Cable connection for vertical shaft cable trays

Cable trays can be connected to vertical shafts using properly supported vertical risers, bends, and tees while ensuring compliance with load, spacing, and fire safety standards.

Material and Design Considerations

When connecting cable trays to vertical shafts, select materials that meet mechanical strength and corrosion resistance requirements, such as cold-rolled steel, galvanized steel, or aluminum alloy. Surface treatments like hot-dip galvanizing or electrostatic spraying enhance durability, and the tray system should support at least 200 kg/m and meet fire resistance standards (GB 8624 Class B1) if applicable . Ensure the tray path avoids obstructions like ventilation ducts or plumbing, maintaining a minimum clearance of 300 mm .

Vertical Riser Installation

Vertical shafts typically use vertical risers to carry the main cable tray backbone. These risers should be securely supported using cantilever wall brackets or trapeze hangers, depending on the shaft structure . When branching off to horizontal trays at each floor, use elbows or downward bends to allow cables to sweep smoothly from the vertical tray to the horizontal run . This avoids sharp bends that could damage cables or exceed minimum bend radius requirements .

Tee and Branch Connections

For branching horizontal trays from a vertical riser:

• Use a vertical down tee or create a combination of horizontal runs with a bend to connect to the vertical tray .
• Ensure the connection maintains proper spacing between power and weak-current trays (minimum 150 mm) and includes isolation plates at crossings if necessary .
• If a pre-manufactured tee is unavailable, a custom fitting or BIM family can be created to simulate the connection in design software, ensuring accurate alignment and cable routing .

Support and Safety

• Vertical trays must be anchored at regular intervals to prevent sagging or excessive load on the shaft structure .
• Maintain firestop clearances when passing through fire compartments, using certified firestop materials .
• Avoid overfilling trays; calculate cable fill according to NEC 392.22 to prevent overheating and maintain ampacity .

Practical Tips

• Start horizontal branches with a downward bend from the vertical riser to facilitate cable installation.
• Use ventilated or ladder trays for large power cables to allow heat dissipation, and solid or channel trays for smaller instrumentation cables .
• Ensure all components are compatible and tested together to maintain system integrity and safety . By following these guidelines, cable trays can be safely and efficiently routed through vertical shafts, providing reliable support for electrical and communication systems while complying with building codes and safety standards.