§ 39.66. Nature of ground connection.
(a) Permanence. The ground connections shall be permanent and effective and made as indicated in subsection (b), if possible, or else as prescribed in subsection (c), (d) or (e). Reference should also be made to § 39.69 (relating to ground resistance).
(b) Piping system. For circuits, equipment, and arresters at supply stations, connections shall be made to all available active continuous metallic underground water piping systems between which no appreciable difference of potential normally exists, and to one such system if appreciable differences of potential do exist between them. At other places connections shall be made to at least one such system, if available. Gas piping shall not be used. References should be made to § § 39.65 and 39.68 (relating to ground conductor; methods of ground connection). The term ‘‘available,’’ as used in this rule, shall mean ordinarily within 500 feet for stations. The protective grounding of electrical circuits and equipment to water pipe systems in accordance with this Subchapter shall always be permitted, since such grounding offers the most efficient protection to life and property and is not injurious to the piping systems.
(c) Alternate methods. If underground metallic piping systems are not available, other methods which will secure the desired permanence and conductance may be permitted. Where available, metal well casings, local metal drain pipes, and similar buried metal structures of considerable extent may be used in lieu of extended buried water-piping systems. Ground connection may be made to the steel frame of a building containing the grounded circuits or equipment, to which frames of machines and other noncurrent-carrying surfaces should also then be connected. In such cases the building frame shall be itself well grounded by effective connection to the ground which may require artificial grounding for steel frame buildings supported on masonry or unreinforced concrete footings.
(d) Artificial grounds. If resort to artificial grounds is necessary, their number shall be determined by the following requirements:
(1) No more than one artificial ground is required for lightning arresters, except for large current capacity. At least two grounds are required for low voltage alternating current distribution circuits at transformers or elsewhere.
(2) If no part of the circuit or equipment protected may be reached by persons while they are standing on the ground or damp floors, or by persons while touching any metallic piping to which the ground wire is not effectively connected, a single artificial ground may be used even if its resistance exceeds that specified in § 39.69. In such cases guards should be provided for the ground conductor in accordance with § 39.65(c) wherever it is otherwise accessible, or to provide insulating mats or platforms so located that persons cannot readily touch the ground conductor without standing on such mats or platforms.
(e) Grounds to railway returns. Protective ground connections shall not be made to railway negative return circuits when other effective means of grounding are available, except ground connections from electric railway lightning arresters. When ground connections are necessarily made to the grounded track return of electric railways, they shall be made in such a manner as not to afford a metallic connection between the railway return and other grounded conducting bodies. This provision shall not prohibit the making of drainage connections which are not protective grounds between piping systems and railway negative return circuits for the prevention of electrolysis. Multiple protective ground connections from other circuits to railway returns shall be avoided, and if multiple artificial grounds are made on such other circuits near such railway returns, they shall be so arranged as to prevent the flow of any considerable current in and between such connections, thus reducing their effectiveness, or causing other damage.
Cross References This section cited in 34 Pa. Code § 39.61 (relating to applicability); 34 Pa. Code § 39.62 (relating to scope); 34 Pa. Code § 39.63 (relating to modification or waiver of provisions); 34 Pa. Code § 39.67 (relating to attachment of ground conductor); 34 Pa. Code § 39.68 (relating to methods of ground connection); 34 Pa. Code § 39.69 (relating to ground resistance); 34 Pa. Code § 39.103 (relating to protective grounding); 34 Pa. Code § 39.183 (relating to ground wires); 34 Pa. Code § 39.197 (relating to grounding); 34 Pa. Code § 39.219 (relating to grounding or isolating service conduits); 34 Pa. Code § 39.292 (relating to grounding noncurrent-carrying parts); and 34 Pa. Code § 39.304 (relating to grounding of arresters for signaling systems).
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