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50. Where electric gas-lighting is to be used on the same fixture with electric light,
(a) no part of the gas piping or fixture shall be in connection with the gas-lighting circuit;
(b) the wire used for the fixture must have a non-inflammable insulation, or (c) if concealed between the pipe and shell of the fixture must have an insulation such as is required for fixture wiring for the electric light; (d) the whole installation must test free of grounds, and (e) the two installations must test perfectly free of connection with each other. (/) Any such installation will then be subject to special approval by the inspector.
Arc Lights on Low Potential Circuits.
51. This system of lighting will in general be governed by the foregoing rules for low potential work, but (a) no wire smaller than No. 12 B. & S. must be used; (b) there must be a double pole cut-out at the junction of the branch with the main, and (c) a double pole switch in the branch, (d) The cut-out, switch, and resistance device must be composed of non-inflammable material, (e) The light must be protected by a globe, etc., the same as is required for a high potential lamp.
52. In isolated plants, (a) the dynamo,, regulating devices, switchboards, and all wires connecting the same, must be installed in conformity with the requirements for a standard central station (see 53 to 67) and (b) should never be placed in any room where they will be exposed to flyings of any combustible materials.
53. (a) Insulated on thoroughly dry wood,
(b) "filled" to prevent absorption of moisture.
(c) A waterproof cover should be provided, and kept over each dynamo when not running.
54. (a) Wires from dynamos to switchboard, and (b) thence to outside lines ("bus wires, feeders, primary mains, arc circuit leads and returns), (c) to be wholly exposed to view, (d) supported by glass or porcelain insulators, and (e) of sufficient sectional area to prevent heating. (/) Where passing through floors, partitions, or other wood-work, (g) to be protected by substantial tubes of glass or porcelain, (h) which shall project above and below floors, and beyond the surface of partitions, so as to insure perfect insulation, (i) Hard rubber tubing may be used except where passing through the floors at or near the dynamo.
55. (a) Where leaving the building, the wires to be looped downward, and (b) the tubes in which they are inclosed to be inclined so as to prevent the entrance of rain water along the wires.
56. (a) Wires of opposite polarity should be separated at least twelve inches, (ft) particularly where passing through floors and partitions.— (c) Conductors from ceiling or floor to switchboard may be run at a less distance than twelve inches from each other, (d) but in that case an approved insulation must be provided.
57. If (a) conductors from dynamos are run under floors—(b) except the space underneath be a perfectly dry, finished room, and (c) not less than six feet between floors—(d), they must be specially insulated, and will then be subject to approval.
58. (a) Each feeder and primary main to be provided with a safety fuse on a non-combustible base, (b) All wire connections must be soldered, if necessary, to secure good contact.
59. Branch wires for station lighting to be in accordance with the requirements of this Exchange for electric light wiring.
60. (a) To be kept free from moisture, (b) located apart from woodwork, (c) accessible from all sides, (d) not inclosed, and (e) with all electrical devices, wires and connections in plain sight.— (/) When all wires and electrical devices are on the front vhe switchboard may be set against a brick wall, (g) but must be detached from any woodwork.— (h) The switchboard should be constructed either of slate or some other non-combustible insulating substance, or (i) so-called "Skeleton."
61. (a) All switches and wires on the switchboard must have ample capacity and (b) contact to carry their possible maximum load without heating.
62. (a) To be located in sight of attendants, and (b) so placed and constructed that an arc if formed will not come in contact with woodwork or other combustible material, (c) Lightning arresters should be so designed as to automatically destroy any arc which may be formed by a lightning discharge or otherwise.
63. (a) Frames to be constructed of noncornbustible material, (b) To be open and accessible from all sides, (c) supported at least twelve inches from all woodwork, (d) and located so as to be in sight of dynamo attendants.
64. (a) All resistance devices to be so designed as to heat but slightly when in use, and (b) connected so as not to be liable from a short circuit or other cause to an overcharge of current; (c) otherwise they must be inclosed in non-combustible cases and (d) kept away from any woodwork.
Care and Attendance.
65. A competent man must be kept constantly in the dynamo room while the dynamos are running.
66. (a) Oil must not be allowed to accumulate on the floor, and (b) all oily waste must be kept in standard metal waste-cans, or (c) removed from the station daily after the dynamos are stopped and cleaned.
67. Arc lamps must always be provided with perfect globes.
68. Motors must (a) be placed as near as possible to the point where wires enter the building, (b) be mounted on filled dry wood, (c) be raised at least eight inches above the surrounding floor, (d) be kept clean, and (e) covered with a waterproof cover when not in use, and (/) if deemed necessary by the inspector, be inclosed in an approved case.
69. Standard metal waste-cans, with a selfclosing cover and legs raising the can at least three inches from the floor, must be provided for oily waste.
Switches, Regulators, and Cut-Outs.
70. (a) The controlling switches must be so constructed as to entirely disconnect the motor from the circuit, and (ft) a cut-out such as is required for a similar lighting circuit must be placed as near as possible to the point where the wires enter the building.