"NATIONAL ELECTRICAL CODE."

RULES AND REQUIREMENTS

OF THE

National Board of Fire Underwriters

FOR THE INSTALLATION OF

ELECTRIC WIRING

AND

APPARATUS

As Recommended by the

UNDERWRITERS' NATIONAL ELECTRIC ASSOCIATION

EDITION OF 1897.

The National Electrical Code, as it is here presented, is the result of the united efforts of the various Electrical, Insurance, Architectural and allied interests which have, through the National Conference on Standard Electrical Rules, composed of delegates from the following Associations, unanimously voted to recommend them to their respective Associations for approval or adoption:

American Institute of Architects. American Institute of Electrical Engineers. American Society of Mechanical Engineers. American Street Railway Association. Factory Mutual Fire Insurance Companies. National Association of Fire Engineers. National Board of Fire Underwriters. National Electric Light Association. Underwriters' National Electric Association.

And as soon as meetings of these Associations are held, and action taken, the fact will be noted.

GENERAL PLAN

GOVERNING THE ARRANGEMENT OF RULES.

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CLASS A.—Central Stations, Dynamo, Motor, and Storage-Battery Rooms, Transformer Substations, etc. Rules 1 to 11.

CLASS B.—Outside Work, all systems and voltages. Rules 12 and 13.

CLASS C.—Inside Work. Rules 14 to 39. Subdivided as follows: General Rules, applying to all systems and voltages. Rules 14 to 17. Constant-Current Systems. Rules 18 to 20. Constant-Potential Systems. All voltages. Rules 21 to 23. Voltage not over 300. Rules 24 to 31. Voltage between 300 and 3,000. Rules 32 to 37. Voltage over 3,000. Rules 38 and 39.

CLASS D.—Specifications for Wires and Fittings. Rules 40 to 55.

CLASS E.—Miscellaneous. Rules 56 to 59.

CLASS F.—Marine Wiring. Rules 60 to 72.

GENERAL SUGGESTIONS.

In all electric work conductors, however well insulated, should always be treated as bare, to the end that under no conditions, existing or likely to exist, can a grounding or short circuit occur, and so that all leakage from conductor to conductor, or between conductor and ground, may be reduced to the minimum.

In all wiring special attention must be paid to the mechanical execution of the work. Careful and neat running, connecting, soldering, taping of conductors, and securing and attaching of fittings, are specially conducive to security and efficiency, and will be strongly insisted on.

In laying out an installation, except for constant-current systems, the work should, if possible, be started from a center of distribution, and the switches and cut-outs, controlling and connected with the several branches, be grouped together in a safe and easily accessible place, where they can be readily got at for attention or repairs. The load should be divided as evenly as possible among the branches, and all complicated and unnecessary wiring avoided.

The use of wire-ways for rendering concealed wiring permanently accessible is most heartily indorsed and recommended; and this method of accessible concealed construction is advised for general use.

Architects are urged, when drawing plans and specifications, to make provision for the channeling and pocketing of buildings for electric light or power wires, and in specifications for electric gas lighting to require a two-wire circuit, whether the building is to be wired for electric lighting or not, so that no part of the gas fixtures or gas piping be allowed to be used for the gas-lighting circuit.

Class A.

STATIONS & DYNAMO ROOMS.

Includes Central Stations, Dynamo, Motor and Storage-Battery Rooms, Transformer Substations, Etc.

1. Generators—

a. Must be located in a dry place.

b. Must never be placed in a room where any hazardous process is carried on, nor in places where they would be exposed to inflammable gases or flyings of combustible materials.

c. Must be insulated on floors or base frames, which must be kept filled to prevent absorption of moisture, and also kept clean and dry. Where frame insulation is impracticable, the Inspection Department having jurisdiction may, in writing, permit its omission, in which case the frame must be permanently and effectively grounded.

d. Every constant-potential generator must be protected from excessive current by a safety fuse, or equivalent device, of approved design in each lead wire.

e. Must each be provided with a waterproof cover.

f. Must each be provided with a name-plate, giving the maker's name, the capacity in volts and amperes, and normal speed in revolutions per minute.

2. Conductors—

From generators to switchboards, rheostats or other instruments, and thence to outside lines.

a. Must be in plain sight or readily accessible.

b. Must have an approved insulating covering as called for by rules in Class "C" for similar work, except that in central stations, on exposed circuits, the wire which is used must have a heavy braided, non-combustible outer covering. Bus bars may be made of bare metal.

c. Must be kept so rigidly in place that they cannot come in contact.

d. Must in all other respects be installed under the same precautions as required by rules in Class "C" for wires carrying a current of the same volume and potential.

3. Switchboards—

a. Must be so placed as to reduce to a minimum the danger of communicating fire to adjacent combustible material.

b. Must be made of non-combustible material or of hardwood in skeleton form, filled to prevent absorption of moisture.

c. Must be accessible from all sides when the connections are on the back, but may be placed against a brick or stone wall when the wiring is entirely on the face.

d. Must be kept free from moisture.

e. Bus bars must be equipped in accordance with rules for placing conductors.

4. Resistance Boxes and Equalizers—

(For construction rules, see No. 52.)

a. Must be placed on a switchboard or, if not thereon, at a distance of at least a foot from combustible material, or separated therefrom by a non-inflammable, non-absorptive, insulating material.

5. Lightning Arresters—

(For construction rules, see No. 55.)

a. Must be attached to each side of every overhead circuit connected with the station.

b. Must be located in readily accessible places away from combustible materials, and as near as practicable to the point where the wires enter the building. Station arresters should generally be placed in plain sight on the switchboard. In all cases, kinks, coils and sharp bends in the wires between the arresters and the out-door lines must be avoided as far as possible.

c. Must be connected with a thoroughly good and permanent ground connection by metallic strips or wires having a conductivity not less than that of a No. 6 B. & S. copper wire, which must be run as nearly in a straight line as possible from the arresters to the earth connection. Ground wires for lightning arresters must not be attached to gas pipes within the buildings.

6. Care and Attendance—

a. A competent man must be kept on duty where generators are operating.

b. Oily waste must be kept in approved metal cans and removed daily.

7. Testing of Insulation Resistance—

a. All circuits must be provided with reliable ground detectors. Detectors which indicate continuously, and give an instant and permanent indication of a ground are preferable. Ground wires from detectors must not be attached to gas pipes within the building.

b. Where continuously indicating detectors are not feasible, the circuits should be tested at least once per day, and preferably oftener.

c. Data obtained from all tests must be preserved for examination by the Inspection Department having jurisdiction.

8. Motors—

a. Must be insulated on floors or base frames, which must be kept filled to prevent absorption of moisture; and must be kept clean and dry. Where frame insulation is impracticable the Inspection Department having jurisdiction may, in writing, permit its omission, in which case the frame must be permanently and effectively grounded.

b. Must be wired with the same precautions as required by rules in class "C", for wires carrying a current of the same volume and potential.

c. The motor and resistance box must be protected by a cut-out and controlled by a switch (see No. 17 a), said switch plainly indicating whether "on" or "off". Where one-quarter horse-power or less is used on low-tension circuits a single-pole switch will be accepted. The switch and rheostat must be located within sight of the motor, except in such cases where special permission to locate them elsewhere is given, in writing, by the Inspection Department having jurisdiction.

d. Must have their rheostats or starting boxes located so as to conform to the requirements of Rule 4.

e. Must not be run in series-multiple or multiple-series.

f. Must be covered with a waterproof cover when not in use, and, if deemed necessary by the Inspection Department having jurisdiction, must be inclosed in an approved case.

g. Must, when combined with ceiling fans, be hung from insulated hooks, or else there must be an insulator interposed between the motor and its support.

h. Must each be provided with a name-plate, giving the maker's name, the capacity in volts and amperes, and the normal speed in revolutions per minute.

