Bizzare RCD

[Albert]

Hi!
Working on adding a double socket to an existing Ring circuit (32A MCB), I isolated the circuit and every time the MCB was off, the RCD tripped. the thing is that it does not happen immediately but after 5, 10 even 30 minuets. I checked the circuit and the R1+R2 values as well as the insulation test are in the range allowed. when the MCB is on it does not happen. this is not the only ring circuit in this installation. any ideas?
Many thanks, Albert

 

[another_sparky]

are you accidently earthing out the neutral?

say, for example touching the neutral cable agaisnt the earth while you're working?
or even with a screwdriver accidently touching the neutral whilst against the metal back box, or ......

I always tape off the neutral and earth whilst doing this type of work

 

[Albert]

Thanks for your reply,
It is hard to say whether i touched the earth and the neutral, they are taped and it seems to happen constantly, is it possible that a unit kicks in, fridge or the immerssion (which I think that the latter, should not be connected to the RCD), and the problem is not caused by the circuit I was working on? Is there a way to verify whether or which circuit could be responsible for this .
Albert

 

[another_sparky]

I thought the RCD has only been tripping since you started working on the circuits?

If it was tripping before you interrupted the circuit, then there are loads of reasons why it could be tripping. Even down to a faulty RCD...(Yes they can go wrong)

 

[Albert]

This is the reply i was worried of. I will have to check each circuit separately.

Many thanks , Albert