Cables in a two-layer cable tray should be secured using proper layering, separation, and fastening techniques to ensure safety, prevent sagging, and maintain code compliance.

Layering and Organization

When using a two-layer cable tray, organize cables by type and size. Place larger power cables on the bottom layer and smaller control or instrumentation cables on the top layer to maintain stability and reduce interference. Maintain separation between high-power and low-power cables to prevent electromagnetic interference (NEC 392 guidelines) and ensure proper airflow for heat dissipation . Use cable ties, clamps, or lacing bars at regular intervals to keep cables in place and prevent sagging .

Securing Methods

1. Cable Ties and Clamps: Use UV-resistant or insulated cable ties for non-metallic trays and metal clamps for metallic trays. Secure cables at rung intervals of 6–9 inches (150–230 mm) for ladder trays to prevent movement .
2. Lacing Bars or Crossbars: Install lacing bars between tray rungs to support multiple layers of cables, especially for heavy or bundled runs. This helps maintain the minimum bend radius and prevents cable damage .
3. Spacers or Dividers: Use vertical dividers to separate layers and maintain consistent spacing. This is particularly important for mixed cable types or when the tray is near its fill limit .
4. Bonding and Grounding: For metallic trays, ensure proper bonding and grounding to meet NEC requirements. This prevents electrical hazards and ensures the tray can act as an equipment grounding conductor if needed .

Installation Tips

• Avoid overfilling: Keep power cables below 40% of the tray cross-section and control cables below 50% to allow airflow and reduce heat buildup .
• Maintain bend radius: Ensure cables exiting the tray do not exceed their minimum bend radius to prevent insulation damage .
• Secure at transitions: At tray joints, bends, or T-junctions, use splice plates, clamps, or bolted connections to maintain stability and prevent cable movement .
• Future maintenance: Leave enough space for adding or removing cables without disturbing the existing layers. Properly secured cables make maintenance safer and easier . By following these practices, a two-layer cable tray system will remain organized, safe, and compliant, minimizing mechanical stress on cables and ensuring long-term reliability.