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On any commercial or residential job site, the choice between different wiring methods is constant. When it comes to armored cables, the AC vs. MC debate is one I’ve heard and participated in for years. To the untrained eye, they look nearly identical—a flexible, metallic armor protecting the conductors inside. But as any seasoned electrician knows, the differences under that armor are critical, impacting everything from grounding and safety to where the cable can be legally installed.
If you’ve ever wondered why a specific type of armored cable was spec’d for a job, or you’re trying to make the right call for your own project, this guide is for you. We’ll break down the core differences between Armored Cable (AC) and Metal-Clad (MC) electrical cable, look at their construction, and help you decide which is the right fit for your needs.
What does ac cable stand for？
Armored Cable, or Type AC, is the classic sheathed cable that has been in use for over a century. Many old-timers still refer to it by its original trade name, “BX” cable. Governed by NEC Article 320, AC cable is a factory assembly of insulated conductors housed within a flexible, interlocked metal armor, which is typically made of steel or aluminum.
What truly defines AC cable is its unique grounding system. Instead of a dedicated ground wire, it features:
- A thin, bare aluminum bonding strip that runs the entire length of the cable, in constant contact with the metal armor.
- The combination of this bonding strip and the metal armor itself serves as the equipment grounding conductor.
Inside the armor, the conductors are traditionally wrapped in a moisture-resistant paper to protect them from abrasion during installation. Because of this construction, standard Type AC cable is restricted to dry locations only and cannot be used outdoors or in wet environments.
What is Metal-Clad Cable (MC)?
Metal-Clad Cable, or Type MC, is the modern evolution of armored cable, governed by NEC Article 330. While it looks similar on the outside, its internal construction is fundamentally different and offers greater versatility.
The key feature of MC electrical cable is its full-sized equipment grounding conductor. This is typically a green-insulated or bare copper wire that provides a dedicated, reliable path to ground. Unlike AC cable, the metal armor of a standard MC cable is not intended to be part of the grounding path.
Other construction differences include:
- The conductors are wrapped in a polypropylene or Mylar tape instead of paper, which is common in modern manufacturing.
- MC cable is available in a much wider range of configurations and sizes, from small 18 AWG control wires to large 1000 kcmil feeder cables.
- Crucially, MC cable can be rated for various environments. With the addition of a PVC outer jacket, it is suitable for wet locations, direct burial, or encasement in concrete.
Also read more about MC cable: MC Cable Practical Insights:Types, Uses&Comparisons
What’s the difference between AC and MC cable?
Understanding the distinctions is key to selecting the right cable and ensuring a code-compliant installation. Here’s a direct comparison of their most important features:
| Feature | Type AC Cable (Armored Cable) | Type MC Cable (Metal-Clad Cable) |
| Grounding Method | The metal armor combined with an internal aluminum bonding strip acts as the ground path. | Contains a full-sized, dedicated equipment grounding conductor (insulated or bare). |
| Internal Wrap | Kraft paper wrap around conductors. | Mylar or polypropylene tape wrap. |
| Wet Locations | Strictly prohibited. For dry, indoor use only. | Permitted when manufactured with a PVC outer jacket and used with wet-location fittings. |
| NEC Support Spacing | Must be supported at least every 4.5 feet and within 12 inches of a box. | Must be supported at least every 6 feet and within 12 inches of a box. |
| Anti-Short Bushings | Required by NEC 320.40 to protect wires from the sharp edge of the cut armor. | Not required by the NEC for listed fittings, but many electricians (myself included) use them as a best practice. |
We can also learn more about how ac cable wiring can be safely prepared with the following video：
Making the Right Choice: Practical Scenarios and Cost
So, which cable should you use? The decision comes down to application, environment, and cost.
- For standard indoor, dry locations like residential or commercial branch circuits concealed in walls or ceilings, Type AC cable is a perfectly acceptable and often more economical choice. Its installation can be slightly faster since there isn’t a separate ground wire to terminate at every device.
- For industrial, commercial, or outdoor applications, Type MC cable is the clear winner in versatility. Its dedicated ground wire is often preferred for the reliability it provides in commercial settings. Furthermore, its availability in PVC-jacketed versions makes it the only choice for runs in wet or damp locations, or for direct burial.
From a cost perspective, the material price can fluctuate. Sometimes AC is slightly more expensive per foot, sometimes less. The real difference is in labor. While AC saves a minute at each termination by not having a ground screw to connect, MC’s wider range of applications and slightly more forgiving support requirements (6 feet vs. 4.5 feet) often make it the more efficient, go-to choice for contractors who want to stock a single, versatile armored cable.
AC VS MC Cable Conclusion
While both AC and MC cables provide excellent physical protection for conductors, they are not interchangeable. Type AC cable, the original “BX,” remains a solid choice for standard, dry-location branch circuits where its armor-based grounding is sufficient.
However, Type MC cable has become the modern industry workhorse for good reason. Its dedicated grounding conductor, robust construction, and unmatched versatility for use in wet and demanding environments make it the superior and more flexible option for the vast majority of new commercial and industrial projects.
With the above understanding of the different emphasis on armored cable vs metal clad cable in terms of structure and application, we are able to choose cables that are more compatible to specific projects according to our needs. In light of this, consulting with experienced professionals and sourcing from trusted manufacturers becomes paramount. Thus, For expert guidance and high-quality solutions, turning to a reputable top 10 china cable manufacturers like ZW Cable is advisable.
