Timed extractor fan or humidistat for en-suite?

[alan333]

Hi,

My en suite shower room has an extractor fan with a pull-cord switch on it, and an on/off switch outside the room.  It's not got a timer and we use the outside switch.  I'm looking at ways to have the fan run for a bit after a shower, but also be able to override it if I've just had a pre-bed shower and want it quiet. I also don't want it to come on automatically with the ceiling light.

If I fit a new fan with a timer would it begin it's timer sequence every time the outside switch was switched on, or does it need a permanent live feed and a separate activating supply?

Alternatively would a humidistat one be a better choice?  How do they work?  It senses humidity and switches itself on a timer, or until the humididty clears?  And does it only need a switched feed?

Also, how many litres/hour extraction rate do I need?  The room is approx 2.4 x 1.4 metres, and ceiling about 2.4 metres high, so approx 8 cubic metres (8000 litres).  The room also has a window with trickle vents.

Any help or recommendations welcome.

 

[Lectrician]

Humidistats can be problematic, unless you go for the expensive ones, such as the Vent Axia ambiend response one. That one is VERY accurate and turns on and off as you expect, with no false triggering. It needs to be sited between the source of steam and the air intake to the room (window or door) to be most effective.

I like to recommend flow switches too, placing a flow switch in the pipe to the shower, and having this control the fan. You turn the shower on, fan starts. You can either have this on a timer, or a humidistat too.

Search this forum for flow-switch, I am sure there was a large thread about it a little while ago.

 

[Simon35]

http://uk.rs-online.com/web/c/autom...0,4294965445&lastAttributeSelectedBlock=Brand