9. Railway Power Plants—

a. Must be equipped in each feed wire before they leave the station with an approved automatic circuit-breaker (see No. 44) or other device, which will immediately cut off the current in case of a ground. This device must be mounted on a fireproof base, and in full view and reach of the attendant.

10. Storage or Primary Batteries—

a. When current for light and power is taken from primary or secondary batteries, the same general regulations must be observed as applied to similar apparatus fed from dynamo generators developing the same difference of potential.

b. Storage battery rooms must be thoroughly ventilated.

c. Special attention is directed to the rules for rooms where acid fumes exist (see No. 24, j and k).

d. All secondary batteries must be mounted on non-absorptive, non-combustible insulators, such as glass or thoroughly vitrified and glazed porcelain.

e. The use of any metal liable to corrosion must be avoided in connections of secondary batteries.

11. Transformers—

(For construction rules, see No. 54.)

a. In central or sub-stations the transformers must be so placed that smoke from the burning out of the coils or the boiling over of the oil (where oil filled cases are used) could do no harm.

Class B.

OUTSIDE WORK.

All Systems and Voltages.

12. Wires—

a. Service wires must have an approved rubber insulating covering (see No. 40 a). Line wires, other than services, must have an approved weatherproof or rubber insulating covering. (See No. 40 a and b). All tie wires must have an insulation equal to that of the conductors they confine.

b. Must be so placed that moisture cannot form a cross connection between them, not less than a foot apart, and not in contact with any substance other than their insulating supports. Service blocks must be covered over their entire surface with at least two coats of waterproof paint.

c. Must be at least seven feet above the highest point of flat roofs, and at least one foot above the ridge of pitched roofs over which they pass or to which they are attached.

d. Must be protected by dead insulated guard irons or wires from possibility of contact with other conducting wires or substances to which current may leak. Special precautions of this kind must be taken where sharp angles occur, or where any wires might possibly come in contact with electric light or power wires.

e. Must be provided with petticoat insulators of glass or porcelain. Porcelain knobs or cleats and rubber hooks will not be approved.

f. Must be so spliced or joined as to be both mechanically and electrically secure without solder. The joints must then be soldered, to insure preservation, and covered with an insulation equal to that on the conductors.

g. Must, where they enter buildings, have drip loops outside, and the holes through which the conductors pass must be bushed with non-combustible, non-absorptive insulating tubes slanting upward toward the inside.

h. Telegraph, telephone and similar wires must not be placed on the same cross-arm with electric light or power wires.

i. The metallic sheaths to cables must be permanently and effectively connected to "earth."

TROLLEY WIRES.

j. Must not be smaller than No. 0 B. & S. copper or No. 4 B. & S. silicon bronze, and must readily stand the strain put upon them when in use.

k. Must have a double insulation from the ground. In wooden pole construction, the pole will be considered as one insulation.

l. Must be capable of being disconnected at the power plant, or of being divided into sections, so that, in case of fire on the railway route, the current may be shut off from the particular section and not interfere with the work of the firemen. This rule also applies to feeders.

m. Must be safely protected against accidental contact where crossed by other conductors.

GROUND RETURN WIRES.

n. For the diminution of electrolytic corrosion of underground metal work, ground return wires must be so arranged that the difference of potential between the grounded dynamo terminal and any point on the return circuit will not exceed twenty-five volts.

13. Transformers—

(For construction rules, see No. 54.)

a. Must not be placed inside of any building, excepting central stations, unless by special permission of the Inspection Department having jurisdiction. b. Must not be attached to the outside walls of buildings, unless separated therefrom by substantial supports.

Class C.

INSIDE WORK.

(Light, Power and Heat. For Signaling Systems, see Class E.)

All Systems and Voltages.

GENERAL RULES—ALL SYSTEMS AND VOLTAGES.

14. Wires—

(For special rules, see Nos. 18, 24, 32, 38 and 39.)

a. Must not be of smaller size than No. 14 B. & S., except as allowed under Rule 24 u and 40 c.

b. Tie wires must have an insulation equal to that of the conductors they confine.

c. Must be so spliced or joined as to be both mechanically and electrically secure without solder; they must then be soldered to insure preservation, and the joint covered with an insulation equal to that on the conductors. Stranded wires must be soldered before being fastened under clamps or binding screws, and, when they have a conductivity greater than that of No. 10 B. & S. copper wire, they must be soldered into lugs.

d. Must be separated from contact with walls, floors, timbers or partitions through which they may pass by non-combustible, non-absorptive insulating tubes, such as glass or porcelain.

e. Must be kept free from contact with gas, water or other metallic piping, or any other conductors or conducting material which they may cross, by some continuous and firmly fixed non-conductor, creating a separation of at least one inch. Deviations from this rule may sometimes be allowed by special permission.

f. Must be so placed in wet places that an air space will be left between conductors and pipes in crossing, and the former must be run in such a way that they cannot come in contact with the pipe accidentally. Wires should be run over, rather than under, pipes upon which moisture is likely to gather or which, by leaking, might cause trouble on a circuit.

15. Underground Conductors—

a. Must be protected, when brought into a building, against moisture and mechanical injury, and all combustible material must be kept removed from the immediate vicinity.

b. Must not be so arranged as to shunt the current through a building around any catch-box.

16. Table of Carrying Capacity of Wires—

Below is a table showing the allowable carrying capacity of wires containing ninety-eight per cent pure copper, which must be followed in placing interior conductors:

	Table A.	Table B.
	Rubber Covered Wires.	Weatherproof Wires.
	See No. 40 a.	See No. 40 b.
B. & S. G.	Amperes.	Amperes.
18	3	5
16	6	8
14	12	16
12	17	23
10	24	32
8	33	46
6	46	65
5	54	77
4	65	92
3	76	110
2	90	131
1	107	156
0	127	185
00	150	220
000	177	262
0000	210	312
Circular Mils.
200,000	200	300
300,000	270	400
400,000	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

17. Switches, Cut-outs, Circuit-Breakers, Etc.—

(For construction rules, see Nos. 43, 44 and 45.)

a. Must, whenever called for, unless otherwise provided (for exceptions, see No. 8 c and No. 22 c), be so arranged that the cut-outs will protect, and the opening of a switch or circuit breaker will disconnect, all of the wires; that is, in a two-wire system the two wires, and in a three-wire system the three wires, must be protected by the cut-out and disconnected by the operation of the switch or circuit-breaker.

b. Must not be placed in the immediate vicinity of easily ignitible stuff or where exposed to inflammable gases or dust or to flyings of combustible material.

c. Must, when exposed to dampness, either be inclosed in a waterproof box or mounted on porcelain knobs.

CONSTANT-CURRENT SYSTEMS.

PRINCIPALLY SERIES ARC LIGHTING.

