Why do they call it bx cable

Overview

BX cable, officially known as armored cable, gets its name from its original trade designation when it was first introduced in 1902 by the National Electric Company. The 'B' stands for 'bendable' or 'flexible,' referring to the cable's ability to be routed through building structures, while the 'X' was simply a suffix added to distinguish it from other cable types in their product line. This innovation came at a critical time in electrical history when buildings were transitioning from gas lighting to electrical systems, and existing wiring methods like knob-and-tube were proving inadequate for growing electrical demands. The development of BX cable coincided with the rapid expansion of urban electrification in the early 20th century, with cities like New York and Chicago seeing massive installation projects between 1905-1915. By 1910, BX cable had become the standard wiring method for commercial buildings and was making significant inroads into residential construction, particularly in multi-story buildings where fire safety was a major concern.

How It Works

BX cable consists of insulated electrical conductors wrapped in a flexible, interlocking metal armor that provides both mechanical protection and a grounding path. The original design featured two or more copper conductors insulated with rubber and wrapped in a spiral-wound steel armor. When installed, electricians would cut the cable to length, then use special connectors called 'anti-short bushings' to prevent the sharp edges of the cut armor from damaging the wire insulation. The flexible armor allows the cable to be bent around corners and through studs without requiring conduit, making installation significantly faster than rigid conduit systems. The metal armor serves multiple functions: it protects against physical damage from nails or screws, contains any potential electrical fires within the cable, and provides a continuous grounding path when properly connected to metal boxes and fittings. Modern versions use aluminum armor in some applications and have evolved to include additional safety features like bonding wires that ensure better grounding continuity.

Why It Matters

BX cable's development marked a turning point in electrical safety, reducing fire hazards in buildings by containing potential electrical faults within the metal armor. This was particularly important in the early 20th century when electrical fires were common due to inadequate wiring systems. The cable's flexibility and ease of installation helped accelerate the electrification of American cities, making electrical power more accessible and affordable. Even today, while modern codes often require updated versions like Type AC or MC cable, the principles established by BX cable continue to influence electrical safety standards. In renovation projects, electricians frequently encounter original BX installations that remain functional after decades of service, demonstrating the durability of this design. The persistence of the term 'BX' in electrical trade language, even for modern armored cables, underscores its lasting impact on the industry.