Cable Trays and Grounding Requirements

Metallic cable trays must be properly grounded and bonded according to NEC standards, and may serve as equipment grounding conductors (EGCs) under specific conditions.

Grounding Metallic Cable Trays

All metallic cable trays must be grounded regardless of whether they are used as an EGC, as required by NEC Article 250.96 . Grounding ensures electrical continuity and safety, preventing shock hazards and equipment damage. Metallic trays can serve as the EGC if they meet the minimum metal cross-sectional area requirements specified in NEC Table 392.60(A) or Table 318-7(b)(2), depending on the protective device ratings for the circuits they carry . If the tray's metal area is insufficient, a separate EGC must be installed within each cable assembly or attached to the tray.

Bonding Practices

To maintain electrical continuity, all tray sections should be mechanically tight and electrically continuous. Bonding jumpers may be required where mechanical connections alone do not provide reliable continuity . Grounding clamps are recommended to bond EGCs to each or alternate tray sections, which also helps secure the conductor under fault conditions . For aluminum trays, bare copper EGCs should be avoided in moist environments to prevent electrolytic corrosion; insulated conductors with exposed ends at bonding points are preferred .

Use of Cable Trays as EGCs

Cable trays may serve as the equipment grounding conductor in qualifying facilities where only qualified personnel service the system . Wire mesh trays are generally not recommended as EGCs due to reduced current-carrying capability from field modifications, but if used, a separate ground wire is advised . Non-metallic trays cannot serve as EGCs and require separate grounding conductors.

NEC Compliance and Safety Considerations

• Tray fill limits must be observed to prevent overheating and maintain airflow: typically 40% for power cables and 50% for control cables .
• Separation of power and data cables is required to reduce electromagnetic interference (EMI), .
• Firestopping is necessary when trays penetrate fire-rated walls or floors to maintain building safety .
• All connections to conduits or cables must use UL-listed connectors to ensure proper electrical continuity .

Best Practices

• Ensure mechanical and electrical continuity across all tray sections.
• Use insulated EGCs in aluminum trays to prevent corrosion.
• Verify EGC sizing according to NEC tables for the highest-rated circuit in the tray.
• Maintain proper separation and tray fill to optimize safety and performance.
• Regularly inspect and maintain grounding connections to ensure ongoing compliance and safety. By following these grounding and bonding requirements, cable tray systems can provide a safe, reliable, and code-compliant solution for managing electrical conductors in industrial, commercial, and data center environments .