PO Box 841
Austin, Mn 55912
Phone 507.396.0247
Fax 507.437.8378
Email Patrick Harty
Copyright © 2006 by Minnesota Geothermal, LLC
Geothermal Definitions
Geothermal Heat Pump:
A geothermal heat pump model uses the thermal energy of the ground
or groundwater as the heat source and heat sink for residential space heating and/ or cooling. It may
provide both space heat and cooling, cooling only or heating only functions. They are similar in size
to a typical furnace.
Heat Sink: The medium - air, water, earth,etc- which receives heat from the heat pump.
Heat Source: The medium - air, water, earth, etc- from which the heat is extracted by the heat pump.
Ground heat Exchanger:
The method by which heat is exchanged with the ground, groundwater or
surface. Geothermal heat pumps may use any form of ground heat exchanger, which include horizontal or
vetical closed loops, open loop vertical wells, or surface water.
Closed Loop System:
Closed loop systems are made of durable, high density polyethylene pipe,
buried in earth or submerged in a lake or pond. They transfer heat by circulating a solution of water
and environmentally safe antifreeze through the system.
Vertical Closed Loop:
This type of loop configuration is ideal for homes where yard space is insufficient,when the earth is rocky
close to the surface, or for retrofit applications where minimum disruption of the landscape is desired.
Contractors bore vertical holes in the ground 150 to 450 feet deep. Each hole contains a single loop of
pipe with a u-bend at the bottom. After the pipe is inserted, the hole is backfilled or grouted. Each vertical
pipe is then connected to a horizontal pipe, which is also concealed underground. Vertical loops are generally
more expensive to install, but require less piping then horizontal loops.
Horizontal Closed Loop:
This configuration is usually the most cost effective when adequate yard space is available, and trenches are
easy to dig. Workers use trenchers or backhoes to dig the trenches three to six feet below the ground and lay
a series of parallel plastic pipes. The trenches are then backfilled. A typical horizontal loop will be 400 to
600 feet long per ton of heating and cooling capacity. The pipe may be curled into a slinky shape in order to fit
more of it into shorter trenches.
Open Loop System:
A ground heat exchanger in which the heat transfer is part of a larger enviroment. The most common open loop
systems use groundwater or surface water as the heat transfer medium.
Desuperheater:
A partial heat recovery system that captures heat from the hot refrigerant as it leaves the
heat pump compressor and transfers it to the domestic hot water. Desuperheaters provide hot water only while
the heat pump is providing space conditioning. Located inside the heat pump.
Payback Analysis:
Overall measure of the efficiency and value of your home comfort system. By combining
your purchase price and ongoing operating costs, a payback analysis determines the number of years required
before monthly energy savings offset the purchase price.
Load Estimate:
A series of studies performed to determine the heating or cooling requirments of your home.
An energy load analysis uses information such as the square footage of your home, window or door areas,
insulation quality and local climate to determine the heating and cooling capacity needed by your furnace,
heat pump or air conditoning. When refering to heating, this is often known by Heat Loss Analysis, since a
home's heating requirements are determined by the amount of heat lost through the roof, entryways and walls.
Capacity:
The ability of a heating or cooling system to heat or cool a given amount of space. For heating, this
is usually expressed in BTU's. For cooling it's usually given in tons.
AFUE:
Annual Fuel Utilization Efficiency. Indicated as a percentage, your furnaces AFUE tells you how much
energy is being converted to heat. For example, an AFUE of 90 means 90% of the fuel is being used to heat
your home, while the other 10% escapes as exhaust with the combustion gases.
SEER:
Seasonal Energy Efficiency Ratio is a measure of the cooling efficiency of your air conditioner. The
higher the SEER number, the more efficient the system is at converting electricity into cooling power.
EER:
Energy Efficiency Ratio is the cooling capacity (in BTU/hr) of the unit divided by it's electrical input
(in watts). The measure of usable cooling capacity derived from an amount of electrical power consumed.
BTU:
British Thermal Unit. It takes 1 BTU of heat energy to raise the temperature of one pound of water
one degree Fahrenheit.
Ton: A unit of measure for cooling capacity. One ton= 12,000 BTU's per hour.
Compressor:
The central component of a heat pump system. The compressor increases the pressure of a
refrigeration fluid, and simultaneously reduces it's volume, while causing the fluid to move through the system.
Scroll Compressor:
A specially designed compressor that works in a circular motion vs an up and down
piston action.
Blowers: Fans used to force air across the heat exchanger.
Circulating Pump:
A devise which circulates the antifreeze or water through the closed loop and heat
exchanger.
Evaporative Coil:
The component of a heat pump over which air is circulated to transfer heat in or out
of the home.