h. Must not have cars left with trolley in electrical connection with the trolley wire. Where ground return is used it must be so arranged that no difference of potential will exist greater than 5 volts to 50 feet, or 50 volts to the mile between any two points in the earth or pipes therein. CLASS F, ELECTRIC HEATERS. 44. ELECTRIC HEATERS: a. If stationary, must be placed in a safe situation, isolated from inflammable materials and treated as stoves b. Must have double-pole indicating switches and doublepole cut-outs arranged as required for electric light or power of same potential and current. c. Must have the attachments of feed wires to the heaters in plain sight, easily accessible, and protected from interference, accidental or otherwise. d. The flexible conductors for portable 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 that mechanical strain will not be borne by the electrical connections. CLASS G, STORAGE OR PRIMARY BATTERIES. 45. 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. All secondary batteries must be mounted on approved insulators. Insulators for mounting secondary batteries, to be approved, must be noncombustible, such as glass, or thoroughly vitrified and glazed porcelain. c. Special attention is directed to the rules for rooms where acid fumes exist. d. The use of any metal liable to corrosion must be avoided in connections of secondary batteries. 46. MISCELLANEOUS:— MISCELLANEOUS. a. The wiring in any building must test free from grounds: i. e., each main supply line and every branch circuit should have an insulation resistance of at least 100,000 ohms, and the whole installation should have an insulation resistance between con ductors and between all conductors and the ground (not including attachments, sockets, receptacles, etc.) of not less than the following: 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. b. Ground wires for lightning arresters of all classes, and ground detectors must not be attached to gas pipes within the building. c. Where telephone, telegraph or other wires connected with outside circuits are bunched together within any building, or where inside wires are laid in conduit or duct 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. d. 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 buildings 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 an abnormal current flow. Any conductor normally forming an innocuous circuit may become a source of fire hazard if crossed with another conductor, through which it may become 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 require ments: I. 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 inclosed 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, and the holes through the outer walls to be protected by bushing the same as required for electric light and ower-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. This ground wire shall be kept at least three (3) inches from all conductors, and shall never be secured by uninsulated double-pointed tacks. 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. e. The metallic sheathes to cables must be permanently and effectively connected to earth." f. The following formula for soldering fluid is suggested : The following is a list of wires which have been tested and found to comply with the standard for approved wires, required for all high-potential work (300 volts or over); and for service wires, all classes of concealed wiring and wiring exposed to dampness in low potential work : Manufacturer. American Electrical Works. . Ind. Rubber & Gutta Percha Ins. Co. Okonite Co. . Nat. India Rubber Co. Paracore N. I. R.. U. S.... Columbia Nat. India Rubber Co. Gen. Electric Co. ...C S. Knowles. NOTE. The results of recent tests on these and other wires can be seen at inspection offices. MATERIALS. The following are given as a list of NON-COMBUstible, nonABSORPTIVE, 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. .. |