A geothermal heat pump moves heat into or out of the earth to heat or cool your home.
The system has three main components:
- Ground loop system
- Heat pump furnace unit
- Distribution system
The ground loop system of polyethylene pipes extracts heat from soil beneath the frost line. In cooling mode, the pipes return heat to the earth. There are four basic ground loop configurations. The heat pump furnace unit and distribution system are located inside your home. Heat is transferred from the ground loop system to the furnace unit. Once inside the furnace unit, the heat is moved to the distribution system to heat your home.
The system operates in reverse to cool your home.
Operation: Homeowners simply set the temperature with an electronic thermostat. The system will heat or cool to achieve the temperature.
Maintenance: Manitoba Hydro recommends inspecting/replacing the air filter monthly; routine checks to ensure supply and return air vents are clear; and an annual system check by a qualified service professional. A certified contractor can inform you about additional operation and maintenance details of your system.
Ground Loop Configurations
- Horizontal Closed
- Loop Vertical Closed
- Loop Well-to-Well or Open Loop
- Lake or Pond Closed Loop
Your contractor will recommend one of these four ground loop designs.
The recommendation will be based on: the size of your home and yard; your home’s design heat loss; soil conditions; equipment sizing; use of a desuperheater; required entering heat transfer fluid temperature; and the availability and quality of groundwater.
- Rural areas where space permits; areas where soils can be easily excavated; land with high moisture content is optimal for these systems.
- Requires more land area than any other loop system. The pipe is generally buried in a trench, usually to 3 metres (6 to 10 feet) deep in one continuous loop or a series of parallel loops.
- Proper design is critical, since horizontal pipe lengths can vary between 91 and 914 metres (300 and 3,000 feet) of pipe per tonne of heat output.
- Rural properties of over one acre are typically best suited for horizontal configuration.
- Not recommended in dry sands and gravels.
- Homes with limited available land area, or where other loop configurations are not cost-effective.
- Vertical loops require fewer feet of piping than horizontal loops, since ground temperatures are more constant at a depth of about 6 metres (20 feet) or deeper.
- Vertical boreholes measure approximately 13–18 centimetres (5–7 inches) in diameter and are typically spaced 10–20 feet apart.
- A pair of 3/4–1 1/4 inch pipes are inserted in the borehole connected by a u-bend assembly on the bottom. The pipes in each of the boreholes are tied together in a trench 4–6 feet under grade.
- Proper design is essential since pipe length can vary from 91 to 183 metres (300 to 600 feet) per tonne of heat output.
- Your contractor may drill a test borehole to determine soil conditions to confirm loop length and design prior to system installation.
Horizontal loop designs include one-pipe, two-pipe, four-pipe, and slinky coil configurations. The most common are two and four-pipe configurations.
Well-to-Well or Open Loop
- Homes with access to a good supply and quality of well water. Open loop systems extract heat directly from well water. Well water is pumped to the heat pump system from a supply well, and is then returned to a second well or “return well”.
- Typically, the entering water temperature of an open loop system is approximately 6 C higher than a closed loop system. Higher entering water temperatures can lead to improved efficiency of the geothermal heat pump system.
- Water sources with high levels of salt, chlorides or other minerals can cause premature system failure or inefficient operation.
- Annual cleaning and maintenance of the heat exchanger(s) by your installation contractor in your heat pump furnace unit will be required to reduce mineral scaling.
- Pumping power may become an issue in installations that require deep supply wells.
Approvals from the appropriate environmental authorities in your area may be required..
Lake or Pond Closed Loop
- Areas with a pond or lake nearby and poor drilling/excavation conditions, where the loop field can be submerged in
water, rather than buried in the ground.
- Approvals from the appropriate environmental authorities in your area are required (i.e. Department of Fisheries and Oceans).
The loop field must be:
- properly anchored to remain on the bottom of the body of water;
- submerged deep enough under water;
- protected at the shoreline to avoid being dragged away by the movement of spring ice break-up.
- Lake/pond system is an extremely specialized configuration, so it is important that an installation contractor has sufficient experience and understands all aspects of this type of installation