Tracing the layout of a lighting circuit

[Martin Pentreath]

Hi all,

I've just bought some wall lights to mount in alcoves which have languished in darkness for years. The wiring is already there, and the last I remember (c. 2003) it worked fine. However, I now find everything is dead, and what was going to be a one hour job is getting a lot more complicated.

What I'd like to do is to find out what the ends of the cables which I see poking out of the walls are connected to. I think I know which other lights are on the circuit, and they all work. I can easily unscrew all the ceiling roses and wall switches. I'm dimly aware that proper electricians go though some process of sending low currents down the cables and checking continuity so that they can map which cable goes where. Can anyone fill me in on the detail or point me in the right direction for an explanation, and tell me what the right tool is?

Cheers!

Martin

[NT]

Option A is a multimeter and a long wire. Power must be off on all circuits to use this, and mcbs switched off, then you can trace where the live wire goes using the low resistance range. Check the resistance from L to N on the circuit first, it needs to be not low. You may need to remove or switch off loads on the circuit to get this.

Option B is a flasher and a mains live wire detector. The flasher turns the mains on and off fequently, making the circuit easy to trace.

Option C is a signal generator and a sniffer. Feed hf signal down the live wire, then use the sniffer to locate where it runs. mcb of the circuit being tested must be off.

Option D is to switch all circuits off bar the one you want to trace, and test which lighting points are live. This does mean live working, which I dont recommend in this case.

If you're not familiar with these methods, I'd go with A.

NT

[John]

Option A is a multimeter and a long wire. Power must be off on all circuits to use this, and mcbs switched off, then you can trace where the live wire goes using the low resistance range. Check the resistance from L to N on the circuit first, it needs to be not low. You may need to remove or switch off loads on the circuit to get this.

Option B is a flasher and a mains live wire detector. The flasher turns the mains on and off fequently, making the circuit easy to trace.

Option C is a signal generator and a sniffer. Feed hf signal down the live wire, then use the sniffer to locate where it runs. mcb of the circuit being tested must be off.

Option D is to switch all circuits off bar the one you want to trace, and test which lighting points are live. This does mean live working, which I dont recommend in this case.

If you're not familiar with these methods, I'd go with A.

NT

My house has the Live going to one wall light position and the neutral going to the other - there is a twin cable running between both positions. It confused me at first.