On Thu, 01 Oct 2009 08:48:10 -0600, SteveB wrote:
I need to run about 190' from breaker box to my shop. I have a double
pole breaker on a 200 (+ or -) v. that says 30 on each leg.

In the shop, I will be running a SP175+ 220v MIG Lincoln welder rated at
22 amps, but that only when cranked fully open. Most of the stuff is
half that. I will be running about four shop lights, radio, and a power
tool or two at any given time. My electrician buddy has suggested IIRC
a #6 wire.

Does this sound adequate? Do I get the bundled wire, or use the
separate strands? How much voltage drop on that far? Is #6 marginal,
or should I slightly oversize?

In NEC table 310-16, #6 copper wire is rated at ampacity of 55, 65, or
75 amps, depending on its type of insulation, so the wire is heavy
enough to meet national code requirements when using a 30A breaker.
As Igor or someone else mentioned, you could reduce heavy-load (100A)
voltage drops by 5 to 10 volts by going to #4 or #2 wire.

What I think would make sense is 4-conductor aluminum wire (3 #2 Al,
insulated, and 1 #4 Al ground wire), attached to a 100A breaker in an
entrance service panel. #2 Al ampacity is slightly larger than #4 Cu
ampacity, ie 75, 90, or 100 for the #2 Al and 70, 85, or 95 for the
#4 Cu, again depending on type of insulation. #2 Al should cost
somewhat less than #4 Cu. (Also see ebay # 180398856402, appears
to be 300' 3-cdr #0000 Al, around $1.58/ft when you count shipping.)

Bundled wire would be easier to pull but might cost a little more, and
with heavy current it heats up a little more than not-bundled wire.

Mike (my electrician) will put the right thing, but I just wanted to
start shopping and getting prices together. BTW, does anyone know what
#6 copper solid strand goes for now? There would be just about a 200'
run.

I think ebay prices (about $2/foot for #6-3+ground; search for romex),
even with shipping, will beat prices at (eg) Lowes or Home Depot, but
haven't been able to make either of http://www.lowes.com or
http://www.homedepot.com reveal anything about wire heavier than #8,
so that's just a guess. (When I bought about 90' of 3-cdr #2 Al and
1-cdr #4 Al at Lowes a few years ago, the price worked out better
than ebay, due to sales, so it's worth going and looking.)

I did get about 800' of 2.5" underground conduit for free, so that
helped.

Use sweeps (big-radius ells) rather than the usual ells on turns, and
it might make sense to pull the wire through any long straight sections
and then slide the corner pieces near the ends onto the wire, unless
you like using a half-ton winch to pull the wire.

--
jiw