How do cables exit from the cable tray

Cables exiting a cable tray should follow NEC guidelines, maintain proper bend radii, and use protective methods such as bushings or flanged openings to ensure safety and equipment compliance.

Methods for Exiting Cables

Cables can exit a cable tray in several ways, depending on the tray type and the equipment being served:

• Through the top or bottom of the tray: Ladder-type trays allow cables to exit from either the top or bottom, providing flexibility for routing into equipment like motor control centers (MCCs) or switchgear enclosures. Proper bend radii must be maintained to prevent cable damage, and rung spacing may need adjustment to accommodate large power cables .
• Via bushed conduit or tubing: NEC 392.46 permits cables to transition from a tray into a raceway with a bushing for protection against physical damage. This method ensures that cables are supported and protected as they leave the tray .
• Through flanged openings on equipment: Cables may also enter equipment through a flanged opening, which should be sealed or covered to prevent debris from entering the enclosure. Duct seal is commonly used for this purpose . It is important to note that cables are not permitted to transition directly from a tray into bushed conduit or flanged connections without proper boxes or protection, according to the 2020 NEC .

Best Practices

• Maintain minimum bending radii: Always follow the cable manufacturer's recommended bend radius to avoid stress or damage to the conductors .
• Use protective bushings: When cables pass through metal edges or openings, bushings prevent abrasion and mechanical damage .
• Label and zone cables: Proper labeling and zoning within the tray improve maintenance, fault detection, and safety by separating power, control, and signal cables .
• Ensure proper ventilation: Ladder trays provide maximum airflow, reducing heat buildup, while solid-bottom trays may require more careful fill calculations to prevent overheating .
• Seal openings: Any transition from tray to equipment should be sealed to prevent dust, debris, or moisture from entering sensitive electrical enclosures .

Summary

Exiting cables from a cable tray requires careful planning to maintain mechanical protection, electrical safety, and code compliance. Using ladder trays, maintaining bend radii, employing bushings or flanged openings, and proper labeling ensures reliable and safe cable transitions from trays to equipment .