Arcing sound from consumer unit for all circuits

[BCW126]

I have been trying to identify the cause of some nuisance MCB trips the last couple of days.

A high power load on one circuit would trip the MCB for that plus take out the MCB for the fridge and freezer at the same time, but I couldn't get any consistent behaviour. Even when the circuit with the high power load on was off sometimes the fridge circuit would trip, with other circuits then effected

Anyway... Whilst glaring at the consumer unit I suddenly heard a crackling arcing noise which coincided with the fridge compressor starting. Not a great thing to hear I presume, but at least that points to the fridge as the culprit right! Or that is what I thought.

It turns out that the same arcing/crackling noise happens when any of the circuits has any noticeable load through it.

With just the fridge/freezer circuit on it does it when those kick in. With just the circuit with the dishwasher on it on, it happens when that is running. Even with just the sockets circuit on it happens with even a minimal amount of load

I am a competent diyer, but I am good enough to known when I am in over my head so this is an electrician job for sure. My question is though, is there something common in the CU that would cause arcing (I assume it's arcing from the noise) because of load from any of the circuits? Just so I can at least describe the fault better to my electrician so he is prepared

Thanks

 

[BCW126]

I may have answered my own question... It's an MK consumer unit and if I put upwards pressure on the RCD lever the arching/buzzing noise happens or increases

I am guessing that probably shouldn't happen? Is that a possible/common fault?

 

[Harry Bloomfield]

Your description, suggests a poor connection, or loose terminal, probably at the RCD. It will need to be inspected closely for potential damage, and/or signs of heat damage.