Extractor fan / lighting circuit / mains circuit/ isolation requirements

[SJRSJR]

Hello. I'm thinking about an extractor fan when refurbing a shower room. I won't be doing it myself but I want to understand the best way to achieve what I want/don't want given what I've already got:

I don't want the fan to come on every time the light comes on
I'd like a fan with a timer or humidistat.
I don't want a pull cord as a part of the solution.

Outside the shower room are three fused switches on a ring circuit at knee level. None are currently in use.

Is a 3 pole isolation switch always required?
Does a 3 pole isolation switch mean you can wire the fan into the lighting circuit but keep the fan off even when the light is on?
If so, could you have the fan on when the light is off?
If so, does it mean running 3 core & E from the lighting circuit to the isolation switch to the fan?
Could one of the fused switches be taken off the ring and used as the isolation switch? (Handy as it's at knee level)
Is there a simpler way - e.g. what would be required to run it off the ring circuit?

I just want to be able to control the fan irrespective of the light being on or off (and no pull cord!)

Thanks in advance

 

[Murdochcat]

I would recommend you fit a fan with a timer ….. and if wired sensibly a fan isolation switch can prove useful

 

[Taylortwocities]

First off. If you want the fan to come on with the light, at any time, then you need to power the fan from the lighting circuit.

Outside the shower room are three fused switches on a ring circuit at knee level

What circuit(s) are these powered by? It may not be practical to use these if they are on a sockets circuit.

I don't want the fan to come on every time the light comes on

Hmm. Maybe a better list of your wants might help. It would be reasonable easy for you to have a single switch that switches the fan on, independently of the light. But you might want to have a press (momentary) switch for the fan. The the fan would then run for , say, 15 minutes from when you press the button. Of course, that isn't so good if you are going to have a steamy shower that lasts for 30minutes!

You could have a standard switch to turn the fan on but you are then relying on whoever turned the fan on to turn the switch off. In my experience, nobody does!

I'd like a fan with a timer or humidistat.

You can get fans with both but (warning) in my experience humidity sensors are very hit and miss. They often have two modes:
run all the time or do not run when the room is steamy.

I don't want a pull cord as a part of the solution.

You dont need to have one.

Is a 3 pole isolation switch always required?

No. Its there to isolate the fan if it needs maintenance. it is not meant to be a fan on/off switch. Its not obligatory.

I won't be doing it myself

There are many options and ways to do this. You really need to get your chosen electrician on site and talk it through with them.

EDIT
There are some interesting smart fans about. Have a look at this beauty

Lo-Carbon Svara White | Vent-Axia

www.vent-axia.com

It has an app and you can set it up so it doesnt run at night times, etc. But it has a price!

 

[EFLImpudence]

Hello. I'm thinking about an extractor fan when refurbing a shower room.

Does that mean you do not have a fan at present?

If so, are you having problems which mean a fan is necessary?

 

[Harry Bloomfield]

You could have a standard switch to turn the fan on but you are then relying on whoever turned the fan on to turn the switch off. In my experience, nobody does!

A push button timer, would achieve that.

 

[Taylortwocities]

A push button timer, would achieve that.

Yes, but as i have pointed out, you'd need to nip out to push de button again once the timer has run out, if you were in there for a long time.

 

[Harry Bloomfield]

Yes, but as i have pointed out, you'd need to nip out to push de button again once the timer has run out, if you were in there for a long time.

Only other way, would be to have a push button, powering a PIR, detecting there is still a presence - with the PIR resetting the time period. All becoming rather complex for the OP's needs>

 

[SJRSJR]

Thanks for the quick replies:

If you want the fan to come on with the light, at any time, then you need to power the fan from the lighting circuit.

I don't so I guess that means I could run off either?

What circuit(s) are these powered by? It may not be practical to use these if they are on a sockets circuit.

The 3 fused switches are their own circuit at the CU - the lighting, extractor fan, towel rail and wall heater were all on it. The lighting has since been put on the upstairs lighting circuit.

It would be reasonable easy for you to have a single switch that switches the fan on, independently of the light.

Yes, that's what I want, how would it work given I want it to have a timer and not be a straight on/off (I taken your point on avoiding humidistats, that's fine).

