by ericmark »
Thu Dec 13, 2018 4:07 pm
[attachment=0]lights.jpg[/attachment]What I would do is guess that they may be, then confirm if guess is correct.
So one cable has to be supply.
A second has to be switch.
Next we likely have supply to next light.
The three core and earth can have many uses, could be to second lights worked by same switch, but raises the question why would you want permanent line as second light.
There is a method of two way wiring where you use two x three core and earth cables one to each switch, but you only have one.
So power off you have to step by step identify the cables, easier if there is some one to help you, although a multi-meter with a buzzer is quite good at working out which is switch wire.
Basic it is using logic, inspection and testing, there is no quick way, removing switches and other ceiling roses you may see that red, yellow, blue and earth, but always test to see if it is the same cable.
I have included a picture that shows a few ways to wire, with a bathroom light that three core and earth could well be supply to fan, pictures are your friend, far easier to work things out from pictures then lengthy description.
I have already been banned from this site once for trying to help some one work out which wires are which without using a meter, and to be fair it is easy to miss read or forget to switch off or even switch off at wrong place.
Remember both line and neutral are considered live, although with a correctly wired house on a TN-C-S supply you should not get a shock from a neutral wire, I don't know if your house is TN, it could be TT so you could get a shock from the neutral. Also although against regulations, you do get from time to time borrowed neutrals, this means it may test as dead with a meter but when you disconnect it then it becomes line.
So safety first, switch off at main switch or RCD that is only way to turn off the neutral supply. Test with a voltage tester that does not require switching on/off and does not use batteries, ideal is using a proving unit, but so easy to have a meter switched to DC in error, or have battery go flat, so two prong voltage tester is safest tester for dead, however although not used to test for dead, a neon screwdriver has saved me from many a borrowed neutral.
I know it's Christmas but I want you safe, not lit up like Christmas lights.
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- How to wire lights.