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
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
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...
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.
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.
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?
