Requirements for cable bundling spacing inside cable trays

Cables in trays should be bundled and secured with spacing that ensures proper airflow, heat dissipation, and mechanical stability, typically with ties every 1.5 meters and careful attention to bundle diameter and tray fill.

Horizontal and Vertical Runs

For horizontal cable tray runs, cables should be secured at the start, end, and at every 3 to 5 meters along straight sections. For vertical runs, cables should be tied at the top and every 1.5 meters to maintain stability and prevent sagging or stress at bends . Cables should be laid straight, avoiding overlaps or crossings, and all bends must be securely fastened.

Cable Tie and Bundle Spacing

When binding cables into bundles, the distance between ties should not exceed 1.5 meters, ensuring even tension and preventing cable movement . The bundle diameter (BD) and spacing (S) between adjacent bundles are critical for calculating tray capacity and maintaining safe installation. Larger bundle diameters or reduced spacing can increase tray fill, potentially affecting airflow and heat dissipation .

Tray Fill and Airflow

The cross-sectional fill rate of cables within a tray should generally not exceed 50% for control, signal, or communication cables, and 40% for power cables, to allow proper ventilation and prevent overheating . Maintaining a 20% void ratio between cables is recommended to optimize airflow and thermal performance .

Clearance and Installation Guidelines

• Height above ground: Minimum 2.2 meters
• Top clearance: At least 0.3 meters from ceilings or obstructions
• Tray width: Minimum 0.1 meters
• Concealed installations: Maintain 80 mm vertical clearance for access

Summary

Proper cable bundling in trays involves:

• Securing cables at regular intervals (horizontal: 3–5 m, vertical: 1.5 m)
• Binding bundles with ties spaced no more than 1.5 m apart
• Maintaining tray fill below recommended limits (40–50%)
• Ensuring adequate clearance for airflow, maintenance, and safety
• Considering bundle diameter and spacing to optimize tray capacity and prevent overheating Following these guidelines ensures mechanical stability, thermal safety, and compliance with electrical standards in cable tray installations.