Low-voltage cables should not be run in cable trays

Low-voltage cables, such as instrumentation, control, and communication lines, should generally not share cable trays with high-voltage power cables due to safety and signal integrity concerns.

Reasons to Avoid Mixed Trays

Electromagnetic Interference (EMI): Low-voltage cables carry sensitive signals that can be disrupted by nearby high-voltage power cables. Running them together can cause noisy signals, incorrect readings, and unstable system performance .

Mechanical and Environmental Risks: Low-voltage cables are often more delicate and can be damaged by improper tray selection, excessive fill, or exposure to dust, moisture, or corrosive environments. Using the wrong tray type, such as perforated trays in corrosive areas, can reduce reliability over time .

Code Compliance: NEC and industry standards require separation of different voltage classes to prevent hazards. For example, NEC 725.136 prohibits Class 2/3 circuits from sharing space with Class 1 circuits unless specific wiring methods are used . Cable trays must remain accessible and properly grounded, and low-voltage cables may require dedicated trays to meet these requirements .

Best Practices for Low-Voltage Cable Tray Installation

• Dedicated Trays: Use separate trays for low-voltage instrumentation, control, and communication cables to prevent interference and simplify maintenance .
• Tray Type Selection: Ladder trays are ideal for long runs needing airflow, solid-bottom trays protect delicate cables from EMI and environmental hazards, and wire mesh trays offer flexible routing .
• Spacing and Shielding: Maintain adequate spacing between low-voltage and power cables, and use shielded cables where necessary to reduce EMI .
• Future Expansion: Design trays to allow for additional cables without interfering with existing installations .
• Material Considerations: In corrosive or humid environments, stainless steel trays are recommended to prevent degradation .

Summary

Running low-voltage cables in the same tray as high-voltage power cables is strongly discouraged due to EMI, safety, and code compliance issues. Dedicated trays, proper spacing, shielding, and appropriate tray materials ensure reliable signal transmission, long-term system integrity, and adherence to NEC and industry standards .