How to install bare wires in cable trays

Bare wires should generally not be placed in cable trays, especially aluminum trays, due to safety and corrosion concerns; insulated conductors rated for tray use are required.

Key Guidelines

Cable Tray Requirements: Cable trays are designed to support and organize electrical conductors in open-air environments. Only conductors rated for tray use, such as Tray Rated (Type TC) or Metal-Clad (Type MC) cables, are permitted in most installations . These cables have insulation suitable for exposure to air and mechanical protection. Bare Conductors: Bare copper or aluminum conductors are generally not allowed in cable trays as primary conductors because they lack insulation and can pose a shock hazard or cause short circuits. In industrial setups, single insulated conductors 1/0 AWG or larger may be used, but bare conductors are typically limited to equipment grounding conductors (EGC) . Material Compatibility: A bare copper EGC should not be placed in an aluminum tray due to the risk of electrolytic corrosion in moist environments. If grounding is required, it is recommended to use insulated conductors and remove insulation only at bonding points using tin- or zinc-plated connectors . Grounding and Bonding: Metallic trays can serve as the EGC if they meet NEC requirements, but all sections must be properly bonded. Grounding clamps are used to mechanically secure EGCs to the tray, ensuring continuity and preventing displacement under fault conditions . Exceptions: Bare conductors may be used in specific industrial applications as part of the grounding system, but they must comply with NEC Table 392.60(A) and other bonding requirements. For circuits with high ground-fault protection, steel or aluminum trays may have limitations on serving as the EGC .

Summary

• Do not place bare power conductors in cable trays.
• Use insulated, tray-rated cables for all conductors exposed in trays.
• Bare conductors are only acceptable for grounding, and even then, insulation is preferred in aluminum trays.
• Follow NEC Article 392 and local codes for spacing, bonding, and material compatibility to ensure safety and compliance . Proper adherence to these rules prevents electrical hazards, corrosion, and interference while maintaining a safe and code-compliant cable tray system.