Wiring wall lights, which is live and neutral?

[TheJay]

I have new two new wall light fittings to mount and have three cables coming out of the wall. Earth, live and neutral.

The light fitting only has live and neutral.

How do I identify which cable is live and which is neutral? Both of the cables are covered in black sheathing, so it's impossible to differentiate as you would usually when wiring a socket/plug.

FYI Both wall lights are operated by the same switch.



Can someone help please?

 

[littlespark]

I’ve been trying to understand that picture since yesterday.

Looks to me like grey sheathed singles.
Uninsulated cpc just twisted together.

Are you saying they are all black, under the grey sheath?

Did you take down old light fittings? How were they wired?


Technically, a standard light bulb can be wired either way round, so it wouldn’t matter… but as there’s 3 cables there, you can’t mix them up as you might have a live to neutral short.

Two of them look like they are twisted together… Keep them together!

 

[TheJay]

I’ve been trying to understand that picture since yesterday.

Looks to me like grey sheathed singles.
Uninsulated cpc just twisted together.

Are you saying they are all black, under the grey sheath?

Did you take down old light fittings? How were they wired?


Technically, a standard light bulb can be wired either way round, so it wouldn’t matter… but as there’s 3 cables there, you can’t mix them up as you might have a live to neutral short.

Two of them look like they are twisted together… Keep them together!

Thank you for your reply. Yes, under the grey is black. I did take down the old light fitting about 8 months ago and didn't take any photos annoyingly.

The third cable is definitely earth. The second terminates at the light. The first is twisted together. Could twisted be live and terminated be neutral?

 

[brianmoooore]

Methinks there might be some dubious wiring hidden behind that blue panel!
Time for a professional to investigate further.

 

[TheJay]

Methinks there might be some dubious wiring hidden behind that blue panel!
Time for a professional to investigate further.

Nope, we had a partial rewire done and all existing wiring circuits were checked when we moved in.

 

[brianmoooore]

I stand by my last post!.

 

[littlespark]

I’m afraid the only way to be sure is by testing with a voltage tester. Either two-prong or non contact.

I won’t go into how you do that until you can say if you’ve got one and know how to use it.

 

[TheJay]

I stand by my last post!.

I'm not sure why you are concerned. The bare twisted strands are from the original earthing cable. The twisted pair was connected to one terminal on the original wall light from the point the wire is exposed and the single at the end to the other terminal.

 

[TheJay]

I’m afraid the only way to be sure is by testing with a voltage tester. Either two-prong or non contact.

I won’t go into how you do that until you can say if you’ve got one and know how to use it.

I have a meter like this:

 

[brianmoooore]

Because you have single sheathed singles, all the same colour, apparently emerging from a void, plus a cpc that I wouldn't trust unless confirmed by testing.

 

[littlespark]

It’s unusual that sheathed singles were used anywhere domestically. It’s not 6241y, single and earth cable as the earths don’t look like they’re coming from the cable, but something behind the wall.
These earths need proved that they do actually go back to the fuse board.

It’s been a diy job when first put in, using whatever cable was available to be scrounged at the time.

So we can’t advise without testing. Only guess, which wouldn’t be smart.

 

[telectrix]

so after sleeving or taping the twisted earths, put the single cable in 1 light terminal, and the loop with the bit of insulation missing in the other. then if the new fitting is classI (metal with an earth terminal, connect the twisted earths to that).
1. it works..... hooray
2. it doesn't work........ aaaah shyte
3. it goes bang........ call in a sparks.

and that purple and white stripe is horrible.

 

[DefyG]

most likely scenario is neutrals twisted together and live conductor on its own (or vice versa) but as previous post advise to get it properly tested and cpc continuity confirmed even though it sounds like you have class 2 fittings now (ie no cpc needed at the fitting?).

 

[TheJay]

Thank you all for your replies.

The new light fittings are dimmable and the fitting type is E14 (SES). It doesn't come with a place to connect earth and there isn't any reference to earth in the instructions.

