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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.....

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.

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

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, always check the manufactures instructions. Being a fan/light combo it probably requires GFCI protection per the manufacture.