At which point did this seem a good idea!

[phil d]

Did a board change for a mate,did a few tests beforehand and the results gave me the view that there would be no issue changing the board, it was a small terraced house with only 4 circuits, light up, lights down, one ring and a cooker. I went for a new board with RCBO's  as I didn't see the sense in using a split unit for 4 circuits. Anyway I fitted the board, everything checked out and away I went, later on that evening I get a call, there's something weird going on with the lights tripping the RCBO's. I immediately realised what I thought the problem was and  drove back to sort it. I was thinking borrowed neutral on the landing light, yes I know I should have checked.

I reset both breakers and tried all the lights, they all worked fine, no trip, which was exactly what it had done earlier when I checked everything, I switched everything back off and headed downstairs, at this point I realised I'd left the landing light on, switched it off and both breakers tripped out. I reset them and tried again, they only tripped when I operated the 2 way in a certain position, given the light worked fine at certain times and not at others I knew it couldn't be a borrowed neutral. Some fool had fed the landing light off the upstairs circuit,but had used a 2 core for the 2 way, the live for the bottom switch came off the downstairs lights. Now considering this house had been rewired about 20 years ago it was obvious that this had been wired like that at the time. At which point did they think it was a good idea to take 2 lives from 2 different fuses to feed each end of a 2 way circuit?

Imagine if someone had pulled the fuse for the upstairs lights, tested the fitting they were planning to work on, found it dead, and started work. If someone had then operated one of the 2 ways, they'd have put a voltage back on the circuit being worked on, with possibly fatal results. Ok I suppose with hindsight I should have remembered to check the 2 way and I didn't, but that still doesn't excuse the allegedly qualified spark who wired the place 20 years earlier.

 

[steptoe]

That's a standard borrowed neutral,

How else does it happen,?

You can't have two lives, you have one live and one switched,!

I'm failing to see how you ever checked for this in the first place, if toy even know how to,!!!!!! Going by your descriprion I'm not sure you actually understand just what a  borrowed 'neutral' actually is,,,,,, 

The only fool here is the fool that is slagging someone off for standard practice at the  time of install.

 

[leesparkykent]

^^^^The UK's friendliest electrical forum at its finest.........

 

[Andy™]

steps is right, there will be a 2 core going from the downstairs switch which has the 2 strappers. the perm live to them is fed from the downstaitrs lights, common of the upstairs switch then goes to light fitting, neutral then goes to upstairs. cant see any way that you could have 2 perm lives?

 

[phil d]

Well there was a live on the upstairs switch when either one of the breakers was off, dependent on the position of the 2 way switches,Incidently Stepps, there's no need to be so tango'd abusive, had a few beers had we? twat!

 

[Murdoch]

^^ steady  on boys...

.

 

[Lurch]

I'm on the "there is no way this that happened" side. If you have a twin as the strappers then there isn't a permanent live at each end.

You've misdiagnosed this one.

 

[steptoe]

OK, sorry @phil d

Just reading the post, and you slagging off someone else for what was a standard wiring method during 15th,,,,

I don't know how you checked for voltage at the upstairs switch, but I'll bet it was either backfeed or induced ,

 

[Sidewinder]

Steps,

It might have been a standard method, but, it was in breach of the IEE wiring regulations of the time.

The 15th actually prohibited sharing of neutral conductors.

 

[steptoe]

Steps,

It might have been a standard method, but, it was in breach of the IEE wiring regulations of the time.

The 15th actually prohibited sharing of neutral conductors.

Usually on the same fuse tho, 

We done loads of council new builds and all they had was sockets, kitchen sockets, cooker, immersion, lights, 

That's why loads of people get caught out doing CU replacements and splitting the lights into 2.

