1. How does a geothermal system work?
2. What makes a geothermal system different
from conventional systems?
3. How efficient is a geothermal system?
4. What does geothermal mean to the environment?
5. Do geothermal systems require much maintenance?
Questions you should ask about a new
1. What is the BTU size of the furnace that's
2. Is the efficiency rating actual or just
a manufacturer's average?
3. Will the minimum entering water temperature
have an affect on which heat pump I buy?
4. Are the dealer and loop installers qualified?
5. Will open- or closed-loop be best for you?
6. How long is the payback period for your
geothermal heat pump system?
7. If a home has ceiling cable heat or baseboard
heat, do air ducts need to be installed?
8. If you want to know more about geothermal
heat pump systems, whom should I contact?
Heat Pumps: What are they and
how do they work
1. What is a geothermal heat pump?
2. How does it work?
3. How is heat transferred between the earth
4. Does it do both heating and cooling?
5. Do I need separate ground loops for heating
6. What types of loops are available?
7. Does the underground pipe system really
1. What is a closed-loop system?
2. Where can this loop be located?
3. How deep and long will my trenches be?
4. How many pipes are in a trench?
5. What if I don't have enough room for a
6. How long will the loop pipe last?
7. How are the pipe sections of the loop joined?
8. Will an earth loop affect my lawn or landscape?
9. Can I reclaim heat from my septic system
10. Can I install an earth loop myself?
11. I have a pond near my home. Can I put
a loop in it?
1. What is an open-loop system?
2. What do I do with the discharge water?
3. How much groundwater does an open-loop
4. What problems can be caused by poor water
5. Does an open-loop system cause environmental
6. Are there any laws that apply to open-loop
Parts of the system
1. What are the components of a geothermal
heat pump system?
2. Are all geothermal heat pumps alike?
3. Will I have to add insulation to my home
if I install one of these systems?
4. Can a geothermal heat pump also heat water?
5. Is a geothermal heat pump difficult to
6. Can a geothermal heat pump be added to
my fossil fuel furnace?
7. I have ductwork, but will it work with
8. Do I need to increase the size of my electric
9. Should I buy a heat pump large enough to
heat my home with no supplemental heat?
10. Do geothermal heat pumps have outdoor
11. The Mechanics of the Heat Pump Process
does a geothermal system work? Throughout the year,
outdoor temperatures fluctuate with the changing seasons.
However, underground temperatures do not. In fact, about
four to six feet below the earth's surface, temperatures
remain relatively constant year-round. A geothermal system,
which consists of an indoor unit and a buried earth loop,
capitalizes on these constant temperatures.
In the winter, fluid circulating through the system's earth
loop absorbs stored heat and carries it indoors. The indoor
unit compresses the heat to a higher temperature and distributes
it throughout the building. In the summer, the system reverses,
pulling heat from the building, carrying through the earth
loop and depositing it in the cooler earth.
2. What makes
a geothermal system different from conventional systems?
A geothermal system utilizes the energy from the sun, which
is stored in the earth, to heat and cool homes and buildings.
Typically, electric power is used only to operate the unit's
fan, compressor and pump. So, unlike conventional systems,
geothermal systems do not burn fossil fuel to generate heat--they
simply transfer heat to and from the earth.
3. How efficient
is a geothermal system? A geothermal system is more
than three times as efficient as the most efficient conventional
system. Because geothermal systems do not burn combustible
fuel to make heat, they provide three to four units of energy
for every one unit used to power the system.
4. What does geothermal
mean to the environment? Because geothermal systems
work with nature, not against it, they minimize the threats
of acid rain, air pollution and the greenhouse effect. An
environmentally friendly fluid is used in the closed, continuous
5. Do geothermal
systems require much maintenance? No. In fact, geothermal
systems are practically maintenance free. When installed
properly, the buried loop will last for generations. And
the other half of the operation--the unit's fan, compressor
and pump--is housed indoors, protected from the harsh weather
conditions. Usually, periodic checks and filter changes
are the only required maintenance.
