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I’m trying to work out if it’s possible (and up to code) to split an existing three way switch that controls my bathroom lights and exhaust fan.

The ideal outcome would be:

  • Caseta dimmer and accessory dimmer control the lights
  • Switch controls the fan
  • Second switch controls laundry lights (in same room)

The present switch setup is:

  • 2-gang switches, one for laundry lights and one as part of three-way switch controlling the lights and exhaust fan
  • 1-gang switch as the second three-way switch for the lights and fan

Here is a photo of the existing three-way switch and part of the single switch (btw: the house was built in the early 1980s): One part of the three way switch, with the one pole switch for the laundry lights beside it

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  • You cn do this if (1) the light/fan combo allows separate power to the light and the fan and (2) the wiring from the switch to the light/fan combo has both red and a black wires to provide separate switched hots for the light and the fan. Usually the two can share a single white neutral. I think these units probably are sold with a "jumper" connection between the light and the exhaust fan so that the unit can be installed with a single switch, but would have instructions to cut or remove the jumper if it is being installed with separate switches for light and fan. Commented Dec 29, 2023 at 12:04
  • Almost certainly any changes necessary can be done from inside the bathroom. Access with be by removing the exterior cover and then an interior cover a connection block. IF you have the right wiring in the walls. Commented Dec 29, 2023 at 12:10
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    You might be lucky and have enough wires in the wall to power the light and fan separately, but the installer just put in a single switch and connected two switched hots to the one switch. If that is what you have, all you would need to do would be to change out the single switch for a "double" switch and you would not even have to change the wall box to a 2-gang. A double switch has two separate switches in one unit. A single line hot is connected to one side and two switched hots are conneected to the other sides of the two switches. Commented Dec 29, 2023 at 12:21
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    Can you post photos looking into the back of the boxes in question please? Commented Dec 29, 2023 at 12:36

1 Answer 1

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This exact question was asked 2 days ago

One Switch (3-way) for Two Fixtures

A 3-way switch can't be magically replaced by a duplex switch. If you find out that you have extra wires going between the switches and the fan, then we can talk. Otherwise, those 3-way switch wires go between the switches and not to the fan.

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  • What would be the simplest way for the OP to determine if his wiring would allow the light and fan to be operated independently? Would it be to look in the switch boxes or would it be to look at the connection block of the light/fan? Presumably the latter would allow him to easily be working with the switched hot(s) off at the switches. In my house the connection blocks are accessible from the living space. He should take a good picture of the connection block if he does this. Commented Dec 29, 2023 at 18:17
  • Thanks; it seems like the answer is “call an electrician”. I don’t want to damage anything and even if whoever installed it went out of their way to add cables to allow separate switching (and dimming, in the case of the lights), they didn’t make it obvious.
    – emoulson
    Commented Dec 30, 2023 at 18:59
  • @JimStewart This scenario with 3-way switches and a fan and lights, it's not as simple as looking at wires. Even with photos I doubt we would have an answer to that. Commented Dec 30, 2023 at 19:04

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