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

[NigelGS]

I have already searched this forum looking for help. I found lots of related threads here =

https://www.diynot.com/diy/search/75855794/?q=nothing+plugged+in&o=relevance&c[node]=8

But I am still stuck and need help.

A bit of background: I own a flat (ground floor and basement). I lived here previously years ago and had no problems with the electrics. Then I rented it out for 5 or 6 years. I moved back in last week. The 15 amp fuse (old fashioned. Fuse wire) blew 4 times on the first day. Then blew a couple of times during next few days. I paid to have a modern fuse box installed a couple of days ago. Ever since then the MCB keeps tripping and on occasions the RCD tripped too. The electricians who installed it came back yesterday. And waited around expecting the MCB to trip again. Which of course (sod's law) it didn't. They seemed unable to think of what other tests they could do. It was left that I would try and diagnose the problem myself (ie try to identify what socket or device was causing the problem) over the weekend. The whole flat is on just one 15 amp ring circuit. After many hours of only using electricity in certain areas it dawned on me that the MCB trips even if nothing is plugged in.

I contacted the previous tenants who said they never had any problems with the electrics.

Reading through all posts that seemed to have similar problems I can already say ... I have not been drilling into walls or hitting nails into walls to hang pictures. Also there are no power sockets outside.

Does anyone have any bright ideas that could help me?

At the moment I am coping by running a couple of extension cables from the cooker plug.

One other (curious) thing that might not be related. In the lounge there was a double socket that was dead. The electrician pulled up some floorboards but could not trace the route fully but said it seemed to be on its own isolated ring/circuit. Apart from the cooker circuit the rest of the flat (ground floor and basement) is all on the one circuit. So it seems strange to me that there should be just be a random socket on its own circuit. He took the socket off, 'capped' off the wires and screwed a plate over it.


Any bright ideas anyone?

 

[NigelGS]

...also .... I only joined today ... and I have no idea whether I have even posted my question in the right area?

time will tell

 

[securespark]

Can you scan and post a redacted copy of the test certificate so we can see what his test readings were?

 

[securespark]

It will probably be moved to Electrics UK.

 

[bernardgreen]

Are you in the same place ( room ) each time the MCB trips ? If yes then suspect a cable trapped between floor board and joist being quashed and shorted when you walk on it.

 

[Ihavenojob]

Damp walls in the basement?

 

[EFLImpudence]

If an MCB trips then it will be a Live to Neutral short circuit or Live to Earth fault.

As it is intermittent, this could be in an appliance or in a cable being moved somehow, as said, under floor boards being stood on.

If you can't recreate the fault at will, then it will be difficult to find.

You can only note what you were doing and using when it trips.

 

[NigelGS]

sorry ... didn't notice I had any replies.... I was busy searching You Tube trying to find a solution.

I haven't received the test certificate yet. As he left the house he asked if I was in a rush to receive the test certificate and I said "no" .. as I did not know then that I would have future problems.

It trips when no one is walking around.

I run humidifiers in the basement to remove moisture from the air .. but generally the rooms are not damp .. I have 2 bedrooms and hallway in basement. central heating down there too.

 

[donrkebab]

I run humidifiers in the basement to remove moisture from the air.

They would be my prime suspect, try unplugging them, and see what happens

 

[NigelGS]

yes I thought that too ... but no appliances made the MCB trip immediately... and all day today I have NOTHING plugged in to any sockets.

Every 30 mins or so I check the fuse box and it has tripped again.

 

[chivers67]

Sorry did you say the Whole Flat is on one Ring that's 15 Amps? Is that before or after the new Consumer unit or both? I'd hope these Electricians did some kind of insulation resistance test before they replaced the Board which one would hope would highlight any issues with the existing wiring.

 

[NigelGS]

Yes ... the whole flat is on one (what I call) 15 amp circuit, but is apparently 16 amp these days.

The old fuse box had 2 fuses for the power and 2 for lights. The new fuse box has 2 for lights, 1 for cooker and 1 for the rest of the power. I have no idea if the previous 2 for power was one for 15 amp and the other for the cooker. I presume it is impossible to be otherwise?

I don't know if an insulation resistance test was done at start. I can ask them that on Monday

 

[chivers67]

Seems odd to say the least if you've a ring circuit on a 15A Fuse (unless it is actually a Radial) and even odder that it's been replaced with a 16A MCB if it is a ring, if it were a radial then I'd expect it to have been replaced with a 20A MCB/RCBO. How many sockets have you actually got in total ?

 

[NigelGS]

In basement there are 2 bedrooms and a hallway. 2 double sockets in one bedroom plus a switched spur to a fan in the window. But the fan has been disconnected. 1 double socket in the other bedroom and 1 double socket in the hall. On ground floor lounge with 3 double sockets (1 of which is dead and seemed to be on its own circuit). Ground floor bedroom has 2 double sockets. Kitchen has 3 double sockets plus a fused spur for the washing machine. Plus another cooker socket.

Now that you mention it ...20 amp was mentioned in conversation (but so was 16) so it might be 20 amp..

There are 2 RCDS. 1 for the cooker MCB and the 2 light's MCB and the other RCD for the MCB causing me problems.

 

[NigelGS]

not sure how to use this forum ... I am trying to include a pic of the new fuse box ..