18. Wires—

(See also Nos. 14, 15 and 16.)

a. Must have an approved rubber insulating covering. (see No. 40 a)

b. Must be arranged to enter and leave the building through an approved double-contact service switch (see No. 51 b), mounted in a non-combustible case, kept free from moisture, and easy of access to police or firemen.

c. Must always be in plain sight, and never encased, except when required by the Inspection Department having jurisdiction.

d. Must be supported on glass or porcelain insulators, which separate the wire at least one inch from the surface wired over, and must be kept rigidly at least eight inches from each other, except within the structure of lamps, on hanger-boards, in cut-out boxes, or like places, where a less distance is necessary.

e. Must, on side walls, be protected from mechanical injury by a substantial boxing, retaining an air space of one inch around the conductors, closed at the top (the wires passing through bushed holes), and extending not less than seven feet from the floor. When crossing floor timbers in cellars, or in rooms where they might be exposed to injury, wires must be attached by their insulating supports to the under side of a wooden strip not less than one-half an inch in thickness.

19. Arc Lamps—

(For construction rules, see No. 57.)

a. Must be carefully isolated from inflammable material.

b. Must be provided at all times with a glass globe surrounding the arc, securely fastened upon a closed base. No broken or cracked globes to be used.

c. Must be provided with a wire netting (having a mesh not exceeding one and one-quarter inches) around the globe, and an approved spark arrester (see No. 50), when readily inflammable material is in the vicinity of the lamps, to prevent escape of sparks, melted copper or carbon. It is recommended that plain carbons, not copper-plated, be used for lamps in such places.

d. Where hanger-boards (see No. 48) are not used, lamps must be hung from insulating supports other than their conductors.

20. Incandescent Lamps in Series Circuits—

a. Must have the conductors installed as provided in Rule No. 18, and each lamp must be provided with an automatic cut-out.

b. Must have each lamp suspended from a hanger-board by means of rigid tube.

c. No electro-magnetic device for switches and no system of multiple-series or series-multiple lighting will be approved.

d. Under no circumstances can they be attached to gas fixtures.

CONSTANT-POTENTIAL SYSTEMS.

GENERAL RULES—ALL VOLTAGES.

21. Automatic Cut-outs (Fuses and Circuit-Breakers.)

(See No. 17, and for construction, Nos. 44 and 45.)

a. Must be placed on all service wires, either overhead or underground, as near as possible to the point where they enter the building and inside the walls, and arranged to cut off the entire current from the building.

b. Must be placed at every point where a change is made in the size of wire [unless the cut-out in the larger wire will protect the smaller. (See No. 16)].

c. Must be in plain sight, or inclosed in an approved box (see No. 46), and readily accessible. They must not be placed in the canopies or shells of fixtures.

d. Must be so placed that no set of incandescent lamps, whether grouped on one fixture or several fixtures or pendants, requiring a current of more than six amperes shall be dependent upon one cut-out. Special permission may be given in writing by the Inspection Department having jurisdiction for departure from this rule in the case of large chandeliers.

e. Must be provided with fuses, the rated capacity of which does not exceed the allowable carrying capacity of the wire, and, when circuit breakers are used, they must not be set more than about thirty per cent above the allowable carrying capacity of the wire, unless a fusible cut-out is also installed in the circuit (see No. 16).

22. Switches—

(See No. 17, and for construction, No. 43.)

a. Must be placed on all service wires, either overhead or underground, in a readily accessible place, as near as possible to the point where the wires enter the building, and arranged to cut off the entire current.

b. Must always be placed in dry, accessible places, and be grouped as far as possible. Knife switches must be so placed that gravity will tend to open rather than close the switch.

c. Must not be single-pole, except when the circuits which they control supply not more than six 16 candle-power lamps or their equivalent.

d. Where gangs of flush switches are used, whether with conduit systems or not, the switches must be inclosed in boxes constructed of or lined with fire resisting material. Where two or more switches are placed under one plate, the box must have a separate compartment for each switch. No push buttons for bells, gas lighting circuits or the like shall be placed in the same wall plate with switches controlling electric light or power wiring.

23. Electric Heaters—

a. Must, if stationary, be placed in a safe situation, isolated from inflammable materials and be treated as sources of, heat.

b. Must each have a cut-out and indicating switch (see No. 17 a).

c. Must have the attachments of feed wires to the heaters in plain sight, easily accessible and protected from interference, accidental or otherwise.

c. Flexible conductors for smoothing irons and sad irons, and for all devices requiring over 250 watts, must comply with Rule 45, section g.

d. The flexible conductors for portable apparatus, such as irons, etc., must have an approved insulating covering (see No. 40 c, 3).

e. Must each be provided with name plate, giving the maker's name and the normal capacity in volts and amperes.

LOW-POTENTIAL SYSTEMS.

300 VOLTS OR LESS.

Any circuit attached to any machine, or combination of machines, which develops a difference of potential between any two wires, of over ten volts and less than 300 volts, shall be considered as a low-potential circuit, and as coming under the class, unless an approved transforming device is used, which cuts the difference of potential down to ten volts or less. The primary circuit not to exceed a potential of 3,000 volts.

24. Wires—

GENERAL RULES.

(See also Nos. 14, 15, and 16.)

a. Must not be laid in plaster, cement, or similar finish.

b. Must never be fastened with staples.

c. Must not be fished for any great distance, and only in places where the inspector can satisfy himself that the rules have been complied with.

d. Twin wires must never be used, except in conduits, or where flexible conductors are necessary.

e. Must be protected on side walls from mechanical injury. When crossing floor timbers in cellars or in rooms, where they might be exposed to injury, wires must be attached by their insulating supports to the under side of a wooden strip, not less than one-half inch in thickness, and not less than three inches in width.

f. When run immediately under roofs, or in proximity to water tanks or pipes, will be considered as exposed to moisture.

SPECIAL RULES.

For open work:

In Dry Places:

g. Must have an approved rubber or weatherproof insulation (See No. 40 a and b.)

h. Must be rigidly supported on non-combustible, non-absorptive insulators, which separate the wire at least one-half inch from the surface wired over, and they must be kept apart at least two and one-half inches.

In damp places, such as Breweries, Packing Houses, Stables, Dye Houses, Paper or Pulp Mills, or building specially liable to moisture or acid or other fumes liable to injure the wires or their insulation, except where used for pendants:

i. Must have an approved rubber insulating covering (see No. 40 a).

j. Must be rigidly supported on non-combustible, non-absorptive insulators, which separate the wire at least one inch from the surface wired over, and must be kept apart at least two and one-half inches.

k. Must have no joints or splices.

For moulding work:

l. Must have approved rubber insulating covering (see No. 40 a).

m. Must never be placed in moulding in concealed or damp places.

For conduit work:

n. Must have an approved rubber insulating covering (see No. 40 e).

o. Must not be drawn in until all mechanical work on the building has been, as far as possible, completed.

p. Must not have wires of different circuits drawn in the same conduit.

q. Must, for alternating systems, have the two or more wires of a circuit drawn in the same conduit.

For so-called concealed work:

r. Must have an approved rubber insulating covering (see No. 40 a).

s. Must be rigidly supported on non-combustible, non-absorptive insulators which separate the wire at least one inch from the surface wired over, and must be kept at least ten inches apart, and, when possible, should be run singly on separate timbers or studding.

t. When from the nature of the case it is impossible to place concealed wiring on non-combustible insulating supports of glass or porcelain, the wires, if not exposed to moisture, may be fished on the loop system if incased throughout in approved continuous flexible tubing or conduit. (See page 45.)

