Armored cable is electrical wiring wrapped in a protective metal sheath that shields the conductors inside from physical damage, moisture, and electromagnetic interference. It’s a self-contained wiring solution: instead of pulling individual wires through rigid metal conduit on a job site, armored cable arrives pre-assembled with its conductors already enclosed in flexible metallic armor, ready to route through walls, ceilings, and exposed runs.
How Armored Cable Is Built
From the inside out, armored cable has five distinct layers. At the center are the conductors themselves, typically copper or aluminum. Surrounding each conductor is an insulation layer made from materials like PVC or cross-linked polyethylene, which prevents short circuits and shields against electromagnetic interference. Between the insulation and the armor sits an inner sheath, often PVC or polyethylene, that holds multi-core conductors in position and protects the insulation from the metal armor pressing against it.
The armor layer is what defines the cable. It can take several forms depending on the application. Steel wire armor provides tensile strength and impact resistance, making it common in low-voltage installations. Steel tape armor resists lateral crushing pressure and is used in medium-voltage cables. Aluminum wire armor works well for single-core cables because it avoids the magnetic interference issues that steel creates. Finally, an outer jacket (usually PVC) protects the armor itself from corrosion, sunlight, and moisture.
Type AC vs. Type MC Cable
In the United States, the two most common categories of armored cable are Type AC and Type MC. They look similar but differ in grounding design and code requirements.
Type AC cable always contains a 16 AWG aluminum bonding wire running underneath the armor, and each insulated conductor is individually wrapped in kraft paper. The armor and bonding wire together serve as the equipment grounding path, which is why AC cable doesn’t need a separate full-size ground wire. Every termination point requires an insulating bushing, a small plastic fitting inserted between the cut armor edge and the conductors to prevent the sharp metal from slicing into the wire insulation.
Type MC (metal-clad) cable may or may not include a ground wire, and its conductors don’t require individual paper wrapping. Instead of a bonding wire, unjacketed MC cable has a printed marker tape under the armor identifying it as MC. The fittings used with MC cable are designed with smooth, rounded end stops so the metal sheath can’t slide through and damage the wires, but they don’t require a separate anti-short bushing the way AC fittings do. MC cable is governed by NEC Article 330, while AC cable falls under Article 320. On the safety testing side, Type AC must meet the UL 4 standard, while Type MC is tested under UL 1569.
Armor Styles for Different Environments
The type of armor determines where a cable can be installed. Interlocking armor, made from aluminum strip spirally wrapped around the cable core, is the most common style for indoor use. It provides good crush resistance while remaining flexible enough to route through tight spaces. Corrugated steel tape armor, a coated steel sheet folded lengthwise around the cable, is built for outdoor and direct-burial applications. It offers stronger mechanical protection and better resistance to rodent damage.
Standard AC cable is rated only for dry indoor locations. For wet environments, direct burial, or embedding in concrete, you need versions with a PVC outer jacket rated for moisture exposure. PVC-jacketed armored cables carry sunlight-resistant and flame-retardant ratings, making them suitable for both exposed outdoor runs and concealed installations.
Cost and Installation Tradeoffs
Armored cable and conduit wiring (like electrical metallic tubing, or EMT) represent two philosophies. Armored cable costs more in materials but saves significantly on labor during initial installation because the conductors are already assembled inside the armor. In one industry cost comparison of a combined feeder and office space project, MC cable materials ran about $25,400 compared to $13,350 for EMT. But the labor picture flipped: MC cable required roughly $11,300 in labor versus $27,450 for EMT, since conduit systems demand threading, forming, and pulling wire on site. The total initial costs were close, with MC cable coming in slightly cheaper overall.
Where conduit systems gain an advantage is in renovations. When building use changes and wiring needs to be replaced or upgraded, conduit acts as a reusable raceway. Electricians can pull old wires out and feed new ones in without tearing open walls. With armored cable, the entire cable has to be removed and replaced, which in one retrofit scenario required over 230 hours of demolition and rewiring labor compared to fewer than 100 hours for the same scope using existing conduit.
Canadian Armored Cable Types
In Canada, armored cable comes in three main varieties governed by the Canadian Electrical Code. AC90 is the basic indoor type, equivalent in concept to US Type AC, using interlocked aluminum armor that eliminates the need for conduit and all the labor-intensive threading and pulling that goes with it. It can bend to an inside radius as small as six times the cable diameter, making it practical for tight routing.
ACWU90 and TECK90 add wet-location and outdoor ratings. TECK90, in particular, is a heavy-duty cable with decades of proven use in mines, pulp and paper mills, petrochemical plants, and metal processing facilities. Both ACWU90 and TECK90 are certified for direct burial and for use in all classes and divisions of hazardous locations, areas where flammable gases, dust, or fibers may be present. AC90, by contrast, is restricted to above-ground services in dry locations.
Grounding Through the Armor
One of armored cable’s practical advantages is that the metal sheath itself can serve as part of the grounding system. In Type AC cable, the combination of the interlocking armor and the internal aluminum bonding wire creates a continuous conductive path back to the electrical panel. If a hot wire faults to the armor, current flows through this path and trips the breaker.
At every point where armored cable enters a building or connects to equipment, the non-current-carrying metallic components need to be bonded and connected to an approved ground. This typically involves a bond clamp secured to the armor, with a bond wire running from the clamp to the grounding system. Double-armored cables, used in applications requiring extra protection, need both armor layers bonded and grounded independently.