National Electrical Installation Standards

Standards as High as Your Own

Thursday, September 14, 2023


Hello Charlie, I have a question regarding your answer to Tommy for August 29, 2023, CQD on a TESLA wall connector and the required wire and breaker sizes. Wouldn’t Section 240.4(B) permit the use of a 60A OCPD on #6 AWG NM Cable, using the next size up rule? For his question, 240.4(B) can allow for a 60-amp breaker to be used on 55-amp rated #6 NM-B (Romex) cable. Thanks, Rich Cressotti


Hello Rich, thank you for your comments and feedback regarding 8/29/23 CQD.

Here is some additional information for clarification:

  • Section 210.19(A)(1)(a) requires branch-circuit conductors supplying continuous loads to have a minimum ampacity not less than 125% of the continuous load served.
  • Section 334.80 requires the ampacity of NM Cable to be calculated using the 60º C column of Table 310.16, limiting the ampacity of the #6 AWG NM Cable to 55A.
  • The TESLA Wall Connector has a maximum output is 48A, as a continuous load, the ampacity of this unit calculates to (48 x 1.25) = 60A.
Regardless of what Section 240.4(B) permits for the OCPD, the conductors still need to be sized according to the continuous load served, so 55A rated conductors would not be acceptable for a 60A load, thus #6 AWG NM Cable would not be permitted.

ABOUT CQD: The Code Question of the Day (CQD) is NECA and ELECTRICAL CONTRACTOR Magazine’s flagship National Electrical Code (NEC®) public forum for the industry, sponsored by EATON. The daily distribution of Q&A generates a lively dialogue and shares relative Code-based practical responses.

SUBMIT YOUR CODE QUESTION: Click here to submit a question to for inclusion in an upcoming edition of the Code Question of the Day, or email

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.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. NEIS can be purchased in the NECA Store in three formats: a printed or  PDF download of a standard or, as an  annual subscription service.

NECA SAFETY PRODUCTS & PUBLICATIONS: NECA produces electrical safety publications and products for the industry including jobsite safety guides, handbooks and resource kits. View a full listing of available resources and products »

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. 

UPDATE YOUR SUBSCRIPTION PREFERENCES: Subscribe or Unsubscribe from this list.