Ladder or ventilated (perforated) cable trays are recommended for vertical runs in electrical shafts, especially for single-conductor or Type MV cables, to ensure proper support, ventilation, and NEC compliance.

Recommended Cable Tray Types

Ladder Cable Trays Ladder trays consist of two longitudinal side rails connected by transverse rungs, forming an open structure that allows maximum airflow around cables. They are ideal for vertical shafts because they:

• Provide strong support for heavy or single-conductor cables
• Allow cables to be tied securely to rungs to prevent movement in vertical runs
• Promote heat dissipation, reducing the risk of insulation degradation
• Comply with NEC requirements for single-conductor and Type MV cables, which are not permitted in solid-bottom trays Ventilated (Perforated) Cable Trays Perforated trays, also called ventilated trough trays, have a solid bottom with regularly spaced holes. They are suitable for:
• Mixed cable systems including control, instrumentation, and communication cables
• Vertical installations where continuous support is needed to prevent mechanical stress on smaller-diameter cables
• Environments requiring moderate ventilation while providing more support than ladder trays Solid-Bottom Trays Solid-bottom trays are generally not recommended for vertical runs with single-conductor or Type MV cables due to NEC restrictions and limited ventilation. They may be used only when additional protection is required for sensitive cables, but they do not allow proper heat dissipation in vertical shafts .

Installation Considerations

• Cable Securing: In vertical runs, cables should be fastened to the tray's transverse members using listed cable ties to prevent slippage and maintain spacing .
• Material Selection: Choose tray material (galvanized steel, aluminum, or FRP) based on environmental conditions, load, and corrosion resistance .
• Fill Capacity: Ensure the tray is not overfilled; NEC Article 392 specifies maximum fill limits (typically 40% for power cables) to prevent overheating .
• Separation: Maintain proper separation between power and signal cables to avoid electromagnetic interference, especially in vertical shafts where multiple trays may be stacked .

Summary

For vertical cable tray installations in electrical shafts, ladder trays are the preferred choice for heavy or single-conductor cables due to their ventilation, support, and NEC compliance. Ventilated trays are suitable for mixed or lighter cables requiring continuous support. Solid-bottom trays should generally be avoided unless specific protection is required. Proper securing, material selection, and adherence to fill and separation rules are essential for safe and code-compliant installations.