[AT] grounds

[Dudley Rupert]

Thanks for the responses to the subject post.  I read them and generally
agreed with them but I was puzzled as to why you folks were puzzled by what
I had posted!  So I then reread my post a couple of times to see if I might
have made something clearer and/or if I had plain stated something wrong or
misleading.  I think I came up with an item in each of these categories.  I
hope the following helps in providing some clarity -

Dudley

I wish I would have described the sub panel grounding scheme in a bit of
detail but I didn't so I will do it now.
Two types of ground bars are used in a sub panel.  One type (which I will
just arbitrarily call the Equipment Ground Bar) is physically and
electrically connected to the sub panel frame/enclosure but is isolated
electrically from the other ground bar type.  The Equipment Ground Bar is
required by code to be connected to a ground rod (actually two rods if we
want to get precise).  All equipment grounds (e.g., the bare copper third
wire that runs in "romax") are required to terminate in/on the Equipment
Ground Bar.

The other type of ground bar used in a sub panel, which I will just
arbitrarily call the Neutral Ground Bar, is electrically isolated from the
Equipment Ground Bar and thus it follows from the sub panel frame/enclosure
as well.  The neutral wire that comes from the main service panel terminates
in/on the Neutral Ground Bar.  All neutral/return wires (e.g., the white
wire that runs in "romax") terminate in/on the Neutral Ground Bar.  The
Neutral Ground Bar cannot be connected to a ground rod; otherwise it could
not be electrically isolated from the Equipment Ground Bar.  And, as we
would expect, if the code is going to say anything at all about this ground
bar it would have to say that the attachment of it to a ground rod is
prohibited.

And now for the wrong - or at the very least misleading - part of my first
post.  In it I stated the following.
 "... and then ran 3-wire 240 from the house down to the barn and put a 100
amp sub panel there with the ground lug connected to a ground rod (and, of
course, to the neutral wire from the house panel)."
That last part of that statement makes it sound like there was only one
ground lug in the sub panel and that I connected both the ground rod and the
neutral wire from the main service panel to it.  That is wrong, of course,
as the above description of sub panel grounds clearly, I hope, points out.
And I apologize if that mislead any of you into thinking I was saying I
connected a ground rod at the sub panel to the Neutral ground.

In my initial post I expressed my perplexity as to Warren's friends advise
that he didn't need a ground rod at his shop ... and I am still perplexed.