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I'm installing a few new outlets in my unfinished basement and what I have currently is a 20 amp circuit and I have a 20 amp GFCI outlet hooked on to that. I'm looking to add another standard 15 amp outlet off the 20 amp GFCI.

I know you can do 15 amp outlets on a 20 amp circuit but what I'm wondering is it ok to have a 15 amp outlet along with a 20 amp outlet on the same 20 amp circuit as I would want the 20 amp GFCI outlet to provide protection to the 15 amp outlet.

Thanks

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    This answer might be helpful.
    – Tester101
    Nov 10, 2015 at 21:37
  • @Tester101 thanks, after reading that and a lot of the answer I'm still confused as It seems most are saying it's ok but some are saying not to do it, so I think I'll just go with a 20 amp outlet.
    – Greenhoe
    Nov 10, 2015 at 22:31

5 Answers 5

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This is legal and will work fine. But you do need to use #12 wire because the circuit is protected by the 20 amp breaker. (you can add more if needed.) I say this because the GFCI outlet is 1 device and the 15 A outlet is the 2nd. If there were only a single 15 amp outlet, it would not be code. But with 2 or more, it is ok. NEC 210-21.b1

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  • what do you mean by "and the 15A outlet is the 2nd if there were only 1, 15 amp outlet it would not be code but with 2 or more it is ok." ?
    – Kris
    Nov 10, 2015 at 21:54
  • Your text states a gfci 20A outlet used to protect a 15 amp outlet, if it was only 1 15 amp outlet on a 20A circuit this is not legal, but with 2 outlets on the 20 amp circuit 1 can be the GFCI outlet and the second one the 15 amp outlet
    – Ed Beal
    Nov 10, 2015 at 22:17
  • sorry I'm not the "OP", just trying to understand your answer, which unfortunately, I am still unable to. Perhaps if you cited the code violation that would help.
    – Kris
    Nov 10, 2015 at 22:28
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    @Kris, The answer here quotes the NEC. If you only have ONE receptacle on a 20A branch, it must be 20A rated. If you have two or more, it can be 15A rated. Note that a single duplex receptacle counts as two, so 15A is OK.
    – JPhi1618
    Nov 10, 2015 at 22:52
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    I down voted your answer because overall it was nonsensical to anyone unaware of the code article you where trying to cite. It is also lacking structure and syntax. A good bit of up votes are given just on that alone. Unfortunately, I still think it is needs improvement before I change my vote.
    – Kris
    Nov 11, 2015 at 2:43
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If a GFCI device is rated for 20 Amps, that just means that under normal use, it can take up to a 20 Amp load. The Ground Fault part of the GFCI is to detect and prevent a current (Amps), which is strong enough to severely injure a human, from going to ground. If you put a paperclip in the short prong side of an outlet, the GFCI should protect your life (but don't try it). A GFCI device is supposed to detect and interrupt a current as small as 6 mA. See here for more info about GFCIs.

The normal operating load of a GFCI device is always much, much greater than the fault detection part of the GFCI device. 15 or 20 Amps, makes no difference. Your 20 AMP GFCI will fully protect your 15 Amp outlet.

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    Edwin, your description and understanding of how a GFI works is wrong. The circuit ampacity and device capacity have NOTHING to do with how a GFI works. GFIs detect a current (amps) imbalance in the normal workings of the circuit.See the link you yourself posted for how GFIs work.
    – Speedy Petey
    Nov 11, 2015 at 12:33
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    @SpeedyPetey, I think you might be misreading my answer.
    – Edwin
    Nov 11, 2015 at 15:54
  • OK, how so?....
    – Speedy Petey
    Nov 11, 2015 at 16:09
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    @SpeedyPetey Because you seem to think that I said that "circuit ampacity and device capacity" had something to do with how a GFCI device works. I said the opposite: "15 or 20 Amps, makes no difference"
    – Edwin
    Nov 11, 2015 at 23:36
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Homeowner - I had a 15 amp outlet ( more than 1) connected to a 20 amp GFI, the 15 amp out burned up and still did not trip the 20 amp breaker, not a good idea to have the mix even if allowed, it could have burned more than the plastic outlet and wire...

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  • Welcome to SO-DIY, in lieu of personal experience, please cite codes, regulations, and/or other verifiable content to support your answer. While it is true that they should not do this, there are also legitimate documented reasons that specify "why" they should not.
    – tahwos
    Oct 6, 2019 at 17:02
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As user107621 indicates, it may not be the best idea, even if it is allowed by code. Granted the primary way this happens is by overloading the receptacle, but in receptacle-sparse rooms this becomes more likely because people will use taps and cheap power strips (with no or ineffective overcurrent protection) to plug in all the devices required of modern living.

That said, I rewired my living room to 2014 code (there were only 2 ungrounded outlets in a ~200sqft space, and they weren't even on the same breaker - idk how anyone puts up with that) and used a 20A breaker so I could reliably run a space heater without tripping the breaker, but used 15A tamper-proof receptacles because they were notably cheaper in a 10 pack than buying single 20A. But I also complied with the requirement to have a receptacle every 6ft of wall space (actually every 4ft where possible, because it happened to be simpler that way), which significantly reduces the chances of anyone deciding to do that.

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Assuming you use 12 gauge wire to the new outlet, the only significant problem would be the possibility of overloading the 15A outlet.

Suppose something something goes wrong with something plugged into it and it starts drawing 18A. Normally this would trip the panel breaker, but in this case the panel breaker and the GFCI both think it is fine, and the wiring can handle it, so the situation will continue uninterrupted.

The 15A outlet itself is now carrying 18A, and in theory could overheat, melt, burn, etc.

Wouldn't everything be simpler and more obvious if the new outlet were also rated at 20A?

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