Nuisance tripping after splitting a ring main

[Mfctitch]

Evening everyone

Had to re post as I started a post within a post

here's hoping I'm posting in the right part or I have started off on the wrong foot.
Long story
Asked by a friend to look at his friends electrics as the kitchen ring was tripping the RCD.
New colours cable
on 32amp B MCB
one of only 3 on the this bank protected by an RCD
5 double sockets
plus a bank of 6 FCU's

Before I went there I had him remove all the plugs plus and turn off the FCU's
believing that this would help narrow down the problem.
But it did not.
so drove to Leytonstone about 45 mins from me
where we split the ring at a double socket and we believed that we had found a the problem which was a bit of cable in the wall between one of the FCU's and a socket in the cupboard.
all this time the other leg was working fine.
So we managed to replace the cable and we seemed to be on the home stretch, when the other leg started to trip I been there for about 5 hours and it was 9pm by now so turned the ring into a radial thinking this will do until I get time to investigate further.
so left at 10:30pm and everything seemed fine only to get a call today saying that the MCB had tripped but not the RCD and thoughts apart from run.

 

[snowhead]

Keep it simple.
Don't get distracted. (say he who's been off on many right, or is that wrong, tangents in the last 50 + years).

As has been said, put it back how it was, if possible.
Test from there to start, then split and follow the fault around the ring (or is it?) till you find it.

What you know is;
Splitting has now caused 2 apparent faults when you only had 1 to start with.
Replacing a section of cable has made no difference.
You've spent quite a bit of time getting nowhere.

 

[Mfctitch]

Keep it simple.
Don't get distracted. (say he who's been off on many right, or is that wrong, tangents in the last 50 + years).

As has been said, put it back how it was, if possible.
Test from there to start, then split and follow the fault around the ring (or is it?) till you find it.

What you know is;
Splitting has now caused 2 apparent faults when you only had 1 to start with.
Replacing a section of cable has made no difference.
You've spent quite a bit of time getting nowhere.
[/QU

Ha Ha
thanks for pointing out that i wasted Approximately 6 hours
but I've no one to blame but myself

 

[Mfctitch]

When you go back just put everything back to how it was.
Check all the terminations, inspect cables for damage..
With all appliances disconnected conduct an IR test between all cores and observe results.. Should hopefully be faulty. Next split the ring and test again. Carry on breaking the ring down and testing till you hopefully find the fault or even faults.

Afternoon
back at the job have split the ring at the point we believe is the last socket on the ring before going back to the board
everything disconnected and all FCU's turned off

results of IR @500v
short leg
L-N 999
N-E 999
L-E 0.05

on the long leg
L-N 0.04
N-E 0.14
L-E 0.01

any suggestion please

 

[Octopus]

Afternoon
back at the job have split the ring at the point we believe is the last socket on the ring before going back to the board
everything disconnected and all FCU's turned off

results of IR @500v
short leg
L-N 999
N-E 999
L-E 0.05

on the long leg
L-N 0.04
N-E 0.14
L-E 0.01

any suggestion please

Now the investigate starts .... both "legs" don't look too good

You need to take sockets off and break the long leg into half, then half again.

Tedious I know but the only sure fire way of investigating properly.

Also ask questions about water leaks, putting up pictures, rodents .........

 

[DPG]

At least you've got some good figures. Well, bad figures but at least they are bad enough to be traceable. Must be a couple ue of 'proper' faults there somewhere.

 

[Mfctitch]

Now the investigate starts .... both "legs" don't look too good

You need to take sockets off and break the long leg into half, then half again.

Tedious I know but the only sure fire way of investigating properly.

Also ask questions about water leaks, putting up pictures, rodents .........

update
split two legs in another socket and one one leg getting continuity between all 3
L-N
L-E
N-E
and the IR reading are 0.03 on all 3

 

[DPG]

Which leg is this on - the long or short?

 

[Mfctitch]

Which leg is this on - the long or short?

just finding that one out

 

[DPG]

just finding that one out

Don't you know which one you are working on?

 

[Octopus]

update
split two legs in another socket and one one leg getting continuity between all 3
L-N
L-E
N-E
and the IR reading are 0.03 on all 3

With that IR reading my guess is there is a load you're not aware of plus a L-N or N-E fault

Have you checked for outside sockets, lights, RCD sockets,

Is this the only socket circuit in the house?

 

[Mfctitch]

With that IR reading my guess is there is a load you're not aware of plus a L-N or N-E fault

Have you checked for outside sockets, lights, RCD sockets,

Is this the only socket circuit in the house?

It's the only circuit tripping and it runs the kitchen sockets and appliances

 

[Octopus]

It's the only circuit tripping and it runs the kitchen sockets and appliances

Have you checked the adjacent rooms? Cooker hood? sockets hidden behind pelmets, sitting in water leaking from the washing machine or dish washer ?

 

[DPG]

How many sockets in kitchen? Might be worth disconnecting them all one by one. Be quicker in long run probably.

 

[Mfctitch]

How many sockets in kitchen? Might be worth disconnecting them all one by one. Be quicker in long run probably.

it's looking that way 8 sockets and 6 FCU's

 

[Octopus]

it's looking that way 8 sockets and 6 FCU's

It is what it is!

If the customer wants it fixed, then they will see what your are having to do and then the bill won't come as a massive shock

How long has the kitchen been in?