§ 39.304. Grounding of arresters for signaling systems.
(a) Exemptions. The ground connections for outside installations of cable protectors employed solely to prevent electrical injury to the cable need not conform to the requirements of this section. For the provisions governing the grounding of the metal cases of outdoor apparatus as covered by this section, reference should be made to § § 39.61—39.70 (relating to methods of protective grounding).
(b) Arresters. Arresters shall be permanently and effectively grounded in the following manner:
(1) Ground conductor. The ground conductor shall preferably be of copper or other material which does not corrode under the conditions of use, and shall be not less than No. 18 in size and in urban districts or within buildings shall be covered with a suitable insulation. If necessary to guard the ground conductor from mechanical injury on poles or if a ground conductor on the outside of building walls is near a roadway, sidewalk or pathway thus necessarily exposing it to tampering by unauthorized persons, it shall be protected for a distance of eight feet from the ground by a wooden molding or by conduit of nonmagnetic material.
(2) Ground connection. The ground connection shall be made to a cold water pipe, if available, connected to the street mains and in service. An outlet pipe from a water tank fed by a street main may be used if such outlet pipe is adequately bonded around the tank to the inlet pipe connected to the street main. If a cold water pipe is not available, the ground connection may be made to a gas pipe, if the ground conductor is attached to the pipe between the meter and the street mains. If cold water or gas pipes are not available, the ground connection may be made to an iron rod or pipe driven into permanently damp earth, or to a plate or other body of metal buried in permanently damp earth. Reference should also be made to § 39.65 (relating to ground conductor). Steam or hot water pipes should not be used for ground connections. Driven rods or pipes, used as ground connections for protectors, shall not also be used as ground connections for electrical supply circuits or electrical apparatus, and where water or gas pipes are used for a ground connection, attachment to such pipes shall be made at a different point than for attachments to electrical supply circuits or equipment.
(c) Connecting ground conductor to pipes. Ground conductors shall be attached to pipes by means of suitable ground clamps. The entire surface of the pipe to be covered by the clamp shall be thoroughly cleaned.
(d) Connecting ground conductor to driven rod or pipe. The ground conductor shall be attached to the rod or pipe so as to give reliable connection both mechanically and electrically and in such a manner as to prevent corrosion when the joint is buried in the earth.
(e) Connecting ground conductor to buried electrode. If a buried plate or other metal electrode is employed, the ground conductor shall be securely fastened to it in such manner as to make a reliable electrical and mechanical contact.
Cross References This section cited in 34 Pa. Code § 39.192 (relating to scope).
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