I have recently had new plaster all downstairs and took all the light fittings off. When i came to put the lights up again i became confused with one particular light. One of the ceilling lights has a yellow wire were as the others have the usuall red,black and earth. The light in question seems to be some what providing power to the outside light that i have. Could this be what the yellow wire is for. The light in question as the following wires to connect 3 live, 3 neutral, 2 earth, 1 yellow and a black wire with a red sleeve. Any suggestions on this problem
As you say something wrong with count. There is no convention for using a triple and earth cable the colours are designed for three phase and using them for fans and two way wiring means unless notes are taken you need to look at other end to work out what it does.
The normal reason in a ceiling rose for using triple and earth cable is so both switched line and permanent line can be taken to a fan in bathroom. The cable is also used to wire central heating and between two switches when used as two way. There is a method of taking the two way cable vie the ceiling rose but it needs a joint in the ceiling rose so not very common.
The fact that you only have two earths makes one think this is a DIY job as I would hope electricians would not install any cables without earths.
As DIY people do all sorts of strange wiring and one I have seen is to use triple and earth between rose and switch and take a neutral to the switch so a second switch can be fitted to take power to items like outside lights.
As you can see there are many options and as a result we have no way that we can really answer all we can do is give pointers as to where to look.
I have even seen yellow used as an earth.
So sorry but ringing out the wires to find where each goes is really the only option.
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