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same general regulations must be observed as apply to such wires fed from dynamo generators developing the same difference of potential.
1. The wiring in any building must test free from "grounds" before the current is turned on. This test may be made with a magneto bell that will ring through a resistance of 20,000 ohms, where currents of less than 250 volts are used.
2. No ground wires for lighting arresters may be attached to gas pipes within the building.
3. All conductors connecting with telephone, district messenger, burglar alarm, watch clock, electric time, and other similar instruments must, if in any portion of their length they are liable to become crossed with circuits carrying currents for light or power, be provided near the point of entrance to the building with some 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.
RULES OF THE NATIONAL BOARD OF FIRE UNDERWRITERS.
At the 24th Annual Meeting of the Board, held June 8th, 1890, the New York Board rules regulating Electric Light Installations were adopted for promulgation to members.
Amended Standard for Electric Equipments, Adopted January 15, 1890, by the New York Board of Fire Underwriters.
Capacity of Wires.
1. The conducting wires must be of copper, and must have a weight per running foot at least equal to that of the wire (or parallel group of wires) constituting the main circuit of the magnetic regulator of the electric lamps (arc lamps), or of the armature of the machine employed, whichever of these is greatest.
Joints or Splices.
2. All joints in wires must be so made as to secure perfect and durable contacts, which shall always maintain a degree of cc nductivi Ly at the joint at least equal to that of the wire generally.
3. The joint must be so made as in the ordinary "telegraph splice" that it is mechanically secure against motion or displacement, and must then be further electrically connected by solder so applied as to leave no corrosive or otherwise injurious substance on the connection. After joining and soldering, the joint must be covered with insulating material in such a way as to make the insulation of the joint as good as that of the rest of the line.
4. A joint made by the process of electric welding would be the equivalent of one made as indicated above, but no joint depending upon solder for its mechanical integrity either wholly or in part will be allowed.
Wires Exterior to Buildings.
5. Outside wires must be covered with at least two coatings, one of insulating material, impervious to water, next to the wire, and the other of some substance fitted to resist abrasion or like mechanical injury, and must be firmly secured to substantial approved insulators, adequately supported. All "tye wires," or those used to secure the conductors to the "insulators," must be themselves covered with waterproof insulating and mechanically resist ant material similar to that used on the conductors themselves.
0. Overhead conducting wires must be supported on poles as far as possible, so that they can be easily reached for inspection, and when this cannot be done, and special permit is granted allowing them to be carried over or attached to buildings, they must be supported at least seven feet above the general level of the roof and at least one foot above the ridge of "pitched roofs."
7. Where wires approach buildings to enter them they should be so located as not to be readily reached by the occupants of such buildings, and in the case of arc light systems must maintain a minimum distance of ten inches, and for incandescent systems of six inches, except where the wires are carried in conduits.
8. When these exterior electric light wires are near other conductors of any kind capable of carrying off a part of the current, if contact should be made, dead-insulated guard irons must be placed so as to prevent any such contact in case of accidents affecting the wires or their supports.
9. Like precautions must be taken where acute angles occur in the line wires.
10. Overhead wires from the main circuit or pole lines in the street to the insulators attached to the buildings which they enter, must not be less than ten inches apart for arc wires, or six inches for incandescent wires carrying currents of 250 E. M. F. as a maximum. They must be securely and rigidly supported on "insulators" of glass, porcelain, or other approved material.
Wires Entering Buildings.
11. Wherever electric light wires enter buildings through their exterior wails the wires must be firmly supported and incased in tubes of non-conducting material not liable to absorb moisture (e.g., porcelain or glass) and so placed as to prevent the entiance of rain water along the wires (e. g., the tubes must slope upward as they pass inivard through the wall).
12. Both the ingoing and return wires should enter the building at the same location and pass through an approved manual "cutout-box" or switch, which must be placed where it will be easy of access to firemen and the police.
High Potential Wires Within Buildings.
13. In the interior of buildings, wires for arc lights, besides being covered with an insulating covering such as has been already described, must be in all cases securely attached and supported by insulators which shall keep them out of contact with any wall, partition, ceiling, or floor, so as to secure an air space of at least one-quarter inch between the wire and any adjacent wall, partition, ceiling, or floor, and wherever the wires cross or come near to any other wires, pipes, or