Adding a second, separate system is an option for expanding a grid-tied PV system. For systems connected on the load side of the main AC service, the size of the existing equipment can limit this option, as the amount of breakers supplying power to the busbar are limited to 120% of the busbar rating. For instance, if an existing PV system backfeeds a 30 A breaker in a 200 A service with a 200 A main disconnect and busbar, only 10 A of additional backfed PV breakers could be added without reconfiguring the interconnection or service.
Two separate systems, side by side: A little forethought allowed the use of shared AC and DC disconnects, a wiring chase (gutter), and connection to the mains panel.
