Thanks all, I understand now.
I woke up in the middle of the night and figured out part of it.
The neutral is only bonded to ground at the service (which I knew).
If it gets bonded elsewhere, then the conduit also becomes a conductor
(bad).
For some reason, in my brain, I was equating the neutral bonding
issue with that of adding a ground wire and I was thinking that was
bad also. That's where most of my confusion came from.

The last part you guys answered today that it is ok to add
an additional ground wire. That is what I wanted to do in the
first place. That will get added because I'd trust the ground wire
more than the conduit.

The control wires for the VFD will be shielded & grounded properly per
VFD instructions and only @ the VFD. So there won't be any
ground loop problems with them.

Wayne D.

On 23 Mar 2005 10:38:16 -0800, jim rozen wrote:

In article , Wayne says...

So the VFD is only supposed to be grounded by conduit and nothing else.

This also implies that the lathe is only grounded through the conduit
and nothing else.

I shouldn't also have a green ground wire run through the conduit from
the
service
to the VFD and lathe in addition to the conduit.

To make it clear, you most likely would not run into any
ground loop issues by running a green wire all the way
back to the service entrance.

I would personally do this if it were my installation.

Many codes allow the conduit itself to be used in place
of the green wire as a grounding conductor. I don't think
any codes prohibit putting a green wire in the pipe as well.

This means you would have to run that wire back from the
sub-panel to the service entrance, as it does not exist there
at the moment.

Jim