the_tool_man wrote:
Hi all:

Six years ago, I built my workshop about 150ft from the house with a
100A service. I ran a four-conductor cable to the subpanel in the
shop, and kept the ground and neutral conductors isolated from each
other. I did not bond the sub-panel ground to its own ground rod,
thinking it might cause a ground loop and/or noise in the intercom
circuit bewteen the buildings. More recently, when I put in a spa with
it's own GFCI breaker, I had several people advise me to drive a
separate ground rod for it, and that I should have done the same for my
workshop. So far, I have had no issues, but I want to make sure I did
the right thing.

My searches here have yielded many debates on the need to keep the
ground and neutral bonded only in the main panel and not the subs
(which is how I did it), but nothing about the ground rod question.
Does a remote subpanel need its own ground rod or not?
Thanks in advance,
John.


John
The debates on this topic are endless and I won't try to settle them.
I will say that the US NEC requires that every building that has an
electrical supply that is more than a branch circuit must have a
grounding electrode system. There are no exceptions.

What you have done so far is great. Since you have an intercom between
the two buildings the code requires you to run an Equipment Grounding
Conductor (EGC) with the feeder conductors which you did. All that is
left to do is to connect the building disconnecting means to any
grounding electrodes at the garage / shop building or in the absence of
existing electrode you must install an electrode system. The point of
termination of the Grounding Electrode Conductor (GEC) to the
disconnecting means enclosure is usually done on the buss bar within the
enclosure that is bonded to the enclosure. In a three wire feeder the
bonded buss bar is the neutral buss. In a four wire feeder the bonded
buss bar is the EGC buss.

So Locate the existing electrodes or install one or more new ones and
connect them to the disconnecting means using an appropriately sized GEC.
--
Tom H