.... ... wrote:

Tom you mentioned grounding electrode system and a 4 wire feed. Could
you clearify that a bit?
Did you mean that you should bring the ground with the feeders to each
building ?
When you said grounding electrode I hope you didn't mean ground rods
for each building ? There should only be a grouding electrode at the
main panel then a 4 wire feed to the sub panel with the ground and
neutral terminating on thier own busses (neutral bus being isolated from
ground)
Do you agree or amI missing something?
Bill

I'm afraid your missing something.

I'm not suggesting that he should use a grounding electrode system as a
substitute for an Equipment Grounding Conductor. I'm not even
suggesting a three wire feeder with the neutral bonded to ground at each
building disconnecting means, though in the absence of other metallic
pathways between the buildings that is a permissible practice. What I
am suggesting is the use of a four wire feeder that includes an
Equipment Grounding (bonding) Conductor (EGC) with that EGC bonded to a
Grounding Electrode System at each building disconnecting means. You
are correct in pointing out that the best practice is to maintain the
Grounded Current Carrying Conductor aloof from Ground at any place other
than the service disconnecting means. Be aware, however that the US NEC
specifically permits you to wire each separate building as if it were a
separate service providing there are no other metallic pathways between
the buildings.

The US NEC requires a Grounding Electrode System at each building unless
that building is served only by a single branch circuit. So in the OPs
case his building A would not need a Grounding Electrode System as he
only needs one branch circuit in there. Trouble is he plans to run the
feeder there first. If he can run the feeder to the building that he is
calling building B then he can run the single branch circuit that he
needs in building A from either the house or building B and he would not
be required to build a grounding electrode system at building A. If he
does run the feeder to building A then he will not need a Grounding
Electrode System there because it will be served only by a single branch
circuit. The applicable section of the US NEC is copied below.

250.32 Two or More Buildings or Structures Supplied from a Common Service.
(A) Grounding Electrode. Where two or more buildings or structures are
supplied from a common ac service by a feeder(s) or branch circuit(s),
the grounding electrode(s) required in Part III of this article at each
building or structure shall be connected in the manner specified in
250.32(B) or (C). Where there are no existing grounding electrodes, the
grounding electrode(s) required in Part III of this article shall be
installed.
Exception: A grounding electrode at separate buildings or structures
shall not be required where only one branch circuit supplies the
building or structure and the branch circuit includes an equipment
grounding conductor for grounding the conductive non–current-carrying
parts of all equipment. (copyright 2002 the National Fire Protection
Association)

It is worth noticing that this section stands alone and is not modified
by other sections. Any building that contains over current protective
devices has to have a grounding electrode system.

I hope that clears up any confusion.
--
Tom H