OP
Geordie Spark
I have only skimmed through this thread as I am eating a sandwich and I am enjoying it, however..
Low powered loads dont trip the RCBO!!
High powered loads do trip the RCBO!!
Perhaps it's nothing to do with earth current?
What is the ampage of the RCBO? Clamp at CU see what it is drawing.
Please tell us more about your sandwich. I think it could be a lot more interesting than this RCBO.