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Class B. HIGH POTENTIAL SYSTEMS. OVER 300 VOLTS. Any circuit attached to any machine, or combination of machines, which develop over 300 volts difference of potential between any two wires, shall be considered as a high potential circuit and coining under that class, unless an approved transforming device is used, which cuts the difference of potential down to less than 300 volts.

10. Outside Conductors. All outside overhead conductors (including services):—

a. Must be covered with some approved insulating material, not easily abraded, firmly secured to properly insulated and substantially built supports, all tie wires having an insulation equal to that of the conductors they confine. (See Definitions).

b. Must be so placed that moisture cannot form a cross connection between them, not less than a foot apart, and not in contact with any substance other than their insulating supports.

c. Must be at least seven feet above the highest point of flat roofs, and at least one foot above the ridge of pitched roofs over which they pass or to which they are attached.

d. Must be protected by dead insulated guard irons or wires from possibility of contact with other conducting wires or substances to which current may leak. Special precautions of this kind must be taken where sharp angles occur, or where any wires might possibly come in contact with electric light or power wires.

e. Must be provided vwith petticoat insulators of glass or porcelain. Porcelain knobs or cleats and rubber hooks will not be approved.

/. Must be so spliced or joined as to be both mechanically and electrically secure without solder. The joints must then be soldered, to insure preservation, and covered with an insulation equal to that on the conductors. (See Definitions).

g. Telegraph, telephone, and similar wires must not be placed on the same cross-arm with electric light or power wires.

11. Service Blocks:

Must be covered over their entire surface with at least two coats of waterproof paint.

Interior Conductors.

12. All Interior Conductors:

a. Must be covered where they enter buildings from outside terminal insulators to and through the walls, with extra waterproof insulation, and must have drip loops outside. The hole through which the conductor passes must be bushed with waterproof and non-combustible insulating tube, slanting upward toward the inside. The tube must be sealed with tape, thoroughly painted, and securing the tube to the wire.

b. Must be arranged to enter and leave the building through a double contact service switch, which will effectually close the main circuit and disconnect the interior wires when it is turned "off." The switch must be so constructed that it shall be automatic in its action, not stopping between points when started, and prevent an arc between the points under all circumstances; it must indicate on inspection whether the current be "on " or " off," and be mounted in a noncombustible case, and kept free from moisture, and easy of access to police or firemen. So-called " snap switches " shall not be used on high potential circuits.

c. Must be always in plain sight, and never encased, except when required by the Inspector.

d. Must be covered in all cases with an approved non-combustible material that will adhere to the wire, not fray by friction, and bear a temperature of 150° F. without softening. (See Definitions).

e. Must be supported on glass or porcelain insulators, and kept rigidly at least eight inches from each other, except within the structure of lamps or on hanger boards, cut-out boxes, or the like, where less distance is necessary.

f. Must be separated from contact with walls, floors, timbers, or partitions through which they may pass by noncombustible insulating tube.

g. Must be so spliced or joined as to be both mechanically and electrically secure without solder. They must then be soldered, to insure preservation, and covered with an insulation equal to that on the conductors.

LAMPS AND OTHER DEVICES.

13. Arc Lamps—In every case:—

a. Must be carefully isolated from inflammable material.

b. Must be provided at all times with a glass globe surrounding the arc, securely fastened upon a closed base. No broken or cracked globes to be used.

c. Must be provided with an approved hand switch, also an automatic switch, that will shunt the current around the carbons should they fail to feed properly. (See Definitions).

d. Must be provided with reliable stops to prevent carbons from falling out in case the clamps become loose.

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