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Tuesday, October 24, 2023

Question:

Hi Charlie, we are wiring a new house, and the customer wants two (2) EV Tesla Wall Connectors installed in the attached garage. These charging units will be controlled by an Energy Management System (EMS), that is constantly monitoring the total demand on the service at any given time. Based on the current demand, the EMS will either let one or both EV charging units operate. With the EMS in place, do the EV charging units need to be included in the service load calculation? Regards, Justin Murphy
A

Answer:

Hello Justin, great question and very relevant to many installations going on right now. There is a new Code Section 220.70 in the 2023 NEC® regarding the use of an Energy Management System (EMS). This Section provides relief for calculated feeder or service load when an EMS is used in accordance with Section 750.30. The value that can be used for the load calculation is the maximum current setpoint of the EMS for the applicable feeder or service. The setpoint value of the EMS shall be considered a continuous load when performing the load calculations. See Section 750.30(A)-(C) for additional guidance on the operation and application of energy management systems.  

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CHARLIE TROUT: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

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IMPORTANT NOTICE: Unless the question requests a response based on a specific edition, all answers are based on the latest edition of NFPA 70® National Electrical Code®.

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