Installation of Supports for Large-Span Cable Trays

Proper installation of large-span cable tray supports requires careful planning of support spacing, hanger selection, structural attachment, and load management to ensure safety and compliance.

Support Span and Load Considerations

The distance between supports is critical for large-span cable trays. Support spans must be calculated based on the manufacturer's load capacity charts and the total anticipated weight of the cables, including future expansion. Overloading a tray can lead to sagging, conductor damage, or code violations.

For ladder or ventilated trays, typical rung spacing ranges from 6 to 9 inches (150–230 mm) to maintain cable stability and prevent excessive bending.

Support Methods

Common support methods include: Trapeze Hangers: Ideal for ceiling suspensions, these consist of two rods supporting a horizontal bar from which the tray is mounted. Cantilever Wall Brackets: Mounted directly to walls for vertical or horizontal runs along structural surfaces.

All-

Thread Rods with Nuts: Used for precise elevation control; pre-threading nuts and cutting rods to length can save installation time. The choice of support method depends on the building structure, tray route, and load requirements.

Structural Attachment and Safety

Consult structural engineers before drilling into pre-stressed concrete or structural members. Avoid using cable trays as walkways or lifting apparatuses, as they are designed solely for cable support. Elevation benchmarks should be established using laser levels or transit instruments to maintain consistent tray height along long runs.

Use factory-precut rods or supports when possible to reduce on-site errors and ensure thread integrity.

Cable Fill and Routing

Determine cable types and cross-sectional areas to calculate maximum tray fill according to NEC 392. 22. Ensure proper spacing to prevent conductor overheating and maintain ampacity.

Plan cable pulls to minimize bends, using rollers, sheaves, and lubricants to protect cable jackets.

Material Selection and Corrosion Protection

Cable trays are typically made of steel or stainless steel, with galvanization or other surface treatments for corrosion resistance. For industrial environments, select materials that withstand mechanical loads, weather, and ambient conditions.

Best Practices

Install components designed and tested together to ensure system integrity. Maintain consistent support spacing and secure all fittings to prevent tray movement. Monitor tension during cable pulls to avoid damage.

Follow relevant standards such as DIN EN 61537 or BS EN 61537 for tray and ladder systems. By carefully planning support spans, selecting appropriate hangers, ensuring structural integrity, and following cable fill guidelines, large-span cable tray installations can achieve safe, durable, and code-compliant performance.