Proper installation of cable trays in low-voltage shafts requires selecting the right tray type, ensuring adequate support, maintaining proper spacing, and following grounding and safety standards.

Selecting the Appropriate Cable Tray

For low-voltage applications, ladder trays are commonly used for power cables due to their excellent ventilation and convenient rungs for securing cables, while ventilated trough trays are ideal for smaller control and instrumentation cables that may sag between rungs . In corrosive or high-moisture environments, fiberglass-reinforced plastic (FRP) trays provide corrosion resistance and non-conductivity, enhancing safety . Material choice should consider environmental conditions, mechanical strength, and electrical insulation requirements .

Support and Spacing

Cable trays must be structurally supported along their length to prevent sagging and maintain cable integrity. Typical support spans vary by tray type and load, but rungs should generally be spaced 150–230 mm (6–9 inches) for ladder trays to ensure proper cable support . Supports should be anchored to the shaft walls or ceiling using brackets or hangers rated for the tray load. Avoid overloading trays to prevent overheating and mechanical stress.

Cable Management and Routing

Maintain the minimum bend radius for cables as they exit or enter the tray to prevent conductor damage . Use cable ties or clamps at intervals to secure cables without compressing insulation. For low-voltage systems, separate power and control cables where possible to reduce electromagnetic interference. Solid covers or ventilated lids can be used to protect cables from dust or accidental contact while allowing heat dissipation .

Grounding and Bonding

All metallic cable trays must be properly grounded and bonded according to NEC Article 392 and local electrical codes . This ensures safety by providing a low-resistance path for fault currents and reduces the risk of electrical shock or fire.

Compliance and Safety

Ensure that the selected cable trays comply with relevant standards such as UL, NEMA, or CE marking, depending on your location . Verify that the tray system is suitable for the voltage, current, and environmental conditions of the installation. Regular inspections and adherence to manufacturer guidelines are essential for long-term reliability and safety.

Summary

1. Choose the tray type based on cable size, type, and environmental conditions.
2. Install supports at recommended intervals and maintain proper rung spacing.
3. Secure cables while respecting minimum bend radii and separation requirements.
4. Ground and bond metallic trays according to code.
5. Verify compliance with standards and manufacturer specifications. Following these practices ensures a safe, organized, and code-compliant cable tray installation in low-voltage electrical shafts, facilitating maintenance and future upgrades.