National Electrical Installation Standards

Standards as High as Your Own

Tuesday, July 26, 2022


Greetings Code Question of the Day,

What is meant by the phrase five full threads fully engaged and being wrench tight as indicated in Section 500.8(E)? Isn’t wrench tight a general installation requirement anyway? Appreciate an opinion on this language in the NEC.

Andy George



Greetings Andy, thanks for the question. Section 500.8(E) is pretty specific and indicates both criteria you mentioned in your question. The five full threads relates to the conduit and fittings being made wrench tight to prevent sparking when fault current flows through the conduit system, and to ensure the explosion-proof integrity of the conduit system where applicable. Wrenchtight is always a general workmanship, as covered in Section 110.12, but also very important in conduit systems installed in hazardous (classified) locations as mentioned above so loose connections or fittings don't become an arcing source in an explosive atmosphere during a fault event. Wrench tight can simply be described as needing a tool or tools to tighten the fittings beyond hand tight. If one holds a conduit with the handle and tightens a coupling or fitting with a tool,  wrench tight is usually not achieved.  

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