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Legal Disclaimer |
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SECTION 4 - BONDING Bonding is the connection to ground of all the nonelectrical conductive materials that enclose or are adjacent to the energized conductors. The electrical code requires that all equipment MUST be properly grounded and bonded, except in very rare special cases. The complete bonding circuit of any system must include the metal enclosures, frames and/or support structures of the following: service entrance equipment, transformers, switchboards, panels, switches, motor controllers, motors, generators, lighting equipment, outlet boxes, junction boxes and cabinets. These devices are then all interconnected by means of metal raceways, cable trays, metal enclosures of bus ducts, bare copper ground wires, and the green insulated conductor in non-metallic sheath cables. The equipment grounding circuit path must be permanent and continuous. The primary purpose of equipment bonding and grounding is safety. Accident statistics show that many fatalities have been caused by electric shock that resulted from persons making contact with metallic enclosures that normally should have been at ground potential but, due to faulty grounding, were not. In the event of an insulation failure at the load, fault current follows the bonding conductor to ground and causes an overcurrent device (fuse, breaker) in the current to open. Until the overcurrent device opens, there will be a momentary voltage to ground on the enclosure. With proper bonding this is low enough and brief enough not to be lethal. The bonding and grounding conductors must be copper per code Section 10-614. |
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