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 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 again
becomes 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 hot
water 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 provide
some 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.
The 4 Loop Types?
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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