For fixture work:

u. Must have an approved rubber insulating covering (see No. 40 d), and shall not be less in size than No. 18 B. & S.

v. Supply conductors, and especially the splices to fixture wires, must be kept clear of the grounded part of gas pipes, and, where shells are used, the latter must be constructed in a manner affording sufficient area to allow this requirement.

w. Must, when fixtures are wired outside, be so secured as not to be cut or abraded by the pressure of the fastenings or motion of the fixture.

25. Interior Conduits—

(See also Nos. 24 n to q, and 41.)

a. Must be continuous from one junction box to another or to fixtures, and the conduit tube must properly enter all fittings.

b. Must be first installed as a complete conduit system, without the conductors.

c. Conduits must extend at least one-half inch beyond the finished surface of walls or ceilings, except that, if the end is threaded and a coupling screwed on, the conduit may be left flush with the surface, and the coupling may be removed when work on building is completed.

d. Must, after conductors are introduced, have all outlets plugged with special wood or fibrous plugs, made in parts, and the outlet then sealed with approved compound. Joints must be made airtight and moisture proof.

e. Must have the metal of the conduit permanently and effectually grounded.

26. Fixtures—

(See also No. 24 u to w.]

a. Must, when supported from the gas piping of a building, be insulated from the gas piping of a building, be insulated from the gas-pipe system by means of approved insulating joints (see No. 51) placed as close as possible to the ceiling.

b. Must have all burs, or fins, removed before the conductors are drawn into the fixture.

c. The tendency to condensation within the pipes should be guarded against by sealing the upper end of the fixture.

d. No combination fixture in which the conductors are concealed in a space less than one-fourth inch between the inside pipe and the outside casing will be approved.

e. Must be tested for "contacts" between conductors and fixtures, for "short circuits" and for ground connections before it is connected to its supply conductors.

f. Ceiling blocks of fixtures should be made of insulating material; if not, the wires in passing through the plate must be surrounded with non-combustible, non-absorptive, insulating material, such as glass or porcelain.

27. Sockets—

(For construction rules, see No. 47.)

a. In rooms where inflammable gases may exist the incandescent lamp and socket must be inclosed in a vapor-tight globe, and supported on a pipe-hanger, wired with approved rubber-covered wire (see No. 40 a) soldered directly to the circuit.

b. In damp or wet places, or over specially inflammable stuff, waterproof sockets must be used.

28. Flexible Cord—

a. Must have an approved insulation and covering (see No. 40 c.)

b. Must not be used as a support for clusters.

c. Must not be used except for pendants, wiring of fixtures and portable lamps or motors.

d. Must not be used in show windows.

e. Must be protected by insulating bushings where the cord enters the socket.

f. Must be so suspended that the entire weight of the socket and lamp will be borne by knots under the bushing in the socket, and above the point where the cord comes through the ceiling block or rosette, in order that the strain may be taken from the joints and binding screws.

29. Arc Lamps on Constant-Potential Circuits—

a. Must have a cut-out (see No. 17 a) for each lamp or each series of lamps.

b. Must only be furnished with such resistances or regulators as are inclosed in non-combustible material, such resistances being treated as sources of heat. Incandescent lamps must not be used for resistance devices.

c. Must be supplied with globes and protected by spark arresters and wire netting around the globe, as in the case of arc lamps on high-potential circuits. (see Nos. 19 and 50).

30. Economy Coils—

a. Economy and compensator coils for arc lamps must be mounted on non-combustible, non-absorptive insulating supports, such as glass or porcelain, allowing an air space of at least one inch between frame and support, and in general to be treated like sources of heat.

31. Decorative Series Lamps—

a. Incandescent lamps run in series shall not be used for decorative purposes inside of buildings, except by special permission in writing from the Inspection Department having jurisdiction.

HIGH-POTENTIAL SYSTEMS.

300 To 3,000 Volts.

Any circuit attached to any machine or combination of machines, which develops a difference of potential, between any two wires, of over 300 volts and less than 3,000 volts, shall be considered as a high potential circuit, and as coming under that class, unless an approved transforming device is used, which cuts the difference of potential down to 300 volts or less.

32. Wires—

(See also Nos. 14, 15 and 16.)

a. Must have an approved rubber-insulating covering. (See No. 40 a.)

b. Must be always in plain sight and never incased, except where required by the Inspection Department having jurisdiction.

c. Must be rigidly supported on glass or porcelain insulators, which raise the wire at least one inch from the surface wired over, and must be kept apart at least four inches for voltages up to 750 and at least eight inches for voltages over 750.

d. Must be protected on side walls from mechanical injury by a substantial boxing, retaining an air space of one inch around the conductors, closed at the top (the wires passing through bushed holes) and extending not less than seven feet from the floor. When crossing floor timbers, in cellars, or in rooms, where they might be exposed to injury, wires must be attached by their insulating supports to the under side of a wooden strip not less than one-half an inch in thickness.

33. Transformers (When permitted inside buildings, see No. 13)—

(For construction rules, see No. 54.)

a. Must be located at a point as near as possible to that at which the primary wires enter the building.

b. Must be placed in an inclosure constructed of or lined with fire-resisting material; the inclosure to be used only for this purpose, and to be kept securely locked, and access to the same allowed only to responsible parties.

c. Must be effectually insulated from the ground and the inclosure in which they are placed must be practically air tight, except that it shall be thoroughly ventilated to the outdoor air, if possible, through a chimney or flue. There should be at least six inches air space on all sides of the transformer.

34. Car Wiring—

a. Must be always run out of reach of the passengers, and must have an approved rubber insulating covering. (See No. 40 a.)

35. Car Houses—

a. Must have the trolley wires securely supported on insulating hangers.

b. Must have the trolley hangers placed at such a distance apart that, in case of a break in the trolley wire, contact can not be made with the floor.

c. Must have cut-out switch located at a proper place outside of the building, so that all trolley circuits in the building can be cut out at one point, and line circuit breakers must be installed, so that when this cut-out switch is open the trolley wire will be dead at all points within 100 feet of the building. The current must be cut out of the building whenever the same is not in use or the road is not in operation.

d. Must have all lamps and stationary motors installed in such a way that one main switch can control the whole of each installation—lighting or power—independently of main feeder-switch. No portable incandescent lamps or twin wire allowed, except that portable incandescent lamps may be used in the pits, connections to be made by two approved rubber-covered flexible wires (see No. 40 a), properly protected against mechanical injury; the circuit to be controlled by a switch placed outside of the pit.

e. Must have all wiring and apparatus installed in accordance with rules under Class "C" for constant potential systems.

f. Must not have any system of feeder distribution centering in the building.

g. Must have the rails bonded at each joint with not less than No. 2 B. & S. annealed copper wire; also a supplementary wire to be run for each track.

h. Must not have cars left with trolley in electrical connection with the trolley wire.

36. Lighting and Power from Railway Wires—

a. Must not be permitted, under any pretense, in the same circuit with trolley wires with a ground return, except in electric railway cars, electric car houses, and their power stations, nor shall the same dynamo be used for both purposes.

37. Series Lamps—

a. No system of multiple-series or series-multiple for light or power will be approved.

b. Under no circumstances can lamps be attached to gas fixtures.

EXTRA-HIGH-POTENTIAL SYSTEMS.

OVER 3,500 VOLTS.

Any circuit attached to any machine or combination of machines, which develops a difference of potential, between any two wires, of over 3,000 volts, shall be considered as an extra high potential circuit, and as coming under that class, unless an approved transforming device is used, which cuts the difference of potential down to 3,000 volts or less.

38. Primary Wires—

Must not be brought into or over buildings, except power stations and sub-stations.

