Maddening MCB Tripping fault

[vwes59]

Hate these. Been called out to troubleshoot a tripping MCB. It's a house I've been to before and I know the wiring is a real dogs diner, but anyway.

Got an MCB that's tripping out with no appliances plugged in. The sockets themselves are not in a great state, however continuity and insulation resistance tests across the circuit showed no problems (Did that at every socket on the radial). Turned on the breaker and within 5 minutes or so it tripped out. Not seeing any singeing on the conductors or sockets.

Now I have to say, last year I attended this house and replaced a burnt out MCB (Different circuit) - surely this couldn't be a second one. The board is only maybe 10 or so years old (Hager).

In my experience these rarely turn out to be cable faults as it would show up in the insulation resistance test, so I'm left with one or more dodgy sockets (6 total on this radial), loose wiring or a broken MCB.

Any other thoughts ?

 

[Lucien Nunes]

could of being a neutral to earth fault causing the trip

No, this could not have been the problem as it was an MCB tripping, not an RCD.

 

[Intoelectrics]

great find on the boiler earth could of being a neutral to earth fault causing the trip when the boiler fired up

As Lucien says^^^^ As the electrician you should already have a clear understanding of protection device's functionalities and what type of fault you are expecting to be looking for. Hence the suggestions previously mentioned regarding checking the current flowing through the device.

 

[Intoelectrics]

As Lucien says^^^^ As the electrician you should already have a clear understanding of protection device's functionalities and what type of fault you are expecting to be looking for. Hence the suggestions previously mentioned regarding checking the current flowing through the device.

I forgot to clarify, for an mcb you would be looking for the total load current to see if or when it is exceeding the rating of the device. For an RCD you would be looking for the total current imbalance to see if or when that is exceeding the rating of the device. For a combined rcd and mcb (rcbo/rccb) you would be looking at both.

 

[cliffed]

There’s nothing worst trying to find faults when there are non accessible junction boxes.
The Client’s not interested in your efforts & all the blame comes to you…I hate it

 

[Midwest]

It wasn’t the OP reopening the thread.