Switching bathroom extractor fan with microwave detector.

[electricbill]

Hi all....

Quick question for you, what are your thoughts on the above?

I am looking for an alternate way to operate a bathroom extractor fan (don't want it on with the lights and don't want extra pull cords etc) - I propose to fit an inline fan in the loft, switched with a microwave sensor located above the shower cubicle ceiling....in the loft (with an isolator on RCD etc)

It's a bit of an experiment to see if it will work basically as an occupancy sensor when I use the shower.

My only concern is most microwave sensors have a load rating of around 1200w, but this would be for a resistive load and not an inductive load such as a fan.

In your opinions would a 1200w rated sensor be OK switching an inductive load of 35w?

Thanks - Bill

 

[Strima]

A humidistat would be better suited to this application.

 

[electricbill]

Hi - thanks...don't like humidistats, they never seem to work properly and are ugly too!

 

[Wilko]

Have a look at this one as an example. The stat is built in.
Silent 200 CHZ Extractor Fan with Shutter & Humidistat - https://www.tlc-direct.co.uk/Products/SLS200CHZ.html

 

[electricbill]

Thanks, but it is for an existing inline fan.

 

[Wilko]

Ok, got it
You are correct that motors have a higher starting current than run current. And give voltage spikes when the current is stopped. Starting should be ok, but the switching may not take the shut off unless designed for it. I have used them, but unless it's rated by manufacturer it's probably pot luck. Here's one that's designed for fans ...
Danlers PIR Occupancy Ceiling Switch - 10 Amps - https://www.tlc-direct.co.uk/Products/DNCEFLPIR10A.html

 

[electricbill]

Thanks....that's more the sort of thing, but needs to be microwave so I can put it above a plaster board ceiling and it won't be seen

 

[robd]

My experience of the microwave sensors is they aren't as particular about where you are when they pick you up and can be a bit over sensitive will be intetesting to see if it works how you want it though I do like the idea in principle.

 

[Risteard]

I would think the microwave detector would pick you up anywhere in the room.

 

[electricbill]

Possibly....I was actually going to experiment with a metal plate (with a hole in it) below the sensor so that it will only operate when you are directly below it. My only real issue is finding a suitable sensor....I don't know if a 1200w one for lighting will work.

 

[MisterE]

Take a look at a water controlled power switch :-
http://uk.rs-online.com/web/p/products/0256578/?grossPrice=Y
I used one on my shower to control the extractor.
It was replaced when I rewired but it worked.

 

[DPG]

Is your existing fan timer-controlled? If not then it won't remain on afterwards to clear things.

 

[D Skelton]

Mister E has the solution