Pason:

Pason wrote:
The garage has a gas line for a heater to it so not running a ground
wire and bonding the neutral and ground in the subpanel wouldn't work,
right?

Right. Nice garage, BTW. The gas line must be bonded to the ground
system in the house, and if you have 2 separate grounds in the garage
(gas line and garage service ground) it's possible that a hot wire in
contact with the gas line might create a complete circuit through
some poor shlub with one hand on the gas heater and the other on
something connected to the garage ground. Shocking.

You aren't allowed to bond the neutral and ground in the subpanel. If
the
neutral was to break somewhere between the main and subpanel, the
ground could become a return path for neutral current. If you
consider
the garage panel a 'service', as zxcvbob mentioned, you have to have a
separate ground system. In that case you could bond the neutral and
ground. The only place neutral and ground come together is in the
service equipment.

What about running three #8 wires and a #10 ground for a 40 amp
subpanel? Hard pull? Anyone know a good resource for EMT IDs or areas
and wire gauge areas?

Area of #8 = .037
Area of #10 = .021
40% area of 1/2" EMT = .122

..037 x 3 = .111 + .021 = .132 .122
Can't do it. I think for a subpanel you need to have the feeders and
ground the same size anyway. (Handbook not here, yadda hey etc.)

The NEC has tables. I suggest a trip to the library, which may have a
copy,
or a copy of the residential manual (a condensed version of the NEC).
Other good quality basic wiring books (not the kind that say "use the
biiiiggest
box you can find for every outlet so you don't have to think about box
fill"
may also have that. Wire and conduit manufacturers' websites may have
tables, too.

zxcvbob wrote:
An outbuilding technically can only be fed from one circuit. If both
circuits run thru the same conduit and disconnect at the same box in the
garage, it's probably not a big deal.

Ah. I thought something didn't seem quite right.




I think that would still be possible, but again it would only be 30
amps, right? If that's the only option that's okay however I would
like to maximize the power to the garage.


Two options. I'm not sure which is better under the 2006 electric code;
my code book is a few years old:

To maximize the power to the garage AND reuse the existing conduit, pull
the existing wires out and replace with three #8 THWN wires. That will
give you a 40A 240V service with 2 hot wires and a neutral. You will
have to make a new ground at the garage and bond it to the neutral, and
you can't have any other grounded pipes or wires connecting the garage
to the house. (CATV, telephone, metal gas or water pipes, etc.) The
subpanel in the garage needs to be rated for Service Equipment, but
that's not a big deal because almost all of them are.

You might can run the three wires and use the EMT as a separate ground,
but I don't know if that's kosher. You'll still need to drive a ground
rod (or two) at the garage. In that case, you would not bond the ground
and neutral at the garage subpanel, and you wouldn't care about
phone/gas/water lines connected back to the house.

Best regards,
Bob