My device calls for 12A and 220V, but comes with no plug attached. The suggestion is to use a NEMA 6-15p plug. I decided to run 12/2 Romex and upgrade the breaker to 20A. This should be no different than running a single pole 20A breaker and 12/2 when 15A are enough, but the double pole is causing me to doubt things a little. Am I going to be OK running my device on a 20A breaker using a NEMA 6-15p and a NEMA 6-20r?


3 Answers 3



You know how you go into a modern kitchen, and those are 20A circuits serving the countertop receptacles. But you look, and the socket are 15A sockets. Why is that?

Because, there is an exception in NEC that allows 15A sockets on 20A circuits as long as there are two or more sockets. And obviously, any random receptacle contains 2 sockets, so you're all set on that rule.

enter image description here

What you cannot do

is mismatch breaker to socket when there is only 1 socket on the circuit. So if you're using one of these simplex critters

Leviton 6-15 single receptacle

So a 15A simplex outlet is not legal as the only outlet on a 20A circuit. It would be fine if the circuit had 2 of these on it; that would be 2 sockets!

So you have several escapes.

  • Change the 6-15 outlet to a duplex 6-15 with 2 sockets as in the top picture.
  • Add a second socket to the circuit anywhere. Might I suggest the garage?*
  • Change the simplex 6-15 to a simplex 6-20.
  • Change the breaker to 15A. The wire can remain #12, you're always allowed to go larger on the wire.

* Houses get better offers when they're EV charging ready, and 240V/20A is perfectly usable level 2 charging, giving 100-150 miles per 10 hour "evening" - more if charged longer obviously. People who need more than that don't generally buy EVs.

  • Thanks - I ran these new lines from the garage direct to the panel for woodworking equipment. This will be the only socket on the circuit so thanks for making that distinction. I will change the plug and receptacle to 6-20 - thanks so much.
    – Garet Jax
    Mar 24, 2023 at 13:15

It's no different for 6-15 and 6-20 than for 5-15 and 5-20, barring manufacturer instruction specifying a maximum of 15A (given there's no supplied plug. If they supplied a 6-15 plug, that plugs into a 6-20 or a 6-15, so it has to handle either if supplied that way.)

So if the receptacle is simplex, the receptacle has to match the breaker. If the receptacle is duplex, it can be a 6-15 duplex receptacle on a 20A 240V circuit. If the receptacle is a 6-20 it has to be on a 20A breaker.

There's no particular benefit to upsizing the circuit if the only thing used on it will be the 12A device, for which a 15A circuit is already sufficiently upsized.

  • The benefit of a 20A circuit and 6-20 instead of 15A and 6-15 is that future things (tools, EV charging, etc.) can be 1/3 more powerful, at very little additional up-front cost. Mar 23, 2023 at 21:48

I think you need to use 6-20 since this is single use circuit(240v) if you use a 20 amp breaker.

I believe only 5-15 can be use on 120v 20 amp circuits if more than one receptacle on that circuit.

12/2 is okay since no neutral is needed, but mark the white wire with black or red colours, since it will be used for hot also. You connect the white to the second pole of the breaker.

This is if your device instructions say to use a 20 amp breaker. If the device says to use 15 amp breaker then you must use 6-15, but can still use the 12/2 cable or can use 14/2 cable(only on 15 amp breaker).

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