How to connect multiple cable trays to the low-voltage wiring shaft

Cable trays in low-voltage shafts should be joined using mechanically secure methods like splice plates, bolted connections, or quick-connect systems, ensuring proper alignment, grounding, and compliance with NEC standards.Key Steps for Connecting Cable Trays1. Select the Appropriate Tray Type and Material Choose a tray suitable for low-voltage cables, such as ladder or ventilated trough trays, made from steel, aluminum, or fiberglass-reinforced plastic (FRP) depending on environmental conditions and load requirements . Ladder trays are ideal for power and larger conductors, while ventilated troughs support smaller control and instrumentation cables . 2. Align Adjacent Tray Sections Ensure that tray sections are properly aligned before joining. Misalignment can cause sagging, cable damage, or uneven load distribution . Maintain a minimum clearance of 20mm behind trays wherever possible to allow for cable installation and maintenance . 3. Use Mechanical Connection Methods Common methods include:Splice Plates and Bolted Connections: Flat metal plates with pre-drilled holes are bolted to the ends of two tray sections. This provides a strong, secure connection suitable for straight runs and heavy cable loads .Quick-Connect Systems: Snap, slide, or twist mechanisms allow faster installation with minimal tools, ideal for large projects or when using a single manufacturer's trays .Angle Plates (L, T, or Cross): Used to join trays at corners or junctions, ensuring proper routing around bends . 4. Ensure Proper Bonding and Grounding Metallic trays must be bonded to serve as an equipment grounding conductor (EGC) if required by NEC Article 392 . Connections should be mechanically strong to prevent relative movement and maintain electrical continuity . 5. Handle Cable Entry and Exit Points Perforations for cable entry should be grommeted, bushed, or lined to prevent insulation damage . Avoid placing cable entries within the circular portion of bends for trays with nominal widths of 100mm or 150mm . 6. Support and Span Considerations Support trays at intervals not exceeding 1500mm on steelworks of adequate strength. Ensure that tray deflection does not exceed 1/100 of a 1.2m span after cable installation . Expansion joints should be bridged with flexible conductors rather than directly joining trays across the joint . 7. Maintain NEC Compliance and SafetyUse only tray-rated (Type TC) or metal-clad (Type MC) cables .Maintain vertical clearance for access and maintenance.Separate high-power and low-power cables to prevent EMI .Avoid installing trays in hoistways or enclosed spaces . Following these steps ensures a secure, durable, and code-compliant cable tray system in low-voltage electrical shafts, facilitating safe cable routing, easy maintenance, and long-term reliability.