New installation concept for Viessmann Vitocal heat pumps – flexible and simplified installation

At ISH 2025, Viessmann Climate Solutions presented a new, simplified installation concept for the Vitocal 250-A and Vitocal 150-A heat pump series.
Four new modular indoor units are now available, allowing any outdoor unit to be combined with any indoor unit from the respective series.

Allendorf (Eder), Germany, December 3, 2025 – At ISH 2025, Viessmann Climate Solutions presented a simplified and highly flexible installation concept for the Vitocal 250-A and Vitocal 150-A heat pump series. The introduction of new modular indoor units (IDUs) significantly simplifies system configuration – each outdoor unit (ODU) is now compatible with every new indoor unit in the respective series. The separation of outdoor and indoor units allows installers to select the exact indoor unit that meets the specific requirements of the heating system, regardless of the selected output of the outdoor unit. This provides maximum flexibility for both new buildings and modernization projects. Viessmann Climate Solutions is part of Carrier Global Corporation (NYSE: CARR), a global leader in intelligent climate and energy solutions.

High flexibility with new indoor units

With a flow temperature of up to 70 °C, the units are ideally suited for modernization projects. Existing radiators can continue to be used without the need for underfloor heating. As a result, the four new indoor units in the Vitocal 250 and Vitocal 150 series meet every requirement.

IDU-A
This wall-mounted indoor unit is particularly suitable for systems with one heating circuit (1C). Good to know: the version with two heating circuits (2C) will remain in the Viessmann portfolio in its current design.

IDU-A Compact
The floor-standing indoor unit with an integrated 190-litre steel domestic hot water cylinder with Ceraprotect enamel coating is designed for systems with one heating circuit. The two-circuit version in the previous design will also remain available.

IDU-A Hybrid
This variant is a hybrid solution for dual-fuel operation with an existing oil or gas boiler. The IDU-A Hybrid can be combined with the Vitocal 250-A Hybrid up to 18.5 kW or the Vitocal 150-A Hybrid up to 14.9 kW.

IDU-A Modular
A cost-effective solution designed for systems with heating water buffer storage tanks and without expansion vessels. This version is particularly recommended for systems with multiple heating circuits and separate buffer tanks, as well as for fresh water systems.

Significantly shorter installation and commissioning times

The new indoor units have been designed to optimise installers’ work processes, significantly reducing installation and commissioning times.

Optimised electrical connection area
An easily accessible electrical connection area in the upper section with lever terminals speeds up wiring.

Swivelling component box
All electronic components are located in a swivelling box, providing easy access to the hydraulics and improved serviceability.

Revised hydraulic interface
The new design eliminates clamp fittings at the hydraulic interface. Connections and valves are directly accessible, reducing installation time.

Improved venting system
Improved ventilation of the indoor unit enhances system efficiency. A new vent valve on the defrost buffer allows air to escape at the highest point, significantly reducing venting time.

Detailed improvements to the outdoor unit

The outdoor units have also received several detailed improvements. Noise emissions of the 10 kW and 13 kW models in noise-reduced operation have been reduced from 54 dB(A) to 53 dB(A). Fan ring heaters (anti-freeze version) are now installed as standard in all outdoor units, eliminating an additional installation step on site.

As usual, the heat pumps can be conveniently and safely controlled and commissioned via the Viessmann One Base platform and the ViGuide mobile app.

Source: viessmann-climatesolutions.com