So I read and read and no one quite seemed to have the same scenario as me. I'd give my self a Basic Plus to intermediate rating for electrical, pretty decent understanding but some of the lingo eludes me.

I have 2 wires (plus ground) coming out in 2 sets. One controls light & fan the other appears to control only the heater. I got an almost direct replacement. However, the diagram sure doesn't match what i have - no red wire and a sneaking suspicion the white to the heater was hot, not neutral. See pic with white tied to red. Red (from unit) is hot.

I took the best pics I could at the time (not great). Bit of a tangled mess before removing. Prior to replacing, the white wire definitely goes to the red (hot for the heater right?) which goes against the diagram and everything else I read. I got worried about switching cuz the second answer from isherwood in this post made made me wonder if I fit this description. <- This guy's post looks almost identical to my model except his wiring is slightly different.

So the 2 things messing me up is: is that white hot? What about the diagram and my lack of a red wire?

The fan/light looks fairly straight forward with the whites all tied together and black to black, except that darned blue to red...

I should also mention that 3 different switches independently control each function, so no tie ins or whatever.

Big thanks ahead of time!

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Ok, so I stuck my tongue out and tried different combos of wires....No, got the multi meter out and confirmed the right side wires are indeed backwards (white = hot, nothing on the black). Th left side branch is how it should be. Took some photos of the switch box as well. Ignore the right most switch, not related. They're labeled in pics. The white with post it note (if you can't read it) is the hot white.

  • For the heater: the hot white to red (heater), black to the white (seriously?? who did this wiring?), ground is obvious. Should I swap the wiring on the switch and reverse it? Or just tape it/label it accordingly.

  • For the correctly routed/colored one - since there is no red wire: black AND blue go to the black from wall (the hots), a bundle of whites (from ceiling with other 2 tied together), again ground obvious.

Thanks for all the input.

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  • I could see a way to wire this where one white would be a true neutral and the other white and both blacks would be switched hots. Opening the switch box could help, but testing with a volt meter while you turn on each switch could also help figure it out, but you have to be very careful with that. Red wire is found in romex that contains three wires, which is more common than running two cables like you have.
    – JPhi1618
    Commented Sep 27, 2021 at 19:28
  • At the switch box with three switches you should have one cable (black/white/ground) supplying power. You don't show that. Do you? And another cable or cables with 5 total wires going to the device. The 5 total wires could be achieved with two cables as in your picture. Do they both go from the switch to the device? EG One switched black for the heater, one switched black for the fan, one white marked as switched hot for the light and the other white and bare for neutral and ground. There doesn't need to be a red wire, you just need to be able to tell the three hots apart.
    – jay613
    Commented Sep 27, 2021 at 19:31
  • Note, the instructions say "Use only 20A branch circuit" and "1300W". Are your wires all #12? Hard to tell from pic. If they are #14 you need a 15A breaker, which is plenty for a 1300W device, but you do have the issue that the label strangely says to use a 20A breaker. And the internal wires appear to be #14 at best, maybe #16. Odd.
    – jay613
    Commented Sep 27, 2021 at 19:44
  • @jay613 It's not a good idea to suggest deviating from the installation instructions. The UL listing is based on the unit being installed per the instructions.
    – JACK
    Commented Sep 27, 2021 at 20:23
  • @jay613, #14 wire is the smallest you can use in the wall, so its not #16. Also, since its a heater, you have to use the 80% derating of the circuit which gives you 1400W on a 15A breaker to run the heat, fan, and bulb. Guess they didn't think that was enough of a safety margin.
    – JPhi1618
    Commented Sep 27, 2021 at 20:38

2 Answers 2


Your installation (as it was) needed 3 hots and 1 neutral. I suspect the original installer didn't want to bother sourcing /4 cable or using smurf tube, so simply doubled up two /2 cables and called it a day. As such, one of the whites is being used as a hot. "Misused", probably. NEC is not as clear on this point as I would like.

If you don't want to correct that, make sure to have the black with the real neutral serve the heater, to minimize the numerous reasons why ganging 2 cables like that is problematic.

Otherwise the way to do it with existing cabling is to de-task white back to a neutral, and make one switch control light+fan together. Like their drawing, but tie the socket black and blue together.

  • Ok, so had to process a lot of info with everyone's input: You were correct about 3 hots/1 neutral. I ended up basically repeating how it was already done (which I know is not ideal/to code). It was that way for about 30 years and the house didn't burn down yet. 1 hot black went to light, 1 hot black went to fan, the hot white went to heat with the rest of the whites tied together. Grounds as well. Works great
    – The Gunth
    Commented Oct 1, 2021 at 18:54
  • Well, heater is the largest current draw, so I would make a point to use the partner black to the actual neutral. Your 30 year "sample size of 1" is not valid if you worsen the conditions! Commented Oct 1, 2021 at 19:10

Ok, first you need to figure out which cable is for the heater. You have two individual circuits going from your switch box to the fan enclosure. Each circuit has a hot (black), neutral (white) and ground (bare). You'll need a voltage sensor or meter to determine this. It's important you put the heater back on it's original circuit because it's probably a dedicated circuit. The fan and light are probably on the general lighting circuit in that area.

Now you see in the fan wiring by box, each lead for fan (black), light (blue), and heater (red) have their own accompanying neutral (white) lead. This is so you can divide these 3 functions in up to 3 individual circuits without crossing neutrals.

So the cable for the heater, the black and white will connect to the red and white for the heater. The cable for the fan/light will connect to the black/blue and both their whites. And as always, the grounds are always all tied together.

Please feel free to ask for clarification.

  • 1
    There are three functions - fan, light, heat and each one needs a switched hot.
    – JPhi1618
    Commented Sep 27, 2021 at 20:33
  • The old unit had the fan and light tied together. The new one will have to be wired this way too. There are not enough conductors.
    – DrSparks
    Commented Sep 27, 2021 at 23:05
  • @DrSparks Checked the voltages and posted some pics of the switch box for ye
    – The Gunth
    Commented Sep 28, 2021 at 3:07

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