With the high voltage coil connected to a circuit of the rated voltage and frequency and with the low voltage coils short circuited, the input as measured by wattmeter must not exceed 250 watts. When so connected, and run until constant temperature is reached or until burnout occurs, the case must not be injured and there must be no escape of flames or molten metal.

§ 582. Lightning arresters.-a. Lightning arresters must be of approved construction.

8583. Electric signs (for low potential systems only).— -a. Electric signs shall be constructed entirely of metal, or other incombustible material, except the insulation of the wires. Sheet metal must be not less than 28 U. S. sheet metal gage. All metal must be galvanized, enameled, treated with at least 3 coats of anti-corrosive paint, or otherwise protected in an approved manner against corrosion.

b. Electric signs must be so constructed as to secure ample strength and rigidity. Electric signs must be so constructed as to be practically weatherproof and to enclose all terminals and wiring other than the supply leads, except that open work will be permitted for signs on roofs or open ground where not subject to mechanical injury, provided the wiring is in accordance with paragraph e of this section. Transformers, unless of weatherproof type, cut-outs, flashers and other similar devices on or within the sign structure, must be enclosed in approved cut-out boxes or cabinets, except that if on or within the sign structure they may be placed in a separate, completely enclosed compartment, or in a substantial weatherproof box or cabinet of metal of thickness not less than that of the metal of the sign itself. Each compartment must have suitable provision for drainage through one or more holes, each not less than 4 inch in diameter.

c. Electric signs must have the maker's name or trade-mark permanently attached to the exterior.

d. Receptacles must be so designed as to afford permanent and reliable means to prevent possible turning; must be so designed and placed that terminals will be at least 1/2 inch from other terminals and from metal of the sign, except that where open work is permitted this separation must be 1 inch. Miniature receptacles will not be approved for use in outdoor signs.

e. Wiring must be approved rubber covered, not less than No. 14 B. & S. gage. Wiring must be neatly run and so disposed and fastened as to be mechanically secure. Wires must be soldered to terminals, and exposed parts of wires and terminals must be treated to prevent corrosion. Wires must, where they pass through walls or partitions of the sign be protected by approved bushings. On outside of sign structure, except where open work is permitted, wires must be in approved metal conduit or in approved lead sheathed armored cable.

For open work wires must be rigidly supported on non-combustible, non-absorptive insulators which separate the wires at least 1 inch from the surface wired over. Rigid supporting requires, under ordinary conditions, where wiring over flat surfaces, supports at least every 42 feet. If the wires are liable to be disturbed the distance between supports should be shortened. In those parts of circuits where wires are connected to approved receptables which hold

them at least 1 inch from surface wired over, and which are placed not over 1 foot apart, such receptacles will be considered to afford the necessary support and spacing of the wires. Between receptacles more than 1 foot, but less than 2 feet, apart an additional noncombustible, non-absorptive insulator maintaining separation and spacing equivalent to the receptacles, must be used. Except as above specified wires must be kept apart at least 22 inches for voltages up to 300, and 4 inches for higher voltages.

f. Leads from signs must pass through the walls of the sign either through approved metal conduit or armored cable, or must be neatly cabled and pass through one or more bushings of approved noncombustible, non-absorptive insulated material.

g. Not over 1,320 watts shall be dependent upon final cut-out.

ARTICLE 6

MISCELLANEOUS

(As amend. by ord. effective May 29, 1916)

Sec. 685. Signaling systems.

§ 686. Wireless telegraph apparatus.

687. Electric gas lighting.

688. Insulation resistance.

Sec. 685. Signaling systems. 1. Exception.-All wiring, apparatus and devices of signaling systems used for the transmission of intelligence as to fire, shall conform to such rules and regulations as the fire commissioner may prescribe.

