National Electrical Installation Standards

Standards as High as Your Own

?
Friday, August 23, 2019

Question:

Can an offset nipple be installed between a 1900 box and through with locknuts?

Being told by the AHJ that it is not listed for that type of installation due to tapered threads? Please reference the code section other than 110.3B

Thank you,

Stan Komorowski
A

Answer:

Hey Stan thanks for your question. Yes. Field threaded conduit must be threaded with a 3/4 inch per foot taper as stated in 344.28 and is commonly connected using locknuts as stated in 250.92(B) and 250.97 so the tapered threads are not a problem. But the answer is actually based on 110.3(B) even though that is not what you requested.

The AHJ might be thinking about the use of straight threads on fittings that are threaded into hubs or couplings. The wording in UL Productspec has changed to require fittings, that are intended for securement into threaded entries, be marked on the smallest unit shipping carton to indicate that. Previous wording was "All male threaded fittings and nipples have only been investigated for use with locknuts." See the following for more information:

http://productspec.ul.com/details.php?ccn=DWTT

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.