On Mon, 10 Jun 2019 09:09:50 -0700 (PDT), trader_4
wrote:

On Sunday, June 9, 2019 at 10:40:23 PM UTC-4, wrote:
On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

If you only have 3 wires in the feeder going to the shop you need to
bond the neutral and ground out there too or there is no path for
fault current. You also need a ground electrode out there. Current
code requires a 4 wire feeder and isolating neutral and ground in sub
panels but if the wire was already there when the 1996 code was
adopted the 3 wire feeder is grandfathered in.
Ground loops are not an issue but carrying circuit current in the
grounding conductor is, That is why you do need another ground
electrode. Essentially you are creating another service in the second
building and creating a new ground reference there.
In the electrical biz, you can't have too many ground electrodes but
they all need to be bonded together.

His main question appeared to be whether the neutral and ground need
to be bonded in the MAIN panel if they are already bonded at the meter
which is right next to it?


That is open to debate. A strict reading of the NEC says the PoCo
should not have bonded the neutral in their can but since they do not
have to follow the NEC, the language was tweaked a little (again 96 as
I recall) so it is all "service equipment" and you still rebond the
neutral in the service disconnect enclosure where the code says the
"Main Bonding Jumper" is supposed to be. That is usually just a green
screw on the neutral bus or a strap.
The hitch is that the MBJ "shall remain accessible" and inside the
meter can isn't. Sanity prevailed. Meter cans are usually made so the
can is bonded to the neutral anyway. There is no way to avoid it.

Some inspectors require that there be no metallic paths between the
meter can (a PVC sleeve) and that you only bring 3 wires in. Then we
did not care what they did in the can, the MBJ was clearly in the
service disconnect enclosure.

The grounding electrode conductor can land anywhere from the service
point (usually the mast head on an overhead drop) to the service
disconnect enclosure. That is how they can land it in the meter can.
If you have an underground service lateral, the service point is
usually the transformer connection at the street. Yes you usually own
that wire in the yard. You typically do not own an overhead drop.