Help needed trying to trace one of these neutral wires!!

tommyt02 · Jun 8, 2022

Hello all.

I am in the process of refurbing my kitchen and I have and old redundant T&E cable coming out of the wall above one of the cabinets which I think may still be live, despite recently replacing the kitchen switch cable and chopping out the extra single & earth cable which was once a switched line to this redundant cable for the old spotlights which were boxed in above the older pine cabinets before the kitchen was refurbed in about 2011. I chopped this single and earth cable out which ran along with the original red and black T&E switch feed, but I know that there will still be a neutral running through this redundant bit of cable as the lighting circuit has a single core (red) and earth feeding the fluorescent light, along with four single neutrals running into it (one of which will be feeding this redundant cable).

What I know about the single core wiring method is that all the line conductors are fed to the switch with one going to the light in the room along with two single neutral cores running from each fitting to the last on the circuit. Because of the layout of my property, we have a porch built onto the side of our house with lighting for the downstairs toilet and utility area, but because there is no upstairs on this part, I know that one of the 3/4 neutral cores will be carrying this spur to feed the last few lights in the porch area, but the real issue is trying to find which one feeds that redundant T&E cable which will probably be junctioned in one of those old crappy JB’s to these old singles below the bathroom floor which I cannot access at all.

The real question to this is, how can I find out which black single core cable to remove which runs to this redundant cable without trying to trace it back and rip down the ceiling to find it? Will I have to do some kind of testing or is it best to call someone out to help with this? As I am going to be changing the old fluorescent fitting for a modern one soon at some point.

Any advice / help will be much appreciated!
Regards Tom

littlespark · Jun 8, 2022

If you have access to both ends of the cable, which it looks like you do… then a continuity test can work out which of your wires is the redundant one.

tommyt02 · Jun 8, 2022

littlespark said:
If you have access to both ends of the cable, which it looks like you do… then a continuity test can work out which of your wires is the redundant one.

Thank you for the feedback. Do you reckon one of those cheapish digital electrical multimeters will be able to carry out the test if possible? Of course I am just trying to get to the bottom of this on a budget as I do not do electrics every day for a living - it’s just one of them small jobs I’m wanting to sort out so I can get rid of that particular cable.

Something like this I’ve attached below

swaRRR · Jun 9, 2022

Just check that the spec says 'continuity' and you're good to go.

timhoward · Jun 9, 2022

While there are a few ways a sparks could quickly and safely identify the right wire, I wouldn't encourage a less experienced person to try and do any continuity test with the power on.

I think one safe way for the OP to do this is with a temporary length of wire. Basically with the power completely off join the temporary wire to the redundant neutral and test the other end with each of the neutrals.

A completely different approach could be to acquire some wago connectors and systematically try 3 neutrals in one wago connector and the fourth in one on it's own. Obviously the power should be off when touching any wiring. When the rest of the downstairs lights still work the one on it's own should be the redundant one.

One question though, before anything is touched. If one of the neutrals feeds a redundant T+E cable, are you confident the live is still not connected somewhere, either at a switch, a light fitting, or another hidden junction?

SJD · Jun 9, 2022

As Tim says, even if you find the N cable at both ends that you think is redundant, how can you be sure there is not something else connected to it (e.g. via a junction box) that could become live when energised, e.g. another light. I'd be wary of disconnecting it without being totally sure it is not still connected to anything else.

tommyt02 · Jun 10, 2022

timhoward said:
While there are a few ways a sparks could quickly and safely identify the right wire, I wouldn't encourage a less experienced person to try and do any continuity test with the power on.

I think one safe way for the OP to do this is with a temporary length of wire. Basically with the power completely off join the temporary wire to the redundant neutral and test the other end with each of the neutrals.

A completely different approach could be to acquire some wago connectors and systematically try 3 neutrals in one wago connector and the fourth in one on it's own. Obviously the power should be off when touching any wiring. When the rest of the downstairs lights still work the one on it's own should be the redundant one.

One question though, before anything is touched. If one of the neutrals feeds a redundant T+E cable, are you confident the live is still not connected somewhere, either at a switch, a light fitting, or another hidden junction?

I would never proceed to carry out a continuity test while the lighting circuit’s still live or any circuit for that matter. I’ve been doing my own electrics for a few years now and I am quite competent and understand the risks involved.
That’s also what I have recently had a thought of doing - stripping back that redundant T&E cable to temporarily connect the neutral side to a longer piece of single core cable to reach over to all the neutrals at the light and carry out the continuity test. The fluorescent tube containing all the singles is only about a meter away from this redundant cable so it should not be too much of a problem.

I do have some wago connectors in a storage compartment in my organiser from previous wiring jobs (such as the 221 levers and the push fit variety) but in my opinion it would be a bit of a pain having to repeatedly run back and forth to turn the power on and off to test and single out the redundant neutral in that fashion, but thank you for that anyways!

Im also very confident that there will no longer be a live feeding that cable above the cupboard now because before I rewired the T&E switch feed and before I ripped the old stuff out, it also had a single red and earth acting as a switched live for those old spotlights which were ripped out long ago - so that single red became completely redundant with the wire chopped off and left in the back in the box and it was not connected to the 1 gang switch which replaced the 2 gang when the kitchen was refitted 10 years ago. The previous 2 gang switch had the T&E switch cable for the main kitchen light but there was a link in the common onto the second gang with the single formerly being the switching live for those spotlights. There will definitely be a junction box hidden somewhere above the kitchen ceiling containing that red single switched live and also one of those single neutrals coming from the main light fitting which will be terminated to that redundant T&E cable, so in that respect I am highly confident there will be no current flowing through the live conductor on that bit of cable - I am more concerned about the neutral conductor now and getting it sorted!

Thanks for your help
Regards

swaRRR · Jun 10, 2022

SJD said:
As Tim says, even if you find the N cable at both ends that you think is redundant, how can you be sure there is not something else connected to it (e.g. via a junction box) that could become live when energised, e.g. another light. I'd be wary of disconnecting it without being totally sure it is not still connected to anything else.

Could they not just disconnect both ends, check continuity, then energise CU and check for an AC feed on the neutral?

timhoward · Jun 10, 2022

swaRRR said:
Could they not just disconnect both ends, check continuity, then energise CU and check for an AC feed on the neutral?

There’s all sorts of things they could do. But I have two concerns
1 - there’s a limit to what I’ll advise someone to do on an Internet forum . Generally any live test is a no no. It does sound as though the OP in this case is informed and competent (and I didn’t want to suggest otherwise) but…
2 - I’m always very conscious that someone else less competent can read a thread like this and apply the advice to a completely different situation.
Hope that makes sense!

swaRRR · Jun 10, 2022

timhoward said:
There’s all sorts of things they could do. But I have two concerns
1 - there’s a limit to what I’ll advise someone to do on an Internet forum . Generally any live test is a no no. It does sound as though the OP in this case is informed and competent (and I didn’t want to suggest otherwise) but…
2 - I’m always very conscious that someone else less competent can read a thread like this and apply the advice to a completely different situation.
Hope that makes sense!

I see your point