Geothermal Hydronic Heat Pumps

Geothermal heat pumps offer a great solution for powering your hydronic heating or cooling system for your home. With pipes laid underground, they generate energy from the relatively constant temperature of the  earth and use this to heat or cool the water in your hydronic system.

Geothermal heat pump

How Geothermal Heating and Cooling Works

Geothermal heating and cooling systems tap into the abundant levels of energy stored below the earth’s surface to reduce your heating and cooling costs by as much as 30 percent. Even when it is freezing outside, temperature levels remain steady deep below the ground. With consistent temperatures under ground, geothermal heat pumps generate from one part electricity up to five parts heat. Best of all, geothermal systems can be installed in any sized home or business in virtually any location and are becoming increasingly popular in Australia.

In winter heat is extracted from the ground no matter what the ambient temperature. This is then converted into a higher temperature through a refrigeration system, similar to a standard air conditioner, except the heat is transferred to the water. This hot water can then be used for underfloor heating, radiators, trenches, etc. 

In summer, the heat from the property is absorbed into water through an air conditioning unit.  The warm water extracted is then passed through the cooler earth and cool water is then pushed back into the home and your hydronic cooling system.

The process can be explained as follows:

  1. The temperature of the ground remains relatively constant year-round. This natural heat is collected through a series of pipes, which are installed below ground and filled with a mixture of water and corrosion inhibitors. 
  2. The fluid is circulated through the ground pipes, where it exchanges heat with the ground. The cooler surface will always be heated by the warmer one.
  3. The warmed fluid continues to circulate from the ground to a heat pump.
  4. The heat pump increases the heat from the fluid in the loop by compressing it, and then transfers it across a heat exchanger and into the air stream, where a blower distributes heated air through the ductwork just like a conventional forced air furnace. During the summer months, the system is run in reverse to provide air conditioning.
  5. The Geothermal system can generate enough heat for your home’s hot water system as a by product when doing your space conditioning.
How Geothermal works
How Geothermal Works

The heat pump system can also be designed to transfer the energy into water to operate an underfloor floor heating system or radiators. Lets take at look at the heating and cooling cycles in more detail.

Geothermal Heating Cycle

The heating process involves the extraction of heat energy from the ground, and moving it into the building. Transferring the heat from the earth to the building involves a cycle of evaporation, compression, condensation and expansion.  

Geothermal heating cycle diagram

The heating cycle starts as cold liquid passes through a  heat exchanger and absorbs heat from the low temperature source (earth loop fluid or well water). The refrigerant evaporates into a gas as heat is absorbed. The gaseous refrigerant passes through a compressor where the refrigerant is pressurised, raising its temperature to over 180° F. The hot gas then circulates through a refrigerant-to-air heat exchanger where heat is removed as the cooler return air passes over it. Now heated, this warm air is delivered into the building by way of the blower and the duct system. Upon releasing its heat energy into the air, the refrigerant returns to the water-to-refrigerant heat exchanger where the process is repeated continuously during the heating process. 


Geothermal Cooling Cycle

The cooling process involves the extraction of heat energy from the air in the building, and moving it into the earth. Transferring the heat from the air in the building to the earth involves a cycle of expansion, condensation, compression, condensation and evaporation. A refrigerant is used as the heat transfer medium.

Geothermal Cooling Cycle Diagram

The cooling cycle starts as the compressor delivers refrigerant to the water-to-refrigerant heat exchanger. Heat from the refrigerant is absorbed by (rejected into) the low temperature source (earth loop fluid or well water) resulting in the refrigerant turning cold. The cold refrigerant passes through a refrigerant-to-air heat exchanger. As warm, humid air from the return air duct system is passed over the cold air coil, the air is cooled and dehumidified the returned into the building, cooling the space.

The heat from the warm air that returns to the unit is absorbed by the cold refrigerant, turning the refrigerant into a hot gas. The hot refrigerant is returned to the compressor where the process is repeated continuously during the cooling process. A portion of the heat returning to the compressor (from the hot return air) is diverted to another refrigerant circuit that generates hot water and delivers it to the water heater by way of a small pump.

For more information on Geothermal heating and cooling processes see Geothermal Industries.

Benefits of Geothermal Heat Pumps

  • Provide consistent heating or cooling through heatwaves or freezing conditions.
  • Low environmental impact, with limited carbon emissions
  • They consume 20-50% less energy than conventional heating or cooling systems
  • Can be used for heating and cooling your home

Australian Hydronic Heating and Cooling, a division of AJ’s Plumbing Pty Ltd, work with suppliers such as Stiebel Eltron and Rinnai, companies which have become synonymous with high quality space heating, water heating and renewable energy products. Below are details of a range of their geothermal hydronic heat pumps which Australian Hydronic Heating and Cooling can source, install and maintain for your property.


Save money while saving energy – the affordable WPF (S) basic series provides an ideal alternative to highly integrated geothermal heat pumps. Featuring top STIEBEL ELTRON quality, the WPF (S) basic is designed for easy installation. Thanks to its compact and timeless design, it fits nicely into your home without wasting valuable space.
  • Geothermal hydronic heat pump installed indoors for underfloor and radiator heating
  • Compact design for easy placement in your home
  • Optimal energy use through efficient circulation pump
  • Timeless design
  • Highest European energy efficiency rating A++ for low energy bills
  • Extremely quiet operation thanks to advanced sound technology
  • Ideal to use in retrofits: up to 65 °C flow temperature
Stiebel internal geothermal hydronic heat pump


In cascading operation, these compact geothermal heat pumps achieve an output of up to 400 kW. To save space in the process, individual heat pumps can be stacked on top of each other. This efficient heating solution was specifically developed for larger residential complexes, as well as commercial and industrial buildings.
  • Geothermal hydronic heat pump installed indoors or outdoors for heating
  • Specially developed for larger residential complexes, as well as commercial and industrial buildings
  • Potential for remote PC monitoring
  • Space savings as a result of stackable design
  • Very quiet operation
  • Flow temperatures up to 75 °C


Rinnai’s Geoflo geothermal heat pump harnesses the free green renewable energy from the earth for cost effective heating and cooling of your home.

The system utilises the stable temperatures found underground, and extracts this as free green energy via state of the art Rinnai technology which reliably delivers highly efficient heating and cooling air conditioning comfort in your home regardless of the outside air temperature.

  • Cost Efficient: can cut electricity consumption by 30% compared to traditional air conditioning system.
  • Quiet Operation: the geothermal system relies on the temperature of the ground to heat and cool your home, with no noisy fans.
  • Space Saving: the hardware requires a lot less space than traditional HVAC systems.
  • New or Retrofit: can be installed in new builds or retrofitted to existing buildings.
  • Easy Maintenance: with few moving parts the system has high durability and reliability.
Rinnai Geothermal Geoflo

If you are thinking of installing a hydronic heating or cooling system, and are interested in finding out more about powering the system with a geothermal heat pump, give us a call or send us an email.

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