Yet another bathroom extractor fan question...

[DeadJoe]

I'm wanting a timed extractor fan in the bathroom.

I want the fan to be switched seperately from the lights, using a seperate pullcord - I don't need it to come on every time the light is switched on, and for noise and energy-saving reasons would prefer it didn't. There's already a window in the bathroom.

I already have an electric fan heater on the wall in there, operated by its in-built pull cord. The wall heater is supplied from outside the bathroom via an isolation switch spurred from the main ring.

Questions:

(1) I understand the fan has to be connected via an isolator switch outside the bathroom. Is there any reason why I couldn't use the same isolator and supply that is supplying the heater, rather than using the lighting circuit for power? This would mean one switch isolating both fan and heater, with the lighting circuit completely seperate from both. The alternative is two isolation switches outside the bathroom, with the possibility of confusion between the two...

(2) I would like to set things up so that the fan cannot be left on. Is there such a thing as a contact-only pullcord switch - a pullcord switch that can be pulled to energise the timer, but doesn't actually stay in the 'on' position? I am hoping to be able to reach a situation where the fan can be switched on independently of the lights, where it will run on only for the period the timer dictates, and cannot inadvertantly be left in the 'on' position where it might run all day. It's either that, or a neon on the pullcord, I guess...

What do you think?

 

[riveralt]

I'm wanting a timed extractor fan in the bathroom.

I want the fan to be switched seperately from the lights, using a seperate pullcord - I don't need it to come on every time the light is switched on, and for noise and energy-saving reasons would prefer it didn't. There's already a window in the bathroom.

I already have an electric fan heater on the wall in there, operated by its in-built pull cord. The wall heater is supplied from outside the bathroom via an isolation switch spurred from the main ring.

Questions:

(1) I understand the fan has to be connected via an isolator switch outside the bathroom. Is there any reason why I couldn't use the same isolator and supply that is supplying the heater, rather than using the lighting circuit for power? This would mean one switch isolating both fan and heater, with the lighting circuit completely seperate from both. The alternative is two isolation switches outside the bathroom, with the possibility of confusion between the two...

You will need to fuse down the circuit as per the manufacturers instructions normally a 3Amp Fused Connection Unit will do - additionally you will need a three pole isolator unless you follow the diagram in Wiki.

(2) I would like to set things up so that the fan cannot be left on. Is there such a thing as a contact-only pullcord switch - a pullcord switch that can be pulled to energise the timer, but doesn't actually stay in the 'on' position? I am hoping to be able to reach a situation where the fan can be switched on independently of the lights, where it will run on only for the period the timer dictates, and cannot inadvertantly be left in the 'on' position where it might run all day. It's either that, or a neon on the pullcord, I guess...

You can set up the circuit so that the extractor fan works directly with a normal pull cord switch and no light - you will however need to have and FCU and a three pole isolator unless you follow the diagram in Wiki.

 

[flameport]

Is there such a thing as a contact-only pullcord switch - a pullcord switch that can be pulled to energise the timer, but doesn't actually stay in the 'on' position?

Yes, they are called retractive switches.
Typically used for emergency alarms, or for starting shower pumps. However no reason why one could not be used for starting a fan.

Here is one: http://uk.rs-online.com/web/1860279.html
The red cord can easily be replaced.

 

[riveralt]

Is there such a thing as a contact-only pullcord switch - a pullcord switch that can be pulled to energise the timer, but doesn't actually stay in the 'on' position?

Yes, they are called retractive switches.
Typically used for emergency alarms, or for starting shower pumps. However no reason why one could not be used for starting a fan.

Here is one: http://uk.rs-online.com/web/1860279.html
The red cord can easily be replaced.

I know the OP talks about having one of these but why would you go down that route its like having a timer within a timer- the OP talks about a extractor fan with timer - if he has wired it properly a normal pullcord switch will keep the fan running for a set period of time.

 

[DeadJoe]

@ riveralt...

As regards a three pole isolation switch, I was thinking that since the existing two pole switch isolates the entire supply to the heater in the bathroom, it would be possible to connect the fan on the same side as the heater before the pull switch and timer, isolating everything in the bathroom on that circuit. Effectively there is no switched live outside the bathroom for a three pole isolator to operate on. The switched live is created at the pull-switch after the isolating switch. But that does still leave the problem of fusing down the circuit...

@ flameport...

That looks like exactly the thing. On the same page it has something called a 'momentary action' pull-switch. I'm more confident now that this is something that might work, if I can deal with the fuse issue.

@riveralt...

You said this:

I know the OP talks about having one of these but why would you go down that route its like having a timer within a timer- the OP talks about a extractor fan with timer - if he has wired it properly a normal pullcord switch will keep the fan running for a set period of time.

