Wiring Light (Strange Yellow Wire!)

[TW01]

Hi,

Wondering if anyone could help me out. I bought a metal pendant light to replace our existing plastic fitting. On opening the ceiling rose i was met with 3 cables going into one juinction box. Its wired as follows:

3 Reds into a junction box - No connection into light

3 Blues into junction box - Connected to Negative at light fitting.

2 Earths into junction box - No connection into light.

1 Yellow into junction box - Connected to live at light fitting.

Am i right in thinking that the yellow wire is the swithced live from the light switch?

I have included a diagram of how i think i should wire the new light. I would appreciate some advice. Thanks In advance.

Untitled

• TW01
• 16 Aug 2010
• 1

 

[ban-all-sheds]

If the light switches on and off then the yellow must be the switched live.

Your diagram might be right - have you looked at the switch to see what's there?

Is it by any chance a 2- or more gang switch? Neutrals aren't usually taken to switches with lighting circuits like yours, but if someone has added a light where the circuit didn't run, or wasn't accessible, e.g. an outside light, or switched sockets for table/standard lamps, then using 3C+E as a switch drop to take a neutral there is a common solution.

But in any event all you need to do is to connect your new light to the L/N/E used by the current one....

 

[holmslaw]

..

 

[MalcofArabia]

Well it certainly looks like that is the correct way it would be wired. A double check would be to remove the switch that controls the light and see if it's yellow in there.

Bit concerned about the colouring though. Not sure I've seen RED/BLUE cable outside of control cables. So that's unusual as Twin + Earth was always RED/BLACK in the old days and is now BROWN/BLUE. Looks like you got something else there.

Also that 3 core cable that is RED/BLUE/YELLOW could be the old 3 core+ Earth but missing the earth. If you have enough spare strip a little back and see if there is a bare copper wire, which should be connected to the other earths. Not forgetting to sleeve it YELLOW/GREEN

If there isn't a bare copper wire then you have pre dated 1966 cable that didn't put earths in twin cable. You may want to think about changing it if there isn't an earth. As it is replacing a cable and because it is not damaged you are technically suppose to certify it. On here we of course would always recommend you do that.

Also while you have the fitting down think about sleeving that yellow cable. It should be Brown but as the existing cables are red then a piece of red tape would suffice, or you could sleeve all the reds and yellow Brown.

Only other thing is, that earth on the two cables that have earth is it a sleeved bare wire, or does it have proper insulation??

 

[TW01]

Many thanks for the replys.

Apologies the wires may actually be red and black but i am at work so tyring to remember the colours! I definitely know it was 3 lives, 3 negatives and 2 earths plus the yellow switch wire.

The thing that threw me was the yellow switch wire as you have 2 lives coming from one cable, one red and one yellow? If there is no earth on the switching cable would that make the light fitting dangerous? The metal light has a seperate earth terminal screwed on to it that i will wire into the other 2 earths + the normal earth wire so would that make it safe?

I will check what is at the light switch end and see if the yellow cable appears as if not i will call in a professional. Although they all want to charge £50 call out fee for a 5 minutes job.


The Kitchen was re-wired recently and i have had a new circut breaker fitted so if it was to go wrong hopefully it will all cut out and then i will need to call in someone! Hopefully will be ok though.

Cheers.

 

[MalcofArabia]

[quote="MalcofArabia";p="1704302"

Also that 3 core cable that is RED/BLUE/YELLOW could be the old 3 core+ Earth but missing the earth. If you have enough spare strip a little back and see if there is a bare copper wire, which should be connected to the other earths. Not forgetting to sleeve it YELLOW/GREEN

Check to see if there is an earth as I said above. If you have a metal faceplate switch then you will need to Earth the plate. If the 3 core as no Earth connected then it will mostly like not have an earth down to the switch. Your way of lighting would take the earth from the rose down to the switch.

 

[TW01]

Thanks - I will double check tonight but i am almost 100% sure there was no earth on that cable.

You say my way of wiring would take the earth to the switch? I am sorry for my ignorance but is that not good then? The light will still be connected to the other 2 earth wires so do these not go back to the circut board?

My understanding would be that if you went through the switched live cable in the wall then that would be bad news as that cable is not earthed but the light fitting itself is earthed by the other 2 earted cables?

The light swicth itself that controls the porch light and hall light is plastic and not metal, not sure if that makes any difference.

My question is if no earth on 3rd cable is it still safe or should i leave it? I guess it would be no different to the current light only difference being this is a plastic pendant as opposed to a a metal light?

Thanks again for your help.

 

[TW01]

Also sorry just want to add someone at work has said that the 3 lives and the switched live wire all need to be wired togehter in the junction box?

This would seem to defeat the purpose of a switched live as the 3 reds are constantly live and you would not be able to turn the light off.

Am i right to wire the switched live and 3 loop lives seperatly as originally thought?
Thanks

 

[ban-all-sheds]

Ignore that someone - he's a plonker.

Of course switched lives should be separate from permanent ones, or the light will be on all of the time.

BTW - you haven't got 3 loop lives - at least one of them is a switch drop.

 

[TW01]

Ignore that someone - he's a plonker.

Of course switched lives should be separate from permanent ones, or the light will be on all of the time.

BTW - you haven't got 3 loop lives - at least one of them is a switch drop.

Thanks - I thought so, do you think it is safe without the switched wire being earthed?

Will the light fitting be ok just being earthed to the other 2 cables?

Many thanks.

 

[ban-all-sheds]

Oh Dear - I'm not on the ball today...

It seems odd that the switch cable has no earth, as the others do. It might be old cable, or it might be that someone has used the earth as a switched live - this is a no-no, and must be sorted out. Have a closer look and see, and also look at what's at the switch.

A simple lack of an earth at the switch means no metal switches.

The light will get its earth from the circuit cables

 

[TW01]

Ok Thanks, I'll double check tonight. If it has no earth i will still wire the light fitting as i guess its no different to whats already there and then i'll consult an electrician about getting an earthed wire put in.

Annoying thing is i just paid £1200 for an electrician to rewire the kitchen, check all the electrics and fit a new consumer unit! (its only a 1 bedroom flat!) I thought he would have checked the lighting circut as well!

Cheers.

 

[riveralt]

Annoying thing is i just paid £1200 for an electrician to rewire the kitchen, check all the electrics and fit a new consumer unit! (its only a 1 bedroom flat!) I thought he would have checked the lighting circut as well!

Cheers.

You don't say where this light is situated. If it is in the kitchen then get the electrician back because it would appear from your drawing that the kitchen lighting part of the rewire has been missed, in so much that the cables should now be brown and blue.

The electrician should have left you with an electrical installation certificate and a wiring/circuit diagram of which wires went where in relation to the work he completed. In fitting the consumer unit he should have tested all the circuits and included that information on the electrical installation certificate.

If the light is not in kitchen then provided the tests produced the correct readings then the electrician would not have touched your light.