"'nuther Bob" wrote in message
...
If you only have a service panel - as in the meter is on a box and
direct wired to a 100A breaker in the service panel - are there rules
about separating ground and neutral ? In my box, it's all one bus bar.
I also have a subpanel off the main panel - do the rules change when
we get into the subpanel ?

Yes. At the service, where you have the meter and main breaker, this is your
Service Disconnect and it is where your "Service" stops. This is the last
place that neutral and ground are connected together. If you have another
panel in the house, this is a subpanel and it must have a 4 wire feeder and
the neutral and ground busses must be isolated. Only the grounding bus may
be electrically connected to the panel enclosure in a subpanel.

There is an exception to this for a panels at detached buildings, but there
must be no electrically conductive path between the service equipment and
the remote panelboards (ecxcept for the service feeder itself). Typical
connections that would mandate a 4 wire feeder to a remote building --
grounded phone or CATV wires, or metal water, gas, or oil pipes. I also
think that mobile homes must have a 4 wire feeder from the typically yard
mounted pole/disconnect.

The idiot that did my house ran a 3-wire feeder to the pool shed (which
because its a pool is not allowed), but there is an oil pipe in there and
another one in the house. The oil pipe was a parallel neutral back to the
panel. Thankfully, this pipe was not loose or arcing in the oil tank!

--
Mark
Kent, WA