Misidentifying electrical cables can lead to safety hazards, code violations, and costly rework in industrial machinery applications. Even experienced professionals sometimes struggle to distinguish armored cable from other types, risking improper installation or maintenance.
Fortunately, by using a systematic approach involving visual inspection, cable feel, examining exposed ends, and decoding manufacturer markings, technicians can reliably identify armored cable and ensure the right product is used for the job.
Visual inspection
The outer jacket of the cable is made of a flexible metal armor, typically aluminum or galvanized steel, which provides both physical protection and grounding for the inner conductors. The metal armor consists of interlocking strips that form a continuous, flexible sheath around the insulated conductors.
When visually inspecting a cable, look for the presence of this metallic outer layer. The armor should have a smooth, uniform appearance without any significant gaps, dents, or kinks.
Feel and rigidity
Another key characteristic of armored cable is its rigidity compared to non-armored cables, such as NM (non-metallic) or Romex. The metal armor provides a level of stiffness that makes the cable less flexible and more resistant to bending.
When handling a suspected piece of armored cable, pay attention to how it feels in your hands. The cable should have a solid, sturdy feel, and it should not be easily bent or kinked.
Check the ends
At a cut end of armored cable, you should see the interlocking metal strips of the armor layer surrounding the inner insulated conductors. The armor may slightly overlap the insulation, creating a protective “collar” around the conductors. If you don’t see this characteristic layering of armor and insulation, the cable may not be a true armored cable.
Interpreting Manufacturer Markings
In addition to the physical characteristics of armored cable, the cable jacket also typically includes printed markings that provide important information about the cable’s specifications and intended use. These markings can help confirm that the cable is indeed an armored type and provide details about its construction and ratings.
Look for markings that include “AC,” “MC,” “AFC,” or similar codes, which indicate that the cable is an armored type. The markings may also include information about the cable’s conductor size (in AWG or kcmil), voltage rating, insulation type, and any specific applications or approvals (such as “sunlight resistant” or “direct burial”).
Some common armored cable markings include:
- AC-HCF: Indicates an armored cable with a continuously corrugated aluminum armor and THHN conductors
- MC-HL: Indicates a metal-clad cable with a continuous corrugated aluminum armor and XHHW conductors
- AC-MCMK: Armored cable with a stranded copper conductor and mineral-insulated (MI) construction