Dead RCBO? or Brain fart

[Andy Walker]

This could just be a Friday evening brain fart after a long week but,
Got home tonight to find the downstairs lighting cicuit has tripped, tried to reset the RCBO and it blew again straight away. IR tested the circuit, all fine.
While the circuit was disconnected I tried turning the rcbo on and re-energising the board and RCBO trips again. I took the neutral flying lead out of the neutral bar and RCBO doesn't trip. Like I say, could be my brain isn't functioning correctly and I'm missing something obvious or has the RCBO failed? Any thoughts appreciated.

 

[Pete999]

This could just be a Friday evening brain fart after a long week but,
Got home tonight to find the downstairs lighting cicuit has tripped, tried to reset the RCBO and it blew again straight away. IR tested the circuit, all fine.
While the circuit was disconnected I tried turning the rcbo on and re-energising the board and RCBO trips again. I took the neutral flying lead out of the neutral bar and RCBO doesn't trip. Like I say, could be my brain isn't functioning correctly and I'm missing something obvious or has the RCBO failed? Any thoughts appreciated.

What IR tests did you carry out L-E, N-E, L-N? and what were the results?were all of the circuit under test dissed from the CU?

 

[Deleted member 9648]

Without the circuit connected to the load terminals of the RCBO it would seem that a faulty RCBO is the only explanation.

 

[Marvo]

Same as Wirepuller, if it trips with circuit live and neutral disconnected replace it with a new one.

 

[Andy Walker]

Pete, did all L-E, N-E and L-N all >400MOhm. Circuit I tested was disconnected from the CU.

 

[Toneyz]

I had a faulty MCB the other day where there had been a L-N short in a pull cord and they had tried turning it back on so the KA had got the better of it.

 

[Toneyz]

Pete, did all L-E, N-E and L-N all >400MOhm. Circuit I tested was disconnected from the CU.

Not the earth though?

 

[Andy Walker]

Cpc of the circuit was disconnected too

 

[westward10]

Sounds like the rcbo if it does it without the circuit connected, as already stated. Have you tried connecting it to another rcbo in the board.

 

[Andy Walker]

Yeah, connected the circuit to another RCBO and it's working fine.

 

[westward10]

Duff device, what brand is it.

 

[Andy Walker]

It's a Hager, I always thought they were half decent, only been in the CU about 3 weeks.

 

[Marvo]

Hager are generally pretty good. Should be able to return it under warranty.

 

[westward10]

It should be replaceable under warranty and I think Hager would be interested in its return.

 

[Andy Walker]

Thanks guys, I'll give them a try. Feel slightly better knowing that my brain is still kind of working.

 

[littlespark]

I thought I had a "soft" Hager RCD on a recent job.
I had added downlights in a kitchen, under cabinet lights and kickboard lights and changed the switch to a 3 gang.
Every so often the switch for the cabinet lights tripped the RCD. Not every time, and it had all tested ok. I thought initially it was either the transformers I put in, the LED lamps or a knackered RCD
It gradually became every time I used the switch... on or off. IR now showed a short between neutral and earth. Worked my way from the board disconnecting neutrals and testing until I found the cable with the problem;- switch wire to outside light at the front door. Luckily easy to replace.
How come a neutral to earth fault only affects the RCD when I turn on a switch at the other end of the house?

 

[Marvo]

Maybe the switch was slow to operate and the arcing caused some earth leakage via the surge arrestors in the driver or transformer.