If the welder is designed for a 20A circuit, there is absolutely no
advantage to increasing the breaker or receptacle size. If the run is long,
it may be advisable to increase the wire size. An oversized breaker will
only give you more opportunity to overload or damage the welder without the
breaker tripping, although breakers are not really intended to protect
connected equipment. Higher capacity than needed is not somehow magically
That said, it costs little more to install a higher capacity circuit if you
think you might need it in the future. I personally would probably install
#10 wire with a 20A breaker and receptacle. This could be easily upgraded to
a 30A circuit.
630.12(B) For Conductors. Conductors that supply one or more welders
shall be protected by an overcurrent device rated or set at not more
than 200 percent of the conductor ampacity.
It gets more complicated than that when you read all of 630 but this
is what he was talking about.
The manufacturer usually does this code thrashing for you in the
manual when they tell you what the recomended circuit should be..
It goes like this: If you are going to weld for four hours straight with
the biggest wire and the highest settings, you will approach the limits of
your breaker. If you are going to weld for short intervals, with smaller
wire, and at the lower settings, a smaller breaker will do.
I have a Lincoln 175SP+ wirefeed welder. At the lower settings, it draws
nowhere near the amperage as it does at higher settings. But, when I had
the electrician do the breaker, he looked at the chart and suggested a
breaker that was 5 amps over that amperage. You don't want it so oversized
that it REALLY has to get hot to pop. But you don't want it kicking off
when you're in the middle of a long run. I'd do a 25.
I'd also check with the manufacturer and see what they recommend. They want
the machine to run right, and for you not to install it incorrectly and have
BTW, there are only two choices for mig welders. Lincoln and Miller. The
rest are crap that are hard to get serviced or to find replacement parts
Steve, who learned to weld in 1974
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