Can I confirm how to test for and how to find a borrowed neutral?

[HappyHippyDad]

During some testing I found a N-E IR fault on the kitchen lights of 0.1Mohms. I also found a N-E IR fault on the ring sockets, again 0.1Mohms.

This could have been a coincidence, but I disconnected both neutrals from the neutral bar (i.e the kitchen lights and sockets) and tested between them. They showed continuity (0.97 ohms). Just FYI, there was no continuity with these neutrals to the neutrals of the other circuits.

This is a dual RCD board. K lights and sockets on the same side.

Does the fact the neutrals showed continuity mean this is a borrowed neutral? I have not come across continuity between neutrals before. Is this the correct test for them? Does it actually mean they are connected together somewhere, or am I missing other possibilities?

Also, as the neutrals have been connected together somewhere in the house between these 2 circuits, how do I find this join? The house is full of shoddy DIY alterations. I would like to offer at least a guess as to how you find this join, but for the life of me I cannot think of a way.

 

[westward10]

Yes, 0.1Mohms (with CPC's still in the bar)

No a continuity test between neutral/earth.

 

[Lucien Nunes]

This N-E test stuff is all old news, see my post #19. There is unusually low insulation resistance between neutral and earth but not a short, so whilst it needs finding it's not the reason that the two neutrals show a hard short together. It might be further evidence of some cables nailed together or co-located with the N-N problem though.

 

[Dave OCD]

Equally it could be a bodge by 'Mr Know All' the homeowner/ resident dinosaur, but he'll never admit to it...

 

[davesparks]

In your example. If the line had been taken from a switch on the lighting circuit and the neutral from a nearby socket, how would that show continuity between neutrals?

Sorry, that was my mistake, I didn't fully think that one through!

I was at the time bored at work watching the special effects people (plumbers) ruin a perfectly good stage floor with their rain effects.

 

[buzzlightyear]

I was at the time bored at work watching the special effects people (plumbers) ruin a perfectly good stage floor with their rain effects.

Was it raining men by the way.

 

[bigspark17]

Ive had 2 o these no so long ago.
One was a conservatory light where they had wired live from a nearby two way switch and taken the neutral from the socket below.
Second was kitchen under unit lights same wiring.
Id be looking around trying to spot the red flags first, opening some accesories should help you identify the culprit.

Good luck.

 

[Lucien Nunes]

This is different though. It's not a line from one circuit paired with a neutral from another, it's two different neutrals connected together. It's not something you would do even as a bodge and might be a true fault e.g. a screw through two cables.

 

[HappyHippyDad]

This is different though. It's not a line from one circuit paired with a neutral from another, it's two different neutrals connected together. It's not something you would do even as a bodge and might be a true fault e.g. a screw through two cables.

Absolutely possible, but just seems so unlikely. A screw passing perfectly through 2 cables, missing the earth on both (which is probably centred in the middle of the cable) and touching both neutrals.
I suppose it has to happen one in a million times, so perhaps this is it. I'd rather have won the lottery!

 

[SJD]

I'd say it is more likely to be some interesting DIY connecting things together that shouldn't be. You could run a sweepstake on the outcome!

 

[Midwest]

Absolutely possible, but just seems so unlikely. A screw passing perfectly through 2 cables, missing the earth on both (which is probably centred in the middle of the cable) and touching both neutrals.
I suppose it has to happen one in a million times, so perhaps this is it. I'd rather have won the lottery!

I had a lighting cable, a twin and earth used as a pair of strappers between 2 way switching, damaged by a nail for a dado rail. It nicked one of the strappers and caused a live to earth fault. Only the strapper was nicked, not the cpc. Fault finder was complicated by which where the two switches were operated.

 

[HappyHippyDad]

It's proving difficult getting a date to do the fault finding, so I'm afraid there won't be an update any time soon. I will update though when I've been back.

 

[westward10]

Leaving us hanging again some of us will be losing sleep

 

[bigspark17]

This is different though. It's not a line from one circuit paired with a neutral from another, it's two different neutrals connected together. It's not something you would do even as a bodge and might be a true fault e.g. a screw through two cables.

I dont think so! Keep taking the pills if you think a screw has gone through 2 different cables. Im assuming you dont do much domestic stuff.

 

[timhoward]

I dont think so! Keep taking the pills if you think a screw has gone through 2 different cables. Im assuming you dont do much domestic stuff.

What he means is there are two different scenarios:
A) no neutral there at all so one is stolen from elsewhere (like your conservatory light example)
B) two neutral conductors from different circuits are joined (what this thread is about and not really a borrowed neutral. All my ideas for what we could call this don’t get past the language filter….

 

[mainline]

I dont think so! Keep taking the pills if you think a screw has gone through 2 different cables. Im assuming you dont do much domestic stuff.

I've seen where someone has put two cables one on top of each other to save on clips, notched in under floorboards, so it's certainly possible.