Extractor Fan - How to?

[jockass]

I am looking to install an in-line extractor fan. It is double insulated and is going to be situated in the loft above the bathroom, the instructions that came with the fan say only a live and neutral feed are required. I have a double switch in my hall that controls both bathroom and hall lighting. I want the extractor to have a separate isolator switch that can operate only when the bathroom light is on and can be used to isolate the fan. I have attached a photo of the double switch and would like your suggestions on the best way to approach this job - View media item 25003
I am aware of part p regulations and am a competent diy'er!

 

[ericmark]

One would not wire from switch as there is normally no neutral at the switch. Sometimes double pole switches are used to enable fusing down to 3A.

Normally they have both switched and permanent line so they can continue to run for 15 minutes after lights are switched off.

Where required to comply with Part F often a pneumatic timing switch is used as where there is natural light combining fan with light switch will not comply.

 

[jockass]

Thanks - bathroom is naturally ventilated with a window. I just wanted to give it a hand when winter comes our way and it gets to cold to have the window open so thought i would go for a in-line fan that can be switched on when required. I take it the neutral feed should come from the lighting and the switched live via the switch here with an isolator in between.

 

[ericmark]

There are special isolators designed for fans which have three instead of two switches.

There are fans designed to reduce heat loss but the heat recovery units start at around the £400 mark.

The problem with any extractor fan is that it needs to draw air into the house from some where. This can easy be the flue and can result in CO2 being drawn into the house.

Of course the tumble drier is also a problem in the same way and they pump air out of the house which must be drawn in somewhere.

The whole idea of central heating is the air into and out of the boiler is all from/to outside and so they cause no drafts. The old open fire by putting the gases up the flue would draw loads of air in from outside.

So what we do is have a shower then open window so it does not cool rest of house.

I have seen so many houses where the fans have been fitted only to be turned off and never used.

 

[ban-all-sheds]

//www.diynot.com/wiki/electrics:lighting:fan

 

[OwainDIYer]

Hopefully your light is wired looped in at the ceiling rose (or equivalent) so you can pick up a switched live and a neutral there. Run to DP switch (a FCU fused at 3A would be fine) and then to the light.

switch/FCU should be in the loft near the fan.