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Smart Home Forum by FIBARO Team

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Bathroom wiring (using Switch2 for extractor fan and dimmer-2 for spot lights)



What is the proper way to wire Bathroom lights with the extractor fan?


Current Situation:

Extractor Fan turns ON automatically when lights are turned ON and turns OFF when lights are OFF.


Desired Use case: 

Light should be able to turned ON without extractor fan. And extractor fan should turned on based on few conditions (e.g. based on humidity level or after 5 mins of lights turned on) and same for turning it off based on certain conditions.


Thanks in advance!

Edited by Hman
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3 answers to this question

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If you want to use humidity as an input, then I'd suggest using a dimmer for the lights, and a smart implant with a DHT22 sensor and slave relay for the fan. A slave relay is better because of the inductive fan load too.


Set up so a push button triggers a scene (the button could be connected to either device). The scene will turn on the light if it is off, turn it off if it is on. It can also turn on/off the fan based on the time delay logic you want.


A separate scene, that is always running, monitors the humidity and turns on the fan if above a certain threshold eg 80%, and off if below another eg 70% (use different values to avoid the fan turning on/off/on/off/on near the set point.)


Then you need to think about how to stop the two scenes interfering with each other. Eg the automatic scene will skip turning off the fan if the light is already on.

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(In UK)

What I ended up doing which works well, is a dimmer for the main lights. One switch module for the fan.

Keep the circuits completely separate. Don't wire them in like you'd do traditionally with a non-smart setup.

 Isolate the Switch module (and anything beyond it) with those Isolator switches that you would use in the UK.


Then use an automation routine (say using EventRunner4) with something like "if lights on, turn on fan" and "if lights off for 5 minutes, turn off fan".

If like me, you already bought a fan with a timer AND humidity control, don't worry you can still put that in. Your time will be increased by at least what you set on the fan itself.


As for the humidity setting, I whacked the humidity setting right up as i'm not interested in controlling via humidity. I don't care if the fan is on for 15 minutes after a shower for example. You'll forget about it eventually, as it just works :)

Edited by gurpal2000
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