Installation of cable tray supports larger than 500 mm

For cable trays larger than 500 mm, proper support spacing, rung selection, and structural attachment are critical to maintain cable integrity and system safety.

Support Spacing and Structural Considerations

For large cable trays, such as those exceeding 500 mm in width, support elements must be designed to handle the weight of the tray and the cables it carries, including dynamic loads from vibration or short-circuit forces. Typical support elements include wall brackets, suspended supports, and center suspensions, which attach the tray to ceilings, walls, or structural beams. The spacing of supports depends on the tray type, material, and load, but larger trays generally require closer support intervals to prevent sagging and maintain structural integrity.

Ladder and Rung Spacing

For ladder-type cable trays supporting large power cables, it is recommended to use rung spacings of 9 inches (approximately 230 mm) or wider. This ensures that the minimum bending radius of the cables is not violated when they exit the bottom of the tray into equipment. In some cases, 12 or 18-inch rung spacing may be selected to accommodate very large cables or to avoid field modifications such as removing rungs.

Solid and Ventilated TraysSolid-bottom trays are suitable for supporting a large number of small-diameter control or instrumentation cables and can provide EMI/RFI shielding if required. However, they may retain moisture, so weep holes should be drilled every 3 feet to prevent water accumulation in humid or outdoor environments. Ventilated trays allow for better heat dissipation and are preferred when large power cables generate heat.

Installation Best Practices

Always follow manufacturer recommendations for support spacing, load capacity, and rung configuration. Ensure that cable bending radii are maintained to prevent damage to insulation and conductors. Use pre-punched holes or fasteners provided by the manufacturer to attach accessories or modify rungs safely.

Consider environmental factors such as corrosion, vibration, and temperature when selecting materials and finishes for supports. Installation should be performed by competent personnel familiar with electrical standards and safety practices.

Compliance and Standards

Cable tray systems should comply with BS EN 61537 for ladder and tray systems, and BS 6946 for channel support systems. Supports must be capable of withstanding mechanical loads, environmental conditions, and short-circuit forces as specified in these standards. By following these guidelines, cable trays larger than 500 mm can be installed safely, ensuring mechanical stability, proper cable management, and long-term reliability.