What is bx cable

Overview

BX cable, commonly referred to as armored cable, is a type of insulated electrical wiring system designed for both residential and commercial applications. The cable features insulated conductors protected by a flexible metal sheath, which provides exceptional protection against physical damage. The construction allows the cable to be both flexible enough for installation in various configurations and sturdy enough to withstand harsh environmental conditions. BX cable has remained a staple in electrical installations for over a century.

Cable Construction

BX cable construction involves several key components working together to provide safe electrical transmission. The core consists of multiple insulated copper conductors, typically ranging from two to four wires depending on application. Each conductor is individually plastic-coated for insulation. These conductors are then bundled together and wrapped by a flexible metal armor made from galvanized steel or aluminum. The metal strip is applied in a tightly interlocked helical pattern, creating a durable yet flexible sheath that gives the cable its distinctive appearance. Modern versions include an internal bonding strip that ensures proper grounding continuity throughout the cable's length.

Grounding and Electrical Properties

One of BX cable's key advantages is its integrated grounding system. The metal armor itself serves as the equipment grounding conductor, eliminating the need for a separate ground wire. In modern Type AC cable, the internal bonding strip maintains intimate contact with the armor along the entire cable length, ensuring a low-impedance path for fault current. This design is essential for safety, allowing circuit breakers to detect faults and interrupt power quickly. The metal sheathing also provides electromagnetic shielding, protecting the conductors and reducing electromagnetic interference.

Advantages Over Other Cable Types

BX cable offers several advantages compared to non-metallic cables. The metal armor provides superior protection against mechanical damage from nails, screws, and drilling. The cable is also highly resistant to damage from rodents and pests that might chew through plastic insulation. The metal sheathing provides shielding against electric fields and reduces electromagnetic emissions. Additionally, BX's structural strength makes it suitable for exposed installations where the wiring is visible and subject to potential impact.

Installation and Applications

BX cable is approved for use in both exposed and concealed installations in buildings. It is particularly well-suited for basements, garages, utility rooms, and industrial environments where mechanical damage risk is elevated. The cable's flexibility allows it to bend around obstacles, though installers must follow code requirements regarding bending radius. BX is commonly used for branch circuits, subfeed wiring, and equipment connections. Installation requires proper securing at intervals specified by code and appropriate termination with approved connectors and fittings designed for the cable type.