Why an air-water heat pump ?
Air-water heat pumps in compare to ground-water heat pumps have negatives and positives.
The biggest negative of heat pumps which use air as a source of heat is the fact that whenever the temperatures are the lowest, and therefore the heat consumption is highest, the heat pumps gives less power (the heat needs to be pumped from the lowest temperature potential which is a physical principle regardless of some manufacturers claims that their heat pump has the same power in all outdoor temperatures). Another disadvantge to ground-water or water-water heat pump is the fact that heat needs to be transferred in particular intervals for defrosting the vaporizer which in contact with wet outdoor air freezes. Because of these facts, the average COP for the time of heating is a bit lower than in ground - water heat pumps. Another disadvantage of outdoor heat pumps is also the presence of a source of noise in the outdoor environment, which however can be limited by appropriate precautions.
Undisputed advantage of air-water heat pumps is the cost of the whole installation. The heat pumps itself are usually more expensive because of more difficult manufacturing, but the savings on the primary side are incomparable (bore hole or ground surface collector doesn't need to be purchased). In addition to that, today the compressors are having better and better quality, and therefore every year air-water heat pumps are used more and more in compare to others.
