How to use an extractor fan with a dimmer switch?

[HappyHippyDad]

Evening all....

My son is 14, he seems to be taking ultra long baths and showers and the bath/shower room is drenched afterwards.

I have just bought a pretty good inline fan and was planning on fitting it on its own switch as the existing lights are on a dimmer. I would love the fan to come on with the lights so that it is guaranteed it comes on when he is bathing.

Is there any way of doing this on a dimmer? The dimmer will be staying as it's too bright at night when on full.

I thought I could install a standard plate switch which switches power to both the fan and the dimmer switch. in other words the dimmer switch doesn't get power unless the fan is on. However, this is too cumbersome. Is there any way the fan can work with a dimmer switch?

A few more questions..

What actually happens to a fan if you install it on a dimmer switch? I'm guessing it would work fine if the dimmer is on full, but problems occur if the dimmer is lowered? Would this be dangerous or would the fan just cease to work as it doesn't have the required voltage?

 

[Jamiecla84]

Yes, it can be done, but the dimmer module will need modification.

I initially tried to do this using the dimmed switch live from the dimmer to the SL of the fan. It sort of worked, but the fan took ages to be triggered, about a minute or more IIRC. Back to the drawing board.

The modification to the was easy enough to do, and worked perfectly. John Ward has a video on how to do it on old leading edge module, but the way I did it on a V-pro module was less faff. I'll PM you details.

Yes, it can be done, but the dimmer module will need modification.

I initially tried to do this using the dimmed switch live from the dimmer to the SL of the fan. It sort of worked, but the fan took ages to be triggered, about a minute or more IIRC. Back to the drawing board.

The modification to the was easy enough to do, and worked perfectly. John Ward has a video on how to do it on old leading edge module, but the way I did it on a V-pro module was less faff. I'll PM you details.

Hi can you please pm me how to do this with a v pro dimmer to control a vent axia inline fan. Thanks

 

[msibart]

Hi, I have a similar issue in that I want to be able to dim the lights but make sure teh fan comes on. It is a timer fan so I assume it has its own power supply as it runs for a while after the light goes off. The switch is a pull cord one. I was wondering if something like this would work as it monitors a traditional switch input. I would then set the dimmer intensity in the software. Quinetic 1 Amp WiFi Mini Wireless Switch/Dimmer Receiver | Quinetic (QURWM1) - https://www.tlc-direct.co.uk/Products/QURWM1.html

 

[Avo Mk8]

Hi, I have a similar issue in that I want to be able to dim the lights but make sure teh fan comes on. It is a timer fan so I assume it has its own power supply as it runs for a while after the light goes off. The switch is a pull cord one. I was wondering if something like this would work as it monitors a traditional switch input. I would then set the dimmer intensity in the software. Quinetic 1 Amp WiFi Mini Wireless Switch/Dimmer Receiver | Quinetic (QURWM1) - https://www.tlc-direct.co.uk/Products/QURWM1.html

You mean put it in the lighting circuit at the light (so not affecting the existing wiring to the fan)?
Yes I think that will work. The receiver needs neutral and permanent live as well as the feed from the switch - worth checking those are present at the light fitting (with a traditional ceiling rose arrangement they should be, otherwise you will need to get permanent L there)

 

[HappyHippyDad]

Update....

I have fitted the fan. It works just fine with the dimmer. As long as the lights are are least half full strength when you initially switch it on then the fan comes on. You can then dim the lights as much as you want as the PL keeps the fan going.

I guess if you dimmed them below half, the fan would switch off after the overrun, but the boy always has the lights full on and I only dim them that low when I need a quick visit to the loo in the night. In fact, it works perfectly as I don't want the fan to come on in the middle of the night.

I probably wouldn't suggest it to a customer though.

 

[smokester]

Much simpler method is to change the light switch to a rocker and install bulbs you can dim from your phone (wifi) or a remote. This is what I had to do in a basement gym that didn't have a switch live to the fan, and they wanted to work-out with mood lighting.

 

[Marvo]

Update....

I have fitted the fan. It works just fine with the dimmer. As long as the lights are are least half full strength when you initially switch it on then the fan comes on. You can then dim the lights as much as you want as the PL keeps the fan going.

I guess if you dimmed them below half, the fan would switch off after the overrun, but the boy always has the lights full on and I only dim them that low when I need a quick visit to the loo in the night. In fact, it works perfectly as I don't want the fan to come on in the middle of the night.

I probably wouldn't suggest it to a customer though.

If you have the dimmer on low and the fan doesn't start running then there's a good chance it's going to get hot very quickly. Most domestic fans motors are designed that their own internal impedance during a stall situation is high enough to keep the stall current (LRA) at a safe level and prevent thermal runaway that might lead to a fire, this is often referred to as 'impedance protected'. Most domestic fan motors should also have a thermal fuse on the motor windings to provide further protection against fire.

Problem is that if you're leaving any possibility of the fan being in a stall situation for any length of time you're relying on the fact the fan was well designed with good protection components which might be a bet I'd take with a good brand fan like an S&P or a Ziehl/EBM but probably not with a generic Chinese rebranded unit.