AC grid voltage has fallen below lower protection threshold. Inverter disconnects. Auto-reconnects when voltage normalises. Displayed fault ID: 004, 005.
Common causes
Utility grid voltage genuinely below thresholdPoor or loose AC cable connection causing voltage dropUndervoltage protection set too high
What to check
STEP 1
Wait — inverter auto-reconnects. If recurring, measure actual grid voltage at AC terminals.
STEP 2
If below set value, contact DNO/DNSP. Inspect AC cable connections — confirm firmly seated in terminal block.
Escalate if
Fault persists after all checks — contact Sungrow support
Need full interactive diagnosis?
Faultpath walks you through decision trees, fault codes, and commissioning — built for solar & battery engineers.