Cable trays and corrugated pipes

No, cable trays do not require corrugated pipes as long as the cables are properly insulated and rated for tray use.

Cable Tray Function and Standards

Cable trays are designed as support systems for electrical, power, signal, and communication cables, providing mechanical support without fully enclosing the cables like a conduit would.

According to NE

C Article 392, cable trays are considered a support structure rather than a raceway, meaning the cables are exposed to air and must have sufficient insulation or armor, such as Type TC (Tray Cable) or metal-armored (Type MC) cables. This eliminates the need for additional corrugated pipes for protection under normal conditions.

When Corrugated Pipes Are Not Needed

Mechanical Protection: Modern cables used in trays already have protective sheathing or armor, so corrugated pipes are redundant. Compliance: NEC explicitly prohibits using tubes or pipes for non-electrical services within cable trays, reinforcing that additional conduits are unnecessary for electrical cables. Accessibility: Cable trays are designed for easy access, inspection, and maintenance, which would be hindered by enclosing cables in corrugated pipes.

Exceptions and Considerations

While corrugated pipes are generally not required, they may still be used in specific scenarios: High-risk environments: If cables are exposed to corrosive chemicals, extreme heat, or physical damage, additional protective conduits may be considered. Outdoor or high-traffic areas: Solid covers or protective conduits can be added to shield cables from falling objects or UV exposure. Instrumentation or control cables: In some sensitive applications, small control cables may be routed through additional protective tubing for extra mechanical protection.

Summary

In modern installations, corrugated pipes are not required for cables in trays as long as the cables are properly rated and sheathed. Cable trays themselves provide support and organization, and NEC standards ensure safety without the need for additional conduits. Corrugated pipes are only used in special conditions where extra protection is necessary due to environmental or mechanical risks.