National Electrical Installation Standards

Standards as High as Your Own

?
Friday, May 27, 2022

Question:

Good Afternoon and thanks for your work in this forum. My application is a 480Y277 generator with an integral 2000/3-pole circuit breaker. There will be (11) sets of individual cables, #4/0 Type XHHW between the generator and transfer switch. The transfer switch will pick up the entire building load, i.e. premise and equipment. I am trying to determine the size and number of the ground conductor(s) required between the generator and the transfer switch. Can you help me out, please?

Pat Wolff

A

Answer:

Hello Pat, thanks for participating. We'll answer the question based on the information provided. You use the term "ground conductor" and we will assume you mean "equipment grounding conductor." Session 250.122(F) requires where conductors are installed in parallel in multiple raceways, that the equipment grounding conductors shall be installed in parallel in each raceway. there are 11 raceways based on the question. Note the last sentence of 250.122(F)(1)(b) in the 2020 NEC, indicates that each equipment grounding conductor shall be sized in compliance with 250.122 based on the rating of the feeder overcurrent protective device. The equipment grounding conductor(s) required for this feeder installation in accordance with Table 250.122 (2000 amperes) is a minimum of 250 kcal copper.

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 codequestion@necanet.org

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.