FAQ'S
How Do Geothermal Systems Work?
The installation of a geothermal heating and cooling system in a new or existing building requires three basic components:
1. An energy source to deliver heat to the building.
Most commonly this is a closed loop of polyethylene pipe, which has been buried in the ground or placed in a pond. This pipe, made from the same material as is used for gas lines, is joined with a heat welding process, totally inert, maintenance free, and will last a lifetime. The loop is filled with a solution of water and environmentally friendly antifreeze, connected to the indoor unit (furnace), and pressure tested. When in operation this liquid is pumped through the furnace.
Another alternative, (if an adequate supply of well water is available),is an open loop. When using this system, well water is pumped through the furnace, and returned to the ground through a second or return well.
The temperature of the earth in South Western Manitoba is constant at about 44 degrees F or 6 degrees C, so the liquid entering the indoor unit from the loop is normally about this temperature. Obviously a temperature higher than this is required to heat a building in Manitoba to a comfortable level in winter, and this is why we require the second component of our geothermal system.
2. A Heat pump to enhance the heat energy from the loop.
The heat pump consists of a compressor, a high temperature heat exchanger, an expansion valve, and a low temperature heat exchanger, all connected in a closed circuit, (similar to the one in your refrigerator), and filled with an environmentally friendly refrigerant. The heat pump uses a cycle of evaporation, compression, condensation, and expansion, as well as natural conduction whereby heat travels from a warmer to a cooler surface.
With geothermal heating and cooling two basic types of heat pumps are used.
Water to Air
The process starts when cold liquid refrigerant in the low temperature heat exchanger absorbs heat from the warmer loop liquid and evaporates. This gas is compressed, becoming very hot, and travels through the high temperature heat exchanger where heat is transferred into the air stream that is being circulated through the building by the furnace fan. The refrigerant, having lost its absorbed heat, condenses to a liquid and passes through the expansion valve where the pressure is released and againbecomes a cold liquid. The refrigerant now goes back to the low temperature heat exchanger to absorb more heat and start the cycle over again.
Water to Water
With this type of heat pump the same process is used except for the high temperature heat exchanger. At this point the heat is transferred into water for hydronic heating or cooling applications.
The heat energy that has been enhanced by the heat pump has now been transferred to the third component of the geothermal system.
3. The heat distribution system.
The most common heat distribution system is forced air. With this system the heat from the high temperature heat exchanger is absorbed by the fan forced air as previously described and circulated throughout the building through ductwork in a manner similar to that common with most electric or fossil fuel furnaces.
The second common heat distribution method is by using hydronic or hotwater systems. With this system the heat is absorbed in the high temperature heat exchanger into water and either pumped directly into the distribution system or to an insulated tank where it is stored until it is required to heat the building. The most popular methods of hydronic heating with geothermal systems is by using heated radiant floors, or fan coils if a heated floor is not possible.
Some geothermal furnace units are equipped with a dual distribution system whereby they can provide both forced air and on demand hot water for applications where this is required.
When the weather turns warm, simply reversing the cycle, and moving heat from the building back into the earth cools the building. Forced air geothermal systems are very efficient for cooling and do an excellent job of dehumidification in summer, but this is not an option with hydronic heat transfer systems.
An additional feature of most geothermal systems is the ability to providesome of the domestic hot water heating for residential or small commercial buildings. When the furnace unit is either heating or cooling a small pump and heat exchanger in the furnace, called a desuperheater, circulates some of the water from the hot water tank through the furnace where it absorbs heat from the high temperature refrigerant.
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*Click on the images above to enlarge them for a better view.
Ways to Drill a Loop
The installation of a loop can be done in any of the following ways, depending upon your locating and soil conditions:
Vertical Loops are installed where space is limited. Holes are bored using a drilling rig, the pipe is inserted, and the holes are filled. The pipes are connected horizontally a few feet below the surface.
Horizontal Loops are used where adequate land is available. One or more trenches are dug using a backhoe or chain trencher. Polyethylene pipes are inserted and the trenches are backfilled.
Pond Loops can be installed if an adequately sized body of water is located close to the home. A series of coils are sunk to the bottom, connected by a header with supply and return pipes leading to the home.
Open Loops are used where there is an abundant supply of quality well water. The well must have enough capacity to provide adequate flow for both domestic use and the WaterFurnace unit.
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