Wiring Standard Extractor Fan In Bathroom

[marc_123]

Hi folks,
I have a standard (not timer) extractor fan that should come on when light cord is pulled. The mains cable to the fan has blue, red and yellow wiring and the fan has 2 black wires going into a junction box. I\\\'ve connected the red and yellow from mains to the junction box but the fan works when the lights are off then goes off when the lights are on! This may sound dumb to the experienced but is there something obvious I\\\'m missing?
Many thanks for any advice...

 

[dingbat]

Haha, yes, you've used the wrong cores. You have wired your fan up to live and switched live, which means that when the lights are on there is no potential difference between these conductors, but when you turn the lights off there is mains potential. (Although how the circuit is actually completed is a bit of a mystery)

What on earth made you decide which conductors to use in the first place, or was it a purely random choice? Whatever your logic, or lack of logic, it indicates that you really shouldn't be playing with electricity - somebody might get hurt.

You need the neutral - probably the blue conductor - and the switched live - probably the yellow. But you should identify exactly which is which before you start mucking about.

If you didn't understand this, it makes me wonder what else you may have done wrong. (terminations, means of isolation, marking of conductors and basic testing immediately spring to mind.) Please call somebody who does this for a living and get it done safely.

 

[marc_123]

Cheers for your help, I've isolated the permanent live and used switch live and neutral...all works now. Now all I need to do is sort out the hole in the ceiling(!)
M

 

[securespark]

I won't ask why there's a hole in the ceiling.....