Cable tray hanger spacing is determined based on tray type, load, and cable weight, typically ranging from 1.5 to 3 meters, with adjustments for bends, tees, and special conditions.

Determining Support Spacing

The spacing of cable tray hangers depends on the type of tray, material, and load of cables. Standard practice for straight runs is to install supports at intervals of 1.5 to 3 meters, ensuring the tray remains stable and prevents excessive sagging or mechanical strain on the cables . For heavier cable loads or wider trays, supports should be placed closer together.

Formula for Support Quantity

To calculate the number of supports required for a cable tray: Support Quantity = (Total Tray Length ÷ Support Spacing) + 1 For example, a 20-meter tray with 2-meter spacing requires: 20 ÷ 2 + 1 = 11 supports . This formula includes supports at both ends and ensures even load distribution.

Special Considerations

• Bends, Tees, and Elbows: These areas experience uneven load distribution and may require additional supports to maintain stability .
• Vertical Runs: Hanging rod supports should be at least 8 mm in diameter to ensure stability and prevent stress on cables .
• Horizontal Spacing: When installing parallel trays, maintain a minimum distance of 0.6 meters for maintenance access and airflow. For power and signal trays crossing each other, a minimum of 0.5 meters is recommended .
• Height Above Ground: Trays should be installed at least 2.2 meters above the floor, with a minimum 0.3 meters clearance from ceilings or obstructions .
• Cable Binding: Tie cables at intervals not exceeding 1.5 meters to maintain order and prevent sagging .

Material and Fire Safety

All supports should be made from fire-resistant materials to prevent premature failure in case of fire, in compliance with BS 7671 Clause 521.10.202 . The stiffness and weight of the cable also affect support spacing; stiffer cables like MDPE sheathed types can span longer distances than LSOH cables for the same allowable sag .

Summary

1. Identify tray type, material, and cable load.
2. Determine standard support spacing (1.5–3 meters for straight runs).
3. Apply the support quantity formula: Length ÷ Spacing + 1.
4. Add extra supports for bends, tees, and heavy loads.
5. Ensure compliance with fire safety, clearance, and accessibility standards. By following these guidelines, cable trays will remain mechanically stable, safe, and accessible for maintenance and future expansion.