Electrical conduit is metal or plastic pipe through which electrical wires are run. This conduit protects the wires and is usually used in exposed locations, such as along the outer surface of a wall.
Flexible Conduit vs. Rigid Metal or Plastic Conduit
Flexible metal conduit typically comes in 1/2" to 3/4" sizes and is used in spaces where rigid, nonflexible conduit is hard to install. Flexible conduit is also easier to work with. Rigid metal or plastic conduit provides a higher degree of protection for the electrical wires than the flexible conduit.
Shaping Rigid Conduit
In the past, specialized tools were needed to form the intricate bends and curves needed to thread rigid conduit through spaces. While this type of conduit is still used, homeowners can also find a wide variety of pre-shaped couplings that can be used instead of bending the conduit.
Metal Conduit and Boxes
Metal conduit can be used only with metal boxes, not plastic boxes.
Metal Conduit Used With THHN/THWN Wiring
The type of wire that is installed inside of conduit is called THHN/THWN. Romex wiring
is not used inside conduit. THHN/THWN wires are individual, plastic-coated and color-coded wires. In fact, they are similar to the wires you see when you strip the sheathing off of Romex.
Metal Conduit Acts As A Ground
Metal conduit acts in place of the green grounding wire that is found in Romex (thus the reason why only metal boxes may be used with metal conduit). However, many electricians still like to run the green grounding wire through metal conduit as an extra-safe means of grounding the system.