3. How Geothermal Heat Works

Geothermal heat is 350% efficient because it pumps a coolant underground and uses the earth to warm it to about 60 degrees. The warmed coolant transfers heat from the earth to a refrigerant within the heat pump. (It’s referred to as a heat pump rather than a furnace, as it doesn’t produce heat, only transfers it.) The first question I had was “How can 60 degree coolant heat a home to 70 degrees?”

The temperature of the gas refrigerant is manipulated through compression and expansion. The gas is compressed to raise its temperature, and is then pumped through an air coil to transfer heat to the air that is circulated through the ductwork. After it transfers its heat, the refrigerant leaves the air coil in its liquid state and is exposed to the coolant pumped through the buried pipes, adding heat to the system. The cycle repeats itself, compressing the warmed refrigerant and pumping it through the air coil. Reversing the flow of the refrigerant and cooling it through expansion provides cool air to the house.

The system uses the following components:

R-410a refrigerant in a closed loop within the heat pump

• This refrigerant is continuously cycled between its liquid and gaseous states
• The boiling point of this refrigerant is –40 degrees. The boiling point rises as the pressure and temperature rise. Cycling between its liquid and gaseous states increases the heat transferred in the air coil.
• This refrigerant is environment friendly and will not deplete the ozone layer in the event of a leak

Coolant pumped through a closed loop of buried pipes to transfer heat from or to the earth (some systems cycle ground water through an open loop)

• During the winter, the coolant transfers heat from the ground to the refrigerant to convert it to a gas
• During the summer, the coolant is used to cool the refrigerant and transfers heat from the system to the earth
• This coolant is environment friendly and will completely decompose within three days in the event of a leak
  A compressor to increase the temperature of the refrigerant by compressing it (or decrease the temperature by expanding it) while in its gaseous state

An air coil to transfer heat between the refrigerant and the air pumped through the ductwork

• During the winter, the refrigerant is pumped through the air coil as a gas and is cooled back to its liquid state by the air circulated through the ducts. (The air is warmed to about 180 degrees in this process.)
• During the summer, the refrigerant is pumped through the air coil, where it cools the air circulated through the ducts
• The warmed refrigerant is cooled by the coolant in the buried pipes. (The air is cooled to about 45 degrees in this process.)

A bank of electric heating elements to provide additional heat in the event that the heat pump can’t produce hot air fast enough.

• These elements are turned on if the house is about 3 degrees or more below the thermostat setting, and cycle off as soon as the house is warmed within one to two degrees of the thermostat setting.