Slo_crx1

WHOOOAAAAA DUDDDDE...please do not give electrical info out anymore...you're going to end up with someone burning their house down

220v is usually considered single phase for residential use, meaning 2 hot legs rated at 110v and one ground. In the US power is distributed to your house via 220v this way from your utility pole. Once it hits your meter base, it creates a neutral either through the panel, or via a disconnect if your house panel is a certain distance from the point of entry according to the NEC rules. Your panel is split into 2 sides, or legs, with each leg rated at 110v. When combined with a 2 pole breaker, you now have a single phase, 220v circuit. Single phase refers to the way the ac wave performs...a single line that oscillates at 60hz, positive voltage and then negative voltage of the same value (although technicly all electricity is considered negative in its flow, positive is more widely used as a base value). Now having given you a background in electricty, let's move on to your application.
According to NEC codebook for 2007, the amperage load placed on any breaker cannot exceed 75% of the breaker's rating. Therefore, if the the welder requires roughly 22 amps to perform it's task, then you would need a breaker rated at 30amps. To achieve 220v status, it means you would need a 2 pole breaker, 30 amp rating. Minimum wire size for 30 amp breakers is a #10 wire for copper, #8 for aluminum. So that being said, a #10/3 wire is minimum requirement for your application...2 hot legs @ 110v (black and red wires), 1 neutral leg (white wire), and 1 ground (bare copper wire). The plug you need will more than likely be for a dryer application setup for both a neutral and ground.
Sometimes it pays to have over 10 years in the electrical and electronics industry, although after this week I hang my electrician's belt up for good to work as an electronics technician for the government full time. Ask me any questions you might have if I confused you

Slo_crx1

Oh, and the kid was wrong...2 20 amp breakers ganged together equals 40 amps total. Just thought I'd toss that in there One other thing I forgot...#14 wire is used on 15 amp single pole breakers only, all 20 amp single and 2 pole require a minimum of #12 wire. The only thing you were close on was the "don't need 4-wire for 20a 220v"...only if it's used for electric baseboard heat. Otherwise they all have to have both a neutral and a ground as per safety regulations in NEC.

Toysrme

You got it. Inverters pull power slowly enough as not to trip most breakers, or slow-blow fusing.
I've seen posts of guys with the newer machines are pulling 27-28amps on 20amp circuits without tripping the circuits.
But yes, 20amps is fine for you.

When wiring in 220v:
When the 110v lines have 20amp breakers, it's still a 20 amp 220v circuit, not a 40amp circuit.

Slo_crx1

Incorrect...the total amperage of the breakers are added together when used in a 2-pole setup. The reason the say "20amp" on each one is because the "total" of the 2-pole setup is 20 amps, so as not to confuse the common homeowner. I can take 2 seperate single pole 20 amp breakers, use them in a 2 pole setup, and get a 40 amp setup...due to the fact that the amperage draw is split 50/50 between both breakers. Ever hook up a 440/460 amp single phase? Same principle, although a very uncommon application. 330/340 and 277 tri-phase are more industrial standards anyway.

Toysrme

It's 20 amps.

If you tried to pull a 35amp load on that it'd trip like a mother ******.

Slo_crx1

I'm not saying to pull 35 amps on a 20 amp breaker, 2 pole or single...that's just retarded. I'm saying pull 35amps on a 40 amp 2-pole breaker, seeing that amperage draws that high are confined to 220v use only.

Toysrme

No ---- shirlock.n You can't pull a 40 amp load on a single phase 220v powered by 20amp breakers.

If you can pull a 40 amp load, it's a 40 amp circuit. So don't tell people that don't have the best idea about what they're reading "it's a 40amp circuit" and have them think they can go plug a 40amp device in it. You're all bitchy to the other guy about blowing someone's house wiring up. Why don't you take a step back from that one & see you're just as bad.






ghettoturbo - I am no an electrictian, but I did install a sub-panel, 3 20amp 220v & 2 30amp 220v outlets. And an inlet from my Honda generator so I can power any 2 circuit breakers in my house. I do have a woodshop in the basement that sees semi-regular use of multiple 20 & 30amp machines at one time.

Trust me... You are perfectly fine drawing 22amps through that 20amp breaker. Your wiring, and outlets are not going to melt. And it's a god damned 20amp circuit. Somebody call him a ------ if he says 40amps one more time.

Slo_crx1

You have been the closest out of these guys, at least you have a good working knowledge of electrical. Here's the problem though...you guys are going by what's available readily at your local homie depot and such. You walk in, look for one that says 40 amps, and think you're done. Pop that tab off that connects the 2 breakers together and what do you have? 2 20 amp breakers. Sorry, but a 22amp draw through a 20 amp breaker will pop as well, not to mention heat the wire up which also risks burning down the house. I already gave you the NEC rule for amperage sizing...22amp draw requires a 30 amp curcuit. Plain and simple. I already told you, I've got 10 years in this business...I started an apprentiship when I was 16 still in highschool and have been doing it almost every day from then until now, and I'm 27. Please enlighten me on your many many years as an electrician so that I may belittle you some more.