Electrical Conduit: Basics, Boxes, and Grounding

Electric meter on exterior of house
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With Conduit, You Do Not Have To Embed Wire In Walls

Electrical conduit is metal or plastic pipe through which electrical wires are run.  Either rigid or flexible, conduit protects the wires and is used in exposed locations, such as along the exterior surface of a wall.

This is a great advantage to home remodeling, as opening up walls and resealing them adds considerably to the project's cost.  

Conduit Is Not the Same as BX

At first glance, electrical conduit may seem similar to BX (or AC, for "armored cable") wiring.

 Like conduit, loose but insulated individual wires are encased in BX's metal shell.  Also like conduit, BX can be used in exposed locations.

The difference is that, according to electrical code (NEC 320.12), armored cable may not be used in damp or wet locations, in places where exposed to corrosive conditions, or places where damage might occur.  Conduit allows you to install wire in such locations.

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.

With Pre-Formed Couplings, Shaping Is Easier Than Ever

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.

Use Metal Conduit With Metal Boxes

Metal conduit should be used with metal boxes, not plastic boxes.

Conduit Can Be 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.

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.