2 rcbo tripping. 2 rcbo tripping

[casperLennon]

Hi. Today I turned a rcbo on and it tripped straight away and took another one with it.
Any help is appreciated.
I didn’t have time to look at anything so just wondering what are peoples initial thoughts

 

[Dave OCD]

My first thoughts are mixed up neutrals on the RCBO outgoing terminals or somewhere in the wiring the two circuits have linked neutrals.

 

[casperLennon]

That’s why I thought. I had a very quick look and they seem fine. The rcbo I switched on banged so I assume the fault is a short somewhere in that circuit but the other one threw me

 

[littlespark]

Maybe just vibration from the first one going that took out the second.
Does the second one reset? Is it adjacent to the first?

 

[casperLennon]

The 2nd does reset.
The 1st is 3L3 and the 2nd one is 4L2.

 

[pc1966]

It is not unknown for "instant" RCD to trip on surges so switching on to a fault could do it, big dV/dt on the supply from the high fault current and so high peak leakage from C * dV/dt

Other common thing is stray fingers accidentally hitting an adjacent test button, more so if you jump with an on-fault BANG! when closing something!