How to seal the cable tray entering the low-voltage wiring shaft

Effective sealing of cable trays in low voltage wiring shafts can be achieved using modular cable entry seals, firestop packs, and heat-shrinkable or rubber-based sealing systems that provide airtight, watertight, and fire-resistant protection.

Firestop and Shaft Sealing

For electrical shafts, firestopping is essential where cable trays pass through walls, slabs, or enter panels. Openings should be tightly sealed with fire-rated materials such as firestop packs, firestop mastic, mineral wool, or fire-rated boards. Large openings may require a fire-resistant backing plate before sealing.

Gaps around cables or metal trunking should be minimal (less than 1 cm²) and packing thickness should meet design requirements, typically not less than 24 cm. Cover plates should be square, evenly painted, and properly installed to ensure a reliable seal.

Modular Cable Entry Seals

Modular cable entry systems are highly effective for high-density cable applications. Products like Roxtec entry seals use rubber modules with removable layers to fit multiple cable sizes, allowing for future expansion without creating new openings. These systems replace multiple conventional cable glands, save installation time, and maintain airtight and watertight integrity.

Similarly, CSD Sealing Systems offer modular solutions such as SLIPSIL plugs, RISE® inserts, and NOFIRNO® systems, which provide fire, water, and gas protection for single or multiple cable penetrations.

Heat-

Shrinkable and Mechanical SealsFor panel or bulkhead entries, heat-shrinkable cable entry seals (CES) provide long-term watertight and fume-tight protection. These seals are made from flame-retardant polyolefin with hot-melt adhesive and can accommodate multiple cables. Mechanical modular seals also allow for neat cable routing and future expansion while maintaining airtight and watertight performance.

Best Practices

Plan for expansion: Use modular systems that allow additional cables without new penetrations. Ensure fire compliance: Select fire-rated materials and follow installation sequences for firestop packs. Maintain tight seals: Avoid visible cracks or voids; ensure all gaps around cables and trays are sealed.

Use waterstop measures: For floor-level or slab penetrations, provide waterstop heights of 20–50 mm to prevent ingress. Facilitate maintenance: Layout and positioning should allow easy access for future cable additions or inspections. By combining firestop materials, modular entry seals, and heat-shrinkable or rubber-based systems, low voltage cable trays in wiring shafts can be effectively sealed to meet safety, environmental, and regulatory requirements.