flexible metallic conduit; armored flexible conductor; and metal moulding under the metallic protective systems. Metallic protective systems offer the fullest measure of protection from mechanical injury to interior wires. In conduits, properly installed, conductors may be withdrawn and insertea at will. For metal moulding, accessibility to the wires is secured. Armored flexible conductors are quickly installed. In a few cases, iron piping is accepted under the Code for protective purposes as well as conduit, but iron piping, even galvanized, is not encouraged, nor much used except for outside work. For work exposed to view, all of the metallic protective systems are accepted. For concealed work or in damp places, or exposed to mechanical injury all except metal moulding are approved. All these systems require grounding. They rely upon contact insulation, of the conductors contained, for durability instead of the air gap of the knob and tube system. Wherever metallic protective systems are combined with knob and tube systems, care should be taken that the former is definitely begun and terminated in a proper manner, by a correct box or fitting. IN GENERAL 321. What requirements are applicable to all of the metal- lic protective system? Must be continuous from outlet to outlet, to junction boxes or approved fittings (for metal mouldings especially designed); must at all outlets be provided with approved terminal fittings protecting insulation of conductors from abrasion, unless such protection is afforded by the construc- tion of the boxes or fitting; and wires must be continuous in- side tubing without splice or cap. (2Q-a, 27-6 and 26-0.) All alternating-current conductors of circuit must be placed in the same casing or conduit. (26-6, 29-6 and 26-p.) 77 ?o i. Tk i )) 78 QUESTIONS AND ANSWERS ON THE 322. May wires of different circuits of the same system! be placed in the same metal or wooden moulding channel? jj No rulings specifically forbid it if channels can prop- erly accommodate the wires. Note No. 27: The Code's intention is to limit mouldings f] a separation of opposite polarity wires. Wires of the same system and polarity may therefore go ^ the same channel. The number of circuits in conduit work li mi ted, however, to four 2- wire or three 3- wire. (See 26-p. Interior Conduits All Kinds. Questions on grounding Nos. 373-378 apply. 323. When may more than four 2- wire or three 3-wil circuits be placed in any one conduit? Special permission of insurance department having jurisdiction. (26-p.) 324. May conduits under any circumstances contain cifl cuits of different systems? No. (26-p.) 325. What is the smallest internal diameter allowed fa conduit? Five-eighths inch, inside measurement. (28-a.) 326. May conductors be installed in conduits before co pleting the entire conduit system? No. (28-c.) 327. May wires be drawn in conduit before carpenterii or other mechanical work on building is completed? No. (26-0.) 328. Is mechanical security of a conduit system by mea of twisted wires or clips or otherwise securing conduit position required? Yes, (28-b) also applies armored cables. (27-b.) 329. Must unlined conduit have an interior coating? Yes. Code says "Which will readily distinguish from ordinary commercial pipe commonly used for other tha electrical purposes." (58-!.) 330. Is it required that conduit be properly entered an be secured to all fittings? Yes. (28-b.) 331. In service connections and main runs, must ea conduit run continuously into the main cut-out cabinets -a.) 506. When switches larger than 30 amperes are installed in cabinets, what construction is necessary? Cabinet must be deep enough to permit switch to be thrown as wide open as its construction, or the limits of the installation conditions will permit. (70 -a.) 507. Is it obligatory that cabinets be substantial and dust- proof? Yes. (7o-a.) 508. On unlined doors of metal which are less than 0.109 in. (Xo. 12 Sheet Metal Gauge) how much space must be kept between door and enclosed fuses and any live metal part at all times? One inch. (7o-a.) 509. Where link fuses are used in cabinets, what space must be provided between them and metal, metal-lined, or glass-panelled cabinet doors? At least 2 in. (7o-a.) Panel Boards. Following questions do not apply to central station switch- boards, or switchboards with primary control of generators or transformed energy, including isolated plants. (69, fine print note.) 510. Must tablets and panel boards bear manufacturer's name, voltage design and maximum capacity of amperage? Yes. (6 9 -c.) 511. How must tablet or panel boards be designed with reference to the relative arrangement of fuses and switches, epacings of same, etc.? Comply hi general with space requirements for switches, cut-outs, etc. See Tables No. 27-29. (69-a-b and 7o-a.) 512. Must fuses be placed between busbars and switches or oppositely in front of the switch, i.e., between switches and circuits? Either is acceptable, except in case of service switches. (69-a.) See No. 424-425. 102 OFFICIAL NATIONAL ELECTRICAL CODE 513. How close may exposed live metal parts on back ol board come to cabinet on which board is mounted? Must be kept away not less than 1/2 in. (69 -a.) 514. Is it necessary when branch switches are betweer fuses and busbars for connections to be so arranged thaSl blades will be dead when switches are open? Yes. (6 9 -a.) 515. Give minimum spacings between bare live parts, busbars, etc. See Table No. 29, Section 9. SECTION SIX DIVISION FOUR THEATERS AND MOVING PICTURE SHOWS IN GENERAL Emergency Lights, Stage Work-construction, Stage Work, wattage Limits, Foot Lights, Border and Proscenium Side Lights, Border Wiring, Stage and Gallery Receptacles, Scene Docks, Curtain Motors, Minimum Thickness Metal, Bunch Lights, Strips, Portable Plugging Boxes, Pin Plug Connectors, Portable Conductors, Lights on Scenery, String or Festoon Lights, Special Electrical Effects, Dressing Rooms, Arc Lamps for Stage Effects Portable, Competent Operators, Stage Flue Control. MOVING PICTURE EQUIPMENTS Reels with Films under Examination or Rewinding, Auto- matic Shutter, Extra Films, Machine Operation, Machine Installation. OUTLINE LIGHTING . Wattage and Receptacle Limits, Sockets and Receptacles ELECTRIC SIGNS Installation and Wattage Limits. In General. DECORATIVE LIGHTING SYSTEM ELECTRIC HEATERS FOR GENERAL USE MERCURY VAPOR LAMPS, HIGH POTENTIAL VACUUM TUBE SYSTEMS Grounding. Mercury Vapor Lamps Enclosed. 103 SECTION SIX DIVISION FOUR THEATERS AND MOVING PICTURE SHOWS IN GENERAL Following questions apply more particularly to theaters I and moving picture shows and their details. Unless other- wise indicated all rules and requirements of the National jiCode Class "C" (Inside Wiring) apply. The code defines buildings under this heading as follows: "A building of that part of a building regularly or frequently used for dramatic, operatic, moving picture or other per- formances or shows, or which has a stage for such performances used with scenery or other stage appliance." (38.) 516. When are two separate and distinct services re- quired? Whenever supply may be obtained from two separate street mains. (s8-a.) 517. What capacity and application must these two services have? The first sufficient to supply current for entire equipment of theater, and the second, at least a sufficient capacity to supply current for all emergency lights. (38-3.) 518. Where supply cannot be obtained from two separate sources, where must feed for emergency lights be taken? From point on street side of main service fuses. (38-a.) Note No. 37: Intention is to ensure fire hazard protection (as well as life) by minimizing any possible interruption to emergency lights. Emergency Lights. 519. Define emergency lights. Exit lights, all lights in lobbies, stairways, corridors, and other parts of theater to which public have access, which are normally kept lighted during the performance. (38-3.) Note No. 38: Theater arrangements should always in- clude lights marking exits, fire escapes and similar places for guidance of audience in case of fire or panic. 520. When must there be an auxiliary service to supply a theater? 105 106 QUESTIONS AND ANSWERS ON THE J When main source of supply is inside the buildi an auxiliary service for emergency lights particularly mus be taken from before fuses of a street main ; a storage batter] within the premises is regarded as an equivalent. (3 8 -a. 521. How many fuses may exit lights have between then and the service fuses? Not more than one set and in cabinets. (38-t.) 522. May exit and audience lights be controlled excep from lobby or other quickly accessible place in front of house? No. (38-t.) 523. May exit and audience lights be placed on lighting circuit? No; must be fed independently of stage light (38-t.) 524. Are general auditorium lights included in audienc lights? No. (38-a.) Stage Work Construction. 525. What kind of permanent construction must be use* on stage side of proscenium wall of theater? Conduit or approved armored cable. (s8-b. Exceptions : Borders and other necessarily flexible installa tions, as indicated by the questions upon the particular piec of apparatus or appliance. (38-b.) 526. Are wooden switchboards permitted for theaters? No. ( 3 8-c.) 527. When must stage switchboards be protected by guard rail? Whenever accessible from the stage level. (38-0.) Wattage Limits Stage Work. 528. Is it necessary to solder wires to lugs of all recej tacles in foots, border and proscenium side lights? Yes. ( 3 8-d, 38-6-3.) 529. Give wattage limit and greatest number of recej tacles dependent upon one cut-out permitted on foot: borders, and proscenium stage lights. 1320 watts; 24 receptacles. (38-d and 38-6-2.) OFFICIAL NATIONAL ELECTRICAL CODE 107 Footlights. 530. Must receptacles in footlights be enclosed in approved outlet boxes, or will lamp receptacles mounted in iron or steel box be approved? Either method is approved, with an approved con- duit or armored cable enclosing the conductors supplying same. (38-d.) 531. Is a steel trough built to enclose live parts of recep- tacles and to contain all wires, acceptable? Yes, if not less than 20 U. S. sheet metal gauge, en- closing all wires. (38-d.) 532. Must wires be soldered to receptacle lugs for foot- lights? Yes. ( 3 8-d.) Borders and Proscenium Side Lights. 533. How must troughs be treated for borders, pro- scenium side lights and as otherwise used? Be painted to prevent oxidation, or otherwise treated ; be suitably supported and stayed. (38-6-1.) 534. Where flanges of a border light trough are arranged to protect lamps from mechanical injury, is this acceptable instead of wire guards or meshing? Yes. (38-6-1.) 535. What kind of guards are necessary to prevent con- tact of scenery or other combustible material with the lamps in borders and proscenium sidelights? "Suitable guards." (38-6-4.) Note No. 39: Wire netting serves. Border Wiring. 536. What kind of wire must be used for wiring borders? Approved slow-burning insulation. (38-6-6.) Type letter S. B. 537. What kind of cables must be used for borders? Type letter B. See Table No. 16, Section 9. 538. How must border trough be suspended? By at least one strain insulator inserted at border if a wire rope is used. (38-6-7.) 539. What construction is specific from switchboard to where border cable begins? 108 QUESTIONS AND ANSWERS ON THE Conduit construction. (38-6-5.) Stago and Gallery Receptacles. 540. Must stage and gallery pockets be controlled from switchboard? Yes. ( 3 8-f.) 541. Must they be of approved type? Yes. (38-1.) 542. Can plugs for arcs and incandescent pockets be interchangeable ? No. (38-f.) 543. Give rating for each receptacle for an arc lamp. Thirty-five amperes. (38-f.) 544. Give rating for a stage receptacle for incandescent lamps. Not less than 15 amperes. (38-f.) 545. Must both arc lamp and incandescent lamp recep- tacles be wired to full capacity? Yes. (38-f.) 546. What size wire must be used for arc lamp pockets? No smaller than No. 6 B. & S. (38-f.) 547. What is the smallest size wire permitted for an incandescent pocket? No. 12 B. & S. ( 3 8-f.) Scene Docks. 548. What special precaution must be taken for location of lamps in scene docks? Must not be liable to mechanical injury. (38-g.) Curtain Motors. 549. What type of motors must be used for curtain motors? Iron clad type. (38-h.) Minimum Thickness Metal. 550. Give minimum thickness border, strip, and footlight metal? No. 20 TJ. S. sheet metal gauge. 38-6-1, 38-m and 38-d. Bunch Lights. 551. May bunch lights contain any exposed wiring? No. (38-1.) OFFICIAL NATIONAL ELECTRICAL CODE 109 552. Is it required that cables feeding bunch lights be fastened to prevent mechanical strain? Yes. (38-1.) 553- I s a bushing necessary where cable passes through metal, in order to prevent abrasion? Yes. ( 3 8-l.) Note No. 40: Above applies to borders, foots, and all kinds of appliances on stage as well as off. Provision that mechanical strain be avoided is also general. Strips. 554. How must wiring be done for strips? Approved conduit or armored cable, with lamp receptacle in boxes; or all wires enclosed in iron or steel box. (38-01.) 555. How must strips be built and hung? Flanged to protect lamps; properly stayed and sup- ported and made of steel thickness No. 20 U. S. M. gauge. (38-m.) Portable Plugging Boxes. 556. Are boxes with exposed carrying parts approved? No. (38-n.) 557. Are approved fuses with slate or marble bases ob- ligatory for each receptacle? Yes. ( 3 8-n.) 558. How must fuses for portable plugging boxes be en- closed? In fire-proof cabinet with self-closing doors. (38-n.) 559. What must be the capacity of each receptacle in a portable plugging box? Thirty amperes; without undue heating. (38-n.) 560. How much current must the busbars of each port- able plugging box carry without undue heating? Equal to the amount required by all the receptacles fed by the box. (38-n.) Pin Plug Connectors. 561. Must pin plug connectors be of approved type? Yes. "So that female part of plug will be on live end of cable; and must be constructed so that tension on 110 QUESTIONS AND ANSWERS ON THE the cable will not cause serious strain on the connections." (38-0.) Portable Conductors. 562. What is the limit for stand lamps where conditions are such as to justify the use of ordinary approved ("P" type letter) reenforced cord, for protection from mechan- ical injury? Six amperes. (3 8 -p.) 563. Does the above apply to all arcs, bunches and other portable equipments used in stage business, and what kind of cable is required in order that a higher amperage may be used? No, approved stage cable. (38-?.) (Type letter T.) See also table 16. Lights on Scenery. 564. Must brackets for use on stage scenery be wired inside? Yes. ( 3 8-q.) 565. How far must such brackets project in the rear? "Fixture stem must come through to the back of scenery and be properly bushed." (38-q.) String or Festoon Lights. 566. What kind of wire may be used for string or festoon lights under ordinary conditions? Rubber-covered. (38-1.) 567. Must guards be used for lanterns or similar devices? Yes. ( 3 8-r.) 568. Is it necessary to tape and solder joints for string and festoon lights? Yes. (38-r.) 569. How must such joints be located in wires? Staggered. (38-r.) Note No. 41: "Staggered" means alternating joints, so that no two will come close together. Special Electrical Effects. 570. For devices for producing lightning, water-falls, etc., what special protection must be given? ' OFFICIAL NATIONAL ELECTRICAL CODE 111 Location must be such that sparks cannot come in itact with combustible materials. (38-3.) ing Rooms. 71. How must dressing room pendant lights be installed? Approved reinforced cord (type letter "P" or P. Wp.) armored cable type A. C. or steel armojed flexible cord (type letter P. A.) ( 3 8-j.) 572. Are approved lamp guards required for all lamps in iressing rooms? Yes. ( 3 8-j.) \ic Lamps for Stage Effects Portable. 573. Is any substitute for metal allowed in the construc- iion of a stage effect arc lamp? No, except where use of approved insulating material s necessary. (38-k-i.) 574. Is construction of stage arc lamps so that proper ventilation, confinement of sparks within, and 'mica for :he frame insulation necessary? Yes. (38-k-2.) 575. Is self-closing hinged wire gauze or glass door equired for front openings of doors of stage lamps? Yes, except hi lens lamps, where front may be tationary and solid door used on back or side. (38-k-3.) 576. Is a construction that will keep arc lamp carbons and ive parts away from liability of contact with metal hood luring operation necessary? Yes, arc lamp frames and standards must be so con- tructed as to prevent grounding liability. (38-k-4.) jl 577. Are knife switches allowed on lamp stands? No, unless so enclosed and protected that accidental [ive contact is impossible. (38-k-5.) | 578. Are approved lugs necessary for stranded connec- ions in lamp and at switch and rheostat? Yes. (38-k-6.) ! 579- How high from floor must rheostat on portable thea- sr arc lamp stand be located? At least 3 in. (38-k-7.) 580. Is it obligatory that rheostats for arc lamps be lainly marked with the rated capacity in volts and amperes? 112 QUESTIONS AND ANSWERS ON THE Yes. ( 3 8-k- 7 .) 581. Is it obligatory that resistance be enclosed in a sul stantial and properly ventilated metal case? Yes. ( 3 8-k- 7 .) 582. How much clearance must be afforded between fac and resistance clement? One inch. Competent Operator. 583. What is the greatest number of arc lamps on operator may watch, and under what conditions? Two; not more than 10 ft. apart and located so ths he can properly watch and care for both lamps. (38-k-8, 584. Is the employment of a competent operator to cai for not more than two lamps located as in last questioi obligatory? Yes. (38-k-8.) Stage Flue Control. 