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.
Note
Every electrical panel within
the system, whether inside or outside the backup circuit, must comply with NEC
705 requirements.
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