That was before 3core was ever used, in fact, GB is the only place in the world I've ever used 3c and earth,  

 

[phil d]

Steps sorry for sounding off at you, been a bad few days, shouldn't be on here really. Please accept my apologies. I,ve been trying to make sense of it,should have taken a pic.as I remember it there was defo a live coming up offthe downstairs circuit, why they did this and decided to  use two circuits is beyond me,however if you  switched off the upstairs breaker the lights would still work if the 2 ways were in a certain position. Anyway I ended up putting everything on one breaker for now.Not ideal but he'd recently decorated and didn't want a new chase to the downstairs switch. 

Anyway I'm taking a break for a few days, try and relax,all the  best Phil. 

 

[Andy™]

quite commonly and wrongly wired that way. of course the upstairs light still works when you turn off the upstairs circuit, you havent isolated the neutral. if you had used DP RCBO's then it wouldnt have worked, but it would also have made the neutral live

 

[steptoe]

Steps sorry for sounding off at you, been a bad few days, shouldn't be on here really. Please accept my apologies. I,ve been trying to make sense of it,should have taken a pic.as I remember it there was defo a live coming up offthe downstairs circuit, why they did this and decided to  use two circuits is beyond me,however if you  switched off the upstairs breaker the lights would still work if the 2 ways were in a certain position. Anyway I ended up putting everything on one breaker for now.Not ideal but he'd recently decorated and didn't want a new chase to the downstairs switch. 

Anyway I'm taking a break for a few days, try and relax,all the  best Phil. 

No offence taken Phil,

Reading my post back, it could have been worded a lot better, I struggle a bit with syntax sometimes. 

 

[Evans Electric]

Stepps ...you are a gentleman of the first order .....we can all be quick to sound off sometimes but the apology is the sign of the man :Salute

 

[Evans Electric]

Just to continue the subject ....  I wonder if there are any areas where the dreaded "borrowed"  neutral  does NOT occur . 

On board changes I'm usually amazed when the landing light is wired correctly .  

I visualise the original cause ..I think... House Basher Bill  is under pressure , as today  ,  to first fix new houses or rewire council houses,  in half an hour including travel time.

After doing smaller houses with only one light circuit  it becomes good practice to have two light circuits .........to save getting a neutral up from the ground floor ..ignore the regs and drop it into the nearest bedroom light.  

After a while it virtually became an industry "norm"  .

I only ever worked in Commercial & Industrial for years and came to house bashing later as "foreigners"  TBH   .  Distinctly remember someone warning me to pull BOTH lighting fuses in houses. 

 

[Andy™]

 Distinctly remember someone warning me to pull BOTH lighting fuses in houses. 

i always do. and check each neutral is still dead after they have been pulled apart

 

[Lurch]

I used to see the odd borrowed neutral from time to time when I was in Shrewsbury, usually in older properties where someone had done a board change and just stuck the 2 lives in 2 MCB's and called it done.

I have been doing a lot of work up north recently and have found pretty much every property with a borrowed neutral, even newer rewired places (as in maybe 90's era).

So it is quite common, but IME it seems to be lack of knowledge in some areas and just standard practice in others.

 

[rapparee]

^^^^The UK's friendliest electrical forum at its finest.........

Alright @steptoe

 

[Phoenix]

Like many others here, I couldn't quite work out what Phil was saying he'd found, it make not a lot of sense with the light having two permanent lives, etc. It came to me a bit later though. Its still a borrowed neutral situation, but slightly different to the normal one we encounter.

If you think of a standard conversion method 2way wired in 6243Y. With a switch drop from the landing light to the top switch and then the 6243y out and to the switch at the bottom. Now keep it wired the mostly the same, remove the core linking L1 to L1 on the two switches, which is in with the red permanent live of the switch drop at the top, you are now short of a permanent live to L1 at the bottom switch (but you of course still have one at the top), so that gets linked off the adjacent switch, which happens to be on a different circuit. Result, is it still borrows, (but only half the time), I suppose you could say its more of a borrowed live than a borrowed neutral!

 

[steptoe]

2 hours ago, rapparee said:

:slap

Not seen that before.....