Disclaimer: This content is for informational and educational purposes only. The diagnostic steps described are suggestions, not an official service manual.
Phenomenon:
The inverter displays Error 129 on the screen or app, with the fault LED illuminated. The inverter stops feeding power to the grid and may attempt reconnection cycles.
Technical Causes:
Grid voltage or frequency temporarily outside the inverter’s permissible range per the selected safety standard.
Incorrect grid safety settings selected for the installation country/region.
High AC cable impedance causing voltage rise at the inverter terminals during export.
Diagnostic Procedure:
Measure AC grid voltage and frequency at the inverter terminals using a true RMS multimeter.
Verify the selected safety standard in advanced settings matches local grid requirements.
Check AC cable sizing and length for voltage drop/rise compliance.
Resolution:
If grid parameters are out of range, wait for grid stabilization or contact the utility provider.
Adjust grid voltage/frequency limits if permitted by local regulations (requires installer access).
Reduce export power or optimize AC cabling if impedance-related.
Restart the inverter after confirmation of stable grid conditions.
WARNING: Maintenance and repair of PV systems, high-voltage DC, and AC components must only be performed by certified professionals with valid electrical qualifications (e.g., SEP/G1 in Poland, or local European equivalents). Unauthorized opening of the inverter housing will void the warranty and carries a risk of electric shock or fire.
In case of persistent hardware failure, the only authorized path for repair is contacting the official Growatt Service Department.