585. Can the so-called open circuit system (normally) I used for electric release of dampers? No. ( 3 8-i.) 586. Must operating magnet take full voltage of supp circuit without resistance devices? Yes. (38-1.) 587. Must operating magnet on damper in full operatic have normal heating limit? Yes. (38-1.) 588. How must magnet be located and installed? In loft above scenery and installed in suitable iron b with self -closing door. (38-!.) 589. How many switches are required, and how mu dampers be controlled? Two single -pole switches in iron boxes approv and with self -closing doors without lock or latch; o switch located at electrician's station and others as d ignated by the insurance department having jurisdictic (38-u-f.) OFFICIAL NATIONAL ELECTRICAL CODE 113 MOVING PICTURE EQUIPMENT 590. How must arc lamps used as part of moving picture machine outfits be constructed? Same requirements as arc lamps of theater. See questions Nos. 573 to 582 inclusive. Division 4. (38-11-1.) 591. What is the smallest size conductor permitted for arc lamps? No less than No. 6, B. & S. (38-u-i.) 592. How must moving picture rheostats be installed? Must conform to theater arcs. See Questions 579 to 582 inclusive. (38-U-2.) 593. Is it necessary to enclose top and bottom reels in flame-proof steel magazines or boxes? Yes. (38-11-3.) 594. Can solder be used on these boxes or magazines? No. (38-U-3.) Reel with Films under Examination or Rewinding. 595. How must reels containing films as above be kept? In magazines or approved metal boxes; not more than 2 ft. of film exposed in booth. (38-u-S.) 596. How must the openings be made in the boxes or magazine? Front side consists of door, spring hinged, and swing- ing horizontally and provided with substantial latch. (38- u-30 Automatic Shutter. 597. How must shutter operate to prevent action of the beam of light upon the inflammable film when film is not running at operating speed? Shutter must shield automatically. (38-U-4.) 598. Is it obligatory that shutter be permanently attached to gate frame? Yes. (38-U-4-) Extra Films. 599. How must extra films be kept? In individual metal boxes with tight-fitting covers. (38-u-s.) 8 114 QUESTIONS AND ANSWERS ON THE Machine Operation. 600. Are motor-driven machines permitted? Yes, under following : "6. Machine. Must be of an approved type. If driven by a motor must be of a type expressly designed and approved for such operation, and when so approved, motor driven machines, when in charge of a skilled operator, may be permitted by the Inspection Department having jurisdiction." Promulgated April, 1912, List of Fittings." Machine Installation. 60 1. How must machines as a whole be installed? Machine Enclosure. Machine must be placed in an enclosure or house made of suitable fire -proof material; must be properly ventilated, properly lighted and large enough for operator to walk freely on either side of or back of ma- chine. All openings into this booth must be arranged so as to be entirely closed by doors or shutters constructed of the same or equally good fire -resisting material as the booth itself. Doors or covers must be arranged so as to be held normally closed by spring hinges or equivalent devices. ( 3 8-u-7.) OUTLINE LIGHTING Low Potential 550 to 10 Volts. Wiring other than signs on exterior of buildings. See 619. Note No. 42: This class of wiring applies in distinction to so-called temporary lighting. 602. Is any kind of moulding permitted for outline wiring? No. (39-b.) 603. What three kinds of work are permitted for outline wiring? Open work with rubber -covered wire. Conduit work. (39-b.) Lead sheathed armored cable also. (39-6.) 604. How must wires for open work be installed? i in. from surface wired over; 2 1/2 in. apart up to 300 volts. 4 in. apart if over 300 volts ; (39-c.) 605. Is it necessary to seal the ends of flexible tubing when used in this work? Yes. (39-d.) OFFICIAL NATIONAL ELECTRICAL CODE 115 606. If flexible tubing is applied, must it be kept away from the surface wired over? Yes, must be knob -mounted or otherwise supported a half inch at least from surface wired over. (39-d.) 607. Must wires for use in rigid or flexible steel conduit on outline wiring be of special insulation? Yes, type letter R-D wire (has 1/32 extra fibrous covering) for wire larger than No. 10; at least 1/64 extra for wires No. 10 or less is required for unlined conduit work. (39 -e.) See table 8. 608. What kind of protective covering must be used where armored cable is applied? Armored cable must be of lead sheathed type, with sheath between armor and insulation. (39-6.) 609. Is separate controlling switch and cut-out required for outline lighting systems? Yes. (39-f.) 610. What precaution must be taken with switches, cut- outs, flashers, time switches and similar appliances where located outside of building. Enclosed in steel or cast-iron box. (39-f.) 6 1 1. How must above appliances be installed where lo- cated inside of building? According to Code requirements for such devices, as indicated by Question No. 438, Section 6, Inside Wiring. (39-fO 612. What is the minimum thickness allowed for a steel box used on outline lighting enclosures at switches, etc.? No. ii U. S. sheet metal gauge, or 0.125 in. (39-f.) 613. How far must knife switch clear a door in an outside steel box? One inch. (39-gO 614. Is it necessary for boxes to be moisture proof whether inside or outside? Yes. (39-g.) Wattage and Receptacle Limits. 615. What is the wattage limit of a circuit dependent upon one double pole cut-out? 1320 watts. (39-h.) 6 1 6. What number of sockets or receptacles may be connected to a single circuit? 116 QUESTIONS AND ANSWERS ON THE Sixty-six, (39-h.) Sockets and Receptacles. 617. What kind of sockets and receptacles must be used? Keyless, porcelain type. (39-!.) 6 1 8. Must wires be soldered to lugs on sockets and receptacles? Yes. (39-i.) ELECTRIC SIGNS (On 550 volts or less) Installation and Wattage Limits. 619. What is the allowance of sign and outline wiring circuit fuses of 55 volts or less? Twenty -five amperes. (23-d.) 620. What is wattage limit on final cut-out for electric sign circuits? 1320 watts. (83 -g.) In General. 621. May approved receptacles alone support the wires? Yes, if supporting every foot; holding one inch high; 2 1/2 inches apart (83-6.) 622. Is open work wiring permitted for signs, and where? Only on roofs or open ground where not subject to mechanical injury. (83 -b.) Read 643. 623. How must wiring up to an open work sign be done? Open work, Conduit, or armored cable (83-6). See Question 631. 624. In open work signs (wires not enclosed with any metal conduit), what is the space limit for receptacle terminals from each other and from the sign metal? One inch. (83-d.) 625. In passing through walls or partitions of a wooden or a metal sign, must approved bushings be used? Yes. (83 -e.) 626. Must cut-outs, transformers for low wattage lamps, flashers and similar devices be in a weather-proof and access- ible compartment when built in the sign ; or how otherwise installed? Yes; or enclosed in a separate substantial box of OFFICIAL NATIONAL ELECTRICAL CODE 117 metal with equivalent thickness of the sign metal and access- ible. (83 -b.) 627. When may wood be used for decoration only of electric sign? When kept 2 in. from nearest lamp receptacle. (83 -a.) 628. What size sheet metal must be used for electric signs? Not less than No. 28 U. S. Gauge. (83 -a.) 620.. What size holes are required for drainage in the bottom of a compartment? Not less than 1/4 in. in diameter. (83 -b.) 630. Is galvanized, enameled, or three-coat painted metal acceptable and required? Yes, as approved protection against corrosion it will be acceptable. (83 -a.) 631. In metal signs (where conduit, cable, or metal com- pletely encloses conductor), give space limit for receptacle terminals from each other and from sign metal? One-half inch. (83-d.) 632. Must receptacles for signs be of special design? Yes. (8 3 -d.) 633. How must receptacles be designed and placed? To prevent possible turning after installation. (83 -d.) 634. Are wires on the outside of electric signs (in open work), permitted to touch metal? What is surface distance? No.; i in. (83-6.) Read 624. 635. How must exposed parts of wires and terminals be treated? So as to prevent corrosion. (83-6.) 636. Must all wires be soldered to terminals? Yes. (83 -e.) 637. How far apart must open wiring for signs be kept? Two and one -hah* inches up to 300 volts; 4 in. for higher voltages. (83-6.) Read 621. 638. Where open work is not permitted by general Code conditions, what system must be used on the outside of sign structure? Approved metal conduit or approved armored cable. (8 3 -e.) 118 QUESTIONS AND ANSWERS ON THE 639. What special support when distances are more th 1 ft. apart and less than 2 ft. apart between receptacles, is required? Additional insulator preserving the required spacing must be inserted. (83-6.) Read 621. 640. Is approved metal conduit or armored cable satis- factory for passing leads from sign to outside? Yes. (8 3 -f.) 641. What other method is approved for conducting wires from signs to connect with supply wires? Neatly cabled and passed through one or more ap- proved non -combustible, non-absorptive bushings. (83-f.) 642. Is any size less than No. 14 B. & S. permitted on signs? No. (83-6.) 643. Must double braided wire always be used? Yes, except where open work is permitted, see ques- tion No. 622, when ordinary type is acceptable. (83 -f.) 644. May single-pole switches be used for control of out- door signs? No. (24-0.) DECORATIVE LIGHTING SYSTEMS Christmas tree series miniature outfits acceptabl April, 1912, List of Fittings. 645. Is special permission in writing necessary from the inspection department for temporary installation of so- called decorative lighting? Code says may be given. (37-a.) 646. What limitation is placed by the National Code upon the approval of decorative lighting systems by the inspection department having jurisdiction? The wires of any circuit shall not be over 150 volts, and no group of lamps requiring more than 1320 watts shall be dependent on one cut-out. (37-a.) ELECTRIC HEATERS FOR GENERAL USE 647. Is an approved stand for flat iron and similar heat- ing appliances obligatory? Yes. (25-6.) 648. How must stationary electric heater be installed? OFFICIAL NATIONAL ELECTRICAL CODE 119 In plain sight protected by a cut-out, controlled by a switch (double pole when over 660 watts), plainly showing when current is on or off; and isolated from inflammable materials. (25-a and b and f.) 649. May electric heaters be concealed? No, except by special permission of inspection de- partment having jurisdiction. (25-b.) 650. Can ordinary flexible cord be used for portable heat- ing devices, such as flat irons and smoothing irons, consum- ing over 250 watts? No, must have asbestos fiber covering over rubber of cord and otherwise as under Table No. 14, Section 9, Flex- ible Cords. (54-d-) 651. How must cords or cables be attached to heating apparatus? So that kinking or chafing at or near point of con- nection will be avoided. (25 -d.) 652. How must a flexible conductor for heating devices be connected to the circuit? By an approved plug device pulling out in case of abnormal strain on conductors. (25 -d.) 653. How must radiators, ranges, plate warmers be treated? As sources of heat and isolated from inflammable material. (25 -f.) 654. Must such devices be provided with name plates? Yes, giving the maker's name and normal capacity in volts and amperes. (25 -g.) MERCURY VAPOR LAMPS, HIGH POTENTIAL, VACUUM TUBE SYSTEMS 655. How must the high potential coils and regulating apparatus be installed? In approved steel cabinets not less than i/io in. thickness, well ventilated and constructed, so as to confine escaping flame or sparks in case of burn-out in the various coils. (34-d.) 656. Is it necessary to mount all apparatus in steel cab- inets on a slate base? Yes. (34-d.) 120 OFFICIAL NATIONAL ELECTRICAL CODE Grounding of Mercury Vapor Lamp Systems High Po- tential. 657. Is it necessary to ground the steel cabinet? Yes, either steel cabinet or enclosing case of appa- ratus must both be grounded on positive side. (34-d.) Mercury Vapor Lamps Enclosed. 658. What requirements govern supply conductors lead- ing into high potential case, and what voltage limitation applies? Standard requirements according to system used un- der low potential and not over 300 volts. (34-d.) 659. What is the maximum number of mercury vapor lamps permitted on one cut-out? Five, when contained in a single frame and lighted by a single operation. (34~a.) 660. Are cut-outs obligatory for each lamp or series of lamps? Yes. (34-a.) 66 1. How must resistances be protected when exposed to flying lint or combustible material? By fine wire gauze over all openings through casing. (34-b.) 662. Can any other resistances or regulators except those enclosed in non-combustible cases be used? No. (34-d.) SECTION SIX DIVISION FIVE FIXTURES AND SOCKETS AND FLEXIBLE CORDS Fixtures in General Canopies. Fixtures in Show Cases. Fixtures Wooden. Portable Lamps. SOCKETS Double-ended Sockets. Miniature Candelabra. Water-proof Sockets. FLEXIBLE CORD, THEATER CABLES AND ELEVATOR CABLES 121 SECTION SIX DIVISION FIVE FIXTURES AND SOCKETS AND FLEXIBLE CORDS [Limited to 300 volts maximum. Below 10 volts, no Code requirements.] Fixtures in General. Following questions apply to fixtures in general, except as specifically indicated. References are principally taken pom Code Class "C" Inside Work and Code Class "D." 663. What is the maximum voltage permitted between conductors in the same fixtures? Three hundred volts. (26-7.) 664. May No. 18 fixture wire or cord which has a carry- ing capacity of 3 amperes, be protected with a 6-ampere fuse? Yes. (2 3 -e.) 665. What is the limit of wattage for any number of lamps on one cut-out, whether on one fixture or several? Six hundred and sixty watts. Exception in case large chandeliers and theater wiring by inspection department having jurisdiction. (23-d.) 666. What is the smallest size wire permitted on fixtures, either solid or stranded? No. 18 B. & S. (55-b.) 667. Can ordinary approved No. 14 (type letter R. S.) rubber-covered wire be used on exposed work on fixtures? Yes. (ss-a.) 668. Can fixtures be wired with any kind of approved flexible cord? Yes. (55-a.) 669. Are stranded conductors approved for fixture work? Yes. (55-b. Also 54 a to c.) 670. Is it necessary for solid fixture wire conductors to be "tinned"? Yes. (55 -c, and 50 -a.) 123 124 QUESTIONS AND ANSWERS ON THE 671. When may slow-burning wire be used on fixtures? Where wiring is exposed to over 120 F. (55-a.) See also No. 701. 672. What test is sufficient to show the elasticity of the braid required on fixture wiring? Must be elastic enough to stand being bent around a cylinder twice the diameter of the wire without injury to the braid. (55-e.) 673. May the wires of two systems be introduced in or on the same fixture, such as an electrolier fan or a chandelier? No. (26-y.) 674. Where conductors are not completely enclosed in metal, as on chains for domes, what kind of wires are re- quired unless pendant (type letter "C") or portable (type letter "P ' ') is used? Stranded rubber-covered; insulation not less than 1/32 in. thick and braided (77-d.) 675. Where supply wires enter fixture stems or casings, are hickeys or similar devices protecting wire coverings approved? Yes, must be used. (77-d.) 676. How must straight electric fixtures be attached when connected on a concealed knob and tube job? To a 7/8 in. wooden block fastened securely between studs and floor timbers flush with back of the laths which must be large enough to allow boring for the flexible tubing to enclose each wire. , and properly support fixture. Or, a 3/4 in. wooden block must be placed on the plaster side of the laths and securely screwed thereto. (24-e.) 677. How may supply wires be insulated from gas pipes? Flexible insulating tubing must be placed over wires from last knob to one inch beyond outlet. (26-u) Read 304. 678. How near to the ceiling or walls must the insulating joint required on combination or otherwise subject to ground fixtures be located? As near as possible. (3O-a.) 679. How must fixtures supported at outlets on metallic protective systems or from any gas piping, metal lathing or any other part of the building, grounded or liable to be grounded, be insulated? OFFICIAL NATIONAL ELECTRICAL CODE 125 By approved insulating joint as close as possible to celings or walls of the building, (ao-a.) Read No. 688. 680. Can electric gas lighting circuits or bell wires be installed on combination fixtures? Frictional system only. (87-a.) 68 1. How must gas pipes be treated above the insulating joint? By approved flexible tubing over pipe, (ao-a.) 682. How must outlet tubings be secured? So that they will not be pushed back when canopy is in place. (30 -a.) 683. Is it necessary for fixtures to be of water-tight con- struction when installed out of doors? Yes. (30-b.) 684. Are fixtures wired on the outside approved for use in show windows or in vicinity of especially inflammable material? No. (30-0.) 685. May fixtures be installed that contain short circuits between conductors; or contact between conductor and metal or fixtures? (So-called "grounded fixtures.)" No. (ao-d.) 686. Must fixture arms be secured with a set screw or otherwise in addition to being screwed in the body of the fixture? Must be reliably secured to prevent turning. (77-b.) 687. What other methods may be used, instead of set screws, to secure arms to fixture body? May be soldered or cemented. (77-b.) 688. When may insulating joints be omitted on fixtures supported at outlets on metallic protective system? When the insulation of the wiring in the straight electric fixture is equal to the insulation of its circuit; and the receptacle, socket, or wireless cluster are approved. (30-a.) Read 679. 