This post extends from the emailed mike holt NEC questions for the day. Referring to code section 210.21, specifically table 210.21(B)(3). This does not make sence. If I am reading it correctly, it is saying you can not put a 20A duplex receptacle on a circuit protected by a 15A breaker. I do not see the harm in it. Even if you plug in a 20A load, the 15A OCPD will protect the circuit from overload. You should be able to connect any receptacle to a 15A circuit even if it is say rated for 50A. I find this to be stranger than allowing a receptacle rated for 15A to be allowed on a 20A circuit. I know, there can't be a load exceeding 15A plugged into a 15A receptacle.