Heat pumps

Solutions from Kermi

x-change dynamic pro AW E air/water heat pump for outdoor installation

How does a heat pump work?

A heat pump basically works in the same way as a refrigerator, just in the other direction. While a refrigerator takes heat away from its contents and emits it externally, the heat pump takes energy from sources such as the ambient air, the ground, or the groundwater and transfers it to the heating system.

In detail, this happens in 3 important steps.

1. Generating heat

Depending on the type of heat pump, energy is generated from the ambient air, the ground, or the groundwater. This process uses either a fan (in the case of air heat pumps), which draws in ambient air, or – in the case of a brine pump – probes or collectors in which the brine circulates and withdraws heat from the environment.

2. Condensing energy

The energy generated is then transferred in the heat pump via a heat exchanger to a second, independent circuit in which – just like a refrigerator – an environmentally friendly coolant is circulating. The coolant vaporises as a result of being heated. The coolant is also compressed in a compressor, causing its temperature to increase significantly. This heat is then drawn out of the coolant again using another heat exchanger, and is transferred to the heating system. The coolant condenses in a process that returns it to the circuit.

3. Distributing & storing heat

The energy that the coolant transmits to the (central) heating system via the second heat exchanger is transferred from this point to radiators, underfloor heating, and so on in the form of heated water, or is stored temporarily in a storage system such as buffer storage or a hot water storage unit.

Ground heat source

Using the ground as a heat source might sound strange at first, but it makes sense when you start looking into it. Energy can be extracted from the ground in two different ways using the option of probes or collectors, depending on the environment and the ground conditions.

Geothermal probes

Geothermal probes are inserted into a drill hole that runs around 100 metres deep in the case of a normal detached house. The ground temperature remains constant throughout the year from a depth of 10 metres downwards, providing ideal conditions for a heat pump.

A frost-proof liquid known as the brine circulates in the heat pump. This brine extracts energy from the ground around the probe and feeds it into a closed circuit into the heat pump.

Geothermal collectors

Geothermal collectors work in a similar way to geothermal probes, except that the collectors are inserted horizontally instead of downwards. At a depth of approx. 1.5 metres, geothermal collectors are laid out in a serpentine shape.

The brine circulates in these pipes – as is the case with geothermal probes – and collects energy from the ground; this is energy that the ground has absorbed from sun irradiation or rain water, for example.

Outside air/groundwater heat source

Aside from the ground, the outside air and even groundwater – where available – are also suitable energy sources for a heat pump.

Outside air

This is a simple principle in which energy is extracted from the outside air with an air heat pump. It even works in the winter when temperatures are below 0 degrees, as long as the boiling point of the coolant is lower than the outside temperature (which is generally the case).

The x-change air/water heat pumps from Kermi, for example, make use of this principle.


In addition to the ground, a heat pump can also extract heat from groundwater. The average temperature of the groundwater is easily enough to operate a heat pump, even on cold days.

Groundwater heat pumps are always an appropriate choice in cases where it is easy to access groundwater and, of course, groundwater is available in sufficient quantities.

What are the benefits of a heat pump?

Low space requirements

Oil or gas tanks, and bunkers for pellets or wood chips, all need plenty of space – something that comes at a premium in old and new buildings alike. In addition to the space requirements, it is important to consider the odours that oil and other sources emit – we are all familiar with the typical smell of a boiler room. With a heat pump, however, none of this is needs to be considered.

Heating and cooling with a single unit

As mentioned previously, a heat pump operating in heating mode works in the same way as a refrigerator, only in reverse. This can be switched around in the summer, of course, allowing the heat pump to operate in cooling mode on hot days – for example, in combination with x–net panel heating and surface cooling.

Virtually no maintenance costs

Heat pumps are extremely easy to maintain and need very little attention. They contain mature technology that has gone the distance, putting them light years ahead of many other heating systems when it comes to durability and maintainability. Heat pumps do not suffer from a gradual loss of performance: whether it is the first day of using them or they have been in operation for 25 years, their output always remains the same.

