Bathroom extractor fan

[danoid]

Firstly, I will not be doing this myself, just after some information.

In my bathrooms I don’t have any extractor fans just a heat operated flap which barely works.

what I’d like to have is a isolator switch outside the bathrooms, which I can turn the fan on/off with a timer and independent of the lights for the bathroom.

Is this possible? If so where does the power come from as I do not want to have to turn the light on in order to use the fan.

If it’s possible, when I turn the switch to turn the fan on, I’d like it to be on a timer, so I guess the next time I want to use the fan I’d switch the isolator to off then switch back to on to use the fan.

If it can work like that I’m happy, I just can’t understand where the power would come from as I only have a light there

 

[JohnD]

Do you have access above the ceiling?

 

[RandomGrinch]

I think your way will work fine, although with the configurations available with a decent modern fan, the conventional way of wiring (to come on with a light) isn't really an issue.
As long as there is a permanent live available, a fan with a humidistat can turn itself on when required.
There are even versions that are WiFi controlled!

Edit:
Please correct me if I'm wrong!
If you want a run-on timer, you may still need two switches. One to turn the fan on, but it will still need a permanent live for the run-on. So will also need an isolator?
Switching through the light switch might save you another switch to mount.

...and if the manufacturers instructions say so, the fans power can come straight from the lighting circuit (through an appropriate isolator!).

 

[JohnD]

I do not want to have to turn the light on in order to use the fan.

What ill effects do you foresee from using the light switch?

 

[Harry Bloomfield]

A PIR with run on timer included in the fan, obviates the need for light to trigger the fan when there is no need to turn the light on. An included humidity sensor in the fan is also useful to have, the fan will then continue to run until the high humidity is cleared in a bathroom due to a bath or shower.

 

[danoid]

Do you have access above the ceiling?

Yes as these are both upstairs with loft space above

What ill effects do you foresee from using the light switch?

Nothing major, as I ideally want them on a timer if we go for a wee in the middle of the night then it’s whirling away for ages for no reason which brings me into a rage (previous house experience the neighbours left their fan on in a modern house which meant we heard everything argh)

 

[danoid]

I think your way will work fine, although with the configurations available with a decent modern fan, the conventional way of wiring (to come on with a light) isn't really an issue.
As long as there is a permanent live available, a fan with a humidistat can turn itself on when required.
There are even versions that are WiFi controlled!

Edit:
Please correct me if I'm wrong!
If you want a run-on timer, you may still need two switches. One to turn the fan on, but it will still need a permanent live for the run-on. So will also need an isolator?
Switching through the light switch might save you another switch to mount.

...and if the manufacturers instructions say so, the fans power can come straight from the lighting circuit (through an appropriate isolator!).

A PIR with run on timer included in the fan, obviates the need for light to trigger the fan when there is no need to turn the light on. An included humidity sensor in the fan is also useful to have, the fan will then continue to run until the high humidity is cleared in a bathroom due to a bath or shower.

I was looking into these humidity sensors, but as they only work on humidity not too great when you have a stinky number 2

 

[JohnD]

A good modern fan with ball-bearing motor is almost inaudible, and you will not hear it with the door shut. There are a couple of very good brands.

The cables bringing the electrical supply go to the ceiling rose (so it is always live even when the light switch is off)

And another cable goes from the rose to the light switch, and returns to the rose to supply the switched live to the lamp.

So you can supply the fan from the ceiling rose, and you can have a separate fan switch if you want. Or let the light switch control it.

 

[RandomGrinch]

Nothing major, as I ideally want them on a timer if we go for a wee in the middle of the night then it’s whirling away for ages for no reason which brings me into a rage

Modern fans often have 'delay timers' as well. Might be just long enough for a pee!

 

[JohnD]

I was looking into these humidity sensors, but as they only work on humidity not too great when you have a stinky number 2

Another advantage of the light switch is that no extra effort is needed to provide ventilation.

 

[EFLImpudence]

An isolator isn't a requirement nor necessary.

 

[Harry Bloomfield]

Nothing major, as I ideally want them on a timer if we go for a wee in the middle of the night then it’s whirling away for ages for no reason which brings me into a rage (previous house experience the neighbours left their fan on in a modern house which meant we heard everything argh)

With our bathroom door closed, our fan is inaudible - your noisy one was likely an old one with worn bushes.

I was looking into these humidity sensors, but as they only work on humidity not too great when you have a stinky number 2

Taken care of by fitting one which has both humidity and PIR trigger.

 

[winston1]

The cables bringing the electrical supply go to the ceiling rose (so it is always live even when the light switch is off)

Not necessarily. The live can be looped at the switch with only switched live and neutral and CPC at the rose.

 

[JohnD]

Not necessarily.

yes, I know

but

My extra-sensory powers tell me that the OP has the ceiling rose method, or equivalent conections above the ceilig, rather the the Switch method. I expect he will confirm this later.

 

[JohnD]

With our bathroom door closed, our fan is inaudible -

Mine too. A Silent 100T.

very good fan.