689. Are insulating joints with soft rubber in their con- struction approved? No, fine print note. (76-3.) 690. How many threads must engage on screw joints of arms? 126 QUESTIONS AND ANSWERS ON THE At least five. (77-b.) 691. May any other methods than screw joints be used, such as brazing and soldering? Only when ample strength and durability is secured. (77-b.) 692. Must all sockets used on fixtures be permanently attached to the metal? Yes. (77-c.) 693. When may receptacles having exposed terminals be used on fixtures? Only when completely enclosed in metal, such as a box. (77-c.) 694. Is the filing or removal otherwise of burrs, fins and sharp edges required on fixtures? Must invariably be modified or removed so that wires drawn over them will not be injured. (77 -d.) 695. In wire ways on fixture stems and similar places, is it required that wires or flexible cord can be drawn in without injury? Yes. (77-d.) Canopies. 696. Can cut-outs or fuses of any kind be placed in opies or shells of fixtures? No. (2 3 -c.) 697. When fixtures arrive from factory with insuffi- ciently large shells and where canopies and outlet boxes are too small for proper installation of necessary splices, what must be done? They must be changed to provide enough room. (26-W.) 698. If a fixture is attached to a wooden ceiling or to a block on wood lathed and plastered ceiling is a canopy insu- lator required? No. (so-a.) Read 679, 688, 699. 699. Is it necessary to insulate all fixture canopies from wall or ceiling where insulating joints are required? Yes. (30-a.) Read 688. 700. When may flat canopies, tops or backs, be used or fixtures? Only when installed on outlet boxes. (3O-a.) OFFICIAL NATIONAL ELECTRICAL CODE 127 Show Case Fixtures. 701. When wiring for show case fixtures, ceiling bull's eye, such as used in theaters, and similar fixtures where lamps are so enclosed as to cause great heat, is slow burn- ing wire approved? Yes, if temperature is in excess of 120 F. (49 degrees Centigrade). (26-v.) 702. Is it required that such forms of fixtures be sub- mitted for examination, tests and approval to the inspection department having jurisdiction before being introduced to use, unless already approved by Underwriters' Labora- tory? Yes. (26-v.) 703. Does the Code require that supply conductors and fixtures, and especially splices, be kept from contact with grounded part of gas pipes? Yes. ( 2 6-w.) Wooden Fixtures. 704. Are hard wood, or hardwood and metal, fixtures ap- proved, and under what condition? Yes, where requisite mechanical strength is secured of a metal fixture same size and form. (77 -a.) 705. On wooden fixtures, is it necessary to use armored conductors and proper fittings upon all the wood parts? Yes. (77-d.) See also No. 706. 706. What must be done in non-metallic fixtures if arm- 'ored approved conductors are not used? Metal wire -ways must be used, or they must be metal lined. (77-d.) Portable Lamps. 707. When must wire guards be used on portable lamps? Whenever necessary to prevent contact with inflam- mable material or protect from breakage. (32 -d.) 708. What kinds of portable cord may be used with port- ables? Type letters "P" ; "P. Wp. ; and P. O., according to conditions as outlined in Tables Nos. u, 12, 13, Section 9." Type letter P. A. is also permitted. 128 QUESTIONS AND ANSWERS ON THE SOCKETS 709. How must sockets be installed where inflammable gases or injurious vapors exist? Socket and incandescent lamp must be enclosed in a vapor-tight globe supported on pipe hanger and wired with approved rubber -covered wire soldered directly to circuit. (3 1 -a.) 710. Are key sockets forbidden over inflammable stuff or when exposed to flying or combustible material? Yes. (si-c.) 711. What size wire must a socket be able to securely grip? No. 16 or 18 B. & S. (72-h.) 712. How must standard key sockets be rated? The standard key sockets (screw shell, standard Edi- son and ordinary "slow make" switch), 250 watts, 250 volts. (72-b.) 713. Must sockets be marked with manufacturer's name and rating of socket? Yes. (72-a.) 714. What is amperage limit allowed for a standard key or pull socket? Two and one -half amperes. (72-b.) 715. Does a key socket with standard Edison shell and special switch which makes and breaks with a quick snap, and does not stop when motion has once been started by handle or button, take a higher rating than a 250 watt, 250 volt, key socket? Yes, rating 660 watts, 250 volts. (72-b.) 716. How are standard keyless sockets rated? Standard keyless sockets, Edison screw shell, 660 watts, 250 volts. (72-b.) 717. What is limitation on any voltage on a keyk socket? Six amperes. (72-b.) 718. Are sockets with an inlet for 3/8-in. pipe, used pendants, acceptable? Yes, with reinforced cord. (72-e, fine print note.) 719. Are smooth holed inlet insulating bushings necessarj for sockets, and what size hole should they have? OFFICIAL NATIONAL ELECTRICAL CODE 129 Yes, at least 9/32 for ordinary flexible cord drop; larger for reinforced cord. (72 -q. and fine print note.) 720. Is it obligatory for socket to firmly hold lamp in place? Yes. (72-1.) 721. Is a contact sufficient to prevent undue heating with device in place and maximum current obligatory? Yes. ( 7 2-i.) 722. Must socket bases' on which current-carrying parts are mounted be of porcelain? Yes. (72-j.) 723. Is it obligatory that current carrying parts of socket be protected from contact or liability of contact with other objects than as intended? Yes. (72-1.) Example: Sockets hung with pro- tecting shells omitted. 724. What heat test is approved for the material of a socket key handle? That it will not soften in a 70 F. (21 C.) ah-, with the heat of a 50 candle-power (carbon) lamp inserted. (72-k.) 725. Is sealing by water-proof compound necessary for holding screws of sockets in porcelain pieces? what is its melting-point? Yes; 200 F., 93 C. (72-!.) 726. Are porcelain, mica, and similar insulated materials, properly constructed, acceptable for all parts of sockets? Yes, if strong and durable and not applied where subject to hard usage. (72-p and fine print note.) Double Ended Sockets. 727. Are double ended sockets allowed a higher rating or amperage than single sockets? Each end is rated 250 watts, 250 volts, for key sockets ; 660 watts, 250 volts for keyless sockets. Only 21/2 amperes per key socket or 6 for keyless sockets is permitted. (72 -b.) Miniature and Candelabra. 728. How are miniature and candelabra key sockets rated? Seventy -five watts, 125 volts. (72 -b.) 130 QUESTIONS AND ANSWERS ON THE Water-proof Sockets. 729. How must weather-proof drops be installed in damp places? Weather-proof sockets suspended by separate strand- ed rubber-covered wires not smaller than No. 14 B. & S. gauge, (ai-b.) Read 732. 730. When pendant is over 3 ft. long, what recommenda- tion is made for wires in damp or wet places? That they be twisted together. (3i-b.) 731. How must weather-proof drops be connected to the circuit wires? Soldered direct to them, but supported independ- ently of them. (3i-b.) 732. What is rating for weather-proof sockets with standard Edison shells and no exposed carrying parts? Six hundred and sixty watts, 600 volts. (72-b.) FLEXIBLE CORD AND THEATER AND BORDER AND ELECTRIC LIGHTING AND CONTROL CABLES Limit 300 volts maximum For details see Tables 10, 11, 12, 13, 15, 16, 17, Section Nine. (Code Class D, Rule 54) References also Code Class C, Rule 32. 733. Where may type C flexible cord be used? Only for pendants, "drop lights" wiring of fixtures. (32-d.) 734. What kind of cord must be used for portable lamps or motors? Type letters "P" or "P. Wp." See tables n and 12, Section Nine ; or heavier insulations per conditions, accord- ing to tables given. 735- What kind of cord is the only kind permitted in show cases or show windows? Cord having approved metal armor. Type letter P-A. (32-6.) Exception at temperature of 120 F. Read 701. 736. May flexible cord be used on systems of over 300 volts? No, except on street railway property. (32-b.) 737. Is so-called "commercial cord," of insulation and OFFICIAL NATIONAL ELECTRICAL CODE 131 make up less than described in the tables, Section Nine, approved? No. (3 2 -a and 54 -a and b.) 738. How must flexible cord be installed in the socket or rosette on all kinds of drops? Entire weight of socket and lamp upon the flexible cord must be borne by an approved method, such as a knot under the bushing in the socket; a similar arrangement must be made at top in the rosette. (32-g.) 739. What type of cord is approved for pendant lamps provided with long cords? Type letter P. (54-c-i.) 740. Define conditions and insulation required, also sizes for the various applications of flexible cord? See Tables hi Section Nine. 741. Give smallest size conductor allowed in making up the strands of an elevator control cable. (Type letter E.) Sixteen B. & S. (54 -g.) See also Table 17, Section Nine. 742. Define conditions of use and insulation required, and sizes of conductors for theater, and elevator lighting and control cables? See Tables, Section Nine. 743. Is ordinary flexible cord allowed where drop lights (pendants) may come in contact with surrounding objects? All flexibles described under tables in Section 9, ex- cept C and Cw.p are acceptable. (54-c-i.) 744. When must flexible wires or cables be used instead of any of the various type letter kinds (see tables, Section 9) of flexible cord? Whenever service is too severe for then* insulation durability. (32-d.) Example : Long extension cords in packing houses. 745. May flexible cord of any type or kind be used to supply lamps or other devices, when used instead of wire installation even if supported on knobs? No. SECTION SIX DIVISION SIX ELECTRIC CRANES IN GENERAL Switches and Cut-outs. Controllers. Motor Grounding. 133 SECTION SIX DIVISION SIX ELECTRIC CRANES IN GENERAL Questions under Section Six, Code Class "C," also apply in general, except where modified by the following: 746. How must wiring for apparatus, etc., be installed, generally speaking, when not covered by the questions fol- lowing this number? Must comply with the general requirements for its class and voltage. (43, italics, under Electric Cranes.) 747. What kind of insulation must be used on conductors between resistances and contact plates of rheostats? Rubber, where exposed to moisture and an insula- tion is necessary; and where they are grouped. (43-3-1 and d.) See 749. 748. Is slow-burning wire ever required? Yes, where subject to severe external heat. (43- a-i.) 749. What kind of wire is excepted under Question 747? Bare collector wires, those between resistances and contact plates of rheostats, and those subjected to severe external heat. (43-a-i and d.) 750. What is the smallest size wire acceptable in use on electric cranes? No. 12 B. & S. (43-a-i.) 751. How must wires other than collector wires be in- stalled? Per free air system (Section 6, Division i) or metallic conduit system (Section 6, Division 2). In dry places where distance between wires required for open work cannot be secured, (see Nos. 249, 285.) approved flexible tubing (non- metallic) encasing each wire and securely fastened will be accepted. (43-3-2.) 752. At all times, how far must collector wires be kept from the surface wired over? One and one-half inch. (43-3-2.) 135 J 136 QUESTIONS AND ANSWERS ON THE 753. How must collector wires be held at ends? By approved strain insulators. (43 -a -2.) 754. How often must collector wires be supported aloi run ways, unless span is over 20 ft.? Every 20 ft. (43-a-3.) 755. What must be done when span is over 20 ft., and what is the limit? Distance must be increased in the same proportion; in no case shall span exceed 40 ft. (43 --3.) 756. How far must collector wires be separated when rui in a horizontal plane? At least 6 in. (43-a-3) 757. When not run in a horizontal plane, what se] tion must be observed? Eight inches. (43-a-3) 758. Where bridge collector wires are over 80 ft. long, how often must insulating supports (upon which wires may lie loose) be provided? At least every 50 ft. (43 -a -4.) 759. What is the least spacing between bridge collector wires allowed? Two and one -half inches; recommended that greater spacing be used whenever possible. (43-3-4.) 760. What are the minimum sizes for collector wires ac- cording to the distance between rigid supports? "Distance between Size wire rigid supports required Feet B. & S. o to 30 6 31 to 60 4 Over 60 2 (43 -a -50 761. How must collectors be designed with reference to sparking? So that it will be reduced to a minimum. (43 -b.) Switches and Cut-outs. 762. Can one main switch be used for all motors of an j electric crane? Yes. (Italics, 43.) OFFICIAL NATIONAL ELECTRICAL CODE 137 763. Is a cut-out and switch necessary for the main col- lector wires, and how must it be located? Yes; located easy of access from floor. (43-0-1.) 764. Is a cut-out and a switch necessary for leads from main collector wire on electric cranes operated from cabs; and where must they be located? Yes; readily accessible to operator. (43-0-2.) 765. Is it necessary to use a cut-out for each motor of a single crane? Yes, each motor lead must be protected by a cut-out ; locate in cab if used. (43-0-3.) Controllers. 766. Where electric crane is outdoors, what kind of in- sulation is required between resistances and contact plates of rheostats? Rubber-covered, type letters R. S., according to voltage. (43-d.) See tables on wires, Section 9. 767. Where wires are grouped in outside controller, what kind of insulation must be used? Rubber-covered. (43 -d.) 768. How must resistances be treated where crane oper- ates over readily combustible material, such as gunpowder or lint? Resistances must be enclosed in non-combustible material, such as asbestos board. (43-d.) 769. If resistances are in a cab, how far above the top of such resistance is a non-combustible enclosure required? From floor to 6 in. above the top of the resistances. (43-d.) Motor Grounding. 770. Is it necessary for motor-frame trucks and the entire frame of the crane to be grounded? Yes. (43-e.) SECTION SEVEN ELECTRIC RAILWAY SYSTEMS Railway Feed Wires. Trolley Wires. CAR WIRING AND EQUIPMENT OF CARS Protection of Carbody. Wires, Cables, Etc. Cut-outs, Circuit -breakers and Switches. Conduit. Moulding. Lighting and Lighting Circuits. Heaters and Heating Circuits. Air-pump Motor and Circuits. Main Motor Circuits and Devices. GENERAL RULES Grounded Trolley Circuits Flexible Cord. 139 SECTION SEVEN ELECTRIC RAILWAY SYSTEMS Following questions apply upon Electric Railway systems as indicated. References are taken principally from Code Class B, Rule 12, and Code Class C, Rules 40 to 42 inclusive, Outside and Inside Work, respectively. Railway Feed Wires. 771. How must feed wires upon railway power plants before leaving power plant be protected? "Each feed wire must have approved automatic circuit-breaker or other device which will immediately cut off the current in case of an accidental ground. Device must be mounted on fire -proof base and in full view and in reach of the attendant." (9 -a.) Read 776. Trolley Wires. 772. What are smallest sized trolley wires permitted under the National Code? No. o B. & S. Copper or No. 4 B. & S. silicon bronze. f(i2-L) 773. Does the Code require that trolley wires readily stand the strain put upon them when in use? Yes. (i2-i.) 774. How many insulations must trolley wire have from the ground? Double insulation, wooden pole being considered as one insulation. (i2-j.) 775. How must trolley wires be divided? Into sections, so that in case of fire, current may be shut off from the particular section and not interfere with firemen. (i2-k.) 776. Does the last requirement apply also to feeders? Yes. (i2-k.) 777. Is it obligatory to protect against accidental contact when crossed by other conductors? Yes. (12-1.) 778. How must guard wires be insulated and treated? 141 142 QUESTIONS AND ANSWERS ON THE Insulated from ground and electrically disconnected in not more than 300 -ft. sections. (12-!.) 779. What requirement exists upon ground return wires, for the diminution of electrolytic corrosion of underground metal work? Ground return wires must be arranged so that potential difference between grounded dynamo terminal and any point on the return circuit will not exceed 25 volts. (i2-m.) "It is suggested that the positive pole of the dynamo be connected to the trolley line, and that whenever pipes or other underground metal work are found to be electrically positive to the rails or surrounding earth, that they be con- nected by conductors arranged so as to prevent as. far as possible current flow from the pipes into the ground." Fine Print Note. (12-m.) CAR WIRING AND EQUIPMENT OF CARS Protection of Car Body. 780. What protection is required over all wires and parts of the electrical equipment in car bodies and what exception is especially made? One -eighth of an inch approved fire -resisting, in- sulating material, or sheet iron or steel not less than 4/100 inch thickness. Motors 75 h. p. or less and wires carry- ing not over 25 amperes when encased hi metal conduit, excepted. (40 -a -i.) 781. How far must protection above required extend over motors 75 h. p. each? Eight inches beyond all edges of openings on motors. (40-a-2.) 782. How far must the protection required above in Question No. 780 extend beyond edges of motor leads? Six inches on all sides. (4O-a-2.) 783. How far must protection extend beyond edges of all devices (unless amply protected by their casing) over resistances, contactors, arresters, and other electrical apparatus of similar kind? Eight inches. (40 -a -3.) 