Originally Posted By: ddivito This post was automatically imported from our archived forum.
Do you think it is a problem?
I've begun to wonder about all those 15 amp receptacles on 20 amp branch circuits throughout many of the houses I inspect.
I have been thinking of the potential for overheating if too many high draw appliances are plugged into one outlet, sending the total over 15 amps but still not enough to trip the breaker.
Originally Posted By: Greg Fretwell This post was automatically imported from our archived forum.
“15 amp” receptacles are still rated for 20 amps feeding through. The only thing the 20a plug configuration does is insure one properly “plugged” equipment can’t exceed 12a on a 15a circuit (80%).
The code assumes the user can overload any circuit that has receptacles. That is the main reason for 240.4(D) (the 15a on 14ga cu, 20a on 12ga cu rule). The safety factor is built into that rule.
They further enforce the safety in individual equipment with an 80% rule on any cord and plug connected equipment that is based on the 240.4(D) ampacity. That still won't keep someone from plugging in more than the circuit will hold.
Originally Posted By: bbadger This post was automatically imported from our archived forum.
ddivito wrote:
But what happens to that 15amp receptacle if someone has 18 amps plugged into it?
Not possible unless the 18 amp load has a 15 amp plug on it.
First, understand that the typical duplex receptacle outlet is two outlets as far as the NEC is concerned.
Second, a 15 amp rated receptacle will not accept a 20 amp plug.
That being the case and assuming no one installed a 15 amp plug on a 18 amp heater it is imposable to connect more than 15 amps of load to a single 15 amp receptacle.
Because most times we use duplex receptacles we could plug in two 10 amp loads into one 15 amp duplex receptacle, that is not a problem, they are designed to take that.
The NEC specifically allows 15 or 20 amp multiple receptacles on 20 amp circuits. 
-- Bob Badger
Electrical Construction & Maintenance
Moderator at ECN
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Quote:
The NEC specifically allows 15 or 20 amp multiple receptacles on 20 amp circuits.
What Bob B is trying to say it that you are alright using 15 amp receptacles on 20 amp circuits, you just can not put one a single 15 amp receptacle on a 20 amp circuit.
Originally Posted By: bbadger This post was automatically imported from our archived forum.
jmyers wrote:
Quote:
The NEC specifically allows 15 or 20 amp multiple receptacles on 20 amp circuits.
What Bob B is trying to say it that you are alright using 15 amp receptacles on 20 amp circuits, you just can not put one a single 15 amp receptacle on a 20 amp circuit.