I have a hypothetical question:
If you have a 15 Amp breaker connected to a 20 Amp T type outlet with (20 Amp) 12 AWG wire, is it within code, below code, or above code, where code means the National Electrical Code.
This is due to a discussion I had with a colleague that insists it is not within code due to the 20 Amp T outlet. I view it as the outlet may be 20 Amp and any appliance you plug into it that draws more than the 15 Amp breaker will support will trip the breaker long before any overheating or electrical damage will occur.
Now I will agree that having a 15 Amp breaker and using 14 AWG wire with a 20 Amp T type outlet could potentially overheat the wiring, as the draw could be just over the 15 Amp breaker which they tend to trip around 16 Amps.
Best Answer
The answer to this question can be found in article 210 of the National Electrical Code (NEC). Section 210.3 of this article, tells us that the circuit rating shall be determined by the overcurrent device rating.
So if you have a 15A breaker, the circuit rating is 15 Amps. Section 210.21(B)(3), tells us to refer to table 210.21(B)(3) to determine the receptacle rating for circuits supplying two or more receptacles.
This tells us that if we have a 15A circuit breaker protecting a circuit with two or more receptacles, each receptacle on the circuit must be rated not over 15 amperes. It's also good to remember, that the NEC does not view a duplex receptacle as a single receptacle according to the definition of a receptacle.
So if you're installing even a single duplex receptacle on the circuit, you'll need to follow 210.21(B)(3) and use a 15A receptacle.