784. When must conductors be protected by a 6-in. extension of the protection (see Question No. 780) on either side? OFFICIAL NATIONAL ELECTRICAL CODE 143 When designed to carry over 25 amperes, unless conduited with a half-inch air space between conduit and car. (40-a-4.) 785. When may the protection specified in question No. 780 be omitted over cables? When flame-proof outer covering of 1/8 in. is provided entire length of cable; also provided that it shall be thoroughly taped or sewed at the ends, where taps are made, and where it enters apparatus. (40-3-4.) 786. How must fire-proof material or sheet iron or steel be treated in car bodies? Must have joints well fitted; securely fastened to sills, floor timbers and cross braces; and have entire surface treated with water-proof paint. (40-3-5.) 787. What material is required for cut-out and switch cabinets? Substantially made hardwood, lined with fire -resist- ing insulating material securely fastened to the woodwork. After material is in place, inside of cabinet must be treated with a water-proof paint. (40-3-6.) Note No. 43: Metal boxes not code. Wires, Cables, Etc. Wires laid (not drawn) in conduit may be R. S. type. (4o-b- 3 .) 788. What is the minimum size for motor, trolley and resistance leads? No. 7 B. & S. (4o-b-i.) 789. Give minimum size conductor for heater circuits? No. 12 B. & S. (4o-b-i.) 790. Give minimum size for lighting and similar auxili- ary circuit?? No. 14 B. & S. gauge. (4o-b-i.) 791. How is the safe carrying capacity of motor, trolley and resistance lead wires or conductors to be de- termined? "The current used in determining the size of motor, trolley and resistance leads shall be the per cent, of the full load current, based on one hour's run of the motor, as given by the following table : 144 QUESTIONS AND ANSWERS ON THE Size each inotor Motor leads Trolley leads Resistance leads 75 h p or less 50 per cent. 40 per cent Over 75 h. p 45 per cent. 35 per cent. 15 per cent. 792. May approved fixture wire be used on approved clusters? Yes. (4o-b-i.) 793. When not in conduit or approved moulding, or in cables with 1/8 in. enclosing flame-proof covers, is a special rubber-covered wire required? Yes. (40 -b -4.) Exception: When motors are en- closed so that flame cannot extend outside of casing, flame- proof covering is not required on motor leads. (40-5-4.) 794. What sort of joints need not be soldered? Those with approved splicing devices, and those con- necting leads at motors, plows or third -rail shoes. (40-5-5.) 795. How must cable connections over 25 amperes be made (controller connection boards excepted) when applied to cut-outs, switches and fittings? Lugs or terminals must be soldered to the cable and securely fastened to the device by screws, bolts or clamping. ( 4 o-b-6.) Or, end of cable dipped in solder, and fastened with at least two sets of screws with check nuts. (40 -b -6.) 796. When designed to carry less than 25 amperes, how must connections of conductors to fittings be made? Device must be provided with up turned lugs that will grip the conductor between screw and lug, screws having flat washers. Or, by dipping ends of conductors in solder and ap- plying to block terminal with two set screws. (4O-b-6.) Code recommends soldering hi addition "to binding screw fastenings. (40 -b -6.) 797. When does the Code Rule 40-b-6 for car wiring of cable connections, soldering, etc., apply? See Nos. 795-796. On circuits of over 25 volts, and over 5 amperes. ( 4 o-b-6.) OFFICIAL NATIONAL ELECTRICAL CODE 145 Cut-outs, Circuit-breakers and Switches. 798. Is it necessary to enclose switches, such as knife switches, and cut-outs with exposed metal parts? Yes. (40 -c -i.) 799. Is it necessary for switches and cut-outs to be mounted on insulating non-combustible material, such as fiber or asbestos, when not enclosed in iron or steel boxes? Yes. (40 -c- 1.) 800. Is it necessary for a switch or cut-out base to project on all sides, and how much? Yes, 1/2 in. (40-0-1.) 80 1. What kind of cut-outs are required? Approved cartridge or approved "blow-out" type. (40-0-2.) 802. Are single pole quick break or approved magnetic blow-out switches required for over 5 amperes circuit? Yes. (40-0-3.) 803. Are snap, double break, and single pole switches accepted for 5 amperes or less capacity circuits? Yes. (40-0-3.) 804. Must circuit-breakers be of approved type? Yes. (40-0-4.) 805. Is it forbidden to fuse circuits above safe carrying capacity? Yes. (40-0-5.) 806. Is a cut-out required near the current collector for cutting off all current? Yes. (40-0-6.) 807. When a metallic return circuit is used, will circuit- breakers alone, without fuses, be sufficient? Yes, when circuit-breakers are connected to both sides of the circuit. (40-0-6.) Conduits. 808. What particularly small size conduit is acceptable for lighting circuits? Five -sixteenths inch internal diameter, and 1/2 in. external diameter. (4O-d-i.) 809. What small size conduit for heating and air motor circuits may be used? Three-eighths inch internal diameter and 9/16 in. external diameter. (4O-d-i.) 10 146 QUESTIONS AND ANSWERS ON THE 810. Where conduits are exposed to dampness, what must be done? Must be made water-tight. (4o-d-i.) 8 1 1. How must conduits be treated in reference to con- tinuity, entrance of junction boxes and fittings, and in general? In accordance with conduit systems in general under metallic protective systems. See Question No. 321. (40 d-2-3-4-5.) Exceptions per 812 and 838. 812. Must conduit be grounded enclosing conductors con- necting between third-rail shoes on same track? No, must be insulated, (4O-d-4 and 4o-i-2.) 813. Where must all conduit outlets or junction box fittings be substantially fastened? To framework of car. (4o-d-6.) Moulding. 814. Is hardwood moulding permitted where circuits are normally not exposed to moisture? Yes. (40-6-1.) 815. What is the special construction required for the fire-resisting and insulated moulding approved for use? Backing not less than 1/4 in. thick; backing must extend i in. beyond conductor at sides; capping 1/8 in. thick and 3/4 in. extension beyond conductors; joints close. ( 4 o-e-2.) 8 1 6. Must joints be mitered? Yes. (40-6-2.) 817. Are either screws or nails acceptable for fastening moulding in place? Yes. (40-6-2.) 8 1 8. Are two water-proof paint coatings required, both inside and out, on all mouldings? Yes. (40-6-2 and 40-6-3.) 819. Can the backings be omitted from fire-resisting moulding when the surface on which it is placed is at least 1/8 in. insulating material? Yes. (40-6-2.) 820. Are screws required for the backing and capping wooden moulding? Yes. (40-6-3.) OFFICIAL NATIONAL ELECTRICAL CODE 147 Lighting and Lighting Circuits. 821. What is the wattage limit for each individual lamp used? One hundred and twenty -eight watts. (40-f-i.) 822. Are approved receptacles or clusters required at outlets? Yes. (40-f-i.) 823. How must circuits be run? In approved conduit or approved moulding. (4O-f-2.) 824. How must receptacles be fastened on a metal con- duit system? To inside of the conduit box. (40 -f -4.) Exception : sign lights. (40 --3.) 825. Is an insulating bushing necessary around the open- ing in a conduit box cover for a lamp? Yes. ( 4 o-f-4.) 826. How must clusters be insulated from the metal con- duit? By a block of hard wood or fiber or other fire -resist- ing and insulating material. (40 -f -4.) 827. When wooden moulding is used, how must either receptacles or clusters be mounted? See Question No. 826. (4O-f-5.) Heaters and Heating Circuits. 828. Must heaters be approved type? Yes. (40-g-i.) 829. How far from all woodwork must the current-carry- ing part of panel heaters come? Four inches. (4o-g-2.) 830. How far must current-carrying parts of heaters for cross seats be located below the under side of the seat? Six inches, unless i /4 in. fire lining is used (as defined in Question No. 780). In this case, distance may be reduced to 3 in. (40-g-2.) 831. Are truss plank heaters, mounted on 1/4 in. fire lining, with an air space of not less than 1/2 in. between 'back of heater and insulating material, approved? Yes. (40-g-2.) 832. When may knob and tube work be done? When an air space of not less than 2 in. on all sides, 148 QUESTIONS AND ANSWERS ON THE except from the surface wired over, is maintained; con-; ductors may then be supported on porcelain supports mounted on not less than 1/4 in. fire lining, extending at least 3 in. beyond conductors at either side. Supports must raise conductors not less than 1/2 in. from surface wired over, and be not over 12 in. apart. (4o-g-3.) Air Pump Motor and Circuits. 833. Can knob and tube work be used instead of approved metal conduit or approved moulding? Yes, provided supports raise conductors 1/2 in. from surface wired over and are not over 12 in. apart. (4O-h-i.) 834. Must automatic control be installed? Yes, in approved metal box. (4o-h-2.) 835. When air pump and motor are enclosed, is a wooden box acceptable? Yes, when lined with metal of not less than 1/32 in. in thickness. (4O-h-2.) 836. May boxes surrounding automatic controls in air pump and motor serve as outlet boxes in which taps, joints, etc., may be freely made? Yes, when conductors are run in metal conduit. (40-h-2.) Main Motor Circuits and Devices. 837. Must conductors in hood be protected where wires enter car to prevent moisture? Yes. (40-1-1.) 838. Is it necessary for conductors between third-rail shoes on same truck to be supported in approved non- metallic fire-resisting mouldings; or by approved iron con- duit (insulated where supported by approved insulating cleats)? Yes. (40-1-2.) 839. What three methods only are permitted for con- ductors on under side of car, and may connection between controllers and contactors be run otherwise as an exception? First, approved metal conduit systems. See Questions 811-812-813. Second, approved insulating, fire -resisting, moulding. Third, approved cleats supporting every 12 in. OFFICIAL NATIONAL ELECTRICAL CODE 149 Exception: Conductors with flame -proof braided outer cover, connecting controllers, or controllers and con- tactors, may be run as a cable, provided where exposed to weather it is canvas covered by tape or hose, and is taped or sewed at the electrical connections and ends. Conductors without flame -proof outer covering, if surrounded with i/8-in. flame -proof cover, may be used subject to same provisions. All of above kinds of installation under Exception may be run full length of car for main motor circuit and devices. (40-1 -4) 840. How must cables be run above floor of car? Specifically provided in metal conduit or wooden box painted with two coats of flame -proof paint inside; box should be made reasonably water -proof when exposed to water, such as washing of car floor. (40 -i -4.) 841. Must canvas hose or tape or flame-proof material surrounding cables be painted with water-proof insulating materials? Yes. (40-1-4.) 842. Is it required that motors be so drilled on double truck cars that connecting cables can leave motor on side nearest to king bolt? Yes. (40-1-5.) 843. How much air space is required between resistances proper and fire-resisting material of car? Six inches. (40-1-6.) 844. What three methods of insulating resistance are specified? First, supports insulated with non -combustible bush- ings or washers. Second, 2 in. of insulating material between the re- sistances and metal work of the car. Third, mount resistances on hardwood bars supported by iron stirrups with not less than 2 in. insulation surface between foot of resistance and metal stirrup ; entire surface of bar covered with at least 1/8 in. insulating fire lining. Conductor insulation about 6 in. from resistance terminal should be replaced if needed by porcelain bushing or asbestos sleeve. (4O-i-6.) 845. How must controller be raised above platform of car? 150 QUESTIONS AND ANSWERS ON THE By a not less than i in. hardwood block, fitted anc painted to prevent moisture working between it and the platform. (40-1-7.) Lightning Arresters. 846. How is it recommended that lightning arresters placed? Located to protect auxiliary service in addition main motor circuits. (40-]-!.) 847. What is the smallest size ground conductor accej No. 6 B. & S. (4Q-J-2.) GENERAL RULES 848. Are approved, tightly fitting insulating bushin such as porcelain or glass, required where conductors pass j through floors? Yes. (40-k-i.) 849. Is it necessary that such bushings used in passing through floors for conductors or cables, fit closely to same? Yes. (40-k-i.) 850. Is moulding forbidden for concealed work? Code recommends in any car wiring work it shall not be concealed except where readily accessible. (4O-k-2.) 85 1. Is it forbidden to tack conductors into moulding? Code recommends they shall never be tacked into moulding. (4o-k-2.) 852. Is it mandatory that sharp edges in conduit or in moulding be smoothed to prevent injury to conductors? j Yes. Sharp edges in conduit must be avoided. (40-k-4.) Car Houses. 853. Must insulating hanger be used for supporting trol- ley wires? Yes. (41 -a.) 854. How far apart must trolley hangers be placed? So that in case of a break trolley wire will not touch floor. (4i-b.) 855. Is an emergency cut-out switch or two or more switches one for the trolley and one for other currents required, and where must the switch or switches be located? OFFICIAL NATIONAL ELECTRICAL CODE 151 Yes, located outside of building, so that all trolley wire current may be cut at one point. (41 -c.) See also fine print note. (41-0.) Read 858. 856. Is it necessary for the trolley wire to be "dead" when emergency switch is open at all points within 100 ft. of the building? Yes. (41 -c.) 857. Is it obligatory to cut off the current from the build- ing when not needed in the building? Yes. (41 -c.) 858. Must lamps and stationary motors be controlled by separate main switch independent of the main cut-out switch described under Question No. 855? Yes. (41 -d.) Grounded Trolley Circuits. Following questions apply where current for lighting and stationary motors is from an earth return trolley circuit. 859. May light and power be taken from a street railway system which has trolley wires with a ground return in any buildings except electric railroad car houses, power houses, passenger and freight stations, and other railways company buildings? No. (42-a.) 860. Are cut-outs and switches obligatory to cut-off cur- rent from motors or lights? Yes. (41-6, i and 2.) 86 1. Where must controlling cut-outs and switches be cut in? On the non -grounded side. (41-6-1 and 2.) 862. How must rails be bonded? At each joint by a conductor with a capacity at least equal to No. o B. & S. gauge annealed copper wire. (41-6-3.) 863. How must rails be connected to outside ground re- turn circuit? By a not less than No. o B. & S. gauge, copper wire, or equivalent bonding through the track. (41-6-3.) 864. How must lighting and stationary motor circuits be connected? Thoroughly and permanently connected to rails or to wire leading to outside ground return circuit. (41-6-3.) 152 OFFICIAL NATIONAL ELECTRICAL CODE 865. What general Code rules and questions apply for installation of all wiring and apparatus in Railway Systems, except as provided under such questions as 787-827; 832-833; 836; 838-839; 844? Rules and questions for constant potential systems. (4i-g.) See No. 249 and 321. 866. May the feeder distributions center in the building? No. (4i-h.) 867. Is it forbidden to leave cars in electrical connection with the trolley wire in power house? Yes. (41 -i.) Flexible Cord. 868. What type of flexible cord must be used throughout all car-house work? Type P. P. W p. P. A. & H. ( 4 i-f.) SECTION EIGHT MARINE WORK Allowable Capacity of Wires. Generators. Wiring. Control of Freight Departments. Cut-outs. Wattage Limit. Wooden Mouldings. Interior Conduits. Protection of Wires. Portable Conductors. SWITCHBOARDS Switches. Resistance Boxes. FIXTURES Mounting. Wiring of Fixtures. Ceiling Fixtures. Sockets. Signal Lights. Bell or Other Wires. MOTORS INSULATION RESISTANCE 153 SECTION EIGHT MARINE WORK TABLE OF ALLOWABLE CAPACITY OF WIRES B. & S. G. Area actual C. M. No. of strands Size of strands. B. & S. G. Amperes 19 1 288 18 1 624 3 17 16 2,048 2 583 6 15 3,257 14 12 4,107 6 530 12 17 9^016 11,368 7 7 19 18 21 25 14 336 7 17 30 18,081 22,799 7 7 16 15 35 40 30,856 38,912 49,077 19 19 19 18 17 16 50 60 70 60,088 37 18 85 75,776 99 064 37 61 17 18 100 120 124,928 157,563 198 677 61 61 61 17 16 15 145 170 200 250 527 61 14 235 296^387 373 737 91 91 15 14 270 320 413 639 127 15 340 Generators. (Code rule 94.) Dry places, and proof covers required 90. 869. Is it obligatory that frames of generators be insu- lated from bed plates? Yes. (90 -b.) Wiring. 870. Is exposed work allowed? No, except on switchboards, Approved moulding, wood or metal, and conduit required. Exception : Switch- boards and for portables. Also by special permission in dynamo-rooms, per fine print note. (91 -a.) 871. What is the largest solid wire allowed? No. 12 B. & S. (9i-b.) 872. What is the smallest solid wire allowed? 155 156 QUESTIONS AND ANSWERS ON THE No. 14 B. & S. Exception: Fixture wiring, which may be No. 18. (91 -b.) 873. How must splices in conductors or taps be made, and when are they permitted? When necessary splices or taps are permitted, but must be avoided as far as possible; must be made mechan- ically and electrically certain without solder, then soldered; covered with insulating compound equivalent wire insula- tion; further protected by water -proof tape. Whole coated or painted with water-proof compound. Exception to solder- ing joint when approved soldering device is used. (91 -c.) 874. Give requirements and test for wires for moulding work? "Must have an approved insulating covering at least 3/32 in. in thickness and be covered with a substantial waterproof braid. The physical characteristics shall not be affected by any change in temperature up to 200 F. (93 C.). After two weeks' submersion hi salt water at 70 F. (21 C.), it must show an insulation resistance of 100 megohms per mile after three minutes' electrification with 550 volts." (9i -d.) Control of Freight Compartments. 