Bathroom lights with fan

I’m going to post this in the UK forum as this has seemingly UK-specific wiring details… I’m not sure US houses often have an extractor fan wired in tandem to the bathroom lights, and I’ll probably also have to deal with the lack of neutral cables.

So most of my house has got dumb light switches and Hue bulbs - the family is now used to leaving light switches on and using motion or Hue dimmers to turn lights on. This works well… almost too well, since I’ve got a couple of lights that are currently dumb switches and dumb bulbs and they get left on all the time because everyone is out of the habit of turning lights off!

So I want to upgrade a bathroom and ensuite toilet to Smart lighting. However, if I just put in some connected GU10s like Hue or IKEA, then I’ll leave the switch on 24/7 and this will mean my bathroom extractor fan is also running constantly although the lights can turn on and off with motion.

Does anyone know if the Fibaro module that fits behind a light switch can also run an extractor fan? I’m not clued up on electronics enough to know the difference between inductive and resistive loads, and whether this would be a problem.
I’m thinking of having a motion sensor that then tells ST to turn on the Fibaro module, turning the lights and the fan on. that way if they still hit the button through habit, it works, and if they forget to turn it off I can switch off 5 minutes after motion stops.

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Thanks for the reply. It’s quite a good setup that, I like the idea of dimming the lights (for relaxing baths instead of messing around with candles) but sounds like the cost comes in fairly high if I’m doing that twice, for two extractors in two rooms. I could leave the en-suite as a straightforward relay as I’m not fussed about that dimming.

So Fibaro modules are definitely able to switch an extractor on and off then? You’ve had no problems?

The fan unit is mains, although I’ve not had it apart to see if the motor itself is hooked up via a transformer. There’s no control boxes on the wall, just a regular 240v isolator switch on the outside of the bathroom.

I use Fibaro Dimmer 2’s in my bathrooms with GU10 LED downlights and extractor fans. The extractor fans have their own power, but are connected to the lighting circuit as a trigger to turn on the fan. The particular ones I have seem to activate at around 30% on the lighting circuit. It all works well.


Aaah that’s useful, I hadn’t considered it was a low-current trigger rather than just wired in parallel.
So actually, that means if I turn the lights on to 20% for relaxing bath or night-time toilet visits, the (really noisy) fan won’t activate. Bonus!

No, it’ll be 240V but it’ll be low current - so I don’t have to worry about whether the Fibaro can provide that much, unlike if it was wired in parallel to the lighting. I think the relays are 1.5KW aren’t they?

Thanks for the advice so far, there’s no makers name on the fan unit so I’ll have a look behind it, and at the wiring behind the isolator and light switch to see what I can see.

Hi all just jumping on top of this but seems to be a few of you who know a fair amount about this kind of setup.

i have a dimmer 2 module which i haven’t fitted yet as i was a little confused and after reading about burning the fan out i’m unsure what kind of setup i have. I’m hoping its the kind that just uses a low current to active the Fan.

There are x3 Gu10s in the ceiling which im hoping is why there are x3 wires that go into com1 on the light switch are the 3 gu10 lights and the black wire in l1 goes to the fan .

Thank you for the detailed answer , i will give this a crack this weekend now i know the logic i was assuming was correct has been confirmed by yourself. Thanks again great help

How would you go about it if you wanted to use a Fibaro relay switch to turn the fan on and off instead of the switch wire in to the fan?

Thanks Robin,

I would like to be able to dim the lights so they come on very low for night time visits to the bathroom. Not have the fan come on at night, and or have it based on humidity rather than the fan’s built in timer.

Here is the wiring diagram for my fan. It has a timer feature set by default to 15 minutes. Can I turn the timer down to 1 or 0 minutes and have a relay just turn the fan on and off? If so how would I connect it?


L to L1 is bridged to have the fan come on low speed. I’m not sure if mine is set to low or high.

so not do good news , i fitted the Fibaro as instructed and the lights came on , however when i turned the isolator switch on (which is the bang in the video) the lights flicker and the fibaro has a red light which goes on and off inline with the lights. I also wasn’t able to pair the Fibaro but i only attempted a couple of times as i didn’t think it would make a difference.

The light setup is x3 Gu10 leds 5watt bulbs , my thinking is maybe thats what the red light is or the reason the fan doesn’t come on ? Although the fan comes on with the normal switch attached so cant imagine its the load unless the fibaro lowers it?20170810_182331

Video is here in the google link

The bang was me flipping the switch so that’s nothing to worry about.

Yep literally followed every little bit even using the earth function on the fibaro .

Switch works fine now I’ve put it all back .

I wonder if the blinking lights is the fibaro working out what load is needed ? I’ve seen that a bit online when its first fitted. Although the red light on the fibaro isn’t normal is it ?

Not sure what I could wire via a plug socket but could try a simple light switch ie just 2 cables

Yes the flashing is when Fibaro works out how to dim the lights (leading or trailing edge dimmer, plus what % timing results in no light/full light). That said it should be more smooth than that… Do you definitely have dimmable LEDs?

I believe red normally means that the load is not behaving in a way that the Fibaro understands or can deal with - that may include having no load (Ive had mine flash red with no load). That could be because the LEDs are not dimmable and it could be because the fan is presenting a weird load. Does it behave differently with the isolator on and off? If you turn off the isolator you should not have any problems… For a quick test that should work.

Can anyone help suggest a solution to try and make the light and fan smart? I have purchased a Fibaro FGS 212 Relay Switch and would like to control both the fan and light with it. I don’t mind about using a physical light switch and can leave this on all the time providing the fan and light and be turned off with the Fibaro. Thanks for any knowledge!

Thanks Robin for your help. I did try a Fibaro 2 Dimmer with a Fibaro Dimmer 2 Bypass but it would not stop flickering despite trying to hold the b button until it was red and clicking to calibrate it. Any ideas? The bulbs were GU10 LEDs and non dimmable. I could perhaps try a standard B22 or E27 fitting?

With the FGS 212, could I potentially use this in my bathroom for the fan? The fan is in the loft so would have to wire it up there and it is connected to the lighting circuit. I also have an FGS 223 and could use that maybe instead?

Thanks for your help again.

Thanks and I’ll try a Fibaro Dimmer 2 again.

With the fan I was mentioning, this in the bathroom (so not the one you saw previously). Here are some photos and I believe the wiring should be accessible from the loft. Again, the fan is triggered by the light switch as with the other setup.

Ideally though, I would like to avoid going into the loft and a Fibaro 2 Dimmer would be easier I guess as long as the fan would work. The fan is 7.5w in terms of power.

Thanks again for both replies. I will try a Fibaro Dimmer 2 on both setups (to avoid going into the loft!). Another option would be to use both a Fibaro Dimmer 2 and an FGS 212 in tandem (bathroom)? But I don’t think it’s possible as the fan relies on the light switch being on.

Thanks again for your help! I will give it a go this Sunday perhaps and report back! Cheers

Hi Robin! After managing to get into the loft, big success! I managed to install the FGS 212 and the bathroom fan is now smart! Your instructions worked a treat. I did the same for the other fan with an FGS 223 and that worked too! Very happy indeed and big thanks for your help. No more fan in the night!

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