Air source heat pump

Outdoor air source heat pump

The air source heat pump draws heat from the outdoor air and transfers it to the water-based heating system of the house. The heat pump is also used for the domestic hot water. Illustration: Bo Reinerdahl

The outdoor air source heat pump draws heat from the outdoor air by means of a fan that blows the air over the heat pump evaporator. The outdoor air heat pump is connected to a water-based heating system and to the domestic hot water system. This pump delivers a decreasing amount of heat with decreasing outdoor temperature and requires make-up heat at outdoor temperatures of 0°C or below.

Comfort heat pump/air-air heat pump


The air-air heat pump draws heat from the outdoor air. The indoor part of the pump is located centrally in the house to enable the warm air to be distributed appropriately. Illustration: Bo Reinerdahl

The comfort heat pump/air-air heat pump is a form of outdoor air source heat pump that uses air as the heat carrier. A house of open-plan design is best suited for the installation of an air-air heat pump, since it is based on the heated air needing to circulate. This type of heat pump also delivers less heat as the temperature drops and it requires make-up heat at temperatures of 0°C and below.

The outdoor part of the air-air heat pump includes a fan that may give rise to disturbing sound. If the sound is perceived as disturbing, this may be due to the sound intensity measured in dB and to the nature of the sound. You can often find out the sound intensity emitted by the fan, but it is still best to ask the installation contractor/distributor to be allowed to listen to the heat pump before buying it. Also bear in mind the location of the outdoor part. Don’t locate it under a bedroom window or close to the neighbour’s bedroom window or close to a veranda, patio, etc. It may otherwise cause a nuisance both to you and to your neighbours.

Exhaust air heat pump

Fresh air is drawn in through registers and leakages in the building. Polluted room air is extracted by means of an exhaust air fan, located in the attic in the above illustration. Illustration: Bo Reinerdahl 

The exhaust air heat pump draws heat from the ventilation system exhaust air, and this type of heat pump needs the house to be equipped with a controlled ventilation system. The exhaust air heat pump can be connected to the heating system and/or can be used for the hot water system.

Read more about exhaust air heat pumps.