Bathroom Extractor Fan Wiring

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aturi83

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Hi guys I'm after some advice on wiring for a humidistat extractor fan. The bathroom celling is being plastered tomorrow so want to run the cabling in place ready for it to be fitted next week.

I have led downlighters (bathroom rated) in place, switched outside the room.

So my plan is to run two 1.5mm 3 core cables into the loft space from where the fan will be located to allow connection next week. One wire to be connected to the lights (switched connection) - via the 3 pole isolator??

The other i was planning to run to a socket on the landing, connecting it to a 3 pole fan switch above the bathroom door.
 
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Why to the socket? The fan would normally run off the lighting circuit via an isolator (3 pole) and be fused down to 3 amp. If you want it coming on separately to the lights run a cable to the switch position & fit a double gang light switch.
 
Sounds as if you think you can connect the fan to both the lighting circuit and a socket circuit.

Please tell me I've misunderstood that.
 
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I thought it needed a permanent live via a socket in this case to allow self activation if the humidity was high enough and also for the timer run on. And then an optional switched live via the lights, to allow it to run for a preset amount of time.
 
At the end of the day do i need two wires running to where the fan will go, and should the wire be 2.5mm 3 core?
 
aturi83 said:
I thought it needed a permanent live via a socket in this case to allow self activation if the humidity was high enough and also for the timer run on. And then an optional switched live via the lights, to allow it to run for a preset amount of time.
Click to expand...
As BAS was implying, you must not 'mix circuits' like that. If (as would be the case) the switched-live is coming from a lighting circuit, the permanent live also needs to come from that same lighting circuit.

Kind Regards, John
 
aturi83 said:
At the end of the day do i need two wires running to where the fan will go, and should the wire be 2.5mm 3 core?
Click to expand...
If the fan is to be activated by the light as well as the humidistat, you will need 3 core + earth cable going to the fan (permanent live, switched live, neutral and earth).

Kind Regards, John
 
aturi83 said:
At the end of the day do i need two wires running to where the fan will go, and should the wire be 2.5mm 3 core?
Click to expand...

The live, neutral and switched live should all be from, or derived from, the same bathroom lighting circuit.

You dont need 2.5mm, 1mm will suffice.

I would imagine the instructions tell you to fuse down to 3A, though I doubt many do.

Take L and N from your lighting circuit to a 3 pole isolator, take your live from the switched side of the bathroom light switch to the same isolator. Connect from the isolator to the fan.

That will make the fan come on with the light, and by itself on high humidity.
 
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