I had replaced the light switch in a bathroom with a GFCI combo outlet /switch so that a hair dryer can be used. The feed comes from the vanity light with a 12/3 wire into the switchbox, then continues out from there with a 12/2 to the other circuits. Because the feed comes from the vanity light, it cannot be protected by the GFCI. Right? I don't know if the vanity light has to be protected so it might not matter.
The vanity light doesn't need GFCI protection, but I would assume that the red wire of the feed cable, is the return to the light, and if so, you could protect it.
I take that back, it wouldn't work with the one neutral
What you most likely have is the 12/2 is "feeding" the light. The
12/3 is carrying a hot to the switch/GFCI and a neutral to the GFCI The red is switch leg coming back to the light.
No, when I seperated all the wires, I confirmed the 12/3 is the feed coming from the vanity light. I tried to connect the red return wire to the "load" side of the GFI, but it tripped immediately, which made sense since the vanity light's neutral is not GFI protected.
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