39. Secondary Wires—

a. Must be installed under Rules for high-potential systems when their immediate primary wires carry a current at a potential of over 3,000 volts.

Class D.

FITTINGS, MATERIALS AND DETAILS OF CONSTRUCTION.

All Systems and Voltages.

40. Wire Insulation—

a. Rubber Covered— The insulating covering must be solid, at least three-sixty-fourths of an inch in thickness and covered with a substantial braid. It must not readily carry fire, must show an insulating resistance of one megohm per mile after two weeks' submersion in water at seventy degrees Fahrenheit and three days' submersion in lime water, and after three minutes' electrification with 550 volts. (See page 44.)

b. Weatherproof— The insulating covering must not support combustion, must resist abrasion, must be at least one-sixteenth of an inch in thickness, and thoroughly impregnated with a moisture repellent.

c. Flexible Cord— Must be made of two stranded conductors, each having a carrying capacity equivalent to not less than a No. 16 B. & S. wire, and each covered by an approved insulation, and protected by a slow-burning, tough-braided outer covering.

1. Insulation for pendants under this rule must be moisture and flame proof.
2. Insulation for cords used for all other purposes, including portable lamps and motors, must be solid, at least one-thirty-second of an inch in thickness, and must show an insulation resistance between conductors, and between either conductor and the ground, of at least one megohm per mile after one week's submersion in water at seventy degrees Fahrenheit, and after three minutes' electrification, with 550 volts.
3. The flexible conductors for portable heating apparatus, such as irons, etc., must have an insulation that will not be injured by heat, such as asbestos, which must be protected from mechanical injury by an outer, substantial, braided covering, and so arranged the mechanical strain will not be borne by the electrical connection.

d. Fixture Wire— Must have a solid insulation, with a slow-burning, tough, outer covering, the whole to be at least one-thirty-second of an inch in thickness, and show an insulation resistance between conductors, and between either conductor and the ground, of at least one megohm per mile, after one week's submersion in water at seventy degrees Fahrenheit, and after three minutes' electrification, with 550 volts.

e. Conduit Wire— Must comply with the following specifications:

1. For insulated metal conduits single wires and twin conductors must comply with section (a) of this rule. Concentric wire must have a braided covering between the outer conductor and the insulation of the inner conductor, and in addition, must comply with section (a) of this rule.
2. For non-insulated metal conduits single wires and twin conductors must comply with section (a) of this rule, and, in addition, have a second outer fibrous covering, at least one-thirty-second of an inch in thickness, and sufficiently tenacious to withstand the abrasion of being hauled through the metal conduit. Concentric conductors must have a braided covering between the outer conductor and the insulation of the inner conductor, and comply with section (a) of this rule, and, in addition, must have a second outer fibrous covering at least one-thirty-second of an inch in thickness, and sufficiently tenacious to withstand the abrasion of being hauled through the metal conduit.

41. Interior Conduits—

(For wiring rules, see Nos. 24 and 25.)

a. Each length of conduit, whether insulated or uninsulated, must have the maker's name or initials stamped in the metal or attached thereto in a satisfactory manner, so that inspectors can readily see the same.

Insulated Metal Conduits:

b. The metal covering, or pipe, must be at least equal in thickness or of equal strength to resist penetration by nails, etc., as the ordinary commercial form of gas pipe of same size.

c. Must not be seriously affected externally by burning out a wire inside the tube when the iron pipe is connected to one side of the circuit.

d. Must have the insulating lining firmly secured to the pipe.

e. The insulating lining must not crack or break when a length of the conduit is uniformly bent at temperature of 212 degrees Fahrenheit to an angle of ninety degrees, with a curve having a radius of fifteen inches, for pipes of one inch and less, and fifteen times the diameter of pipe for larger sizes.

f. The insulating lining must not soften injuriously at a temperature below 212 degrees Fahrenheit and must leave water in which it is boiled practically neutral.

g. The insulating lining must be at least one thirty-second of an inch in thickness, and the materials of which it is composed must be of such a nature as will not have a deteriorating effect on the insulation of the conductor, and be sufficiently tough and tenacious to withstand the abrasion test of drawing in and out of same long lengths of conductors.

h. The insulating lining must not be mechanically weak after three days' submersion in water, and, when removed from the pipe entire, must not absorb more than ten per cent of its weight of water during 100 hours of submersion.

i. All elbows or bends must be so made for the purpose, and not bent from lengths of pipe. The radius of the curve of the inner edge of any elbow must not be less than three and one-half inches. Must have not more than the equivalent of four quarter bends from outlet to outlet, the bends at the outlets not being counted.

Uninsulated Metal Conduits:

j. Plain iron or steel pipes of equal thickness, or of equal strength, to resist penetration of nails, etc., as the ordinary commercial form of gas pipe of the same size, may be used as conduits, provided their interior surfaces are smooth and free from burs; pipe to be galvanized, or the interior surfaces coated or enameled to prevent oxidation with some substance which will not soften so as to become sticky and prevent the wire from being withdrawn from the pipe.

k. All elbows must be made for the purpose, and not bent from lengths of pipe. The radius of the curve of the inner edge of any elbow not to be less than three and one-half inches. Must have no more than the equivalent of four quarter bends from outlet to outlet, the bends at the outlets not being counted.

42. Wooden Mouldings—

(For wiring rules, see No. 24.)

a. Must have, both outside and inside, at least two coats of waterproof paint, or be impregnated with a moisture repellent.

b. Must be made in two pieces, a backing and capping so constructed as to thoroughly incase the wire, and provide a one-half inch tongue between the conductors, and a solid backing, which, under grooves, shall not be less than three-eighths of an inch in thickness, and must afford suitable protection from abrasion.

43. Switches—

(See Nos. 17 and 22.)

a. Must be mounted on non-combustible, non-absorptive, insulating bases, such as slate or porcelain.

b. Must have carrying capacity sufficient to prevent undue heating.

c. Must, when used for service switches, indicate, on inspection, whether the current be "on" or "off".

d. Must be plainly marked where it will always be visible, with the name of the maker and the current and voltage for which the switch is designed.

e. Must, for constant potential systems, operate successfully at fifty per cent overload in amperes, with twenty-five per cent excess voltage under the most severe conditions they are liable to meet with in practice.

f. Must, for constant potential systems, have a firm and secure contact; must make and break readily, and not stop when motion has once been imparted by the handle.

g. Must, for constant current systems, close the main circuit and disconnect the branch wires when turned "off"; must be so constructed that they shall be automatic in action, not stopping between points when started, and must prevent an arc between the points under all circumstances. They must indicate, upon inspection, whether the current be "on" or "off".

44. Cut-outs and Circuit Breakers—

(For installation rules, see Nos. 17 and 21.)

a. Must be supported on bases of non-combustible, non-absorptive insulating material.

b. Cut-outs must be provided with covers, when not arranged in approved cabinets, so as to obviate any danger of the melted fuse metal coming in contact with any substance which might be ignited thereby.

c. Cut-outs must operate successfully, under the most severe conditions they are liable to meet with in practice, on short circuits with fuses rated at 50 per cent above and with a voltage 25 per cent above the current and voltage for which they are designed.

d. Circuit-breakers must operate successfully, under the most severe conditions they are liable to meet with in practice, on short circuits when set at fifty per cent above the current, and with a voltage twenty-five per cent above that for which they are designed.

e. Must be plainly marked where it will always be visible, with the name of the maker, and current and voltage for which the device is designed.

