Weird or old wiring on light fitting - please help!

[johncross85]

Hello!

I am in the process of changing a light fitting but the wiring does not seem to fit with any I can find a description of. Any help would be very much appreciated!

Through the ceiling there are two groups of wires. Group one has a red wire, a black wire and an earth (bare copper). Group 2 has another red wire and an earth (bare copper).

The light fitting has just two contacts. The black from group 1 and the red from group 2 are connected to one contact, and the red from group 1 is connected to the other contact.

The earths are cut back and connected to nothing. Neither of the two red wires have a jacket marking it as switched live.

My new light fitting has just blue (neutral), green (earth) and brown (live) contacts.

I just don't see how it should work. Why would both a red wire (presumably either live or switched live) be connected to the same contact as a black wire (presumably neutral)? and if I am to follow this and connect the red and black to one contact in the new fitting which would it be - blue (neutral) or brown (live)?

I've searched and searched online and can't seem to find a description of a similar set up and everyone I know who would probably know the answer is unavailable because it's Easter.

Any help much appreciated! I'll try to post a photo below as soon as I get my camera connected to my PC...

Thanks,

John

 

[EFLImpudence]

Well - nothing obvious springs to mind.

Pesumably the red and black (group 1) will be the switched live and neutral - although you never know.
I can't think why the other red would be connected to a neutral.

Could we please have a picture of the switch wiring.

Or - turn off power, remove the second red (group 2) and put it in a terminal block (just in case).
Turn on power and see what doesn't happen.

 

[johncross85]

It appears that while this light fitting is disconnected two more upstairs lights stop working but three others dont. I assume that the two that stop working are connected in series somehow. I've no idea if thats normal?

John

 

[securespark]

Not series, but the power may be connected to them from this light you have taken down.

The red may be a neutral (either not labelled or lost its tape) feeding the two lights that have gone out.

 

[securespark]

Also, you can't connect the new light fitting to this wiring unless the cpcs are connected to each other and are connected to an effective earth at the other end.

 

[EFLImpudence]

It appears that while this light fitting is disconnected two more upstairs lights stop working but three others dont. I assume that the two that stop working are connected in series somehow. I've no idea if thats normal?

Do you mean with the single red disconnected (as I suggested) and with this light still working?

What you describe is normal but the wiring is unusual.
There must be some junction boxes somewhere. perhaps someone has used the colours the wrong way round.
Unless you can test with a meter it is impossible to say.

 

[johncross85]

So it turns out that the red and black in group 1 are live and neutral and the other red is switched live. I wired live to live in the new fitting and black and switched live to neutral in the new fitting... Essentially replicating how the other fitting was wired.

It works fine, the other lights upstairs still work. All is good.

Thanks for the help!

John

 

[EFLImpudence]

So it turns out that the red and black in group 1 are live and neutral and the other red is switched live.

That cannot be correct.

I wired live to live in the new fitting and black and switched live to neutral in the new fitting... Essentially replicating how the other fitting was wired.

It works fine, the other lights upstairs still work. All is good.

If you have wired it the same as it has always been then it will work.

However, we are none the wiser.

 

[flameport]

I wired live to live in the new fitting and black and switched live to neutral in the new fitting... Essentially replicating how the other fitting was wired.

It works fine, the other lights upstairs still work. All is good.

All is NOT good, because you have ignored this:

Also, you can't connect the new light fitting to this wiring unless the cpcs are connected to each other and are connected to an effective earth at the other end.

Even if you did connect those bare copper wires to the earth terminal, there is no way to know if they are connected at the other end - given the unusual mess of the other wires, it is highly likely they are not.

3 wires at the light fitting would normally be where the line is looped at the switch, and neutrals are looped at the light fitting, the three wires at the light being 2x neutrals and a switched line.
However this doesn't fit what you have either because that would be wired as singles in conduit.

Your only safe option is to get an electrician to find out just what is going on with that wiring, and if those bare copper wires are actually connected to earth.