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NOTE: If the battery mode needs to be changed after the selection has expired in the Enphase Installer App, contact Enphase Support. The Battery mode can only be changed based on the validity of the claim. 5.3 MPU avoidance MPU avoidance with Busbar Overload Control allows maximum renewable energy generation and helps avoid the cost of panel upgrades for large PV and battery systems under the National Electric Code (NEC) 2020 705.13, reducing the system payback period. MPU avoidance with Feeder Control enables avoiding the cost of panel upgrades for large PV and battery systems by controlling the backfeed current into the main panel according to the National Electric Code (NEC) 2020 705.12. The feature ensures that the backfeed current allowed into the main panel is limited according to the configuration provided by the installer for both grid-tied and grid-forming configurations. The MPU avoidance feature can be configured using the following three options: •Using Busbar Overload Control •With Feeder Control (using the NEC 120% rule) •With Feeder Control (using the Current Limit Directly Entered) 5.3.1 Compliance with regulations Compliance of MPU avoidance Busbar Overload Control with NEC 2020 705.13 According to the National Electric Code (NEC) 2020 705.13 (A) through (E), the Enphase Power Control feature, MPU avoidance with Busbar Overload Control, controls the backfeed from the Enphase Power Control features 25 © 2025 Enphase Energy Inc. All rights reserved. August 2025 TEB-00269-2.0-EN Enphase PV and IQ Battery 10C such that the sum of the backfeed current from the DERs and the current being drawn from the grid is equal to or less than the rating or the ampacity of the busbar. Compliance of MPU avoidance with Feeder Control using the NEC 120% rule or the current limit directly entered with NEC 2020 705.12 The National Electric Code (NEC) 2020 705.12 allows backfeed of current from solar or storage into the main panel, subject to the following limit: Backfeed or continuous current from DERs allowed ≤((120% of busbar rating) – ampacity of the overcurrent protection device protecting the busbar)/125%. NOTE: The NEC 2020 705.12 section also contains other articles (such as the sum of breakers) that may be used to determine the backfeed limit. However, using the above calculation is the most common. Later in this document, this rule may be referred to as the NEC 120% rule. 5.3.2 MPU avoidance using Busbar Overload Control When the option to use MPU avoidance using Busbar Overload Control is selected, the feature continuously monitors the backfeed current (Ibackfeed) using the integrated Backfeed CTs, and current entering the main panel from the grid Consumption CTs (Iconsumption) respectively. It then limits the current from the battery (Ibattery) and PV (Iproduction) in real time such that the total current entering the busbar does not exceed the busbar ampacity. The diagram for MPU avoidance with Busbar Overload Control in the grid-tied configuration is shown in the following figure. Enphase Power Control features 26 © 2025 Enphase Energy Inc. All rights reserved. August 2025 TEB-00269-2.0-EN