Bathroom extractors with humidistats

I don't know for sure, but I assume that the humisistat would be in parallel with the timer, causing the fan to run whenever either or both of them required it.

I don't know the model you have in mind, but the Vent-Axia extractor fan which is in my en-suite bathroom - which comes on when the light is turned on and has a delay timer to keep it on for about 10 minutes after the light is turned off - seems to cope ok without a humidistat.

One thing I would say though: Mine is claimed to be silent and, on the lower of its two speeds, it *is* silent, but it's also useless. I needed to move an internal jumper in order to switch it to the higher speed - and it now works fine, but it's *not* silent!

If we need to go out in the night, we don't turn the light on - and so no fan noise. There's a streetlamp outside which provides sufficient light to see what we're doing.

Because I don't like fan noise at night I've always fitted two pull switches: one for the light and one for the fan. I'm puzzling over what to do this time. If the humidistat will switch the fan on automagically when the shower is used then (I think) I will still use two pull switches, but default to having the fan switch being on and leave the automagic electrons to do their work. There will be an isolator switch (because that's what the installation requirements will say) but it will be out of easy reach. Question is, how good are the humidistats?

Richard

Pretty good really. Ive had one on a (noisy) fan for 25 years and its Just Worked.

Another solution would be, for nighttime at least, to become what in Germany is termed a sitzpinkler:

The landlord, who was seeking €1,900 (£1400; $2,200), claimed the marble floor had been damaged by urine.

But the Duesseldorf judge ruled that the man's method was within cultural norms, saying "urinating standing up is still common practice".”

That's why you should fully carpet a toilet with shag-pile to mop up the mis-aimed urine. :) :)

What I hope to do is to leave the fan permanently powered and expect it to wake up when needed (day or night) - i.e. when someone has a shower - but not if someone just wanders in to the room to brush their teeth or to admire their grandfather/grandmother looking back at them in the mirror(!). In this situation I can't see why I would want a timer function if there is some hysteresis on the humidity detection level to stop it toggling ... hmmm, but perhaps that's partly why the timer is there. Can a humidistat be relied on to do what I want?

I have quite a large bathroom (room for a bath and a shower in opposite corners) and there is a humidistat controlled Vent-Axia fan which has a humidity setting knob which seems to go all the way between permanently off and permanently on with about 8 other numbered setting between. The fan has a pull chord override so that it can be switched on at lower levels of humidity than the control setting. That pull chord lights an indicator to show that the chord has been pulled and to revert to automatic it needs to be pulled again. I normally leave it so that the fan comes on at anything over 70% humidity (I have a cheap and cheerful humidity meter beside it and that is how I have established what setting of the fan control to use). That level seems to turn on the extractor regardless of whether the bath or the shower has been used. It can turn on when neither has been used if the atmospheric humidity is high, but it then draws air from inside the house to replace the air extracted and it doesn't stay on for long because the air in the rest of the house is drier than the outside air. It works completely independently of whether the light is on or off.

I don't regret going for the humidistat version instead of the timer version, and I would replace it with another humidistat one if the current one fails.

Yes - if all you want it for is to get rid of condensation - and you don't care about smells!

Thanks. The toilets are separate so it would only be the odd fart - I think we can cope with that :-)

My experience exactly. Mine turns on on a timer from the lights OR humidity

Another question - It seems that the environmental RH in the UK varies between 70% and 95% (and, I guess, gets close to 100% after a sustained period of rain) so what do humidistat-controlled fans do - run forever, but in vain?

If the air temperature in the bathroom is 15degC and at 100% humidity, meaning it will contain 15g of water vapour per cubic metre, a change in temperature to 25degC will mean that because at that temperature the air can hold ~25g per cubic metre, the RH will now be 15/25 = 60%

Keep the bathroom nice and warm.

That is my conclusion in that they're impossible to setup for all year round conditions. But then I only purchased a cheapish one. Nice idea though.

Air in a heated house should be drier in the Winter.

No. Because the house is always warmer/drier than outside.

My fan comes on on very heavy rain but it switches off after half an hour or so

?? We should have heating in the bathroom? Whatever next.

I'm now wondering whether it would be worth putting a flow switch on the cold feed to the shower and using this to trigger the extractor. It feels like this should be more reliable than a humidistat.

Surely if you do that, the extractor will turn off as soon as you turn the shower off. Ideally you want it to run for a while after that?