PART V. BONDING
250.92 Service Bonding Continued
(2) Threaded Fittings or Entries. Raceways containing service conductors are considered bonded to an effective ground-fault current path by threaded couplings or threaded entries on enclosures where made up wrenchtight. Figure 250129
(3) Threadless Fitting. Raceways containing service conductors are considered bonded to an effective ground-fault current path by threadless raceway couplings and connectors where made up tight. Figure 250130
(4) Bonding Fitting. When a metal service raceway terminates to an enclosure with a ringed knockout, a listed bonding device, such as a bonding wedge or bushing, must bond one end of the service raceway with a bonding jumper sized in accordance with Table 250.66 [250.92(B)(4) and 250.102(C)]. Figure 250131
When a metal raceway containing service conductors terminates to an enclosure without a ringed knockout, a bonding-type locknut can be used instead of a bonding wedge or bushing. Figure 250132
A bonding-type locknut differs from a standard-type locknut in that it has a bonding screw with a sharp point that drives into the metal enclosure to ensure a solid termination.
Bonding one end of a service raceway in accordance with 250.92(B) provides the low-impedance fault-current path to the utility electrical supply source. Figure 250133
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