Can I wire a box with two 120-volt duplex outlets each wired to one leg of a 240-volt 3-wire plug?

Question

In my shop I have plenty of NEMA 6-20Rs (240-volt, 20-amp receptacles) and not enough NEMA 5-20Rs (120-volt 20-amp receptacles). These are all right next to the panel.

My goal or my desire: I want to run a 20-foot 10/3 power cord to a two duplex box attached to a work table to run simple motors and perhaps a work light. I want one duplex outlet to be on one 120-volt leg of the 240/20 and the other duplex outlet on the other leg.

Question: Can I use the neutral as a ground or should I use 10/4 for a separate ground?

Answer 1

Your question should be "can I use ground as neutral" since your 6-20 has only 2 hots and ground, no neutral. It is a against code and potentially dangerous to use a ground in place of a neutral.

You need to pull a separate neutral wire back to the panel or sub panel. If you want to keep 240V available, install an L14-20 outlet and use an adapter off of that.

Answer 2

You cannot abuse ground as neutral in any way, shape or form. Neutral is not ground.

The linchpin issue is that you don't have the right receptacles in place. If you are clever enough to think of this scheme, you are clever enough to run some proper neutral wire and fit the right receptacles where you need them. I do that whenever I need a receptacle somewhere. If you're in conduit, it's easy; otherwise if the shop area isn't drywalled up, you'll have no trouble replacing the 12/2 Romex with 12/3.

You will note on a subpanel that neutrals and grounds are on separate buses. For good reason; neutral is not ground.

I don't object to the idea of fitting a NEMA 14-20 then having a pendant to a workbench which presents two sets of NEMA 5-20s to the user, just as you propose except with a proper neutral. This is called a multi-wire branch circuit. I have seen shops dangle the pendant from the ceiling with proper strain reliefs. It would be a very good idea if those were GFCI, preferably back at the panel with a 2-pole GFCI breaker.