National Electrical Installation Standards

Standards as High as Your Own

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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

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