RCD keeps tripping

[AVI_8]

RCD keeps tripping in the house, I’ve narrowed it down to one circuit breaker for the downstairs sockets, the other socket circuit breaker is not causing the RCD to trip so at least we’ve got power.
I don’t understand why one would cause this issue and not the other. Every socket has power with using one side of the ring main so I don’t think there’s a break in the circuit.

I’ve switched off every socket (didn’t unplug things) and the fault is still there.

Any ideas as to where to start troubleshooting or is a case of taking the faceplate off every socket to inspect the wiring? Or is there a device I could buy to test each socket and the wiring?

The house was fully re-wired in 2015 by an electrician.

 

[123hotchef]

check the wires are tight in the CU first port of call for me.

 

[sparkysy]

Unless you unplug things the fault may still be present as we tend to only switch the live in the UK, unless the socket has double pole isolation! It may be something plugged in that has a fault. Unplug everything and try resetting the mcb and see if the rcd trips. If it does try turning off any spurs that are on that circuit and go again. If it still won't stay on then there is either a fixed wiring fault somewhere or something you have forgotten to switch off or unplug.
If it still trips you need a tester and some fault finding done!
Sy

 

[Dee J]

If every socket works with one mcb off then it's not a socket mcb. Both ends of the ring go into one mcb, not one for 'each end' (unless there's a horrible mistake in your wiring).

 

[AVI_8]

Actually there’s no power to 2 of the bedrooms with one CB switched off, my mistake.

 

[sparkysy]

Do you just have one RCD?
It could be a neutral earth fault that is taking out the RCD or if you have a lot of electronic equipment plugged in it may be accumulated leakage from it all combined pushing the RCD over the trip threshold. A 30ma Hager RCD will typically trip between 21 and 27ma of current flowing to earth!
Sy

 

[Dee J]

Definitely unplug everything on that circuit. As said before, many sockets only switch off the live side. And check for hidden loads.. SW-fuse for bathroom heater or towel rail? An outdoor socket? Something in the loft. After that you need test gear and knowledge to go further. Really an 8 year old rewire shouldn't be displaying faults.

 

[AVI_8]

Do you just have one RCD?
It could be a neutral earth fault that is taking out the RCD or if you have a lot of electronic equipment plugged in it may be accumulated leakage from it all combined pushing the RCD over the trip threshold. A 30ma Hager RCD will typically trip between 21 and 27ma of current flowing to earth!
Sy

No there’s another RCD for the kitchen and upstairs sockets
Unplugged everything and the fault is still there.

 

[AVI_8]

Definitely unplug everything on that circuit. As said before, many sockets only switch off the live side. And check for hidden loads.. SW-fuse for bathroom heater or towel rail? An outdoor socket? Something in the loft. After that you need test gear and knowledge to go further. Really an 8 year old rewire shouldn't be displaying faults.

No bathroom electric power other than the lights, no outdoor sockets, the upstairs sockets are in the loft as we haven’t done the conversion yet, that’s all off another RCD which is OK, could a faulty circuit breaker cause this?

Edited to say I was under the floor in the house on Thursday to pull a cable through to the living room for the fibre broadband installer, its a tight entrance to get down there and it’s where all of the cables come up to the CU, I’m thinking now that I might have disturbed something.

 

[dobbslc]

If it only trips when you switch that mcb on then chances are it's a live to earth fault, switch off all spurs and sockets, check for spurs that might feed a TV booster in the loft or a shower pump etc.
Just looked again at your picture, the two MCB's are or should be feeding two completely different circuits, they've not been well marked up with both saying "sockets" .
If you took the cover off you'd see two cables in each mcb, one pair (ring) for each circuit.

 

[sparkysy]

Ok that is helpful, are you positive there is nothing else plugged in. I only ask as I've had it many times where something that is hidden and forgotten and still plugged in has been the culprit!
Also has any DIY, new pictures been put up since this started?
How competent are you with electrics? If you feel you are capable I would start by checking at each socket on the affected circuits and see if that is where the fault is power off of course!
Very unlikely that an MCB would cause the RCD to trip. It's going to be a fault on either equipment or the fixed wiring, or possibly a fault with the RCD! Does it trip using the test button on it?

 

[dobbslc]

Do you have rodents in the house?
They can cause utter chaos!

 

[AVI_8]

Do you have rodents in the house?
They can cause utter chaos!
View attachment 386689

I did have last month, caught a couple in traps

 

[AVI_8]

Ok that is helpful, are you positive there is nothing else plugged in. I only ask as I've had it many times where something that is hidden and forgotten and still plugged in has been the culprit!
Also has any DIY, new pictures been put up since this started?
How competent are you with electrics? If you feel you are capable I would start by checking at each socket on the affected circuits and see if that is where the fault is power off of course!
Very unlikely that an MCB would cause the RCD to trip. It's going to be a fault on either equipment or the fixed wiring, or possibly a fault with the RCD! Does it trip using the test button on it?

I’ll do that tomorrow when it’s light, I edited a post earlier to mention I might have accidentally disturbed the wiring going to the CU when I was under the floor on Thursday the entrance is under the CU and it’s quite tight to get under.

 

[sparkysy]

Mmm the list of possibilities is growing!
Rats and squirrels can be an absolute nightmare with wiring as @dobbslc says!
Or you may have accidentally pulled something under the floor and caused the fault. It could also be totally unrelated to something you have done!
Keep us informed and we will try and help further!
Sy

 

[AVI_8]

Ok that is helpful, are you positive there is nothing else plugged in. I only ask as I've had it many times where something that is hidden and forgotten and still plugged in has been the culprit!
Also has any DIY, new pictures been put up since this started?
How competent are you with electrics? If you feel you are capable I would start by checking at each socket on the affected circuits and see if that is where the fault is power off of course!
Very unlikely that an MCB would cause the RCD to trip. It's going to be a fault on either equipment or the fixed wiring, or possibly a fault with the RCD! Does it trip using the test button on it?

Definitely nothing plugged in and yes it trips with the test button, I’ll pull the cover off the CU tomorrow first of all to see if I’ve partly pulled a wire out by accident, I’ve never had a problem with the electrics before and now it seems a coincidence that this started the day after I crawled under the floor.
Thanks for all of your help guys.

 

[brightspark]

is it tripping instantly the breaker is turned on or taking a while

 

[AVI_8]

Less than a second

 

[brightspark]

Less than a second

what you can do is disconect a socket thats on the ring main furthest away from db and disconect one leg live and neutral of the ring at the db and turn it back on. if it still trips disconect it and put the other leg back in and it should stay on. half of your sockets should be on see how that goes before disconecting more just make sure all appliances are unplugged 1st and all switchspurs are turned off its preferable to have an insulation tester to check as well

 

[Dee J]

The friction of pulling another wire through a tight space can rub through and melt insulation on existing wires. If you've worked near wiring recently then that's likely to be where the fault is.