Think I have sorted this out now
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Get to job this morning - nice bright sunny day so panels are well upto some fun.
RCD had tripped out again, so re-set and go look at inverter, which duly fires up after 180s and trips RCD straight out.
Go back inside and remove earth at CU fire up again - perfect, 2kW from 2.16 kWp system. Touch earth to earth bar - trips staright out. Check out RCD seems to be working fine bar ramp test is 65mA. Test IR >299Mohm all conductors. Attach digital multimeter between earth and earth bar - trip... Reset system and wait for it to start, as soon as the sun peaks out from behind cloud, and system rises to measured 5mA - trip???
So leave earth out again and just run system for 30 mins - no problem, it's a windy day here in sunny Devon so overhead cabling getting a good shake. Still no problem. Notice it's not VOELD but early 100mA RCD on existing electrics, so this seems to rule out incoming supply issues. (system is TT, Ra 21 Ohm with bonding attached)
Getting very confused now as I can't find anything wrong with any part of the system. So take wander out to van to inspect the supply of come-in handy MCBs RCDs etc etc. Dig out Hager 30mA RCD on grounds that it may be a 'make' issue.
Fit hager unit - struggle to see bus bar in bottom of Newey MCB (missed it 3 times. Finally get system fired up and hey - presto it's all working with the sun out to play.
Conclusion :-
1/ Control Gear RCds don't like inverters????
2/ We missed busbar and had poor contact between MCB clamp and busbar.
I think it was possibility 2 - unfortunately I didn't notice if it was clamped properly when dropping bus-bar out to change RCD. In my defence the CU is at the back of a fairly dark cupboard. This option I feel fits better with the whole scenario of the more power the panels are making, the more often it trips RCD, and problem was escalating ie tripping more often. Didn't observe any witness marks on bus-bar though. The customer had previously observed that it seemed to trip RCD when sun was out and also fits with the scenario that the system would happily start-up every day and fail around mid-morning (south facing array).
Any way, fingers crossed, no more e-mails from customer so-far
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