Change bathroom switch to separate light and fan.

Forums › Home Workshop DIY › Change bathroom switch to separate light and fan.

Paul1977

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#248745 8-Apr-2019 12:08

Let me preface this by saying that I am comfortable with doing things like changing light switches and power points in my own home. But I generally limit myself to like-for like replacements, but the following is a little different so just want to ensure I do it right.

In my bathroom the light and extractor fan run off a single switch, so either both are own or both are off. I would like to change this to a 2 gang switch so they are controlled individually. I don't want to get a sparky in to do this as I am more than confident with my ability to do the actual actual physical wiring into the switch, I just want to verify the way I wire it is correct.

The current switch is wired as follows:

1: Two red wires (presumably positive/phase)
2: No wires
C: One red wire (presumably positive/phase)
Loop: Two black wires (presumably negative/neutral)

How do I wire the 2 gang switch to give me separate control of the light and fan?

Thanks

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#2212757 8-Apr-2019 12:13

It depends on whether there are 2 cables or just 1 cable running between the switch, and the light + fan.

No one can answer that Question based on what you have said. You will need to do some testing. First of all to confirm which cable is the always on power, and which is the switched cable to the light + fan.

Short answer. Get an electrician in. You might need a whole new cable installed between the switch and the light or fan.

neb

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#2212758 8-Apr-2019 12:15

Aredwood: Short answer. Get an electrician in. You might need a whole new cable installed between the switch and the light or fan.

That's what I would have said too, in particular for bathroom wiring where the requirements are a lot more stringent than in other parts of the house.

Brunzy

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#2212759 8-Apr-2019 12:16

Remove one of the wires from 1 and see what stops working,
that’s assuming one goes to the light / fan.

evilonenz

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#2212761 8-Apr-2019 12:16

Aredwood:

Short answer. Get an electrician in. You might need a whole new cable installed between the switch and the light or fan.

This.

Having been through the same thing as you a few months ago, I wouldn't dare have tried it myself - I too am comfortable with changing out switches / power points, but in the case of splitting out two things from a single gang to double gang setup, I wouldn't even contemplate it without at least getting guidance from a sparky.

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neb

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#2212762 8-Apr-2019 12:17

Paul1977:
In my bathroom the light and extractor fan run off a single switch, so either both are own or both are off. I would like to change this to a 2 gang switch so they are controlled individually.

If it's just a case of not wanting to turn the fan on and off every time you go in to pick up a toothbrush or something, you can get run-on timers for fans that have delayed turn on, so you get something like 45s to get in and out before the fan kicks in after the light comes on.

Aredwood

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#2212767 8-Apr-2019 12:22

Brunzy: Remove one of the wires from 1 and see what stops working

Depending on how it has been wired, doing so might cause half of the lights in the house to stop working.

And that is before you deal with the risk of possible cross connections between circuits.

Brunzy

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#2212771 8-Apr-2019 12:35

Then at least he would have an idea of whether he could DIY ;-)

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MileHighKiwi

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#2212782 8-Apr-2019 12:48

Doing your own electrical work is a good way to void your home insurance policy.

Brunzy

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#2212786 8-Apr-2019 12:55

The op asked how to do it, I didn’t advocate that he should.

Paul1977

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#2212807 8-Apr-2019 13:15

The fan is newer cabling than the light and was clearly added later. The red and black from the fan are going into 1 and loop respectively.

Last time we had a sparky in for something else we had him look at this as well. He didn't want to touch it because some of the cabling is older conduit stuff. It's perfectly intact but he said if he did it he'd need to replace it, and getting the switches separated out wasn't worth it to us for the cost of doing that. It still isn't worth it to us if a sparky is going to insist on re-cabling.

In regards to invalidating home insurance, my understanding was that a home owner was allowed to change switches and power points themselves. Would changing this from a single gang to 2 gang not fall under the same category?

Rikkitic

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#2212826 8-Apr-2019 13:46

Paul1977:

Let me preface this by saying that I am comfortable with doing things like changing light switches and power points in my own home. But I generally limit myself to like-for like replacements, but the following is a little different so just want to ensure I do it right.

In my bathroom the light and extractor fan run off a single switch, so either both are own or both are off. I would like to change this to a 2 gang switch so they are controlled individually. I don't want to get a sparky in to do this as I am more than confident with my ability to do the actual actual physical wiring into the switch, I just want to verify the way I wire it is correct.

The current switch is wired as follows:

1: Two red wires (presumably positive/phase)
2: No wires
C: One red wire (presumably positive/phase)
Loop: Two black wires (presumably negative/neutral)
How do I wire the 2 gang switch to give me separate control of the light and fan?

Thanks

I am not a qualified electrician. I am not giving advice.

If this was my home and I wanted to do this, I would start by disconnecting one red wire at a time as suggested above. After cutting the power, of course. Normally disconnecting something won't hurt anything (though there are special cases). But I would be comfortable doing this to see what happens with each wire. My guess would be that one feeds the light, the other the fan. This would be logical. If that turns out to be correct, just continue and install the new switch.

The red wire at C will be feeding power to the switch, which connects it to the other two red wires. The two black wires are the common neutral wires. One of them should be the neutral connection back to the box while the other would carry the connection to the devices. The devices presumably have a common neutral connection with each other so only one wire from the switch is needed. This shouldn't affect anything because the devices are switched on the phase side.

This is my reading of the information provided. Again, I am not an electrician.

Plesse igmore amd axxept applogies in adbance fir anu typos

networkn

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#2212846 8-Apr-2019 14:11

neb:
Paul1977:

In my bathroom the light and extractor fan run off a single switch, so either both are own or both are off. I would like to change this to a 2 gang switch so they are controlled individually.

If it's just a case of not wanting to turn the fan on and off every time you go in to pick up a toothbrush or something, you can get run-on timers for fans that have delayed turn on, so you get something like 45s to get in and out before the fan kicks in after the light comes on.

We just did this for our bathroom extractor fan. So we got a switch/push button combination. The fan runs for 15 minutes pressed once and stops automatically. Much better.

Paul1977

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#2212851 8-Apr-2019 14:19

I think what @Rikkitic said might be right.

Below is how it currently appears to be wired:

And here is how I believe I can change it to a 2 gang switch:

Assuming that the diagram for the current wiring is correct, is the proposed method of changing it to 2 gang right?

EDIT: Actually the diagram for the current wiring isn't correct as there are only two black wires in loop, not three.

Rikkitic

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#2212865 8-Apr-2019 14:29

Looks fine to me.

Plesse igmore amd axxept applogies in adbance fir anu typos

Paul1977

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#2212871 8-Apr-2019 14:34

Rikkitic:

Looks fine to me.

See my edit above. The "current" diagram isn't correct is the actual switch has one less neutral wired in than the diagram does, so I need to figure that out first.

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