Questions you should ask about
a new heating system
1. What is the
BTU size of the furnace that's being proposed? Furnaces
are designed to provide specific amounts of heat energy
per hour. The term "BTUH" refers to how much heat can be
produced by the unit in an hour. Before you can determine
what size furnace you'll need, you must have a heat loss/heat
gain calculation done on the structure. From that, an accurate
determination can be made on the size of the heating system
you'll need. Most fossil fuel furnaces are substantially
oversized for heating requirements, resulting in increased
2. Is the efficiency
rating actual or just a manufacturer's average? All
types of heating and cooling systems have a rated efficiency.
Fossil fuel furnaces have a percentage efficiency rating.
Natural gas, propane and fuel oil furnaces have efficiency
ratings based on laboratory conditions. To get an accurate
installed efficiency rating, factors such as flue gas heat
losses, cycling losses caused by oversizing, blower fan
electrical usage, etc., must be included.
Geothermal heat pumps, as well as all other types of heat
pumps, have efficiencies rated according to their coefficient
of performance or COP. It's a scientific way of determining
how much energy the system produces versus how much it uses.
Most geothermal heat pump systems have COPs of 2.5 - 3.5.
That means for every one unit of energy used to power the
system, two and one-half to three and one-half units are
supplied as heat. Where a fossil fuel furnace may be 50-90
percent efficient, a geothermal heat pump is about 300 percent
efficient. Some geothermal heat pump manufacturers and electric
utilities use computers to accurately determine the operating
efficiency of a system for your home or building.
3. Will the minimum
entering water temperature have an effect on which heat
pump I buy? Yes. If you have an open-loop system,
your entering water temperatures (EWTs) may range from the
70s in the southern United States to the 40s in Canada.
All heat pumps can handle temperatures in the moderate to
warm ranges. A closed loop system, on the other hand, will
encounter EWTs below freezing. Not all geothermal heat pumps
will operate efficiently at those temperatures. It's important
for you to know what EWTs your heat pump will handle.
4. Are the dealer
and loop installers qualified? Don't be afraid to
ask for references from dealers. A reputable dealer won't
hesitate to give you names and numbers to call to confirm
his capabilities. The same applies to the loop installer.
5. Will open-
or closed-loop be best for you? That depends on several
factors as stated earlier. A dealer should be willing to
install what's best for you, not for him.
6. How long is
the payback period for your geothermal heat pump system?
To figure this accurately, you must know how much per year
you'll save in energy costs with a geothermal system and
the difference in costs between it and the alternative heating
system and central air conditioner. To calculate your return
on investment (payback in number of years), divide the annual
savings into the additional cost. When you install a geothermal
system in a new home, the monthly savings in operating costs
will generally offset the additional monthly cost in the
mortgage, resulting in a monthly positive cash flow immediately.
Keep in mind that energy savings is only one of the many
benefits you receive from a geothermal system.
7. If a home has
ceiling cable heat or baseboard heat, do air ducts need
to be installed? Not always. It may be desirable
to install geothermal heat pump room units. For some small
homes, one room unit would provide most of the heating and
cooling needs. Ceiling cable or baseboard units could then
be used for supplemental heat.
8. If you want
to know more about geothermal heat pump systems, who should
you contact? Contact your electric utility. Most
electric utilities have information about these systems.
If you have a question they can't answer, they will put
you in contact with someone who can.
Heat Pumps: What are they and
how do they work?
1. What is a
geothermal heat pump? A geothermal heat pump is an
electrically-powered device that uses the natural heat storage
ability of the earth and/or the earth's groundwater to heat
and cool your home or business.
2. How does it
work? Like any type of heat pump, it simply moves
heat energy from one place to another. Your refrigerator
works using the same scientific principle. By using the
refrigeration process, geothermal heat pumps remove heat
energy stored in the earth and/or the earth's groundwater
and transfer it indoors.
3. How is heat
transferred between the earth and the home or building?
The earth has the ability to absorb and store heat energy.
To use that stored energy, heat is extracted from the earth
through a liquid medium (groundwater or an anti-freeze solution)
and is pumped to the heat pump or heat exchanger. There,
the heat is used to heat the air. In summer, the process
is reversed and indoor heat is extracted from indoors and
transferred to the earth through the liquid.
