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concealed between the pipe and shell of the fixture the insulation must be such as is required for fixture wiring for the electric light.
3. The whole installation must test free from "grounds."
4. The two installations must test perfectly free of connection with each other.
Pendants and Sockets.
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.
Cord Pendants—Must be:
1. Made of conductors, each of which is composed of several strands insulated from the other conductor by a mechanical separator of carbonizable material, and both surrounded in damp places with a moisture-proof aud a non-inflammable layer.
2. Protected by insulating bushings where the cord enters the socket.
3. So suspended that the entire weight of the socket and lamp will be borne by knots, above the points where the cord comes through the ceiling block or rosette, in order that the strain may be taken from the joints and binding screws. All sockets used for wire or cord pendants should have openings at least equal to one-quarter inch gas pipe size.
4. Allowed to sustain nothing heavier than a four-light cluster, and in such a case sufficient provision should be made by an extra heavy cord or wire, as a mechanical reinforcement.
5. Equipped with keyless sockets as far as practicable, controlled by wall switches. In no case may a lamp giving more than fifty (50) candle-power be placed in a key socket on a flexible pendant.
CLASS D.—ALTERNATING SYSTEMS.
Converters or Transformers.
1. Be placed inside of any building except the central station unless as hereinafter provided.
2. Be placed in any but metallic or noncombustible cases.
3. Be attached to the outside walls of buildings, unless separated therefrom by substantial insulating supports.
4. Be placed in any other than a dry and convenient location (which can be secured from opening into the interior of the building such as a vault) when an underground service is UBed.
5. Be placed without safety fuses at the junction between main and service conductors and safety fuses in the secondary circuits where they will not be affected by the heat of the converter,
In those cases where it may not be possible to exclude the transformers and primary wires entirely from the building, the following precautions must be strictly observed:
1. The transformer must be located at a point as near as possible to that at which the primary wires enter the building.
2. Between these points the conductors must be heavily insulated with a coating of moisture-proof material, and, in addition, must be so covered and protected that mechanical injury to them or contact with them shall be practically impossible.
3. The primary conductors, if within a building, must be furnished with a double pole switch, and also with an automatic double pole cut-out where the wires enter the building, or where they leave the main line, on the pole or in the conduit. These switches should, if possible, be inclosed in secure and fireproof boxes outside the building.
4. The primary conductors, when inside a building, must be kept apart at least 10 inches, and at the same distance from all other conducting bodies.
The conductors from the secondary coil of the transformer to the lamps or other translating devices must be installed according to the rules for "inside wiring" for "low potential systems,"
CLASS E.—ELECTRIC RAILWAYS.
All rules pertaining to arc light wires and stations shall apply (so far as practicable) to street railway stations and their conductors.
Railway Systems with Ground Return.
Electric railway systems in which the motor cars are driven by a current from a single wire, with ground or floor return circuit, are prohibited except as hereinafter provided:
1. When there is no liability of other conductors coming in contact with the trolley wire.
2. When the location of the generator is such that the ground circuit will not create a fire hazard to the property.
3. When an approved automatic circuit breaker or other device that will immediately cut off the current in case the trolley wires become grounded is introduced in each circuit as it leaves the power station. This device must be mounted on a fireproof base, and be in full view of the attendant.
Trolley Wires—Must be:
1. No smaller than No. OB. & S. copper, or No. 4 B. & S. silicon bronze, and must readily stand the strain put upon them when in use,
2. Well insulated from their supports, and in case of the side or double pole construction, the supports shall also be insulated from the poles immediately outside the trolley wire.
3. Capable of being disconnected at the power house, 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 in extinguishing the flames. This rule also applies to feeders.
4. Safely protected against contact with all other conductors.
All wires in cars must be run out of reach of the passengers, and shall be insulated with a waterproof insulation.
Lighting and Railway Power Wires.
Lighting and power wires must not be permitted in the same circuit with trolley wires with a ground return, except in street railway cars, car houses, and power stations. The same dynamo may be used for both purposes, provided the connection from the dynamo for each circuit shall be a double-pole switch so arranged that only one of the circuits can be in use at the same time.
When current for light and power is taken from primary or secondary batteries, the