National Electrical Installation Standards

Standards as High as Your Own

?
Tuesday, March 12, 2019

Question:

Re: CQD answer published February 21 & March 1, 2019 -Isolated Phase Conductors

Charlie, Most code experts say that the only time you can use an isolated phase installation is per the Exception to 300.3(B)(1). This installation does not appear to be an underground installation. Note, that I don't agree with those experts that say you can only install an isophase installation underground. It appears to me that the language in 300.3(B)(3) would permit it anywhere you want to use it.

Don Ganiere

A

Answer:

Hey Don thanks for your comment, you make a good point and it's good to hear from you. The exception to 300.3(B) is limited to underground installations but the wording in 300.3(B)3 has different conditions and is not limited to underground installations.

ABOUT CQD: NECA’s Code Question of the Day (CQD) is a leading National Electrical Code® forum for NECA and the industry. The CQD generates a lively dialogue and relative practical and Code-based responses to an ever-increasing and interactive audience.

IMPORTANT NOTICE: All answers are based on the latest edition of the National Electrical Code®, unless the question requests a response based on a specific edition. This correspondence is not a formal interpretation of the NEC®. Any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, or any technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services.

ABOUT CHARLIE: 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. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. Visit NECA-NEIS.org for more information. NEISÔ can be purchased in three formats: as paper books, on CD, or as electronic downloads.

NECA SAFETY PRODUCTS: NECA publishes valuable electrical safety books and CDs for the industry. Visit necanet.org/store to view or purchase NECA safety products.

 CONTACT US: To submit a Code question, subscribe, or unsubscribe from this list, please e-mail: codequestion@necanet.org.