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Building an extension cord for a MM200.

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  • Building an extension cord for a MM200.

    I need to build a 20' extension cord for a MM200.
    It plugs into a wall (dryer) outlet that is 240/30A. (NEMA10-30)

    I have never built an extension cord before so any suggestions on materials to use and so on would be greatly appreciated.

  • #2
    Here's a few resources to get you started.

    http://www.hobartwelders.com/weldtal...ad.php?t=32862
    http://www.hobartwelders.com/weldtal...ad.php?t=32699
    http://www.hobartwelders.com/weldtal...ad.php?t=32507
    http://www.hobartwelders.com/weldtal...ad.php?t=32198
    http://www.hobartwelders.com/weldtal...ad.php?t=32142
    http://www.hobartwelders.com/weldtal...ad.php?t=32061

    Personally, I would (and DID) just buy a pre-made welder extension from one of the various suppliers out there. Nice flexible 8 gauge cable, molded on plug and receptacle, and you're ready to go. I paid about $65 for mine, not sure what they cost these days.
    Trailblazer 302 * Millermatic 212 * Syncrowave 180SD * X-Treme 12VS Feeder * Spoolmate 3035
    Thermal Dynamics Cutmaster 52 Plasma * Lincoln 175 MIG

    Victor Superrange II * Victor Journeyman

    Hobart HH 125EZ


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    • #3
      I'd be sure to use an 8 gauge cord as a minimum since you have a 250+ amp welder.
      Millermatic Passport Plus
      Millermatic 200

      Millermatic 350P with Python
      XMT 304 /w S-64 feeder and 12RC
      Dynasty 300 DX
      Victor O/A
      Premier Power Welder for my trail junk.

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      • #4
        Originally posted by crawler View Post
        I'd be sure to use an 8 gauge cord as a minimum since you have a 250+ amp welder.
        This is the part I'm not to clear about. I'm know electrician by any means.

        I used the calculator and plugged in, under input, 38A. Am I using the calculator correctly?

        The Calculator:http://www.jhlarson.com/ind_tables/v...c_wiresize.htm

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        • #5
          The Millermatic 200 instruction manual contains recommendations on conductor and breaker size.
          --- RJL ----------------------------------------------

          Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
          -------------------------

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          • #6
            For a 20' run, the calculator says that 12 gauge is plenty. It shows #12 will carry over 60 amps for that distance. That surprised me.

            Nice calculator by the way.

            Bob

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            • #7
              It depends on duty cycle. For this application a 10 wire would be sufficient. It can be done down a 12, no one will personally think thats a good idea (even though legal in some circumstances) an 8 wouldn't hurt anything but for home/hobby use especially for a 1 wire 1 gas setup the operator wouldn't ever know the difference, neither would the machine or the wire. Build it 5 ft longer while you are at it.
              http://www.facebook.com/cary.urka.urkafarms

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              • #8
                A 12 would run 60 for a while but it shouldnt be part of any circuit over 50A.
                http://www.facebook.com/cary.urka.urkafarms

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                • #9
                  I just went and double checked the wall outlet. (this house is a rental, I'm still getting familiar with it)
                  The outlet is 250V. I tried to test the actual voltage but it is to high for meter and pops the fuse.
                  Does this make much of a difference in the amperage draw by the machine which is rated at 38A/230V?

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                  • #10
                    Hey, you electrical gurus, isn't a NEMA 10-30 two hots and a neutral, no ground? Doesn't the welder need a ground? Is it OK to use a neutral for that in this particular case?

                    Sean, you sure you have that meter set right? You shouldn't be popping meter fuses measuring voltage. Do be careful!

                    Edit: Or is this the answer? NEMA 10 devices are a curious throwback to an earlier time. They are classified as 125/250 V non-grounding, yet they are usually used in a manner that effectively grounds the appliance, albeit not in a manner consistent with most modern practice.

                    As commonly used, 10-30 and 10-50 plugs have the frame of the appliance grounded through the neutral pin. This was a legal grounding method under the National Electrical Code for electric ranges and electric clothes dryers from the 1947 to the 1996 edition. Since North American dryers and ranges have certain parts (timers, lights, fans, etc.) that run on 120 V, this means that the wire used for grounding is also carrying current. Although this is contrary to modern grounding practice, such installations remain extremely common in the United States and are relatively safe, because the larger conductors used are less likely to be broken than the smaller conductors used in ordinary appliance cords.
                    Last edited by usmcpop; 01-13-2009, 04:10 PM.
                    --- RJL ----------------------------------------------

                    Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
                    -------------------------

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                    • #11
                      Originally posted by usmcpop View Post
                      Hey, you electrical gurus, isn't a NEMA 10-30 two hots and a neutral, no ground? Doesn't the welder need a ground? Is it OK to use a neutral for that in this particular case?

                      Sean, you sure you have that meter set right? You shouldn't be popping meter fuses measuring voltage. Do be careful!
                      Yep, its just a POS. It is only rated at 250V and has a 1A fuse. Works fine for 110 and automotive stuff.

                      This machine has always been run off of this type of circuit (250V/30A dryer) but before the machine sat next to the outlet. Now I need the machine on the opposite side of the garage, thus the extension cord.

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                      • #12
                        The dryer outlet is wired fine as we assume it goes back to the service main panel.
                        http://www.facebook.com/cary.urka.urkafarms

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