Humidistat bathroom fan question

by **Mr Makeshift** » Sat Feb 12, 2011 11:39 pm

I have just installed (rather replaced as the old one was burnt out) a bathroom extractor with humidistat.
This is wired to the light switch and now comes on every time I turn the light on.
My question is, is this supposed to happen as what I wanted was for the fan only to operate when there is high humidity in the room eg when the shower is used.
I have adjusted the humidistat setting up to maximum 100% (so it is less sensitive) but cannot get it to remain off whenever the light is switched.

The reason I went for this type is that I thought it would only work when absolutely necessary and not whenever I just pop into the bathroom for a minute, otherwise I would have bought just a standard timer model.
Was I wrong in thinking this or is there some wiring issue?

by **stoneyboy** » Mon Feb 14, 2011 10:45 pm

Mr Makeshift,
Humidistat controlled fans will normally run for some time when powered up irrespective of humidity levels.
end

by **Mr Makeshift** » Tue Feb 22, 2011 12:37 pm

stoneyboy wrote:Mr Makeshift,
Humidistat controlled fans will normally run for some time when powered up irrespective of humidity levels.
end

Thanks (sort of). This doesn't really answer my question though. I know that they also have timers that will run on once the light is off. What I wanted to know was, is there a way for it NOT to come on EVERY TIME I turn on the bathroom light?

I think it's a case of not wiring it to the bathroom light switch. I thought that the humidistat function however would not allow the fan to operate when there is no moisture present, but it seems it doesn't unless it's re-wired.

by **stoneyboy** » Tue Feb 22, 2011 8:19 pm

Mr Makeshift,
To answer your question directly I have fitted both manrose and expelair extractors with humiditystats in bathrooms, both these turn on if the shower is used without the light being turned on. This does not mean that if you buy the same make they will have the same characteristics - manufacturers regularly change the design of their products. You are just going to have to try one and see if it does what you want.
end

by **Mr Makeshift** » Thu Feb 24, 2011 11:25 pm

I'm still not sure I fully understand. If I disconnect the wiring from the fan to the light switch will the unit then only come on when shower is in use?

by **stoneyboy** » Fri Feb 25, 2011 7:22 pm

Mr Makeshift,
Fit the fan with only a permanent live supply not a switched supply - the fan should have three connections L N and switched L, may also have earth.
end