Been looking and thinking on some of the points you raised
I don't find anywhere in the regs that says surge protection shall be fitted
I would suggest you tell the customer to switch the system off asap, unless it is not connected to the grid, as it will damage the inverter and the supplier
Isetech Yesterday, 08:53 AM
How you deal with invalid/ non complaint COC's
Manufacturer's Specifications:
Derlyn Today, 04:30 PMPg 14. Recommended DC Surge Protector.
Pg 17. Recommended AC Surge Protector.
Pg 18. 3.4.1.