Good afternoon Elmar,
According to my "Pocket Ref" (ISBN 1-885071-00-0), the following applies for
240 VAC feeds for a 2% drop using COPPER:
60 Amps @ 240 VAC (14,400 V-A), #4 is good for 150'.
50 Amps @ 240 VAC (12,000 V-A), #6 is good for 110'.
on the next page (122) they show that a 1-1/4" conduit is suitable for 5
each #4 wires or 6 each #6 when using type TW. The book recommends checking
the NEC (National Electric Code) when using wire types other than TW.
I'd take the time and discuss this with your electrical inspector before
pulling the wire. My preference is to use the #4 to minimize the voltage
drop ... but I'm not buying the wire! If you want, there's a whole page
(page 120) dedicated to calculating the voltage drop for a given distance
and cable size ... armed with this information, you may well be able to
convince the electrical inspector you do know what you're doing. You could
also ask several electricians for a quote on the job, requiring a detailed
BOM as part of the quote. You can also ask for the rate where you supply the
labor, they provide the materials and do the final hookups.
I haven't bothered with aluminum wire, though the calculations page does
include the conversion factor required. I don't like aluminum wire; the
cold-flow, corrosion and resultant I2R losses make it no fun. Yes, I know
NoAlox, proper CU/AL fittings and PROPER torque on the fittings prevents
most of the problems, but I just don't like the additional I2R losses as
well.
The Pocket Ref by Thomas J. Glover, 2nd Edition, 28th Printing - January
2001 (C) 1989-2000 by Thomas J. Glover ISBN 1-885071-00-0
HTH
Rick
P.S. You'll find that over the years the REC has remained pretty much the
same ... lots of people with highly valued opinions (well, THEY value them),
some snide remarks, and a few people willing and able to point facts your
way. Take it all with a grain of salt, and verify everything, and you'll be
fine. Funny though, I haven't checked the REC for about a year, and nothing
has changed except some of the familiar names are gone. Back to the woodwork
(literally AND figuratively).
"Tom Veatch" wrote in message
...
On 21 Oct 2004 11:33:53 -0700, (Elmar) wrote:
Just built a WW shop about 50' (cable length) from my service panel.
What gauge wire should I be using? 4-4-4-6? If so, should I pull
them all individually? Or buy the premade 4-4-4-6? What size
conduit? 1.25"?
Shop is 16X20, may consider a/c eventually too. Aside from that, I
have all the other goodies, Table Saw, dust collector, Compressors,
I'll need a ton of lighting, etc...
Would I ever really exceed 70 amps? Could I maybe get away with
6-6-6-6?
Thoughts? Experience?
Thanks!
Elmar
My shop is about the same size, etc. I have a 60 amp drop and about 150'
of
cable run. The wires are individual #6 AL.
Lighting is 6 4' fluorescent fixtures w/4 40w bulbs in each. There is a
small
window unit air conditioner on 120v. Most of the stationary tools are
wired for
240. Heat is LP gas.
Maximum simultaneous load is lights plus A/C (on opposite phases) plus 3hp
cabinet saw. No dust collector, yet. The lights do react to saw startup,
but
that is the only negative I've noticed. No breaker trips, so far.
However, if I had it to do over, I'd go with a larger gauge (and use CU
feeders
instead of AL) for a couple of reasons. One, easier to increase capacity
down
the road, and, second, reduced line losses today. I'm pushing the limits
with
the existing installation.
Tom Veatch
Wichita, KS USA