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Thread: plug and circuit question

  1. #1
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    plug and circuit question

    Hi

    I am about to get the HF Dual Mig 151 welder (my first welder) and from what I've read, it doesn't come with a plug.

    The welder spec's are:
    input 230 volts, 21 amps, single phase, 60 Hz

    I am going to plug it in to a 240v receptacle that has a 50 amp dedicated breaker.

    Do I need a 50 amp plug and receptacle or is the 50 amps the limit? Also I've read that the power supply cord is very short. What gauge wire would be safe?

    In most of my reading I've read "I replaced the power cord" or "added a plug" but no actual details on the wire or plug that they used.

    Thanks

  2. #2
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    Re: plug and circuit question

    50 amps is the limit for that circuit.
    If you use a 50amp plug and receptical, it would be ready if you get a bigger welder.
    The cord is pretty short at 6ft or so,and I think it is 14g, if you put a 10ft 12g cord on.it should be ok.
    I would need to check the voltage drop tables if I was to suggest more feet of cord.

  3. #3
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    Re: plug and circuit question

    Thanks for the help

    The more I'm looking into the electrical demands welding requires the less I think this is going to pan out for me. My electrical service at my house is very dated. I don't want to start cooking wires in the walls. It's our first house and it was about 50 years old when we got it.

    I'm starting to think of trying out O/A welding. I'm not in a rush. This is just a hobby I was thinking of getting into. There is also an airgas retail store 3 miles from my house.

  4. #4
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    Re: plug and circuit question

    The small welders like the Harbor freight, only pull about 3,000 watts.
    A 220 line at 50 amps would be able to handle 11,000 watts.
    The welder can only run intermittently so the safety margin is even better.
    O/A is a good method of welding,cutting and heating,very versatile within its limitations.
    Whatever you decide,try to find a local welding class.
    It's worth it just for the practice and materials.

  5. #5
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    Re: plug and circuit question

    I'm in the same boat as you with an older house and an insufficient panel. I'm in the process of roughing in a new panel (100 amp #4 feeders) out in the garage and I'm going to tie it into my Service entrance. You could probably do the same thing, but if you've never done it before spend the money and have an electrician do it for you. I do stuff like this for work everyday and I figure it's going to cost me about $150- $200 for the parts (getting some leftovers from work) and talking my local power company into upgrading my service entrance.

  6. #6
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    Re: plug and circuit question

    You will need a minimum of # 6 copper wire, which is good for 55 amps. # 8 copper wire is good for 40amps, #10 copper wire will only handle 30 amps at 220 volts, #14 Copper wire is only good for 20 amps. This is allowable ampacities for wire in a raceway, cable or earth at 30 degrees C. (86 F)

  7. #7
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    Re: plug and circuit question

    Getting an updated panel is one of our big ticket items for the house. When we get around to it I'll have them put a sub panel in the garage. Make things a little easier.

    Thanks for all of the great info guys. I really appreciate it.

    I think I might have to go with a gas system. I've used it to cut steel and rebar when I worked for a demolition contractor. I didn't even know you could weld with one until just recently.

    This whole crazy welding scheme came about because I wanted to build a BBQ smoker out of 55 gallon drum. It went from wonderful BBQ to getting my electrical service completely overhauled.

    But really thanks for the help.

    I'm going to go bother the O/A guys now with my remedial questions about heat and metal.

  8. #8
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    Re: plug and circuit question

    Quote Originally Posted by mikelisko View Post

    This whole crazy welding scheme came about because I wanted to build a BBQ smoker out of 55 gallon drum. It went from wonderful BBQ to getting my electrical service completely overhauled.
    .
    That's nothing. Once you start welding, you will find all kinds of stuff you never knew you needed. Like more welding machines, grinders, clamps, compressors, saws, plasma cutters, presses, brakes, fork lifts, tractors, flatbed trailers, generators, motorcycles, a huge shop, and I'm sure I forgot some stuff.
    Miller Challenger 172
    Miller Thunderbolt AC/DC 225/150
    Miller Maxstar 150 STL
    Victor 100C
    Victor Journeyman
    Oxweld OA
    Harris O/A
    Smith O/A little torch

    No, that's not my car.

  9. #9
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    Re: plug and circuit question

    preach on brother

  10. #10
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    Re: plug and circuit question

    Sounds like you've already made up your mind, but do be aware that a small welder like that will not tax your electrical system in a meaningful way. If it bothers you, don't run the clothes dryer while you're welding. Or better yet, plug it into the dryer receptacle.

    Or develope some skills with a torch. You'll be able to move sideways into brazing and soldering, too. Like arc welding, once you learn what you can do with it, you'll keep finding new things to do.

