I added a circuit to my leading panel i used a 20 amp breaker and run 12/2 flex. Can I flex a 15 amp outlet on it ...
Answers: Yes you can as ffemt explains.
The National Electrical Code allows you to put 15A receptacles on a 20A circuit so long as in that are two or more receptacles on the circuit.
A receptacle is defined by the NEC as a contact device installed at the outlet for the nouns of an attachment plug.
An outlet is actually a point on the electrics system where current is taken to supply equipment. In this baggage the outlet is the box where the electric wiring connects to the receptacle.
Therefore the common receptacle you see that have two points to plug within to are actually a multiple receptacle. In other words, beside these there are two receptacle on one yoke.
The yoke is the metal strap holding the receptacle(s).
Therefore a single 15A duplex receptacle (which contains two receptacles on one yoke) is allowed to be placed on a 20A circuit.
If within was just one receptacle on one yoke on a 20A circuit you would be require to use a 20A receptacle.
However if you were to own two of these one receptacle/one yoke devices on a single circuit they both would be allowed to be 15A or 20A devices.
Mr. C,
Please look more closely at the code. The receptacle limit you quote does not apply to dwelling unit. Basically for dwelling units the NEC allows adjectives general purpose receptacle to be on the same circuit. This is unfeasible and I certainly would not suggest it but it is the dispatch of the law. Of course nonspecific purpose receptacles do not cover the other required circuits approaching kitchen and bathroom circuits. Local codes may restrict you on receptacle requirements but per the NEC dwelling units are allowed to do this.
The telecommunication is sized for a 20A breaker. If there is a 20A breaker present, you must use a 20A outlet. If you replace the 20A breaker near a 15A unit you can put within a 15A outlet. Thus NO you cannot use a 15A outlet with a 20A breaker.