F55 - DC_VoltHigh_Fault - Solved!
Seems to be a bit of a common one, found the cause of mine - sparky didnt clamp the grid cables, inserted them behind the clamp:
My thoughts on what & why the F55 is...
Its due to high voltage on the PV Input - not battery.
Solar panels have a Voc & Vmpp, Voc is voltage when the soalr panel is open circuit, Vmpp is the voltage when the panel is under load (optimal load). My panels as an example: Voc 51.4, Vmpp43.2 I have 9 panels in a string: Voc 462v, Vmpp 388v The inverter (8kw) is rated to 500v max DC, 425v MPPT (425v from memory) The 500v is for Voc - which i'm under The 425v is for MPPT - which i'm under
Since the grid cables were loose, the connection was being lost intermittently for a fraction of a second, or there was high impedence restricting how much power could flow back to the grid. The MPPTs have some sort of "sense circuit" to detect if the grid is there, they'd have some capacitor smoothing or similar, so during these "micro outages" the MPPT grid sense wouldnt detect them & be turned "on" all the time. So the inverter thought it was always connected to the grid & in "MPPT On mode" which means max PV voltage of 425. When a "micro outage" would occur - the panels couldnt push the current back to grid, so the voltage would rise to the Voc level. So the PV goes to Voc for a fraction of a second, and the MPPTs are "on" - causing it to think that the PV is above the 425 limit. If you get this error - check the AC connections!!! - Screw terminals in the inverter - Terminals in the breaker board - Replace the breaker, internal terminals could be higher resistance Always tug on the cables to check they're tight, a thermal camera that plugs into your phone is $100-300AU - run your inverters & batteries hard for an hour & look at everything!!!