Standards for laying control cable trays

Cable tray installation must comply with NEC 392, IEC 61537:2023, and best practice guidelines to ensure safety, proper support, and long-term reliability.

Key Standards and Codes

NEC 392 (National Electrical Code, USA) specifies that only conductors rated for open-air environments, such as Tray Rated (Type TC) or Metal-Clad (Type MC) cables, should be used. Cable trays must maintain at least 12 inches of vertical clearance for installation and maintenance, and metallic trays can serve as equipment grounding conductors if they meet NEC requirements. Fill limits are 40% for power cables and 50% for control cables, and high-power and low-power cables must be separated to prevent electromagnetic interference (EMI) (Electrical Trader) . IEC 61537:2023 (International Standard) defines requirements and tests for cable tray and ladder systems used to support and accommodate cables and other electrical equipment. It covers grouping of cables, protective earth conductor use, and ensures compatibility with electrical and communication systems. This standard supersedes the 2006 edition and includes technical revisions for safety and performance (IEC) . BS EN 61537 (UK/Europe) provides manufacturing and installation guidance for cable ladder and tray systems, emphasizing that these systems are supports for cables, not walkways or ladders, and should be installed by competent personnel familiar with electrical safety practices (BEAMA) .

Material Selection

Cable trays are available in aluminum, steel, stainless steel, or FRP (fiberglass reinforced plastic). Material choice depends on environmental conditions, load requirements, and corrosion resistance. Aluminum offers excellent corrosion resistance due to its natural oxide layer, while stainless steel (AISI 316L) provides superior resistance in chlorinated or harsh environments. FRP offers a high resistance-to-weight ratio and is suitable for corrosive environments (ABB Technical Guide) .

Installation Guidelines

• Tray Types: Ventilated, solid-bottom, or wire-mesh trays are selected based on heat dissipation, EMI protection, and aesthetic requirements.
• Rung Spacing: 6–9 inches (150–230 mm) is recommended for proper cable support.
• Cable Bundling: Cables should be balanced and secured to prevent sagging or mechanical stress.
• Transition to Equipment: Use bushed conduit, tubing, or flanged connections to enter equipment safely.
• Load Considerations: Cable trays must withstand the weight of cables, imposed loads, and short-circuit forces without deformation (ABB Technical Guide) .

Safety and Maintenance

• Avoid installing trays in hoistways or enclosed spaces; they must remain accessible.
• Maintain proper separation between high-power and low-power cables to reduce EMI.
• Ensure grounding continuity for metallic trays.
• Follow fill limits to prevent overheating and mechanical failure.
• Regular inspection and maintenance are essential to ensure long-term reliability and compliance with NEC and IEC standards (Electrical Trader, BEAMA) . By adhering to these standards and best practices, cable tray systems can provide safe, efficient, and durable support for electrical and communication cables in industrial, commercial, and institutional installations.