Commercial Wiring Methods

Several wiring methods are available for commercial installation. Some methods play a role in specific conditions, while some have a broader application. Commercial wiring methods fall into three categories: multiconductor cable, raceways and cable trays. Electricians must follow general guidelines common to the majority of wiring methods to avoid problems of inductance.

Commercial Wiring

• Commercial wiring is classified as high risk compared with residential wiring, owing to the added specifications. For example, commercial wiring involves the regulation and maintenance of high and low voltages required by commercial properties. Thus, electricians must have full awareness of the necessary codes for commercial wiring as established by the National Electric Code.

Multiconductor Cables

• Consisting of flexible conductors covered in a protective outer layer, the four types of multiconductor cables commonly used are service-entrance, armored, nonmetallic-sheath and metal-clad cable. Service entrance cables are mainly used for indoor and underground wiring, or at the service entrance. Nonmetallic-sheath cables are common in small commercial buildings or residences. Armored cables have restricted use but can work in both dry and wet locations, while heavy duty metal-clad cable has a wider range of application.

Raceways

• A raceway is either a metallic or nonmetal channel developed specifically to store wires and cables. Although more costly, raceways provide increased protection compared with the cable method. The types of raceways available include rigid, intermediate, flexible and liquid-tight flexible metal conduits, electrical metallic and nonmetallic tubing, and the rigid polyvinyl chloride conduit. In addition, electricians use surface raceways in adding circuits to inaccessible areas.

Cable Trays

• Cable trays operate similarly to raceways but are not enclosed. Most are open at the top and ventilated at the bottom. Often used as support systems for other wiring methods such as multiconductor cables, cable trays are predominantly applied to industrial settings. The two most common types are ladder and trough trays.