High-voltage and low-voltage cables should generally be separated in cable trays, but if co-location is necessary, physical barriers or compartmentalized trays are required to ensure safety and code compliance.

Code and Safety Considerations

According to the National Electrical Code (NEC), mixing power (high-voltage) and low-voltage cables in the same tray is prohibited unless specific separation or shielding measures are implemented (NEC 300.3(C)(1), 725.136, 760.53/760.136) . High-voltage cables can induce voltages in nearby low-voltage circuits, potentially causing electromagnetic interference (EMI), signal distortion, or equipment damage . Fire hazards may also increase if cables are improperly grouped, especially in congested trays .

Acceptable Practices for Co-Location

If it is unavoidable to run high- and low-voltage cables in the same tray, the following best practices should be applied:

• Physical Separation: Use divider brackets or solid fixed barriers to create distinct compartments within the tray, effectively isolating voltage classes .
• Shielding: Low-voltage cables can be shielded and properly grounded to reduce EMI, though shielding alone does not replace the need for separation .
• Zoning: Segregate power and control circuits into different sections of the tray whenever possible .
• Voltage Rating Compliance: Ensure that all cables meet the insulation and voltage rating requirements for the highest voltage present in the tray . For example, multiconductor cables rated over 600 volts must be separated from lower-voltage cables by either a separate tray or a solid fixed barrier, while Type MC cables can sometimes be mixed with lower-voltage cables if proper separation is maintained .

International Standards

The IEC 60364-5-52 standard also recommends physical separation or shielding to prevent interference between power and instrumentation/communication cables . This aligns with NEC guidance and ensures both signal integrity and safety.

Summary

While it is technically possible to store high-voltage and low-voltage cables in the same cable tray, it is strongly recommended to maintain separation using barriers, compartmentalized trays, or dedicated pathways. This approach minimizes EMI, voltage induction, and fire risks, ensures compliance with NEC and IEC standards, and facilitates successful inspections .