UK Rcbo intermittently tripping

[Siraj123]

Done a board change at domestic property ti an rcbo and spd board, previously had old rewireable fuse board, and done all my ir tests and so on and everything seemed good, lo and behold I get a phone call that the downstairs sockets have tripped, I told them to remove all loads and the circuit still tripped overnight.
I then went back to job and found a loose neutral in one of the sockets which I then connected and everything was back up and running, keep in mind that security system is on this circuit via a unswitched spur.
I then decided to redo an ir test only to find that there was a complete dead short between all conductors even after removing all loads and fuse from the spur and also removing the wires from the rcbo and earth bar.
Any help would be greatly appreciated.

 

[KungFuTurkeyLeg]

Look for something different on the walls. Guessing a new picture has been hung or something of the nature that puts holes into walls or floors. Or a leak has caused something to get very wet. Take some resistance measurements to calculate rough distance to the fault

 

[Bluetit]

Had something vaguely similar recently. Turned out to be a badly wired extension with t&e run in god knows what (my guess is nothing) under the floors. After the recent deluge of rain a leg had gone down taking out the ring. As above moisture ingress or some wall hangings seem a likely culprit.

 

[simpson93]

The IR test is between live conductors and earth? neutral to the security still seems to be connected if you've only removed the fuse.

I would break the circuit up and test in between sockets to find the issue.

 

[Siraj123]

The IR test is between live conductors and earth? neutral to the security still seems to be connected if you've only removed the fuse.

I would break the circuit up and test in between sockets to find the issue.

Literally came into my mind last night that only the lines isolated and not the neutral.
Will do exactly that when I'm back down there, much appreciated

 

[Siraj123]

Had something vaguely similar recently. Turned out to be a badly wired extension with t&e run in god knows what (my guess is nothing) under the floors. After the recent deluge of rain a leg had gone down taking out the ring. As above moisture ingress or some wall hangings seem a likely culprit.

First thing I checked was any new wall hangings but nothing looked suspect, but highly likely that moisture could be an issue.
Appreciate the help

 

[Siraj123]

Look for something different on the walls. Guessing a new picture has been hung or something of the nature that puts holes into walls or floors. Or a leak has caused something to get very wet. Take some resistance measurements to calculate rough distance to the fault

Yup will do exactly that when I'm back down there.
Thanks for the help