NEC 705 Interconnection Code Compliance

705.12 Code Compliance

Powerwall 3 has a UL1741 inverter, so NEC 705.12 must be considered in the design of Powerwall systems.

Max continuous AC output current = 48A

NEC 2020 705.13 Power Control System (PCS) (Also Called Energy Management System, or EMS)

Powerwall 3 and the Backup Gateway 2 / Gateway 3 / Backup Switch have achieved UL 1741 PCS certification, which allows Powerwall to limit its charge/discharge rate to programmed limits. This feature can be used to comply with NEC 705.13 without the need to upgrade main panels or perform load relocations, saving both time and cost on installations. PCS can be utilized when the AHJ is on NEC 2020, or when the AHJ allows PCS as a means for complying with 705.12. See the Power Control System (PCS) Features for Powerwall Systems application note for more information.

Note

Any uncontrolled power sources must still comply with NEC 705.12.

Electrical Configuration Examples with Compliance Notes


Powerwall 3 interconnected on the load side of the service A 60A overcurrent protection device in the main panel The Backup Switch acting as the islanding relay at the meter	NEC 2020 / 2023 705.13


Powerwall 3 interconnected on the load side of the service A 60A overcurrent protection device in the main panel The Backup Switch acting as the islanding relay at the meter The Power Control System in the Powerwall units limit the current and loading on the bus and conductors to meet 705.13 requirements Main Service Panel does not support hold down kit requirement, so Powerwall 3 breaker is placed in subpanel that can support hold down	NEC 2020 / 2023 705.13


(2) Powerwall 3 units interconnected on the load side of the service Overcurrent protection device in a load center with backup loads The Backup Gateway acting as the islanding relay	NEC 2020 / 2023 705.13


*Powerwall 3 interconnected on the supply side of the service in the main panel Overcurrent protection device in the Powerwall load center The Backup Switch acting as the islanding relay at the meter Note that there cannot be any backup loads downstream of the supply side connection	NEC 2020 / 2023 705.13

*Supply side configurations will only be used in areas where detached service meters are allowed.


Powerwall 3 interconnected on the load side of the service Overcurrent protection device in a load center with backup loads The Backup Gateway acting as the islanding relay	NEC 2017 705.12(B)(2)(3)(b) NEC 2020 705.12(B)(3)(2) NEC 2023 705.12(B)(2)


Powerwall 3 interconnected on the load side of the service A 60A overcurrent protection device in the main panel The Backup Switch acting as the islanding relay at the meter 12V emergency stop button can be installed with the Powerwall 3 to initiate rapid shutdown per 690.12(C) requirements See the installation manual for additional details	NEC 2020 / 2023 705.13