Random RCBO Trip...What Next?

[carlyai]

Trying to isolate which electrical cct. is causing random trips of a RCBO. 

With all the feed breakers (to greenhouse pumps, aquaphonics pumps and air pumps, pool pump and chlorinator disconnected), the main breaker in the garage CU still trips intermittantly.

I blew out all the red ants etc from the garage CU and thought the problem was fixed, but RCBO still tripping, but not nearly as much. This only started this wet season.

I don't really need the breaker to be an RCBO but installed it before the underground feed to the shed as the underground feed is Al cable (which I now know is a no no) but 7 odd years ago the local electrician said OK.

The circuit: from the 3 phase mains PEA supply to a CU on the 2m block fence, then splits underground to the house CU via 3 single phase stabalisers, then a phase to the RCBO on the fence, then underground to the shed CU.

So to my questions:

1. Can the main shed CU breaker go leaky and should I change it?

2. Should I replace the wall RCBO with a normal MCB?

I don't think the Al cable feed to the shed is a problem, at the moment, even though the conduit probably has water in it, because the Al cable is double insulated and thicker than the recommended underground cable.

This cable will be changed when I install solar on the shed.

Thanks.