NATIONAL BOARD FIRE UNDERWRITERS.

f. Must have ample carrying capacity, to prevent heating. (See Capacity of Wires Table.)

4. SWITCHBOARDS:

a. Must be so placed as to reduce to a minimum the danger of communicating fire to adjacent combustible material.

b. Must be accessible from all sides when the connections are on the back; or may be placed against a brick or stone wall when the wiring is entirely on the face.

C.

Must be kept free from moisture.

d. Must be made of non-combustible material, or of hard wood in skeleton form, filled to prevent absorption of moisture. e. Bus bars must be equipped in accordance with Rule 3 for placing conductors.

5. RESISTANCE BOXES AND EQUALIZERS:

a. Must be equipped with metal, or other non-combustible frames. (See Definitions.)

b. Must be placed on the switchboard, or, if not thereon, at a distance of a foot from combustible material, or separated therefrom by a non-inflammable, non-absorptive, insulating

material.

6. LIGHTNING ARRESTERS:

a. Must be attached to each side of every overhead circuit connected with the station.

b. Must be mounted on non-combustible bases in plain sight on the switchboard, or in any equally accessible place, away from combustible material.

WIRING RULES AND REQUIREMENTS.

C. Must be connected with at least two "earths" by separate wires, not smaller than No. 6 B. & S., which must not be connected to any pipe within the building, and must be run as nearly as possible in a straight line from the arresters to the earth connection.

d. Must be so constructed as not to maintain an arc after the discharge has passed.

7. TESTING:

a. All series and alternating circuits must be tested every two hours while in operation, to discover any leakage to earth, abnormal in view of the potential and method of operation.

b. All multiple arc low potential systems (300 volts or less) must be provided with an indicating or detecting device, readily attachable, to afford easy means of testing where the station operates continuously.

c. Data obtained from all tests must be preserved for examination by insurance inspectors.

These rules on testing to be applied at such places as may be designated by the association having jurisdiction.

8. MOTORS:

a. Must be wired under the same precautions as with a current of the same volume and potential for lighting. The motor and resistance box must be protected by a double pole cut-out and controlled by a double-pole switch, except in cases where one-quarter horse-power or less is used on low tension circuit, a single pole switch will be accepted.

NATIONAL BOARD FIRE UNDERWRITERS.

b. Must be thoroughly insulated, mounted on filled dry wood, be raised at least eight inches above the surrounding floor, be provided with pans to prevent oil from soaking into the floor, and must be kept clean.

C. Must be covered with a waterproof cover when not in use, and, if deemed necessary by the Inspector, be inclosed in an approved case. (See Definitions.)

9. RESISTANCE BOXES:

a. Must be equipped with metal or other non-combustible frames. (See Definitions.)

b. Must be placed on the switchboard, or at a distance of a foot from combustible material, or separated therefrom by a non-inflammable, non-absorptive, insulating material.

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 coming under that class, unless an approved transforming device is used, which cuts the difference of potential down to less than 300 volts.

IO.

OUTSIDE CONDUCTORS—ALL OUTSIDE, OVERHEAD CON-
DUCTORS (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.)

WIRING RULES AND REQUIREMENTS:

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 with petticoat insulators of glass or porcelain. Porcelain knobs or cleats and rubber hooks will not be approved.

f. 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.

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

a. Must be covered where they enter buildings from outside terminal insulators to and through the walls, with