by ericmark »
Sun Feb 05, 2017 10:36 pm
First things first, do you need a fan, or is it just something you want, when I say need I mean to comply with building regulations?
It's all down to windows, if there are no windows then the fan can be controlled solely by lights.
If windows open it does not need a fan.
If it has windows which don't open then you must be able to switch on the fan without switching on the lights. With this scenario best option is likely a simple pneumatic push switch. To get it to switch with the lights plus have an independent method would mean a double pole switch for lights, so although same switch they are not electrical connected.
With all options likely the best option is a PIR to switch it on. Again no electrical connection to lights.
The 3 amp fuse is the preferred size, electricians carry 3 and 13 amp fuses and they are matched to wiring not the appliance. Although the fan manufacturer says 3A in real terms it will not protect the fan, the wiring is too thin in the motor so motor will burn out before fuse blows, with a 6A fuse in the lighting the 3A fuse will rupture first, but with a 6A MCB or RCBO likely they will open first so the 3A fuse is pointless. One is in theory allowed up to 16A for lights, as long as there are not any junction boxes etc which have a lower rating, and in the main ceiling roses are rated 6A so in real terms 6A is highest supply for lighting.
So in the main three pole isolator only is used, a FCU with 3A fuse is only used when supplied from power circuit.
The idea of three wires is the permanent line keeps fan running after lights are switched off, where a pneumatic time switch is used this is not required.
If when the house was built there was no fan, you don't need to fit one. Unless that is you change something like fitting a non opening window instead of a opening one. How one knows what happened in past I don't know?
The problem today is bathrooms require any new items to be RCD protected, this can make a simple job of fitting a fan more expensive, although a RCD FCU would seem easy way out.
If the pull cord does not work lights then reasonable easy, but if it also works lights crossing all t's and dotting all i's is not that easy. The guy before may have not been the cowboy he may have been following the rules.
Personally having a fan in bathroom is OK, but in the toilet it's a pain as you wake up house hold when you turn on loo light, same with PIR. So although we were forced to fit a fan by building control, as soon as we got the completion certificate the isolator was switched off and it was never used again.
If on leaving the toilet you could push a button and let fan run for 15 minutes that would be great, clears the steam without putting you in a draft, same would be good for under floor heating 1 hour after leaving to dry floor. Both are pointless while having the shower.
