Heat pumps are our preferred heat source for space or swimming pool heating. The most efficient principal heat source is a heat pump. A heat pump is defined by Dictionary.com as;
“a device that uses a compressible refrigerant to transfer heat from one body, as the ground, air, or water, to another body, as a building, with the process being reversible.”
All heat pumps use the principle of Boyles law – that the temperature and vapour pressure of a substance are directly and proportionately related at a constant volume. The basics of how a heat pump works can be seen here:
This is the technology behind air conditioning units (known as Direct Expansion systems), where the refrigerant acts directly as the heat transfer agent with the air, as well as the heat pump/chiller units, that use a hydronic system, whereby the refrigerant heats or cools water which is the medium used for heat transfer; be it for a swimming pool or for space heating/cooling through underfloor pipes, radiators or fan coils.
Heat pumps are more expensive to buy initially than alternative heat sources, but the cost is amortised quickly through reduced energy bills. With the moderate temperature that we enjoy in this area, an air source heat pump is efficient and effective and cheap to install (compared to a geothermal or “ground source” heat pump).
Heat pumps are available for both high and low temperature installations. Heat pumps for swimming pools are low temperature and are dealt with here. For space heating we need to consider whether water temperature needs to be low temperature, for heating through underfloor heating, low temperature radiators or fan-coils, or high temperature heat pumps through standard radiators.