Installing a new light.

Can someone explain as to why there are four lighting cables off the landing ceiling light and only three cables in all the other ceiling lights? We know on a regular ceiling light, two neutral, one switch and three ring and the three earth...how many are live on the one with the four cables coming out of the light? Any help would be greatly appreciated.

What colour wires are in these four cables and how are they connected in? It could just be someone has taken more than one loop out to supply other lights, there is more than one light switched the same time as the landing light or could be two way wiring.

Most likely the 4th cable is to power something in the loft such as a TV booster, or maybe you have a smoke alarm in the landing ceiling?

I'm not sure what you mean by "how many are live", but you should always assume that EVERY conductor has the ability to pass a potentially-lethal electric current until you can be sure otherwise. And yes that means the earths too.

What I mean by this is that if you have no proof that the wiring was done properly, you should, for safety's sake, assume that it could be done wrongly. So before doing any changes (if that's what you are proposing), check voltage and (with power off) continuity until you are happy that you know how it is wired.

where the condutors are connected should tell you what they do unless you've already disconnected them.

most likely the extra cable is taking a neutral and either a switched or unswitched live to another light fitting.

Got a light in the loft? Probably that.

Tayla