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How to Identify Conduit Fittings

Conduit fittings join conduit to boxes and to other conduit. This sheet shows how to tell set-screw, compression, threaded and liquidtight fittings apart and what each is listed for.

Ref EL-0076NEMA FB 1UL 514B

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Conduit fittings include connectors, which attach conduit to a box or enclosure, and couplings, which join two pieces of conduit. The fitting type must match the conduit type and the location: dry, damp, wet or embedded in concrete.

Listing marks on the fitting or carton show what the fitting may be used for, such as raintight, wet locations or concrete-tight.

How to identify

Identify the conduit type. EMT, rigid, IMC, PVC and flexible conduit each use their own fittings. See How to Identify Conduit Types.
Look at how it grips. A screw that presses on the conduit means set-screw. A nut that squeezes a ring around the conduit means compression. Pipe threads mean threaded. A nut, sealing ring and a ferrule that goes inside the conduit mean liquidtight.
Read the trade size cast or stamped on the body.
Read the carton for listing and location marks.
Check the material. Steel and zinc die-cast are common. Malleable iron is used for heavy duty fittings.

Fitting identification table

Fitting	Tells	Used with	Location notes
Set-screw	One or two screws press on conduit	EMT	Dry and damp; check carton for concrete-tight
Compression	Nut and gland ring squeeze the conduit	EMT	Raintight versions listed for wet locations
Threaded	Pipe threads, locknut and bushing	Rigid and IMC	Wet and hazardous locations with the right fitting
Threadless (rigid)	Compression or set-screw for unthreaded rigid	Rigid and IMC	Check listing
Squeeze (FMC)	Clamp squeezes the flex	FMC	Dry locations
Screw-in (FMC)	Threads into the convolutions	FMC	Dry locations
Liquidtight	Nut, sealing ring, ferrule	LFMC, LFNC	Wet locations when listed
PVC adapter	Solvent-weld socket with thread	PVC	Wet locations

Key points

Insulated throats or bushings protect conductors at the box entry.
Steel and die-cast fittings may serve as part of the grounding path only when listed for it.
Straight, 45 and 90 degree liquidtight connectors are common.
See Conduit Fittings — Set-Screw, Compression and Threaded for more on each type.

Common mistakes

Using set-screw EMT fittings outdoors.
Mixing EMT fittings on rigid conduit.
Leaving out the ferrule on liquidtight fittings.
Over-tightening die-cast fittings until they crack.

Governing standards: NEMA FB 1 (fittings, cast metal boxes and conduit bodies); UL 514B (conduit, tubing and cable fittings); NEC articles for each conduit type.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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