45. Fuses—

(For installation rules, see Nos. 17 and 21.)

a. Must have contact surfaces or tips of harder metal having perfect electrical connections with the fusible part of the strip.

b. Must be stamped with about eighty per cent of the maximum current they can carry indefinitely, thus allowing about twenty-five per cent overload before fuse melts.

c. Fuse terminals must be stamped with the maker's name, initials, or some known trademark.

46. Cut-out Cabinets—

a. Must be so constructed, and cut-outs so arranged, as to obviate any danger of the melted fuse metal coming in contact with any substance which might be ignited thereby.

47. Sockets—

(See No. 27.)

a. No portion of the lamp socket, or lamp base, exposed to contact with outside objects, must be allowed to come into electrical contact with either conductor.

b. Must, when provided with keys, comply with the requirements for switches. (See No. 43.)

48. Hanger-boards—

a. Hanger-boards must be so constructed that all wires and current-carrying devices thereon shall 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.

57. Arc Lamps.

(For installation rules, see No. 19.)

a. Must be provided with reliable stops to prevent carbons from falling out in case the clamps become loose.

b. Must be carefully insulated from the circuit in all their exposed parts.

c. Must, for constant-current systems, be provided with an approved hand switch, also an automatic switch that will shunt the current around the carbons, should they fail to feed properly. The hand switch to be approved, if placed anywhere except on the lamp itself, must comply with requirements for switches on hanger-boards as laid down in Rule 48.

50. Spark Arresters—

(For installation rules, see Nos. 19 c.)

a. Spark arresters must so close the upper orifice of the globe that it will be impossible for any sparks, thrown off by the carbons, to escape.

51. Insulating Joints—

(See No. 26 a.)

a. Must be entirely made of material that will resist the action of illuminating gases, and will not give way or soften under the heat of an ordinary gas flame or leak under a moderate pressure. They shall be so arranged that a deposit of moisture will not destroy the insulating effect, and shall have an insulating resistance of at least 250,000 ohms between the gas-pipe attachments, and be sufficiently strong to resist the strain they will be liable to be subjected to in being installed.

b. Insulating joints having soft rubber in their construction will not be approved.

52. Resistance Boxes and Equalizers—

(For installation rules, see No. 4)

a. Must be equipped with metal, or with other non-combustible frames.

53. Reactive Coils and Condensers—

a. Reactive coils must be made of non-combustible material, mounted on non-combustible bases and treated, in general, as sources of heat.

b. Condensers must be treated like apparatus operating with equivalent voltage and currents. They must have non-combustible cases and supports, and must be isolated from all combustible materials and, in general, treated as sources of heat.

54. Transformers—

(For installation rules, see Nos. 11 and 33.)

a. Must not be placed in any but metallic or other non-combustible cases.

55. Lightning Arresters—

(For installation rules, see No. 5.)

a. Must be mounted on non-combustible bases, and must be so constructed as not to maintain an arc after the discharge has passed, and must have no moving parts.

Class E.

MISCELLANEOUS.

56. Insulation Resistance—

The wiring in any building must test free from 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 the following:

Up to 5 amperes	4,000,000
Up to 10 amperes	2,000,000
Up to 25 amperes	800,000
Up to 50 amperes	400,000
Up to 100 amperes	200,000
Up to 200 amperes	100,000
Up to 400 amperes	50,000
Up to 800 amperes	25,000
Up to 1,600 amperes and over	12,500
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.

57. Protection against Foreign Currents.

a. Where telephone, telegraph or other wires, connected with outside circuits, are bunched together within any building, or where inside wires are laid in conduits or ducts with electric light or power wires, the covering of such wires must be fire-resisting, or else the wires must be inclosed in an air-tight tube or duct.

b. All aerial conductors and underground conductors, which are directly connected to aerial wires, connecting with telephone, telegraph, district messenger, burglar-alarm, watch-clock, electric-time and other similar instruments must be provided near the point of entrance to the building with some approved protective device which will operate to shunt the instruments in case of a dangerous rise of potential, and will open the circuit and arrest any abnormal current flow. Any conductor normally forming an innocuous circuit may become a source of fire hazard if crossed with another conductor charged with a relatively high pressure. Protectors must have a non-combustible, insulating base, and the cover to be provided with a lock similar to the lock now placed on telephone apparatus or some equally secure fastening, and to be installed under the following requirements:

1. The protector to be located at the point where the wires enter the building, either immediately inside or outside of the same. If outside, the protector to be enclosed in a metallic, waterproof case.
2. If the protector is placed inside of building, the wires of the circuit from the support outside to the binding posts of the protector to be of such insulation as is approved for service wires of electric light and power (See No. 40 a) and the holes through the outer wall to be protected by bushing the same as required for electric light and power service wires.
3. The wire from the point of entrance to the protector to be run in accordance with rules for high-potential wires, i. e., free of contact with building and supported on non·combustible insulators.
4. The ground wire shall be insulated, not smaller than No. 16 B. & S. gauge copper wire. This ground wire shall be kept at least three inches from all conductors, and shall never be secured by uninsulated, double-pointed tacks, and must be run in as straight a line as possible to the ground connection.
5. The ground wire shall be attached to a water pipe, if possible, otherwise may be attached to a gas pipe. The ground wire shall be carried to, and attached to, the pipe outside of the first joint or coupling inside the foundation walls, and the connection shall be made by soldering, if possible. In the absence of other good ground, the ground shall be made by means of a metallic plate or a bunch of wires buried in a permanently moist earth.

58. Electric Gas Lighting—

Where electric gas lighting is to be used on the same fixture with the electric light:

a. No part of the gas piping or fixture shall be in electric connection with the gas lighting circuit.

b. The wires used with the fixtures must have a non-inflammable insulation, or, where concealed between the pipe and shell of the fixture, the insulation must be such as required for fixture wiring for the electric light.

c. The whole installation must test free from "grounds".

d. The two installations must test perfectly free from connection with each other.

59. Soldering Fluid—

a. The following formula for soldering fluid is suggested:

Saturated solution of zinc chloride	5 parts
Alcohol	4 parts
Glycerine	1 part

Approved Materials.

Wires—

The following is a list of wires constructed to comply with the standard given in Rule 40 a. Result of recent tests on these and on other wires can be seen at inspection offices:

Name of Wire.	Manufacturer.
Americanite	American Electrical Works.
Bishop	Bishop Gutta Percha Co.
Clark	Eastern Electric Co.
Climax	Simplex Electric Co.
Simplex (caoutchouc)	Simplex Electric Co.
Acme	Simplex Electrical Co.
C. C.	Canadian General Electric Co.
Crescent	John A. Roebling's Sons Co.
Crown	Washburn & Moen.
Glove	Washburn & Moen.
Crefeld	Crefeld Electrical Works.
Grimshaw (White core)	N. Y. Insulated Wire Co.
Raven (Black core)	N. Y. Insulated Wire Co.
Raven (White core)	N. Y. Insulated Wire Co.
Safety (Black core)	Safety Insulated Wire and Cable Co.
Habirshaw (White core)	Safety Insulated Wire and Cable Co.
Habirshaw (Blue core)	Ind. Rubber and Gutta Percha Ins. Co.
Habirshaw (Red core)	Ind. Rubber and Gutta Percha Ins. Co.
Paranite	Indiana Rubber & Insulated Wire Co.
Liberty	Atlas Covering Works.
Kerite	W. R. Brixey.
Okonite	Okonite Co., Limited.
Paracore	Nat. India Rubber Co.
N. I. R.	Nat. India Rubber Co.
Double Rubber Core	General Electric Co.
Double Rubber (Red core)	General Electric Co.
Sterling	Standard Underground Cable Co.
Tip Top	Standard Underground Cable Co.
Phillips	Phillips Insulated Wire Co.