 

[littlespark]

If it has a “square within a square” icon on the box, then it’s double insulated and doesn’t need an earth, but make sure the cpc is connected through, just in case it’s supplying an earth to another point.

 

[brianmoooore]

so after sleeving or taping the twisted earths, put the single cable in 1 light terminal, and the loop with the bit of insulation missing in the other. then if the new fitting is classI (metal with an earth terminal, connect the twisted earths to that).
1. it works..... hooray
2. it doesn't work........ aaaah shyte
3. it goes bang........ call in a sparks.

Surprised to see a post like this from a esteemed professional! As I've posted on here before, we install electrics to fail, not just to work. Anyone, slightly above the level of idiot, can make electrics 'work' - it's what happens when things start to fail that's the difficult bit. To ensure that it disconnects itself in such a way as to present as little danger as possible to life or property.
The twisted earth is very likely to be more than one wire twisted together, so the integrity of the connection is important to maintain earthing to other parts of the circuit. Twisted wires are not sufficient.
1. "It works". Maybe it does, but what's going on behind the panel? More DIY twisted together wires, that may have been loosened by pulling the wires while attaching the new light?
2. Lucky! The fault happened right away, before it could start carbonising, destroying insulation, and potentially cause a fire.
3. The safest outcome.

 

[telectrix]

Thank you all for your replies.

The new light fittings are dimmable and the fitting type is E14 (SES). It doesn't come with a place to connect earth and there isn't any reference to earth in the instructions.

with E14 and E27 bases, it'sstandard practice to wire L to the centre contact and N to the outer. however, with the newer fittings, it does not matter so much as the thread is insulated from the supply cables

 

[TheJay]

with E14 and E27 bases, it'sstandard practice to wire L to the centre contact and N to the outer. however, with the newer fittings, it does not matter so much as the thread is insulated from the supply cables

I've just found details in the specification confirming that it is double insulated.

 

[timhoward]

Ok. I'll explain the concern.
The "partial rewire" would not have included these unless you moved in before 2004 as they are black sheathed. It's also not common way of doing domestic wiring, and hasn't been used that widely since the 70's/80's. I see cables like that in old schools / hospitals a lot, and occasionally in older houses.
All of this makes it look like this wiring hasn't been checked by a sparks, and a decent sparks wouldn't have left the earth wires like that.
Therefore we are concerned for your safety, and suggest you get a bit of help to help advance this project.
Contrary to rumours, most sparks aren't out to scam you, and this would be a quick visit. Many would not even charge for dropping by to help sort out what is going on. Whereabouts are you in the UK?

 

[TheJay]

Ok. I'll explain the concern.
The "partial rewire" would not have included these unless you moved in before 2004 as they are black sheathed. It's also not common way of doing domestic wiring, and hasn't been used that widely since the 70's/80's. I see cables like that in old schools / hospitals a lot, and occasionally in older houses.
All of this makes it look like this wiring hasn't been checked by a sparks, and a decent sparks wouldn't have left the earth wires like that.
Therefore we are concerned for your safety, and suggest you get a bit of help to help advance this project.
Contrary to rumours, most sparks aren't out to scam you, and this would be a quick visit. Many would not even charge for dropping by to help sort out what is going on. Whereabouts are you in the UK?

In Worcester

 

[TheJay]

You were right, live is single cable and neutral was twisted double.



Thank you for your help.

 

[brianmoooore]

The fact that something electrical works' does not necessarily mean it's safe. What have you done with the cpcs?

 

[MJPD29]

Nope, we had a partial rewire done and all existing wiring circuits were checked when we moved in.

Looks extremely dubious. All live conductors the same colour and earth's butchered. No half decent spark would have left anything like that.

 

[cloverman]

The fact that something electrical works' does not necessarily mean it's safe. What have you done with the cpcs?

It Works !!

The fact that something electrical works' does not necessarily mean it's safe. What have you done with the cpcs?

So I doubt you will get an answer to that question