Requirements for the use of cable tray hangers

Cable tray hangers must comply with standards ensuring mechanical support, fire resistance, and safe spacing, as outlined in BS 7671, IEC 61537, and NEC Article 392.

UK Regulations (BS 7671 and 18th Edition Wiring Regulations)

In the UK, BS 7671 and the 18th Edition Wiring Regulations require that cables are adequately supported to prevent mechanical strain and premature collapse, especially in the event of a fire (Regulation 521.10.202) . Key points include:

• Material requirements: Cable supports must be fire-resistant; non-metallic clips or ties cannot be the sole means of support for cables clipped directly to surfaces or suspended under trays .
• Spacing: Support intervals depend on cable type and diameter, with guidance provided in IET Selection and Erection Guidance Notes. Horizontal and angled runs have specific spacing rules to prevent sagging or mechanical stress .
• Supplementary supports: Plastic fixings may be used but must be supplemented with metal clips, saddles, or ties to meet compliance .
• Safety considerations: Supports must not obstruct access or egress routes and should maintain cable integrity during fire events .

International Standards (IEC 61537)

IEC 61537 provides global guidance for metallic cable tray systems :

• Mechanical strength: Trays and hangers must withstand the weight of cables, environmental loads, and short-circuit forces. Load testing is required to validate strength.
• Corrosion resistance: Materials must resist corrosion in specific environments, including marine or chemical settings.
• Electrical continuity: Metal trays often serve as grounding paths, and continuity must be ensured.
• Fire resistance: Supports must maintain structural integrity under high temperatures.
• Installation compatibility: Hangers and trays must be compatible with bends, risers, and other accessories to ensure a secure and continuous support system.

US Regulations (NEC Article 392)

In the United States, NEC Article 392 governs cable tray systems :

• Support function: Cable trays are considered support structures, not raceways, and must be installed to prevent sagging or mechanical failure.
• Cable types: Only cables rated for tray use (Type TC or metal-armored Type MC) are permitted.
• Covers: Optional but recommended in high-traffic or outdoor areas to protect cables.
• Installation: Hangers must be designed to handle the weight of cables and any imposed loads, ensuring safety and compliance with electrical codes.

Best Practices

• Competent installation: Only trained personnel familiar with electrical installation standards should install cable trays and hangers .
• Load balancing: Cables should be bundled and balanced to prevent uneven stress on hangers.
• Avoid misuse: Cable trays and hangers are not designed to support people or heavy equipment, which could compromise safety and system integrity .
• Regular inspection: Periodic checks ensure hangers remain secure, corrosion-free, and compliant with fire safety requirements. In summary, cable tray hangers must be metallic or fire-resistant, spaced according to cable type and load, and installed to maintain mechanical integrity and safety under normal and fire conditions, following BS 7671, IEC 61537, and NEC Article 392 standards. Proper installation and maintenance are essential to ensure compliance and prevent hazards.