Have i got a borrowed neutral

down2earth · Jul 9, 2009

Dear all,

I would be grateful for some advice, a friend has a redundanct lighting circuit that they want disabling so they can plaster over the old fitting holes on the wall, when i tested the circuit the switch wire (black wire red sleeve) only has power to it, there are two other live wires (from a 3 core and earth wire) going into the switch which have no power to them at all. My problem is finding where the switch wire is being fed from, is this what is known as a borrowed neutral and is there an easy way of finding where it is being fed from?
For background i have passed my 2382 exam but am lacking in practical experience (as is painfully obvious from this post

)

I will try and upload a picture later in the day.

Thankyou for any help

Down2earth.

Had8Lives · Jul 9, 2009

Sounds a bit like someones made the fittings unswitched. How many wires at your light fittings? How many wires at your switch?

down2earth · Jul 9, 2009

Sorry about the delay, just got in from work, there are 4 wires at the light switch (3 core and earth) so have the switched neutral, two red and the earth. At the fittings there are 3 wires, interestingly the switched neutral was in the 'C' bit of the dimmer switch which presumably backs up your non swithced theory.

Down2earth

chocolate · Jul 9, 2009

Would be interesting to see the pictures of the light fitting, and the light switch. My first thoughts are that if you have a black sleeved red, it is not a neutral but is the switched live coming from the switch and going to the light.

Sometimes, you find that wall switches have been wired in a way that takes power to the switch. So there'll be a power in ( to the switch ), and a power out ( from the switch and going off somewhere else ), and a switched live which goes from the load side of the switch to the wall lights.

Such a method of wiring would suggest there is a JB above the ceiling. But where ?

Really, if you can't remove the cables from these positions, and it sounds like without doing further investigation you can't disconnect them from wherever they come from, then they shouldn't be plastered over. Sounds stupid I know, but that cable end should be accessible simply because it is still connected. If you can't be 100% sure it is disconnected, then don't bury it. Doing so could create a bigger bag of trouble, at a later date.