Strange RCD Fault

[Guest569]

80amp main switch RCD, occasionally trips when a couple of circuits are switched on (doesn't matter which circuits) with nothing plugged in.

IR tests all good. Replaced RCD for new. Happens in all weather ( don't think its external )

Only sockets on this consumer unit.

Ive had my guys out at it twice with no joy. New build wiring from 16th edition.

Im going to investigate myself this week, Im sure Ive had loose connections causing tripping before, it about all I can think of, a loose tail somewhere around the main switch.


Anything else to look out for ?

Im pretty certain its not a dodgy nail at floorboard etc its fairly new property and in good condition with chipboard throughout.

 

[Guest569]

jrc, you said in an earlier post that it appeared circuit legs of rfc and immersion has got mixed up. if that's the case, then doing end/end continuity and sorting it out may go a long way to finding the fault.

Ye

Yeah Hopefully , The spare 2.5 is just dangling LIVE (found out the hard way). The immerser breaker on the other board with one cable coming from it isolates it !


Organising the circuits and RCBOs to solve accumulative leakage hopefully solve it !

 

[jackhammerJIM]

I'm confused .

is it a ring or 2 radials ?

 

[Octopus]

I had a similar one a while back - very occasional tripping of a 16th Ed board with an upfront RCD. After 3 visits and absolutely no pattern to the tripping, I changed the RCD.

What I noticed was that the ramp test showed very different results on different days.

This was about 2 years ago and I've done other work in the house since and the RCD trip was completely eliminated. The RCD in question was a 100 mA

 

[Guest569]

I'm confused .

is it a ring or 2 radials ?

Im assuming its supposed to be a ring, both routes go to one end socket and it had 2 cables in 32amp breaker at board. It should be a ring but it looks like its diverting somewhere else! Possible indian ring with botched job to fix it.

 

[Guest569]

I had a similar one a while back - very occasional tripping of a 16th Ed board with an upfront RCD. After 3 visits and absolutely no pattern to the tripping, I changed the RCD.

What I noticed was that the ramp test showed very different results on different days.

This was about 2 years ago and I've done other work in the house since and the RCD trip was completely eliminated. The RCD in question was a 100 mA

Have installed a new RCD already but still same problem....

Im convinced there is multiple problems which is making things difficult .

 

[jackhammerJIM]

Im assuming its supposed to be a ring, both routes go to one end socket and it had 2 cables in 32amp breaker at board. It should be a ring but it looks like its diverting somewhere else! Possible indian ring with botched job to fix it.

what were the end to end continuity readings ???

 

[Guest569]

what were the end to end continuity readings ???

>2000Mohms!

It should be a ring but definitely not. I think one side is fed from elsewhere but hard to say with no access to trace out cables...Ill check again on monday incase Ive grabbed the wrong cable but I could get no continuity readings on the ring yet it was belling out! Confused.

 

[Guest569]

1k no one ? ;p

 

[jackhammerJIM]

your confusing me again . what do you mean by belling out ?

 

[R G]

Sounds like this fault has been there since day 1 , Take along 20 Amp Rcbos as well on Monday in case you can't get ring continuity ….What A Job ...

 

[jackhammerJIM]

and what model is the metrel tester ?

 

[Dcf]

new build? no ring continuity?
look for a socket thats been missed out
should be able to tell from a quick loop check at the sockets where its between......
call it £350

 

[Des 56]

I think you have to get the circuit make up absolutely sure and precise
That is before even thinking about searching for the RCD tripping cause

I know you say you have tried and tested most of what you expect to be the cause,but personally I suspect you are getting bogged down sorting 2 different problems with one mind set

This is not meant to be criticism of your testing or yourself (because that would need to be observed rather than guessing procedures and outcomes on a forum)
It's meant more as a pointer, hopefully,that may make the road clearer for you
It seems to be a pain in the neck problem,but there is a reason and logic and testing and investigating using that logic will reveal all

 

[guest119]

new build? no ring continuity?
look for a socket thats been missed out
should be able to tell from a quick loop check at the sockets where its between......
call it £350

Been there, with a magnet on the wall.
Behind a radiator is also a favourite one to miss on a second fix.
Boydy

 

[Guest569]

new build? no ring continuity?
look for a socket thats been missed out
should be able to tell from a quick loop check at the sockets where its between......
call it £350

Good shout but ends are belling out using bell set , If it were properly wired ring with a socket missed ( potentially lying live somewhere) I would expect it to bell , which suggests there is a big mix up somewhere !

 

[Guest569]

and what model is the metrel tester ?

will check

 

[Guest569]

I think you have to get the circuit make up absolutely sure and precise
That is before even thinking about searching for the RCD tripping cause

I know you say you have tried and tested most of what you expect to be the cause,but personally I suspect you are getting bogged down sorting 2 different problems with one mind set

This is not meant to be criticism of your testing or yourself (because that would need to be observed rather than guessing procedures and outcomes on a forum)
It's meant more as a pointer, hopefully,that may make the road clearer for you
It seems to be a pain in the neck problem,but there is a reason and logic and testing and investigating using that logic will reveal all

Totally, There is 2 problems Im sure. Ill get circuits organised as best I can on Monday.

 

[Plonker 3]

Sorry only browsed over the thread so apologies if this has been asked already, but you say you have narrowed it down to a RFC. Have you removed every socket and proved each leg between the sockets? Then carried a IR on each individual leg?

 

[Guest569]

Sorry only browsed over the thread so apologies if this has been asked already, but you say you have narrowed it down to a RFC. Have you removed every socket and proved each leg between the sockets? Then carried a IR on each individual leg?

Yes and all fine. I wish it was that easy and one leg was down.

IR is fine and it bells out ok but Im convinced something is spurred off the ring then back onto it or onto another circuit somehow, Frankly I think someone has made a complete arse of wiring the ring !

 

[R G]

If your able to pop back before Monday , you could isolate that 1 circuit and see how it goes before Monday , to confirm your suspicions .