What is a heat pump?

A heat pump utilizes energy in the ground or air to heat a building. Heat pumps are currently both an economically and an environ–mentally viable alternative to conventional heating methods such as oil and gas.

A heat pump is a heating system that absorbs heat energy from a low temperature heat source (ground or air). Via a closed-circuit system with a refrigerant and a compressor, the heat is converted to a higher temperature level, which can be used for heating purposes. The process is the same as in a refrigerator, but instead of removing the energy away from the refrigerator, the energy is now led into a building.

The heat pump operates using electricity, but the heat pump uses only 1/3 or 1/4 of the electricity that would otherwise have been used, if the building was heated by electricity alone.

Ground source heat pump

A ground source heat pump consists of water tubes (ground collectors) that are buried in the ground and a heat pump placed indoors. When the sun shines, the ground absorbs heat, and a lot of energy is stored in the topsoil. This energy is drawn out of the ground through the water tubes and transported via a frost proof fluid into the heat pump. The heat pump converts the energy to a high enough temperature to suit the building's radiators and water taps.

The type of soil that the water tubes are placed in is important for the efficiency of the heat pumps, because energy is released by the moisture and the water currents in the soil. Very sandy soil is therefore not as efficient as more clayey soil.

Air to water heat pump

An air to water heat pump utilizes heat in the outside air to produce heat and hot water for the building and can function as the sole heat source. The heat pump consists of an outdoor unit and an indoor unit. The outdoor unit has a large fan that draws air through the heat pump. The indoor unit transfers the heat to the heating system, which leads the heat into the building's heating distribution system, radiators and water taps.

Be attentive when considering the location of the outdoor unit, as it can be noisy especially when defrosting. The noise is usually not audible inside the building, if the doors and windows are closed, but avoid placing it under e.g. a bedroom window or on the patio, where it can be bothersome in the summer. In order not to annoy any neighbours, the outdoor unit ought to be placed 5-10 meters from the properties’ boundaries, but remember to check whether the boundary noise limits are respected.

Air to air heat pump

An air to air heat pump utilizes the energy in the outdoor air to provide heat to the building as hot air. It is an environmentally friendly alternative, especially to electric heating. Air to air heat pumps furthermore have different ways of filtering and defrosting the air, whereby viruses, moisture, mould and other allergens are removed in an efficient way.

Air to air heat pumps usually consist of an outdoor unit, which is mounted on the building's outer wall, and an indoor unit, which is mounted on an internal wall in the building. Because the air to air heat pump delivers the heat as hot air, it will usually only be able to heat the room where the indoor unit is placed. It can, however, also serve as supplement heating in other adjoining rooms, if the heat can be distributed through open doors or the like. An air to air heat pump cannot make hot water.

If you are considering an air-air heat pump, be aware of the noise from both the indoor and outdoor unit.

Air-water heat pump for church.
Photo: Carsten Vejborg

Luft-vand vandpumpe