How R290 Air-to-Water Heat Pumps Adapt to Heating, Cooling and DHW Applications

For an air-to-water heat pump, selecting the right capacity is only the first step. The more important question is how the system will actually be used: space heating, cooling, domestic hot water, or a combination with existing boilers, solar energy and multiple hydronic terminals.

This is particularly important for residential renovation and heating-replacement projects. A new heat pump does not always need to replace every existing component. In many cases, the most practical solution is to let the heat pump operate as the primary energy source while existing equipment remains available for peak-load support.

1. Start with the Application, Not Just the Heat Pump

The same R290 air-to-water heat pump platform can serve very different building requirements. The system configuration should therefore be selected according to the actual application.

Integrated R290 hydronic system with domestic hot water, buffer tank, radiators, floor heating and fan coil terminals.

2. R290 Monobloc Platform and System Configurations

The YUJU R290 air-to-water heat pump platform uses a monobloc outdoor unit and can be configured with different hydraulic components according to the project.

The main product range shown in the current technical data covers 8, 10, 12, 14 and 16 kW. The 8, 10 and 12 kW models are available with 220–240V single-phase or 380–415V three-phase power supplies, while the 14 and 16 kW configurations shown are three-phase.

A hydraulic module, also referred to as a Hydrobox configuration in system applications, can be used to organize hydraulic connections, controls and auxiliary components. It should be understood as a system configuration rather than a separate heat-pump refrigeration platform.

3. Heating Applications: From New Homes to Boiler Replacement

Heating is one of the most important applications for an air-to-water heat pump. The system can supply hot water to underfloor heating, radiators and other hydronic terminals.

New Residential Heating

For new homes, underfloor heating is particularly suitable for heat-pump operation because the system can normally achieve the required indoor comfort with relatively low water temperatures. Lower water temperature means a smaller temperature lift between the outdoor air and the heating water, which generally supports higher heat-pump efficiency.

Replacing a Gas or Oil Boiler

Boiler replacement is different from new construction. Existing homes may already have radiators, pipework and a domestic hot-water system designed around a combustion boiler.

The advantage of an R290 heat pump is that it can transfer heat from outdoor air rather than generate all heating energy through fuel combustion. When the local electricity and gas prices, building load and system design are favorable, this can significantly reduce energy consumption and operating costs.

The key is not simply to remove the boiler. The existing hydronic system should first be evaluated for required water temperature, radiator capacity, building heat loss and actual winter operating conditions.

4. Hybrid Heating: Heat Pump Priority with Boiler Peak-Load Support

For colder climates, a hybrid system can provide a more practical solution than forcing one heat source to cover every extreme operating condition.

The recommended operating principle is:

This approach avoids treating the boiler as the main heating source. Instead, the heat pump handles normal heating loads while the boiler is available when the building requires additional heat during extreme outdoor conditions.

Boiler-assisted configuration in which the boiler provides auxiliary heat for domestic hot water.

Boiler-assisted configuration for hydronic indoor heating.

Combined boiler configuration serving both domestic hot water and indoor heating.

5. Cooling Applications: One Hydronic Platform for Year-Round Use

An air-to-water heat pump does not have to be used only for winter heating. A reversible system can provide hydronic cooling during summer and heating during winter.

Cooling water can be supplied to fan coil units or other suitable hydronic terminals. The technical reference range shows cooling water temperatures of approximately 5–25°C, with actual operating conditions depending on the terminal type and system design.

This makes the same equipment platform useful for homes that require:

• Winter space heating
• Summer hydronic cooling
• Domestic hot water
• Multi-zone temperature control

6. Domestic Hot Water and Solar-Assisted Heating

Domestic hot water can be integrated into the same hydronic system through a dedicated DHW storage tank. For projects with solar thermal energy, the solar system can also be connected to the DHW tank as an additional heat source.

The heat pump can then provide hot water when the solar contribution is insufficient, while solar energy can reduce the amount of electricity required for water heating when suitable solar energy is available.

Solar-assisted domestic hot water configuration with solar collector, storage tank and heat-pump support.

7. Operating Temperature Range

Operating temperature is one of the most important parameters when selecting an air-to-water heat pump. The required outdoor temperature and water temperature should always be evaluated together.

The -30°C operating point should not be presented as a currently mass-produced standard capability. The ultra-low-temperature version is under development, while the -20°C model has completed testing and production.

8. Representative Heating and Cooling Performance

The technical data show that the R290 platform can maintain strong efficiency across different water-temperature conditions. The following values are representative of the 12 kW configuration under the specified test conditions.

Under the referenced EN 14825 seasonal conditions, the 12 kW configuration shows a SCOP of approximately 5.08 at W35 with seasonal efficiency ηs of approximately 200%, and a SCOP of approximately 4.00 at W55 with ηs of approximately 157%.

These values demonstrate an important principle in heat-pump design: higher water temperature generally increases the temperature lift and reduces instantaneous COP. Therefore, using the lowest practical water temperature for the selected heating terminal can improve seasonal energy performance.

9. Choosing the Right Application Strategy

The best R290 heat-pump system is not determined by the heat-pump capacity alone. The building, heating terminal, outdoor design temperature, water temperature and energy sources must be considered together.

10. The Main Advantage Is System Integration

The value of an air-to-water heat pump is not limited to the outdoor unit itself. Its real application flexibility comes from how the heat pump interacts with the building's hydronic system.

One R290 platform can be configured around different combinations of:

• Underfloor heating
• Radiators
• Fan coil units
• Domestic hot water tanks
• Buffer tanks
• Hydraulic modules / Hydrobox configurations
• Existing boilers
• Solar-assisted DHW systems
• Multiple heating zones

For cold-climate applications, the most practical strategy may not be to completely remove the existing boiler. Instead, the heat pump can carry the normal heating load while the boiler remains available as a peak-load heat source when outdoor temperatures or building demand exceed the preferred operating range.

This approach combines the energy-saving potential of heat-pump operation with the reliability of an existing high-temperature heat source, providing a more flexible path for residential heating renovation.

Conclusion

R290 air-to-water heat pumps are increasingly being considered not simply as heating equipment, but as a central component of integrated hydronic energy systems.

For new homes, the system can provide efficient heating, cooling and domestic hot water. For renovation projects, it can work with existing radiators and other hydronic terminals. For colder climates, a heat-pump-priority hybrid system can retain the boiler as peak-load support. Solar-assisted DHW can further reduce the electrical energy required for water heating when solar energy is available.

The correct starting point is therefore the application: what the building needs to heat, cool or supply with hot water, at what outdoor temperature, and at what water temperature. The heat-pump configuration should then be selected around those requirements.