convert bathroom extractor fan?

[canitwork]

I'm so confused! Is it possible to convert a pull cord (ie manual) operation extractor fan to an automatic one? I'd like it to either
1. come on when the light is switched on/someone comes into the bathroom and then stay on for another 10 minutes after the light is switched off/motion ceases
or
2. be switched on and turn off automatically 10 minutes after the light is switched off/motion ceases

our bathroom has very poor ventilation and there is a real problem with damp - letting to tenants and not sure that they will remember to use the fan so option 1 is preferable...

I'd like to avoid wiring to the light and would like to use a light dependent resistor/motion sensor added to the existing unit...any thoughts?
much appreciated!

 

[ColJack]

1 and 2 are the exact same thing just worded differently..

it depends on the fan.. some you can just plug a timer module into, and providing you have the wiring there to support it ( ie 3 core and earth to supply a permanent live feed.. ) then it works just as you said..

alternatively, you could change the fan to one with an itegeral motion sensor, or one with a humidity stat....


the other method is to turn the fan on, cut the cord off so they can't turn it off, and fit a motion sensor in the ceiling and wire the fan feed through that..

 

[canitwork]

thanks for the reply
sorry, I meant in 2 that there would be manual switch on (by cord) with auto shut off - whilst in 1 auto switch on/off auto...anyways

your final suggestion implies chasing into the ceiling? which with our board and lath construction i'm keen to avoid.

so dependent on the wiring on the fan it should be ok to just pin a maplin type standard timer circuit into? do I need to clear that with building regs?

 

[ColJack]

not maplin type no.. it has to be the manufacturers module ...

if there no access to the roof above the bathroom?


it's easy enough to do... ( if you do that sort of thing all day that is.. )..

you take the light down and find the cable that goes to the fan, and try to determine approximately where it runs..

then you carefully drill a round hole into the ceiling and find the cable..

attatch a new length of wire to the existing one and feed it / pull both wires down the hole you just drilled.. ..

then you fit one of those round fast fix boxes into the hole, the type commonly used for fire detectors and such..

put your sensor on this.. ..

easy..

or most probably cheaper is to get a new fan with a sensor built in.. probably time for a new fan anyway...

 

[canitwork]

going to get a new fan with built in sensor! thanks for help.

 

[stem]

I've had one of these for years. It works great. Set to stay on for 12 minutes as it's not being triggered when someones in the shower behind the screen.

http://www.nuaire.co.uk/IandM/670610.pdf