I'm trying to add a new GFCI outlet by splitting and using pigtails off an existing GFCI outlet. However, when I opened out the junction box I noticed that there are two sets of wires attached to the existing GFCI outlet.
Why is this set up this way?
Can I just take one of the set off and use that for my new outlet?
GFCI outlets have two sets of connectors: Line and Load.
The Line terminals receive power from the breaker/fuse box. The Load terminals carry power onto other outlet(s). These “downstream” outlets are also protected by this GFCI.
If you want to add a separate GFCI outlet, you’ll need to identify the wires connected to the Line terminals and connect the new wires there. Looking at the photos, it looks like you’re in luck: these are designed to accept two wires each. Otherwise, you’d need to pull out the wires and add pigtail wires to connect everything.
On the other hand, you could add another standard outlet and have it protected by this GFCI. To do this connect the new wires in parallel with the Load wires. Note that you must label the new outlet “GFCI protected”. I’d also suggest labeling it with the location of the GFCI.
To answer your last question, you wil need an additional cable to go to the new outlet.
You might look at cars and presume all cars are gasoline powered. No, "gasoline power" does not define cars and there are other options. Similarly, you might look at GFCIs and presume all GFCIs are "GFCI + receptacle combo devices". GFCIs come in many forms - GFCI+receptacle, GFCI+breaker, GFCI+switch, GFCI as switch, and GFCI only. They're even built into EV "chargers"! All of them provide the "downline protection" feature you just learned about.
On the vast majority of GFCIs, they use a splice feature called "Screw-and-clamp". This allows each screw to screw down and clamp up to 2 wires each. So on your setup, you can add an additional pair of wires to either the LINE side screws (if you do not want downline protection) or the LOAD side screws (if you do want downline protection).
Never put a GFCI in the downline protected area of another GFCI - resetting it after a trip will be very difficult and confusing.
Marking downline outlets is mandatory. You'll thank me later when the receptacle goes dead for no apparent reason and you find you can fix it easily instead of hiring a pro. You can use the ugly "GFCI Protected" stickers provided, or any other marking method which is not handwritten. I like P-touch or Brother labelmakers on a white cover plate.
Also, let's talk about a Code issue. Code requires that circuits which serve bathroom receptacles in the workspace area (i.e. bathroom counter etc. where one might plug in a hair dryer) -- circuits which serve those must not serve anything else. To be more specific, for a circuit which serves bathroom workspace areas, either:
I wasn't clear where you were extending this circuit to, but if it's outside the bathroom, no go.
