Raceway Types and Their Characteristics

Although a very few types of conductors are rated for use without a raceway (such as for direct burial or for aerial installation), most conductors require protection in the form of a raceway. The most common raceways are conduit (both the metallic and nonmetallic) and sheet-metal wireways of various configurations. For the convenience of the engineer or designer selecting a raceway type for a particular installation, a brief summary of the types of raceways normally used, along with their trade names, is as follows:

• Rigid metal conduit (RGS). Can be made of heavy-wall steel or aluminum.

• Intermediate metal conduit (IMC). Normally made of steel conduit.

• Electrometallic tubing (EMT). Thin-walled steel conduit.

• Electric nonmetallic tubing (ENT). Corrugated plastic flexible raceway.

• Nonmetallic underground conduit (PVC). Schedule 40 (heavy wall) or schedule 20 [called EB, for "encased burial" (in concrete)].

• Flexible metallic tubing, Greenfield, spiral metal flexible conduit.

• Liquidtite flexible metallic conduit, Sealtite, flexible metal conduit with an overall PVC waterproofing covering.

• Surface metal and nonmetallic raceways, Wiremold.

• Multioutlet assembly, Plugmold.

• Cellular metal floor raceways, underfloor duct, Q-deck, Walker duct.

• Cellular concrete floor raceways, Flexicore, Trenchduct.

• Wireways.

• Busways, bus duct.

• Cablebus.

• Boxes.

• Auxiliary gutters.

• Condulets and similar fittings.

The most common types of metallic raceways are electrometallic tubing (EMT) and rigid galvanized steel or rigid aluminum conduit. Rigid galvanized steel is available in both a standard wall thickness and a lighter-weight...