The trough-type cable tray has been made into a trapezoidal cable tray

Converting from trough-type to trapezoidal cable trays requires evaluating load capacity, cable support, and structural compatibility to ensure safe and efficient cable management.

Understanding the Tray Types

Trough-type cable trays are rigid structures with a solid or ventilated bottom and side rails, providing continuous support for cables and protection against dust, moisture, and debris. They are ideal for horizontal runs and environments where minimal cable sag is critical, supporting large volumes of power and control cables effectively . Trapezoidal cable trays feature a sloped or angled bottom, often with side rails, designed to optimize material usage and reduce weight while maintaining structural strength. They are commonly used where load distribution and airflow are important, and they can accommodate similar cable types as trough trays but may require adjustments in support spacing and cable tie methods.

Key Considerations for Conversion

1. Load Capacity and Structural Support
   • Trough trays are designed for heavy cable loads with solid bottoms, while trapezoidal trays may have different load ratings. Check the manufacturer's load charts to ensure the trapezoidal tray can safely support the existing cable weight .
   • Support spacing may need adjustment; wider spans reduce strength, so additional hangers or brackets may be required .
2. Cable Support and Spacing
   • Trough trays provide continuous support, minimizing sag. Trapezoidal trays may require additional cable ties or crossbars to prevent sagging, especially for small-diameter control or instrumentation cables .
   • Maintain proper minimum bend radius for cables when transitioning to a trapezoidal profile to avoid stress or insulation damage .
3. Thermal Management
   • Ventilated trough trays allow heat dissipation. If converting to a trapezoidal tray with less ventilation, consider cable derating for heat-sensitive conductors .
   • Solid or partially solid trapezoidal trays may require ventilation holes or spacing adjustments to prevent overheating.
4. Material and Environmental Compatibility
   • Ensure the trapezoidal tray material (steel, aluminum, or FRP) matches the environmental requirements, such as corrosion resistance or chemical exposure .
   • Aluminum or stainless steel trays offer corrosion resistance, while fiberglass-reinforced plastic (FRP) is suitable for high-moisture or corrosive environments.
5. Installation and Code Compliance
   • Verify that the new tray system complies with NEC Article 392 or local electrical codes for cable support, grounding, and bonding .
   • Modular design of trapezoidal trays may require splice plates, end fittings, and proper alignment with existing runs to maintain continuity and safety.

Practical Steps for Conversion

• Assess existing cable load and tray dimensions.
• Select trapezoidal trays with adequate load rating and width.
• Adjust support spacing and add hangers if necessary.
• Install cable ties or crossbars to maintain cable alignment.
• Check thermal performance and derate cables if ventilation is reduced.
• Ensure grounding and bonding continuity across the new tray sections. By carefully evaluating these factors, you can safely convert a trough-type cable tray system to a trapezoidal design while maintaining cable integrity, structural safety, and compliance with electrical standards.