flexoTHERM

flexoTHERM is Vaillant’s indoor multi-source heat pump. The heat-pump unit uses a brine circuit and can take energy from a ground loop, groundwater heat exchanger or outdoor air collector.

Source modules define the installation type

A direct ground loop makes flexoTHERM a ground-source system. Adding fluoCOLLECT provides the intermediate heat exchanger for a water-source installation. Adding aroCOLLECT provides an outdoor air-to-brine collector, making the complete arrangement an air-source system even though the compressor remains indoors.

The source module is therefore part of the product definition and certification record. flexoTHERM 8 kW does not establish whether the project is ground, water or air source.

Output and electrical schedules

Current UK professional pages list 230 V models in 5, 8 and 11 kW classes and 400 V models in 5, 8, 11, 15 and 19 kW classes. Codes use VWF 58/4 to 118/4 for the 230 V schedule and VWF 57/4 to 197/4 for 400 V.

The indoor enclosure is approximately 1183 × 595 × 600 mm. It does not contain domestic-hot-water storage, so a compatible cylinder is added where hot water is required.

Certification and guarantee record

On 23 July 2026, the MCS Product Directory listed current ground-source, water-source and aroCOLLECT air-source flexoTHERM combinations under the applicable VWF codes. Their displayed certification periods ended on 23 April 2027. The complete heat-pump code and source module identify the certified combination.

Vaillant’s current homeowner page states a two-year standard guarantee with a route up to seven years, subject to eligible installation, registration and cylinder conditions. The written certificate establishes the term for a specific system.

Related entries

• Vaillant
• flexoCOMPACT
• uniSTOR heat-pump cylinder
• Ground-source heat pumps
• Open-loop ground-source heat pumps