Q: What is a GeoExchange unit?
A: A GeoExchange unit is a heating and cooling system that provides heat in winter and cooling in summer, at efficiencies that are far better than those of alternative systems. Like a conventional heat pump, it is essentially an air conditioner that can also run in reverse to provide heat in the winter. The primary difference is that it relies on the nearly constant temperature of the ground or ground water for heat transfer instead of the widely fluctuating temperature of the outside air. As a result, a GeoExchange unit saves energy, cuts electric and hot water bills, reduces greenhouse gas emissions, and offers lower maintenance than conventional heating and cooling systems.

Q: How does a GeoExchange unit operate?
A: A GeoExchange unit simply transfers thermal energy (heat) from the ground or ground water into the space being conditioned during the winter months and transfers excess heat from the structure back into the ground or ground water in the summer months. Because the temperature of the ground or ground water remains fairly constant throughout the year – ranging from about 45-50 degrees F in northern latitudes to 70-80 degrees F in the south – operating efficiencies remain high year-round.

Q: How is heat actually transferred between the ground and the building?
A: As a fluid is circulated through the buried pipe, it attracts heat from the surrounding ground; the further the fluid flows, the more heat it can extract. When the warm fluid returns to the compressor heat is taken from the fluid and transferred to the heat pump where it warms air prior to circulation into the building. In summer, the compressor transfers building heat into the fluid, which then dissipates this heat into the ground as it circulates through the loop, keeping the building cooled.

Q: How can a GeoExchange system heat both air and water?
A: The solar heat that is transferred from the ground can be used either to warm air (for use in a forced air distribution system) or to heat water (for drinking or service applications, in radiant heating or swimming pools).

Q: How does the GeoExchange system extract heat from frozen soil?
A: The loop is buried below the frost line, and insulation is used to protect any section that may rise above the frost line (e.g.: as the pipe enters the building) to avoid freezing in winter.

Q: Can a GeoExchange system be used for anything other than heating and cooling a building?
A: Twenty percent of the average energy demand in a residential home is for water heating thus most units include a component to heat water for potable or sanitary use. Heat pumps can also be used to dehumidify indoor swimming pool areas by controlling condensation using a minimum ventilation and using the recovered heat from the main heating process.

Q: What makes a GeoExchange system different from conventional heating and cooling systems?
A: Most space heating and water heating in Canada is provided by combustion of natural gas, oil or propane, or by electric resistance while most cooling is provided by electric air conditioning. A GeoExchange system does not use combustion to make heat; it simply transfers solar heat from the ground at very high efficiency. This lack of combustion makes a GeoExchange system the best choice from an environmental and safety standpoint.

Q: Do GeoExchange systems have outdoor units?
A: The ground loop is buried in the soil and enters the building through an underground penetration. There are no visual components outdoors.

Q: Does a GeoExchange system require separate ground loops for heating and cooling?
A: In Canada, a GeoExchange unit is used more for heating than for cooling, and a reversing valve can be switched between seasons to reverse the flow of the loop fluid and the operation of the heat pump. The system design may be over-sized for the second application but that means the unit cycles less frequently.

Q: Can a GeoExchange system work with a diesel generator?
A: The generator must be of sufficient capacity and have a constant voltage to meet the electrical demands of the GHP including the circulating pump used to move fluid in the loops and the distribution pump for the hot air.

Q: What is the difference between a GeoExchange and an air-source heat pump?
A: An air-source system is a similar concept to a GeoExchange system but it extracts heat from outside air instead of from the ground. Winter air does not contain much latent heat and the efficiency of an air-source unit drops significantly when outside temperatures drop below 0o Celsius. Also, the compressor in an air-source unit is located in an outdoor compartment where it is noisy and exposed to weather elements. By comparison, a GeoExchange system is more efficient due to higher ground temperatures in winter and the absence of any outdoor equipment makes a GeoExchange system quieter, more aesthetically pleasing and longer lasting.

Q: Can GeoExchange systems be used in commercial or industrial buildings? In an apartment or school?
A: Absolutely. Research conducted for Natural Resources Canada (NRCan) confirms that these applications are very cost-effective and provide high reductions of greenhouse gas emissions. More than half the GeoExchange systems installed in Canada are used for commercial and institutional applications.

Q: Can heating and cooling occur simultaneously in the same building?
A: Yes. Each heat pump unit can perform only one function at a time but a larger building (with more than one unit) can provide heating to one spot and cooling to another. This is a common application in schools and other institutional facilities where there is a diverse energy load requirement. The practice also increases the efficiency of the overall system because the heat removed from room A can be transferred to room B thereby reducing the size (and cost) of the ground loop.

Q: Can a GeoExchange system provide heat recovery ventilation?
A: Some units integrate a HRV unit that can provide fresh air and enhance building comfort, and offer enhanced defrosting without creating negative pressure inside the building.

Q: Is the compressor in a GeoExchange unit the same compressor as in a refrigerator?
A: In principle yes it is as a refrigerator is designed to cool food by extracting heat from the package and transferring the warm air into the kitchen. There are numerous compressors on the market all of which use the same general principles although the specific models used in a GeoExchange system are different from the kitchen appliance.

Q: Is there a national or local standard for the design and installation of a GeoExchange system?
A: Design and installation are covered under national CSA standards C447 (commercial) and C445 (residential). As of March 2002, both applications are covered under the CSA C448 standard. CGC is not aware of any mandatory provincial regulations pertaining to GeoExchange systems, although some municipalities or regulatory agencies may have guidelines or rules that have an impact on the design or installation of GeoExchange systems. Internationally the IGSHPA, International Ground-Source Heat Pump Association, certifies installers of GeoExchange systems.