Geothermal system components
- Ground loop
A closed ground loop system consists of a series of high density polyethylene pipes buried in your yard. A heat transfer fluid, comprised of antifreeze and water, is inside the ground loop pipes. This heat transfer fluid removes heat from (heating mode) or delivers heat to (cooling mode) the earth surrounding the ground loop. The ground loop pipes carry the heated fluid to the heat pump furnace unit in the home.
- Heat pump furnace unit
The heat pump’s system improves the consistency of the heat, which is then circulated throughout the home by way of the distribution system. The heat pump furnace unit provides both heating and cooling.
- Distribution system
In a forced air system, a fan in the heat pump furnace unit blows air over a fan coil and the heated or cooled air is distributed through the home’s ductwork. In a hydronic system, hot water is circulated through radiators or a system of in-floor pipes to provide heat.
Geothermal heat pumps may include a device known as a desuperheater to help with domestic water heating. In summer, the desuperheater recovers some of the heat that would otherwise be sent to the ground loop to help produce hot water. In winter, some of the capacity of the heat pump may be diverted from space heating for the same purpose. Desuperheaters save approximately 25% on domestic water heating costs.
- Supplemental/auxiliary electric heater
The majority of geothermal heat pump systems are designed with an auxiliary electric resistance heater built into the system. Typically this auxiliary electric heater is installed to allow your contractor to more optimally size the geothermal heat pump system for the home’s base heating load, and allow the electric heater to assist the system during the few coldest days of the year. This provides an emergency backup heat source if there are any operational issues with the geothermal heat pump system.
Ground loop configurations
Your contractor will recommend one of these 4 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.
Horizontal closed loop
- 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 2 to 3 metres 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 of pipe per tonne of heat output.
- Rural properties of over 1 acre are typically best suited for horizontal configuration.
- Not recommended in dry sands and gravels.
Horizontal loop designs include 1-, 2-, and 4-pipe, and slinky coil configurations. The most common are 2- and 4-pipe configurations.
Vertical closed loop
- 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 or deeper.
- Vertical boreholes measure approximately 13 to 18 centimetres in diameter and are typically spaced 3 to 6 metres apart.
- A pair of 2 to 3 centimetre 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 1 to 2 metres under grade.
- Proper design is essential since pipe length can vary from 91 to 183 metres 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.
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 is 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