Humidity setting in extractor fan

[henry1]

How do I set the humidity setting in my bathroom extractor fan? There's a tiny screw but it doesn't say how much to turn or how to end up at say 60%.

 

[Taylortwocities]

Make???
Model???

PS, check out the weather forecast. The forecast today is

that makes setting a fan to come on at 60% rather pointless. It will spend most of its time just running because that's what the weather is like in the UK.

 

[ericmark]

At 60% I would expect it would never turn off, sunny morning today outside is 60% the percent humidity is a problem, I convert to dew point to get a useful reading.

Temperature effect the percent humidity but it does not effect the dew point, with a fan running you are drawing in new air which is likely cold, so it is likely the fan is not running on percent humidity but some random unit which is enough to switch it off but does not relate to any fixed figure.

I have found the fans can run for an hour or so when set to switch off with humility, it is rather hit and miss, however the wet room with under floor heating is often still wet an hour after use, so very likely a couple of hours before it dries out. Do you really want the fan to run that long?

 

[endecotp]

The forecast today is (Humidity 56%)
that makes setting a fan to come on at 60% rather pointless.

That is the forecast OUTSIDE humidity.
The RELATIVE humidity of that air will be much less once it is inside and warmed up.
If it were 10 C outside and 20 C inside, the inside humidity with fresh air would be about 28%.

(I recall a similar post previously: https://www.diynot.com/diy/threads/will-it-work.477943/ . Do you not understand relative humidity?)

 

[endecotp]

How do I set the humidity setting in my bathroom extractor fan?

Trial and error. If it comes on when you don't want it, turn it one way; if it doesn't come on when you do want it, turn it the other way.
Turn it tiny amounts each time. Don't expect it to work perfectly.

 

[ericmark]

I was at one time very friendly with a woodland owner, and he was very interested in humidity, I spent ages working out how to convert relative humidity into dew point, it was an interesting project, and that is when I realised the problem with extractors, it depends where the replacement air comes from, in the house the air is warmer but has more moisture in it, from outside less moisture, but cooler.

There was a second problem, over 95% humidity and the digital meters started to miss behave, bring them in doors for a week or so they would dry out and start working again, but they would get stuck on 95%. If they hit 95% once in a while they are OK, but in the woodland it was regular, I found same in garden shed, and they had to be brought indoors and allowed to dry out.

Clearly this is a problem when the meter is built into the fan, the fan can run for days to dry out the sensor inside the fan. I think a simple timer is a better way.

 

[EFLImpudence]

PS, check out the weather forecast. The forecast today is View attachment 117972
that makes setting a fan to come on at 60% rather pointless. It will spend most of its time just running because that's what the weather is like in the UK.

That is the forecast OUTSIDE humidity.
The RELATIVE humidity of that air will be much less once it is inside and warmed up.

in the house the air is warmer but has more moisture in it, from outside less moisture, but cooler.

Do you not understand relative humidity?)

It may not be quite so straightforward.

 

[ericmark]

I used =IF(E2>0,D2-(100-E2)/5,"Fault") in excel where E = relative humidity, and D = temperature to give me the dew point which remains the same what ever the temperature. It may not be 100% accurate but is near enough for what I want.

Relative humidity is the percentage of moisture the air has in it compared to what it could hold, the if E2 is greater than 0°C is because at zero the air should not be able to hold any water, this is not strictly true, as it also depends on pressure, very often high up it is below zero but we see clouds of moisture.

One would expect when it's raining the relative humidity would be 100% however that is not always the case. So in the shower it is raining hot rain which will result in the RH being 100% as said this will mess up the sensor, if the fan is pumping out some air from the shower and some from the room then the mixture will be likely less than 100% RH so the sensor is OK, however if it draws it from very close to the shower it is being washed with water, this will mess up the sensor.

So fan in wall one meter from shower likely it will work, fan in ceiling above the shower likely it will fail.

 

[henry1]

Guys, 60% was just an example. My point is that there is no scale at all to even indicate what % I am setting the sensor to.
I guess it is trial and error.

 

[333rocky333]

Make???
Model???

 

[henry1]

Envirovent SILENT-150HT Extractor Fan with Humidistat / Timer for 6"/150mm duct

 

[ericmark]

Since it states 60 to 90% adjustable one would expect the adjustment to be reasonable liner through the range. However likely trail and error is best way to set.

 

[Taylortwocities]

How to adjust the humidity setting is in the user manual. Did you look there?
http://www.envirovent.com/product-downloads/SILENT_100_install_guide_1.pdf

 

[henry1]

Thanks for the manual. I didn't have it and didn't think of looking for it online using make and model. It only confirms what I thought though, that adjusting it to say 70% or 80% is a bit hit and miss.
By the way, I had a thermometer in my bedroom for some time that also gives a humidity reading. Humidity went as low as 50%. So for a bathroom in the same house, maybe 60% as a minimum doesn't sound too bad, assuming that 50% reading was correct. There's no window in the bathroom either, so airflow relies a lot on the fan.

 

[PrenticeBoyofDerry]

Thanks for the manual. I didn't have it and didn't think of looking for it online using make and model.

You didn't even think to offer up the make and model in your opening post, so how do you expect us to help you, if you cannot even be bothered to do that? Some people are just too lazy.

How do I set the humidity setting in my bathroom extractor fan? There's a tiny screw but it doesn't say how much to turn or how to end up at say 60%.

The trick is to read and understand the manufacturers instructions of the equipment you have, not all fans are the same make and model, therefore do not all adjust the same. So without this valued information, it would be impossible to help us or yourself.