24 hour timer on bathroom fan

[newbuyer17]

Fitted a more powerful inline fan to our ensuite, on a 20 min timer.
All good, but the missus is complaining its too loud in the middle of the night and runs for too long.

I want it to run for a decent time after a shower so dont want to turn the timer length down.

I'm considering running the live and neutral through a 24/7 immersion timer and setting it to on only during daytime hours. The switched live will stay as it is directly to the fan. This is all up in the loft out of the way.

Is this likely to case any issues? At some points the switched live will be live to the fan without any perm live or neutral? I dont see why this should matter, but thought I'd ask?

Thanks

 

[EFLImpudence]

That's all fine. Good idea.

The neutral isn't usually switched by the timer, anyway.

 

[JohnW2]

Is this likely to case any issues? At some points the switched live will be live to the fan without any perm live or neutral? I dont see why this should matter, but thought I'd ask?

As EFLI has said, that would be fine - and, as he also said, it's a very good idea, which has never occurred to me. We have quite a few people here proposing to go through all sorts of complicated contortions to avoid a light-triggered fan coming on at night, and this would be an ideal solution for many/most of them. I don't know why I never thought of it myself It does, of course, rely on their being somewhere convenient to locate and wire-in the timer.

The L & N supply to the timer do, of course, have to come from the same circuit as the switched live (i.e. the light).

Kind Regards, John

 

[EFLImpudence]

I don't know why I never thought of it myself

Nor I.

The L & N supply to the timer do, of course, have to come from the same circuit as the switched live (i.e. the light).

It will just be in-line.

 

[john4703]

I am in the process of redesigning my bathroom and am considering having one light that has a pir, at night just that one will come on, no fan, no switch and not too much light. I thought of a fitting like this one

 

[JohnW2]

I am in the process of redesigning my bathroom and am considering having one light that has a pir, at night just that one will come on, no fan, no switch and not too much light. I thought of a fitting like this one

That's fine, provide you can train/educate everyone not to use the light switch at night - and that's probably easier said than done, given that we tend to do such things automatically. The OP's idea, on the other hand, is more-or-less foolproof (except you might say 'too much light!).

Kind Regards, John

 

[newbuyer17]

Thanks all.

"The L & N supply to the timer do, of course, have to come from the same circuit as the switched live (i.e. the light)."

Just pondering this, the live and neutral to the timer would have to be permanently live. If I take it off the circuit after the lightswitch, then when the light is off the timer wont move and wont keep time?

So am I correct in saying:
1. The switched live comes from the lightswitch.
2. The live/neutral from the isolating switch on the fan in the loft will be permanently live, and taken from the circuit before the lightswitch??

i.e. I need to power the timer from the isolating switch, and have the output from the timer go to the fan permanent L/N?

Sorry if some of my terminilogy is a bit off.

Thanks

 

[JohnW2]

I don't know why I never thought of it myself

Nor I.

Quite - it's a pretty 'obvious' solution

The L & N supply to the timer do, of course, have to come from the same circuit as the switched live (i.e. the light).

It will just be in-line.

Yes, it should be. I added that bit just in case someone reading this thought that they would use some other supply which was 'convenient' to the location of the timer! That would, of course, work - but it would not be desirable, nor necessarily 'safe'.

Kind Regards, John

 

[tightasfcuk]

why not fit a humidistat fan?

 

[EFLImpudence]

why not fit a humidistat fan?

They don't work very well.

 

[tightasfcuk]

work better than a 24hour timer, wasting energy running a fan all day

and if set up properly then they work quite well

 

[JohnW2]

work better than a 24hour timer, wasting energy running a fan all day

That is not what is proposed. The fan will still only come on with the light (and for the timed period after light is switched off) - but only during the daytime.

Kind Regards, John

 

[tightasfcuk]

ok im wrong

 

[JohnW2]

ok im wrong

Indeed.

Another problem with humidistat fans is that they are not very sensitive to smells from loos. It's a bit frustrating to have an extractor fan, but one which can only be made to come on to extract odours by creating a lot of steam (waste of hot water!).

Kind Regards, John

 

[ericmark]

There are two reasons to include a timer.
1) To comply with building regulations.
2) To allow moisture and smells to be fully extracted before it turns off.

With the former there is no real option at to length of time it runs. However the regulations don't say it must come on with the light, in fact they say where there is day light there must be another way to switch on the fan without the light being used. This assumes the window does not open as if it does then no fan is required.

With the latter assuming there is no building regulation requiring the fan then you can do what you want. If you could trigger the fan only with a long flush or shower use that would be OK. "Ban all sheds" once showed a method using a double pole light switch and a push button so the fan could be activated during the day without using the lights.

One major problem with fans be it a tumble trier, kitchen or bathroom is what ever air it blown outside has to be replaced. My wife switches on the tumble drier then complains about the draft under the front door. She it seems wants to live in a vacuum. However in real terms unless a heat recovery unit is used then we have to consider how the air is replaced and what any depression may mean. If there are any open flue devices (which means they draw air from room rather than from outside not really having an open flue) then one has to ensure there is no depression caused.

All any fan required to comply with building regulations is a simple push button normally pneumatic which will activate the fan. With that method the user is in full control. To stop mould building up one could use a humidistat as well, which will not normally be triggered by use of the WC and I would assume you don't have a shower in the middle of the night?

Of course many just don't worry about the law, I have seen new houses where there is a non opening window in the bathroom and the fan is triggered by the light only. It seems no one really worries about what the regulations say they only worry about being caught.