The heat pump as a replacement for an air conditioner
A heating system is installed in almost every home, while just a few structures in Germany have an air conditioning system. However, it is not uncommon for your own home to become excessively hot in the summer. Is buying an air conditioner for a few hot summer days worth it? Almost never. Especially since air conditioners that run solely on energy are frequently pricey. A heat pump, on the other hand, can provide both heating and cooling in one system. This is because heat pumps can both heat and cool, and they run on mostly ambient heat and very little electricity.
How cooling with heat pumps works
Heat pumps can provide both active and passive cooling. In active cooling, the heat pump’s compressor is still used. The heat pump is basically in normal operation, with the only difference being that its operating direction is reversed to cool instead of heat.
Passive cooling, on the other hand, bypasses the compressor. This method can only be used with geothermal or brine-to-water heat pumps, since the ground maintains temperatures of 10 degrees even in summer. The outside air, which is the heat source of air-source heat pumps, is too warm in summer for cooling purposes.
With the help of a heat exchanger, passive cooling automatically removes the excess heat in the house to the now cooler ground probes. This is made possible by a simple valve that bypasses the heat pump and allows the heat to flow naturally from the hot to the cold. One disadvantage of passive cooling is that the cooling effect is slow to occur. Also, the system has a lower intensity than active cooling.
The principle of active cooling in an air-water heat pump
Air-to-water heat pumps extract their heat from the outside air. If the unit is to cool instead of heat, the heat must be extracted from the indoor air rather than the outdoor air. Unlike passive cooling, the compressor remains in operation. In principle, therefore, there is only a change in direction, and the heat pump’s mode of operation remains the same.
To enable the change of direction in the heat pump process, both a 4-way valve and a second expansion valve must be integrated in the refrigerant circuit. The 4-way valve switches the flow direction. In addition, the valve enables independent heating and cooling. This is because, although heat generation for space heating is unnecessary in summer, domestic hot water must still be heated.
Which radiators are ideal?
If you want to cool your house with a heat pump, you are tied to a hot water heating system, unlike conventional air conditioners and fans. However, classic radiators for hot water heating systems, so-called radiators, are unsuitable for cooling with heat pumps. Here, only a very limited transfer of cool room air is possible and there is an increased risk of condensation.
In contrast, underfloor heating/cooling, wall panel heating/cooling or fan heating/cooling are suitable. In the case of fan coils, care should be taken to design them for higher cold and lower hot water temperatures.
If you want to cool with underfloor heating, there is often a fear of getting cold feet. However, this fear is unfounded, because even in cooling mode, the floor temperature remains above 20 degrees. The advantage is that, unlike fan coils, there is no draft or noise, and the heater is not further noticeable in the room. Wall surface cooling is even more efficient than cooling with underfloor heating, as the occupants come into greater contact with the radiation from the cooling surfaces.
If room air is cooled, there is always a risk of dew formation. This is because, for example, if the floor heating reaches a temperature below the dew point, there is a risk of water condensing on the floor surface. Therefore, the dew point should be continuously monitored by the heat pump control.