Change bathroom switch to separate light and fan.

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

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#2213323 9-Apr-2019 07:12

The fact that you have 3 red wires and only 2 black wires is an indication that something slightly different is happening. Where is the missing neutral conductor connected?

Rikkitic

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#2213338 9-Apr-2019 08:31

Until a simple test is performed, it's all conjecture.

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Bung

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#2213364 9-Apr-2019 09:23

The ability to test is something a lot of people ignore. The code of practice requires you to have a multimeter available.

If it's an installation old enough to have conduit wiring I wouldn't assume that the wires were necessarily phase and neutral. Lighting circuits were commonly wired with power at the light fitting and only the phase sent down for switching. That should have been with red wires or wires sleeved red but who knows what happens on a friday?

Rikkitic

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#2213374 9-Apr-2019 09:40

I couldn't live without a multimeter but in this situation, all that is needed is to establish if each red wire controls each device. It is a very simple test to disconnect them one at a time (after cutting the power, of course) and seeing what happens. If, as expected, they control the devices separately, then the switch can be installed and there is no need to worry about what the black wires or anything else does. Electrically, nothing gets changed except the red wires are switched individually instead of together. Of course, the fan and light could always be 120 volt US imports connected in series, but that isn't very likely.

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1101

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#2213411 9-Apr-2019 10:26

If you have to ask advice here , you really ARNT competent.

If you have to ask advice here , you shouldnt be doing to job.

Paul1977

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#2213431 9-Apr-2019 11:23

1101: If you have to ask advice here , you really ARNT competent. If you have to ask advice here , you shouldnt be doing to job.

I disagree that asking for advice automatically disqualifies you as being able to do a job. By that logic nobody would be able to anything.

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Paul1977

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#2213433 9-Apr-2019 11:27

larknz: The fact that you have 3 red wires and only 2 black wires is an indication that something slightly different is happening. Where is the missing neutral conductor connected?

I agree, which is why I haven't just gone ahead and done it already because it isn't quite what I would have expected.

Paul1977

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#2213435 9-Apr-2019 11:32

Bung: If it's an installation old enough to have conduit wiring I wouldn't assume that the wires were necessarily phase and neutral. Lighting circuits were commonly wired with power at the light fitting and only the phase sent down for switching. That should have been with red wires or wires sleeved red but who knows what happens on a friday?

What you've described is how all the other switches in the house that I have previously changed have been wired, with only phase going to the switch.

As @Rikkitic pointed out, this is easy for me to test - I just didn't get a chance to do this last night.

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#2213492 9-Apr-2019 12:16

Aside from the electrical wiring issue, which I would recommend engaging an electrician, there is the reason it was wired like this in the first place which I would assume would be to meet ventilation requirements for the bathroom. If you split these then don't engage the fan when needed you would get moisture build up and in turn mould. Whilst having the light and fan connected may be annoying for when you just want the light on to grab a toothbrush, you will be thankful there is a failsafe there in case you forget to turn the fan on when it is needed, as it sounds like you are unlikely to run the shower with the light off if you need it on to find a toothbrush.

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#2213573 9-Apr-2019 13:04

1101: If you have to ask advice here , you really ARNT competent.
If you have to ask advice here , you shouldnt be doing to job.

Whilst I somewhat agree with your comments ( although you aren’t a competent speller ;-)) ) ,
this site is full of people asking for advice.
There’s hardly a week goes by without someone asking how to wire their house for a network, and from the questions asked it’s obvious they have absolutely no technical knowledge in that area.

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#2213592 9-Apr-2019 13:26

Brunzy:
1101: If you have to ask advice here , you really ARNT competent.
If you have to ask advice here , you shouldnt be doing to job.

Whilst I somewhat agree with your comments ( although you aren’t a competent speller ;-)) ) ,
this site is full of people asking for advice.
There’s hardly a week goes by without someone asking how to wire their house for a network, and from the questions asked it’s obvious they have absolutely no technical knowledge in that area.

[EDIT: I see now whose spelling you were referring to]

I agree... why must so many DIY in areas they are not competent, skilled or qualified in... but feel they can once they bounce ideas around in a forum...

There a re qualified licensed people out there for a reason, it is not just for your safety now but for the safety of the next owner of the house. Not to mention the non-electrical implications.

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neb

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#2213600 9-Apr-2019 13:30

Rikkitic:
If the red wires are disconnected one at a time as suggested above, it will become clear if either device is looped off the other. If it behaves as expected, the switch can be changed without problem.

This assumes however that the house is wired as expected, and wires are colour-coded as expected, e.g. no active/neutral reversed. I've been in several houses, all dating back about 30-40 years, that have over time accreted a complete mishmash of wiring with things patched in by previous owners wherever they was a conduit, who-knows-what sort of connections (not helped by the change in colour codes during that period), etc. This place has the heat pump connected into the circuit for the fridge, wires draped at random across the attic like cobwebs, switches with no obvious function in the walls and four wires leading to them including odd colours like grey and white, and who-knows what else.

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#2213731 9-Apr-2019 16:42

gregmcc: BTW quite big difference between an electrician and an electrical engineer, "Electrical Engineers create designs that electricians have to fix to make work as intended"

Maybe tongue in cheek I realise, but methinks you are not an electrical engineer.

gregmcc

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#2213740 9-Apr-2019 17:25

mclean:

gregmcc: BTW quite big difference between an electrician and an electrical engineer, "Electrical Engineers create designs that electricians have to fix to make work as intended"

Maybe tongue in cheek I realise, but methinks you are not an electrical engineer.

no, not an electrical engineer, but way better an Electrical Inspector! ;)

Paul1977

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#2213743 9-Apr-2019 17:43

Well, it turns out this is not wired as expected at all.

The fan must be looped directly from the light batten after all, as when I disconnect one of the reds from "1" nothing worked, and when I tried the other both fan and light worked.

So I can't do what I want without an electrician, and I am left wondering what the extra wires hooked up to the switch are actually for... which makes me a little nervous as the only thing that happens when I turn on the switch is that the light and fan start - so what are these other wires powering?

As it stands I've put it all back how it was before I started looking.

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