4. Does it do
both heating and cooling? One of the things that
makes a heat pump so versatile is its ability to be a heating
and cooling system in one. You can change from one mode
to another with a simple flick of a switch on your indoor
thermostat. In the cooling mode, a geothermal heat pump
takes heat from indoors and transfers it to the cooler earth
through either groundwater or an underground loop system.
5. Do I need separate
ground loops for heating and cooling? No. The same
loop works for both. All that happens when changing from
heating to cooling, or vice versa, is that the flow of heat
6. What types
of loops are available? There are two main types:
open and closed. The next two sections will give you specifics
7. Does the
underground pipe system really work? The buried pipe,
or "ground loop," is the most recent technical advancement
in heat pump technology. The idea to bury pipe in the ground
to gather heat energy began in the 1940s. It's only been
in the last few years that new heat pump designs and improved
pipe materials have been combined to make geothermal heat
pumps the most efficient heating and cooling systems available.
1. What is a
closed-loop system? The term "closed-loop" is used
to describe a geothermal heat pump system that uses a continuous
loop of special buried plastic pipe as a heat exchanger.
The pipe is connected to the indoor heat pump to form a
sealed, underground loop through which an antifreeze solution
is circulated. Unlike an open-loop system that consumes
water from a well, a closed-loop system recirculates its
heat-transferring solution in pressurized pipe.
2. Where can
this loop be located? That depends on land availability
and terrain. Most closed-loops are trenched horizontally
in yards adjacent to the building. But any area near a home
or business with appropriate soil conditions and adequate
square footage will work.
3. How deep
and long will my trenches be? Trenches are normally
four to six feet deep and up to 400 feet long, depending
on how many pipes are in a trench. One of the advantages
of a horizontal loop system is being able to lay the trenches
according to the shape of the land. As a rule of thumb,
500-600 feet of pipe is required per ton of system capacity.
A well-insulated 2,000 square-foot home would need about
a three-ton system with 1,500 - 1,800 feet of pipe.
4. How many
pipes are in a trench? Normally, a run of pipe is
laid at five feet then looped back over itself at three
feet once the bottom pipe is covered with soil. This allows
more length of pipe to be put in one trench and has no adverse
affect on system efficiency. Other loop designs use four
or six pipes and allow for shorter trenches if land area
5. What if I
don't have enough room for a horizontal loop? Closed-loop
systems can also be vertical. Holes are bored to about 125-150
feet per ton of heat pump capacity. U-shaped loops of pipe
are inserted in the holes. The holes are then backfilled
with a sealing solution.
6. How long
will the loop pipe last? Closed-loop systems should
only be installed using high density polyethylene or polybutylene
pipe. Properly installed, these pipes will last for many
decades. They are inert to chemicals normally found in soil
and have good heat conducting properties. PVC pipe should
not be used under any circumstances.
7. How are the
pipe sections of the loop joined? The only acceptable
method to connect pipe sections is by thermal fusion. Pipe
connections are heated and fused together to form a joint
stronger than the original pipe. Mechanical joining of pipe
for an earth loop is never an accepted practice. The use
of barbed fittings, clamps, and glue joints is certain to
result in loop failure due to leaks.
8. Will an earth
loop affect my lawn or landscape? No. Research has
proven that loops have no adverse effect on grass, trees,
or shrubs. Most horizontal loop installations use trenches
about six inches wide. This, of course, will leave temporary
bare areas that can be restored with grass seed or sod.
Vertical loops require little space and result in minimal
9. Can I reclaim
heat from my septic system disposal field? No. An
earth loop will reach temperatures below freezing during
extreme conditions and may freeze your septic system. Such
usage is banned in many areas.
10. Can I install an earth loop myself?
It's not recommended. In addition to thermal fusion of the
pipe, good earth-to-coil contact is very important for successful
loop operation. Nonprofessional installations may result
in less than optimum system performance.
