Cable trays are not grounded or connected via bridging connections

Metallic cable trays must be grounded and electrically continuous; failure to do so can create shock hazards, equipment damage, and code violations.

Importance of Grounding and Bonding

Metallic cable trays, including steel, aluminum, and stainless steel, are required to be grounded and bonded to ensure safety and compliance with electrical codes such as NEC Article 392. Grounding provides a low-resistance path for fault currents, protecting personnel from electric shock and preventing arcing or equipment damage. Even if the tray is not used as an Equipment Grounding Conductor (EGC), all metallic trays must be grounded to the building's protective conductor system.

Bridging Connections and Electrical Continuity

Bridging connections, or bonding jumpers, are used to maintain electrical continuity between tray sections. Without proper bridging or bonding: Fault currents may not flow effectively, increasing the risk of electrical shock or equipment failure. Mechanical connections alone may not provide reliable conductivity, especially in galvanized, stainless steel, or aluminum trays.

Inspection failures can occur, as grounding continuity is a key compliance requirement. Best practices include using copper or tinned copper bonding conductors with a cross-sectional area of at least 4 mm², crimped connectors, and securing connections with lock nuts or anti-loosening washers to ensure both mechanical and electrical reliability.

Inspection and Compliance

Grounding inspections should be performed before cable installation and energization to verify that all tray sections are electrically continuous and properly bonded. For long runs, multiple grounding points are required: Trays ≤30 m: at least 2 reliable connections to the protective conductor at both ends. Trays >30 m: additional connection points every 20–30 m to maintain equipotential bonding.

If bridging conductors are not used, each connecting plate must have at least two bolts with lock nuts or washers to ensure reliable contact and minimize contact resistance.

Consequences of Non-

Grounded or Non-Bridged TraysFailure to ground or bridge cable trays can result in: Shock hazards to personnel. Equipment damage due to uncontrolled fault currents. Non-compliance with NEC or international standards, potentially leading to failed inspections.

Increased risk of arcing and fire in fault conditions.

Summary

To ensure safety and compliance: Always ground metallic cable trays to the building's protective conductor system. Use bonding jumpers or bridging conductors to maintain electrical continuity between tray sections. Inspect grounding before cable installation and energization.

Follow NE

C Article 392 and international standards (GB 50303-2015, GB 51348-2019, CECS 31-2023) for connection spacing, conductor sizing, and mechanical fastening. Proper grounding and bridging are essential for safe, reliable, and code-compliant cable tray installations.