Ventilation junction box gbc Boligflex Plus BFP KVB 2x75 Ø125 for duct connections

The gbc Boligflex Plus BFP KVB 2x75 Ø125 ventilation junction box is a compact metal and plastic unit for splitting and routing air from a single Ø125 mm main outlet into two Ø75 mm branch ducts. Designed for residential and light commercial ventilation systems, this junction box supports integration with flexible ducts and common fittings, providing a neat and space-saving branching point for supply or extract air. The construct combines the rigidity of metal with the adaptability of plastic components to simplify installation and maintain airflow balance in small-scale HVAC layouts.

Advantages

This junction box offers a compact footprint and a durable mixed-material construction that resists deformation while allowing easy connection to flexible ducts. Its two-branch design ensures reliable airflow distribution without complex assembly, and compatibility with standard Ø75 mm and Ø125 mm ductwork reduces the need for additional adaptors. The product is intended to streamline ductwork routing and minimise on-site modifications during ventilation installation or refurbishment.

Suitable for

• Branching a single Ø125 mm ventilation main into two Ø75 mm flexible ducts
• Domestic ventilation systems in apartments and houses
• Light commercial ventilation installations where compact distribution is required
• Retrofitting or extending existing ductwork with flexible hoses

Key specifications

• Main outlet diameter: Ø125 mm
• Two branch outlet diameters: Ø75 mm each
• Mixed metal and plastic construction for strength and ease of connection
• Compact rectangular junction box form factor suitable for confined spaces
• Designed for use with flexible ducts and standard ventilation fittings

How to use

Install the junction box at the point where the main Ø125 mm duct feeds the two Ø75 mm branches. Secure the box to a structural element if necessary, then attach the Ø125 mm main duct to the designated outlet using appropriate clamps or duct tape, ensuring an airtight connection. Fit the two Ø75 mm flexible ducts onto the branch outlets and fasten them with suitable clamps. Check alignment and support for the connected ducts to avoid strain on the box and to maintain consistent airflow. Perform a leak and airflow test after installation to confirm correct sealing and distribution.

Usage recommendations

Use corrosion-resistant clamps and sealants suitable for HVAC applications to ensure long-term airtightness. Avoid over-bending flexible ducts near the connection points to prevent airflow restriction. If installing in a moisture-prone area, verify that surrounding materials and fasteners are compatible with both metal and plastic components.