Why has my new light fitting only got 2 earth wires and two black wires? What does black signify (live or neutral)? There are no blue or red wires.

Andrew, November 2008

A light bulb needs power on one wire and neutral on the other wire - a bulb is not polarised and does not care which is which - pendant lamp holders in the Uk usually have a Brown and a Blue wire and IF you have these colours you must make Brown the live wire but this can connect to either side of the lamp / lamp holder. You have two blacks to the lamps so it doesn't matter.

A simple light switch has power coming in on one wire (most often Red in the UK but slowly changing to Brown) and power going out to the light fitting on a DIFFERENT coloured wire - usually Black but slowly changing to Blue.

This switched live wire is very scary - you may think it's a neutral but it has the power to kill you when the switch is on - we are required to put a Red or Brown sleeve on it to show that it's dangerous.

At the ceiling you will most usually have power arriving on a Red wire which joins to the Red wire that goes off to the switch - sometimes a third Red going to the next ceiling rose but not always. There will be a Black neutral wire coming in with the arriving power cable and maybe another Black going to the next rose. There will also be the scary wire from the switch - The Black coloured Switched Live that should be identified with a Red or Brown sleeve. This is the power to the lamp holder and turns on and off with the switch - the other side of the lamp holder needs to be connected to a Black neutral to complete the circuit.

Stay Safe - call a sparky if in any doubt.

Peccavi, November 2008

How confusing is the answer below??

Are you talking about the light or what is in the ceiling?

Mr Handy Andy, November 2008

the two wires comming down from your (OLD LIGHT) are red and black . and is there a earth wire up there too , if so put the earth wire to the earth on the new fitting , and the black to the black, and the red to the (other ) black , have the mains off wile doing this work , and the light switch off too, if you think about it , when you put a bulb in how do you what is live or neutral, on the points of the bulb, just look at the old fitting and how its wired up and copy it , if there are 3 wires up there and two of them are twinded together , mark them , and keep them together, one of them is a switch wire, but make sure all the power if off at the mains first,

paul, November 2008