WaterFurnace OM1500MW Owner's Manual - How Geothermal Systems Work
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ABOUT YOUR WATERFURNACE SYSTEM
How Geothermal Systems Work
Geothermal heat pumps utilize some of the same technology found in your home's refrigerator. They are both devices
that move heat energy. Your refrigerator removes heat from the food and transfers it to the air in your home. Your
geothermal heat pump removes heat energy from the earth to heat your home and removes heat energy from inside
your home to cool it.
A Ground Source Heat Pump System consists of a water-to-air or water-
to-water heat pump, connected to a series of long plastic pipes buried
below the earth’s surface or placed in a pond. These systems can also
utilize well water instead of the earth loop. As fluid from the earth loop
or well water is moved through the unit, the heat pump transfers thermal
energy that heats or cools the home or building.
The ground serves as a giant solar collector, storing heat energy. At
depths greater than 30 feet, the temperature is about the same as the
annual average outdoor air temperature for that climate. Air temperatures
may fluctuate as much as 50° F above and below the annual average
temperature. However, only a few feet below the surface the changes in
earth temperatures are much less severe. Earth temperature variations
decrease with increasing depth. During heating, the earth serves as a
heat source. During cooling, the earth serves as a heat sink.
The earth loop is placed in the ground either horizontally or vertically, or it can be placed in a pond. Water (or water and
anti-freeze) is circulated through the pipe, transporting heat to the heat pump during the heating mode and away from
the heat pump during the cooling mode. The heat transfer takes place inside the heat pump in a water-to-refrigerant
heat exchanger.
HEAT PUMP OPERATION—Geothermal heat pump systems consist of four circuits:
1.
Air circuit — The duct system that distributes the air throughout the home or building and returns it to the unit.
2.
Refrigerant circuit — A sealed and pressurized circuit of refrigerant including compressor, expansion valve,
water-to-refrigerant heat exchanger, air coil and reversing valve. The refrigerant is R-410A.
3. Earth loop circuit — The piping system buried in the ground or in the pond (or well water) with fluid that is circulated
by pumps to and from the geothermal unit.
4. Hot water circuit — Domestic water can be heated in a geothermal unit with a device called a hot water assist. A
piping connection is made from the geothermal unit to the water heater.
Each of these circuits is closed and sealed from the others —there is no direct mixing. However, heat energy does mix
from the refrigeration circuit to the other three circuits.
The air circuit, the earth loop circuit, and the domestic hot water circuit always travel in the same direction. However, the
refrigeration circuit will change direction depending on what mode (heating or cooling) the unit is in. (The exception to
the change in direction of refrigerant flow is the flow through the compressor. This change of direction is controlled by
the reversing valve.)