Materials—

The following are given as a list of NON-COMBUSTIBLE, NON-ABSORPTIVE, INSULATING materials and are listed here for the benefit of those who might consider hard rubber, fiber, wood and the like as fulfilling the above requirements. Any other substance, which it is claimed should be accepted, must be forwarded for testing before being put on the market:

1. Glass.
2. Marble (filled).
3. Slate without metal veins.
4. Porcelain, thoroughly glazed and vitrified.
5. Pure Sheet Mica.
6. Lava (certain kinds of).
7. Alberene Stone.

Iron-Armored Insulated Conduits—

The iron and steel-armored conduits manufactured by the Interior Conduit and Insulation Company, the Armorite Company, the Clifton Manufacturing Company, and the Consolidated Tube Company have been tested and, in general, have given good results in practice.

Flexible Tubing—

(See No. 24 t.)

American Circular Loom tubing is approved for use under rule 24, section t.

Class F.

MARINE WORK.

60. Generators—

a. Must be located in a dry place.

b. Must have their frames insulated from their bed-plates.

c. Must each be provided with a waterproof cover.

d. Must each be provided with a name plate, giving the maker's name, the capacity in voltage and amperes and normal speed in revolutions per minute.

61. Wires.

a. Must have an approved insulating covering.

b. Must have no single wire larger than No. 12 B. & S. Wires to be stranded when greater carrying capacity is required. No single solid wire smaller than No. 14 B. & S., except in fixture wiring, to be used.

c. Must be supported in approved molding or conduit, except at switchboards and portables.

d. Must be bushed with hard rubber tubing one-eighth inch in thickness when passing through beams and non-water-tight bulkheads.

e. Must have when passing through water-tight bulkheads and through all decks, a metallic stuffing tube lined with hard rubber. In case of deck tubes they shall be boxed near deck to prevent mechanical injury.

f. Splices or taps in conductors must be avoided as far as possible. Where it is necessary to make them they must be so spliced or joined as to be both mechanically and electrically secure without solder. They must then be soldered, to insure preservation, covered with an insulating compound equal to the insulation of the wire, and further protected by a waterproof tape. The joint must then be coated or painted with a waterproof compound.

62. Portable Conductors—

a. Must be made of two stranded conductors, each having a carrying capacity equivalent to not less than No. 14 B. & S. wire, and each covered with an approved insulation and covering.

63. Bell or Other Wires—

a. Shall never be run in same duct with lighting or power wires.

64. Table of 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	2,048	..	..	..
16	2,583	..	..	6
15	3,257	..	..	..
14	4,107	..	..	12
12	6,530	..	..	17
..	9,016	7	19	21
..	11,368	7	18	25
..	14,336	7	17	30
..	18,081	7	16	35
..	22,799	7	15	40
..	30,856	19	18	50
..	38,912	19	17	60
..	49,077	19	16	70
..	60,088	37	18	85
..	75,776	37	17	100
..	99,064	61	18	120
..	124,928	61	17	145
..	157,563	61	16	170
..	198,677	61	15	200
..	250,527	61	14	235
..	296,387	91	15	270
..	373,737	91	14	320
..	413,639	127	15	340

65. Switchboards—

a. Must be made of non-combustible, non-absorptive, insulating material, such as marble or slate.

b. Must be kept free from moisture, and must be located so as to be accessible from all sides.

c. Must have a main switch, main cut-out and ammeter for each generator. Must also have a voltmeter and ground detector.

d. Must have a cut-out and switch for each side of each circuit leading from board.

66. Resistance Boxes—

a. Must be made of non-combustible material.

b. Must be located on switchboard or away from combustible material. When not placed on switchboard they must be mounted on non-inflammable, non-absorptive insulating material.

c. Must be so constructed as to allow sufficient ventilation for the uses to which they are put.

67. Switches—

a. Must have non-combustible, non-absorptive, insulating bases.

b. Must operate successfully at fifty per cent overload in amperes with twenty-five per cent excess voltage under the most severe conditions they are liable to meet with in practice, and must be plainly marked where it will always be visible, with the name of the maker and the current and voltage for which the switch is designed.

c. Must be double-pole when circuits which they control supply more than six 16-candle-power lamps or their equivalent.

d. When exposed to dampness, they must be enclosed in a water-tight case.

68. Cut-outs—

a. Must have non-combustible, non-absorptive, insulating bases.

b. Must operate successfully, under the most severe conditions they are liable to meet with in practice, on short circuit with fuse rated at fifty per cent above, and with a voltage twenty-five per cent above the current and voltage they are designed for, and must be plainly marked where they will always be visible with the name of the maker and current and voltage for which the switch is designed.

c. Must be placed at every point where a change is made in the size of the wire (unless the cut-out in the larger wire will protect the smaller).

d. In places such as upper decks, holds, cargo spaces and fire rooms a water-tight and fireproof cut-out may be used, connecting directly to mains when such cut-out supplies circuits requiring not more than six 16-candle-power lamps or their equivalent.

e. When placed anywhere except on switch-boards and certain places, as cargo spaces, holds, fire-rooms, etc., where it is impossible to run from center of distribution, they shall be in a cabinet lined with fire-resisting material.

f. Except for motors, search-lights and diving lamps shall be so placed that no group of lamps, requiring a current of more than six amperes, shall ultimately be dependent upon one cut-out.

69. Fixtures—

a. Shall be mounted on blocks made from well-seasoned lumber treated with two coats of white lead or shellac.

b. Where exposed to dampness, the lamp must be surrounded by a vapor-proof globe.

c. Where exposed to mechanical injury, the lamp must be surrounded by a globe protected by a stout wire guard.

d. Shall be wired with same grade of insulation as portable conductors which are not exposed to moisture or mechanical injury.

70. Sockets—

a. No portion of the lamp socket or lamp base exposed to contact with outside objects shall be allowed to come into electrical contact with either of the conductors.

71. Wooden Mouldings—

a. Must be made of well seasoned lumber, and be treated inside and out with at least two coats of white lead or shellac.

b. Must be made of two pieces, a backing and a capping, so constructed as to thoroughly incase the wire and provide a one-half-inch tongue between the conductors, and a solid backing which, under grooves, shall not be less than three-eighths inch in thickness.

c. Where moulding is run over rivets, beams, etc., a backing strip must first be put up and the moulding secured to this.

d. Capping must be secured by brass screws.

72. Motors—

a. Must be wired under the same precautions as with a current of same volume and potential for lighting. The motor and resistance box must be protected by a double-pole cut-out and controlled by a double-pole switch, except in cases where one-quarter horse-power or less is used.

b. Must be thoroughly insulated. Where possible, should be set on base frames made from filled, hard, dry wood and raised above surrounding deck. On hoists and winches they shall be insulated from bed-plates by hard rubber, fiber or similar insulating material.

c. Shall be covered with a waterproof cover when not in use.

d. Must each be provided with a name plate giving maker's name, the capacity in volts and amperes and the normal speed in revolutions per minute.

INDEX.

