Hi all,

As the designated 'family electrician' (I completed my 16th ed regs back in 1999 and havent done anything other than wire a plug since 2002!), I have been asked to help sort out the sister in laws new flat..

I have an issue whereby no lights work unless the entrance hall light is switched on. Looking at the ceiling rose for that particular light, I have a configuration with 5 'live' feeds, 2 in one terminal block, 3 in another.

I am assuming right now that the two should be your switch wire, and the three are your loop, and somewhere along the line they have been mixed up (so your loop circuit is dependant on the switch). Question I have is, as none of the 5 'lives' have been identified as switch wires, what is the procedure for 'belling out' to identify what is switch and what is loop?

I'm trying to remember whether this should be done through a continuity check, a resistance check, either or both to identify common and live switchwire, vs supply in and out!

Can anyone advise me a procedure - where I need to probe with the multimeter and readings I should expect to be able to trace what is what?

Thanks in advance for the help!

Mark

If, and I say IF it has been wired correctly in the first place you will have a loop in a loop out and a switch line. To identify the switch line turn off the power and check it is off with a volt meter at the ceiling rose. Connect an Ohm meter to both the black and red wires in each twin and earth in turn and turn the light switch on each time. The switch line will show a short circuit when the switch is in the on position. The black wire from the switch is the live return from the switch and should be sleeved to show it is a phase wire and NOT a neutral.

Look at this link

http://diydata.com/planning/electric_lights/electric_lights.php

Hope that helps

I would take the switch plate off the wall and identify the wiring colour first, as it could be wired in twin red and earth,
single red and earth and single red or red and black twin and earth.

Once you have seen what the wiring method is you can start to identify which wire is which at the rose by the above method.

As above, Mr. V Twin is quite right, there could be other colour wiring used. The principle is the same but just be aware of the possibility of different colours being used!

There is also more than one way to wire lighting circuits and I have only described the most common method used in domestic installations and made an assumption from what you have found in the rose. Just remember, always work safe and turn the power off. If you have doubts about what you are doing call in a professional!

[Edited on 20/11/12 by Strontium Dog]

Its VERY difficult to advise on light circuits due to the already mentioned Many ways of doing the actual circuits.
All the advice you need has been given. you just need to work out HOW its been wired.
I'd assume that its wired lived loops round the ceiling roses and twin ( reds or red and black t&e ) dropped down to the switches. Take of a switch plate and see whats there. Turn the power off seperate the cables and meter out to see whats live and what's a switchwire from the plate as a starting point. But Basically yes I'd agree that someones taken down a light fitting and rejoind the wires wrongly.

Cheers all, shall be dusting off the multimeter