I hope there is an electrician on this forum who would know the answer to this. I am in the US and must have permits in my area and install per NEC.

This is new construction. Installing a fan/light unit over a shower. I ran 12-3 Romex to them. They are being fed from a load side of a GFCI circuit. They will be sharing the white neutral wire.

Are there any issues with shared neutral when you have a GFI? or must they have separate neutrals?

Any issues with the GFCI not functioning as designed doing it this way?

Any issues with the NEC codes?

Anything else I should know?

see picture of how I have it wired..... GFI-protected

  • Do you mean the fan and light will be sharing the neutral (hopefully) or neutrals will be shared between the load and line side (bad) ?
    – Jeffrey
    Commented Sep 19, 2019 at 16:58
  • no sir. i ran 1 red and 1 black to the hot side of the fan and light (as stated 12-3 cable). then they both share the neutral return. Normally this is never an issue. I was just concerned that the electronic in the GFCI would be "unhappy" if it sense the return load different. Commented Sep 19, 2019 at 22:31

2 Answers 2


Generally speaking, you don't want to have a fan/light - or more specifically, a light - on GFCI because if the GFCI trips due to something else on the circuit then you are in the dark. As I understand it (I am not an electrician, but I have seen other questions on this topic and I heard this from my own electrician years ago when he installed heat/fan/light for me in a bathroom), if the fixture is not above a tub or shower then it does not need GFCI. However, sometimes that is either necessary (no other reasonable location) or desired, and in such cases, yes you would connect it to the LOAD side of a GFCI receptacle.

The key is that all hots must go to the same place and all neutrals must go to the same place. Plus all hots and neutrals for any given use must be together in the same cable. In the case of a combination fan/light, that means one of two things:

  • Two separate pairs of hot neutral, each pair must be together and both pairs connect to the same LOAD side of the same GFCI receptacle.
  • Three wires - 2 hot, 1 neutral, all must be together and all connect to the same LOAD side of the same GFCI receptacle. This is your situation as described.

Of course, there will be switches in between. If you use 2 separate switches (so you can have fan or light or both) then your setup will actually be:

  • LOAD hot -> pigtail -> both switch hots (This could also be without a pigtail if the switch is a double switch with a common screw to use for hot)
  • LOAD neutral -> neutral on switch if you need it via a pigtail -> neutral (white) from fan/light
  • Switched Hot 1 -> hot 1 (typically black) from fan/light
  • Switched Hot 2 -> hot 2 (typically red) from fan/light

If your fan/light actually has two separate neutral connections, connect them both to the white wire of your 12/3 using a pigtail.

  • actually,,, you are incorrect. you MUST have a GFCI if your light or fan is above a shower stall. (NEC states any place where it is wet) and the instructions for the light or fan indicate it. furthermore, the inspector who looked at this confirmed this. Commented Sep 19, 2019 at 22:53
  • 2
    What I said was:if the fixture is not above a tub or shower then it does not need GFCI. If it is over a tub or shower then it DOES need GFCI. Commented Sep 19, 2019 at 23:01
  • There is no NEC code requiring GFCI protection even it where in the shower. A manufacturer listing could however require it or local amendment.
    – Kris
    Commented Sep 21, 2019 at 2:31

There is no issue in sharing the neutral as it is on the LOAD side of the GFCI.

enter image description here

Bathrooms do have specific codes which is pretty technical.
I'll try to sum it up:

  • All receptacles within a residential bathroom must be GFCI protected.
  • If only one bathroom is being fed by a single 20A circuit, the lights and other small appliances like exhaust fans may also be on the same circuit.
  • If multiple bathrooms are fed by a single 20A circuit, then only the receptacles are permitted to be on that circuit. Lights and other small appliances must be wired on a separate circuit.
  • If the switches to control the lights and other small appliances is in an adjacent room and not physically in the bathroom, it probably will require AFCI protection.
  • Regardless if others suggest the light in the bathroom shower should not be on a GFCI, and even if there is no specific NEC code stating it should be, always check the manufactures instructions. Being a fan/light combo it probably requires GFCI protection per the manufacture.
  • 1
    thank you. that seems correct. The inspector said that because the fan/light was above the shower, it MUST be protected by GFI. I knew this already, as I worked in this before. But what I was not completely sure of, was if the GFCI would be "unhappy" if it sensed load differences due to having the two appliances sharing a neutral return. I ran a 3 wire (red-black-white) cable to them as it was convenient. I have done this before on other circuits, that were not on GFI with no issues. Was just concerned there was any issues with sharing neutral on GFI loads. sounds like it will not be an issue. Commented Sep 19, 2019 at 22:28
  • There is no specific NEC code to put shower lights on a GFCI. But the manufacturer may require it. See diy.stackexchange.com/questions/89500/…
    – Kris
    Commented Sep 20, 2019 at 12:49

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.