In February 2025, sales of our new system based on Multi units have been launched. Phase two follows the ‘DHW Multi+’ system introduced in 2022 as a compact solution for heating, cooling, but also domestic hot water (DHW), targeting households or accommodation capacities for 2 to 3 people.
The newly released system expands this offer to support households of up to 4 members, with output capacities of 6.8 kW and 9 kW. It allows connections up to four indoor units (air-to-air) and a DHW tank with a capacities of 180 or 230 liters. Together with the system from the first phase with (5.2 kW, up to three indoor units and 90 l and 120 l DHW tank), we can offer customers a wide portfolio of Multi+ products allowing them to select configurations tailored to their specific needs.
The key improvement compared with the original product is the efficiency in the domestic hot water heating. The main structural changes to the outdoor unit are a new four-way valve assembly, a shut-off valve assembly (including their cover), a control unit assembly, a fan motor, more powerful compressor and, in the case of the 9kW unit, larger heat exchanger. The new product also adds the possibility of combining FBA ceiling units with output capacities up to 12.5kW.
The development process presented several challenges. After initial performance testing, it was necessary to adjust the capillary tube design (specifically its length) to reduce the amount of refrigerant returning to the compressor before passing through the indoor unit’s heat exchanger during heating operation. Another issue was valve noise mitigation during switching between heating modes. To avoid increasing the product’s cost, the valves were placed outside the outdoor unit. Placing them inside would have required enlarging the unit’s casing, which would mean new parts and tooling. The development team resolved the noise issue by adding sound insulation.
The test plan also had to be revised due to an additional requirement: compatibility of the new outdoor units with the original 90 l and 120 l DHW tanks. Development was carried out in close cooperation with our Belgian colleagues at DENV, who were responsible for the DHW tank development. The project was successfully completed, and the new models entered mass production in February 2025.