UL tests 15 and 20 amp receptacles to the same standards. This is done because the NEC allows 15 amp patterns to be used on 20 amp circuits.
A 20 amp receptacle is tested, assuming a 20 amp circuit. A 30 amp pattern assumes a 30 amp load, etc. So it does matter that you use the right plug pattern for the circuit.
The NEC allows the exception for 15 amp pattern receptacles, because a 20 amp circuit with multiple outlets is, almost by definition, a convenience or general purpose circuit. There is really no way of knowing what loads will be applied, just a near-certainty that they will be numerous, and much less than the rating of the circuit.
The same reasoning cannot apply to a circuit dedicated to a specific appliance. In that circumstance, the circuit - as a whole, and not just the plug pattern- is based upon the specific needs of the appliance.
Re: 15Amp GFCI on 20Amp Circuit?#71974 11/12/0603:14 PM11/12/0603:14 PM
The thing to keep in mind is that a listed 15 amp receptacle is designed and tested to be used on a 20 amp circuit.
I'd bet that there must be at least some makes of 15A receptacles which are manufactured with exactly the same T-slot contact as the 20A version but are just assembled with a different plastic front (with only parallel slots).
Has anyone stripped apart any to confirm this?
Re: 15Amp GFCI on 20Amp Circuit?#71975 11/12/0603:19 PM11/12/0603:19 PM
Personally I dont see why the 20 amp overcurrent is permitted on the 15 amp configuration receptacle. Some homeowner is going to plug their 16 gage extension cord into it, and load it up with who knows what, until it can pull 16 amps continuously and more than that intermittently, with no breaker tripping. Sure your receptacle is rated for the load but who knows what happens downstream.
Re: 15Amp GFCI on 20Amp Circuit?#71977 11/17/0606:01 PM11/17/0606:01 PM
Since the nominal 15 or 20amp protection does not protect against using a lamp cord that is not rated for the load it is carrying, that point seems to be moot.
TheKid: What the 15 amp receptacle configuration does for you is to protect the circuit from connection of a (properly wired) appliance of greater than 15 amps being connected, since the plug doesn't fit. So if you have a circuit wired at 20 amps and limit connection to 15 amps, there shouldn't be a problem.
The T-slot in the 20 amp receptacle allows you to plug in your 1 amp appliance with a 15 amp plug into either receptacle.
Re: 15Amp GFCI on 20Amp Circuit?#71979 11/19/0609:14 PM11/19/0609:14 PM
Pauluk: Specifically yes to your question. If you break apart a residential grade recep.,either 15 or 20 A, you will find the same stampings, they just use a different piece of plastic on the face. And also, the Leviton 5320, pretty much the standard device around here, costs me 39 or 40 cents, the guts are exactly the same as a Decora receptacle, which sells for $ 1.68... If you open a commercial device, say a hubbell CR15, it has the same innards as a CR 20, just different plastic on the front. Go Figure
On the issue of GFI receps, there seems to be some kind of current sensing built into some that won't allow you to draw more than 15 A from the recep.,I have not done much of a scientifical double blinded by the light test, but several times I have tried to pull more than the 15A load and the unit tripped...
[This message has been edited by Almost Fried (edited 11-19-2006).]
Re: 15Amp GFCI on 20Amp Circuit?#71980 11/23/0604:01 AM11/23/0604:01 AM
iwire, the 20 amp receptacle should be polarized for 20 plugs and therefore the 15 amp 16 gage extension cord couldnt be plugged into it, so then it wouldnt be carrying the 16 amps or so that the 20 overcurrent would allow. By the way, I am here in Canada, so maybe there is some difference between our 20 amp receptacles and the US version. The use of 20 amp overcurrent on the 15 amp rated cord seems to go back to the screw in fuse days when homeowner, frustrated with the 15 amp fuse always blowing, installs a 30 amp screw in fuse to fix the problem.