Equipment with Threaded Entries

For listed explosionproof equipment, factory threaded entries shall be made up with at least _____ threads fully engaged.

a) 4
b) 4.5
c) 5
d) 6

See answer and applicable Code reference

The correct answer is: b) 4.5

Article 500 covers the installation requirements in hazardous (classified) locations. Section 500.8 focuses on equipment. As per 500.8(E)(1), "For equipment provided with threaded entries for NPT threaded conduit or fittings, listed conduit, conduit fittings, or cable fittings shall be used. All NPT threaded conduit and fittings shall be threaded with a National (American) Standard Pipe Taper (NPT) thread. NPT threaded entries into explosionproof equipment shall be made up with at least five threads fully engaged." However, an Exception notes: "For listed explosionproof equipment, joints with factory threaded NPT entries shall be made up with at least 4.5 threads fully engaged."


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