(1) Equipment Provided With Threaded Entries for NPT-Threaded Conduit or Fittings
NPT-threaded entries into explosionproof equipment shall be made up with at least five threads fully engaged.
Exception: For listed explosionproof equipment, joints with factory-threaded NPT entries shall be made, up with at least four and one-half threads fully engaged.
Informational Note No. 1: Thread specifications for male NPT threads are located in ASME B1.20.1-2013, Pipe Threads, General Purpose (Inch).
Informational Note No. 2: Female NPT-threaded entries use a modified National Standard Pipe Taper (NPT) thread with thread form per ASME B1.20.1-2013, Pipe Threads, General Purpose (Inch). See ANSI/UL 1203-2015, Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations.