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I have a 60amp 220v run from a sub-panel. The run is a four wire run (2 hots, 1 neutral, 1 ground). The appliances are an air compressor and a welder. The compressor only requires a 3 wire setup because of it’s magnetic motor. The welder will use 4 wires. I’d like to setup the wiring on both appliances with a plug on each so that I can connect one at a time to a receptacle as needed.

For the compressor, I’d get a 3 wire plug and for the welder, I’d get a 4 wire plug. With that said, how do I setup a receptacle that has a 4 wire run to accommodate both a 3 wire plug and a 4 wire plug at a time?

Any thoughts on what I can do here without running a separate run for each appliance?

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    What are the input amp ratings on the welder and compressor?
    – Ecnerwal
    May 9 '20 at 13:37
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    Yes, what are the amp ratings of the appliances? Also, I take it this is in a shop space of some sort, no? May 9 '20 at 13:39
  • The amp ratings are 40 for the compressor and 50 for the welder May 9 '20 at 20:33
  • And yep, this is a shop in my yard I have May 9 '20 at 20:38
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In a code free world, you would need a 4 wire receptacle and two plugs to match. You'd wire the welder with four wires as needed and wire the compressor with the three wires in the other plug and not connect the terminal for the fourth wire. I don't think you can't do this. You shouldn't jury rig plugs and outlets like this. The other major problem is the 60 amp breaker. If either one of your pieces of equipment failed, they burn up before your 60 amp breaker tripped. They would literally have no protection. Do this right and run two circuits, protecting them individually. If this run is in conduit, running two circuits would not be that difficult.

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    I'm not certain that code forbids using a 4-wire plug on a device that makes no use of the neutral - the OTHER direction is clearly forbidden. But the amperage ratings of the devices are as yet unknown, and you may well be right on that point.
    – Ecnerwal
    May 9 '20 at 13:39
  • @Ecnerwal Noted and changed wording.
    – JACK
    May 9 '20 at 13:50
  • So the compressor is 40 amps but peaks close to 60 at startup. The same with the welder except it operates at 50amps May 9 '20 at 20:37
  • So any concerns with the 60 amp breaker and trying this method? May 10 '20 at 17:48
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    @TitoValentin Breakers are not sized for startup currents so you'll still have little protection.
    – JACK
    May 11 '20 at 19:59

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