RCD tripping instantly despite nothing plugged in

[mojo8472]

Having a weird one: Yesterday the RCD tripped a couple of times over a few hours (hasn't happened before).

This morning I find it's tripped again and triggers instantly when I energise a single ring MCB - even when I've disconnected everything from the sockets. I've also popped the faceplates off the sockets to check the wiring, all seems fine apart from some Cu corrosion on the wires leading to a socket on a damp wall.

Is this corrosion likely to be responsible for the trips? Or is it more likely that something's happened to the wire in the walls?

 

[DaveHerns]

Has something happened to the circuit? Has it rained to make the wall extra damp ? I'd be cleaning off the corrosion and seeing if it works OK. If so , you need to rectify the damp problem

 

[Taylortwocities]

That damp may be the culprit. Remove the socket completely and termiante the cable ends and try again. The damp may have permeated into the socket guts.
If thats not then problem then…..

I've disconnected everything from the sockets.

What else in on that circuit? As well as sockets there may be a feed to outside, power for boiler/central heating, etc. This are the usual suspects when RCDs trip.

 

[mojo8472]

Has something happened to the circuit? Has it rained to make the wall extra damp ? I'd be cleaning off the corrosion and seeing if it works OK. If so , you need to rectify the damp problem

Nothing changed on the circuit at all, nor have I hammered in any nails around the sockets! Just tested after disconnecting the faceplate entirely with the same results.

The feed doesn't run outside, although it is connected to the boiler. I've pulled the fuse on the isolator switch for the boiler and it still trips

 

[plugwash]

It may be time to split the ring into sections and insulation test each one.

 

[JohnW2]

It may be time to split the ring into sections and insulation test each one.

Indeed - or, if the OP doesn't have the means of IR testing (and assuming he is comfortable/competent to do things in the CU), disconnect one end of the ring at the CU and then to work around the ring, breaking it at each socket, until he finds where he has to break it to stop the tripping - then reconnect the disconnected end of the ring and do the same from the other end.

Kind Regards, John

 

[securespark]

Christ, don't tell Ban....

 

[ban-all-sheds]

Indeed - or, if the OP doesn't have the means of IR testing

get a man who does.

 

[JohnW2]

Christ, don't tell Ban....

However, apart (possibly) from the need to disconnect things in the CU, it's not really much different from the suggestion to "split the ring into sections and IR each one".

Kind Regards, John

 

[JohnW2]

Indeed - or, if the OP doesn't have the means of IR testing

get a man who does.

That's obviously one approach - but what I suggested ought to be as effective at locating, or at least 'narrowing down', the source of the problem.

Kind Regards, John

 

[DaveHerns]

Maybe he needs to disconnect the boiler feed as if it has a N-E fault , pulling the fuse won't make any difference ( I think)

 

[securespark]

Disconnecting the neutrals of the suspected circuit and isolating the corresponding MCB will narrow it down.

 

[JohnW2]

Maybe he needs to disconnect the boiler feed as if it has a N-E fault , pulling the fuse won't make any difference ( I think)

Yes, but if it were a N-E fault, it's very unlikely that the problem would go away when the just the MCB for the circuit was switched off (given that that there are no other known loads on the circuit).

Kind Regards, John

 

[JohnW2]

Disconnecting the neutrals of the suspected circuit and isolating the corresponding MCB will narrow it down.

The RCD trips apparently stop when just the MCB is switched off, even with the neutral still connected.

Kind Regards, John

 

[securespark]

What about a fault on another circuit that is manifesting itself when an unrelated circuit is energised?