Earthquake-resistant cable tray installation in New Zealand

All cable tray systems in New Zealand must be seismically restrained according to NZS 4219: 2009, unless supporting only non-essential services or suspended less than 400mm below structural support.

Key Standards and Requirements

Cable tray installations must comply with NZS 4219: 2009, which governs the seismic performance of non-structural building elements. Key points include: Mandatory Restraints: All cable trays must be restrained to prevent movement in all directions during an earthquake, except for non-essential electrical services or trays suspended less than 400mm from the structural support. Fixings and Bracing: Use bolts, anchors, brackets, cleats, gusset plates, or similar devices to attach trays to the building structure.

Fixings must transfer seismic forces effectively and employ positive locking mechanisms to prevent disengagement. Load Classification: Emergency electrical systems should be classified as P4, while non-essential systems are P7. P4 systems include critical services like emergency lighting and must remain operational during seismic events.

Design Considerations: Restraint systems should accommodate building drift, vibration, and floor movement without damaging the cable tray or connected equipment.

Installation Practices

Transverse and Longitudinal Bracing: Horizontal cable trays require at least two transverse restraints and one longitudinal restraint per straight segment. Vertical trays require two transverse restraints in each orthogonal direction. Suspended Trays: Ensure that suspended trays are supported with seismic hangers or wire systems that can resist earthquake forces.

Avoid long unsupported spans and provide lateral bracing where necessary. Critical Equipment Support: Any heavy or essential equipment mounted on trays, such as power distribution units or communication hubs, should be independently braced to prevent damage during seismic events.

Engineering and Supplier Support

Specialist seismic engineering services in New Zealand, such as MSS, Gripple, and USL Multistrut, provide: Seismic load calculations and compliant bracing designs. Full documentation and installation guidance aligned with NZS 4219. Upgrades for existing cable tray systems to meet seismic requirements.

Certified seismic restraint products, including brackets, channels, and fixings suitable for New Zealand conditions.

Practical Recommendations

Engage a certified seismic engineer to design and verify cable tray restraints, especially for critical infrastructure like hospitals, data centers, or schools. Use positive locking fixings and ensure all connections are capable of transferring seismic forces to the building structure. Document all installations for compliance and project certification, including PS1 and PS4 forms where applicable.

Consider retrofitting older installations with seismic bracing to improve resilience and minimize operational disruption during earthquakes. By following these standards and best practices, cable tray systems in New Zealand can remain secure, functional, and compliant during seismic events, protecting both equipment and building occupants.