Bathroom dimmer with timer fan

[PeatBog]

I went to a property last week where the lights had failed in the ensuite bathroom. The circuit was controlled by a dimmer and had two 12V downlights and a fan on the circuit. The downlights each had their own transformer. I didn't look too hard at the fan but there was no indication that it was not 240V, it was a timer fan and had a 3 pole isolator. I checked the dimmer and it had failed. So the fan appeared to have a dimmed switched live. Is this a normal arrangement? I guess the fan takes it's power from the permenant live connection so the switched live is justed used as signal for the switching. I have come across dimmers that have a non-dimmed output for use with, for example, a fan.

I did not like this arrangement so I changed the dimmer for a switch. The customer was keen to keep her dimmer, so I promised I would would check on the acceptability of this arrangement as it had been working ok for a number of years. Any views?

 

[lilman]

Try one of these - used them myself a while ago -

www.phaseliner.co.uk/PDF/SGD600L%20Installation%20Sheet.pdf

 

[PeatBog]

Yes, phaseliner are the ones I had seen before. However, to re-wire using a phaseliner would require an extra core from the switch drop - it is a tiled loft room, so I can't rewire the circuit without disturbing the the tiles. Does anyone have an opinion as to if the existing circuit ok with a dimmer, does anyone else routinely wire fans from a dimmer?

 

[steptoe]

a short answer would be no, you cant have a fan on a dimmer.

saying that, its very hard to tell without knowing the fan specs, or the dimmer specs either for that matter.

you cant just put a normal fan on a normal dimmer switch, if that is what you are asking,

would it be easier to change the fan to a humidistat one with pullcord?

 

[batty]

Now i have always thought as steps says but this was talked about a few years back it was decided as fan gets its switch from switched live and actually works through permanent live you are not actually dimming fan so it will work ok.

 

[PeatBog]

Thanks for the replies. I guess it is a case of it being against the manufacturers instructions but might work ok in reality (but may vary between fans due to specific design of each manufacturers electronics!).

I may give the client the choice in trying it - I suppose I would need to show a deviations on the MWC if I do try it.

Regards, Pete.

 

[Evans Electric]

How long has it been working like that , Peatbog?

And an enquiry to the fan manufacturer's rep. wouldn't go amiss.

It sounds like the dimmed sw/wire has been triggering the fan for a while.