- 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]).
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.