dpb wrote:
Only can use EMT as ground if is a continous ground all the way to the
main ground, not if it is just a section for protection as sounds like
this might be.

dpb:

Hmm. From the OP I can't tell if that's EMT with individual conductors
or
UF with EMT sleeved over it for protection. If it's the former, and it
is bonded
properly to the main ground, then I don't see any reason it couldn't be
used as
the ground. For instance, if the wiring changes from cable to piped
conductors
at a box in the basement, and the cable ground is bonded to the box,
and
the same situation occurs at the garage, that's a continuous ground,
no?

What is the 15A circuit going to? If it's the garage, why not eliminate
that circuit
and feed it from the new subpanel? Probably I'd prefer at least a 60A
panel in
the garage over a 30A, for that matter, but I do know that sometimes
you need
to safely do something less than ideal. To have a 60A panel, you'd
need at
least 3/4" EMT for four #6 THHN/THWN conductors, since 1/2" is only
allowed 2.

Now for the conduit fill for your 1/2" EMT:

#10 THHN area = about .021 sq in
40% of 1/2" EMT area = .122 sq in allowed

You can legally pull 5 #10, THHN insulated conductors into your 1/2"
EMT.

If you must keep the 15A circuit in there (perhaps serves outdoor
lights?):

#14 THHN area = .010 sq in
#10 THHN area = .021 sq in
40% of 1/2" EMT area = .122 sq in allowed

4 #10 THHN = .084 sq in
3 #14 THHN = .030 sq in
Total .114

You can also legally have 4 #10s and 3 #14s. It will not be a picnic,
but
you were not looking for a picnic; you were trying to wire. I would
pull
the #14s out first, then pull all the wires at once, and once again be
sure
to use stranded wire and lube, and of course invest in a fish tape if
you
don't already have one. In fact, buy two, and green is prettier than
red.

One thing I don't know off hand without referring to the NEC: will he
need to
use THWN inside the conduit if it's (as it sounds to be) buried in
concrete?

Please feel free to poke holes in my figuring. I don't have my
handbook
in front of me just now (on break at work)

Cordially yours:
G P.