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I've searched for 3 weeks looking for a simple answer. warning after warning about how dangerous this is. Still no answer.

  1. I have a generator that uses a 4 prong 30 amp 230v female plug.

  2. I am only using it to test machinery and 230v tools. It will NEVER be hooked up to a home nor used to hurt anyone. (Yes I have to state this because of special humans that reside here).

  3. All of the machinery and tools that I am testing have 3 wires.

  4. How would I wire the 4 prong in order to have 3 wires that I can connect and disconnect when testing.

Thanks for the help and the constant reminder of safety from certain individuals. You are always needed. ❤

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  • 1
    The equipment being tested... does it have a cord and plug? Or is it provided with terminals that the end user attaches the 230V to? Mar 17, 2022 at 21:14
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    3 wire might mean hot, hot, ground for 240volts, or hot, neutral, ground for 120 volts. Are all the machinery have 10-30 plugs or are they different types?
    – crip659
    Mar 17, 2022 at 21:17
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    We'd probably need to know the voltage of the devices you are trying to test, and whether, if they are 230/240 volt devices, are they North American or European. Also the number of wires of the device is not sufficient to show a wiring suggestion. A 240 volt device with ground can be three wires, so can a 120 volt device. A three-wire 240V North American device will have two power wires plus ground, but a three-wire 240V European device will have one power wire, plus return and ground. Each has different connection requirements. Please edit the question to add details like these. Mar 17, 2022 at 21:19
  • If the devices you are testing just need hot/hot/ground why don't you just put plugs on them that fit the socket on your generator? There's nothing to connect to the plug's neutral pin, that's fine. If you don't understand that, I don't think it's reasonable for you to ask this community to suspend their knowledge and instincts about how to do things safely. It's not safe to do this without some minimum level of knowledge, that you don't seem to have.
    – jay613
    Mar 18, 2022 at 13:51

1 Answer 1

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The first rule of power sources

Things which supply power must have female sockets, and things which draw power must have male plugs. The first corollary of that rule is that no cord may have male plugs on both ends. That is simply so the energy sources are always shielded (by virtue of the sockets being female). It's not any more complicated than that.

Now, what happens with a cord that is male plug at one end, and bare wires or lugs at the other? (e.g. typical dryer or range cord). Real simple: bolt it to the machine before you plug it into the wall.

Generally, if a person feels brutalized by incessant safety warnings from concerned citizens, it's because they have communicated loathing or alarming ignorance for the above rules or the electrical code generally. The best cure is to reduce the amount of "imagining rules" that you do, actively avoid sophomorism, and simply listen to best advice from the experienced.

Getting from "universal donor" NEMA 14-30 to 240V-only

The NEMA 14 series is the universal socket, because it provides neutral in case it is needed. What do you do if it isn't?

Really simple: you use a 3-wire cord that has a NEMA 14 male plug, and you don't hook neutral to any wire. The other end could be any of the following:

  • Lugs for attachment to a machine
  • A NEMA 6 family female socket
  • a BS1363 female socket
  • a CEE 6/3 female socket
  • Etc. as meets your requirements

Now you have an "adapter cable" you can use for North American testing of the equipment. It connects normally and safely, either to the generator or hardwired NEMA 14 socket wired into the electrical grid.

"Why build a cord? Why not use a 4-wire cord and leave neutral flapping in the breeze? It's harmless." No, it's not. Neutral is insulated for a reason - a variety of faults can energize netural at line potential (120V or 230V). Eliminate it altogether from the cord.

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