Air source heat pumps – air as a heat source

How the air source heat pump works

How the heat pump generates thermal energy with air can be described using the example of a refrigerator. While the refrigerator channels the warm air to the outside, the air source heat pump brings the heat from the ambient air into the room. More specifically, a fan actively draws in the ambient air and transfers it to an air heat exchanger (evaporator) built into the heat pump. Within that is a circulating refrigerant, which changes its physical state at low temperature and evaporates. To raise this refrigerant vapour to a level that can be used for heating and domestic hot water heating, it is compressed with the help of a compressor. A detailed description of this process can be found in the section on how the air source heat pump works.

Air source heat pumps are among the most commonly used heat pumps. This is not only due to their relatively low investment costs, but to their divergent installation options as well.

In the monoblock version, all components used for heat generation are located within the heat pump. As the connection pipes between the indoor and outdoor units are only filled with water, these units can be put into operation quickly and easily. The contractor carrying out the work does not need to have a refrigerant certificate to do this work. And, as most appliances operate very quietly, they can be positioned close to the living room.

Since older buildings differ greatly depending on their age and history, varying types and amounts of work are required. In order to sensibly accommodate and operate a new heating system in an older building, the premises, flue system, chimney and thermal insulation may need to be updated as well. Exact details can only be provided by a heating installer after a thorough inspection.

Vitocal 222-S: Air source heat pump with one outdoor unit

Benefits of an air source heat pump

The benefits of an air source heat pump differ depending on perspective. In order to better classify these pumps, it is helpful to differentiate between their basic and more specific benefits.

The basic benefits of an air source heat pump include first and foremost the cost-free and, from a human perspective, infinite heat source. Using this energy source makes system owners a little less dependent on their previous fuel providers. This is because, unlike fuel oil or natural gas, ambient air is not subject to economic or political fluctuations. In addition, the costs for chimneys and flue gas inspectors will become a thing of the past. When homeowners decide to operate an air source heat pump, they can count on high operational reliability and an increase in the value of their property. Other economic benefits of an air source heat pump are the attractive subsidies from the state, the fulfilment of all EnEV requirements for new buildings and renovated older buildings, and low-maintenance operation. You can find out more about financial support from the state in the section on financing an air source heat pump.

The following list provides an overview of the benefits of an air source heat pump:  

  • Free heat source available at any time of day
  • Relatively low investment costs
  • Expandable thanks to cascade function
  • No official approval needed
  • Suitable for both new build and modernisation projects
  • Retrofitting is possible

By operating an air source heat pump, system owners not only keep heating costs at a low level in the long term. They also noticeably reduce the environmental impact of CO₂ emissions. If homeowners also choose to purchase heat pump electricity from ecological resources, the system can operate fully CO₂ neutral.

The protection of the environment is also important at the climate policy level. Many experts believe that the energy transition can be achieved with the help of heat pumps. Keyword: Sector coupling, i.e. the intelligent merging of the electricity and heating markets. After all, even today, green power plants still need to be shut down from time to time in order not to endanger grid stability. Heat pumps can capture this surplus power, store it thermally and then use it to supply heat all year round.

Benefits over other heat pumps

In addition to the ambient air, the ground and groundwater also provide thermal energy from which heat pumps can generate heating energy. When homeowners are faced with a purchase decision, they should not ignore the benefits of the air source heat pump over other types of heat pump. These are quite numerous.

When compared to brine or water/water heat pumps, the investment costs for an air source heat pump are relatively low. One of the reasons for this is the way in which the heat source is exploited. Unlike a brine/water heat pump, neither excavation of the ground nor deep drilling is required. Instead, the outdoor unit of an air source heat pump is flexible in its installation. It can be placed on a base or on a wall mounting and extracts heat from the outdoor air. It has a footprint of around one square metre, depending on the model.

The planning effort for an air source heat pump is low, as only the suitable heating output and noise protection need to be taken into account. An official permit is not needed, unlike with a brine or water/water heat pump. The sound calculator can help in assessing sound propagation.

Modern air source heat pumps from Viessmann operate very quietly and are barely audible during operation. Achieving this has taken years of intensive research and development work. Viessmann heat pumps feature Advanced Acoustic Design, where all heat pump components have been designed to minimise noise. Low frequency noises that are perceived as particularly annoying have been minimised.

Another advantage of the air source heat pump is its simple installation. Depending on the model, it can be set up either completely indoors or outdoors. Where space is limited, the split version is an optimal solution. Here, the appliance is divided into an indoor and outdoor unit, with the majority of the components such as the fan, the evaporator and the compressor located in the outdoor unit. The indoor unit contains only the condenser and the hydraulic components as well as the control unit. Thanks to their straightforward installation, air source heat pumps are ideal for modernisation projects.

Vitocal 300-A: the outdoor unit of a heat pump

Local authority and commercial use also possible

In addition to its environmental responsibility, one of the benefits of an air source heat pump is that it is quick and easy to use, especially in the local authority and commercial sector. For the local authorities sector, for example, the Vitocal 300-A offers a rated heating output of up to 47.2 kilowatts. It was designed to be sound-optimised. In a cascade of 5, it achieves an output of up to 236 kilowatts.

Product range: Air source heat pumps

The Vitocal 250-A and 252-A air source heat pumps are particularly suitable for modernisation projects, the Vitocal 200-A air source heat pump for new build projects. Compared to a brine/water system, the investment in an air source heat pump is lower, as the costs for installing a geothermal collector or drilling holes for geothermal probes are not incurred. The heat pumps can be installed indoors and outdoors. Outdoor installation is a particularly space efficient solution. Only the control unit is mounted on the wall in the house.

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