There are almost as many types of conduits as there are wires and cables. Below are four of the most common types of conduit fittings manufactured.
Rigid Metal Conduit (RMC)
RMCs, or ‘rigids’ are one of the most commonly used conduits in commercial establishments. Rigid metal conduit is heavy-duty galvanized steel tubing that is installed with threaded fittings. It is typically used outdoors to provide protection from damage and can also provide structural support for electrical cables, panels, and other equipment.
Electrical Metallic Tubing (EMT)
These are by far the most commonly used conduits, even though they’re not technically conduits at all (they’re actually classified as tubings). EMTs are made of galvanized steel but can also be aluminum. EMT is also called "thin-wall" conduit because it is thin and lightweight, especially compared to RMC. EMT is rigid but can be bent with a simple tool called a conduit bender. Due to their design, these conduits function best in situations that are prone to rust and corrosion.
Electrical Non-Metallic Tubing (ENT)
Electrical nonmetallic tubing (ENT) are flexible corrugated plastic tubing that is moisture-resistant and flame-retardant. Though there is no code requiring it, ENTs are usually light blue in color. Their non-metallic material makes them resistant to chemicals, moisture, and flames. However, ENTs can only be used indoors, in areas where they will not be exposed to physical damage, hazardous conditions, temperatures over 50°C and the conductors do not carry over 600 volts.
Flexible Metallic Conduit (FMC)
Commonly known as ‘Greenfield’ or ‘flex’ conduits, FMCs are made from spirally wound metal strips that interlock. They’re most often used for the last few feet of wiring, where conventional conduit systems are difficult to maneuver and terminate. They absorb vibrations and allow movement, so they’re often used to house wiring for pumps, motors, and manufacturing equipment.