How to measure the height of cable tray access

The height of a cable tray, also referred to as the tray's sidewall depth, is measured from the bottom of the tray to the top edge of the sidewall to ensure safe cable containment and proper airflow.

Understanding Cable Tray Height

The height or depth of a cable tray is critical for maintaining cable safety, heat dissipation, and future expansion. It ensures that cables remain securely held without overcrowding, allowing air to circulate and preventing overheating. Standard cable tray heights typically range from 25 mm to 150 mm, depending on the type of tray and the number of cables to be installed.

Steps to Measure Cable Tray Height

Identify the Tray Type: Ladder, perforated, channel, or wire mesh trays may have different sidewall heights and structural requirements. Measure from Bottom to Top Edge: Use a tape measure or ruler to measure the vertical distance from the bottom of the tray (where cables rest) to the top of the sidewall. This is the usable height for cable installation.

Consider Cable Fill and Airflow: Only a portion of the tray should be filled to allow for ventilation. For power cables, a 40% fill ratio is recommended, leaving 60% of the height free for airflow and heat dissipation. Account for Future Expansion: Add extra height allowance for potential future cable additions.

This ensures maintenance access and avoids costly retrofits. Check Manufacturer Specifications: Tray height may vary slightly by manufacturer, so always confirm the exact dimensions and load capacity.

Practical Tips

For single-layer cable installation, ensure the tallest cable fits comfortably within the tray height while maintaining the recommended fill ratio. In multi-layer or trefoil configurations, calculate the required height based on the sum of cable diameters plus spacing between layers. Always follow NEC, IEC, or NEMA standards for safe installation and compliance.

By following these steps, you can accurately measure the height of cable tray access, ensuring safe, code-compliant, and maintainable cable installations.