Raceways and Conductors

Raceways are the conduits, or similar housing, whose dual function is to facilitate the installation (or removal) of electrical conductors and to provide protection from mechanical damage. Article 100 defines raceway as an enclosed channel of metallic (or nonmetallic) materials designed expressly for holding wires, cables, or busbars, with additional functions as permitted in the National Electrical Code. The term raceway applies to more than just tubular conduit.

This unit contains regulations for raceway systems that are frequently used (such as electrical metallic tubing and wireways), as well as raceway systems that are rarely used (such as cellular concrete floor raceways). In addition to defining different raceways, other important information is covered, such as minimum and maximum size, installation provisions, fittings, and support requirements. Instructions are presented on how to perform raceway fill calculations, a prerequisite in determining the size of raceway needed for particular circuits. A brief explanation of conductors, including ampacity correction factors and conductor temperature limitations, can be found near the conclusion of this unit. Understanding this unit will make finding the best raceway system for a particular project much easier.

Most raceway articles have sections entitled “Uses Permitted” and “Uses Not Permitted” (NEC^® Chapter 3). These sections give locations (some specific) where the raceway system can (or cannot) be installed. Because most of these provisions are clearly understandable, this book does not repeat much of this information. Although not addressed in this unit, another important area is underground raceway installation (300.5). Underground installations are covered in Unit 4, which explains minimum cover requirements for underground cables and conductors. Use Table 300.5(A) (Minimum Cover Requirements) to find the minimum burial depth for different types of raceways installed in a variety of locations.