I just bought a Broan 80n CFM ventilation fan with light to install in my shower that will replace an existing can light. When looking at my new Broan fan light, there are 7 wires:

  • 1-black,
  • 2-white,
  • 2-green,
  • 1-gray,
  • 1-brown

I have not done a lot with electrical- I know enough to connect black/black and white/white/white, green/green/copper. Not sure what to do with the gray and brown. The instructions say to refer to the wiring diagram, but the wiring diagram shows RED, BLACK, GROUND, and WHITE.

Can someone tell me

  1. what is the brown wire and how do I connect?
  2. what is the gray wire and how do I connect?
  3. Why only one black, but two whites and two greens?
  4. Also, should there be a green screw to connect copper wire or just connect all greens/copper together?

I called Broan and their hours are the same as my work hours 7:30am-6pm, so I guess I'll never be able to get help from them.

  • Can you post the model number of your vent fan? Commented Dec 11, 2021 at 17:01
  • CST80SL got it from Costco Commented Dec 11, 2021 at 18:11
  • Do you have separate switches for fan power and light power that go to the fan housing? If not you probably need to tie a couple of those wires together so the fan and light come on together
    – redlude97
    Commented Dec 11, 2021 at 19:53
  • I think I will probably put all on the same switch- out of convenience. My understanding is that I need to cap off the wire for the automatic sensor (brown wire???) since I only have one romex line going to the can light now. FYI, I do have another bathroom fan in the bathroom hooked up to a separate switch, but it does not go to the can light. I don't want to have to add another wire. I guess I will probably just have the fan and light on one switch. Commented Dec 11, 2021 at 20:17

1 Answer 1


Different hots for different things, since you have a fancy fan

Since your fan is fancy, it has different hot wires for different jobs:

  • The black wire is the hot to the light

  • The grey wire is the hot that's selected when the fan's built-in humidity sensor is not sensing humidity

  • The brown wire is the hot that's selected when the fan's built-in humidity sensor is sensing humidity

As a result, you can make the fan run off its internal humidistat exclusively, run off the humidistat with an override, or simply run when switched on at the light switch, depending on how you wire it.

  • Okay, thanks- very good to know. So, if I currently only have only one romex cable going to my light, and the romex is either 14/2 or 16/2, I can connect BLACK/BLACK+GRAY and WHITE/WHITE+WHITE and COPPER/GREEN+GREEN and cap off BROWN by itself. Should that allow me to turn the light and fan with the current switch that controls my current can light? Commented Dec 11, 2021 at 22:29
  • @LandonWhittington -- 14/2 or 12/2, and you'll want to include the grey and brown wires together with the black wires, so that the fan doesn't cut out when the humidity sensor turns on Commented Dec 11, 2021 at 23:36
  • Thanks. One follow-up question since I am connecting both fan and light to the same switch. If I connect the GREY and BROWN to BLACK, the humidity sensor will only come on when the switch is turned on- correct? And if the switch is turned on, the fan will come on anyway since the GREY wire is attached (is that correct?). So what is the benefit of having the BROWN wire attached to the same power as the GREY wire? Not sure I understand, but I'm new to this. Thanks again for the help! Commented Dec 12, 2021 at 4:47
  • @LandonWhittington -- it means that the fan won't inadvertently get turned off by the humidity sensor trying to turn it on :P Commented Dec 12, 2021 at 5:39

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