Another Heat Pump Alternative
Air-to-water heat pumps have some advantages over air-to-air units or split-system heat pumps. Like other heat pumps these take heat out of the air, but they put it into a water-antifreeze mixture which is then pumped through the house. The heat from the water can be distributed by a radiant floor system, through low-temperature radiators or through fan-coil blowers. The system can be reversed to take heat from the water and cool the house.
An air-to-water heat pump system will contain a buffer tank to store heated or cooled water, so it smoothly reacts to loads. The system can also be connected to a coil in the domestic water heater or in a pre-heat storage unit to reduce the costs of electric water heating.
These systems are a miniature version of larger systems used in commercial buildings and commonly known as “chillers”. The unit sits outside and the refrigerant is all contained within the unit, so the only connections are for electricity and a fluid supply and return line—there is no piping of refrigerant.
Air-to water heat pumps operate quite efficiently. They are least efficient during the coldest weather, but the coldest weather makes up a small part of the heating season. Operating at relatively low water temperatures increases their efficiency, and the lower temperatures are ideal for heated floors.
As regulations move us towards net-zero houses this alternative may become more widely accepted since natural gas is not renewable cannot be generated on site like electricity can.