tripping rcd

[tommy-trucker]

Hi All
been asked to check out my friends flat his rcd is tripping all the time even when he's not there all seems fine apart from the insulation resistance on the lighting circuit is slightly low but unable to currently get to the connections as they are spots and cannot get to the junction boxes but when i was changing the shower switch back box the whole system tripped this circuit was connected at the time but not on(added that bit on just in case someone thought i was working on a live one)but the rest of the system was on so i could have lights on in the bathroom this is the first time i've come across something like this so any help would be grateful if i don't get back to you tonight with any questions you have i'm of to work, but i will answer you
cheers Tom

 

[ezzzekiel]

A high ZS on whichever circuit that is the problem would have the opposite effect on an RCD ie would not trip

rcds were originally intended to overcome high zs values - for example tt systems where disconnection times could not be met, and allow a zmax of 1667 ohms

 

[beanzntoast]

rcds were originally intended to overcome high zs values - for example tt systems where disconnection times could not be met, and allow a zmax of 1667 ohms

I know that my friend but what I meant was that if the ZS was too high i.e higher than 1667 then it wouldn't trip in the time allowed.like the post above mine described it better the point i was making but probably didnt explain it correctly & as previous posts says because his RCD is tripping then it must be something else not his ZE ,cheers jason

 

[ezzzekiel]

1667 is a pretty high zs value

 

[tommy-trucker]

Thanks for all your messages have to go back and recheck the sockets as it does only seem to be when the sockets that are tripping it
once again cheers all and any more problems will let you know
Tom