Chris Friesen wrote:


I'm purchasing a house with an attached garage, and will be adding a
subpanel for use as a shop. The garage is already insulated and
drywalled, so I'll be running conduit (most likely EMT).

The most-filled run will have three 20A 120V circuits for outlets wired
with #12, and 2 30A circuits for 240V wired with #10. (One 240V for the
dust collector, and one for everything else.)

I'm currently planning to run a single #10 ground wire (bare or green)
to ground everything on this run. I think this meets code, but I'd like
confirmation.

With EMT and metal boxes you aren't required to run a ground wire, but
if you do #10 is OK.

Assuming the above is okay, I'll have 11 wires in that conduit. Given
that I'm allowed 11 #10 wires in a 3/4" conduit, does that sound like a
reasonable conduit fill? Max spacing between conduit openings will be
about 10 ft.

Using THHNs the wire fill is about 35%. Should be managable for 10 ft.
Carefully avoid wire crossovers feeding the wire into the pipe.

Since this is a one-man shop I'll only ever be using two tools at once,
maybe three if someone is helping. I'm working on the assumption that
my load diversity is enough that I can use the 70% ampacity derate for
10 conductors. Is this reasonable, or do I have to go down to the 50%?
Should I go with two 1/2" conduits instead of a single 3/4"?

You are (I assume)ignoring the ground wire to get from 11 to 10 which is
correct. At 10 wires the derate is 50% - you aren't likely to use them
all at once, but use in the future is unknown. If you ran a common
neutral for 2 of the 20A circuits the wire count would be 9 (actually
only 8 since the common neutral doesn't count) and the derate 70%. If
using THHN wire in a dry garage the "ampacity" of #12 wire is 30 amps
(but 20A max breaker). Using 70% derate the allowable current is 21A, so
they can be on a 20A breaker. The "ampacity" of a #10 THHN wire is 40A
(30A max breaker). Derated to 70% gives 28A - should be on a 25A
breaker. If the conductor count is 6 or less, the derate is 80% which
gives 32A for the #10s - can go on a 30A breaker. If the dust collector
is hardwired the rules change.

Finally, what's the best way to pull this given that the various wires
are going to different places, and one of the 240V circuits is going
right to the end? Do I pull one section at a time with all the wires
for that section?

Yes, pull all the wires in one run at the same time. Lot less mess in
the boxes if the wires unused in that box loop through without splice
(but harder to pull). I agree with Bob - box fill with that many wires
is another thing to watch.

bud--