Cables can be drilled through the bottom of the cable tray

Cables can enter or exit through the bottom of a cable tray, especially in ladder-type trays, provided proper precautions are taken to protect the cables and maintain code compliance.

Ladder Cable Trays

For ladder-type cable trays, it is common and acceptable for cables to exit or enter through the bottom of the tray. This configuration is often used when routing cables into equipment such as motor control centers (MCCs) or switchgear enclosures . Ladder trays without covers allow maximum airflow, which helps dissipate heat from current-carrying conductors, and moisture cannot accumulate as it might in conduit systems . When cables exit the bottom, it is important to respect the manufacturer's recommended minimum bending radii to prevent damage to the cable insulation .

Solid-Bottom and Ventilated Trough Trays

For solid-bottom trays, cables are typically routed on top, but drilling drain holes in the bottom is permissible to prevent moisture accumulation if the tray is not being used for EMI/RFI shielding . Ventilated trough trays also allow bottom entry, but care must be taken to avoid excessive drooping of small-diameter cables between rungs or supports .

Protection and Accessories

When cables exit the bottom of a tray, especially in systems subject to vibration, it is recommended to use cable channel bushings or similar protective devices to prevent abrasion and damage to the cable jackets . Additionally, field modifications such as drilling or cutting tray sections should be done carefully, smoothing edges to remove burrs and using protective coatings if necessary .

Summary

• Yes, cables can be routed through the bottom of ladder, ventilated trough, and solid-bottom trays under proper conditions.
• Maintain proper bending radii to avoid cable damage.
• Use bushings or protective devices where vibration or abrasion is a concern.
• Drill drain holes in solid-bottom trays if moisture accumulation is possible and EMI/RFI shielding is not required.
• Always follow NEC Article 392 and manufacturer guidelines for tray type, fill limits, and installation practices . By following these guidelines, bottom entry or exit of cables can be safely implemented without compromising cable integrity or system performance.