Wiring a bathroom fan and lights independently

[TJ1]

I already have a bathroom fan installed on a pull cord switch which operates the fan and light and I want to make it so the lights come on independently of the fan. I want the light switch for the lights on the outside of the bathroom (obviously) and the pull cord for the fan in the bathroom.
Can anyone help with the wiring side of things please?

 

[garlicbread]

You need to identify where the fan and lights are connected together. Assuming it is at the light or a JB, then you need to run another twin brown & Earth to the switch outside the bathroom.
Your original switch wire from the pull cord should connect to both the fan and light at the same point. Disconnect the one that goes to the light, this now connects to the switch wire of your new switch.
The other brown at the new switch should be terminated with the feed/line for the bathroom lights (which will also include a wire for the fan if it has a timer override).

Test all the power is off to the lighting circuit before working on it. (safe isolation)

It would be better to get a competent electrician in to do the work, as it will probably save you money in the long run if you don't get things right!

 

[TJ1]

You need to identify where the fan and lights are connected together. Assuming it is at the light or a JB, then you need to run another twin brown & Earth to the switch outside the bathroom.
Your original switch wire from the pull cord should connect to both the fan and light at the same point. Disconnect the one that goes to the light, this now connects to the switch wire of your new switch.
The other brown at the new switch should be terminated with the feed/line for the bathroom lights (which will also include a wire for the fan if it has a timer override).

Test all the power is off to the lighting circuit before working on it. (safe isolation)

It would be better to get a competent electrician in to do the work, as it will probably save you money in the long run if you don't get things right!

Yes I understand, will study what you say and thanks. Will get electrician if unsure.

 

[ericmark]

In the main fans are wired to the ceiling rose. There are three general types of fan those with and those without run on. Plus those with humidity control. If it has run on then likely triple and earth cable will be used so easy to identify.

Nothing in the rules say that the fan should be triggered by lights in fact where there is natural lighting and no opening window it says the reverse and the fan has to be able to be switched on without the lights.

However most people want to ensure the fan is used hence connecting to lights. Using double pole switches allows it to auto start with lights and also have independent start.

Before anyone can work out how to re-wire to things are needed one exactly how you want it to work and two what type of fan you have.

I am uncertain on timings for fan when it says 15 mins not sure if that's after leaving room or from when fan is switched on but using pneumatic switches is common to get timed run on.

So the fan switch could be on/off or momentary on type the latter just triggering the run on timer.

With so many variations before going into details really need more information.

Do remember this work may need building control approval and registering so may be cheaper to use a scheme member electrician.

 

[JohnW2]

I am uncertain on timings for fan when it says 15 mins not sure if that's after leaving room or from when fan is switched on but using pneumatic switches is common to get timed run on.

A fan with a run-on timer will run for the set period after the trigger ('switched live') voltage is removed, provided the permanent live remains live. If one wanted a run-on period after manual switch on/off, the switch would therefore have to switch the feed to the 'S/L' terminal of the fan, the fan's 'permanent live' terminal being permanently live. The fan would then come on when manually switched on, remain on so long as the switch was still 'on' and then run for the timed period after it was switched off.

If one wanted the fan to go off immediately it was (manually) switched off, one would link the L and S/L terminals of the fan and then switch the supply to these joined terminals.

Kind Regards, John

 

[ericmark]

Any automatic control must provide manual over-ride to allow the occupant to turn the extract on.

For a room with no openable window (i.e. an internal room), the fan should have a 15 minute over-run. In rooms with no natural light, the fans could be controlled by the operation of the main room light switch.

From Ventilation part F building regulations approved document.

What the document does not make plain is from what point that over run is timed from. I would have thought from leaving the room but it does not say that.

So the question is would a pull switch be considered as complying where it starts the timer? Clearly if the person spent 20 minutes it would have stopped before they leave but again nothing to stop then pulling the switch twice.

My bathroom does not require a fan so if I fit one I can do as I like. But where it's required by law clearly one has to comply with the law when the work is subject to part P as well so LABC will be involved.

If one wanted the fan to go off immediately it was (manually) switched off, one would link the L and S/L terminals of the fan and then switch the supply to these joined terminals.

This is only where a fan is an extra, what one wants is nothing to do with what one must do to comply with the law.

 

[JohnW2]

So the question is would a pull switch be considered as complying where it starts the timer? Clearly if the person spent 20 minutes it would have stopped before they leave ...

As I recently wrote, that's not how run-on timers work. If the fan has a permanent live and the pull switch feeds the 'trigger' ('S/L') input of the fan, then, once the switch has been pulled to switch on the fan, the fan will stay on indefinitely if the switch is not pulled again, and then will 'run-on' for the set period (15 minutes or whatever) after the switch is pulled the second time.

Kind Regards, John

 

[ericmark]

A momentary pull switch will either remove or introduce power when pulled. Note the red cord. A latching switch would work as you describe.

The switch I show would cause the fan to run for the programmed run on time when correctly wired but not sure as I have said if this would be accepted by LABC.

Also as yet no input from posted as to what they require.

 

[TJ1]

A momentary pull switch will either remove or introduce power when pulled. Note the red cord. A latching switch would work as you describe.

The switch I show would cause the fan to run for the programmed run on time when correctly wired but not sure as I have said if this would be accepted by LABC.

Also as yet no input from posted as to what they require.

The fan just comes on when switched on and goes off when switched off, there doesn't seem to be any timer on it.
Thanks all who have posted.

 

[JohnW2]

A momentary pull switch will either remove or introduce power when pulled. Note the red cord. A latching switch would work as you describe.

Well, yes - I have to confess that I hadn't even considered the possibility that anyone would use a 'momentary', rather than conventional ('latching') switch in such a situation. As you say, a momentary switch would provide just a timed 'on-time' - not a timed 'run-on', which is what I thought the regs required.

The switch I show would cause the fan to run for the programmed run on time when correctly wired but not sure as I have said if this would be accepted by LABC.

Maybe I'm wrong but, as above, I thought the regs required a 'run-on', not just a timed 'on' period. It would seemingly make little sense if the fan was only on for the first 15 minutes of, say, a protracted 40-minute shower or bath - so I doubt that LABC would accept it.

These regs are, in any event, probably a bit 'silly'. If there is an 'openable window', there is no regulatory obligation to have any fan - but nor is there any compulsion to open the window, ever!!

Kind Regards, John

 

[ericmark]

It would seem no timer so that bit does not matter but still no idea if required or an extra so still can't really work out what is required.

Is there a window and does it open?

 

[Astra99]

Whether the fan is a run-on version with two live feeds, or a "standard" version, I thought that a two- or three-pole isolator was required for isolation purposes. Is this not the case?

 

[JohnW2]

Whether the fan is a run-on version with two live feeds, or a "standard" version, I thought that a two- or three-pole isolator was required for isolation purposes. Is this not the case?

Only if the manufacturer's instructions say so - and even that probably only until next year!

Kind Regards, John