lighting wiring
- Thread starter rolydv
- Start date
You will need a mutimeter set to the lowest ohm (ˑΩ ) beep.
Turn off the main switch at the consumer unit and test the circuit is dead.
Select one of the cables at the ceiling and connect the meter probes to the Red and Black (or Brown and Blue if newer cable) wires.
Turn the light switch on and off. If the meter beeps correspondingly then this is the switch cable.
If not, try another of the cables - it's usually the last one.
Mark the cable.
If you don't have a meter you could test with a battery and bulb from a torch but it would be advisable to buy a meter for such work.
Turn off the main switch at the consumer unit and test the circuit is dead.
Select one of the cables at the ceiling and connect the meter probes to the Red and Black (or Brown and Blue if newer cable) wires.
Turn the light switch on and off. If the meter beeps correspondingly then this is the switch cable.
If not, try another of the cables - it's usually the last one.
Mark the cable.
If you don't have a meter you could test with a battery and bulb from a torch but it would be advisable to buy a meter for such work.
You can easily do this if you note where the wires go before they are disconnected!
Are we sure that the OP is talking about 3 cables, rather than 3 conductors? He asked how to identify the 'switch live' - your method will obviously just identify the cable from the switch.
Kind Regards, John
Not really. That's why I particularly mentioned 'cable' at every opportunity.
If the OP didn't mean what I thought then the method in the reply will be impossible to carry out.
However, from experience questioners usually call the cables wires.
If only three wires was actually meant then the answer is - what's the word? - red (or brown).
Fair enough. It was the fact that the question was about 'switch live' which got me wondering.
... or perhaps black (or blue), with a red (or brown) sleeve over it! {i don't know about you, but I always uses brown/red for the live feed to a switch and oversleeved blue/black for the 'switched live']
Kind Regards, John
Energise the circuit, use a volt stick and throw the switch. Maybe the core that has no voltage before the switch is thrown and voltage after the switch is thrown would be the SL
On an isolated circuit if the switch is on you will get continuity across the live / SL switch cable.
On the cores, red or brown should be live, black or blue should be SL with an over sleeve of red (on the black) or brown (on the blue). Depending on if cable is old or new colour code.
No, if only three wires they will be (switched) live, neutral and cpc.
There is a wink but still bad advice.Energise the circuit, use a volt stick and throw the switch. Maybe the core that has no voltage before the switch is thrown and voltage after the switch is thrown would be the SL
as above.
Should be but OP said not.
Yes, that's literally true - but if the whole story were that there were literally just three conductors in total (as you say, a (switched) live, neutral and CPC), then it's very hard to see why the OP would be needing to ask the question! I was thinking that, if he did mean 'wires' (rather than cables), he probably wan't counting the CPC in his 'three' (i.e. he had 3 insulated conductors, plus a CPC) - that's the only way I could see the question making sense (if we were talking of 'wires').
Kind Regards, John
We may never know.
Also - to some extent I think we may be excused for thinking that, at least some of the words, mean what they mean.
Wires instead of cables - fair enough.
Four instead of three - stretching the limit of language when expecting helpful answers.
Perhaps it's not a light after all.
Wires instead of cables - fair enough.
Four instead of three - stretching the limit of language when expecting helpful answers.
Perhaps it's not a light after all.
As you've said, we may never know. I have to keep coming back to the thing which caused me to wonder in the first place. As you say, 'wires' instead of 'cables' would certainly be fair enough - that is the language that all members of my imemdiate family would almost certaionly use. However, if he was talkiing about cables, what do you think he would have meant by 'switch live'?
Kind Regards, John
I presumed (is that different than 'assumed'?) that the OP knew enough that if the switched live were identified then the configuration of all the others would be apparent.
After all, all the other wires are grouped by colour.
After all, all the other wires are grouped by colour.
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