875. Must freight departments be under a separate control? Yes. (97-c.) Cut-outs. 876. Is a water-tight and fire-proof cut-out obligatory connecting directly to the mains in such places as upper deck holes, cargo spaces and fire rooms, and under what conditions? Water-tight and fire-proof cut-outs are recommended, but language of Code is not mandatory in this instance. They are optional when cut-outs apply to circuits requiring not more than 660 watts energy. (98 -b.) Note No. 44: Water-proof cut-outs should be used. Wattage Limit. 877. What is the wattage limit for cut-outs, except for motors, search lights and diving lamps? OFFICIAL NATIONAL ELECTRICAL CODE 157 Six hundred and sixty watts for ultimate dependence on one cut-out. (gS-d.) Wooden Mouldings. 878. What are the requirements for the construction of wooden moulding? Same as for inside wiring in ordinary buildings. See Section 6, Division One. (ioi-6o-26-k to m.) 879. How must moulding be secured when run over rivets, beams, etc.? Backing strip must first be put up and moulding secured to this. (loi-a.) 880. Is it necessary for brass screws to be used in securing capping? Yes. (loi-b.) Interior Conduits. 88 1. What are the requirements for wires for conduit work? Same as for moulding (No. 874.) and for unlined metal conduits, conductors must conform to the specifica- tions given for lined conduits, and in addition have a second outer fibrous covering at least 1/32 hi. in thickness and sufficiently tenacious to withstand the abrasion of being hauled through the metal conduit." (91 -g.) (Type R. D.) 882. Can wires be drawn in conduit before the conduit system mechanical work is completed? No. (gi-h.) 883. Must approved conduit be used instead of moulding wherever wires are exposed to severe mechanical injury; and in coal bunkers, boiler rooms, etc.? Yes. (91 -i.) 884. Is it obligatory that on alternating systems two or more wires must be drawn in the same conduit? Yes. (9i-j.) 885. What are the general requirements for interior con- duits and fittings and other sundries? Same as for interior conduits for wiring on land. See Section 6, Division 2, Code Class "C." Rule 102, Code Class "F." Questions Nos. 321-333 inclusive may apply. 886. How must boxes for centers of distribution and not 158 QUESTIONS AND ANSWERS ON THE affording good electrical connection with the rest of the system be treated? Bonded by means of suitable bond wires properly attached, and with exposed ground connections properly made. (iO2-f.) See questions on grounding for detail. Section 6, Code Class " C," 373-378 inclusive. 887. How many circuits of the same system may one conduit contain? Four 2 -wire and three 3 -wire. Exception: Special permission from insurance department having jurisdiction. (9I-JO Protection of Wires. 888. How must wires passing through water-tight bulk- heads and through all decks be protected? Metallic stuffing tube lined with hard rubber must be used. (91 -e.) 889. In the case of deck tubes, what extra protection must be given to prevent mechanical injury to the metallic stuffing tube? Must be boxed near the deck. (91-6.) 890. Where wires pass through beams and non-water- tight bulkheads, how thick must the required bushing of hard rubber tubing be made? One-eighth inch thick. (91 -f.) Portable Conductors. 891. How many stranded wires are allowed in portable conductors? Two. (92-a.) 892. What is the smallest gauge conductor permitted? Fourteen B. & S. (92-a.) 893. What kind of a covering must a stranded conductor in a portable cable have? Slow -burning, tough braided outer covering. (92-3.) 894. Give description of portable conductors extra re- quirement in thickness of insulation and general make-up over ordinary portables? When exposed to moisture and mechanical injury (as for use on decks, hold and fire rooms) each conductor to have solid insulation at least 1/32 in., protected by tough OFFICIAL NATIONAL ELECTRICAL CODE 159 braid. Two conductors shall then be stranded together, using a jute filling. Whole shall be covered with a layer of flax, either woven or braided, at least 1/32 in. in thickness, and treated with a non-inflammable water -proof compound. (92 -a.) See Table No. 18, Section 9. 895. When a greater conductivity than No. 12 B. & S. gauge is used, what must be the sizes of the wires making up the strands; how shall it be made? Stranded in series of 7, 19, 37, 61, 91, or 127 wires, as may be required. Strand consisting of one central wire ; remainder laid around it concentrically, each layer to be twisted in opposite direction from preceding. (94.) SWITCHBOARDS 896. Can wood be used for main switchboards? No. (95 -a.) 897. What special kinds of insulation and protective cov- ering is required for conductors at switchboard? Flame -proof braided and otherwise as required for moulding or conduit work. (95 -e.) Switches. 898. What special requirements apply for marine switch- boards not mandatory in other classes of work? Must have main cut-out and ammeter for each gen- erator, as well as main switch. Second, volt meter and ground detector. Third, cut-out and switch for each side of circuit leading from board. (95 -c and d.) Note: Switchboard must be made of slate or marble or similar material, free from moisture, and accessible from all sides. (95-a-b.) Section 6, Division Three questions ap- plicable. 899. What kind of special switch is required for marine switchboard? Knife bladed. (97-0.) 900. How must switches on deck and otherwise exposed to dampness be treated? Enclosed in water-tight case. (97-3.) Resistance Boxes. 901. How must resistance boxes not located on switch- board be mounted? 160 QUESTIONS AND ANSWERS ON THE Away from combustible material. (Q6-a.) Code Rule 78 applying. See also Questions Nos. 390-410. in- clusive. For Auto starters read 411 to 418 inclusive. All 4-c (reference) questions apply. FIXTURES Mounting. 902. Give special requirements for mounting fixtures? Blocks made from well seasoned lumber, treated with two coats. white paint or shellac. (99-a.) 903. Are vapor-proof globes obligatory where lamps exposed to dampness? Yes. (99-b.) 904. What special requirement is made for lamps where exposed to mechanical injury? Must be surrounded by a globe which in turn is pro- tected by stout wire guard. (99-c.) Wiring of Fixtures. 905. What special grade of insulation is required fo marine work? Same as portable conductors not exposed to moistur or injury. (99-d.) Type letter P. O. applies. Ceiling Fixtures. 906. What special mechanical provision is required upoi all ceiling fixtures over 2 ft. in length? Must be provided with stay chains. (99-6.) Sockets. 907. What special kind of sockets are required for marin work? Requirements the same as for other classes of worl under same conditions. Read 709 to 732. Signal Lights. 908. Is it obligatory for signal lights to be provided with an approved tell-tale board, located preferably in pilot house, which will immediately indicate a burned-out lamp? Yes. (103 -a.) OFFICIAL NATIONAL ELECTRICAL CODE 161 Bell or Other Wires. 909. Can bell or other wires be run in the same duct as electric lighting or power wires? No. (93 -a.) MOTORS 910. What are the general requirements for motors, al- ternating and direct? Must comply with requirements as indicated under questions, Section i, Motors, and Code Class "A." Must also be thoroughly insulated. On hoists and winches, must be insulated from bed plates by hard rubber fiber or other similar insulating material. (104 -a and b.) General requirements demanding name plate, water- proof cover, and other details same as in Section One. INSULATION RESISTANCE "The wiring in any vessel must test free from grounds; i.e., the complete installation must have an insulation be- tween conductors and between all conductors and the ground (not including attachments, sockets, receptacles, etc.) of not less than the following: Up to 25 amperes 800,000 ohms. Up to 50 amperes 400,000 ohms. Up to 100 amperes 200,000 ohms. Up to 200 amperes 100,000 ohms. Up to 400 amperes 50,000 ohms. Up to 800 amperes 25,000 ohms. Up to 1,600 amperes 12,500 ohms. "All cut-outs and safety devices in place in the above. "Where lamp sockets, receptacles and electroliers, etc., are connected, one-half of the above will be required." (105.) 11 SECTION NINE In this section will be found general information upon approved wire markings and the requirements for wire and material as demanded by the Code. The 1911 requirements have raised the standard of rubber insulation for wire materially, requiring 20 per cent, of rubber in the compound. For mechanical and chemical tests of the compound the Underwriters Laboratories, 131 East Ohio street, Chicago, 111, have provided special specifications. Read also 50-g-h- and i of the Code. The Underwriters' Laboratories now has approved coils tagged at factories before shipment. Many of the tables from the 1911 Code are assembled here for convenient reference. The wire-conduit table has been added as a matter of general interest. 163 CONTENTS pproved Wire Markings. Type Letters of Wire. Varnished Cambric Cabl Table No. 1. Allowable capacity of wire. Table No. 2. Slow-burning weather-proof wire require- ments. 3. Slow-burning wire requirements. 4. Weather-proof wire requirements. 5. Insulation tests for 0-600 volts R. C. wire. Table No. Table No. Table No. Table No. 6. Insulation tests for 601-3500 volts R. C. wire. Table No. 7. Insulation tests for 3500-7000 volts R. C. wire. Table No. 8. Requirements for conduit wires. Type let- ters R. D. Table No. 9. Requirements for fixture wires. Type letters F. 32-F. 64. Table No. 10. Requirements for flexible cord. Type let- ter C. Table No. 11. Requirements for flexible cord. Type let- ter P. Table No. 12. Requirements for flexible cord. Type letter P. Wp. Table No. 13. Requirements for flexible cord. Type letter P. O. Table No. 14. Requirements for flexible cord for portable heating devices. Type letter H. Table No. 15. Requirements for armored portable cord. Type letter P. A. Table No. 16. Requirements for theater cables. Table No. 17. Requirements for elevator cables. Table No. 18. Requirements for portable conductors for marine work. Table No. 19. Dimensions of approved tubes. Table No. 20. Sizes of approved knobs. Table No. 21. Spacings of approved cleats. Table No. 22. Sizes and weights of unlined conduits. Table No. 23. Spacings for cut-outs. Table No. 24. Rating of plug, cartridge, scalable service and meter cut-outs. 165 166 QUESTIONS AND ANSWERS ON THE Table No. 25. Dimensions of National Electrical Code ridge enclosed fuses. Table No. 26. Spacings for enclosed fuse terminals. Table No. 27. Spacings for knife switches. Table No. 28. Spacings for switch and cut-out terminals. Table No. 29. Switch and bus spacings for tablets and panel boards. Table No. 30. Breaking capacity of circuit-breakers. Table No. 31. Wiring in buildings insulation resistance test. Table No. 32. Number of wires in rigid conduit. WIRE MARKINGS AND TYPE LETTER. When received from factory approved wire must have distinctive marking entire length of coil; also be tagged or marked. " 1. The maximum voltage at which the wire is designed to be used. "2. The words ' National Electrical Code Standard.' " 3. Name of the manufacturing company and, if desired, trade name of the wire. " 4. Month and year when manufactured. " 5. The proper type letter for the particular style of wire or cable as given for each type of insulation in Code rules 50 to 57 inclusive. "Wires described under Table No. 4 need not have distinctive marking, but are to be tagged. VARNISHED CAMBRIC CABLE. The April, 1912, List of Fittings says: "Varnished cambric cable insulation consisting of cambric with protecting covering of braid or a lead sheath. Present installation rules do not recognize a material 9f this character. Laboratory tests show favorable results and limited field experience to date is satisfactory. It is, therefore, recom- mended that local inspection departments having iurisdiction allow the use of the cable as the equivalent to a rubber covered conductor in such quantities and location as will, in their judg- ment, afford information sufficient to warrant consideration of change in present rules." The Underwriters' Laboratories type letter marking is as follows: For use on Type letter 0-600 volts R. S. 0-1500 R. S. 15 0-2500 R. S. 25 0-3500 R. S. 35 OFFICIAL NATIONAL ELECTRICAL CODE 167 For use on Type letter 0-5000 R. S. 50 0-7000 R. S. 70 Slow-burning weather-proof . S. B. W. Slow-burning S. B. Weather-proof W. R. Conduit wire R. D. Armored cable A. C. Lead-covered cable R. S. L. Fixture wires { ^ Flexible cords For pendant lamps, free in air C. For pendants in damp places C. Wp. For portables P. For portables in damp places P. Wp. For portables in dwellings, etc. P. O. Armored portable P. A. Portable cord for heating apparatus H. Theater stage cable T. Theater border cable B. Elevator lighting and control cable E. Marine portable No type letter. TABLE NO. i Table B of Table No. 1 may be used for large starting cur- rent alternating type motors, where rubber insulation is used, unless a time element circuit-breaker is installed as the only protector. Example: A No. 5 B. & S. wire, Table A (rubber-cov- ered), is allowed 54 amperes for all ordinary work such as direct-current motors. When the same wire is used for alternating current motors of large starting current the same wire (rubber-covered) is allowed 77 amperes under Table B. The selection of the proper size of wire for large alter- nating current motors is at the present time a matter of individual treatment of each case, according to its start- ing load, and using Table B and rubber-covered wire. Where circuit-breakers are used on alternating-current work for motor protection they must be set not over 30 per cent, above allowable carrying capacity of the wire unless fuses protecting circuit are also used. 168 QUESTIONS AND ANSWERS ON THE TABLE No. 1 ALLOWABLE CAPACITY OF WIRES Table A Table B B. & S. G. Rubber insulation Amperes Other insulations Amperes Circular mils 18 3 5 1,624 16 6 8 2,583 14 12 16 4,107 12 17 23 6,530 10 24 32 10,380 8 33 46 16,510 6 46 65 26,250 5 54 77 33,100 4 65 92 41,740 3 76 110 52,630 2 90 131 66,370 1 107 156 83,690 127 185 105,500 00 150 220 133,100 000 177 262 167,800 0000 210 312 211,600 Circular mils 200,000 200 300 300,000 270 400 40o]oOO 330 500 500,000 390 590 600,000 450 680 700^000 500 760 800,000 550 840 900,000 600 920 1,000,000 650 1,000 1,100,000 690 1,080 1,200,000 730 1,150 1,300,000 770 1,220 1,400,000 810 1,290 1,500,000 850 1,360 1 ,600,000 890 1,430 1 700 000 930 1,490 1 800 000 970 1,550 1 900 000 1,010 1,610 2,000,000 1,050 1,670 "Aluminum wire is rated 84 per cent, of copper, same insulations." The lower limit is specified for rubber-covered wires to prevent gradua deterioration of the high insulations by the heat of the wires, but not from fear of igniting the insulation. The question of drop is not taken into consideration in the above tables. fi8-a.) Copper conductors must be tinned. (50-a.) OFFICIAL NATIONAL ELECTRICAL CODE 169 TABLE No. 2 SLOW-BURNING WEATHER-PROOF WIRE Type Letters S. B. W. This wire is not as burnable as " weather-proof " nor as subject to ftening under heat. It is not suitable for outside work. a. The insulation must consist of two coatings, one to be -proof in character and the other to be weather-proof, fire-proof coating must be on the outside and must comprise about six-tenths of the total thickness of the wall. The completed covering must be of a thickness not less than that given in the following table: B. & S. gage Thickness 14 to 8 3/64 in. 7 to 2 1/16 in. 1 to 0000 5/64 in. Circular mils 250,000 to 500,000 3/32 in. 500,000 to 1,000,000 7/64 in. Over 1,000,000 1/8 in. Measurements of insulating wall are to be made at the thinnest portion. 