11. I have a
pond nearby. Can I put a loop in it? Yes, if it's
deep enough and large enough. A minimum of six feet in depth
at its lowest level during the year is needed for a pond
to be considered. The amount of surface area required depends
on the heating and cooling load of the structure.
1. What is an
open-loop system? The term "open-loop" is commonly
used to describe a geothermal heat pump system that uses
groundwater from a conventional well as a heat source. The
groundwater is pumped into the heat pump unit where heat
is extracted, then the water is disposed of in an appropriate
manner. Since groundwater is a relatively constant temperature
year-round, it is an excellent heat source.
2. What do I do
with the discharge water? There are a number of ways
to dispose of water after it has passed through the heat
pump. The open discharge method is the easiest and least
expensive. Open discharge simply involves releasing the
water into a stream, river, lake, pond, ditch, or drainage
tile. Obviously, one of these alternatives must be readily
available and must possess the capacity to accept the amount
of water used by the heat pump before open discharge is
A second means of water discharge is the return well. A
return well is a second well bore that returns the water
to the ground aquifer. A return well must have enough capacity
to dispose of the water passed through the heat pump. A
new return well should be installed by a qualified well
driller. Likewise, a professional should test the capacity
of an existing well before it is used as a return.
3. How much groundwater
does an open-loop system need? Geothermal heat pumps
used in open-loop systems need differing amounts of water
depending on the size of the unit and the manufacturer's
specifications. The water requirement of a specific model
is usually expressed in gallons per minute (g.p.m.) and
is listed in the specifications for that unit. Your heating
contractor should be able to provide this information. Generally,
the average system will use 1.5 g.p.m. per ton of capacity
Your well and pump combination should be large enough to
supply the water needed by the heat pump in addition to
your domestic water requirements. You will probably need
to enlarge your pressure tank or modify your plumbing to
supply adequate water to the heat pump.
4. What problems
can be caused by poor water quality? Poor water quality
can cause serious problems in open-loop systems. Your water
should be tested for hardness, acidity and iron content
before a heat pump is installed. Your contractor or equipment
manufacturer can tell you what level of water is acceptable.
Mineral deposits can build up inside the heat pump's heat
exchanger. Sometimes a periodic cleaning with a mild acid
solution is all that's needed to remove the build-up.
Impurities, particularly iron, can eventually clog a return
well. If your water has a high iron content you, should
be sure that the discharge water is not aerated before it's
injected into a return well.
Finally, you should opt against using water from a spring,
pond, lake or river as a source for your heat pump system
unless it's proven to be free of excessive particles and
organic matter. They can clog a heat pump system and make
it inoperable in a short time.
5. Does an open-loop
system cause environmental damage? No. They are pollution
free. The heat pump merely removes or adds heat to the water.
No pollutants are added whatsoever. The only change in the
water returned to the environment is a slight increase or
decrease in temperature.
Some people are concerned that open-loop systems contribute
to the depletion of our ground water resources. This issue
is not critical in some parts of North America because of
abundant supplies of ground water.
6. Are there any
laws that apply to open-loop installations? In some
localities, all or parts of the installation may be subject
to local ordinances, codes, covenants or licensing requirements.
Check with local authorities to determine if any restrictions
apply in your area.
Parts of the System
1. What are the
components of a geothermal heat-pump system? The
three main parts are the heat-pump unit, the liquid heat-exchange
medium (open or closed loop), and the air-delivery system
2. Are all geothermal
heat pumps alike? No. There are different kinds of
geothermal heat pumps designed for specific applications.
Many geothermal heat pumps, for example, are intended for
use only with higher temperature ground water encountered
in open-loop systems. Others will operate at entering water
temperatures as low as 25°F which are possible in closed-loop
Most geothermal heat pumps provide summer air conditioning,
but a few brands are designed only for winter heating. Sometimes
these heating-only systems incorporate a groundwater cooled
coil that can provide cooling in moderate climates.
Geothermal heat pumps can also differ in the way they are
designed. Self contained units combine the blower, compressor,
heat exchanger and coil in a single cabinet. Split systems
allow the coil to be added to a forced-air furnace and utilize
the existing blower.
