Shower extractor fan

[martin t]

Think I know the answer to this.

I'm fitting an extractor fan with timer in the bathroom, normally they are fitted via the lights, however I am fitting a pull cord dimmer switch, would this reduce the effectiveness of the fan too? If so what would the best way of wiring the fan up?

Thanks

[buildersmate]

The way the fans with timers work is with three wires - a permanent live, a switched live, and a neutral. The permanent live drives the fan at all times - even after the lights have been switched off (and the thing is running-on, on the timer). The switched live is connected to light live side. When the voltage hits 240V, the control circuit in the timer is switched on - this turns the fan on for a period ot time driven by the timer.
If you run the light on a dimmer circuit, the dimmer 'chops' the alternating voltage pattern so that the voltage still comes close to 240V, but the period within the 50Hz cycle over which voltage is present is reduced.
I think (but I am not sure - never tried it) that you will find that this chopped voltage pattern will still trigger the fan - try it, I do not see how you can do any harm.
At worst you may find that the fan does not switch at the lower settings of the dimmer.

[martin t]

Cheers Buildersmate i'll try it out, if I do find that it doesn't kick in on the lower settings of the dimmer I can always come up with another option although the dimmer does start at max wattage when first switched on, it only reduces if you keep the chord 'pulled down' I can always run another circuit into the bathroom if it comes to it.

[droopdrawers]

Can I ask why you would want a dimmer switch in the bathroom/shower room?

I always think you need all the light you can get in such a room



DD

[martin t]

3 downlighters @ 50W each ample for shaving etc, dimmer allows us to have a nice soak in the bath in a lower light level, saves on candles Droopdrawers :-)

Update on the extractor fan anyway - it's now operated via an Infrared sensor so dimmng the lights has no effect on its running speed.