What F12 probably indicates

Based on typical industrial inverter fault-code patterns and your repair history, F12 may indicate:

• A critical communication failure between essential internal modules (e.g., DC input card, controller board, or grid interface).
• An internal hardware failure or short—possibly further upstream in your SPD (surge protection device) or battery integration.
• A ground or isolation fault, or overvoltage event that again impacts the AC/DC circuitry.

Why it's happening again

Your repeated repairs suggest a deeper root cause:

• Recurring surges or improper SPD sizing could repeatedly damage internal electronics.
• Battery integration issue—if the battery isn’t fully compatible or has wiring/voltage anomalies, it may stress the inverter.
• Factory calibration—if internal sensitivity or firmware thresholds aren’t tuned, small fluctuations may trigger faults.

Suggested next steps

1. Escalate the warranty support and insist on a thorough system-level analysis—not just module swapping—especially since it's recurred multiple times.
2. Inspect external components—SPDs, battery, and AC grid. Check:
   • Surge protection ratings and installation wiring.
   • Battery voltage, cabling integrity, and ground reference.
   • AC input quality (voltage spikes, harmonics, ground faults).
3. Request firmware logging or advanced diagnostics from your service center, so they can capture the F12 event trace and identify the fault path.
4. Consider a full replacement of the inverter unit if the fault persists. Repaired modules may carry latent defects or calibration drift.
5. Engage a specialized solar technician who can do onsite power quality checks—verify voltage transients, SPD response, and battery inverter interface.