Standards as High as Your Own
NECA Online Help Desk Please leave a message
Under table 300.50 - it does not clearly specify (in column 2) if those conduit depth requirements are for direct buried or concrete encased. We have a situation at JFK airport where we are struggling to meet the 18" depth for concrete encasement for runway and taxiway lighting installation (voltage between 1kv and 22kv). Also, in lieu of RGS (for 6" depth), is it compliant to use LFMC - concrete encase?
Hey Al thanks for your question. There is a superscript "c" at the end of the fourth subheading heading (types of conduits) in Column 2 of Table 300.50. The wording in the superscript "c" Specific Footnote indicates that if the conduit listed for direct burial without concrete encasement then concrete encasement is not required.
General Note 2, to table 300.50 allows 2 inches of concrete cover extending down to the rock for metal or nonmetallic raceways permitted for direct burial, if solid rock prevents meeting the cover requirements.
LFMC is not a type specifically included in the table so the local AHJ would need to make that determination.
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. NEISÃ” 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: email@example.com.
© 1999 – 2014 National Electrical Installation Standards. All rights reserved.
Brought to you by NECA. NECA is the voice of the electrical contracting industry NATIONAL ELECTRICAL INSTALLATION STANDARDS, NEIS and the NEIS logo are registered trademarks of the National Electrical Contractors Association.
Created by Matrix Group International, Inc.