Fireproof putty on top of cable tray in electrical well

Fireproof putty can be used to seal cable tray penetrations in electrical wells, but it must be applied according to firestop system guidelines to ensure compliance and effectiveness.Purpose and SuitabilityFireproof putty, such as 3M Fire Barrier Moldable Putty+ or Firebreak 55, is designed to maintain the fire resistance of walls, floors, and cable penetrations by forming a dense char under fire conditions, which blocks the passage of smoke and flames . These materials are non-setting or moldable, allowing for future cable modifications without compromising the fire seal . They are suitable for small to medium cable penetrations and can be applied over cable trays in electrical wells, provided the installation follows manufacturer and code requirements.Installation GuidelinesSurface Preparation: Ensure the cable tray and surrounding surfaces are clean, dry, and free of debris. For large openings, a fire-resistant backing plate or mineral wool may be required before applying putty .Application: Mold the putty around the cables or over the tray to completely fill gaps and voids, leaving no visible cracks. The thickness and coverage should meet the fire rating specified for the wall or floor penetration .Mechanical Considerations: Some firestop systems, like FIRSTO, allow modular installation around cable trays and can withstand mechanical loads while maintaining fire protection . Ensure the putty does not interfere with cable support or tray integrity.Compliance: Follow local fire codes and standards for electrical shafts, including UL or EN firestop ratings. The putty must be compatible with the tray material (steel, galvanized, or aluminum) and the type of cables installed .Maintenance and ModificationsOne advantage of non-setting putty is reusability. Cables can be added or removed without dismantling the entire firestop, and the putty can be reshaped to maintain the fire seal . Regular inspections are recommended to ensure the putty remains intact and that no gaps have formed due to cable movement or vibration.Key ConsiderationsDo not rely solely on putty for large openings; combine with fire-resistant boards or mineral wool if necessary .Ensure proper thickness and coverage to achieve the rated fire resistance.Maintain clear documentation of the firestop system used for compliance and future maintenance. Using fireproof putty correctly on cable trays in electrical wells provides an effective, flexible, and code-compliant method to prevent fire and smoke spread while allowing for future cable modifications.