Reserved holes in cable trays must be tightly sealed using fire-resistant materials, ensuring no visible gaps, proper thickness, and compliance with fire safety standards.

Firestopping and Sealing Principles

Reserved holes in cable trays, whether in walls, slabs, or electrical shafts, must be sealed to prevent fire and smoke propagation. Openings should be tightly filled with firestopping materials such as fire-rated boards, firestop packs, firestop mastic, or fire-resistant mineral wool. The seal must be continuous, without visible cracks or voids, and all gaps inside and around metal trunking must be completely sealed both internally and externally .

Material and Installation Requirements

• Firestop Packs: Should be placed in an orderly sequence, with the gap area between packs and cables not exceeding 1 cm² and a minimum packing thickness of 24 cm .
• Backing Plates: For large openings, a fire-resistant backing plate should be installed before sealing to provide structural support and ensure complete coverage .
• Cover Plates: Should be square, consistent in size, and evenly painted, used to close the opening after sealing .
• Waterstop: At floor level or slab penetrations, a waterstop of at least 50 mm height is recommended to prevent water ingress .
• Fire-support Plate: At slab penetrations, provide 20–30 mm of firestopping and install a fire-support plate at the top .

Standards and Testing

Cable tray penetration seals should comply with European Standard EN 1366-3 for fire resistance and be classified according to EN 13501-2. The required thickness of firestop coatings, such as PROMASTOP®-CC, depends on the type of cable or conduit and the number of cable groups. Metal conduits require thicker coatings due to heat conduction, and plastic conduits may require additional coating to compensate for melting .

Installation Sequence

1. Complete floor and wall finishes in the electrical shaft and install shaft doors.
2. Install busways, cable trays, and distribution boxes.
3. Route cables and perform grounding.
4. Apply waterproofing measures.
5. Seal reserved openings with firestopping materials, ensuring proper packing, thickness, and backing plates as needed .

Key Considerations

• Ensure layout and positioning facilitate installation and maintenance.
• Use materials that are resistant to moisture and high humidity if the area is wet .
• Verify that all seals are tight, reliable, and compliant with fire safety regulations. By following these requirements, reserved holes in cable trays can be effectively sealed, maintaining both fire safety and structural integrity while complying with relevant standards .