RCD Tripping – Fault Traced to One Socket, Still Trips with Replacement

[opps]

I'm having an issue with an RCD that keeps tripping as soon as I attempt to turn it back on. I've already unplugged all appliances from the affected circuit, but the RCD still trips immediately. To isolate the fault, I disconnected each socket on the circuit one by one and managed to trace the problem to a single socket.

When this socket is disconnected, the RCD resets without any issue. However, when I install a brand new socket in its place and wire it up, the RCD trips again as soon as I attempt to turn it on.

This suggests the issue might not be the socket itself but potentially a fault in the cable feeding it. There are no obvious signs of damage, but I haven’t carried out any insulation resistance testing yet.

Looking for advice or confirmation from anyone who's seen a similar issue — is it likely to be a neutral-to-earth fault or some other wiring issue in the cable?

I am not an electrician.

In the event that you remove the socket and fit a terminal block, does the fault still exist? I would be inclined to be think that @crystal ball might be correct about a spur that runs off to the outside. I am also mindful of @EFLImpudence point about RCDs and MCBs

Photos will help.

 

[Scally-Ho]

Of course, it could be possible that the fault lies within the CU. I've seen all kinds of debris in the back of many over the years.

 

[crystal ball]

Just to add to the fun, I have found the following causing trips RCD & MCB & fuses,
Slug in JB & TV amp
Suspected melted cable run behind fire place
Water in inaccessible JB, water stain on ceiling below
Water in outdoor kit
Nicked cable in back box
Rodent damage
T&E run outside through a tree, branch had rubbed through

 

[Harry Bloomfield]

I have isolated the MCB as it was causing the RCD to trip.

That suggests it has to be a L to E fault, if the MCB prevents the RCD trip.

 

[icon_boy]

that circuit, doesn't have any outdoor sockets, I'm dubious about any water ingress, as we are in a heatwave....

 

[icon_boy]

That suggests it has to be a L to E fault, if the MCB prevents the RCD trip.

The MCB is causing the RCD to trip not preventing it, I will have a look at the wiring coming out of the back box, incase its chaffed....

 

[endecotp]

The MCB is causing the RCD to trip not preventing it, I will have a look at the wiring coming out of the back box, incase its chaffed....

He means, turning off the MCB is stopping the RCD from tripping. That’s right, isn’t it?

 

[Harry Bloomfield]

The MCB is causing the RCD to trip not preventing it,

You misunderstood....

Turning the MCB off, isolates the L only, if the RCD then does not trip, that indicates your issue of the RCD tripping, is due to a L to E fault..

 

[crystal ball]

that circuit, doesn't have any outdoor sockets, I'm dubious about any water ingress, as we are in a heatwave....

Internal leak maybe, pipework joint failed, I recently re plumbed my central heating, found a dry joint that had held for 40 odd years, could have been a different story