Metallic cable trays can serve as equipment grounding conductors (EGCs) when installed according to NEC requirements and proper bonding practices.

Use as Equipment Grounding Conductor (EGC)

Metal cable trays are permitted to function as EGCs in qualifying facilities where qualified personnel maintain and service the system. The tray itself provides a low-impedance path for fault currents, ensuring that over-current protective devices operate correctly under ground fault conditions (NEC Section 318-3(c)), . This allows the tray to act as a grounding trunk line, eliminating the need for separate grounding conductors in some installations.

Material and Construction Considerations

• Steel trays: Suitable for circuits with ground-fault protection up to 600 amperes.
• Aluminum trays: Suitable for circuits with ground-fault protection up to 2000 amperes.
• Cross-sectional area: The total metal area of the tray side rails (or combined with the bottom for one-piece trays) must meet minimum requirements based on the fault current rating to safely carry fault currents .
• Corrosion prevention: Avoid bare copper conductors in aluminum trays to prevent electrolytic corrosion; use insulated conductors with exposed bonding points and tin- or zinc-plated connectors .

Installation and Bonding Practices

• Grounding clamps: Bond each or alternate tray sections to the EGC to maintain electrical continuity and mechanically secure the conductor under fault conditions .
• Parallel EGCs: Designers may run a single conductor or multiple EGCs in parallel with the tray to enhance reliability .
• Continuous grounding: All metallic trays must be grounded per NEC Article 250.96, even if not used as an EGC, to prevent shock hazards and ensure safety .
• UL Classification: Metal trays are UL-classified for suitability as EGCs, and manufacturers provide cross-sectional data for compliance .

Practical Considerations

• Qualified personnel: Only facilities with trained electrical staff should rely on the tray as the primary EGC.
• Environmental factors: Choose tray material (steel, aluminum, or stainless steel) based on moisture, chemical exposure, and mechanical load requirements .
• Maintenance access: Ensure trays remain accessible for inspection and bonding verification.
• Circuit separation: Maintain separation between high-power and low-power circuits to reduce electromagnetic interference (EMI) and maintain safety . Using metal cable trays as grounding trunk lines can simplify installations, reduce conductor clutter, and provide a reliable grounding path when properly designed, bonded, and maintained according to NEC and industry standards .