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 303 (NE/PE abnormal) on the screen, with the fault LED illuminated. Startup or operation is blocked.
Technical Causes:
- Voltage difference between neutral (N) and protective earth (PE) exceeds threshold (typically >20-30V).
- Poor or missing PE connection.
- Faulty neutral wiring or grid-side grounding issue.
Diagnostic Procedure:
- Measure voltage between N and PE at inverter AC terminals.
- Inspect PE conductor continuity and connections.
- Verify neutral wiring integrity.
Resolution:
- Secure or repair PE and neutral connections.
- Ensure proper system grounding per local standards.
- Restart inverter after correction.
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.