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What is a
geothermal/geoexchange heat pump?
A
geothermal system is an electrically powered home comfort
system that uses the earth's stored energy to heat or cool
you home or business.
How does
it work?
The principles of a geothermal
system are the same as a normal heat pump. The geothermal
system simply moves heat from one place to another. The
geothermal system moves the heat from the earth to your home
in the winter and moves the heat from you home back to the
earth in the summer.
How
can a geothermal system transfer heat?
Earth has the ability to
absorb and retain heat. In the winter, heat is extracted
from the earth using water or an anti-freeze solution. In
the summer, heat is sent back to the earth through the same
water or anti-freeze that brought the stored heat to your
home in the winter. The operation of the geothermal system
(or any heat pump) is simply reversed to get the desired
effect of heating or cooling.
How
does it know when to heat and when to cool?
That is done through the same
basic thermostat you have used for years. A simple switch
and temperature setting from your indoor thermostat
determines the amount of heating or cooling.
What
methods are available to transferred the water?
Open loop and closed loop are
the two basic methods of moving the water or anti-freeze.
What
is a closed loop system?
Closed loop means that there
is one continuous loop of special material used to transfer
the water or anti-freeze solution from the geothermal down
into the earth and back to the geothermal. The water is
being re-circulated in a pressurized pipe instead of adding
new water.
Where
can I put this loop?
Depends
on the amount of space available on your property. You can
place the loops horizontally if there is a lot of land. Or
you can place the loops vertically if the amount of land is
limited. A pond or lake can even be used in some situations.
Which
loop is best?
There really isn't a "best"
loop configuration for every geothermal system. Best in some
areas is the vertical loop where drilling is easy and
inexpensive. Some rockier areas may be better suited for
horizontal looping. A pond or lake may be close enough to
use for some geothermal jobs.
How
much pipe is used for the loops?
There again, it depends on the
particular area you are putting the geothermal system. A
horizontal loop system normally needs 400 - 500 feet of pipe
per ton. This pipe is buried in trenches normally 4-6 feet
deep. The vertical loop normally takes 150 - 250 feet of
pipe per ton. A hole is drilled and the loop is placed in
the hole with a U-Bend to allow the water to circulate. Your
mechanical contractor can better determine what is
necessary.
What
kind of material is used for these loops?
Many different materials have
been used in the past with different degrees of success.
Currently, polyethylene is the most widely used material for
looping. PVC should never been used for any of the closed
loop piping.
How
does polyethylene loops get connected together?
The only acceptable method of
connecting piping is through heat fusion. Most fusion is
done around 510 degree's Fahrenheit using special tools and
irons just for geothermal piping. Barbs, screw fittings,
clamps and glued joints should never be used to join piping.
Loop failure is certain if heat fusion isn't used.
Will
the loops be visible or affect my lawn?
The loops shouldn't be visible and will not effect your
lawn. Initial installation will affect your lawn but will
not be visible once the grass has grown back.
(More info)
What
about freezing?
Your
mechanical contractor should be able to properly prepare
your geothermal system for freezing conditions. