Bathroom extract fans-run on timers/light switch activated? Ask questions and find answers to many subjects relating to electrics and electrical work

[Sparkydelux]

Hi

Could someone shine the light on extract fans for me please.
1.Is there any rule that says extract fans have to have a run on timer?

I have always wired mine off the light radial.So basically,light on=fan on.Especially en-suite bathrooms due to the fact if you got to the toilet at night and switch on the light the fan kicks in and runs for ages whilst you are trying to get back to sleep.

2.I would also like to know how these are wired up.off the switch with a perm. power from the JB?

I would very much like to have a crash course in this please.

3.whats the story on the fan isolator?is it neccessary or is the light switch sufficient?

4.Extraction volumes for different rooms please?and minimum requirements.

All knowlegde passed on is greatly appreciated and invaluable.

Regards.

[sparx]

Hi, run-on timers are reqd. by bldg regs if room has no open vents or windows with 'trickle vents' fitted.
Wiring is easy from rose as you have perm. live, Neutral & sw. line there already, assuming 3 plate loop-in method used.
Fan isolator only required if fan is in a location without natural day light such as inline loft fitted type or if room has no window.
Reason being that if daylight available it is isolatable by locking off lighting circuit at con. unit. and servicing fan by daylight, if lights required to be on to service fan then an isolator is required in all 'Live poles' in this context Neutral is considered a 'Live conductor' hence triple pole fan switches, unofficially they are handy to stop fan at night!
Extract volumes are posted by bldg control site, and a call to say expelair/vent-axia/manrose or their web sites would probably give latest figures, hope this is what you are after,
regards SPARX