Types of Conduit

The two main types of metallic conduit and raceway are rigid and flexible. Rigid conduit offers solid protection. Flexible metal conduit allows for bends and twists without using extra hardware.

Prewired conduit, or armored cable, offers an all-in-one solution with the wires already running through it. Metal electrical boxes must be used with metal conduit.

Rigid metallic conduit is most often used in commercial applications. It can also be a smart choice for straight runs of wire or cable through an attic, garage, basement or crawlspace. It protects against nicks, cuts and punctures to wiring from accidents or chewing animals.

Examples of rigid metallic raceways are:

• Electrical metallic tubing (EMT): Lightweight and easy to install
• Intermediate metallic conduit (IMC): Has a thicker, galvanized wall, making it suitable for outdoor applications
• Galvanized rigid conduit (GRC), which is thickest and offers the most protection

Flexible metal conduit allows for bends and twists without the use of extra hardware. It allows for turns at corners without using elbow joints.

Tip: Running a green grounding wire is recommended when using conduit. However, electrical code may allow the metal conduit itself to serve as grounding conductor.

Nonmetallic conduit and raceway also comes in rigid and flexible types.
Metal or plastic boxes can be used with nonmetallic conduit.

• Nonmetallic conduit is typically made from PVC. It’s a good choice for outdoor residential applications.
• Blue electrical nonmetal tubing (ENT) is for indoor use only. Some code-compliant PVC fittings can be used with ENT inside walls, floors, some ceilings or encased in concrete.
• Outdoor flexible nonmetallic tubing is strong, watertight, non-corrosive and weighs less.
• Always run a ground wire when using PVC conduit.

High-Density Polyethylene

• Lightweight and durable
• Highly resistant to corrosive elements
• Often used for data and communications cables
• Good for in-ground use
• Not used indoors

Intermediate Metallic Conduit

• Thick, galvanized walls
• Can be used outside. A good choice for exposed outdoor use
• Can also be used indoors
• Approved for all interior applications
• Weighs less than GRC, so it’s easier to work with

Channel Raceway

• Available in metallic and nonmetallic
• Runs across the surface of walls. Allows cables and wires to be run without cutting into the walls
• Good for installing new switches, home theater systems, telephones and more
• Can be painted to blend with existing decor
• Use indoors for electrical or telephone wires, or audio, video data cables

Armored Cable

• Pre-wired conduit
• Metallic sheath
• Spiral construction for high degree of flexibility
• Metallic armored cable is commonly known as BX or MC
• For indoor use

PVC

• Won’t corrode or rust
• Requires a separate grounded wire
• Most economical solution
• A common choice for electricians
• Can be used indoors in walls or ceilings and outdoors
• Good for in-ground and above-ground use

Additional types of conduit include:

Electrical Metallic Tubing (EMT)

• Lightweight steel tubing that is easy to install
• Can be bent or cut with the appropriate tools
• EMT conduit is more affordable than IMC or GRC, but its thin walls are more easily punctured. Most often used in dry interior spaces
• Can be used in damp locations with corrosion-resistant hardware and rain-tight fittings

Flexible Metal Conduit

• Easy to install
• Has a spiral construction for a high degree of flexibility.
• Commonly referred to as “Greenfield”
• Useful in places where rigid conduit is difficult to install.
• Also a good choice for vibrating equipment, such as heating and air conditioning units

Galvanized Rigid Conduit (GRC)

• Offers the highest level of protection at a higher cost
• Available in galvanized aluminum, galvanized steel and stainless steel
• Good for straight runways
• Its threaded ends require threaded fittings
• This rigid metal conduit is approved for all interior applications. Can also be used outside

Liquid Tight Conduit

• Available in both metallic and nonmetallic configurations
• Metallic configurations generally have a plastic coating to prevent water from penetrating.
• Protects wires from moisture
• Intended for use in wet or corrosive locations indoors and out