Cable tray connections and spans

Cable tray span connections are achieved using splice plates between tray sections, with support spacing carefully designed to maintain structural integrity and comply with standards.

Splice Plates and Tray Connections

Splice plates are used to connect two sections of cable tray, ensuring both mechanical strength and electrical continuity. For optimal performance, it is recommended to place only one splice plate per support span. The tray length should be equal to or longer than the support span to control splice locations and maintain structural integrity.

Some systems, like Eaton's B-Line KwikRail, feature side rails with splice-retention grooves that allow easy alignment and secure attachment with just two bolts.

Support Span Considerations

The support span is the distance between two supports holding the cable tray. Proper support spacing is critical because the tray strength decreases exponentially with longer spans. Outdoor installations may require spans of 20 to 40 feet, and extra-long spans reduce the number of supports needed but increase the importance of correct splice placement.

Support locations should follow standards such as NEMA VE-1 and VE-2, which align with the NEC and CEC requirements.

Load Class and Tray Strength

Cable trays are rated by load class, which defines the maximum load they can carry for a given support span. Selecting the correct load class ensures the tray can safely support the cables without excessive deflection or risk of failure. The design should consider the total working load, including power, instrumentation, and communication cables, as well as environmental factors.

Best Practices

Align tray sections carefully to avoid misalignment at splice points. Use only compatible components from the same manufacturer to ensure mechanical and electrical compatibility. Verify support spacing against the tray's rated load class to prevent sagging or structural failure.

Consider thermal expansion for long outdoor runs, which may require expansion joints or flexible connections. Install by qualified personnel familiar with electrical installation standards and safety practices. By following these guidelines, cable tray systems can maintain reliability, safety, and compliance while accommodating long spans and heavy cable loads.

Proper splice plate placement and support spacing are essential for both mechanical stability and electrical grounding.