6. The fire-proof coating shall be of the same kind as that required for "slow-burning wire," and must be finished rith a hard, smooth surface. c. The weather-proof coating shall consist of a stout braid, applied and treated as required for "weather-proof wire." (5i-a-b-c.) 170 QUESTIONS AND ANSWERS ON THE TABLE No. 3 SLOW-BURNING WIRE Type Letters S. B. a. The insulation must consist of three braids of cotton or other thread, all the interstices of which must be filled with the fire-proofing compound or with material hav- ing equivalent resisting and insulating properties. The outer braid must be specially designed to withstand abrasion, and its surface must be finished smooth and hard. The completed covering must be of a thickness not less than that given in the Table 2. The solid constituent of the fire-proofing compound must not be sus- ceptible to moisture, and must not burn even when ground in an oxi- dizable oil, making a compound which, while proof against fire and moisture, at the same time has considerable elasticity, and which when dry will suffer no change at a temperature of 250 F. (121 C.)t and which will not burn at even a higher temperature. This is practically the old so-called "underwriters" insulation. It ia especially useful in hot, dry places where ordinary insulations would perish, and where wires are bunched, as on the back of a large switch- board or in a wire tower, so that the accumulation of rubber insulation would result in an objectionably large mass of highly inflammable material. (52-a.) TABLE No. 4 WEATHER-PROOF WIRE Type Letters W. R. a. The insulating covering shall consist of at least three braids, all of which must be thoroughly saturated with a dense moisture-proof compound, applied in such a manner as to drive any atmospheric moisture from the cotton braid- ing, thereby securing a covering to a great degree water- proof and of high insulating power. This compound must not drip at 160 F. (71 C.). The thickness of insulation must not be less than that given in the Table 2, and the outer surface must be thoroughly slicked down. This wire is for use outdoors, where moisture is certain and where fire- proof qualities are not necessary. (S3-a.) OFFICIAL NATIONAL ELECTRICAL CODE 171 TABLE No. 5 TESTS ON COMPLETED LENGTHS 0-600 VOLT CLASS Type Letters R. S. Size Thickness in 64ths inches Megohms per mile after 12 hrs. immersion Voltage test 1 minute 14 3/64 300 1,500 12 3/64 250 1,500 10 3/64 225 1,500 8 3/64 200 1,500 6 1/16 200 2,000 4 1/16 150 2,000 2 1/16 125 2,000 1 5/64 150 2,500 5/64 125 2,500 00 5/64 125 2,500 000 5/64 100 2,500 0000 5/64 100 2,500 225,000 C. M. 3/32 100 3,000 300,000 C. M. 3/32 100 3,000 400,000 C. M. 3/32 100 3,000 500,000 C. M. 3/32 100 3,000 600,000 C. M. 7/64 100 3,500 700,000 C. M. 7/64 100 3,500 800,000 C. M. 7/64 100 3,500 900,000 C. M. 7/64 100 3,500 1,000,000 C. M. 7/64 100 3,500 1,250,000 C. M. 1/8 100 3,500 1,500,000 C. M. 1/8 75 3,500 1,750,000 C. M. 1/8 60 3,500 2,000,000 C. M. 1/8 50 3,500 172 QUESTIONS AND ANSWERS ON THE TABLE No. 6 MAXIMUM OPERATING VOLTAGE 1500 V. Type Letters R. S. 15 Size Thickness insulation. Insulation resistance niegoh ms one minute 60 F Volts test for one minute B & S. Gauge 14-8 1/16 600 4 000 7-2 5/64 300 4 000 1-0000 3/32 200 4 000 C. M. 225,000-500,000 7/64 175 4 000 525,000-1 ,000,000 1/8 150 4 000 Over 1,000,000 9/64 100 4 000 MAXIMUM OPERATING VOLTAGE 2500 V. Type Letters R. S. 25 (5o-f and e.) Size Thick ins. Ins. res. meg. Volts test B. & S. Gauge 14-8 3/32 700 6 250 7-2 3/32 350 6 250 1-0000 7/64 250 6 250 C. M. 225,000-500,000 1/8 200 6,250 525,000-1,000,000 Over 1,000,000 9/64 10/64 175 125 6,250 6,250 MAXIMUM OPERATING VOLTAGE 3500 V. Type Letters R. S. 35 (5o-f and e.) Size Thick ins. Ins. res. meg. Volts tests B. & S. Gauge 14-8 4/32 850 8 750 7-2 4/32 450 8750 1-0000 4/32 300 8,750 C. M. 225,000-500,000 9/64 225 8,750 525,000-1,000,000 10/64 200 8,750 Over 1 000 000 11/64 150 8,750 (50-1 and e.) OFFICIAL NATIONAL ELECTRICAL CODE 173 TABLE No. 7 MAXIMUM OPERATING VOLTAGE 5000 V. Type Letters R. S. 50 Size Thick ins. Ins. res. meg. Volts test B. & S. Gauge 14-8 6/32 1 000 12 500 7-2 6/32 650 12 500 1-0000 C. M. 225,000-500,000 525,000-1,000,000 Over 1,000,000 6/32 6/32 6/32 7/32 450 300 225 175 12,500 12,500 12,500 12 500 (5o-f and e.) MAXIMUM OPERATING VOLTAGE 7000 V. Type Letters R. S. 70 Tns Size Thick reg. Volts ms. test meg. B. & S. Gauge 14-8 8/32 1,200 17,500 7-2 8/32* 800 17 500 1-0000 8/32 550 17 500 C. M. 225,000-500,000 . 8/32 400 17 500 525,000-1,000,000 8/32 275 17 500 Over 1,000,000 9/32 200 17 500 (5o-f and e.) 174 QUESTIONS AND ANSWERS ON THE EH . HH CO Li) EH Q o ^:> * fcf o ojS I ^OH? 03 i t> (Srtg H g| oi s gl d d "d'B -a|| .93 M T3 gj |S| "S fl e 1 *s ! 1 ' "- co S g -^ A S * ^A^ ^ d I I 1 1 -* ? dll S 1 ^-II-I.S M o o.<;-ico.g d o o, t o 03 S 6 . OFFICIAL NATIONAL ELECTRICAL CODE 179 o r -1 g - T3 11 g| - o W o ^ Z M fe II c <3 S 4 O J3 " O ft PI l|l| afll c a ** CJ "" 0) 5? 'rt T3 .2 > g g^i ^S 8 ^1 4S w ^ T3 O /n 11 II ^ a g CO TJ - 73 V . 2 "S 2 A .8 & | .2 3 | ^ N J g-^^-^ & 3 ofo^ g 6o^ S J g n w "8 First protection 35 -S s-^ol i *> " -? 1 2 4 1 ji 1 !!!! O ^3 OT g ft O 03 1 S -i 8 i"o 1 CO 5 o S g ^ 3 si*!" 1 1a sS Illll Is CQ II PQ 1 fl 00 2 o QUESTIONS AND ANSWERS ON THE c 5*5 S J | J2 3 PH EH 8 | P5 1 First protection IS^J iid .^81 8-g 1 - 2^-8 2 HIl 111 w 3-i 8 & S* 8 J- 2 ^ ^ 1 1 I- 03 CO f**- | * " a S "o 6 5 fc ^ S W a 2 cti i si pq ' -2 ' 3 H 00 8 6 OFFICIAL NATIONAL ELECTRICAL CODE 181 tf SH _. ' O 1 1 182 QUESTIONS AND ANSWERS ON THE DQ O a 3 ^ ^ w Q 3 5 g ls 1 1 1 S3 xi > a S is | S3 | 1 gfl 1 1 i| 1 111 -Soi. "I * ij ^ 1-1 1 53 J ^^^'^H^ a o3 1 Jlx's I.Sx'i o K.S^-i oi^co 3 OQ 8 3 .2 cj pq M g o 3 . . . | 1 II g-S^ -LS -2 > o 2 'V M S 1 R'llj s mill 11 M II 1 -2 S3 .z s 5 ^ -p o PQ ^?^ 1 1 DO S N 3 pq '3 '3 "O 00 S .-1 O 6 - 55 OFFICIAL NATIONAL ELECTRICAL CODE 183 E 5 PH 02 g O W H fe S Q 3 ^ H P^ ^ EH ^ g P. W OH PQ 1 3 ir tec I I a i II H 8 o 2l 8 & I 184 QUESTIONS AND ANSWERS ON THE 03 | "? S i ^ ! liNl! is O i i |5 3 1 e 1 refers to ti 5 H 8^S g-o 8 g I i rotection I5ij|i I 14 ft | lll^l P 1 1 |^ 1 e 1 1 O d .^ a d o H H I'SiB I 1 | ||.a I -+ i i *H ? M 111" !' d fc 1 p 3 c s3 PS s a^ S gl d 3 o &S ll I 5 oo S 3 1*2* J ?' 3 H P feH 8 ft r 1 * 1 3 r i S r T 0^2 O Q- ^-i ^ W -fJ O c3 O ro I E 1 1 3 K> fcfl C 3 1-1 S pq I o | PH a i a tf as! . t-H 40 O PH 'd '" ^3 S 00 5Q 1 o fc M OFFICIAL NATIONAL ELECTRICAL CODE 185 1 9 | c "' 3 I 1 1 1 s c5 i 83 1 II QQ 1 1 & I 2 > 1 a C^ r{ Q -a 2 | * 9 o a *j f X S g e 02 PQ ^ 8 A ^ .a 1 ..s ^ ..S3 TABLE No. 15 ARMORED PORTABLE TYPE LETTERS P. A. [Minimum requirements] Insulation Homogeneous ru compound dry places 1/32 in damp places 3/64 Same as above a; dry places 3/64 in damp places 3/64 protection 3% 1 ||||| I 4 8 ^ o " 3" B cj o > 8 p.^ 1 i H3 f 1 ^ S^ e 5 -S ^ 2 '2 H ^G ? S cfl 188 QUESTIONS AND ANSWERS ON THE 55 8 g II a s Illl ^S SI C " C ? a .: S3 o o-o ft a "2 El It g 8 3 "w 1 OFFICIAL NATIONAL ELECTRICAL CODE 189 I fi* J a l 3 * 111 i i.s a aa 73 Illlilj sf-s'S- o o> 3 3 o ^ fe d c ** o > .2 O T3 t, O -*3 ill! llll! J3 3 2 ^ O T3 -Q J2 w o d -*J 1 8 t^ S ^ 6 . 190 QUESTIONS AND ANSWERS ON THE TABLE No. 19 Tubes. Dimensions of walls and heads must be at least as great as those given in the following table: Diameter of hole External diameter Thickness of wall External diameter of head Length of head 5/16 in. 9/16 in. 1/8 in. 13/16 in. 1/2 in. 3/8 in. 11/16 in. 5/32 in. 15/16 in 1/2 in. 1/2 in. 13/16 in. 5/32 in. 1 3/16 in. 1/2 in. 5/8 in. 15/16 in. 5/32 in. 1 5/16 in. 1/2 in. 3/4 in. 1 3/16 in. 7/32 in. 1 11/16 in. 5/8 in. lin. 1 7/16 in. 7/32 in. 1 15/16 in. 5/8 in. 1 1/4 in. 1 13/16 in. 9/32 in. 2 5/16 in. 5/8 in. 1 1/2 in. 2 3/16 in. 11/32 in. 2 11/16 in. 3/4 in. 1 3/4 in. 2 9/16 in. 13/32 in. 3 1/16 in. 3/4 in. 2 in. 2 15/16 in. 15/32 in. 3 7/16 in. 3/4 in. 2 1/4 in. 3 5/16 in. 17/32 in. 3 13/16 in. 1 in. 2 1/2 in. 3 11/16 in. 19/32 in. 4 3/16 in. 1 in. An allowance of 1/64 in. for variation in manufacturing will be per- mitted, except in the thickness of the wall. (6i-d.) OFFICIAL NATIONAL ELECTRICAL CODE 191 TABLE No. 20 Knobs. Must be so constructed as to separate the wire at least 1 in. from the surface wired over, and also conform to the following minimum dimensions: Size of base, inches Solid knobs, Split fe^ifeMf 4t( Ip Size of wire groove, inches knobs, thickness of cap, Square knobs inclusive Circular knobs, or single wire cleats inches from top diameter Depth Diam- eter of wire groove Width Length 14-10 1 1/8 3/4 1 3/4 3/16 1/4 3/8 8-4 1 1/2 7/8 2 5/16 5/16 5/8 2-00 2 1 21/4 7/16 5/8 5/8 )00-300,000 C. M. 21/2 1 1/8 23/4 7/16 25/32 7/8 400,000- 1,000,000 3 1 3/8 33/4 5/8 1 1/4 1 C. M. (6 4 -e.) 192 QUESTIONS AND ANSWERS ON THE TABLE No. 21 Cleats. Must conform to the spacings given in the following table: Voltage 0-300 Distance from wire to surface 1/2 in. Distance between wires 2 1/2 in. This rule will not be interpreted to forbid the placing of the neutral of a three-wire system in the center of a three- wire cleat where the difference of potential between the outside wires is not over 300 volts, provided the outside wires are separated 21/2 in. (62 -e.) TABLE No. 22 WEIGHTS AND DIMENSIONS OF UNLINED, RIGID METAL CONDUIT. Finished conduit to have weight per 100 ft. not less than that given in the following table: Trade size, inches Approx. internal diameter, inches Min. thickness of wall, inches Wt. per 100 ft. Ib. 1/2 .62 .100 75 3/4 .82 .105 104 1 1.04 .125 152 1 1/4 1.38 .135 209 1 1/2 1.61 .140 250 2 2.06 .150 350 2 1/2 2.46 .200 535 3 3.06 .210 710 (58-j.) OFFICIAL NATIONAL ELECTRICAL CODE 193 TABLE No. 23 SPACINGS FOR OPEN LINK CUT-OUTS Only Slate and Marble Base Approved Minimum separation of nearest metal parts of opposite polarity Minimum break- distance Not over 125 volts 10 amperes or less 11100 amperes 3/4 in. 1 in 3/4 in. 3/4 in 101-300 amperes. . 1 in 1 in 301-1,000 amperes Not over 250 volts 10 amperes or less 11100 amperes 11/4 in. 11/2 in. 1 3/4 in. 1 1/4 in. 1 1/4 in. 1 1/4 in. 101-300 amperes 2 in 1 1/2 in 301-1 000 amperes 2 1/2 in 2 in (67-J-) TABLE No. 24 STANDARD PLUG OR CARTRIDGE CUT-OUTS Not over 250 Volts Not over 600 Volts 0-30 amperes. 0-30 amperes. 31-60 amperes. 31-60 amperes. 61-100 amperes. 61-100 amperes. 101-200 amperes. 101-200 amperes. 201-400 amperes. 201-400 amperes. 401-600 amperes. Scalable Service and Meter Cut-outs Not over 250 Volts Not over 600 Volts 0-31 amperes 0-30 amperes 31-60 amperes 31-60 amperes 61-100 amperes 61-100 amperes 101-200 amperes 101-200 amperes (67-0.) 13 194 QUESTIONS AND ANSWERS ON THE TABLE DIMENSIONS OF THE NAT STANDARD CARTRID FORM 1. CAETRIDGE FUSE FERRULE CONTACT Voltage A B C Rated capacity Amperes Length over terminals. Inches Distance between contact clips. Inches Width of contact clips. Inches Not over 250. . . 0-30 31-60 I' 1 1 3/4 1/2 5/8 61-100 101-200 201-400 401-600 M 57/3 5 7 1/8 8 85/8 fe 103/8 4 4 1/2 5 6 7/8 1 1/4 1 3/4 2 1/8 Not over 600. . . 0-30 31-60 1 5 5 1/2 4 4 1/4 1/2 5/8 7/8 1 1/4 1 3/4 61-100 101-200 201-400 Cartridge fuse (ferrule contact). 0-30 31-60 Amps. Amps. 61-100 Amps. 101-200 Amps. 201-400 Amps. Cartridge fuse (knife blade contact) (68-f.) TABLE No. 27 SWITCH SPACINGS AND SPECIFICATIONS [CODE TABLE I] Not over 125 volts D. C. and A. C. For Switchboards and Panel Boards. KNIFE SWITCH SPACINGS Minimum separation Minimum break- of nearest metal distance parts of opposite polarity 10 amperes 3/4 in. 1/2 in. 30 amperes 1 in. 3/4 in. 60 amperes 1 1/4 in. 1 in. This 10-ampere switch must have ample metal for stiffness, and to prevent rise in temperature of any part of more than 50 degrees Fahrenheit (28 degrees Centigrade) when carrying 30 amperes, the contacts being arranged so that a thoroughly good bearing at every point is obtained with contact surface advised for pure copper blades of about 0.4 square inch. OFFICIAL NATIONAL ELECTRICAL CODE 197 [CODE TABLE II] Not over 125 volts D. C. and A. C. For individual switches: 30 amperes 1 1/4 in. 1 in. 60 and 100 amperes 1 1/2 in. 1 1/4 in. 200 and 300 amperes 2 1/4 in. 2 in. 400 and 600 amperes 2 3/4 in. 2 1/2 in. 800 and 1,000 amperes 3 in. 2 3/4 in. The 300-ampere switch must not be equipped with cut-out terminals. [CODE TABLE III] 250 volts only D. C. and A. C. For all switches : 30 amperes 1 3/4 in. 11/2 in. [CODE TABLE IV] Not over 250 volts D. C. nor over 500 volts A. C. For all switches: 30, 60 and 100 amperes 21/4 in. 2 in. 200 and 300 amperes 2 1/2 in. 2 1/4 in. 400 and 600 amperes 2 3/4 in. 2 1/2 in. 800 and 1,000 amperes 3 in. 23/4 in. The 30-ampere switch must have ample metal to prevent rise in temperature of any part of more than 50 degrees Fahrenheit (28 degrees Centigrade) when carrying 60 amperes, the contacts being arranged so that a thoroughly good bearing at every point is obtained with contact surfaces advised for pure copper blades of about 0.8 square inch. The 300-ampere switch must not be equipped with cut- out terminals. Cut-out terminals on switches for over 250 volts must be designed and spaced for 600- volt fuses. 198 QUESTIONS AND ANSWERS ON THE [CODE TABLE V] Not over 600 volts D. C. and A. C. For all switches: 30 and 60 amperes 4 inch 3 1/2 100 amperes 4 1/2 " 4 The 30-ampere switch must have ample metal to prevt rise in temperature of any part of more than 50 de Fahrenheit (28 degrees Centigrade) when carrying 60 ampc the contacts being arranged so that a thoroughly good bes at every point is obtained with contact surfaces advised pure copper blades of about 0.8 square inch. Auxiliary breaks or the equivalent are recommended fc D. C. switches designed for over 250 volts, and must be vided on D. C. switches designed for use in breaking current greater than 100 amperes at a voltage of over 250. For three- wire direct current and three- wire single phf systems the separations and break distances for plain three- pole knife switches must not be less than those required in the above table for switches designed for the voltage between the neutral and outside wires. [65-k, and April, 1912, List of Fittings.] TABLE No. 28 SPACINGS FOR KNIFE SWITCH CUT-OUT TERMINALS Not over 600 volts D. C. and A. C. For all switches : 30 and 60 amperes 4 in. 100 amperes 4 1/2 in. 3 1/2 in 4 in. (65-k.) TABLE No. 29 SWITCH AND Bus SPACINGS FOR TABLETS AND PANEL BOARDS The following minimum distance between bare live metal parts (busbars, etc.) must be maintained: Between parts of opposite polarity, Between parts of except at switches and link fuses. same polarity. When mounted on When held free in At link the same surface. air. fuses. Not over 125 volts, 3/4 in. 1/2 in. 1/2 in. Not over 250 volts, 1 1/4 in. 3/4 in. 3/4 in. Not over 600 volts, 2 in. 1 3/4 in. At switches or enclosed fuses, parts of the same polari may be placed as close together as convenience in handli will allow. OFFICIAL NATIONAL ELECTRICAL CODE 199 It should be noted that the above distances are the minimum allowable, and it is urged that greater distances be adopted wherever the conditions will permit. The spacings given in the first column apply to the branch conductors where enclosed fuses are used. Where link fuses or knife switches are used, the spacings must be at least as great as those required by Nos. 65 and 67 (Tables 23 and 27). The spacings given in the second column apply to the distance between the raised main bars and between these bars and the branch bars over which they pass. The spacings given in the third column are intended to prevent the melting of a link fuse by the blowing of an adjacent fuse of the same polarity. Panel boards of special design in which the insulation and separation between busbars and between other current- carrying parts is secured by means of barriers or insulating materials instead of by the spacings given above, must be submitted for special examination and approval before being used. (69-b.) Marking. Must be marked where the marking can be plainly seen when installed, with the name or trade-mark of the manu- facturer and the maximum capacity in amperes and the voltage for which the board is designed. (69-0.) TABLE No. 30 ClRCUITBREAKER TEST Must successfully operate three times with two minute intervals intervening without incapacitating the breaker, the conditions of testing current to be as given in the follow- ing table: (66 -c.) Per cent, of voltage Minimum available Current rating of breakers to 100 amperes 101 to 300 amperes drop in test circuit with rated current flowing 2 3 capacity of supply system not including overload capacity 1000 amperes 3000 amperes 400 amperes. 4 4000 amperes 500 amperes 5 5000 amperes (66-c.) 200 QUESTIONS AND ANSWERS ON THE TABLE No. 31 INSULATION TEST 550 VOLTS OR LESS The wiring in any building must test free *rom grounds; i.e., the complete installation must have an insulation between conductors and between all conductors and the ground (not including attachments, sockets, receptacles, etc.) not less than that given in the following table: Up to 5 amperes 4,000,000 ohms Up to 10 amperes 2,000,000 ohms Up to 25 amperes 800,000 ohms Up to 50 amperes 400,000 ohms Up to 100 amperes 200,000 ohms Up to 200 amperes 100,000 ohms Up to 400 amperes 50,000 ohms Up to 800 amperes 25,000 ohms Up to 1600 amperes 12,500 ohms The test must be made with all cut-outs and safety devices in place. If the lamp sockets, receptacles, elec- troliers, etc., are also connected, only one-half of the resist- ances specified in the table will be required. (88.) OFFICIAL NATIONAL ELECTRICAL CODE 201 TABLE No. 32 NUMBER OF WIRES IN RIGID CONDUIT, Following table is inserted for convenience in estimating sizes conduit for a given number and sizes of wires. It is not a Code requirement, except in so far as wires and con- ductors must be installed without abrasion of the insulation RULES FOR RESUSCITATION FROM ELECTRIC SHOCK Recommended by Commission on Resuscitation from Electric Shock COURTESY NATIONAL ELECTRIC LIGHT ASSOCIATION 203 COMMISSION ON RESUSCITATION FROM ELECTRIC SHOCK DR. W. B. CANNON, Chairman Professor of Physiology, Harvard University DR. GEORGE W. CRILE Professor of Surgery, Western Reserve University DR. YANDELL HENDERSON Professor of Physiology, Yale University DR. S. J. MELTZER Head of Department of Physiology and Pharmacology, Rockefeller Institute for Medical Research DR. EDW. ANTHONY SPITZKA Director and Professor of General Anatomy, Danie, Baugh Institute of Anatomy, Jefferson Medical College MR. W. C. L. EGLIN Past-President, National Electric Light Association DR. A. E. KENNELLY Professor of Electrical Engineering, Harvard University DR. ELJHU THOMSON West Lynn, Mass. MR. W. D. WEAVER, Secretary Editor, Electrical World COPYRIGHT, 1912 National Electric Light Association 204 TREATMENT FOR ELECTRIC SHOCK An accidental electric shock usually does not kill at once, but may only stun the victim and for a while stop his breathing. The shock is not likely to be immediately fatal, because : (a) The conductors may make only a brief and imperfect contact with the body. (6) The skin, unless it is wet, offers high resistance to the current. Hope of restoring the victim lies in prompt and continued use of artificial respiration. The reasons for this statement are: (a) The body continuously depends on an exchange of air, as shown by the fact that we must breathe in and out about fifteen times a minute. (6) If the body is not thus repeatedly supplied with air, suffocation occurs. (c) Persons whose breathing has been stopped by electric shock have been reported restored after artificial respiration has been continued for approximately two hours. The Schafer, or "prone pressure" method of artificial respiration, slightly modified, is illustrated and described -in the following resuscitation rules. The advantages of this method are: (a) Easy performance ; little muscular exertion is required. (6) Larger ventilation of the lungs than by the supine method. (c) Simplicity; the operator makes no complex motions and readily learns the method on first trial. (d) No trouble from the tongue falling back into the air passage. (e) No risk of injury to the liver or ribs if the method is executed with proper care. A id can be rendered best by one who has studied the rules and has learned them by practice on a volunteer subject. 