I did one just two months ago in NY. A detached garage with an existing
three wire feed in pvc to the house. I had to run two ground rods and did
have to bond the neutral. Like Bob said, I was given specific instructions
about not having any other conductive, grounded paths. i.e.. telephone,
catv, gas, water



"zxcvbob" wrote in message
...
Chris Lewis wrote:

According to zxcvbob :


As I understand it, it's either 3 wire plus new ground electrode, or 4
wire with
no new ground electrode. In both cases with the ground/neutral lug
_removed_
in the subpanel. Not a mixture of both. Ground loops.


If you run 3 wires (assuming 2 hot wires and a grounded neutral) you most
definitely do leave the bonding lug (screw) in the panel -- the panel is
a "service entrance".


We're talking subpanels (downstreams from main panels) here exclusively,
not
separate service entrances.

If you leave the bonding lug in the panel, the subpanel's grounding goes
through
the subpanel feed's neutral. Distinctly bad. Lose that neutral and all
hell
breaks loose.

Subpanels always have their bonding lugs out. Either they get their
grounding
from the fourth wire in the feed, or they get their grounding from
grounding
electrode[s]. In neither case is it connected to the neutral.


From the main panel's perspective, we are talking about a subpanel.

But from the outbuilding's perspective, the box is a service entrance and
must be listed as such if it is fed without a separate grounding conductor
(which is what I think you were proposing.)

Maybe the rules are different up there in Canada, but I installed a 3-wire
240/120V feeder to an outbuilding 1.5 year ago and had it inspected. The
incoming grounded neutral wire is bonded to the panel, and I had to add a
grounding electrode.

Bob