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Circuit breaker requirement

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  • Circuit breaker requirement

    I have a new Miller 180 welder, the manual specifies MAX amperage for the circuit breaker as either a 25 amp time delay or a 30 amp standard breaker.

    In both cases these are two pole breakers for 230V service correct, so both poles should read either 25 amp for the former or 30 amp on the latter correct?

  • #2
    I believe the wording in these manuals should be changed due to the DIY crowd wiring. They are written for the electrician. The 25 or 30 is max when the minimum wire size is used, this machine can run on circuits to 50A provided a 12 wire or larger is used. Ideally I like a 10 wire and a 30A double pole breaker for this class of machine (up to 50 is acceptable) but the 10/30 is tailor made for it.
    Law probably prevents them from writing a layman's language section to the wiring guidelines. These small machines really could use it in the owners manual.

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    • #3
      Use a 30A, two pole breaker. If you are running this circuit exclusively for THIS welder, you can technically run 14g wire, but I wouldn't go with anything smaller than 12g. 10g if it takes more than 50 ft to get from the box. See National Electric Code article 630.

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      • #4
        Originally posted by Bodybagger View Post
        Use a 30A, two pole breaker. If you are running this circuit exclusively for THIS welder, you can technically run 14g wire, but I wouldn't go with anything smaller than 12g. 10g if it takes more than 50 ft to get from the box. See National Electric Code article 630.
        I'm not an electrician, but 14g wire for that machine scares me from across the internet. I guess if it meets code, somebody a lot smarter than me has made certain it's ok.

        I've got 8 going to mine, but I chose that as much because I wanted to leave myself room for expansion. If I'm doing it for me, it's going to be overkill. Relatively speaking, the wire is cheap.
        Millermatic 180 Auto Set

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        • #5
          I will agree, the 14 is not good even though it meets the letter of the code,,, and since that is a minimum I dont see a reason Miller couldn't up that to a 12, wouldn't be any skin off their rear at all and avoid a lot of confusion.

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          • #6
            perfect responses guys.

            I'm going to be running all of 2 feet of wire, since I want this right next to my subpanel.

            Its going to be for the welder exclusively, and due to the minimum length of run I have no qualms running 10 or even 8 awg wire since its not going to cost much more than running 14 anyway.

            And 2 feet from the box gives me a location that I can weld using the factory supplied cord in 95% of my garage no problem, and easily to my work bench.

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            • #7
              I used what the electric supply store suggested. It's been a few years but I'm pretty sure it was 10 or better. I know I opted for overkill just to be safe so it's more likely in the 8 range. The breaker I used was a 40a. It worked fine for mild steel, but would trip sometimes if I welded aluminum (180 syncrowave). So, I replaced it with a 50a and have had no issues the last few years. Most of the time when I weld mild steel I rarely work the machine hard enough to kick the cooling fan on. Aluminum on the other hand makes the meter spin.

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              • #8
                Run an 8 then, you would be ready for a breaker change should the need arise for a larger machine. 8 wire covers most machines that would find their way to a home shop.

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