In article , Peter De Smidt wrote:
I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.

Hopefully, these are fed from one duplex circuit breaker. If not, it's a Code
violation and a fire hazard.

I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

How many wires the Code allows in the conduit depends on the type of
insulation on the wires, but for the types of wire that you'd buy as single
wires (not cables) at Menard's, yes, the Code allows 5 or even 6 #10 wires in
a 1/2" conduit.

Please note, however, that there is a *large* difference between the number of
wires the Code permits in a conduit, and the number of wires that can be
easily pulled through the same conduit. Even though the Code permits five #10
wires in a 1/2" conduit, you will encounter substantial difficulty in trying
to pull them through it.

If you succeed in pulling four #10 wires through this conduit, you're still
limited to a 30A version of what you have now: two 30A 120V circuits with a
shared neutral. What will you do with a 30A 120V circuit? Not too many 120V
tools require 30A.

It would help a lot if you provided more information about what your objective
is. What tools do you want to run in your garage/shop, and how much current do
they require?

--
Doug Miller (alphageek at milmac dot com)

How come we choose from just two people to run for president and 50 for Miss America?