Adding a humidistat to fan and lighting circuit

Joined
30 Jan 2025
Messages
3
Reaction score
0
Country
United Kingdom
So I have a normal light switch & fan installation whereby you turn the light on and it also turns the inline extract fan in the loft on for a few minutes on the timer after the light switch has been switched off.

What I want to install is a humidistat that also turns on the fan when humidity is high say 85% and I still want to switch the fan on by the light switch, but I don’t want the humidistat to bring on the light when it is activated which is what would happen if it’s wired in parallel. Any time the SL of the humidistat is linked with the SL of the light switch and fan I’ll get this problem so I need a way around this.

What are my options to get this functionality?
 
Last edited:
Sponsored Links
What are my options to get this functionality?
Use a humidistat with a built in timer?

Something like...


Screenshot_20250130_224359_Adobe Acrobat.jpg

And convert your fan to non-timed operation, by linking both the L and T terminals at the fan, to the 'fan live' output of the humidistat.

Alternatively, if your humidistat has a SPDT relay...
Screenshot_20250130_225441_Adobe Acrobat.jpg

The Common could be connected to the fans switched live, the NC could connect to the lights switched live, and NO could be connected to a permanent live.
 
Last edited:
I’d still want to use the light switch to bring on the fan too in manual operation, would this be possible in this configuration?
 
Sponsored Links

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top