Is 20 amp outlet on 30 amp circuit legal?

[Steve Schoene]

You should use the 20 amp breaker if you want to use a 20 amp outlet. NEC section 210.21(B) is the cited section that says the receptacle shall have an amp rating not less than that of the circuit. You can use 15 amp outlets on a multi-outlet 20 amp circuit, but that's spelled out specifically in that code section. No problem using a 20 amp breaker with 10 gauge wire.

[Prashun Patel]

Pigtailing puts the receptacle in parallel with the rest of the circuit instead of in series. If the receptacle is interrupted (but doesn't short), then the rest of the ckt remains operational. But, I'm not convinced that the receptacle itself is still protected from surges above its rating just by being in parallel.

[Brian Elfert]

It looks I need to go with a 20 amp breaker then. This is only going to be a single outlet on the circuit.

I am pretty sure I have a spare 20 or 30 amp double pole breaker. I'll just have to break down and buy a 20 amp breaker if I only have a 30 amp breaker.

[Tom Veatch]

... Can I put a 20 amp receptacle on a 30 amp circuit and be legal?

Haven't read the other responses yet, but the short answer is _NO_!!! If you want to use that circuit, install a 30amp receptacle and replace the plug on the compressor with the a 30amp plug.

The code folks would probably be concerned about the 5 or 6 feet of 20 amp cable from the compressor to the receptacle not being protected.

Code folks aren't concered with what's beyond the receptacle. They have no way of knowing or controlling what load the consumer plugs into the circuit. The breaker is there to protect the circuit, not what might be beyond the receptacle.

As far as the power cord is concerned, it only carries what the compressor is drawing and that sounds like a <20 amp load under non-fault conditions. Under fault conditions with a load >30 amps, the breaker should trip long before the power cord vaporizes.

The only problem you might see would be a fault condition that draws more than 20 amps which would not trip the breaker and less than 30 amps which would trip the breaker. That is a low probability situation, and I seriously doubt that the power cord would present a problem even should that occur. If it concerns you to the point of interfering with your sleep, replace the cord with a heavier gauge cord.