Bathroom timed extractor fan wiring question

[Hibbo]

because then he would have a shared neutral..with the light circuit back feeding into the neutral of th heater circuit.

OK, I see. I thought it was normal practice to install extractor fans powered from a RFC, but switched by the lighting switched live. In fact I was going to start a thread asking this; does that constitute a borrowed nuetral and how would it affect the RCDs (assuming the circuits were on different RCDs). I had guessed that it wasn't an issue as the switched live would just be connected to a very high impedance solid-state input.


Is it normal to actually power the fan from the lighting circuit?

 

[Flybywyre]

If I understand that correctly then you are suggesting that I run another live connection from the permanent live on the light switch, through the trunking, and into the airing cupboard where I presume I will need to connect all three wires into a three pole isolator switch and then route them accordingly from there ?

 

[ColJack]

you already have a T+E in there from the switch to the light..
simply replace this with a 3C+E.. you then have all the wires you need at the light..
they you take a second 3C+E from the light to the fan via an isolator..

 

[Flybywyre]

As you have already realised household electrics are not my bag
Could you please explain the terms T+E & 3C+E ?
Thanks

 

[ColJack]

T+E = Twin and Earth..
A flat cable consisting of a red and black ( or brown and blue nowadays ) wire, and a bare copper wire, all enclosed in an overall grey ( or sometimes white ) sheath.
Sometimes for switch drops it is has red and red cables ( or brown and brown nowadays ), and a bare copper wire..

3C+E = 3 Core and Earth..
Same as above but with a red, blue and yellow ( or brown, black and grey nowadays ) wires as well as the bare copper wire..