No load fuse trip but not RCD.

[datanotpwr]

I awoke to find half of the circuits had tripped on the RCD the other day. So I when I reset the RCD and then turned off each fused circuit and turned them back on in sequence to find which one was tripping the RCD.
Turns out it was the first floor sockets ring circuit which has a B32 MCB which is relatively new, the whole CU is and the RCDs (about 18 months old).
So then I unplugged everything from the 1st floor and turned of the fused plugs that isolate the electrical underfloor heating in the bathroom and the towel rail, then tried again. Still tripped the RCD.

So then I thought it might be either the towel rail or the underfloor heating from water ingress or something, so I took the cartridge fuses out of those and tried again, still tripped.

I though there may be water ingress on the back of one socket as it is in a bedroom but the shower is behind it, took the front off an dry as a bone.

Still unable to have the 1st floor socket MCB on without tripping the RCD immediately.

So then I think I should take off all the faceplates (started with the ones that have the USB charging built in) one by one and just use some reusable Wago connectors and effectively remove a socket from the circuit. Still cant get it to not trip.

So now I have removed all the sockets and used the Wago connectors to basically cover each L & N wire behind each socket, so none of them are actually connected to anything else at all. Like in the pic here.

Now what happens is that the RCD does not trip, and the MCB stays on, but then after a little while when I was walking back upstairs I heard a click, went to check and the MCB has tripped but not the RCD.
I was going to try this again, but thought not a good idea as thought it would mean that the load has to be going over 32A somewhere for the MCB to trip on it's own. I thought best I didn't test this bit again without a professional.
I am at a bit of a loss now.

The 1st floor ring circuit is older than the CU and all the wiring is the old type except for the towel rail and underfloor heating.

Are there tests that can be run in between sockets and the CU to see where the issue is if it is not visible by removing them all and isolating?
I don't really want to start taking up floors or something like that.

 

[pc1966]

Really you need to actually measure/test things with a meter capable of doing insualtion test (typically 500V for dometsic electrics, not the 1V or so a multimeter uses) and it will be cheaper and quicker to get in a professional electrician to do that.

It might be a cable fault, it might be some equipment that is attached but you are not ware of it. You can waste a lot of time and energy if you don't have a systematic approach and the equipment to verify sections of cable, etc, as they are isolated and tested.

 

[7029 dave]

The circuits/ circuit needs to be tested, IR test is needed best to get an Electrician, you have done about as much as you can.

 

[datanotpwr]

Really you need to actually measure/test things with a meter capable of doing insualtion test (typically 500V for dometsic electrics, not the 1V or so a multimeter uses) and it will be cheaper and quicker to get in a professional electrician to do that.

It might be a cable fault, it might be some equipment that is attached but you are not ware of it. You can waste a lot of time and energy if you don't have a systematic approach and the equipment to verify sections of cable, etc, as they are isolated and tested.

Thanks, so would a typical test be carried out before disconnecting them all and so should I reconnect all the sockets

The circuits/ circuit needs to be tested, IR test is needed best to get an Electrician, you have done about as much as you can.

Thanks both, I was reading up about on test equipment but it is very pricey and I wouldn't know what to do with it anyway.
Do you think I am best leaving all the sockets off and the WAGO connectors on, or should I put everything back how it was?
The MCB is just switched off.

 

[TJ Anderson]

M

Thanks, so would a typical test be carried out before disconnecting them all and so should I reconnect all the sockets

Thanks both, I was reading urp about on test equipment but it is very pricey and I wouldn't know what to do with it anyway.
Do you think I am best leaving all the sockets off and the WAGO connectors on, or should I put everything back how it was?
The MCB is just switched off.

If you have all the conductors in Wago's as in pic then you only now have 1st and last leg on ring final still connected to MCB. As circuit is now so deconstructed it now needs to be reinstated and tested by an electrician as if initial verification, the fault will soon be traced by someone competent with test equipment. Randomly pulling the circuit apart and then reseting RCD's and MCB's onto faults is not the way to go and is likely going to end up giving you more problems than the single fault you started with.

 

[James]

I would leave it as is,
If I were coming to fault find, I may well end up deconstructing the ring like that anyway.

 

[datanotpwr]

Thanks. It was not random, I did them one by one to try to rule each one out, first by just removing a socket and using the wago terminals but with both sets of N & L wires in the same terminal so the ring was still complete but with each socket removed in turn.
When that didn't work.Then got to the place where in theory I thought if I disconnect everything it has to be a fault on a cable somewhere which was obviously not what I was hoping for as then it means potentially replacing cable I guess. Or there is a hidden junction or joint somewhere that I dont know about that has a fault.
I think it might be from when we had renovations done and had complete new wiring on the ground floor but not the first floor. The builder (not a sparky) kept temporarily disconnecting the ring main on the first floor to complete works. Then when the sparky came to put in a new CU and he hooked up the 1st floor ring to it (that he did not install) potentially some of the builders temporary work still existed and is now behind a new ceiling.

Would all qualified electricians be expected to have all the test equipment necessary to find this fault?

 

[markythesparky]

This is what happens when someone who is not qualified to do the work does the work!

Yes, any electrician who is a real and proper electrician (Not someone who says they are) should have and be able to use the relevant testing equipment. If he/ she does not have it then it is not worth them looking at the problem.

 

[datanotpwr]

Thanks all, I'll book in pro to come in and sort it out.

 

[DPG]

Thanks all, I'll book in pro to come in and sort it out.

Let us know what they find.