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4 Post Dryer Plug Wiring

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  • 4 Post Dryer Plug Wiring

    I've got a Millermatic 175 mig welder which I'm trying to wire to my 4 post Dryer outlet. I'm using a 25' 10/3 extension cable. The dryer outlet consists of 4 posts..........two flat spade terminals side by side, a round terminal on top, and an "L" shaped terminal on the bottom (I believe it's a 30 amp). My 175 plug has a small spade teminal on the left, a larger spade terminal on the right, and a round terminal at the top. The 10/3 cable has a green, white, and black. I was hoping someone here on the forum could help as far as the wiring goes.

    Thanks in advance.

  • #2
    Correction to the post above, the cable is 8/3, not 10/3.

    Comment


    • #3
      New receptacle.....

      The receptacle that fits your MM175 is a NEMA 6-50 (nicknamed Welder outlet) which can be had at Lowe's/Home Depot or the like. It slightly resembles a regular 120V outlet. The hot wires attach to the outside lugs and the gound wire to the round lug. The 4-wire dryer receptacle (probably) has a black and a red (hot wires), a white (neutral) and a green (ground). The white neutral does not get connected to the new 6-50 receptacle. Leave it capped off inside the box.

      Hope this helps.

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      • #4
        Yes, I already have both receptacles which I got from Lowe's. So black and white to both hots, and green to ground, neutral not used.

        That'll do it!!

        Thanks!

        Comment


        • #5
          Originally posted by JCTX View Post
          Yes, I already have both receptacles which I got from Lowe's. So black and white to both hots, and green to ground, neutral not used.

          That'll do it!!

          Thanks!

          NO!

          Black, RED and Ground Do not connect the white-

          ahh I see you are making an extension cord- So yes
          Last edited by Broccoli1; 01-09-2008, 12:51 PM.

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          • #6
            I was allways told that you never change out the wall plug only change pigtails to match the wall plug. The 4 prong has 2 hot 1 ground 1 netural which is the new code. The three plug has 2 hot and 1 ground-netural. Three prong netural and ground sre the same.

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            • #7
              Originally posted by Woodshed View Post
              I was allways told that you never change out the wall plug only change pigtails to match the wall plug. The 4 prong has 2 hot 1 ground 1 netural which is the new code. The three plug has 2 hot and 1 ground-netural. Three prong netural and ground sre the same.
              Yeah, that's what I did. I needed an extension to go from the dryer plug out to my garage. I bought both the 3-terminal welder side receptacle, and the 4-terminal male plug from Lowe's. Both made by Cooper. (using a 25' 8/3 cable) Following triggerman's advice, I connected the green to the lower center "L" shaped terminal, (ground) and the black and white to the side spade terminals (hot). I left out the round neutral terminal. Got it all wired up and fired the 175 and it's working perfectly. It's been about a year and a half since I've done any welding so gonna get some practice in...

              Thanks again.

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              • #8
                What exactly is the purpose of the nuetral anyways?

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                • #9
                  Neutral

                  The voltage from hot to hot is 240V. From either hot to neutral is 120V. The green ground wire should NEVER, NEVER, NEVER EVER be wired to carry current during normal conditions. The neutral is a return path for the current coming down the hot leg to get back to the wall, breaker box and, ultimately, the power plant.

                  Hope this helps.

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                  • #10
                    The neutral is for appliances that have 120v controls, as most modern appliances do now. You need a neutral and one leg of 240v for 120.

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                    • #11
                      Ok, I see now thanks.

                      Comment


                      • #12
                        Pigtail

                        Hello,

                        just wondering, from all other threads I've read,
                        it seems it says the round pin on the male plug is your ground, not the L shaped one, (the L one is the neutral)

                        if i'm wrong, I hope someone corrects me.

                        thanks

                        Comment


                        • #13
                          You're right. THe round or "D" shaped prong is the ground which is wired to the green or bare wire. THe "L" shaped prong on the bottom is the neutral which is wired to the white. The neutral is code now to allow dryer manufacturers to elimnate having to put transformers in the dryers to step down to 120V to run the electronic circuits in the dryer. As mentioned before, the ground is not a normal current carrying conductor whereas the neutral is expected to carry current. In fact, wiring the ground to neutral or neutral to ground can cause you to get shocked by touching any grounded appliance as this would put a 120V potential on the ground circuit which is wired to the external case of every UL listed appliance.

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                          • #14
                            The round "D" shaped pin of the NEMA 14-30 plug is GROUND

                            The L shaped pin is NEUTRAL.

                            Do not connect anything to the L shaped pin when wiring a pigtail!

                            BTW, 8 ga wire is extraordinary overkill. This welder will be running around 20 amps at low duty cycle. 12 ga is more than adequate, unless your extension cord is 100 or more feet long, in which case you may consider 10 ga to minimize voltage drop.

                            And no, wiring the neutral to ground will not cause 120V to be present on the chassis of the appliance. It will cause maybe 5 VAC (give or take a few) to be present at high loads. The only way 120V would be present is if the ground was cut in the box.

                            But you will feel 5 VAC and under certain circumstances it can kill, especially the elderly and those predisposed to certain cardiac arrhythmia.
                            Last edited by Bodybagger; 03-30-2010, 05:34 PM.

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