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Tried to figure this out from previous posts but am still confused, and afraid.

Our 30 year old exhaust fan had a light, fan and heater. We're replacing it with a fan/light combo, no heater.

The switches independently operated the light, fan and heater. I had an electrician remove the heater switch and turn the 3 gang switch into a 2 gang.

I removed the old fan/light and there were only 2 supply Romex cables- the light was supplied by a Romex with a hot black wire, normal.

The fan wire has a hot white wire. Why is that?

Do I just connect the white wire to the black wire of the fan motor?![enter image description here] These photos show the 2 romex cables- one is switched to the light, and one is switched to the fan. The one to the fan shows a voltage tester on the white wire. The new light /fan wiring is shown. Does the black wire in the Romex go to blue, and the white wire of the Romex go to black of the fan?

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  • Are both the old Romex just Black + White + bare ground? If so, it is possible (though wrong) for the previous setup to have been: Romex 1: Switched Hot 1 + Neutral, Romex 2: Switched Hot 2 + Switched Hot 3. If so, that was wrong, but since you only need two Switched Hots now, the second Romex could become Switched Hot 2 + Neutral 2.
    – manassehkatz-Moving 2 Codidact
    Commented Oct 12, 2020 at 18:52
  • Yes both are just white, black and ground. So, just connect the white wire to the black in the fan?
    – Solly-SA
    Commented Oct 12, 2020 at 19:29

3 Answers 3

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In the past the white wire in a NM cable was used as either a hot or a switched hot in what is called a "switch loop". This is no longer done, but, e.g., my 1970 house is wired that way.

Consider the case of a wall switch controlled ceiling fixture where the line power is in the ceiling box, i.e., black hot and white neutral (plus bare gnd) are in the ceiling box. The white neutral would be connected directly to the neutral contact of the fixture and the hot would connect to one wire of a /2 + gnd cable going to the switch box.

The other wire in this cable would be the switched hot going back to the ceiling box and connected to the hot contact of the fixture. These /2 cables only came with white and black wires so the white had to be used either for the line hot or for the switched hot.

In this older arrangement there would be no neutral in the switch loop/switch box. At that time there was no need for a neutral in the switch box because the switches of that time did not consume power. New programmable switches do consume power and they require a neutral in the switch box to complete the circuit to allow current to flow back to the panel for their own internal operation.

Nowadays a /3 cable is used for this purpose with the white being used to carry neutral to the switch box and black and red used for hot and switched hot.

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  • So that arrangement allows 2 switched circuits off one wire?
    – Solly-SA
    Commented Oct 12, 2020 at 19:25
  • And so do I connect the hot white wire to the black in the fan?
    – Solly-SA
    Commented Oct 12, 2020 at 19:27
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    You don't just start connecting wires without knowing what is hot and what is neutral.. Do you have a voltage tester? It would be helpful if we could see pictures of the wires in the switch box and connections to the new fan/light assembly. Did the new light/fan come with instructions?
    – Jim Stewart
    Commented Oct 12, 2020 at 21:37
  • Added photos to original post. Looks like the black (hot) wire from the light wall switch goes to blue on the light, and the white (hot) wire from the fan wall switch goes to black on the fan. Correct?
    – Solly-SA
    Commented Oct 13, 2020 at 18:20
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    Is that picture the wires in the ceiling for the fan/light or is it the wires for the switches in the wall? We need both.
    – Jim Stewart
    Commented Oct 13, 2020 at 18:51
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I suspect since there were three separate circuits powered, that ONE (and only one) of the whites is neutral for all three (Fan, light and heater) and the other white and BOTH blacks are the switched hots for the FAN, Light and Neutral. It seems you've identified the FAN hot, and the other white is likely the neutral. That leaves two options for the "light" Hot (one of the blacks) the other black will be capped off and not used. And its likely your previous electrician did so on the other end already when he removed its switch.

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  • I think you are right. This is not allowed, however, a neutral must be in the same cable as its hot. The switch box wiring must be redone.
    – Jim Stewart
    Commented Oct 15, 2020 at 1:11
  • There are two cables from the switch box to the fixture. One cable (black switched hot and the white neutral that is in the same cable) will connect to the fan and the other cable (black switched hot and white neutral) will connect to the light). In the switch box the three neutral whites will be connected, the black line hot will go to one side of both switches, and the other side of each switch will get one of the blacks that goes to the ceiling box.
    – Jim Stewart
    Commented Oct 15, 2020 at 11:31
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If the line hot and its neutral are entering the circuit in the wall switch box, and the pic is of the ceiling box, then I think both whites in the pic should be wired as neutrals, and neither should be energized, if they are disconnected.

Do you see three cables in the switch box? (Each cable would have a black, a white, and a bare ground.) If there are three cables in the switch box, then test to see if one is the line hot from the panel. The other two would be carrying hot and neutral to the ceiling box.

In that case, proper wiring would have the black line hot going to two black pigtails, one to one side of each switch. The other sides of the switches would have one each of the outgoing black wires. These blacks would be switched hots. The white neutral with the line hot would be connected to the two whites going to the fixture.

At the fixture end one black would go to the black lead and one to the blue lead. The white with the black connected to the black lead goes to its white lead, and similarly for the other white

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