Requirements for support installation at cable tray tees

Cable tray tees must be supported at junctions with proper hangers or brackets, maintaining manufacturer-specified spans and ensuring mechanical stability and NEC compliance.

Support and Span Requirements

At a cable tray tee, additional support is required at the junction to handle the combined weight of cables from all branches. The support should be designed to prevent sagging, twisting, or undue stress on the tray system. Typical methods include: Trapeze hangers for ceiling-mounted trays, which can support multiple branches from a single overhead structure.

Cantilever wall brackets for wall-mounted tees, providing lateral support for the branching trays. Direct support from structural beams using threaded rods or clamps, ensuring the tee junction is rigid and level. The distance between supports (support span) must follow the manufacturer's load capacity charts, taking into account the total anticipated cable weight, including future expansion.

Overloading or exceeding the span can lead to mechanical failure or cable damage.

Installation Considerations

Alignment: Ensure the tee is level and properly aligned with the main and branch trays to prevent cable stress. Rung spacing: For ladder-type trays, maintain rung spacing of 6–9 inches (150–230 mm) to support cables adequately at the tee. Cable fill: Do not exceed the tray's fill capacity at the tee; power cables should not exceed 40% of cross-sectional area, and control cables 50%.

Separation: Maintain separation between high-power and low-power cables to prevent electromagnetic interference, especially at junctions. Grounding: Metallic trays at tees must be bonded and grounded according to NEC Article 392 requirements.

Environmental and Material Considerations

Choose tray materials (aluminum, steel, or FRP) suitable for the environment, considering corrosion, temperature, and mechanical load. For outdoor or sunlight-exposed installations, use UV-resistant materials and expansion splice plates to accommodate thermal expansion at tees.

Summary

Supporting cable tray tees requires rigid, properly spaced supports, careful alignment, adherence to fill limits, and compliance with NEC and manufacturer specifications. Using appropriate hangers or brackets, maintaining correct spans, and ensuring grounding and separation will provide a safe, durable, and code-compliant installation.