BX Wire
BX wiring (also known as armored cable) is the 2nd generation of wiring used in homes. It first appeared in the 1903 National Electrical Code (NEC) book. It became popular in the 1920s, and it was the main wiring type by 1932. Electrical cable encased in metal sheathing is often used in basements and other areas where the wire is not encased in a finished wall. It is handled differently than standard Romex® (non-metallic sheathed) cable. It is often used in fire-rated occupancies as an alternative to metallic conduit. BX cable is grounded via its metal armor or internal green plastic-coated ground wire. Because vinyl is not conductive, grounding is achieved by a separate bare copper ground wire in the bundle. BX is cut with a hacksaw.
Armored cable (AC) first appears in the 1903 NEC. There were originally two initial versions of armored cable. One was called “AX” and the other “BX,” with the “X” standing for “experimental.” The “BX” version became the one that eventually was produced, and hence the name “BX” became the common name.
