Can a 15 amp rated duplex outlet be used in a circuit fed by 12 AWG wire through a 20 AMP breaker, or are only 20 amp rated receptacles allowed?

You can use 15 Amp recepticles and switches on a 20 Amp circuit. Does seem strange.

For some reason in Canada you must use 20A receptacles.

In the US as long as it is at least one duplex or two or more simplex receptacles 15A are fine.

I got one and asked the installer why, that's what he had in the truck. Its OK but a waste of versatility.

I may be off here...

But I always thought that this was allowed, however you can not use a 20 AMP receptical in a 15 amp circuit.

After all, an appliance that only draws 10 amps (and uses a 15 AMP plug) would be perfectly safe on a 20 AMP circuit.

However, if you change the cord of an appliance that draws 16 or so amps, and install a 15 amp plug on the cord, then you are going to run into overloads.

Few houseshold appliances would require a dedicated 20 AMP circuit, a large window AC is the only thing that comes to mind right now.