Requirements for Ground Cable Tray Installation

Metallic cable trays must be properly grounded and bonded according to NEC standards, using either the tray itself or an equipment grounding conductor (EGC) to ensure electrical safety and system reliability.

NEC Requirements for Grounding Cable Trays

The National Electrical Code (NEC) Article 392 governs cable tray systems, including grounding and bonding requirements. All metallic cable trays must be grounded regardless of whether they are used as an EGC. Grounding ensures that any fault current is safely conducted to the earth, reducing the risk of electric shock or fire (NEC Article 250.96) .

Using Cable Trays as Equipment Grounding Conductors

Metallic trays can serve as the equipment grounding conductor (EGC) in qualifying facilities where only qualified personnel service the system. The tray must be electrically continuous and properly bonded at joints to maintain a low-impedance path for fault currents (NEC Sections 318-3(c) and 250-51) . If an EGC cable is installed alongside the tray, it should be bonded to each or alternate tray sections using grounding clamps to prevent mechanical displacement during fault conditions .

Bonding and Conductor Considerations

• Bonding clamps are recommended to connect EGCs to the tray, ensuring both electrical continuity and mechanical stability .
• Bare copper conductors should not be used in aluminum trays due to the risk of electrolytic corrosion; insulated conductors with exposed ends at bonding points are preferred .
• The size of the EGC depends on the circuit rating and the number of paralleled cables, following NEC Table 250-95 .

Installation Best Practices

• Maintain proper tray fill limits: 40% for power cables and 50% for control cables to prevent overheating .
• Ensure separation of high-power and low-power cables to reduce electromagnetic interference (EMI) .
• Use mesh or ventilated trays to improve airflow, simplify grounding, and allow visual inspection .
• Maintain minimum clearances above trays (at least 12 inches) for safe installation and maintenance access .
• Apply firestop systems at penetrations to comply with safety codes .

Material and Environmental Considerations

• Choose tray materials (aluminum, steel, or FRP) based on environmental conditions, load requirements, and corrosion resistance .
• Stainless steel or pre-galvanized steel is recommended in corrosive environments to maintain grounding integrity . By following these NEC guidelines and best practices, electrical professionals can ensure that cable tray installations are safe, code-compliant, and reliable, providing a continuous grounding path and minimizing risks associated with electrical faults.