Confused - lighting circuit.

[Liam Regan]

Hello, any help will be appreciated. One of the RCDs tripped that protected the downstairs lights, kitchen and upstairs sockets. Process of elimination showed the issue to be with the downstairs lights. At the time it tripped the two kitchen lights had been on for sometime. Separate switches for them. I switched the hall light on and about 5 minutes later the circuit tripped.

I assumed it would be the hall light that was the issue. One switch two lights. I disconnected both ceiling roses. Went to switch the circuit back on and it tripped again.

I have had problems with the hall lights about two months ago that I thought I resolved. Why suddenly go now?

One by one I disconnected every ceiling light. The circuit still trips.

Am I missing an elephant in the room or is it time to call an expert.
Most of the ceiling roses have connectors as per image. Not like the ones i see in guide videos.

 

[Geoff1946]

Unfortunately random time RCD trips can be hard to diagnose. The fault doesn't even have to be on the same circuit, because adjacent circuits on the same RCD can interact depending on overall circuit loading.
Hence looking at the last item to be switched is no indication at all if it was several minutes ago.
It could be a faulty appliance on the ring circuit.
You probably need help.

 

[Liam Regan]

Unfortunately random time RCD trips can be hard to diagnose. The fault doesn't even have to be on the same circuit, because adjacent circuits on the same RCD can interact depending on overall circuit loading.
Hence looking at the last item to be switched is no indication at all if it was several minutes ago.
It could be a faulty appliance on the ring circuit.
You probably need help.

Thanks for your quick reply. Of note when i switched the lighting circuit back on, which immediately tripped, there was nothing else on in the house other than usual stand by stuff. Could it still be surrounding circuits.

 

[Geoff1946]

You did say it tripped a few minutes after switch on. If it goes immediately then it's more likely where the fault lies, but still not 100%.
I'll try to explain; When you switch on a load the current drawn slightly raises the potential on the neutral, due to the resistance of the cable. That small potential is applied to all the neutrals which share that RCD. Note that neutrals are not switched by normal MCBs.
Now if one of those dormant circuits has a short, or partial short, to earth, some current will flow and that may be enough to cause the RCD to trip.
An electrician has equipment which can measure for any such short circuit and will quite likely disconnect individual circuits at your consumer unit in order to test them.