Replacing a celing light

[mdkennedy]

Apologies if this has been covered in other posts but I looked and couldn't see a clear answer.

I have removed a celing rose and bought a new light fitting. I have 3 black, 3 red and an earth from the ceiling , the terminal block on the light has four holes one marked for Live, Neutral and Earth.

I have been told to wire the three red to the live and the three black to the blue with the earth clearly going to the earth.

Is this correct?

The light is in a circuit of three upstairs but is connected to a one way switch.

 

[breezer]

you have not looked that hard.
look in for refernce

 

[ban-all-sheds]

Apologies if this has been covered in other posts but I looked and couldn't see a clear answer.

Look again - it's in the For Reference topic

I have removed a celing rose and bought a new light fitting.

Did you make a note of which conductors went where?

I have 3 black, 3 red and an earth from the ceiling ,

Should be 3 earths. Can you see if what you've got are 3 twin&earth cables? You've probably got the classic loop-in, loop-out and switch cable wiring.

the terminal block on the light has four holes one marked for Live, Neutral and Earth.

Err - that's only 3, what's the 4th terminal for?

I have been told to wire the three red to the live and the three black to the blue with the earth clearly going to the earth.

Whoever told you that is playing a cruel and dangerous practical joke, or is a complete idiot.

Is this correct?

No - it'll result in a big flashbangfizzpop and the fuse/MCB blowing/tripping. One of the black cores will be a switched live, and connecting it to the other two, which are neutrals, is a Bad Thing™.

The question is, which is the switched live, and which are the neutrals? Armed with either the cables marked to say what went where on the ceiling rose or a knowledge of lighting circuits and a multimeter, it's a trivial question to answer. Without either of those you're going to regret going off half-cocked...

 

[mdkennedy]

I do appear to have three twin and earth cables but I have no indication of which is the switch (daft b*****d didn't note what went where. I have no red tag to identify it.

I think the black from switch the wire is to go to the live with the other two black to the neutral but do the three red then go into the fourth unmarked plug on the terminal block?

 

[andy]

I do appear to have three twin and earth cables but I have no indication of which is the switch (daft b*****d didn't note what went where. I have no red tag to identify it.

I think the black from switch the wire is to go to the live with the other two black to the neutral but do the three red then go into the fourth unmarked plug on the terminal block?

you will need to identify the switch cable. do u have a multimeter? if not, get one.

as for the wiring, its all in the reference section

 

[mdkennedy]

Thanks I've had a look but I can figure out which is the switched live its what I should be doing with the red wires thats confusingme.

 

[andy]

Thanks I've had a look but I can figure out which is the switched live its what I should be doing with the red wires thats confusingme.

you need a mulimeter to find the switch. if you dont hve 1, get 1.

for the reds - its all in the reference section. try lookihn

 

[ban-all-sheds]

The reds all go together - that's not the problem, they are all live, all the time.

Your problem is finding which black is not a neutral....

 

[mdkennedy]

So would it be fair to say the three reds can go togather in the spare slot on the terminal block and I just need to locate the switch cable and wire the black s upaccoringly from there

 

[andy]

So would it be fair to say the three reds can go togather in the spare slot on the terminal block and I just need to locate the switch cable and wire the black s upaccoringly from there

yes

 

[mdkennedy]

Okay thanks for all the help.

I've tried the three possible alternatives but with no success I'll have to get some one in to have a look asits also kncked out the bathroom and bedroom lights.

I can't seem to see whats wrong but I appreciate the help and advice posted

 

[andy]

Okay thanks for all the help.

I've tried the three possible alternatives but with no success I'll have to get some one in to have a look asits also kncked out the bathroom and bedroom lights.

I can't seem to see whats wrong but I appreciate the help and advice posted

well i kno whats wrong. u caused a direct short theu guess in the switch, which will have taken out the MCB or fuse

 

[mdkennedy]

S**t are u sure.

The same fuse I've been turning off whilst working on it controls the landing light but that works fine but is off when I switch the fuse.

Wouldn't it just pop out the fuse or will it be blown completely?

 

[andy]

S**t are u sure.

The same fuse I've been turning off whilst working on it controls the landing light but that works fine but is off when I switch the fuse.

Wouldn't it just pop out the fuse or will it be blown completely?

depends on how u wired it. get a multimeter to identify each cable BEFORE you do anything. any u wunder why accidents happen.

 

[Damocles]

If you have three cables then probably (probably!) that is one power in, one power out to next light, one to switch.

I don't know what you have done, but if you have somehow disconnected the power out, then you might have disconnected power to some of the lights on the circuit but others would still be fine.

If this was wired normally, then all reds connect together to one terminal. All earths to one terminal. Power in and power out black to one terminal...together with neutral for light. (might be black,or blue). Last black (which is sometimes identified by putting a bit of red sleeving around it) goes to a terminal together with live to lamp. (red or brown)

Now, mix them up and most likely is a big bang. But other interesting combinations are possible, including wiring this and next light is series.

Unforunately, the moral is to know all this before you take it apart, but anyway note very carefully how it was connected before. It is possible that you have something different to normal.