Cable trays passing through walls or slabs must be properly firestopped, sealed, and supported according to fire safety and electrical installation standards.

Firestopping Requirements

Cable tray penetrations through walls or slabs must be tightly sealed with fire-resistant materials to prevent the spread of fire and smoke. Openings should be free of visible cracks or voids, and large openings require a fire-resistant backing plate before sealing. Firestopping materials include fire-rated boards, firestop packs, firestop mastic, or fire-resistant mineral wool, with packing thickness typically not less than 24 cm and gaps around cables limited to 1 cm² . Cover plates should be square, evenly painted, and properly dimensioned to close the opening securely .

Installation Sequence

The recommended installation process generally follows these steps :

1. Reserve openings in walls or slabs for cable trays.
2. Install busways or cable trays.
3. Position and install distribution boxes.
4. Install conduits and route cables.
5. Ensure proper grounding.
6. Apply waterproofing where required.
7. Complete firestopping with appropriate materials. At slab penetrations, a waterstop of at least 50 mm is recommended at floor level, and 20–30 mm of firestopping should be applied with a fire-support plate at the top .

Material Considerations

• Intumescent caulks (e.g., IC 15WB) expand under heat to seal gaps and contain fire and smoke .
• Moldable putty and elastomeric sheets bonded to steel or reinforced with wire mesh can be used for retrofits or new installations .
• Mineral wool with fire-retardant coatings is commonly used in European systems, tested according to EN 1366-3 and classified under EN 13501-2 .

Standards and Compliance

• In the U.S., firestopping and cable tray installations often follow UL-listed systems and NEMA guidelines .
• In Europe, cable penetration seals are tested and classified according to EN 1366-3 (fire resistance) and EN 13501-2 (reaction to fire), with performance depending on cable type, configuration, and installation method .
• Compliance includes proper CE marking for European products and adherence to national electrical codes .

Key Considerations

• Ensure all gaps inside and around metal trunking are sealed both internally and externally.
• Maintain reasonable layout and positioning to facilitate installation and future maintenance.
• Use fire-support plates and waterstops at slab penetrations to enhance fire and water resistance.
• Verify that the selected firestop system is tested for the specific cable types and configurations used in the installation . By following these regulations and standards, cable tray through-wall sleeves can achieve fire safety compliance, structural integrity, and maintainability in both new construction and retrofit projects.