Bathroom Extractor Fan

[HandymanJohn]

Hi all

i'm in the process of buying and fitting and extractor fan for the bathroom and have a few quick questions about wiring.

i want the fan to operate with a timer via a pull switch that isn't connecdted to the light switch althou takes power from the light. I think i will need to fit a fan isolator switch too thou not sure

can't seem to get my head around how this will work, will i need to pull the pull cord twice to get it to work

also be grateful if anyone could provide a wiring diagram for this and guidance at to which pull switch is needed or if i can get an isolator pullswitch to save buying an extra isolator and running it from that.


cheers

john

 

[ericmark]

I think this RETRACTIVE CEILING SWITCH is what you want with the built in delay off timer in the fan. The normal way is with these they do not require timer in the fan the switch does it.

 

[ekmdgrf]

I think maybe you need to think about the theory of operation that your require and then build a system that does that, rather that assemble a bill of materials and see if it does what you want! Doubtless you can get the components to do whatever it is that you want to achieve.

I'm not 100% sure if you want a fan that will run while it's turned on and then for at extra n minutes when it's turned off or if you're looking for a system where you press a switch and that runs the fan n minutes? Both are possible.

First think about how a switch works: its just makes or breaks a circuit by connecting or disconnect a wire. Just imagine the fan as being a light fitting. You turn the switch and it turns the fan/light on. It's a little different with a fan, if it has a timer as you'll need to run a permanent line across as well as the switched.

Those three wires might need to go via an isolator. The toss has well and truly been argued over that here and on plenty of other forums. Some say it doesn't, some say only if you don't have a window in the bathroom, others say it depends on the house earthing system. The overwhelming consensus seems to be that it does require three pole isolation. The most common reason for that is "because that's the way it's done", followed by "because it's always been done like that". In 3rd place is a slightly more logical "so that you can isolate the fan if you need to replace it." Not entirely sure how you replace the light fittings though. About 0.1% of the time this argument kicks off you may see a few quotes from BS7671 to support both sides of the argument.

Hope that helps. I'm going to take a break for a few hours while the room clears of hornets.

 

[swampy2]

The triple pole fan isolator is for maintenance purposes, so fan can be worked on whilst leaving power onto lights in the same room.

 

[ericmark]

The standard fan isolator allows you to lock off the supply

with the attachment seen in red and the three connections are for permanent line, switched line and neutral switching neutral so with a fault you can work on it with light with out tripping RCD.

Where there is no natural light then using the light switch is OK and OK if window opens but you are correct if window does not open and there is natural light then the fan needs an independent method of switching it on. It can also be switched on with light but has to be something else as well. Double pole light switches one switching light and other fan is one way to use both methods to switch on fan as push switch is wired in parallel. In which case a standard FCU with 3A fuse used as an isolator.

There is debate as manufacturers often require it fusing to 3A if you need a FCU anyway! Personally I consider the 6A MCB for lights is good enough only where coming from a socket supply is the FCU needed and 3A is stated simply as it is a preferred size.

I think all rules are in Part F of building regulations the other consideration is where open flues are used. There must be some air allowed into the room to stop fumes being drawn into the house with an open flue.

 

[sparkwright]

So you want a timed fan that doesn't work in conjunction with the light.

All you need then is a separate pull switch in the bathroom, so you pull that switch; the fan comes on; pull the switch off; fan overuns for a few minutes.

Or you could have the switch outside the bathroom on the wall.

The switch would only cut the switch live. The cable to the fan needs to be permanent live, switched live, neutral, earth.

Depending on your wiring method, you would probably need a 3 pole fan switch to isolate the fan for the maintenance.

 

[PrenticeBoyofDerry]

Also you will need to read the manufacturer's instruction that come with the unit, as manufacturers seem to be stating that a 3A fused connection is used.

 

[AndyPRK]

A pull switch without a light could be a pain not knowing whether it is on or off