A supply-side connection or line-side connection is a form of interconnection that is typically used when your main electrical panel is not suitable to handle the inverter breaker and it is not possible to downsize the main breaker and upgrading the main electrical panel is not an option. In a supply-side connection, you bypass the main electrical panel and main breaker altogether, to tap or connect to the conductors going from the main service meter into your electrical panel. When doing this, the installation is no longer limited by the 120% rule and you can backfeed as much as the feeder conductors allow, which generally is more than enough for any system size you may need.
When doing a supply-side connection, instead of using a breaker as OCPD for the inverter (since you are not installing a breaker on the busbar of the electrical panel), you would instead use a fusible AC disconnect, which has fuses inside that act as the overcurrent protection. The fuses must be sized according to the same rules as sizing breakers.
Please note that you must make sure you check with your local utility first and get your permit plans approved before you start any work.
IMPORTANT: For this method of interconnection, we must rely on a licensed electrician, since working with the supply side of your electrical service can be very dangerous and requires coordination with the utility (to cut power to your home or pull the main meter).
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