Chapter 5 Wiring Methods 67 Copyright Goodheart-Willcox Co., Inc. main service disconnect. When it is used for interior wiring, the grounded neutral con- ductor must be insulated, with the following exceptions: • When used as a feeder between two buildings. • When used as the circuit conductor or branch wiring to clothes dryers, counter- mounted cooktops, ranges, and ovens. Service-entrance cable may not be used for interior wiring of buildings of any type exceed- ing three stories high. Armored Cable (AC) Armored cable (AC), often called “BX” cable, is used in both dry and wet locations, but is not permitted to be buried. Armored cable has limited commercial use. It may not be used in places of assembly, studios, movie theaters, haz- ardous locations, commercial garages, areas with vapors and corrosive agents, lifts, cranes, hoists, elevators, or battery rooms. Armored cable can be used in the following situations: • As fl exible connections to motors or vibrating equipment (up to 24″ length). • As fi xture whips (up to 6′ length). • In dry locations. • Concealed behind walls (may be fi shed behind walls in old work). • Exposed along wall surfaces. • Where exposed to weather or moisture (type ACL only). Armored cable must be properly supported at intervals of 4′-6″ and within 12″ of terminal boxes or fi ttings. When routing BX cable through wall, fl oor, or ceiling members, the member must be drilled through the center or notched and covered with a metal plate to protect the cable from nails. The cable can be run along the sides of studs, joists, or rafters without further protection. Guard strips that are made of 1 × 1 or 1 × 2 stock are used to protect BX or AC cable when it is run along attic fl oor joists. Nonmetallic-Sheathed Cable (Types NM, NMC, and UF) Nonmetallic-sheathed cable is made up of two to four insulated conductors plus a green insulated or bare grounding conductor with an overall nonmetallic sheath. Often referred to as Romex, it is frequently used as the preferred CAUTION Antishort insulating bushing must be placed between conductors and the outer armor wher- ever the cable is cut. The bushings protect the conductor insulation from any sharp edges on the cut armor. A Protective outer jacket Insulated neutral conductor Insulation Type SE Conductor B Protective outer jacket Reinforcement tape Concentric neutral Insulation Conductors Type USE Reinforcement tape Bare equipment ground Goodheart-Willcox Publisher Figure 5-6. Service-entrance cable can be used for general indoor wiring as well as at the service entrance. A—Type SE cable. B—Type USE cable is used for underground applications.