205 INSTRUCTIONS FOR RESUSCITATION FOLLOW THESE INSTRUCTIONS EVEN IF VICTIM APPEARS DEAD I. Break the Circuit Immediately 1. With a single quick motion separate the victim from the live conductor. In so doing avoid receiving a shock yourself. Many have, by their carelessness, received injury in trying to disconnect victims of shock from live conductors. OBSERVE THE FOLLOWING PRECAUTIONS (a) Use a dry coat, a dry rope, a dry stick or board, or any other dry non-conductor to move either the victim or the wire, so as to break the electrical contact. Beware of using metal or any moist material. The victim's loose clothing, if dry, may be used to pull him away; do not touch the soles or heels of his shoes while he remains in contact the nails are dangerous. (6) If the body must be touched by your hands, be sure to cover them with rubber gloves, mackintosh, rubber sheeting or dry cloth; or stand on a dry board or on some other dry insulating surface. If possible, use only one hand. If the victim is conducting the current to ground, and is convulsively clutching the live conductor, it may be easier to shut off the current by lifting him than by leaving him on the ground and trying to break his grasp. 2. Open the nearest switch, if that is the quickest way to break the circuit. 3. If necessary to cut a live wire, use an ax or a hatchet with a dry wooden handle, or properly insulated pliers. n. Send for the Nearest Doctor This should be done without a moment's delay, as soon as the accident occurs, and while the victim is being removed from the conductor. The Doctors entered on page 205 are recommended: 206 INSTRUCTIONS FOR RESUSCITATION 207 Telephone Call. Name Address Telephone Call. Name Address Telephone Call Name Address Telephone Call 208 INSTRUCTIONS FOR RESUSCITATION in. Attend Instantly to Victim's Breathing (1) As soon as the victim is clear of the live conductor, quickly feel with your finger in his mouth and throat and remove any foreign body (tobacco, false teeth, etc.) Then begin artificial respiration at once. Do not stop to loosen the patient's clothing; every moment of delay is serious. (2) Lay the subject on his belly, with arms extended as straight forward as possible, and with the face to one side, so that the nose and mouth are free for breathing (see Fig. 1). Let an assistant draw forward the subject's tongue. FIG. 1. Inspiration; Pressure Off. If possible, avoid so laying the subject that any burned places are pressed upon. Do not permit bystanders to crowd about and shut off fresh air. (3) Kneel straddling the subject's thighs and facing his head; rest the palms of your hands on the loins (on the muscles of the small of the back)/ with thumbs nearly touching each other, and with fingers spread over the lowest ribs (see Fig. 1). (4) With arms held straight, swing forward slowly so that the weight of your body is gradually brought to bear upon the subject (see Fig. 2). This operation, which should take from two to three seconds, must not be violent internal organs may be injured. The lower part of the chest and also the abdomen are thus compressed, and air is forced out of the lungs. INSTRUCTIONS FOR RESUSCITATION 209 (5) Now immediately swing backward so as to remove the pressure, but leave your hands in place, thus returning to the position shown in Fig. 1. Through their elasticity, the chest walls expand and the lungs are thus supplied with fresh air. (6) After two seconds swing forward again. Thus repeat deliberately twelve to fifteen times a minute the double movement of compression and release a complete respira- tion in four or five seconds. If a watch or a clock is not visible, follow the natural rate of your own deep breathing swinging forward with each expiration, and backward with each inspiration. /IG. 2. Expiration; Pressure On. While this is being done, an assistant should loosen any tight clothing about the subject's neck, chest, or waist. (7) Continue artificial respiration (if necessary, two hours or longer), without interruption, until natural breathing is restored, or until a physician arrives. Even after natural breathing begins, carefully watch that it continues. If it stops, start artificial respiration again. During the period of operation, keep the subject warm by applying a proper covering and by laying beside his body bottles or rubber bags filled with warm (not hot) water. The attention to keeping the subject warm should be given by an assistant or assistants. (8) Do not give any liquids whatever by mouth until the subject is fully conscious. 14 210 INSTRUCTIONS FOR RESUSCITATION FIRST CARE OF BURNS When natural respiration has been restored, burns, if serious, should be attended to until a doctor comes. A raw or blistered surface should be protected from the air. If clothing sticks, do not peel it off cut around it. The adherent cloth, or a dressing of cotton or other soft material applied to the burned surface, should be saturated with picric acid (0.5 per cent.). If this is not at hand, use a solution of baking soda (one teaspoonful to a pint of water), or the wound may be coated with a paste of flour and water. Or it may be protected with a heavy oil, such as machine oil, transformer oil, vaseline, linseed, carron or olive oil. Cover the dressing with cotton, gauze, lint, clean waste, clean handkerchiefs, or other soft cloth, held lightly in place by a bandage. The same coverings should be lightly bandged over a dry, charred burn, but without wetting the burned region or applying oil to it. Do not open blisters. INDEX PAGE Acid fumes, wires subject to 67 Accessibility of auto-starters 92 cut outs, branch 94 main 59, 94 generator conductors 14 grounds on metallic protective system 59 junction boxes on armored cable 83 lightning arrestors 15 switches, main 59 Arc lamps, construction 51, 52, 53 cut-out required 51 hanger board required 53 incandescent lamps as resistance 51 installation 51, 52, 53 resistance 51 size branch conductor for 51 spark arrestor, when required 51 spark arrestor, not required 52 wiring, protection of 52 Arc lamp, moving picture machine 113 Arc lamps, series, attachment to gas fixtures forbidden 53 concealed wiring not permitted 52 cracked globes not permitted 53 enclosed, required 53 isolation of 52 rubber covered wire required 52 size mesh allowed for wire netting 53 ppark arrestor required 53 switch, type required 52, 53 wire spacings 52 Armored cables. See Cables. Auditorium lights 106 Auto-starters. See Rheostats. Batteries, storage and primary 19, 20 Binding screws not to bear strain 131 Blocks, wood, for fixtures 124 for insulators 30 for switches 94 Border lights 107, 108 Boxes, junction, accessibility of armored cable 83 211 212 INDEX Boxes, support of cables in 79 supporting risers in . . . 79 Boxes, outlet, armored cable installation 84 omitted 82 broken plaster not permitted at 58 conduit, construction, lined 80, 81 unlined 80, 81 when required 79, 80 installation 79, 80, 81 covers, porcelain for 81 type acceptable 81 installation, concealed work 72 joints in 79 Boxes, portable plugging, construction 109 Boxes, reel, moving picture, construction 1 13 Boxes, switch, outline lighting construction 115 Bunch lights, construction 108, 109 Bus bars, bare 14 Bushings, armored cable, omitted on 83 brick walls, through 58 entrance, light, heat and power 29 signal system 41 generator, type obligatory 11 required conduit work 80 electric signs 116 Cabinets, approved kind 100, 101 construction 100, 101 markings 100 service, conduit entering 33 spacings 100, 101 Tables 27 and 29 196, 197, 198 spacings for link fuses in 101 switches ia 1 101 wires entering 61,71 wooden, construction 100, 101 not permitted on conduit system 100 Cables, supported in junction boxes 79 Cables, armored, bends allowed 82 construction 82, 83 grounding 83, 84 installation 82 joints 82 Cables, armored lead, construction 82 damp places, required 83 fireproof buildings, when required 83 outline lighting 115 Cables, elevator, insulation 131 Table 17 188 smallest conductor permitted 131 Cables, lead sheathed, type letter 13 INDEX 213 Cables, required for high potential motors 17 Cables, theater, feeder, required for borders 107 insulation required, Table 16 186 Cables, varnished cambric 166 Canopies 126 Capacity allowed, aluminum wire 57 alternating current (rubber covered wire) 18 Table 1 167 rubber covered wire, Table 1 167 slow burning wire 58 Table 1 167 slow burning weather-proof wire 58 Table 1 167 plugging box receptacle 109 Care and attendance 16 Note 8 17 Christmas tree lights 118 Circuits, signal systems, installation 41, 43, 47 metallic, required 41 wattage limits, 2-wire 58 3- wire 59 Circuit breakers, adjusting limits 96, 97 installation 97 markings required 97 on generators 11, 12, 96, 97 operation of 96, 97 test, breaking, Table 30 199 used as service switch 93 Cleats, construction 68 Table 21 192 installation 65, 70 Code, enforcement 3 how made 1 originator 4 Competent operator required, central stations 16 theaters and moving picture shows 112 Concealed wiring, knob and tube 71, 72 Condensers and reactive coils 45 Conductors, aluminium ' 168 distance between, at switchboard 14 inside wiring, kind permitted 31, 43, 57, 67, 70 Table 8 174, 175 installation generator to switchboard 14 size branch, for arc lamp 51 smallest size, moving picture machine 113 spacing tablet board, Table 29 198 stranded in fixture work 123 support of in vertical conduit 79 underground, requirements 36 Conduit, brass, not permitted 81 214 INDEX Conduit, rigid metal, accessibility of ground on 59 bends 80 bonding high tension motor leads 14 central stations, lined required 14 circuits, number allowed 78 construction 78, 80, 81 curve, shortest allowed 80 electric signs, required 117 entering cabinets 33, 77, 78 exposed to weather 33 Note 15 34 fastening to boxes 80 fittings, installation 78, 80 galvanized pipe as 82 grounding, interior, Note 26 77, 83, 84 installation requirements 77 outlet boxes required 79 elevator shafts 68 knob and tube work 60, 63, 69 marine work 157 theaters and moving picture establishments 106, 107 smallest size permitted 78 support of 78 support of risers in vertical 79 wires, drawn before completion of mechanical work 78 wires of different systems in 78 Conduit, flexible metallic, installation 82 requirements , 82 Connectors, pin plug 109 Covers, outlet box, type acceptable 81 porcelain, for outlet boxes 81 switch box, damp places 94 waterproof, required for generators and motors 17 Cranes, electric, collectors, construction 136 conductors, insulation resistance 135 controlling 136 cut outs required 137 grounding 137 resistance, protection of 137 wire, bare, permitted 135 collector, size required 136 support of 136 distance from surface 136 installation 135, 136 rubber covered, required 137 slow burning, required 135 smallest size, permitted 135 spacings 136 Cut outs, fuse limits in branch 61 location 59, 94 omitted in service 94 INDEX 215 required at change of wire 93 at arc lamp 51 at electric crane 137 at marine work 156 at mercury vapor lamp 120 at outline lighting 115 at signal system 41, 42, 44 signal system, construction 42 single pole, omitted on generator 12 wattage limits, fixture work 123 outline lighting 115 theater work 106 Distance, arc lamps to sidewalk 51 between supports, electric cranes 135 electric signs 116 inside work, concealed 71 open 65, 70 outline lighting 115 between wires, inside work, concealed 65 open 65 from last line support to rosette 70 from surface wired over, electric cranes 135 electric signs 116 inside work, concealed 65 open 65 outline lighting 114-115 Electric fans, ceiling 18, 19 fuse, number on one set of 18 portable 19 Emergency lights, what are 105 wiring for 105 Exit lights, control of 106 forbidden on stage circuits 106 fuses on 106 Fire proof building, armored lead cable, when required 83 canopies in 126 Fittings, conduit, installation 78 terminal 79 Fixtures, burs and pins must be removed 126 canopies, flat when permitted, 126 fuses not permitted in 126 insulated, required 126 insulated, not required 126 construction 125, 126 cu^ out, wattage limits 123 flexible cord permitted in 123 flexible tubing at outlets 124, 125 fuse, six ampere permitted 123 216 INDEX gas lighting systems on 125 grounds free from 125, 127 hickeys required 124 insulating joints, construction 125 required 124 not required 125 receptacles, exposed terminals 126 subject to heat 127 sockets, attachment of 126 testing 125, 127 Table 31 200 voltage, maximum 123 watertight, required 125 wires of different systems in 124 wiring, exposed, on 125 wooden blocks required . . . 124 wooden, armored conductors required 127 construction 127 when approved 127 Fixture wire, flex cord approved 123 tinned, required 123 ordinary rubber covered permitted 123 slow-burning wire, on 124, 127 smallest size permitted 123 stranded, approved 123 required 124 test 124 Flexible cord, electric heaters, type for 119 fan motors for 19, 130 fixtures permitted in 123 heat, subject to 127, 135 insulation requirements, Tables 10-18 178-189 knots in, required 131 long pendants, type permitted 131 portable lamps, type for 131 Tables for 178-185 theater work, type required 110, 111 show cases, type required 130 voltage limits 130 when "Type C" is permitted 130 when not permitted . ..... .... 131 wooden fixtures, type required 127 Flexible tubing, construction 72, 73 fished wires in 71 , 72 requirements in fixture work 72, 124, 125 in knob and tube, open 67, 69, 72 in knob and tube, concealed 67, 72 in outline lighting . 114, 115 in signal systems 42 when permitted 71, 72 INDEX 217 Foot light construction 107 Fuses, canopy, not permitted 126 change of wire, required 93 circuits, branch in mills 97 house. 59, 60 cut outs, branch, limits in 61 electric signs 55-volt circuits 116 fixture wire, six ampere for 123 generator 11, 12 ground detector, for 15 grounded neutral 59, 60 inside work. (See Cut outs) 59, 98 motors limited on one set of 18 neutral wire, omitted on 59 non-grounded neutral 60 on theater exit lights 106 Out-buildings, omitted on 93 pilot light 14, 15 potential transformer 15 rosette, double pole 99 signal systems, required on 41, 42, 44, 45 theater work 106 Fuses enclosed. (Cartridge and Plug), cartridge refilling 98 construction (cartridge) 98 (plug), Table 24 193 dimensions, Table 25 194, 195 ferrule contact, Table 25 194, 195 heat limits 98 in mills, large 98 labels, colors required 98 knife contact, Table 25 194, 195 markings 98 motor, A. C. required 16, 17 plug, refilling 98 Fused link, branch circuits in large mills 97 contact tips 97 markings required 97 spacings 98, 101 Table 23 51 when permitted 97 Gas lighting on fixtures 125 Generators, bushings, type permitted 11 circuit breakers 11, 12, 93, 96, 97 cut outs, single pole when permitted 12 frame, grounding required 12 insulation of 12 fuses 11, 12 guards for high potential 13 high potential, wiring 13, 14 218 INDEX location of 11 name plate required 11 terminal blocks, kind permitted 11 wiring, Note 7 16 Grounding, armored cable 83, 84 conduit 83, 84 conduit, not required 70 electric crane motors 137 flexible metallic conduit 82 generator frames 12 inside wires 32, 33 lightning arrestors, central station 16 electric cars 150 mercury vapor lamps 120 metal moulding 85 metallic protective systems 83 Note 23 69 grounded neutral systems 59, 601 neutral wire 31, 32, 33, 59, 60 outside wires 31, 33 secondary wires 31, 32, 33 signal system wires 45, 46 three-phase wires 32 transformers 23, 25, 33 wireless telegraph 46, 47 Grounding secondaries, Amer. Institute of Elec. Engs. on 5 Ground detectors required 15 Grounded neutral systems 59, 60 Guards, incandescent lamps, required for 110, 111, 127 high potential generators 13 motors 13 Strip required for wires 69 Hanger boards, construction 53 Heat, fixtures subject to 127 wires subject to 67 Heaters, electric, approved stand required, flatiron, etc 118 car 147 conductor, attachment of 119 conductor, type required 119 Table 14 184 installation 118, 119 name plate required 119 Insulators, cleats, construction, Table 21 192 installation 67, 68 use of 44, 68 knobs, installation 44, 68 outside work, when permitted for 30 INDEX 219 knobs, solid, construction. 65, 68 Table 20 191 not permitted 68 permitted 68 required at end of runs 70 split, construction 68 required 68 petticoat, outside ;work, required 30 distance apart 30 Insulation resistance of completed buildings 41 Table 31 200 Joints, armored cable 82 outlet boxes, in 79, 82 streamers and festoons 110 wire, inside work 29 marine work 156 outside work 29 wood moulding 73 Joints, insulating, construction of 125 required 124 when omitted 125 Knobs. See Insulators. Knots, inflexible required in socket and rosette 131 Lamps, arc. See Arc Lamps. Lamps, incandescent allowed on 2-wire ordinary house circuit. . . . 