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230v wiring question

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  • 230v wiring question

    I'm thinking about buying a 230v Miller welder... the new DVIj-2 dual voltage unit. I've done quite a bit of residential wiring but saw a comment recently in another forum that confuses me. The person said that a dryer circuit requires a "hot/hot/neutral" circuit.... but welders need a "hot/hot/ground" circuit. I've never wired anything and omitted the neutral connection... someone please help me here... thanx

  • #2
    All circuits have a ground. Any appliance that is 220v only needs 2 hots, one from each phase. That would be 3 wires: 2 hots and a ground.

    If an appliance requires both 110v and 220v, like some ranges for example, which use the 110v for timers, lights etc., it will have 4 wires, 2 hots, a neutral and a ground. The appliance then uses 1 phase and the neutral for the internal 110v circuit.

    In some installations, you may open a receptacle like the dryer and find that it shows 2 hots, one to each slotted prong opening and a white "neutral" to the center rounded hole. That really is not 2 hots and a neutral, it is 2 hots with a neutral being used as a ground - hopefully.

    So what is the difference? Well, if the wire goes directly back to the distribution panel and connects to the ground bus, it is in fact a ground. If the wire goes back to the panel and connects to the neutral bus, then it is a neutral. But if the panel neutral is BONDED to the panel (ground), then the neutral and the ground at that point are common.

    This is often a point of confusion. In a simple installation, the panel neutral is bonded to the case, i.e. the ground. If you have a disconnect, either a main breaker outside the distribution panel or a disconnect remote from the distribution panel, then that device is grounded and the distribution panel has one bus connected to that ground and the other as strictly a neutral.

    If the white wire from the receptacle in question, is connected at some point with other neutrals or outlet neutrals, then the wire may be under-rated for the whole cummulative load and will at the least transfer noise to the other circuits tied in.

    You can check the distribution panel for the green screw usually located on one side of the neutral bus or the other. It should be labeled on the cabinet as "grounding screw" or similar. If this is in place and tight (because it can be in place and not touching the cabinet below) then your neutral is bonded to ground. Then running to the neutral bus is the same as running to ground. Regardless, the wire should be of appropriate gauge for the load and come directly from the receptacle to the bus for high load, high noise installations.

    Most important is to check the condition and gauge of the wires when hooking into an existing circuit. Remember the WIRE size determines the size of the breaker you use. If you need more amps than the wire allows you need to upgrade the wire.

    Hope this helps... Good luck and start burning some steel!

    Last edited by Handy560; 03-04-2008, 09:13 AM.


    • #3

      man what a class i didnt learn that much in two years thanks


      • #4
        Originally posted by Handy560 View Post
        All circuits have a ground. Any appliance that is 220v only needs 2 hots, one from each phase............ John
        There is only one phase. The "hots" come from each end of the transformer winding on the pole (or wherever it is).

        Other than that, I can't add much other than some nomenclature. The 4- wire dryer outlet (code in today's world) is a NEMA 14-30R. 240V welders have NEMA 6-50P's on the cords when supplied.

        The part about the neutral/ground bond is true if the outlet in question is being fed from the main service panel or a sub panel in the same building as the main service panel.

        If your shop is in a detached building, be carefull. The neutral and the equipment ground (green wire) are isolated. In this case, although the neutral is still connected to the driven grounding system, this is not the equipment ground bus! There will be a separate equipment ground terminal bolted to the inside of the remote panel's case, which will be connected to the main service via it's own green feed wire.



        • #5
          Maybe I missed it, but what was the answer to the question about whether the welder should be using the ground or the neutral wire? That is, which wire should go to the round center prong on the NEMA 6-50P/R?


          • #6
            Originally posted by root View Post
            Maybe I missed it, but what was the answer to the question about whether the welder should be using the ground or the neutral wire? That is, which wire should go to the round center prong on the NEMA 6-50P/R?
            It is the ground (green) wire, but the rest of the dialogue describes what is up in an old 3-wire dryer circuit that does not have a green ground, but rather a white neutral.

            In the same building as the service panel, the green and white are bonded, so the neutral can act as the equipment ground, too.



            • #7

              Thanks for being more clear Hank. You are correct. It is single phase wiring. Unfortunately, I fell victim to a habit. Because all we work with is single phase, we (incorrectly) refer to each hot as a phase.

              My advice really was not to take for granted what is there. Check it out and if you are not sure, have someone who does check it out.

              I have seen so many half ****** installations that it is scary.

              Good luck,



              • #8
                ooops forgot...

                Just wanted to mention that here locally, Chicago area, any panel including subpanels after the first disconnect of any type are not bonded. If you have a pedastal with breakers outside, it is bonded and not the main panel, if the main breaker in the main panel is your disconnect then that panel is bonded, but no sub panel is bonded.

                Can be confusing as #ell.



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