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.

 

[Mfctitch]

the system had been energised for at least a day with all switches on but I will check thank you

 

[Jim_e_Jib]

Did you down rate the MCB when converting the circuit to a radial? If so, possibly something is being switched on that has a high start up current that is causing the MCB to trip?

 

[Mfctitch]

Did you downrate the MCB when converting to a radial? If so, possibly something is being switched on that has a high start up current that is causing the MCB to trip?

No as I did not have a 20 amp on the van at the time and I knew that I was going back there and that with the stuff he had running there was not a danger. Almost wish that was the case

 

[Mfctitch]

update on tripping
fridge and freezer were plugged into an extension lead which was plugged into a circuit that is controled by the other RCD at 9 am this morning and has not tripped but the orignal RCD tripped about 30 mins ago with nothing running in the kitchen.
Any thoughts please

 

[Marcus Vaughan]

Dead test results?

 

[Mfctitch]

Dead test results?

As i sheepishly had to admit earlier in this post because I'd asked to all the plugs to be removed and fCU's turned off and it was still tripping so assumed that it would be a a faulty piece of cable.
I know stupid mistake but hopfully one I'll learn from once this has been sorted

 

[Pete999]

As i sheepishly had to admit earlier in this post because I'd asked to all the plugs to be removed and fCU's turned off and it was still tripping so assumed that it would be a a faulty piece of cable.
I know stupid mistake but hopfully one I'll learn from once this has been sorted

Were the FCUs DP ??? that could/will be the cause of tripping with them in the off position, if they weren't, NE fault?????

 

[Mfctitch]

Were the FCUs DP ??? that could/will be the cause of tripping with them in the off position, if they weren't, NE fault?????

I'm going back there wednesday night after work so will double check
so far with the help of the forum I'm thinking of joining the ring back up and doing an
Ir test
and am wondering if its worth doing an R1 RN and R2 test on the ring
or to keep the two leg seperate as one leg trips the RCD straight away and the other leg takes nearly 10 hours to trip the RCD
if that make any sense

 

[DPG]

Write down all your results and post them on here.

 

[Mfctitch]

Write down all your results and post them on here.

I will do
now I know that taking short cuts has got me into this mess but what tests would be helpful for you to have and do you want them on the whole ring, the two separate legs or both ?

 

[SparkyAndGeorge]

Remove one leg from the board and split the circuit half way does it still trip?

 

[SparkyAndGeorge]

What are they using when the RCD trips?

 

[Charlie_]

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.

 

[Mfctitch]

Remove one leg from the board and split the circuit half way does it still trip?

Remove one leg from the board and split the circuit half way does it still trip?

The situation that we are in at the moment is that the RCD was tripping
we then split the legs at a socket
one leg seemed to be working fine
the problem seemed to be on the other leg between a socket in a cupboard and an FCU. we managed to replace that section of cable and all seemed ok with that leg.
then the leg that seemed ok started tripping the RCD so maybe in our ruch we got something wrong so ended up turning the ring into two radials.
the leg that started to trip was left disconnected and the other leg seemed fine only for me to be told that, that leg is now tripping the RCD after a few hours.
the fridge and the freezer which were on that leg are now being supplied from an extension lead which is plugged into the other bank of MCB's but the first RCD is still tripping after a few hours.
Hope that makes sense

 

[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.

will do as asked
and again thank you all for your understanding and patience with someone who cut corners