Important Notes on UL 1741 PCS Compliance

Note

A system equipped with a Power Control System (PCS) must be suitably rated to provide branch circuit overcurrent protection. The controlled current setting shall not exceed the rating of any controlled panels or conductor ampacity.

Warning

Configuration of Power Control System settings or changes to settings shall be made by Qualified Personnel only. Incorrect configuration or setting of the power control settings may result in unsafe conditions.

Note

Maximum PCS Controlled Current setting: 200 A.

Note

The maximum operating currents in controlled busbars or conductors are limited by the settings of the Power Control System (PCS) and may be lower than the sum of the currents of the connected controlled power sources. The settings of the PCS controlled currents may be used for calculation of the design currents used in the relevant sections of NEC Article 690 and 705.

Monitoring (2020 NEC, 705.13 (A), UL 1741 PCS)

Tesla Site Controller receives meter data from the Backup Switch (Meter Z), Gateway 3 (Meter Z), or Backup Gateway 2 (Meter X and/or Meter Y), and/or Remote Energy Meter(s).
Tesla Site Controller receives controlled current data of the AC output of the Powerwall and controlled solar.
Each limit is monitored by a metering device as follows:
- Panel Limits are monitored by adding together the current flowing into the Virtual Panel (net current from Site, Solar, and Battery). The limit is enforced on the sum of all phases.
- Site Limits are monitored by the sum of all Site meters. The limit is enforced on the sum of all phases.
- Conductor Limits are monitored by each Conductor meter. The limit is enforced on each phase independently.
Where communications are lost with the relevant meter(s), all controlled power production sources are curtailed.

Settings (2020 NEC 705.13(B), 2023 NEC 750.30(C)(1), UL 1741 PCS 201.9)

Each default is as follows:
- Panel Limits by default are automatically configured with an 80A Panel Limit for all Powerwall 2, Powerwall+, and Powerwall 3 installations. As 100A is the minimum allowable size for a single family dwelling per NEC 230.79 (C), this protects any main panel busbar for a single family dwelling with any quantity of Tesla Powerwalls (80A is 80% of the 100A minimum service size).
  Note
  The minimum allowable size for multifamily dwellings is 60A, and downstream subpanels may also be smaller than 100A.
- The maximum current output is 48 A by default. The installer can configure a maximum current output of 41.7, 31.7, or 24 A in Tesla One.
- Site Import Permissions are by default set to allow charging from grid. However, charge from grid can only be enabled by the customer in their Tesla app. Unless the customer sets Grid Charging to Yes, the system will not charge from grid.
- Site Export Permissions are by default set to allow solar-only export.
- Site Limits are not set by default.
- Conductor Limits are not set by default.
The PCS limits can be verified by viewing the Summary page in Tesla One.

Overcurrent Protection (2020 NEC 705.13(C) and UL 1741 PCS 201.2)

The Tesla Site Controller software is certified under UL 1741 PCS as secondary overcurrent protection.
Overcurrent protection devices are still required for each circuit as required by the National Electrical Code.
Overcurrent protection devices shall be sized in accordance with the ratings of conductors, panels, and related equipment as required by the National Electrical Code.
Software manages the output of the battery and controlled solar in a best effort approach to prevent exceeding each of the configured limits.
- For Panel Limits, software curtails battery and/or controlled solar to prevent exceeding the configured limits.
- For Power / Current Limits (Powerwall 3 only), software curtails controlled solar to prevent exceeding the configured maximum current output.
- For Site Limits, software both curtails battery and/or controlled solar, and compensates by having Powerwall charge or discharge to prevent exceeding the configured limits.
- For Conductor Limits, software both curtails battery and/or controlled solar, and compensates by having Powerwall charge or discharge to prevent exceeding the configured limits.
- Once battery and controlled solar have been curtailed, or if they have no additional power or energy with which to compensate for loads, the balance is fed from the grid.
- Accordingly, breakers should be sized to protect all conductors, busbars, and equipment on site, as intended prior to the addition of secondary power sources.

Single Power Source Rating (2020 NEC 705.13(D) and UL 1741 PCS 201.9)

Each Powerwall 2 connection to the electrical panel requires an independent 30 A circuit breaker.
Each Powerwall+ connection to the electrical panel requires an independent 50 A circuit breaker.
Each Powerwall 3 connection to the electrical panel requires an independent circuit breaker; the default breaker size is 60 A, but may be smaller if configuring a Power / Current Limit (see Power / Current Limit Feature for Powerwall 3).
This breaker serves as the disconnect for the unit and must be wired in accordance with local wiring codes and regulations.
This breaker is by design smaller than the smallest panel used within the system.
The service disconnect overcurrent rating can remain unchanged through the use of the PCS.

Access to Settings (2020 NEC 705.13(E), 2023 NEC 750.30(C)(3), UL 1741 PCS 208.1(F))

Panel Limits, Site Limits, Conductor Limits, and/or Power / Current Limits can be configured by Qualified Personnel (Tesla or Certified Installers) in the Tesla One app, which is password-protected.
- For Panel Limits, a limit of 80A is auto-enabled for all Powerwall 2, Powerwall+, and Powerwall 3 systems. Qualified Personnel can change this limit in the Tesla One app.