No emissions, no chimney sweeps

You don’t need a chimney if there are no emissions. And without a chimney, you don’t need an annual visit from a chimney sweep. That’s not just a good thing for the environment – your wallet will thank you too.

Controlling your heat pump intelligently and conveniently

The technology in a heat pump can be controlled with precision. That creates the perfect conditions for intelligent control with smart home applications and apps – delivering not only greater comfort, but also more potential for savings.

Completely independent with solar power

If you operate your heat pump with electricity you have generated yourself (from a solar panel system, for instance) and you use intelligent control, you no longer have to worry about oil, gas, electricity, and wood prices – instead, you’ll be generating electricity at virtually zero cost.

When does it make economical sense to use a heat pump?

The answer is actually quite simple: it always makes sense. Fossil fuels such as oil, gas, and coal do not have a future in private households, particularly in view of the high carbon emissions they produce. With a heat pump, you are investing in a sustainable and future-proof form of heat generation which your wallet will thank you for – apart from low maintenance costs, you will also benefit from attractive subsidies.

What should I pay attention to when selecting a heat pump?

Ultimately, the right heat pump technology is selected on the basis of a wide range of factors, such as the size of the property, the local conditions, the location, and the available budget.

Once the question of which technology is most appropriate has been settled, you need to select the most suitable heat pump model for your project. In this case, factors such as floor space, the type of heat transfer in the house (radiators or panel heating, for example), and even the insulation in the property all play a role.

Questions surrounding these aspects can only be answered in detail on location by an expert. If you are still looking for an experienced expert, use our specialist partner search function to find a Kermi specialist partner near you. They will be delighted to answer any questions you may have and provide assistance in all matters concerning the procurement and installation of a heat pump.

Heat pump advice

x-change dynamic pro AW E air/water heat pump for outdoor installation

Will the heat pump be used for cooling?

Heat pumps are also suitable for cooling

x-change dynamic pro AW E air/water heat pump for outdoor installation

Optimise your own consumption

Reduce electricity costs with the x-change heat pump.

The x-change dynamic water WW I (water/water) heat pump extracts thermal energy from the groundwater using an extraction and absorption well.

Which heat pump is the right one?

The right heat pump for your needs

Sound level and sound insulation

Highly effective sound and vibration absorption

Combine a heat pump with solar panels

x-change dynamic heat pumps with solar panel interface as standard

Product overview

Heat pump product range from Kermi.

Specialist heat pump terminology

Explained simply

Bivalent operation

There is a second heat generator that works either in parallel (bivalent-parallel) or alternately (bivalent-alternative) with the heat pump.

In bivalent-parallel operation, both heat sources work in parallel at a predefined outside temperature. If the heat generators run bivalent-alternatively, then they operate alternately.

Monoenergetic operation

The heat pump operates up to a predefined outside temperature. If the outside temperature is lower than this, an electric screw-in heater switches on; like the heat pump, this is operated using electricity.

Monovalent operation

The heat pump is the only heat generator in the building.

Coefficient of performance (COP)

The coefficient of performance (or COP  for short) of a heat pump is a parameter determined under standardised test conditions and indicates the output of a heat pump. The COP is suitable for an initial comparison of different models and provides an insight into their output and the heat source used.

Although initially somewhat cryptic-looking, the sequence of numbers and letters is actually quite easy to decipher.

The letters A, B, and W stand for the terms air, brine, and water respectively. Assuming a COP of B2W35 for our heat pump, this would mean that a brine heat pump at 2 degrees brine temperature would generate hot water at a temperature of 35 degrees under normal conditions.

Annual COP (ACOP)

The annual COP (Annual COP ) compares the energy generated with the energy required to do so, providing an efficiency factor. The higher the annual COP, the more efficient the heat pump is.

Depending on the heat source, the annual COP is usually between 3.5 and around 4.5; that is, a kilowatt hour of electricity is converted into between 3.5 and 4.5 kilowatt hours of heat output.

Go to ACOP calculator