Does that mean you do not have a fan at present?

If so, are you having problems which mean a fan is necessary?

Before my time it was a shower room with an extractor fan but no window. There aren't any signs of previous ventilation problems but I'm refurbing and having a window installed anyway because I don't like windowless rooms and I want natural light.

There are some interesting smart fans about. Have a look at this beauty

Like you say, it's pricey - it's not the main bathroom and the most fancy thing I want is a timer!

A push button timer, would achieve that.

Only other way, would be to have a push button, powering a PIR, detecting there is still a presence - with the PIR resetting the time period. All becoming rather complex for the OP's needs>

Yes, I don't want to over complicate it. I know how it'll be used - it's a small room, there'll be no lingering in a long hot shower, window open when in use, fan on to clear the humidity.

There are many options and ways to do this. You really need to get your chosen electrician on site and talk it through with them.

The electrician thinks I should have the fan come on every time the light comes on. That might be the most usual but it doesn't suit me, which is why I'm keen to explore the alternatives, the suggestions on this forum have always been very good for that. Thanks.

 

[Harry Bloomfield]

The electrician thinks I should have the fan come on every time the light comes on. That might be the most usual but it doesn't suit me, which is why I'm keen to explore the alternatives, the suggestions on this forum have always been very good for that. Thanks.

The operation mode you are proposing, likely involves it being forgotten to be turned on, when needed, and the possibility of forgetting to turn it off, after use. I personally don't like fans which only come on when the light is turned on, because often there is no need for the light to be turned on at all.

What I settled on, was one which ran on either high humidity, or a PIR, with an option to trigger from the light, but a delay to off timer, once triggered. I never bothered with the light trigger, it was unnecessary. You walk in the bathroom, anytime at all day, or night, once triggered it stays on for 20 minutes, since the last trigger - longer if the room is especially humid. It's only 20w, fairly quiet, so no reason for it not to run.

 

[SJRSJR]

Yes, I agree. That's why I don't want it to come on with the light. But equally I don't want it to come on and run for 20 minutes every time I walk in.

So I'm thinking a master switch outside which will turn it off altogether - perhaps one of the 3 fused switches? Then perhaps a two-gang light switch - one for the light and one for the fan. So:
light on when I only pop in
fan on when a light isn't needed
both on when it's dark and the shower is on.

As I understand it, a permanent live would be needed for the timer? Is that do able? Thanks

 

[Murdochcat]

Yes, I agree. That's why I don't want it to come on with the light. But equally I don't want it to come on and run for 20 minutes every time I walk in.

So I'm thinking a master switch outside which will turn it off altogether - perhaps one of the 3 fused switches? Then perhaps a two-gang light switch - one for the light and one for the fan. So:
light on when I only pop in
fan on when a light isn't needed
both on when it's dark and the shower is on.

As I understand it, a permanent live would be needed for the timer? Is that do able? Thanks

Just get it wired properly with a fan isolation switch

 

[SJRSJR]

So can one of the three fused switches be changed for an isolation switch (presumably put on the lighting circuit?) and the on/off control added to a 2 gang light switch?

If someone could tell me what I have to spell out to the electrician so I get what I want (rather than what he thinks I should have) that would be appreciated!

 

[EFLImpudence]

If someone could tell me what I have to spell out to the electrician so I get what I want

Tell him what you want.

 

[Murdochcat]

Tell him what you want.

Hit, nail and head springs to mind

eyes on site trump random internet advice

 

[Harry Bloomfield]

Yes, I agree. That's why I don't want it to come on with the light. But equally I don't want it to come on and run for 20 minutes every time I walk in.

Explain why, please?

So I'm thinking a master switch outside which will turn it off altogether - perhaps one of the 3 fused switches? Then perhaps a two-gang light switch - one for the light and one for the fan. So:
light on when I only pop in
fan on when a light isn't needed
both on when it's dark and the shower is on.

A switch, means it could be left on and forgotten. A push-button, could be used to trigger the timer to run for say 20 minutes. I still say - automatic PIR triggering is best. No action needed for anyone to remember to turn on, or off.