The short answer
Backup loads exceed rated power or there is a short on a backup circuit. Check for shorts, then cut loads.
Plain explanation
From the Huawei manual for the SUN2000 + Backup Box/SmartGuard: Check there is no short circuit on backup circuits (installer if unsure). Reduce backup loads below the rated power. The rest of the checklist is below; work through it in order. Owners can do the app and visual checks; any work on the wiring is for the installer.
Steps from the source
- Check there is no short circuit on backup circuits (installer if unsure)
- Reduce backup loads below the rated power
- Switch heavy loads off when sun/battery are low
- Clear the alarm in the app
Source
Huawei Inverter Alarm Reference, Issue 09 (2024-11-01), EDOC1100345192, Alarm 2077, §43, p51files.keno-energy.com ↗
Where installers ask this
- Huawei sun2000 back up box alternative (r/SolarDIY)
- reddit.com/r/DeutschePhotovoltaik/comments/1gcsg73/
- reddit.com/r/DeutschePhotovoltaik/comments/1q5d0ks/
General guidance based on the manufacturer's manual or the named source. Always follow the current manual for your exact model and your national code. DC and AC electrical work is for qualified installers only. Not affiliated with or endorsed by any brand named; trademarks belong to their owners.