2. Outside wires. a. Outside wires must be run in underground ducts or strung on poles, and kept off the roofs of buildings, except by special permission, and must not be placed on the same crossarm with electric light or power wires. They must not occupy the same duct, manhole or handhole of conduit systems with electric light or power wires. Single manholes or handholes separated into sections by means of partitions of brick or tile will be considered as conforming with the above requirement. When the entire circuit from central station to building is run in underground conduits, paragraphs b to m, inclusive, of this section do not apply.

h. When outside wires are run on same pole with electric light or power wires, the distance between the two inside pins of each-cross arm must not be less than 24 inches. When the wires are carried in approved cables, paragraphs c, d and e of this section do not apply. c. Where wires are attached to the outside walls of buildings they must have an approved rubber insulating covering, and on frame buildings or frame portions of other buildings shall be supported on glass or porcelain insulators or knobs.

d. The wires from last outside support to the cut-outs or protectors must be of copper, and must have an approved rubber insulation; must be provided with drip loops immediately outside the building and at entrance.

e. Wires must enter building through approved non-combustible,

non-absorptive insulating bushings sloping upward from the outside, and both wires may enter through the same bushing, if desired.

3. Ten ampere installations. f. An all-metallic circuit shall be provided, except in telegraph systems.

g. At the entrance of wires to building, approved single pole cut-outs, designed for 251-600 volts potential and containing fuses rated at not over 10 amperes capacity, shall be provided for each wire. These cut-outs 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.

h. The wires inside building shall be of copper not less than No. 16 B. & S. gage, and must have insulation and be supported, the same as would be required for an installation of electric light or power wiring, 0-600 volts potential.

i. The instruments shall be mounted on bases constructed of noncombustible, non-absorptive insulating material. Holes for the supporting screws must be so located, or counter-sunk, that there will be at least 1-2 inch space, measured over the surface, between the head of the screw and the nearest live metal part.

4. Less than 10 ampere installations. j. Wires must be provided with an approved protective device located as near as possible to the entrance of wires to building. The protector must not be placed in the immediate vicinity of easily ignitible stuff, or where exposed to inflammable gases or dust or flyings of combustible materials.

k. Wires from entrance to building to protector must be supported on porcelain insulators, so that they will come in contact with nothing except their designed supports.

I. The ground wire of the protective device shall be run in accordance with the following requirements:

1. Shall be of copper and not smaller than No. 18 B. & S. gage. 2. Must have an insulating covering approved for voltages from 0 to 600, except that the preservative compound may be omitted.

3. Must run in as straight a line as possible to a good permanent ground. This may be obtained by connecting to a water or gas pipe connected to the street mains or to a ground rod or pipe driven in permanently damp earth. When connections are made to pipes, preference shall be given to water pipes. If attachment is made to gas pipe, the connection in all cases must be made between the meter and the street mains. In every case the connection shall be made as near as possible to the earth. When the ground wire is attached to a water pipe or gas pipe, it may be connected by means of an approved ground clamp fastened to a thoroughly clean portion of said pipe, or the pipe shall be thoroughly cleaned and tinned with rosin flux solder, and the ground wire shall then be wrapped tightly around the pipe and thoroughly soldered to it. When the ground wire is attached to a ground rod driven into the earth, the ground wire shall be soldered to the rod in a similar manner. Steam or hot-water pipes must not be used for a protector ground.

m. The protector to be approved must comply with the following requirements:

1. For instrument circuits of telegraph systems, an approved single pole cut-out in each wire, designed for 2,000 volts potential, and containing fuses rated at not over 1 ampere capacity. When

main line cut-outs are installed as called for in paragraph g of this section the instrument cut-outs may be placed between the switchboard and the instrument as near the switchboard as possible;

2. In all other systems the protector must be mounted on noncombustible, non-absorptive insulating bases, so designed that when the protector is in place, all parts which may be alive will be thoroughly insulated from the wall to which the protector is attached. The protector must have the following parts:

A lightning arrester which will operate with a difference of potential between wires of not over 500 volts, and so arranged that the chance of accidental grounding is reduced to a minimum;

