Fronius Primo GEN24 208-240 Operating Instructions Manual page 32

If no energy from the PV modules is available in backup power mode, backup
power mode ends automatically. Backup power mode restarts again automatic-
ally once sufficient energy can once again be provided by the PV modules.
In the event of excessive loads, backup power mode is stopped and the "Backup
power overload" status code is displayed on the inverter's LED status indicator.
The maximum power in backup power mode specified in the technical data must
be observed.
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