Multimatic 220 AC/DC - Circuit/Amperage

[MMM220ACDC]

I'm a little confused regarding the amperage requirements for the multimatic 220 ac/dc. The manual reads use a NEMA 6 240V receptacle on a 50 AMP circuit. On Miller's site under the FAQ for the MM it seems there are conflicting answers.

I understand using a 50 amp circuit with 240V as the faq reads a max draw of 31.3 amps, but I'm confused regarding using a 120V 20 amp circuit if the max draw is 24.5 amps? I don't have the 50 amp circuit in yet so I'll be using 120V for now. Is Miller giving incorrect info on their faq page?

[ryanjones2150]

Those figures look good to me. I didn’t read them as closely as I would a contract, but sounds right.

I have a dedicated 30amp 120v circuit in the shop for when I use a 120v welder. If you use that machine on any normal 20amp (or less) circuit, it will trip in short order. Do that a few times and then go over and put the back of your hand on that breaker and you’ll see why.

[MMM220ACDC]

ryanjones2150 Yeah, I guess I'm just confused why they would recommend a 20 amp circuit if the welder can/will draw 25 amps on 120. I'll add a 30 amp 120.

[ryanjones2150]

Good plan. You’ll be happier with that anyway.

[MAC702]

A circuit breaker is a thermal/magnetic device. A 20 A breaker will not trip for several minutes at 25 amps. It takes a while to heat up the thermal tripping mechanism. But the higher you go, and the longer you go, and the less you rest in between, the more often it will trip. At high enough amerages, like a short circuit, it will trip immediately via a magnetic field.

[MMM220ACDC]

Thank you, MAC702. I found this youtube vid that helped me understand it better.