Requirements for Fire Cable Tray Support Arms

Fire-rated cable tray support arms must be made of materials that withstand temperatures above 1084°C, be certified for fire resistance, and spaced no more than 1 metre apart to prevent premature collapse.

Material and Fire Resistance

Fire-rated supports must be manufactured from materials that do not fail under extreme heat, with a melting point exceeding 1084°C. They must be capable of securing cables for at least 2 hours under fire conditions, ensuring that wiring systems remain intact and do not collapse prematurely, which is critical for safe evacuation and firefighting operations . Non-metallic supports or PVC clips alone are not acceptable for exposed surfaces or suspended cable trays in fire-rated installations .

Spacing and Installation

Supports should be spaced at intervals no greater than 1 metre to prevent cables from sagging or encroaching into passageways during a fire . The exact spacing may also depend on cable type, diameter, and weight, following guidance from BS 7671 Section 522.8 and IET Selection and Erection Guidance Notes . For fire alarm and detection systems, BS5839-1 requires strict adherence to fire-rated support spacing and installation practices .

Certification and Compliance

All fire-rated support arms must have certificates of conformity validating their fire resistance and suitability for securing cables under fire conditions . This ensures compliance with BS 7671:2018 and provides assurance that the installation meets safety standards.

Best Practices

• Use metallic or certified fire-rated supports for exposed or suspended cable trays.
• Avoid relying solely on PVC clips or non-metallic trunking for fire-critical installations .
• For non-metallic trunking, hinged-lid versions are preferred to maintain cable security during fire events .
• Ensure supports are installed by competent personnel familiar with electrical installation standards and fire safety requirements . By following these requirements, cable tray systems will remain secure during a fire, minimizing the risk of cable collapse and ensuring safe evacuation and operational continuity.