On Fri, 07 Nov 2003 19:52:48 -0800, Jeff wrote:
Hello David,

Your math, while correct, only applies to purely resistive loads, and does not
apply to a highly inductive transformer device like a welder. What happens is
that the voltage and current get out of phase, (called power factor) so you can
have much higher current draw on the input of the welder versus the power output
of the welder.

Correct, which is why you want to use a heavier wire and a heavier
service breaker than would be needed for a purely resistive load.

Furthermore, there is an issue with an oversized breaker. Could be a fire risk
plugging it into an oversized breaker. You should put a 20 amp breaker feeding
the outlet for the welder.

If he's using #4 wire, a 50 amp breaker is not oversize. It will trip before
the wire overheats dangerously. That's what Code says it must do. What
it *won't* do is nuisance trip with the reactive load provided by the welder.

The welder has its own internal breaker, CB1, a 25 amp delay breaker,
which is designed to protect the welder in case of a welder fault.
Because it is a delay breaker, it won't nuisance trip like a 20 amp
service panel breaker would.

Gary