Cables in cable trays do not always need to be armored; they must be either tray-rated (Type TC) or metal-clad (Type MC) depending on the installation and exposure conditions.

NEC Requirements

According to NEC Article 392, cable trays are considered a support system, not a fully enclosed raceway. This distinction means that cables installed in trays are exposed to the open air, so they require a durable outer covering. The NEC specifies that cables in trays must be either Type TC (Tray Cable) or metal-armored (Type MC) to ensure mechanical protection and fire safety, but armor is not universally required for all installations . Cables with sufficient insulation and tray rating can be installed without additional armor, especially in indoor, low-risk environments. Covers for trays are optional but recommended in high-traffic areas or outdoor installations to protect against physical damage and environmental exposure .

Practical Considerations

• Cable Type: Power, control, communication, and optical fiber cables can be installed in trays. Type TC, PLTC, ITC, MC, and MI cables are commonly used .
• Separation: High-power and low-power cables should be separated to prevent electromagnetic interference (EMI) and maintain signal integrity .
• Environmental Exposure: In areas exposed to sunlight, moisture, or potential mechanical damage, armored cables or tray covers may be preferred for added protection .
• Grounding: Metallic trays can serve as equipment grounding conductors if installed according to NEC requirements .

IEC Perspective

Under IEC standards, armored cables may be required in certain hazardous locations, such as gas compressor areas, but this is location-specific and not a general mandate for all cable tray installations .

Summary

• Armor is not mandatory for all cables in trays.
• Tray-rated (Type TC) or metal-clad (Type MC) cables are typically sufficient.
• Additional protection (armor or tray covers) is recommended in high-risk or outdoor environments.
• Compliance with NEC Article 392 ensures safety, proper support, and fire protection. By selecting the appropriate cable type and following NEC or IEC guidelines, cable tray installations can be both safe and cost-effective without requiring armor in every case.