Bathroom extractor fan and dimmer

[gorstj]

Short version of question: can I use the dimmed output of a dimmer to connect to the switched live input of a timed extractor fan? The permanent live and neutral will not come from the dimmer switch (but will come fromt eh lighting circuit)

Long version.
Here is what I am going to use:
3 x mains halogens http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=101162&ts=14883&id=46943
1 x showerlite fan http://www.tlc-direct.co.uk/Products/BGSLC.html
1 x inline fan located in loft http://www.tlc-direct.co.uk/Products/BGCFD200T.html
1 x behind tile bathroom switch with momentary output http://www.sensor.co.uk/BathroomSwitch.htm
1 x X10 LD11 din rail dimmer

The theory is:
The 'behind tile' bathroom switch (it is a low voltage sensor with a control box in the loft) provides a momentary action switched outlet when the tile is pressed. This output is put into the LD11 dimmer. The dimmed output dims the mains halogen lights and the low voltage halogen transformer in the extractor light.
My question is can this dimmed output be used as the switched live for the timer extractor fan? (the permanent live and neutral will come directly from the un-dimmed lighting circuit)

If I activated the timed extractor fan from the momentary action output of the 'behind tile bathroom switch' then the fan will only stay on until e.g. 20mins after the lights were turned on. This is obviously a problem if someone is having a bath for 1 hour as I think the 'showerlite' needs to have the extractro fan in operation when it is working otherwise the low voltage light will over heat.

Many thanks for any help

 

[breezer]

it may backfeed through the fan and not dim the lights

 

[RF Lighting]

What about fitting a PIR to control the fan? You can get some very neat flush mounted ones, and also save a bit of money by buying a standard fan instead of a timer one (use the timer on the PIR instead)

 

[gorstj]

it may backfeed through the fan and not dim the lights

Do you mean that it will take the 'easiest' route and will therefore ignore the lights and run into the fan?

(excuse my ignorance, but I am not an electrician but will be getting an electrician to do the work but want to make sure what I am asking is possible!!)

 

[gorstj]

What about fitting a PIR to control the fan? You can get some very neat flush mounted ones, and also save a bit of money by buying a standard fan instead of a timer one (use the timer on the PIR instead)

Same problem. If the lights are left on but the fan switched off (i.e. no one in the bathroom) then the 'shower fan/light' may overheat.

 

[RF Lighting]

What you could do then is wire a relay in parallel with the fan across the output from the PIR, then wire the switch contacts of the relay between the output of the lighting transformer and the light that is built into the fan. This will mean the light in the fan will only come on if the fan is running, overcoming the problem of the lights being left on.