This is a link to the AMSolar Smart Phase Selector:
https://static1.squarespace.com/stat...or+Diagram.pdf
Also to note, I will be removing the inverter installed by Keystone.
Just a comment on battery options. I currently have a 300ah ReLion 8D battery and will go that route again. It has a built in BMS which has worked flawlessly and being an 8D negates the need for for battery interconnects. This along with the built in BMS simplifies the install. I have measured the battery compartment on the 3120RL to confirm it fits.