A Comprehensive Guide Based on NEC and Industry Standards

Armored cable (often referred to as Type AC cable) is widely used for its robust mechanical protection and ease of installation in many wiring applications. However, its design does not make it a universal solution. Understanding its limitations—and where it is not permitted—is crucial for compliance with the National Electrical Code (NEC) and ensuring overall installation safety.

Overview of Armored Cable

Armored cable consists of insulated conductors wrapped in a flexible metal sheath (commonly steel or aluminum) with an internal bonding strip that can serve as an equipment grounding path. This construction provides excellent protection against physical damage and certain environmental hazards. Despite these benefits, the NEC and various industry standards impose restrictions on its use in specific applications.

Key Restrictions and Prohibited Applications

1. Areas Subject to Physical Damage

Not Permitted:

• Exposed Installations: Armored cable should not be used in locations where it is likely to be subjected to direct physical impact or abrasion unless additional protection (such as conduit) is provided.
• High Traffic Areas: For example, in open corridors or on building exteriors where accidental damage may occur, using armored cable without extra protection is generally prohibited.
  

2. Damp or Wet Locations

Not Permitted:

• Moisture-Prone Areas: Standard armored cable is not allowed in damp or wet environments (e.g., outdoor wet areas or directly exposed to rain) because the metal sheath can corrode, and the insulation may degrade over time.
  
  

3. Voids in Block or Tile Walls

Not Permitted:

• Exposed Voids: When installed within the air spaces (voids) of masonry block or tile walls that are exposed to excessive moisture, armored cable is disallowed. Moisture can infiltrate these spaces and compromise the cable's integrity.
  
  

4. Corrosive Environments

Not Permitted:

• Chemical Exposure: In environments where cables are exposed to corrosive substances (such as chlorides, caustic chemicals, or acidic vapors), standard armored cable is not acceptable unless it is specifically listed for corrosive conditions. In such cases, a cable with a corrosion-resistant armor or additional protective jacket must be used.
  
  

5. Plenum Spaces (Unless Listed for Use)

Conditional:

• Plenum Installations: Armored cable may be used in plenum spaces (areas used for environmental air) only if it is specifically listed and rated for that application. Standard armored cable without the appropriate plenum rating is not permitted in these spaces because of concerns over smoke production and fire spread.
  
  

Comparison Table: Permitted vs. Prohibited Uses of Armored Cable

Illustrative Image

Below is an example illustration of armored cable installation in a typical indoor setting. Note how proper protection measures (such as conduit or securing fasteners) are employed to minimize the risk of physical damage.

Related Video

For further details on the proper and improper applications of wiring methods in plenum spaces and other environments, check out this informative video by Mike Holt on plenum space wiring methods:

Conclusion

While armored cable offers robust protection and versatility for many electrical installations, it is not a one-size-fits-all solution. When planning an installation, it is essential to consider the environment—particularly moisture, exposure to physical damage, corrosive conditions, and plenum space requirements. Always consult the latest NEC guidelines and local codes, and use cables that are specifically listed for the intended application. This ensures not only code compliance but also long-term safety and performance.