The reason I am thinking about a momentary switch is because if it is wired with a standard pull switch (which locks in either 'on' or 'off' positions), it would be really easy to walk into the bathroom, pull the cord to switch the fan on, and then go out of the bathroom and not remember to turn it off. It could run all day - the timer only controls run-on after the switch has been pulled to off.

The obvious answer would be to connect it to the light-switch like everyone else does - then it's easy to tell that it has been switched off. But, it's a small house and the noise from the fan is likely to be a nuisance at night (if someone makes a brief visit to the loo). I'm looking for a way of having the choice of whether it comes on or not, and ensuring that it can't get left on.

 

[riveralt]

@ riveralt...

As regards a three pole isolation switch, I was thinking that since the existing two pole switch isolates the entire supply to the heater in the bathroom, it would be possible to connect the fan on the same side as the heater before the pull switch and timer, isolating everything in the bathroom on that circuit.

Didn't you say that the heater was run from a spur of the ring final circuit?
I would imagine that that is fused down to 13Amp whereas the fan needs to be 3Amp. Size of fuse aside, I'm sure you could do this but it doesn't feel right.

The fan will need switch live, neutral and permanent live which is why a three pole isolator is suggested. As I said if you look at Wiki you will see there is a way to avoid using a three pole isolator.

Effectively there is no switched live outside the bathroom for a three pole isolator to operate on. The switched live is created at the pull-switch after the isolating switch. But that does still leave the problem of fusing down the circuit...

You really need to look at the wiring diagrams provided by the extractor fan manufacturers.

The reason I am thinking about a momentary switch is because if it is wired with a standard pull switch (which locks in either 'on' or 'off' positions), it would be really easy to walk into the bathroom, pull the cord to switch the fan on, and then go out of the bathroom and not remember to turn it off. It could run all day - the timer only controls run-on after the switch has been pulled to off.

These fans aren't exactly silent which kind of contradicts your next statement.

The obvious answer would be to connect it to the light-switch like everyone else does - then it's easy to tell that it has been switched off. But, it's a small house and the noise from the fan is likely to be a nuisance at night (if someone makes a brief visit to the loo). I'm looking for a way of having the choice of whether it comes on or not, and ensuring that it can't get left on.

The purpose of these fans is to vent moisture out of the bathroom - unless you have been seriously at the curry why would you want to turn it on at nightime and wake everyone up anyway?

 

[DeadJoe]

I think we're misunderstanding each other somewhere for some of this, at least...

Didn't you say that the heater was run from a spur of the ring final circuit?
I would imagine that that is fused down to 13Amp whereas the fan needs to be 3Amp. Size of fuse aside, I'm sure you could do this but it doesn't feel right.

Yes. It's on a spur, and yes, fused down to 13A. I've just had another look (at home now) it's isolated with an FCU.

The fan will need switch live, neutral and permanent live which is why a three pole isolator is suggested. As I said if you look at Wiki you will see there is a way to avoid using a three pole isolator.

I'll have another look at the Wiki. All I could find was the standard 'fan into lighting circuit' diagram.

You really need to look at the wiring diagrams provided by the extractor fan manufacturers.

I'll dig around on-line. What I don't want to do is go off half-cocked and buy the wrong gear and only find out its wrong when I look at their recommendations.

The reason I am thinking about a momentary switch is because if it is wired with a standard pull switch (which locks in either 'on' or 'off' positions), it would be really easy to walk into the bathroom, pull the cord to switch the fan on, and then go out of the bathroom and not remember to turn it off. It could run all day - the timer only controls run-on after the switch has been pulled to off.

These fans aren't exactly silent which kind of contradicts your next statement.

The thing with a timed fan operated from its own pull cord is that you can't tell easily if the power to the fan is on or off. If someone walks into the bathroom, turns the fan on and leaves without turning it off, then it will run all day. If they remember, and go back and switch it off, it will continue to run for another 20 minutes or whatever. Unless of course they did switch it off originally, but it was on the timer, and when they went back to switch it off, they actually switched it back on again...

The obvious answer would be to connect it to the light-switch like everyone else does - then it's easy to tell that it has been switched off. But, it's a small house and the noise from the fan is likely to be a nuisance at night (if someone makes a brief visit to the loo). I'm looking for a way of having the choice of whether it comes on or not, and ensuring that it can't get left on.

The purpose of these fans is to vent moisture out of the bathroom - unless you have been seriously at the curry why would you want to turn it on at nightime and wake everyone up anyway?

I wouldn't. Which is why I need it to be on a circuit separate to the light.