3. Will I have to add insulation to my
home if I install one of these systems? Geothermal
heat pumps will reduce your heating and cooling costs regardless
of how well your home is insulated. However, insulating
and weatherizing are key factors in realizing the most savings
from any type of heating and cooling system.
4. Can a geothermal
heat pump also heat water? Yes. Using what's called
a desuperheater, some types of geothermal heat pumps can
save you up to 50 percent on your water-heating bill by
preheating tank water. Desuperheaters are standard on some
units, optional on others. Some geothermal models can provide
all of your hot water needs on demand at the same high efficiencies
as the heating/cooling cycles.
5. Is a geothermal heat pump difficult
to install? Most units are easy to install, especially
when they are replacing another forced-air system. They
can be installed in areas unsuitable for fossil fuel furnaces
because there is no combustion, thus, no need to vent exhaust
gases. Ductwork must be installed in homes that don't have
an existing air distribution system. The difficulty of installing
ductwork will vary and should be assessed by a contractor.
6. Can geothermal
heat pump be added to my fossil fuel furnace? Split
systems can easily be added to existing furnaces for those
wishing to have a dual-fuel heating system. Dual-fuel systems
use the heat pump as the main heating source and a fossil
fuel furnace as a supplement in extremely cold weather if
additional heat is needed.
7. I have ductwork, but will it work with
this system? In all probability, yes. Your installing
contractor should be able to determine ductwork requirements
and any minor modifications if needed.
8. Do I need to
increase the size of my electric service? Geothermal
heat pumps don't use large amounts of resistance heat, so
your existing service may be adequate. Generally, a 200-amp
service will have enough capacity, and smaller amp services
may be large enough in some cases. Your electric utility
or contractor can determine your service needs.
9. Should I buy
a heat pump large enough to heat with no supplemental heat?
Your contractor should provide a heating and cooling load
calculation (heat loss, heat gain) to guide your equipment
selection. Geothermal heat pumps are sized to meet your
cooling requirements. Depending on your heating needs, a
geothermal heat pump will supply 80-100 percent of your
design heating load. Sizing the heat pump to handle your
entire heating needs may result in slightly lower heating
costs, but the savings may not offset the added cost of
the larger heat pump unit. Also, an oversized unit can cause
dehumidification problems in the cooling mode, resulting
in a loss of summer comfort.
10. Do geothermal
heat pumps have outdoor units? No. The equipment
goes inside your home, usually in the basement, garage,
crawl space, or mechanical room. Because it's indoors, the
life spans of the compressor and major components are greatly
extended, most having a life span of 20 years or more.
11. The Mechanics
of the Heat Pump Process Anyone who has a refrigerator
or an air conditioner has witnessed the operation of a heat
pump, even though the term heat pump may be unfamiliar.
All of these machines, rather than making heat, take existing
heat and move it from a lower temperature location to a
higher temperature location. Refrigerators and air conditioners
are heat pumps which remove heat from colder interior spaces
to warmer exterior spaces for cooling purposes. Heat pumps
also move heat from a low-temperature source to a high-temperature
space for heating.
An air-source heat pump, for example, extracts heat from
outdoor air and pumps it indoors. A geothermal heat pump
works the same way, except that its heat source is the warmth
of the earth.
The process of elevating low-temperature heat to over 100°F
and transferring it indoors involves a cycle of evaporation,
compression, condensation and expansion. A refrigerant,
like Freon, is used as the heat-transfer medium which circulates
within the heat pump.
The cycle starts as the cold, liquid refrigerant passes
through a heat exchanger (evaporator) and absorbs heat from
the low-temperature source (liquid from the ground loop).
The refrigerant evaporates into a gas as heat is absorbed.
The gaseous refrigerant then passes through a compressor
where the refrigerant is pressurized, raising its temperature
to over 180°F. The hot gas then circulates through a
refrigerant-to-air heat exchanger where heat is removed
and pumped into the building at about 100°F. When it
loses the heat, the refrigerant changes back to a liquid.
The liquid is cooled as it passes through an expansion valve
and begins the process again. To become an air conditioner,
the flow is reversed.