  11. #11
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    Re: plug and circuit question

    (slapping own forehead) Of course I could plug it into the dryer. I didn't even realize that.

    Our dryer is on its own 30 amp breaker and the welder is rated at 21 amps. I just checked the southwire calculator and I could use 50 ft of #10 wire. Add a 30 amp plug and I'm in business.

    When looking at welder specs, it's the input amperage I'm looking at right? The 120 amp output is what the welder is doing right?

    Thanks tkanzler!!

  12. #12
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    Re: plug and circuit question

    Quote Originally Posted by mikelisko View Post
    Our dryer is on its own 30 amp breaker and the welder is rated at 21 amps. I just checked the southwire calculator and I could use 50 ft of #10 wire. Add a 30 amp plug and I'm in business.
    Your dryer is likely rated about the same current, and the element cycles once it gets hot enough, so in a sense, your welder and your dryer present very similar loads to electrical system. No worries.

    Oh, and use cord, not NM (Romex) for an extension. You'll probably find better pricing at a real electrical supply house than at HD or Lowes. Ask for 3-conductor cord, which will have all three conductors insulation (black, white, green). If your dryer receptacle is 4-pin, you still only need 3 conductors - hot, hot, ground - the neutral isn't needed or used.

    Quote Originally Posted by mikelisko View Post
    When looking at welder specs, it's the input amperage I'm looking at right? The 120 amp output is what the welder is doing right?
    That's right. 21A is the average input current (at 240V) while welding at it's highest setting. The welder is rated 20% duty-cycle at that output, so you can run at full power for 2 minutes straight, then let it cool (turned on, with the fan running, but not welding) for the next 8 minutes. That may not sound like much time, but if you ever timed that sort of light-duty welding, it's really not restrictive. You'll probably not be working at the highest setting anyway, so duty-cycle improves from 20% as the welding current goes down.

    Edit: Almost forgot - there are two common 'grades' of cord at the big box stores. SOOW and SJOW, possibly with some minor variations. The "J" is junior hard service cord, with 300V insulation, oil and water resistant, which is fine for what you want UNLESS you typically walk all over it, or drop molten steel on it a lot while cutting, or whatever, in which case the SOOW (hard service, oil and water resistant) would be the better choice with it's thicker 600V insulation (and larger price tag).
    Last edited by tkanzler; 03-29-2011 at 02:16 PM.

  13. #13
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    Re: plug and circuit question

    I was thinking of following the tutorial on this site for the 240 volt extension cord but making the adjustments to fit my situation.

    I'm still not grasping the 4 prong vs 3 prong wire configuration yet. I'll cross that bridge when I get to it. I'm in the office right now so I can't check to see what the dryer setup is.

    Really good news that the dryer consumes more power than the welder though.

    Thanks again

  14. #14
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    Re: plug and circuit question

    Good news again. 3 prong dryer outlet. It looks like the ground is L shaped and the other two are flat blades.

  15. #15
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    Re: plug and circuit question

    It wouldn't matter either way (3 or 4 blade), but since you have a NEMA 10-30 receptacle (3-pole, 3-wire, 125/250V, non-grounding), just connect black and white to the two straight blades (X and Y), and the green to the L-shaped neutral blade (W). At the other end, connect the black and white to X and Y, and the green to the G pin (half-round), assuming you're using a NEMA 6-30 or 6-50 receptacle (2-pole, 3-wire, 250V, grounding).

    Or, if the welder doesn't even have a cord, just put the long cord on it, and save yourself some money on extra receptacles and plugs.

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    Re: plug and circuit question

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    That's what I'm working with.

    The welder doesn't have a plug and the cord is supposed to be #12. I was thinking of cutting a #10 extension cord or finding suitable wire from an electrical supply, and wiring it directly to the machine. Then attaching the NEMA 10-30 plug.

    Are you suggesting that I rewire the existing receptacle?

    I was hoping I could just wire everything up and plug it to the receptacle.

  17. #17
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    Re: plug and circuit question

    No. I thought (mistakenly) that your welder had a cord and 6-30 or 6-50 plug. Since it doesn't, I'd just put a long cord on it, with a 10-30 plug (fits your 10-30 receptacle), and call it good. It's the cheapest way to do this, and if you ever move, you could shorten it to suit, if you felt so inclined.

    But with a #10 cord, voltage drop in the cord is not going to be an issue. It'll be about 2.7V dropped in the cord at 21A, which is only 1.1% at 240V. No worries. Even a #12 is only 1.8% at 240V, which is also no worries, but I don't know if the lugs of the plug are rated for #12, and the jacket might be too small to be clamped by the plug housing as intended. You should check that out before buying the cord.

  18. #18
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    Re: plug and circuit question

    OK cool. Thanks for all of your help. I really appreciate it.

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