Electrical Conduit, Couplings and Fittings

What 1/2 in and 1 in really mean on conduit

Conduit sizes such as 1/2 in, 3/4 in, 1 in and 1-1/2 in are trade sizes, not measured outer diameters, so a 1/2 in conduit is wider than half an inch outside. Fittings, couplings and connectors must match both the trade size and the conduit type: rigid steel uses threaded couplings, EMT uses set-screw or compression fittings, flexible conduit uses its own connectors, and PVC uses solvent-welded ones. Mixing types, even at the same size, will not seat or seal.

Steel, stainless, aluminum or plastic for the environment

Galvanized steel suits most indoor runs and is tough where cables might be hit. Stainless steel, such as the 316 grade named in some titles, resists corrosion in wet, coastal or washdown areas. Aluminum is light and easy to handle, and PVC does not rust but softens in strong heat. Wet locations also need raintight or compression fittings, and a knockout seal closes an unused hole in a box.

Clamps, cable ties and wire staples sit in the same department. Pick nylon ties rated for sunlight outdoors, and size staples to the cable so they hold it without crushing the jacket. A few entries are electronic D-sub connector pairs rather than pipe parts, so confirm the title names a conduit part, coupling, clamp or tie before you compare sizes.

Questions about Electrical Conduit, Couplings and Fittings

Can I mix EMT and rigid fittings?

No. EMT is thin-wall tubing joined with set-screw or compression fittings, while rigid steel is thick-wall pipe joined by threads. A coupling for one will not grip or seal on the other. Match the fitting to the conduit type and the trade size.

How many wires can go in a conduit?

Wiring codes limit how full a conduit can be, depending on the conductor size, count and insulation. The limit leaves room to pull wires and shed heat. Use the code's conduit-fill tables or the fitting maker's charts, and go up a size if in doubt.

What does a knockout seal do?

A knockout seal plugs an unused punched hole in a metal electrical box or panel so that dust, insects and debris stay out and the enclosure remains closed. Choose it by the knockout's trade size, commonly 1/2 in or 3/4 in; like conduit sizes, these are not the measured hole diameters.