1021 on a Sigenergy SigenStor: Inverter AC side voltage abnormal. Official suggestion (summarised): Reduce load; check for short circuits; check gateway inverter-side breaker
Short answer
On a Sigenergy inverter, 1021 means: Inverter AC side voltage abnormal. Official suggestion (summarised): Reduce load; check for short circuits; check gateway inverter-side breaker. The inverter stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Inverter AC side voltage abnormal. Official suggestion (summarised): Reduce load; check for short circuits; check gateway inverter-side breaker.
Likely causes:
- Off-grid overload/short, gateway inverter-side breaker not closed, grid or generator out of range.
Is it safe?
| Does the inverter stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The inverter stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: n/a.
What you can check
- Read the alarm code, name and ID in the mySigen app.
- Report it via mySigen app Support > Troubleshooting (Sigenergy's stated route) or contact your installer.
- During a power cut, switch off large loads (backup overload).
What the engineer will check
- Check load circuits for short; check Gateway INV-port breaker.
- Sub-IDs: ID1 AC overload; ID2 AC short circuit; ID3 AC overvoltage; ID4 AC undervoltage; ID5 overfrequency; ID6 underfrequency.
Who to ask for: battery storage / PV inverter.
Certification: Sigenergy-trained installer; MCS PV/battery installer for certified installs; electrical work to BS 7671.
What you might notice
Sources
- Sigenergy Alarm List (Version 05) ↗ · 05 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026