§ 39.197. Grounding.
(a) Grounding method. Lighting arrester grounding and all grounding of circuits, equipment, or wire runways, which are intended to be a permanent and effective protective measure shall be made in accordance with the methods specified in § § 39.61—39.70 (relating to methods of protective grounding).
(b) Circuits required to be grounded. Circuits installed in rooms to which other than properly qualified electrical workmen have access, or in rooms where nonelectrical processes are liable to distract the attention of the electrical operator from the purely electrical operations, shall be permanently grounded in accordance with § § 39.61—39.70 except that the following circuits are not required to be grounded:
(1) Circuits on two-wire, direct-current systems.
(2) Circuits entirely unexposed to leakage or induction from higher voltage circuits, either through overhead construction or through transformers or other devices. It is recommended, however, that all three-wire, not delta three-phase, circuits, even if unexposed, have their neutrals grounded; and that multiphase circuits, even if unexposed where partly used for lighting, be so arranged and grounded that the lighting circuits have the lowest practical voltage ground.
(3) Circuits over 150 volts to ground. Reference should be made to § 39.199 (relating to guarding or isolating live parts).
(4) Electric furnace and welding circuits. Reference should be made to § 39.263 (relating to guarding live parts).
(c) Grounding noncurrent-carrying metal parts. Under the hazardous conditions given in this subsection, fixed electrical utilization equipment shall, if practicable, have the exposed noncurrent-carrying metal parts, such as frames of motors, cranes, cars, and switchboards, cases of transformers and oil switches, and casings of wiring and conductors permanently grounded. Reference should be made to § § 39.61—39.70 and 39.281—39.285. The following conditions shall be considered hazardous:
(1) Operations at voltages over 150 to ground, wherever equipment is located.
(2) Locations where explosives, inflammable gas or inflammable flyings normally exist in dangerous quantities.
(3) Cases where exposed grounded surfaces, such as metal frames of other machines, plumbing fixtures, and conducting floors or walls, exist within the reach of persons when touching the metal parts under consideration. Grounded surfaces within 5 feet horizontally of the parts considered and within 8 feet vertically of the floor shall be considered within reach.
(d) Exceptions. Except as set out in subsection (c)(2) and (3) no ground connection need be made to expose metal frames of switchboards, motors, or lighting fixtures connected to direct current trolley or third rail circuit, if such frames are effectively insulated from ground, and if the metal frames in question are so located with reference to insulating floors or platforms that persons may not readily touch the metal frames in question without standing on such floors or platforms.
(e) Parts of machines, such as name plates, screws in wood, and similar small parts which are not liable to become alive, except under very unusual circumstances, are not considered as coming under the rule and may be left ungrounded.
Cross References This section cited in 34 Pa. Code § 39.191 (relating to applicability); 34 Pa. Code § 39.192 (relating to scope); 34 Pa. Code § 39.193 (relating to modification or waiver of provisions); 34 Pa. Code § 39.201 (relating to storage batteries, transformers, and lightning arresters); 34 Pa. Code § 39.219 (relating to grounding or isolating service conduits); 34 Pa. Code § 39.237 (relating to grounding noncurrent-carrying metal parts); 34 Pa. Code § 39.245 (relating to grounding frames); 34 Pa. Code § 39.253 (relating to deteriorating agencies); 34 Pa. Code § 39.254 (relating to guards for live parts); and 34 Pa. Code § 39.271 (relating to grounding).
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