Included in this category are metallic and nonmetallic, rigid and flexible conduit, manufactured wiring systems, reels, festoons, powertracks, and all types of ducts, trays, wireways, and boxes.
Wire management can be accomplished using any one of a wide variety of raceways and systems. Depending on the location, applications, and environment, a variety of choices is available, each specifically designed for ease of installation by the installer and increased flexibility for the end user. These raceways and systems are available in metallic and nonmetallic configurations, depending on the installed environment and/or designer/end-user preference.
Rigid metallic conduit and fittings are available in nominal sizes up to 6 in. The most. common metals used are steel and aluminum, and these can be PVC-coated to protect in wet and corrosive locations. Fittings include "T", "L", and pull fittings; seals; drains; boxes; expansion and alignment joints; couplings; and other items that together form a complete raceway system when installed. Factory-installed couplings allow quick assembly on the jobsite.
Intermediate metal conduit (IMC) is a lighter-weight rigid conduit that comes in sizes from 1/2 to 4 in. and uses threaded fittings. For a given trade size, IMC has a larger inside diameter than standard galvanized rigid steel conduit, which makes for easier cable pulling, while its lighter weight makes handling easier. IMC may be used wherever rigid metal conduit is used, including encasement in concrete and direct-burial applications.
Rigid nonmetallic conduit is available in fiberglass, polyethylene, and PVC. Such raceways can resist corrosion, electrolysis, impact, and temperature extremes.
They are lighter in weight than rigid metallic conduit and come in longer section lengths. This eases handling and reduces the number of required joints. Some types can be used for above-ground installations for circuits rated over 600V, or directly buried without concrete encasement.
Electrical metallic tubing (EMT), or "thinwall", is typically used in smaller sizes for branch circuits, and in larger sizes for feeders in indoor applications. Setscrew fittings are most economical; however, compression-type fittings are also available.
Where flexibility is required to accommodate vibration or movement, or to ease routing problems as a result of obstructions, flexible metallic conduit formed by a variety of interlocking methods is available. Steel or aluminum are the materials usually used for this type of raceway, although various others are available. Flex can be obtained with PVC or other jackets and can be classified as liquidtight. Nonmetallic flexible conduit is also available.
Wireways and surface metal raceways
Wireways, in both metallic and nonmetallic constructions, have square- or rectangular- shaped cross sections. They provide access to conductors enclosed within them at all points, and offer ease of conductor installation, splicing, rerouting, and tapping. Raintight constructions are available for outdoor or wet environments. The nonmetallic construction, now recognized in the 1993 NEC, is ideal for applications in corrosive atmospheres.
Surface metal raceways and multi-outlet assemblies, both metallic and nonmetallic, offer the same advantages as wire-ways but are smaller and less rugged. Installation of such raceways is limited to dry locations and locations where they will not be subject to physical damage. Where lighting, power, and telecommunications circuits are enclosed in the same raceway, this raceway must be barriered.
Cable trays are actually cable-support systems, not raceways, and are cost effective in terms of speed of installation of wire and cable. Metal trays are usually made of steel or aluminum, but stainless steel is also available for special applications. Nonmetallic trays are made of fiberglass and are available in widths from 4 to 36 in. Varied types of fittings, in both metallic and nonmetallic constructions, permit flexibility in system design and layout.