123 allowed on 3- wire ordinary house circuit 60, 61 arc lamps, incandescent, as resistance for 51 rheostats, as resistance for 80 series 53, 54, 90 Lamps, mercury vapor, cut out required 120 number on each 120 grounding 120 installation 119, 120 resistance, protection of 120 voltage limits 120 Lamps, portable, flexible cord, type permitted 127 guard required 127 Leather heads, use of permitted 68 Life hazard 5 Light -s arc. See Arc Lamps, car. See Railway Systems, signal. See Marine Work, theater. See Theater Wiring. Lighting, outline, armored lead cable required 115 box, construction of switch 115 cut out installation 115 required 115 wattage limits 115 220 INDEX flashers, installation 115 flexible tubing, installation 114, 115 moulding not permitted 114 receptacles, limit on circuit 115 type required 116 sockets, keyless, required 116 switch, installation 115 required 115 wattage limit on single cut out 115 wires soldered to receptacles 1 16 kind required in conduit 115 Lighting system, decorative, Christmas tree 118 limits specified 118 special permission necessary 118 Lightning arrestors, accessibility of 15 approved, required for central stations 16 street railway 150 grounding 16 insulation resistance required 16 number and location 15 signal system 44 Main block 59, 98 Marine wiring, bonding of cabinet boxes 157 brass screws required 157 conduit, A. C. circuits in 157 number of .circuits in 158 required 157 requirements 157 cut outs, wattage limits 156 waterproof required 156 fittings, conduit requirements 157 fixtures, mounting 160 protection 160 freight compartments, central 156 generator frames, insulation 155 guards required for lamps 160 joints 156 moulding, wood construction 157 installation 157 type wire required 156 test wire required 156 motors, installation requirements 161 open work not permitted 155 portable conductors 158, 159 Table 18 189 resistance boxes, installation 159 rubber tubing, thickness required 158 signal lights 160 sockets. . . 160 INDEX 221 stuffing tubes required 158 switches, deck 159 switchboard, insulation of wires at 159 special requirements, conductors 159 wood not acceptable 159 Note 159 tell-tale board required 160 vapor-proof globes required 160 wire, allowable carrying capacity 155 bell 161 conduit 157 fixture 160 largest solid, permitted 155 smallest solid, permitted 155 stranded, construction 159 Meters, installation 60 Motors, alternating current, allowable capacity of wiring 18 overload capacity of circuits 18 variable speed, markings 19 wire capacity starting 18 wiring for varying speed 18 care and attendance 16 circuits, electrical protection of 16 enclosed, recommended for dusty places 17 fans 19 frame, grounding when required 17 insulation 17 high potential wiring 17 marine 161 name plate required 16 number permitted on one set fuses 18 rating 16 single-phase, fuses required 16 stage curtain ironclad type obligatory 108 switches, indicating required 17 single-pole when permitted 17 variable speed, starting 17 water-proof cover obligatory 17 wiring capacity, Table 1 168 Moving picture establishment wiring 113, 114 arc lamp, construction 113 automatic shutter 113 films, extra 113 under examination 113 machine installation of 114 operation of 114 motor driven machine permitted 114 operator, competent, required 112 reel boxes, construction 113 rheostat, installation 113 wire, smallest size permitted for machine 113 222 INDEX Moulding metal, construction 84, 85 grounding 85 installation 84 Moulding, wooden, circuits, number, in one groove 73 conductors A. C., in same groove 73 construction 73, 74 damp places, not permitted in 73 outline lighting, not permitted in. . . : 114 use of 73 wire, rubber covered, required 73 Nails and leather heads, use of permitted 68 Open wiring. Section 6, division 1 57, 71 Outlets, flexible tubing required at 72 open spaces not permitted at 58 stage and gallery 108 terminal fittings for fixture 79 Note 28 79 Outline lighting. See Lighting Outline. Panel boards, tablet and, construction 101, 102 marking required 101 spacings 102 Table 29 198 Pilot lights, fuses for 14 Plates, dust-proof, when required 89 Plates, outlet, used instead of boxes 80 when required 80 Plates, switch, push buttons forbidden on 93 Plugs, attachment 98 ordinary fuse, Table 23 193 stage 108 Pockets, stage 108 Pole line, high tension 34, 36 Note 16 34 low tension 30 railways 141 Precautions in damp places 5 Protecting wires from mechanical injury 69 Protective devices on signal circuits 44 Railway systems, automatic control 148 cabinet, cut out, material required 143 cabinet used as outlet boxes 148 car body, protection of 142, 143 cars not to be left in electrical connection 152 circuits, heater, minimum size wire 143 circuits, lighting and motor 151 installation... 147 INDEX 223 minimum size wire 143 over fused 145 stationary motor, bonding 151 circuit breakers must be approved 145 clusters, installation 147 must be approved 147 conductor connections, construction 144 conduit, burrs in 150 installation 145, 146 size acceptable 145 third rail not grounded 146 connections, bonding of 151 controller, installation 149 current not to be taken from railway circuits 151 cut out connections, controlling 151 installation 143, 144 location 145 required 145 enclosure for air pump and motor 148 feeder distribution, centering 152 fittings, installation 145, 146 flexible cord permitted in car houses 152 fuses may be omitted 145 general rules applying 152 ground return, code requirements 142 guard wires, insulation 141 hangers, trolley, required 150 distance apart 150 heaters, approved required 147 construction 147 installation 147 insulation between trolley and ground 141 knob and tube work permitted 147, 148 permitted 146 tacking wires in 1 50 rails, bonding 151 receptacles, approved required 147 installation 147 resistance, insulation 149 lead wires, capacity 143 smallest size 143 soldered connections omitted 144 soldered connections required 144 switches, connections controlling 151 installation 145 type required 145 lamps, separate, cut out required 151 separate switch required 151 wattage limit of each 147 lightning arrester, location 150 ground wire, smallest size . 150 224 INDEX motor, circuits, main 148, 149 cut outs required 151 installation 149 lead wires, carrying capacity 143 switch separate, required 150, 151 moulding accessibility 150 backing omitted 146 construction 146 installation 146, 147 switches, emergency 150, 151 snap, permitted 145 switch box construction 145 wires, feed division of 141 feed, protecting at crossings 141 fixture permitted 144 rubber covered, special required 144 trolley, protection at crossings 141 smallest size permitted 141 strain requirements 141 trolley lead capacity J 43 Receptacles, eloctric sign 117 outline lighting 115, 116 ordinary 106, 107 Receptacles, stage, approved 108 capacity of arc and incandescent 108 control of 108 wiring requirements 108 Resuscitation from electric shock 203 Rheostats, construction 89, 90, 91 dust plate required 89 incandescent lamps as resistance 90 installation 89, 90 markings required 90 maximum difference of potential 89 no voltage release required 90 overload release required 91 resistance and contact plates, wire required 90 test 91 auto-starting, construction 91, 92 installation 92 use of 91 moving picture machine installation 113 Risers, support of, in conduit 79 Rosettes, construction 99 fused 99 link fused permitted 97 Sections, one, central stations, generators, motors, storage batteries 11-20 two, transformers. 23-26 three, outside work 29-36 four, signal systems 141-147 INDEX 225 five, constant current systems 52-54 six, division one, knob and tube work 65-74 two, metallic protective systems 77-85 three, rheostats 89-91 auto-starters 91, 92 switches 92-96 circuit breakers 96, 97 fuses 97, 98 rosettes 99, 100 cabinets 100, 101 panel boards 101, 102 four, theater wiring 105-112 moving picture 113, 114 outline lighting 114, 115, 116 electric signs 116, 117, 118 decorative lighting 118 electric heaters 118, 119 mercury vapor lamps 119, 120 five, fixtures 124-127 sockets 127-130 flex cord 130, 131 six, electric cranes.' 135, 136, 137 seven, electric railway systems 141-152 eight, marine work 155-161 nine, Tables (1-32) 167-201 Signal systems, bushing, entrance wires in single 41 circuits, all metallic, required 41 condensers 45 cut outs, entrance, location 42 for each wire required 41 type required, telegraph circuits 44 flex tubing 42 fuses, location, telegraph systems 44 required on protector 45 fuse block, construction 42 inside wiring, questions applying 42 heat coils 45 instrument, installation 42, 44 lightning arrestor, grounding 44 protectors, marking required 45 reactive coils 45 subject to code 43 sneak currents 45 staples 42 wires, cabled, exceptions for 43 cross arms on 43 ground, installation 45, 46 iron 43 shafts in 42 on buildings 43 smallest size. . . 42 226 INDEX smallest size, ground 45 kind supplying current to apparatus 44 underground 43 when separate tube is required 42 Signs, electric, bushings required 116 conduit or cable required 117 construction 117 corrosion 117 cut out, wattage limits on final 116 fuse limits on 55-volt circuit 116 open work, when permitted 116, 117 receptacles, spacings 1 16, 117 type required 117 switches, single pole 118 transformers, installation 116 wire, smallest size 118 supply 118 type required 1 18 wiring 116, 117, 118 wood 117 Smallest size wire permitted, electric signs on 118 elevator control, conductor for 131 fixtures 123 ground detector 15 grounding, alternating current, lightning arrestors, central station 16 electric cars 150 metal moulding 85 metallic protective system 84 Note 23 69 neutral, direct current, central station 32 signal system, protective devices 45 three-phase systems 32 wireless telegraph apparatus 46 interior work 57 marine work 155, 158 moving picture machine arc lamp 113 railway systems 143, 151 signal systems 42 theater work 108, 131 Sockets, construction 128, 129 markings 128 use of in hazardous places 128 used on pipe pendants 128 candelabra 129 double ended 129 key 128 keyless 128 miniature 129 weather-proof 130 Soldering required, electric sign receptacles 117 INDEX 227 joints, wire 29, 110, 156 outline lighting receptacles 116 railway systems . 144, 152 rheostats 90, 92 signal systems 46 switch lugs 96 theater receptacles 106, 107, 110 wires stranded 67, 69, 96 Spacings, cabinets, metal 115 wood 100, 101 fuse enclosed, Table 25 194, 195 link 98 Table 23 193 insulator pins 43 panel boards 101, 102 Table 29 198 receptacles, electric signs 116, 117, 118 rheostats 90, 111, 112, 137 switch 95, 96 Tables 27, 28 196, 198 switchboard from ceiling 15 wall 15 transformers from wall 24 wire, central stations 13 electric crane 135, 136 electric railway car 147, 148 electric signs 117 inside work, concealed 65 open 65, 70 outline lighting 114, 115 outside work 29, 30 series arc 52 storage batteries 20, 65 Spark arresters, construction 51 not required 52 required 53 Splices and joints in wire 29, 73, 156 Subject to code, burglar alarm service 43 electric bells inside buildings 42, 43 Read Low Voltage Transformer 25 electric call bell, outside 41, 43 fire alarm companies. (See Explanation of Section 4, page 41) , 35, 41, 43 telegraph companies 41 , 43 telephone companies 41 , 43 Switches, accessibility 59, 92 construction, knife 94, 95 double brake, auxiliary required 95 double throw, installation 93 electric sign, single pole not permitted 118 grouping 93 228 INDEX installation 92, 93, 94, 95 Note 34 95 oil, dust-proof cases required 92 outline lighting, contact required 115 installation 115 rating for D. C. and A. C 95 single pole on neutral wire 94 service, circuit breaker as 93 indicating required 94 location 93 must disconnect all wires 95 series arc, construction 53 installation 52 type required 53 snap, construction 93, 94, 96 sub-base required , 93 stage flue control, type required 112 street railway 145, 150, 151 tests for 95 time, metal cabinets required for 94 wood blocks required for 94 Switchboards, construction 14 free from moisture 15 ground detectors, when required 15 installation 15 instrument circuit, protection 15 fuses 14 link fuses permitted 14 marine, requirements 159 rear connected 15 space back of 15 wiring for 13, 14 wood, when not permitted 106, 159 permitted 14, 15 Systems. See Sections. Tape 29, 156 Terminal blocks, generator 11 Testing, fixtures for grounds 125 insulation resistance in completed buildings, Table 31 200 transformers 24 wires. Tables 5, 6, 7, 31 171, 172, 173, 200 Theater wiring, arc lamps, portable, construction Ill, 112 auditorium lights 106 borders, conductors required 107 construction 107, 108 trough suspension 107 wiring to 107 bunch lights 108, 109 cable border, construction, Table 16 186, 187 stage, construction, Table 16 186, 187 INDEX 229 conduit required switchboard to border 107 cut outs, receptacle limits on 106 wattage limits 106 dressing rooms, lamp guards required Ill pendants Ill exit lights, control 106 fuses on 106 emergency lights 105 foot-lights, construction 107, 108 flexible cord, ampere limits 110 type permitted in dressing rooms Ill festoon lights 1 10 guards, lamp, required 110, 111 lights on scenery 110 motor, curtain, type required 108 operator, competent, required 112 pin plug connectors 109 plugs, stage 108 plugging boxes, portable 109 proscenium 107, 108 receptacles, number on one cut out 106 wattage limits 106 stage, approved, required 108 control 108 rating 108 wiring requirements 108 service, auxiliary, required 105 wires , 105 scene docks 108 special electrical effects 110 stage flue, control 112 stage work 106 strip lights 109 switchboard, guard rail required 106 wooden, not permitted 106 wire, border, insulation .' 107 Table 16 186 wires, service 105 Tables, Section 9 163 Transformers, approved, required 25 Note 12 24 enclosures 24 grounding .' 23, 25, 33 installation, electric sign 129 high potential 24 extra 24 low potential 24 Section 2 23 low voltage 25 wireless telegraph 46 tests. . . .... 24 230 INDEX Tubes, cabinets, entering 67 construction, Table 19 190 cross-over 67 electric signs 116 entrance 29, 58 signal systems 41 marine stuffing lt>8 signal system 42 timbers passing through 67, 72 wall, through brick 58 Tubing, flexible 72, 73 Underground conductors 36 Underwriters laboratories, organization and purpose 2 Wattage limits, circuits, 2-wire 58, 60 3-wire 60 cut outs, branch 61, 115, 116, 118, 123, 156 railway systems, lamps. 147 switches, single-pole on neutral 94 switchboard instrument circuit 15 Wire, armored. See Cables, Armored. concentric, Table 8 175 conduit, Table 8 174, 175 fixture, Table 9 176 flexible cord 129 lead covered 13, 58 iron, use of, signal systems 43 netting on arc lamps 51 rubber covered, 0-600 volts, Table 5 171 600-3500 volts, Table 6 172 3500-7000 volts, Table 7 173 slow-burning, Table 3 170 slow-burning, weatherproof, Table 2 169 Wires, allowable capacity, aluminum 57 alternating current 18 Table 168 rubber covered 57, 58 Table 1 168 attics in 66 border insulation 107 concealed work, spacings 65, 67, 71 conduit, different systems in same 78 conduit, installation 77, 78 circuits, allowed, in 78 crossing pipes 67 cut out required at change of 93 elevator shafts, in 68 entrance 29, 31 entering cabinets . 67, 71 extra high potential, installation of primary 58 INDEX 231 insulation of secondary. 58 pole line 34, 36 fished 71, 72 fixture, braid test for 124 must be tinned 123 on exposed 123 protection of 126, 127 slow-burning, approved 127 stranded, required 124 flame proof required 19 flexible tubing, in 71, 72 Note 25 72 fuse required at change of 58 generator to switchboard 14 grounded neutral 60 grounding, A. C. secondary 31, 32, 33 Note 14 31 grounding, at central station 32 grounding, inside 32, 33 grounding, neutral 31, 32 grounding outside 31, 32, 33 Note 14 31 guard strips required 69 inside work spacings 52, 65, 66, 70, 71 knob and tube, insulation required 70 knob and tube, concealed 71, 72 knob and tube, open, spacings 65, 67, 71 mixed system 66 moulding, in 73, 78 neutral, single pole switch on 94 not permitted under staples 32, 68 outline lighting, type required 115 passing through timbers 72 protection against mechanical injury 69 Notes 23, 24 69, 70 rheostat insulation 90 rubber covered, type letter for 0-550 volts 57 rubber covered, required, electric cranes 135, 137 electric signs 118 fixtures 124 high potential circuits 13 inside work 52, 71 moulding, wood 73 outline lighting 115 pole line 29 railway system 144 service 29 signal system 43, 45 theater work 110 series arc, insulation 52 signal system, ground 45, 46 232 INDEX entrance 137 insulation 43 installation 43, 44 on cross arms 43 permitted under staples 42 Note 17 42 pole to building 43 underground conduits 43 slow-burning permitted 67 smallest size permitted, electric signs 118 elevator conductor 131 fixture 123 ground detector 15 grounding lightning arrestors 16 electric cars 150 metal moulding 85 metallic protective system 84 neutral, central stations 32 secondaries 32 signal system, protective devices, ground 45 3-phase systems, ground 32 wireless telegraph apparatus, ground 40 interior work 57 marine work 1 551 58 moving picture arc lamps 113 railway systems 143, 151 signal systems 42 stranded, computing 57 required 124 soldering required 67 subject to acid fumes 67 to heat 57, 67 to moisture 66 support of, at end of runs 70 service, aerial 29 conduit 31, 33 defined 31 knobs permitted on 30 petticoat insulators required on .> 30 support of outside 30 wood blocks, painted 30 switchboards, installation at 13 tie 68 tinned, all 123 Tables 8, 9 174, 175, 176 twin, use of 70 Wiring, car, read 142-151 moving picture shows 113, 114 theaters 105-112 Wireless telegraph apparatus 46, 47 Wooden moulding 73, 74 UNIVERSITY OF CALIFORNIA LIBRARY This book is DUE on the last date stamped below. Fine schedule: 25 cents on first day overdue 50 cents on fourth day overdue One dollar on seventh day overdue. 1949 / ENGINEERING L NOV 29 L .- tit 11950* LD 21-100m-12,'46(A2012sl6)4120 BRARY osioo