National Electrical Installation Standards

Standards as High as Your Own

Friday, August 23, 2019


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


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:

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

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.