Changing a ceiling light Ask questions and find answers to many subjects relating to electrics and electrical work

[IanJ99]

Hi, I'm trying to change a ceiling light. The new light fixture has a terminal block with three pins. When removing the old fixture however I found that there was an 8 pin terminal block with three lives, three neutrals and three earths. I wasn't expecting this many cables! As you might be able to tell, this is the first time I've come across this! Am i able to put all three lives into the one live pin on the new outlet and so on for the others or would this not work/is dangerous?

Thanks in advance, Ian

[Mr White]

It does not work how you think. The probability is you do not have 3 lives, 3 neutrals and 3 earths, what you have is called 3 plate wiring method. This forum has an indepth explanation, Click here

[ericmark]

The standard UK method is to use the ceiling rose as a junction box, in some other countries they use the switch back box as a junction box, there are pros and cons with each method.

So standard was three cables, two were red, black and earth, one was two reds and earth, so feed in, feed out to next lamp, and two reds to the switch, however when we changed colours to harmonise with Europe, and went to brown and blue, it seems we went from using two brown and earth but simply over sleeved the blue with brown sleeving, which often fell off, if it was ever fitted, but it allowed for having emergency lighting and ceiling fans, but having two lines together did allow some capacitive and induction leaking, and as we went to LED lights excessive runs to the switch as with two way lighting could cause the bulb to glow when off, or flash.

The use of smart switches designed for other countries has resulted in some electricians adopting the European methods, and we seem to get a lot of imports without the parking option for the non switched lines in the lamp. And the import of smart and dimming switches which require the neutral.

However the LP-link range of smart switches (Tapo) use a battery, and work A1 with UK system, and smart relays can be used in the lamp, also smart bulbs.

It is easy enough to with power turned off to clip the multi meter to each pair of cables and turn light switch on/off until you find the pair which works the meters built in buzzer, called belling out the cables. However it is surprising how many people attempt to work on electrics without any test equipment, one can also with power on test for live, however there is some danger with that, I would park each wire in a block connector to ensure one can't by accident touch a live cable. However this will identify the feed in, but you still have feed to next lamp, and feed to switch to work out, it is simple logic as to what cable does what, if you know which red pairs with which black (or brown/blue) but where all you have is the cores, not so easy.