National Electrical Installation Standards

Standards as High as Your Own

?
Tuesday, October 10, 2017

Question:

Could you clarify what is meant when Table 110.26(A)(1) refers to "insulating materials". Thanks a whole lot more than you will ever know!

John James

A

Answer:

Hey John thanks for your question and the kind words. We published an answer to a similar question on Friday January 27, 2017. The concept of effectively guarded by insulating materials applies to live parts on both sides of the work space as described in Table 110.26 (A)(1) Condition 1 so materials with rated electrical insulating properties would be suitable.

The wording describing Condition 2 in Table 110.26(A)(1) uses the phrase "grounded parts on the other side of the working space". The last sentence indicates that concrete, brick, or tile walls are considered as grounded. If gypsum board (drywall), wood or some other suitable material was used to cover the concrete wall that was on the other side of the working space most AHJ's would probably consider the Condition 1 distances to be acceptable.

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.