Pennsylvania Code
Title 34 - LABOR AND INDUSTRY
Part I - Department of Labor and Industry
Chapter 39 - SAFETY STANDARDS-GENERAL
Subchapter B - ELECTRIC SAFETY
CONDUCTORS
Section 39.219 - Grounding or isolating service conduits

(a) Metal conduit or sheathing encasing service conductors from either overhead or underground lines shall either be permanently grounded as required by § 39.197 (relating to grounding) or effectively isolated by elevation. Reference should also be made to §§ 39.197 and 39.199 (relating to grounding; and guarding or isolating live parts).

(b) If not grounded, the service conduit or sheathing shall be effectively insulated from metal work of the building, and from its piping. If service conduit or sheathing is electrically continuous with interior conduit or sheathing, the grounding required for conduit in § 39.197(c) shall be made direct to the service conduit or sheathing and shall have conductance not less than that of No. 6 copper wire.

(c) If grounded service conduit or sheathing is insulated from interior conduit or sheathing, its ground wire conductance need not exceed that required under §§ 39.61-39.70. It is frequently advisable to insulate interior conduit or sheathing from underground service conduit or sheathing, to prevent burnouts of small interior conduit, armored cable sheaths or metal molding, by large currents which might flow from grounded circuits through the interior metal to water pipes or other good ground connections within the building.