National Electrical Installation Standards

Standards as High as Your Own

Friday, August 18, 2023


Hello Charlie, years ago when I was learning the trade my boss would always use the three-piece threaded coupling for joining rigid pipe together when bends wouldn't line up by just tightening it with a wrench. However, recently I ran across an electrician that said all he did was take a normal threaded coupler and then cinch it down tight after aligning the bends with a standard lock nut. Is this a common practice that meets the requirements of the NEC® for being wrench tight? Thanks in advance, Eric Bridgestone


Hi Eric, great question. This comes down to the listing of the fitting(coupling). Section 300.15 requires fittings to be used only with the specific wiring methods for which they are designed and listed for use with. The installation instructions associated with a threaded rigid coupling would dictate whether the use of a locknut is allowed. Also check Section 500.8(E)(2) as rigid metal conduit installed in hazardous locations requires threaded fittings to be made up of at least 5 threads.  

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