Heat pump – simple principle, great effect

A heat pump works in a similar way to a fridge – simply the other way round.

In a fridge, heat is transferred from the inside to the outside. With a heat pump, this happens exactly the other way round. Energy from the air or the ground is transferred into the living space via the heating system.

Refrigerant vapour is compressed to raise its temperature, that is high enough to provide DHW and central heating. Through this process, the Vitocal 350-G reaches up to 72 °C; the Vitocal 300-A and Vitocal 350-A up to 65 °C. These heat pumps can therefore also be used for modernisation as they can deliver a sufficiently high flow temperature for central heating with radiators.

Heat pumps – highly efficient scroll compressor

Viessmann heat pumps – highly efficient scroll compressor

The compression process is critical for the efficiency of a heat pump. For this, Viessmann uses a Compliant scroll compressor. It is characterised by quiet operation, low vibrations, low maintenance and an extremely long service life.

To generate heat, for example, energy is drawn from the ambient air and used to evaporate a refrigerant that boils at low temperatures. The gas thereby created is compressed by the scroll compressor, which causes it to heat up. The gas heated in this way transfers its heat via the condenser to the heating water or DHW heating system, and reverts to a liquid state. Finally, the refrigerant, which is still under pressure, is expanded in an expansion valve, and the cycle begins again.


Energy sources for heat pumps

The best energy source for each individual case depends on local conditions and the actual heat demand. Viessmann heat pumps can use various energy sources:

  • Air – practically unlimited availability; lowest investment costs
  • Ground – via geothermal collector, geothermal probe or ice store; very efficient
  • Water – extremely efficient; observe water quality
  • Waste heat – subject to availability, volume and temperature level of the waste heat
Heat pump for utilising energy from the ground (collector)

Ground source energy (collector)

[1] Vitocal brine/water heat pump
[2] DHW cylinder
[3] Heating water buffer cylinder

Heat pump for utilising energy from the ground (probe)

Ground source energy (probe)

[1] Vitocal brine/water heat pump
[2] DHW cylinder
[3] Heating water buffer cylinder

Heat pump for utilising energy from the ground, the air and the sun (ice store)

Energy from the ground, the air and the sun (ice store)

[1] Vitocal brine/water heat pump
[2] Ice store
[3] Solar/air absorber

Heat pump for utilising energy from the air

Air source energy

[1] Vitocal air/water heat pump
[2] DHW cylinder
[3] Heating water buffer cylinder

Heat pump for utilising energy from groundwater

Ground source energy (groundwater)

[1] Vitocal water/water heat pump
[2] DHW cylinder
[3] Heating water buffer cylinder

Seasonal performance factor

The coefficient of performance (COP) is the ratio of heat transfer to power consumption. The seasonal performance factor is the average of all COPs occurring in a year.

The coefficient of performance is used to compare heat pumps with regard to efficiency, yet it is derived from a particular operating point under defined temperature conditions.

When planning a system, it is necessary to consider its operation over the whole year. For this, the heat volume transferred over the year is given in relation to the overall electrical power drawn by the heat pump system over the same period. This includes the power drawn by pumps and control units, etc. The result is given as the seasonal performance factor.