The Backup Box is used in a residential rooftop PV plant system to control the inverter grid-tied or off-grid state. When the grid recovers, the inverter switches back to the. The Automatic Switch Box is a switching unit for Backup systems. • Off-grid. A Solar Distribution Box is an electrical enclosure designed to distribute power from one source to multiple circuits while ensuring safety and protection. In a solar setup. This application guide describes all the necessary steps to activate and commission the backup power function with the Fronius GEN24 Plus inverters. GENERAL INFORMATION ABOUT BACKUP.