A fuse designed to open the circuit in case the wires become crossed with light or power circuits. The fuse must be able to open the circuit without arcing or serious flashing when crossed with any ordinary commercial light or power circuit,

A heat coil, if the sensitiveness of the instrument demands it, which will operate before a sneak current can damage the instrument the protector is guarding;

Heat coils are necessary in all circuits normally closed through magnet windings, which cannot indefinitely carry a current of at least 5 amperes;

The heat coil is designed to warm up and melt out with a current large enough to endanger the instruments if continued for a long time, but so small that it would not blow the fuses ordinarily found necessary for such instruments.

3. The fuses must be so placed as to protect the arrester and heat coils, and the protector terminals must be plainly marked "line," 'instrument," ," "ground." An easily read abbreviation of the above words will be allowed.

5. Generally. The following rules apply to all systems whether the wires from the central office to the building are overhead or underground:

n. Wires beyond the protector, or wires inside buildings where no protector is used, must be neatly arranged and securely fastened in place in some convenient, workmanlike manner. They must not come nearer than 2 inches to any electric light or power wire in the building, unless separated therefrom by some continuous and firmly fixed non-conductor creating a permanent separation; this nonconductor to be in addition to the regular insulation on the wire.

o. Wires where bunched together in a vertical run within any building must have a fire-resisting covering sufficient to prevent the wires from carrying fire from floor to floor unless they are run either in non-combustible tubing or in a fireproof shaft, which shaft must be provided with fire stops at each floor. Signaling wires and electric light or power wires may be run in the same shaft, provided that one of these classes of wires is run in non-combustible tubing, or provided that when run otherwise these two classes of wires shall be separated from each other by at least 2 inches. In no case shall signaling wires be run in the same tube with electric light or power wires.

p. Transformers or other devices for supplying current to signaling systems from light, heat or power circuits must be of a design expressly approved for this purpose. The primary wiring must be installed in accordance with the requirements of article 4 of this

chapter, and the secondary wiring in accordance with this article. §686. Wireless telegraph apparatus. In setting up wireless telegraph apparatus, all wiring within the building must conform to the requirements of this chapter for the class of work installed and to the following additional specifications:

a. Aerial conductors must be permanently and effectively grounded at all times when station is not in operation by a conductor not smaller than No. 4 B. & S. gage copper wire, run in as direct line as possible to water pipe at a point on the street side of all connections to said water pipe within the premises, or to some other equally satisfactory earth connection.

b. Aerial conductors when grounded as above specified must be effectually cut off from all apparatus within the building.

c. Or the aerial must be permanently connected at all times to earth in the manner specified above, through a short-gap lightning arrester, said arrester to have a gap of not over .015 inch between brass or copper plate, not less than 211⁄2 inches in length parallel to the gap, and 12 inches the other way with a thickness of not less than 1/8 inch mounted upon non-combustible, non-absorptive insulating material of such dimensions as to give ample strength. Other approved arresters of equally low resistance and equally substantial construction may be used.

d. In cases where the aerial is grounded as specified in paragraph a of this section, the switch employed to join the aerial to the ground connection shall not be smaller than a standard 100 ampere knife switch.

e. Where supply is obtained direct from the street service the circuit must be installed in approved metal conduits or armored cable. In order to protect the supply system from high potential surges, there must be inserted in circuit either a transformer having a ratio which will give a potential on the secondary leads not to exceed 550 volts, or two condensers in series across the line, the connection between said condensers to be permanently and effectually grounded. These condensers should have capacity of not less than 1/2 microfarad.

8687. Electric gas lighting.-a. Electrical gas lighting, unless it is the frictional system, must not be used on the same fixture with the electric light, except under special permission in writing.

§ 688. Insulation resistance.-The wiring in any building must comply with the following requirements. The complete installation must have a resistance between conductors and between all conductors and the ground (not including attachments, sockets, receptacles, etc.) not less than that given in the following table: