Galvanized cable trays may require bridging

Yes, galvanized cable trays generally require bridging or bonding to ensure electrical continuity and mechanical stability, especially when used as part of an equipment grounding system.

Electrical Continuity and Grounding

Galvanized cable trays, like other metallic trays, are often used as part of the equipment grounding conductor (EGC) system. To maintain proper grounding, each section of the tray should be electrically continuous. This is typically achieved through bonding clamps or bridging connections between tray sections.

While the NE

C does not always mandate bonding every section, it is considered a desirable practice to prevent disconnection of the EGC under fault conditions and to mechanically secure the grounding conductor. For installations where the tray itself serves as the EGC, the minimum cross-sectional area of the tray side rails must meet the requirements for the specific circuit protection rating. Bridging ensures that the tray sections remain electrically connected and capable of safely carrying fault currents.

Mechanical Support and Structural Bridging

In addition to electrical bonding, bridging can also provide mechanical reinforcement. Galvanized trays are often used in industrial and commercial applications where heavy cables or long spans are present. Installing bridges or splice plates at appropriate intervals helps maintain structural integrity, reduces deflection, and prevents sagging of the tray under load.

The recommended practice is to place supports at quarter-span points and use bridging or splice plates to connect tray sections, particularly at joints or where the tray changes direction. This ensures both mechanical stability and proper alignment for cable installation.

Summary

Electrical bridging: Recommended to maintain grounding continuity and secure the EGC, using bonding clamps or splice plates. Mechanical bridging: Helps prevent sagging and maintains structural integrity, especially for long spans or heavy cable loads. Compliance: Follow NEC, IEC, and manufacturer guidelines for support spacing, bonding, and bridging to ensure safety and reliability.

In conclusion, while not every installation may strictly require bridging, best practices for galvanized cable trays include both electrical and mechanical bridging to ensure safety, grounding continuity, and structural performance.