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Grounding versus Bonding



250.100 Bonding—Hazardous (Classified) Locations.

Because of the explosive conditions associated with electrical installations in hazardous (classified) locations, electrical continuity of the effective ground-fault current path (metal parts of equipment and raceways) must be ensured by one of the methods specified in 250.92(B)(2) through (4): Figure 250–142

Author’s Comments:
• The methods of bonding metal raceways that extend into a hazardous (classified) location include:
• Threaded couplings or threaded entries on enclosures [250.92(B)(2)].
• Threadless raceway couplings and connectors where permitted in Articles 501, 502, and 503 [250.92(B)(3)].
• Bonding the raceway with a listed bonding wedge or bushing [250.92(B)(4)].
• Bonding the raceway with a bonding-type locknut if the metal raceway terminates to an enclosure without a ringed knockout [250.92(B)(4)].
• Hazardous (classified) location bonding requirements apply to all intervening raceways, fittings, boxes, and enclosures between the hazardous (classified) location and the point of grounding and bonding at service equipment and separately derived systems. See 501.100 for Class I locations, 502.100 for Class II locations, and 503.100 for Class III locations for specific requirements. Figure 250–143

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