3

I'll start by acknowledging that I know this violates NEC. As I understand it, the reason that a 20 amp outlet can't be connected to a 15 amp circuit is that someone could potentially connect a 20 amp device, overload the circuit, and cause a fire. That makes sense.

Now, here's the question. Suppose all you have on hand is a 20 amp GFCI and you need to replace an outlet on a 15 amp circuit. (You will get a correct 15 amp outlet eventually, but you don't have it right now.) This circuit is on your own, private property - no one else will use it but you. You also don't own any 20 amp devices, so there is zero chance of one being connected to the circuit. (For sake of discussion, exclude situations like forgetting you did this, contractors using the circuit, sale of the property to an unaware party, etc. I acknowledge those are more good reasons for the NEC rule.)

Does connecting the 20 amp GFCI to the 15 amp circuit pose a danger just by its existence? That is, will it pose some risk just by being connected to the circuit, even if unused, or only used for 15 amp devices? Or, is it only potentially dangerous, because someone could connect something to it that they shouldn't?

Improve this question
2
  • You're chasing a fantasy, as detailed in the answers you've already gotten. And I can safely say that as a person who runs basically all outlet circuits at 20A, the only items I've ever used with a 20A plug on them were ones that I myself had put that plug on. So I rarely bother with 20A receptacles OTHER than the 20A GFCI's on those circuits.
    – Ecnerwal
    Commented Oct 21, 2020 at 21:16
  • 4
    STOP. Does the GFCI device actually have an obvious T-shaped neutral pin? Or do you think it's 20A only because its labeling and documentation says something about that?
    – Harper - Reinstate Monica
    Commented Oct 22, 2020 at 0:39

4 Answers 4

Reset to default
5

First off, connecting a 20 Amp load to a 15 Amp circuit will overload the circuit but shouldn't cause a fire because the 15 Amp breaker will trip.

A 20 amp GFCI doesn't pose any threat just by being there. The threat comes from people thinking it's on a 20 amp circuit and loading it as such.... which will trip a 15 Amp breaker.

Improve this answer
3
  • 3
    As I understood it, you shouldn't count on a breaker. 20 amps may trip a 15 amp breaker, but it could take a long time, whereas 200 amps would trip it very quickly.
    – SouthShoreAK
    Commented Oct 21, 2020 at 20:34
  • 3
    @SouthShoreAK We've got 328 million people depending on breakers, and fuses, to do their job so I think it's safe to count on them. Plus, #14 awg is actually good for 20 Amps.... but you're only allowed to protect it for 15 Amps. Plus, 20 Amps would trip a 15 Amp breaker fairly fast if a constant load.
    – JACK
    Commented Oct 21, 2020 at 21:02
  • You said it yourself: if you don't plug a 20A device into it because you don't own one, there is no potential danger. The ONLY possible hazard is in "someone" plugging in a device that actually draws more than 15A continuously. And most likely, the breaker will trip and prevent a fire. I bought a bunch of 20A duplex receptacles at a garage sale years ago for 10 cents each, I used them in making up my own extension cords. The plug end of the cord is 15A, so I can't plug it into a 20A circuit anyway, but in theory I could plug in a 20A device to the box. I just know not to...
    – JRaef
    Commented Oct 21, 2020 at 21:47
6

Let's look at it a slightly different way:

  • Which is more dangerous, a 20 Amp GFCI on a 15 Amp circuit, or a 15 Amp non-GFCI on a 15 Amp circuit that should have GFCI, such as a kitchen or bathroom receptacle?

I would argue that given those two choices, the risk of using the 20 Amp GFCI (an edge case of 20 Amp device overloading 14 AWG wire and causing a problem before the 15 Amp breaker trips) is very, very low. But the risk of using the 15 Amp (i.e., matched exactly) non-GFCI in a place where water hazards exist that can be made safe by using GFCI is huge.

Improve this answer
1
  • 4
    On the other hand, a quick trip to town will enable you to buy the right sized circuit breaker and not worry about it any more.
    – Marvinlee
    Commented Oct 9, 2022 at 17:23
-2

It it correct, no. But...I wouldn't lose any sleep over it. If you have glass fuses or knob&tube I would be concerned.

The 20amp GFCI doesn't override your 15amp breaker. So the breaker will trip when it's rating is reached.

Improve this answer
3
  • You may want to reread and edit this to be an answer. There are too many typos for this to make much sense.
    – FreeMan
    Commented Oct 10, 2022 at 0:16
  • This doesn't really add any new information to the answers already provided.
    – JACK
    Commented Oct 10, 2022 at 1:06
  • Note that in many jurisdictions, installing a 20 amp outlet on a 15 amp circuit violates code.
    – Michael Mior
    Commented Oct 24, 2022 at 17:29
-3

The answer is YES and NO.

Section 210.8 of NEC only states where GFCI breakers or outlets must be installed in a building.(Breaker with built-in GFCI doesn't count as outlet or receptacle.) A GFCI can help prevent electrocution. If a person’s body starts to receive a shock, the GFCI senses this and cuts off the power before he/she can get injured. A GFCI is not a fuse and it doesn't react to overload circuit.

However, if a GFCI is an outlet, it must follow NEC's outlet rules. If a 120V outlet has a T-slot, it's a 20A one and can be used on 20A circuit only. If the older 20A CFGI doesn't have T-slot, it can be used on 15A or 20A circuit.

Improve this answer
3
  • This simply restates the code violations that the OP knew about 3 years ago, but doesn't address the actual question of "does it inherently pose a danger?"
    – FreeMan
    Commented Oct 1, 2023 at 11:36
  • Question was about Article 210 Part II, not Part I. Also, it's not accurate to say a GFCI senses shocks.
    – Robert Chapin
    Commented Oct 1, 2023 at 15:08
  • Also review definitions of outlet and receptacle. A light fixture or other hard wired device is considered an outlet, and are not required by 210.8 to have GFCI protection.
    – NoSparksPlease
    Commented Oct 1, 2023 at 15:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.