EZSMART Corporation, ESA/ECRA #7012690 , North York , Ontario
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BX cable — conductors wrapped in a flexible metal spiral jacket instead of the plastic sheath on standard NMD90 — shows up in a lot of Toronto and GTA homes, both as older original wiring and as a modern cable type still used for specific applications today. Unlike knob-and-tube or cloth wiring, finding BX cable is not automatically a red flag. This guide covers what it actually is and when it matters.
BX cable (the trade name; the current Canadian designation is AC90, for Armored Cable rated 90°C) consists of insulated conductors wrapped in a flexible, spiral-wound metal sheath. The metal jacket provides mechanical protection the plastic sheath on NMD90 does not, which is why AC90 remains a code-recognized, actively used cable type today — not a deprecated legacy product like knob-and-tube. Whether existing BX wiring in an older home is a concern depends entirely on its age, condition, and how the metal jacket itself is functioning as the ground path, which is where older BX installations sometimes fall short of current standards.
It is genuinely different from NMD90 in application, not a worse or outdated version of it — see what is the difference between NM cable and armored cable for the fuller comparison.
The issue in a Toronto or GTA home is not the metal jacket itself — it is how grounding was handled on older installations. Modern AC90 cable includes a dedicated bonding conductor inside the jacket specifically for grounding. Older BX cable sometimes relied on the metal armor itself as the ground path, with continuity depending on tight, clean connections at every single connector and box along the run. Over decades, those connections can loosen or corrode, degrading the ground path’s reliability in a way that is not visible from outside — the same invisible-until-tested problem covered in what are the signs of a bad ground wire.
Not automatically. Sound BX cable with intact connections and a verified ground path is a legitimate, functioning wiring system, not a defect to be replaced on sight the way active knob-and-tube or crumbling cloth insulation is treated. The practical response is verification, not automatic replacement:
BX/AC90 cable does not carry the same blanket insurance concern that knob-and-tube or aluminum branch wiring does in Ontario, because it is still an actively used, code-current cable type rather than a discontinued legacy system. Insurers and home inspectors are generally more interested in the specific condition and grounding verification than the presence of BX cable itself.
The BX calls we get in the GTA usually come from a homeowner who read online that BX cable is dangerous and panicked, when the actual system in their home has been running fine for decades. The real question is never “do I have BX cable” — it is “does the ground path through this specific run test as continuous and low-resistance.” That is a fifteen-minute check with a meter, not a rewrite of the whole electrical system. Get the continuity verified before assuming the cable itself is the problem.
No. Knob and tube is discontinued open-air wiring from an earlier era. BX/AC90 is a metal-jacketed cable type still actively used in current construction.
Not automatically — verify the ground path integrity first. Sound BX with confirmed continuity is a legitimate wiring system.
Modern AC90 includes a dedicated bonding conductor. Older BX sometimes relies on the metal armor itself, which depends on tight connections throughout.
Yes, it remains a current, code-recognized product used for specific applications where mechanical protection matters.
Generally no, since it is an actively used current cable type rather than a discontinued legacy system.
Found BX cable in your Toronto or GTA home and want the ground path verified? Call ezsmart at 416-838-9006 or use our contact page. An ESA-licensed electrician will test it properly.
Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp
