Trough-type cable tray with partitions

Trough-type cable trays require proper partitioning, ventilation, and adherence to NEC and NEMA standards to ensure safe cable support and separation.

Overview of Trough-Type Cable Trays

Trough-type cable trays, also known as ventilated trough trays, feature a solid bottom with ventilation openings, typically ranging from 1/4-inch to 1-inch slots or holes. They provide moderate ventilation and better support for cables that might sag between rungs, making them suitable for medium-voltage cables or installations requiring some debris protection . These trays are commonly used in industrial and commercial applications where cable protection and organized routing are essential.

Partitioning Requirements

1. Separation of Cable Types: Partitions are used to separate power, control, and communication cables within the same tray to prevent electromagnetic interference and maintain signal integrity. NEC Article 392 specifies that signal and power cables should be separated when installed in the same tray .
2. Material and Construction: Partitions are typically made of non-conductive or metallic materials compatible with the tray. They must be rigid enough to maintain separation under cable load and environmental conditions .
3. Height and Placement: Partitions should extend above the tray bottom sufficiently to prevent cables from crossing over into adjacent sections. The spacing depends on the cable diameter and fill requirements, ensuring that the tray does not exceed its maximum fill capacity .
4. Ventilation Considerations: Trough trays rely on ventilation slots to dissipate heat. Partitions should not obstruct airflow, as this could reduce ampacity and lead to overheating .

Compliance and Standards

• NEC Article 392: Governs installation, fill limits, and separation requirements for cable trays, including trough-type trays .
• NEMA VE 1: Specifies manufacturing and installation requirements for metal cable trays, including trough trays and associated fittings, and provides load/span class designations .
• UL 568: Covers performance requirements for fiberglass or nonmetallic trough trays, ensuring safe application in industrial environments .

Additional Considerations

• Load and Span: Ensure the tray and partitions can support the combined weight of cables and environmental loads such as wind or snow. Support spacing should follow manufacturer guidelines, typically ranging from 6 to 20 feet depending on tray type and load .
• Maintenance Access: Partitions should allow easy cable installation and removal for maintenance without compromising separation or ventilation .
• Covers: Optional covers may be used for additional protection, but they must not interfere with the tray's ventilation or exceed fill limits . By following these requirements, trough-type cable trays can safely support multiple cable types, maintain proper separation, and comply with electrical codes, ensuring reliable and safe operation in industrial and commercial installations.