Wiring in a bathroom extractor fan

[gdunbar]

Hello,

I'm going to get an inline extractor fan fitted in the loft. Currently the bathroom has a pull down cord. I'm thinking of getting rid of the pulldown cord and instead having a 2 gang switch outside the bathroom (one switch for the light and one for the extractor fan). I don't want the fan switching on with the light ie. I don't need the light on in the summer, or when visiting the toilet in the middle of the night, etc.

Is this new setup fairly straight forward for the electrician to do. Will it work off the existing light circuit or will the extractor fan need a seperate power source?

There is a power socket outside the bathroom which is below the position of the new light switch. But the heater in the bathroom is running off of this via a fused connection. Can an extractor fan also be connected to this socket or is this too much?

Thanks for your help.

Glyn

 

[Doggit]

Your proposed setup is sound, just take the power from the lighting circuit to power the fan rather than socket. A good leccy will have no problem on what you want.

 

[ban-all-sheds]

I don't want the fan switching on with the light

When do you want it switching on? Maybe the ideal solution for you is not to have a manual switch at all.

 

[gdunbar]

Cheers for the reply Doggit.

When do you want it switching on? Maybe the ideal solution for you is not to have a manual switch at all.

I just want it to work when we either use the shower or have a bath. I did look at Humidstats but a standard switch will do what we want and is alot cheaper.

I'm thinking of installing the backbox in the wall myself and running the cabling from the backbox to the loft, to save the electrician time. Will I need three runs of cable (one to switch on the light, and the other two to take power from the light and the other cable to switch on the extractor)?

Will this cable do the job Twin & Earth cable 1.5mm or will he need Three core 1.5mm?

Thanks.

 

[Taylortwocities]

Will this cable do the job Twin & Earth cable 1.5mm or will he need Three core 1.5mm?

It depends on what is present at the light. If you have a loop-in system at the light, you would need 3 core and earth from the light to the switch and 2 core and earth from the switch to the fan. I'm assuming that you will not be having a timer fan?
The wiring will be different if you have one of the many other ways of wiring up a lighting circuit.

You won't need 1.5mm² cable. 1.0mm² will be big enough.

 

[gdunbar]

I'm assuming that you will not be having a timer fan?

Yes it is a timed version. It is a Vent Axia ACM100T

 

[ban-all-sheds]

I just want it to work when we either use the shower or have a bath.

If you've got a mixer shower, i.e. not an instant electric one, clip a temperature operated switch to the hot water pipe. That way the fan will kick in automagically when the shower is on or the bath filled, and you won't need a manual switch at all. And you might not need a timed fan, either, if the pipe remains hot for long enough after you stop drawing water.

 

[Taylortwocities]

Yes it is a timed version. It is a Vent Axia ACM100T

Then you will need 3core and earth from the switch to the fan. But you do not need a timer fan if it is on its own switch.

 

[Doggit]

At the end of the day, the cabling will depend on where everything is in the bathroom. Being a timed extractor, you need an extra supply for the overrun facility. You need a single gang double switch, and you can take 2x 1mm t&e to both switches, and then take the extra live feed from the light pendant to the fan, so you really need to talk to the electrician who's going to do the work, unless you're intending to tackle this yourself of course.

But Taylors also right in using a 4 core cable to the light switches but that might make it problematical depending on the layout, and whilst he's also right in not needing a timer fan as it's on it's own switch, it won't be an issue, and the overrun will just clear things after you've left the bathroom.

 

[gdunbar]

Great, thanks everyone for taking the time to reply.

 

[ban-all-sheds]

you do not need a timer fan if it is on its own switch.

Why not?

 

[Taylortwocities]

Personal preference. I forseethat the OP will forget to turn off the fan switch so it will be left running unnecessarily.
Having it switched by the light switch means less chance of that, because the room light serves as a fan on indicator.

 

[ban-all-sheds]

Firstly, it isn't going to be switched by the light:

I don't want the fan switching on with the light ie. I don't need the light on in the summer, or when visiting the toilet in the middle of the night

Secondly, you said "you do not need a timer fan if it is on its own switch". Is that because you think they'll forget to turn it off, and that will provide the overrun facility, or because you think that if it's on its own switch it won't need to run on for a while to finish clearing the room?

Lastly, how does what else the switch controls affect whether a timed overrun is needed or not?

 

[Doggit]

It's really a bit of a reverse there. A fan can be controlled from the light switch, and it can be a bog standard switch on the lights and it starts, and then switch the lights off, and it stops, and this type can be fitted on it's own switch if you don't want it working say at night. But if you want the fan to carry on working after you leave the bathroom, then you need an overrun facility that needs a separate live feed to allow it to carry on working. So a timer (or overrun) fan isn't normally fitted on it's own switch, but that doesn't mean it can't be. BAS is right when he says that having the overrun can fool you into not switching the fan off, so it's down to OP as to can he remember to always switch the fan off.

 

[ban-all-sheds]

Nobody needs to remember to turn it off, or on, if it goes on and off via use of the shower etc.