National Electrical Installation Standards

Standards as High as Your Own

 
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Monday, August 28, 2023

Question:

Hello Charlie! Thank you for this wonderful service you provide! Does the code allow the installation of a 22/2 cable with 600V rated conductor insulation in the same underground raceway containing the #10 AWG THHN Conductors for a 120V branch-circuit to a piece of equipment (Assuming wire fill isn’t an issue)? Regards, Joe Frieders-IBEW 701
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Answer:

Hi Joe and thank you for the kind words. This is a great question given the restructuring of Chapter 7 in the 2023 edition of the NEC®. The requirements in Article 725 have been separated for ease of application and use as follows:

  • Article 722 – Cable for Power-Limited and Fault-Managed Power Circuits
  • Article 724 – Class 1 Power-Limited, Remote-Control, and Signaling Circuits (Class 1 Nonpower-Limited circuits are covered by Chapter 3). 
  • Article 725 – Class 2 & 3 Power-Limited Circuits
  • Article 726[NEW] – Class 4 Fault-Managed Power Systems

The answer depends on the Class of the power supply the 22/2 cable is connected to:

Class 1 Power Supply - If the supply is a listed Class 1 power supply, then guidance for installing the Class 1 power-limited cable with power conductors in the same raceway is found in Section 724.48(B)(2). If the Class 1 circuit is supplying equipment “functionally associated” with the power equipment. If it is not “functionally associated” then a barrier between the two types of circuits is required.

Class 2 or 3 Power Supply – If the supply is a listed Class 2 or 3 Power Supply, then guidance for installing Class 2 & 3 circuits in the same raceway as power conductors is found in Section 725.136(A) and generally prohibited from being installed in the same raceway.

Class 4 Power Supply - If the supply is a listed Class 4 Power Supply, then guidance for installing Class 4 circuits in the same raceway as power conductors is found in Section 726.136(A) and generally prohibited from being installed in the same raceway.

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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®.

This correspondence is not a formal interpretation of the NEC® and any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, the NEC Correlating Committee any Code-making panel or other electrical technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services. 

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