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Q.Is it possible to properly bond an electrical subpanel without running four-wire SER cable to it from the service-entrance panel? Some electricians have told me that under certain circumstances the subpanel can have its own ground wire and rod, while others have said it has to be bonded through the entrance panel. Who's right?

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][2]).

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 having an additional ground wire and ground rod.