Adding a pull-cord override to a light-triggered extractor

[fidgetcat]

I've got an extractor fan in my bathroom that is wired into the lighting circuit, such that it comes on when the lights go on and then runs on a timer when they turn off. The light switch is a pull cord in the bathroom. The extractor is in the loft and also has a triple pole isolator switch in the loft. I'd like to rejig this a bit such that I can have a second pull switch in the bathroom that acts as an override to the fan coming on automatically when the lights go on. The bathroom has a window, so the fan is not necessary.

I think that I need to add the pull cord switch such that it interrupts the permanent live into the fan. This way, when the switch is closed, the fan will come on with the lights as normal, and whenever the switch is open, the fan will never turn on. I intend this to also let me use the 2nd switch to turn the fan off instantly at any point.

I could do with some advice on how to wire this. I know that I need a 2nd pull switch, but what else? I'm intending to leave the existing isolator in the loft in place.

Thanks in advance!

 

[PrinceofDarkness]

There's no way of using a second (standard) pull-cord to achieve this. It's possible to have a 'master' pull cord to control the permanent live but it can't be wired to double as an override switch to to use a timer fan as you fancy that it might be.

The standard pull-cord has no indication of the ON/OFF status - so you would have to rely your on memory: "Did I just switch ON or OFF?

Why don't you let the fan do its own thing? A change of air is a nice thing - whether it's needed or not. It doesn't cost a fortune to let a 20 Watt fan run......

 

[fidgetcat]

The fan is quite noisy, so it would be nice to be able to turn it off when it's not needed. I'm not sure that I understand your reply, or that my original post was that clear, so I'll elaborate:

At the moment, the isolator switch performs exactly the function that I want, except that it's in the loft. When the isolator is off, turning on the lights doesn't activate the fan (obviously). When it's on, turning on the lights activates the fan, and once the lights are turned off, the fan goes off after a short period of time. If the lights and fan are already on, switching the isolator to off immediately kills the fan, but leaves the lights on.

I believe that the isolator in the loft is isolating all the connections between the fan and the light circuit (switched live, permanent live and neutral). This is more than is necessary to act as a simple override switch, isn't it? I thought that by just putting a switch into the permanent live feed into the isolator, I could achieve the same effect, but I couldn't work out how to wire this. I know little about electrics, as you can probably tell.

I was thinking that I would put the switch into the permanent live rather than the switched live in order to be able to immediately turn the fan off if it's already on, rather than making it turn off after the timer period.

I don't think I'd need an on/off indicator - the fan wouldn't be on unless the switch was 'on', so it would be easy to tell the status by simply turning on the lights.

 

[333rocky333]

The timer permanent supply does not cut in, till the switched feed is off to the fan.
To stop the fan you would need to break both live pole and switched pole , or else the fan will run still while the light is on even without the permanent supply to the fan.
Why not shorten the time on the timer.

In a bathroom certain rules will apply to do this work.

 

[nozspark]

You can get a 3 pole, pull cord, fan isolator switch..

 

[PrinceofDarkness]

So the fan is noisy? This can only be due to clapped-out bearings, or the fact that the motor is screwed to a ceiling joist (probably in accordance with the manufacturer's instructions). I prefer to suspend an in-line fan on nylon cord attached to the rafters and not fixed to the joists. That way there'll be no transmitted or 'amplified' sound from above....

 

[vintagegt]

Why not just get an electrician to move the triple pole isolator to a place where you can reach it?

 

[fidgetcat]

Thanks for all the advice. I think I'm going to try suspending the fan from a rafter as suggested - this may remove my need to turn it off anyway. Failing that, it sounds like a pull cord isolator may be the way forward. I'd rather have the isolator in the bathroom itself, rather than a switch outside.

Out of interest, is the 'permanent live' into the fan actually live all the time, or is it just the opposite of the switched live?

 

[vintagegt]

Thanks for all the advice. I think I'm going to try suspending the fan from a rafter as suggested - this may remove my need to turn it off anyway. Failing that, it sounds like a pull cord isolator may be the way forward. I'd rather have the isolator in the bathroom itself, rather than a switch outside.

Out of interest, is the 'permanent live' into the fan actually live all the time, or is it just the opposite of the switched live?

The permament live is permanently live.

 

[fidgetcat]

Thanks for all the help and advice. I've just completed possibly the easiest and yet most effective bit of DIY I've ever done. I unscrewed the fan from the board mounted across the joists, screwed a hook into a rafter above and then suspended the fan from the rafter using some synthetic washing line. I cannot believe how quiet the fan now is! I certainly don't need to even consider turning the fan off now. A great tip!

Thanks again.

 

[vintagegt]

Thanks for all the help and advice. I've just completed possibly the easiest and yet most effective bit of DIY I've ever done. I unscrewed the fan from the board mounted across the joists, screwed a hook into a rafter above and then suspended the fan from the rafter using some synthetic washing line. I cannot believe how quiet the fan now is! I certainly don't need to even consider turning the fan off now. A great tip!

Thanks again.

Gotta admit, thats a good tip!