Fireproof sealing of vertical cable trays in electrical wells

Vertical cable trays in electrical wells must be sealed with certified firestop materials to maintain fire resistance and prevent smoke and heat spread.

Key Principles

Firestopping for vertical cable trays involves sealing all openings where trays pass through walls, floors, or shafts using materials that restore the fire-resistance rating of the building element . The seal must be tight, reliable, and free of cracks or voids, ensuring that fire and smoke cannot propagate through the penetration .

Recommended Materials

1. Firestop Packs and Pillows: Intumescent or ablative pillows, such as AF BAGS, are suitable for vertical cable tray penetrations. They expand under heat to seal gaps and can accommodate cables up to 21 mm in diameter, providing protection up to EI 240 .
2. Firestop Mastic or Caulk: Products like 3M Fire Barrier Moldable Putty+ or IC 15WB Caulk can seal irregular gaps around trays and conduits, offering intumescent properties to block heat and smoke .
3. Fire-Resistant Mineral Wool: Often used in combination with backing plates for larger openings, mineral wool provides thermal insulation and structural support for the seal .
4. Fire-Rated Boards: For large or structural penetrations, fire-rated boards can be installed as backing before applying mastic or pillows .

Installation Guidelines

• Measure and Plan: Determine the tray dimensions and the number of firestop units required to completely fill the penetration .
• Backer Installation: For large openings, install a fire-resistant backing plate to support the firestop material .
• Packing and Sealing: Place firestop packs or pillows in an orderly sequence, ensuring gaps between the material and cables do not exceed 1 cm² and packing thickness meets manufacturer specifications .
• Cover Plates: Use square, evenly painted cover plates to close the opening, ensuring a neat and secure finish .
• Vertical Alignment: Ensure trays are plumb and securely mounted; deviations should not exceed 3 mm per meter .

Maintenance and Inspection

• Routine Checks: Inspect seals periodically for integrity, signs of compression, or damage.
• Heat Dissipation: Maintain adequate spacing between cables and use perforated trays if necessary to prevent heat accumulation .
• Retrofit and Modification: Firestop pillows and caulks can be repositioned or reapplied during maintenance without compromising fire protection .

Compliance

All fireproof sealing must comply with EN 1366-3 or equivalent local fire-resistance standards, ensuring that the firestop system matches the required EI rating for the wall, floor, or shaft penetration . Only certified products should be used, and installation should follow manufacturer instructions and building authority regulations . By following these guidelines, vertical cable trays in electrical wells can be effectively fireproofed, maintaining safety, compliance, and long-term reliability.