A. George Flach, former chief electrical inspector for New Orleans, responds: At one time, the National Electrical Code allowed the circuit-grounded conductor (which could be a neutral conductor) to be regrounded at a subpanel via a grounding electrode bonded to the subpanel. Then the code was revised to allow this kind of regrounding only when a feeder was run to a separate structure and there was no interconnected metal — metal pipes, reinforcing rods in interconnected concrete walkways, metal roof components, and so on — between the two buildings (NEC 2005, 250.32[B]).
In the 2008 edition of the NEC, however, this grounding method is not permitted, except in existing installations. In all other cases, subpanels must be bonded to the service-entrance panel, either with metal raceways or with metal jacketed cables and properly installed fittings. But there's nothing in the new code that prohibits a subpanel from...
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