What Is Armor-Clad (BX) Cable?

What Is Armor-Clad (BX) Cable?

Armor-clad cable, commonly called BX cable, is a type of electrical cable where the conductors are enclosed in a flexible metal armour rather than a plastic sheath. The armour is formed from interlocked steel or aluminum strips that spiral around the conductors, providing mechanical protection against physical damage. In Canada, armoured cable is designated AC (Armoured Cable) or ACWU (Armoured Cable, Water and Underground resistant). In the US, similar cable is called BX or MC (Metal-Clad) cable — the terms are often used interchangeably in Canada even though the exact products differ.

Where BX/AC Cable Is Used

• Exposed locations where NMD-90 cable could be damaged — unfinished basements, garages, mechanical rooms, and commercial applications
• Where the Ontario Electrical Code or local authority requires a wiring method more robust than NMD — some municipalities and commercial occupancies mandate armoured cable throughout
• Short runs from a panel to the first outlet or device in a finished wall, where the cable is exposed before entering the wall
• Retrofits in existing walls where conduit installation is impractical and mechanical protection is required

Differences from NMD-90

The metal armour of BX/AC cable acts as the grounding conductor in some versions — in older installations, this was the only ground path. Modern AC cable (ACWU) includes a separate green insulated grounding conductor. The armour requires a metal anti-short bushing (also called a red fibre bushing or anti-short) to be installed at every cut end before entering a connector, to prevent the sharp metal edges from cutting the conductor insulation. EZSMART uses armoured cable where code requires it and ensures correct termination and grounding on every installation. Contact us for commercial or residential wiring across Ontario.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp