Pictured is the "no longer available" Iota 30 amp transfer switch, It is located in the attic and is used to control one circuit. Following the wiring from the inverter the current goes in to a 30 amp main breaker then out through a 20-amp breaker. When it reaches the house the current passes through a disconnect box where it enters the house on the outside. Then runs direct to the transfer switch. A 20 amp breaker is placed in the homes breaker box and a wire ran to the transfer switch.
This Gives the transfer switch two sources of power. The out put from the transfer switch is ran to a sub panel with a breaker going to the load to be switched for battery backup. The sub breaker panel is a must to disconnect the load if something were to go wrong. The house/grid breaker would trip then switch to the backup power and re-power the line, You could end up with a fire if the backup power breaker don't break. Or you might even fool yourself and think you turned off the power and get the full bite of the inverter. Be safe.
You will notice three cables entering the bottom of the transfer switch. The wire on the left comes from the solar backup system inverter. The cable in the middle is the output to the homes sub panel circuit The cable on the right is the input from the home’s main breaker box. Make sure you hook all the bare ground wires to the ground block shown in the upper left. Do not bond the neutral to the ground in side the switch. That is done in the main control panels. Note the green light top middle shows the transfer switch is engaged and powered by the grid.
This install has been wired to hold the contacts in the transfer switch together when the grid power is present. When the Grid power goes off line it releases and allows transfer switch to switch to the solar backup side powering your survival mode items. If you are off grid replace the grid connection with a generator output so you will be solar powered till the gen starts.