Ladder-type span cable trays

The span of a ladder-type cable tray is the distance between support points and depends on load, tray width, rung spacing, and material, typically ranging from 2 to 6 meters for standard installations.

Key Considerations for Span

Support Span Definition: The support span is the distance between two points that hold the tray, separate from the overall tray length. Longer spans reduce the number of supports but require lower load per meter, while shorter spans allow higher loads and less deflection. Material and Construction: Ladder trays are usually made from steel, aluminum, or fiberglass-reinforced composites.

Fiberglass trays, for example, have specific load vs. span ratings per IEC 61537, and their deflection is measured at mid-span. Steel and aluminum trays have standard rung spacings (150 mm, 225 mm, 300 mm) and typical support spans of 2–6 meters depending on load. Tray Width and Rung Spacing: Wider trays and larger rung spacing reduce overall strength.

For example, Eaton's B-Line series recommends stronger rungs for trays wider than 36 inches to maintain load capacity. Narrower trays with smaller rung spacing can support small-diameter control cables with minimal droop. Load Considerations: Maximum allowable load per meter decreases as span increases.

Designers must check manufacturer load tables to ensure the selected span supports the intended cable weight without excessive deflection. Outdoor or long-span installations (20–40 feet) require careful placement of splice plates and may need additional structural reinforcement. Installation Guidelines: Use one splice plate per support span to maintain structural integrity.

Ensure tray length is equal to or longer than the support span. For heavy power cables, select appropriate rung spacing (≥9 inches) to prevent sagging.

Follow NEM

A VE-1/VE-2 and NEC/CEC standards for support spacing and load ratings. Summary: Standard ladder-type cable trays typically have support spans of 2–6 meters for indoor installations, with longer spans possible for lighter loads or reinforced trays. Span selection must consider tray material, width, rung spacing, cable weight, and environmental conditions to ensure safety and compliance with standards.