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before the conductors are drawn into a fixture.
f. The tendency to condensation within the pipes should be guarded
ist by sealing the upper end of the fixture.
g. 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.
h. Each fixture must be tested for o contacts” between conductors and fix. tures, for“ short circuits,” and for ground connections before the fixture is connected to its supply conductors.
i. Ceiling blocks of fixtures should be made of insulating material; if not, the wires in passing through the plate must be surrounded with hard rubber tubing. 28. ARC LIGHTS ON Low POTENTIAL CIR
a. Must be supplied by branch conductors not smaller than No. 12 B. & S. gauge.
b. Must be connected with main conductors only through double pole cut-outs.
c. Must only be furnished with such resistances or regulators as are enclosed in non-combustible material, such resistances being treated as stoves.
Incandescent lamps must not be used for resistance devices.
d. Must be supplied with globes and protected as in the case of arc lights on high potential circuits. 29. 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 electrical 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 wir. ing 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. 30. SOCKETS:
a. No portion of the lamp socket exposed to contact with outside objects must be allowed to come into electrical contact with either of the conductors.
b. In rooms where inflammable gases may exist, or where the atmosphere is damp, the incandescent lamp and socket should be enclosed in a vapor-tight globe. 31. FLEXIBLE CORD:: a. Must be made of conductors, each surrounded with a moisture-proof and a non-inflammable layer, and further insulated from each other by a mechanical separator of carbonized material. Each of these conductors must be composed of several strands.
b. Must not sustain more than one light not exceeding 50 candle-power.
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. The ends of the cord must be taped, to prevent fraying of the covering.
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.
g. Must be equipped with keyless sockets as far as practicable, and be controlled by wall switches. RULE 32. DECORATIVE SERIES LAMPS.
Incandescent lamps run in series circuits shall not be used for decorative purposes inside of buildings.
Class D. ALTERNATING SYSTEMS. — CONVERTERS OR
TRANSFORMERS. 33. CONVERTERS:-
a. Must not be placed inside of any building, except the Central Station, unless by special permission of the Underwriters having jurisdiction.
b. Must not be placed in any but metallic or other non-combustible cases.
c. Must not be attached to the outside walls of buildings, unless separated therefrom by substantial insulating supports. IN THOSE CASES WHERE IT MAY NOT BE POS
SIBLE TO EXCLUDE THE CONVERTERS AND PRIMARY WIRES ENTIRELY FROM THE BUILDING, THE FOLLOWING PRECAUTIONS MUST BE STRICTLY OBSERVED:-34. Converters must be located at a point as near as possible to that at which the primary wires enter the building, and must be placed in a room or vault constructed of, or lined with, fire-resisting material, and used only for the purpose. They must be effectually insulated from