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Thread: Question about NEC code for welding circuits.

  1. #1

    Default Question about NEC code for welding circuits.

    I'm hoping one or more of you out there will be able to help out with a couple of questions I have.

    Here is some background information about my situation. I just purchased a Hobart Handler 187 wire feed welder. I need to set up a circuit on which the welder can operate. Based on what I have read in the owner's manual, and what I have read on the internet I have come up with the following information.

    This Hobart welder has an input amperage of 20.5A and a duty cycle of 30%. Based upon NEC 630-11(a) I can take that 20.5A and multiply it by .55.

    So, 20.5A x .55 = 11.275A. Am I correct in interpreting this information to mean that I can use #14 or heavier wire for my circuit? I think this is correct (plus the owner's manual from Hobart says #14 is the minimum wire size allowable).

    A second point is that 630-12(a) leads me to believe that in order to determine the correct size of circuit breaker I must not exceed 200% of "the rated primary current of the welder". Does that mean that I take the 20.5A and simply multiply it by 2?

    If so, that would give 20.5A x 2 = 41A. I am interpreting this to mean that I cannot use a breaker that is larger that 41A for the circuit (assuming that I match that breaker with a suitable wire size).

    At this point I am of the belief that I could run a suitable circuit using #10 wire and a 30A breaker using a 6-50 receptacle.

    However, why could I not just wire up a circuit using #6 wire, a 50A breaker, and a 6-50 receptacle? In the future I may purchase a stick welder with 50A input. Could I use such a circuit so that I could plug either machine into the same receptacle? I think this would be less of a hassle than running two separate circuits. I was prepared to install such a circuit but then ran into 630-12(a) on several discussion forums.

    Any thoughts, inputs, corrections would be greatly appreciated.

    Thanks folks.

  2. #2
    Join Date
    Dec 2003
    Location
    Kent, WA
    Posts
    8,427

    Default

    I believe your math to be correct. I found it strange you determined you could use a #14 wire on a 40A circuit and then decided to go with 30A wire on a 30A circuit with a 50A receptacle...

    There's nothing wrong with what you propose.

    You may have a problem using the smaller welder on a 50A circuit -- that breaker may be too big for it. You could run a 60A feeder on #6 wire to a subpanel, then hang a 30A and 50A receptacle off of it using breakers of the same size. Then you could support both welders, but probably not both at the same time. I'd use 6-3 cable in the feeder so you have 120V available too should you ever need it.
    Mark
    Kent, WA

  3. #3
    Join Date
    Dec 2003
    Location
    WA
    Posts
    4,631

    Default

    I believe your math to be correct. I found it strange you determined you could use a #14 wire on a 40A circuit and then decided to go with 30A wire on a 30A circuit with a 50A receptacle...
    I didn't find it strange seeing that the op has pulled most his info from other sites. For the most part I agree with suemark, yet what's new.
    Learning brings success. While you are waiting, I'm getting better!

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