ECN Forum Forums General Topics of the Trade General Discussion Area Bonding Service Equipment Raceways

Someone Please help clarify whether all metal raceways at the service equipment/panel have to be bonded to the grounded conductor or if it is only the raceways containing the service conductors. Double locknut bonding is not acceptable for the service raceways but is it acceptable for the branch raceways at the service equipment? Hard to interpret the code on this mattter. Thanks for any help.

You bond service raceways to the "grounding" conductor. This is a different application than feeder and branch circuit raceways. That is why we have extra bonding requirements. Service conductors basically are not protected against overcurrent. The same fault that would trip a breaker on a feeder will just sit there and cook on a service conductor until the primary fuse on the transformer opens or the transformer blosw.

I accept your reasoning but the NEC states that the service raceways be bonded to the "grounded conductor" or through other acceptable means per 250.92. --standard locknuts not being allowed as sole means for the bonding requirement, but my question is also in reference to 250.130(A) where {all}the equipment grounding conductor at service equipment(branch metal raceway) is required to be bonded to the grounded service conductor and the GEC (acceptable bonding means per 250.96 superceded by 250.92(b)). I have to conclude that standard locknuts are not allowed as sole means for bonding at the service equipment for any metal raceways.