The height of fireproof cable tray partitions is not fixed and depends on the cable tray size, firestop system, and regulatory requirements, but typical fire-blocking sections are designed to fully cover the tray height plus a safety margin.

General Guidelines

Fireproof cable tray partitions, also called fire-blocking sections or fire partitions, are installed to prevent the spread of fire along cable trays and ensure safe operation of electrical systems . The height of these partitions is generally determined by:

• Tray dimensions: The partition must extend above the top of the cable bundle to fully isolate the section. For example, openings are often made 1.5 inches larger than the tray on all sides to accommodate firestop materials .
• Firestop material thickness: Firestop packs, boards, or mineral wool are used to fill gaps. The packing thickness is typically not less than 24 cm for large openings .
• Regulatory requirements: Fire-rated walls or partitions must meet UL or local fire codes, which may specify minimum coverage or clearance above the cable tray .

Installation Considerations

• Material selection: Fireproof boards, coatings, bags, or intumescent caulks are commonly used. The choice affects the partition height and coverage needed .
• Gap sealing: All gaps around the tray must be sealed tightly, with no visible cracks, to maintain fire resistance .
• Accessibility: Partitions should allow for cable installation and maintenance while maintaining fire protection .

Practical Example

For a 4” x 12” ladder tray, the recommended firestop opening would be approximately 7” x 15”, which implies the partition height should cover the tray height plus at least 1.5 inches on top and bottom to ensure complete fire isolation . Larger trays or bundles require proportionally taller partitions.

Key Takeaway

While there is no universal fixed height, fireproof cable tray partitions should fully cover the cable tray height with additional clearance to accommodate firestop materials and comply with fire safety standards. Designers should refer to UL-listed systems, local fire codes, and manufacturer guidelines to determine the exact height for each installation .