Fire cable tray connection

Fire cable tray connections require proper firestopping, UL-rated materials, and secure mechanical splices to prevent fire propagation and maintain electrical safety.

Firestopping Principles

When cable trays pass through walls, slabs, or electrical shafts, all openings must be tightly sealed with fire-resistant materials to prevent fire and smoke spread. This includes using firestop packs, mineral wool, fire-rated boards, or intumescent caulks. Gaps around cables should not exceed 1 cm², and packing thickness should meet design requirements, typically at least 24 cm for large openings.

Cover plates should be square, evenly painted, and fully close the penetration to maintain integrity.

Materials and Products

Firestop pillows and putty: Medium self-locking pillows (e.g., 3M FSP-SLP-M) and moldable putty (FSP-MPS) are used to fill gaps around trays, conforming to the opening shape and adhering to surfaces. Intumescent caulks: Products like IC 15WB expand under heat to seal gaps and protect cables from fire. Fire protection coatings and tapes: FLAMMOTECT-A and DG-CR 0.

7 provide a protective shield around cables and trays, preventing flame propagation and maintaining functionality during fire.

Mechanical Connections

Cable trays must be securely connected using splice plates and hardware. For example, “CT” type trays use pair splice plates with zinc-plated hardware, while aluminum trays may require drilled holes for field splices. Proper mechanical connections ensure structural integrity and prevent deformation under load.

Installation Sequence

Complete floor and wall finishes in the electrical shaft. Install busways, distribution boxes, and conduits. Route cables and secure grounding.

Apply firestopping materials around tray penetrations. Ensure all gaps are sealed internally and externally, with cover plates installed.

Compliance and Ratings

Use UL-listed systems for walls and slabs, such as C-AJ-4056 for concrete (3 HR F-rating) or W-L-4037 for gypsum (1–2 HR F-rating). Ensure tray openings are sized appropriately, typically 1. 5 inches larger than the tray on all sides, to accommodate firestop materials.

Summary

A proper fire cable tray connection combines mechanical integrity, firestopping, and UL-rated materials. Using firestop pillows, putty, intumescent caulks, and protective coatings ensures that cable trays remain functional and safe during a fire, while secure splice plates maintain structural stability. Following the correct installation sequence and adhering to fire ratings is essential for compliance and safety.