	RULE AND SECTION.
Acid fumes	10 (c) & 24 (j) and (k)
Arc lamps, Construction of	49
Arc lamps, Installation of	19
Arc lamps, On low-potential circuits	29
Base frames, Generators and motors	1 (i), 8 (a)
Batteries, Storage or primary	10
Binding screws, not to bear strain	8 (f)
Bonds, rails and car houses	35 (g)
Boxing, where necessary	18 (e), 24 (f) 32 (d)
Breweries	24 (i) to (k)
Burglar alarms	57 (b)
Burrs and fins. Fixture work.	26 (b)
Bushings, For wires	14 (d)
Bushings, Lamp sockets	28 (e)
Bus bars	2 (b), 3 (e)
Cabinets for cut-outs	46
Care and attendance	6
Car houses	35
Carrying capacity table	16
Car wiring	34
Central stations	1 to 7
Circuit breakers, Construction of	44
Circuit breakers, Installation of	17, 21 (e)
Compensator coils	30
Concealed wiring	24 (a) to (f) & (r) to (t)
Condensers	53 (b)
Conductors	(See Wires.)
Conduits, Installation of	25
Conduits, Insulated approved list	page 45
Conduits, Insulated metal	41 (b) to (i)
Conduits, To be marked	41 (a)
Conduits, Uninsulated metal	41 (j) & (k)
Conduit work	24 (m) to (q)
Constant-current systems	18 to 20
Constant-potential systems, General Rules	21 to 23
Converters.	(See Transformers.)
Cut-out cabinets
Cut-outs, Construction of	44
Cut-outs, Installation of	17 to 21
Cut-outs, Marine work	68
Cut-outs, To be double pole	17 (a)
Decorative series lamps	31
Distance between conductors, inside	18 (d), 24 (h), (j), & (s)
Distance between conductors, outside	12 (b)
Drip loops at service entrances	12 (g)
Dynamo rooms	1 to 7
Economy coils	30
Electric gas lighting	58
Electric heaters	23
Electro-magnetic devices for switches	20 (c)
Equalizers	(See resistance boxes)
Extra high-potential systems	38 & 39
Feeders, Railway	35 (f)
Fished wires	24 (c) & (t)
Fittings and materials	40 to 55
Fixtures	26
Fixtures, Marine work	69
Fixture wire	40 (d)
Fixture wiring	24 (u) to (w)
Flexible cord, Construction of	40 (c)
Flexible cord, Construction of, Heaters	40 (c-3)
Flexible cord, Construction of, Pendants	40 (c-1)
Flexible cord, Construction of, Portables	40 (c-2)
Flexible cord, Use of	28
Flexible tubing	page 45
Foreign currents, protection against	57
Formula for soldering fluid	59
Fuses, Construction of	25
Fuses, Installation of	21
Gas lighting, Electric	58
General plan of rules	page 3
General suggestions	page 4
Generators	1
Generators, Marine work	60
Grounded circuits	36
Grounding of dynamo and motor frames	1 (c-8) (a)
Grounds, Testing for	7
Ground wire for lightning arresters	5-c, 57 (b-5)
Hanger-boards, Construction of	48
Hanger-boards, When not used	19-d
Heaters, Electric	23
High, constant-potential systems	32 to 37
Incandescent lamps as resistances	29-b
Inside work	14 to 39
Insulating joints, Construction of	51
Insulating joints, When required	26-a
Insulation of trolley wires	12-k
Insulation resistance	56
Interior conduits.	(See conduits)
Joints, in conductors	12-f, 14-c
Joints, in interior conduits	25-d
Joints, Insulating.	(See Insulating Joints)
Lamps, Arc	(See Arc Lamps)
Lamps, Incandescent series	20
Lightning arresters, Construction of	55
Lightning arresters, Installation of	5
Lights from trolley circuits	36
Low-potential systems	24 to 31
Marine work	60 to 72
Materials, Approved	pages 44 & 45
Mechanical injury, Protection against	18-e, 24-e, 32-d
Motors	8
Motors, Marine work	72
Moulding, Construction of	42
Moulding, Marine work	71
Moulding work	24-a to f, l, & m
Oily waste	6-b
Open wiring	24-a to k
Outside work	12 & 13
Portable conductors	40 (c-2)
Portable conductors for marine work	62
Protective devices, signal circuits	57-b
Power from trolley circuits	36
Railway power plants	9
Reactive coils	53-a
Resistance boxes, Construction of	52
Resistance boxes, Installation of	4
Resistance boxes, Marine work	66
Resistances for arc lamps, Low-potential	29-b
Series lamps	31 & 37
Service blocks	12-b
Sockets, Construction of	47
Sockets, Installation of	27
Sockets, Marine work	70
Soldering fluid formula	59
Spark arresters, Construction of	50
Spark arresters, When required	19-c, 29-c
Storage battery rooms	10
Switchboards	8
Switchboards, Marine work	65
Switches, Construction of	43
Switches, Electro-magnetic	20-c
Switches, Installation of	17 & 22
Switches, Marine work	67
Switches, To be double pole	17-a
Switches, When may be single pole	8-c, 22-c
Systems, Constant-current	18 to 20
Systems, Constant-potential	21 to 39
Systems, Extra high, constant-potential	38 & 39
Systems, High, constant-potential	32 to 37
Systems, Low, constant-potential	21 to 31
Telegraph, telephone, and other signal circuits	57
Testing	7
Transformers in central stations	11
Transformers, Construction of	54
Transformers, Inside	33
Transformers, Outside	13
Tubing, Flexible	page 45
Wire, Concentric	47-e
Wire, Fixtures	40-d
Wire, Insulated conduit	40-e, l
Wire, Insulation of	40
Wire, Netting required on arc lamps	19-c, 29-c
Wire, Rubber-covered	40-a
Wire, Uninsulated conduit	40 (e-2)
Wire, Weatherproof	40-b
Wires, Carrying capacity table	16
Wires, Carrying capacity table, Marine work	64
Wires, Central stations	2
Wires, Concealed work	24-r to t
Wires, Conduit work	24-n to q
Wires, Distance between, inside	18-d, 24-h, j & s
Wires, Distance between, outside	12-b
Wires, Extra high-potential	38 & 39
Wires, Fished	24-c & t
Wires, General rules, low-potential	24-a to f
Wires, Ground return	12-m
Wires, High-potential	32
Wires, Inside, constant-current	18
Wires, Inside, general rules	14
Wires, Underground	15
Wires, Marine work	61
Wires, Moulding work	24-l & m
Wires, Open work, damp places	24-i to k
Wires, Open work, dry places	24-g & h
Wires, Outside, overhead	12
Wires, Rubber covered, approved list	page 44
Wires, Trolley	12-j to m

Results of recent tests made under the specifications given in Class D for cut-outs, switches, conduits, wires, circuit breakers, fuses, etc., can be seen at inspection offices, and should be consulted in all cases where any doubt exists as to the ability of any particular device to successfully meet the requirements given. Copies of laboratory reports on all devices can be obtained by architects, building owners and contractors by addressing the Electrical Bureau of the National Board of Fire Underwriters at the Chicago office, No. 157 LaSalle Street, to which address new devices, or devices on which tests are required, should be sent.

Errata

• Rule 43. Fuses, note to subsection b: This note identifies the "maximum" current which melts a naked open fuse in five minutes as the taken melting point. In future code cycles, this is properly changed to "minimum", which appears to be the ultimate idea.
• Rule 57's name is formatted irregularly, with a period instead of an m-dash at the end of the title.