Winston wrote:

Don Foreman wrote:
On Thu, 29 Nov 2007 12:15:57 -0800, "SteveB"
wrote:


I've just wired an external box with 10/3 solid copper 600v. wire with AWG
running about ten feet from the panel to an outside outlet. I need to run
it 100' to my slab where I weld. I want to use MAINLY a Lincoln SP 175+,
and the input amperage on that is 22 amps. Can I run a 100' of 10/3 AWG
with stranded wire safely? It's the big yellow one available at HD.

Now, I also have an AC 225 Tombstone that pulls 50-63 amps. How about that
one?

I'm probably going to get a gas driven welder/generator in the future, but
this is what I have to work with NOW.

Steve


Safely, yes. Voltage drop: resistance of 200 ft (round trip) of #10
copper is about 0.2 ohms, drop of 0.2 volt per amp or about 4.4 volts
at 22 amps -- shouldn't be an issue. It'd be 12 volts at 60 amps or
5.5% of 220V, shouldn't be an issue.

Power dropped by the extension cord is 97 W in the first case and 720 W
in the second case. That second figure sounds high to me.

http://www.belden.com/pdfs/MasterCat.../3.28_3.32.pdf

Page '3.30' has a table showing ampacities for multiple conductor
cables. Table 4 shows 40 A being an upper limit for 10 AWG neoprene
insulation at 86 F ambient (or cooler). That's 320 W loss or 44% of the
loss at 60 A.

Were I you, I would buy another identical extension cord and connect it
in parallel with your existing cord. You'd have 0.10 ohm loop
resistance, a drop of 6.3 V or 397 W at 63 A. That should limit power in
each cord to 200 W and you get to use the additional 320 W (that would
have been wasted as heat in one cable).

--Winston

NEC Article 630 allows supply conductors for arc welders to be "over
fused" based on the welder duty cycle (table 630.11(A)).