Supply-side connection

A supply-side connection ties an interactive PV system or other interconnected source in on the utility side of the service disconnecting means. It is made by tapping the existing service conductors or bus, or by installing new service equipment. It is chosen when meeting the load-side connection rules becomes impractical or too costly, and larger installations often need it. The connection needs a service-rated disconnect and overcurrent device rated at least 60 A. Its interrupting (AIC) rating must cover the maximum available fault current, which is generally 10,000 A or less for residential services. The combined ratings of the overcurrent devices supplying the service conductors must not exceed the ratings of those conductors. The tap can be made at or ahead of the main distribution panel, before the existing service disconnect, or on the load side of the meter socket if its terminals allow. Extra junction boxes can be added to give room for the tap, and large commercial switchgear often needs an NRTL field evaluation to keep its listing. Enphase states that supply-side connection is permitted and points to section 705.12 of the NEC 2017, 2020 and 2023 editions. It is used with microinverter, DC optimizer and string inverter systems, and as the point of interconnection for behind-the-meter solar plus storage systems.