MCB keeps tripping (and sometimes RCD trips too) - nothing plugged in

[JohnD]

I'm visualising a 50-year old installation. It used to have fusewire and has a strange socketr circuit.

I'm thinking of rubber cables and junction boxes under the floor.

It would be interesting to see some photos. Of the old cables, connections and sockets. Light switches and ceiling roses.

 

[chivers67]

The Sockets are on a 20A which is what I'd expect if a Radial

 

[NigelGS]

I have just been looking at You Tube for clues.... should I ask them to test for "fault to earth" and/or measure any "leakage current"?

 

[JohnD]

it would also be interesting to see the cables around the meter and CU

 

[NigelGS]

what's a CU?

 

[JohnD]

Consumer Unit. What you call a "fusebox"

 

[bernardgreen]

what's a CU?

Consumer Unit ( modern name for a fuse box )

 

[NigelGS]

there are no wires to be seen around the CU. Just the box attached to the wall. And not much to see around the meter ...

 

[securespark]

I suspect a qualified spark would have at least split the lighting MCBs across the two RCDs....

 

[333rocky333]

Not that it helps your problem, a board fitted days ago should have a Label wth test Rcds 6 monthly not quarterly.

 

[securespark]

Hi NGS

Did you talk to them?

 

[AndyPRK]

Comic board.

4 rcbos would be sensible.

 

[AndyPRK]

So if it were me I would open the CU. and see if there are 1 or 2 wires leaving the socket MCB.

If there is 1 wire, then pick roughtly the middle point between the CU and the last socket. (but of a guess!), open the socket, and remove 1 set of wires LNE) and isolate them in terminal blocks. Leave the other cable in the socket.
This should result in some sockets working and others not.
Monitor this for a few days and see if the RCD/MCB trips. You will at least have some working sockets. and may narrow down the fault zone.




If the CU has 2 wires leaving the MCB, then order a MK MCB B16 or B20

 

[NigelGS]

Thanks for your continued interest. I have been too busy these last few days to provide a further update. What also delayed me was that I realised that in middle of last week I did drill holes in wall so I wasted money on a gizmo that is supposed to identify if there are live wires within the walls ... but this didn't give me consistent readings. After taking out the raw plugs and looking inside the drill holes I could not see any indication of wires being hit so I then started to hack away the plaster to check. I gave up on this at the point when I hit solid brick.

I then chased the original electrician again pointing out that I had done all I could to diagnose what might be the problem and that they needed to re-attend. He said he can do that but that the fault sounded hard to find and that he would probably recommend re-wiring. With my "new knowledge" I then asked him what tests had been done initially ... IR test, Earth leakage, etc etc. He said "all of those". But as his response was "re-wiring" rather than "don't worry, we will sort it out for you" I was so frustrated I searched Google and found a local electrician who showed confidence over the phone that they could help me.

The result is ... during a 1 hour visit .. (£90 incl VAT) he immediately identified that it was 2 radials and not 1 ring circuit. He put in another MCB on the CU for each radial and was mystified why the original electrician had not done that initially.

He then identified that the radial upstairs was all working but that it was in basement where the problem was. He went round to each socket, taking them off the wall, testing with meter and also expecting to find the end of the radial at some point. It got to the point where all the sockets were working but there were still wires running somewhere else that obviously had a problem on them but were not needed as there were no more sockets in the basement that were needed on this radial. He disconnected the wires that ran off into the 'unknown'. And all now is good!

If you remember from my first post I mention a dead socket in the lounge that did not seem to be joined to the rest of the lounge circuit. My theory is that some idiot (over 20 years ago ... because I bought this place in 2000) wanted an extra socket in the lounge and for some reason went down through the ceiling to link with the basement radial. The wiring from this socket in the lounge does disappear through the floor boards approximately above where the 'last' socket is in the basement.

Maybe it was originally a ring circuit and after a problem it got split into 2 radials. is that possible?

Anyway ... I am happy now ... (which you can tell from the length of this message) ... I can get my life back again and will probably give the original electrician a hard time to see if I can get any compensation from them.

Thanks for all of your input.

 

[EFLImpudence]

Very good. Some know what they are doing.

Yes a ring might have been split into two radials - thus removing a length of cable from the circuit.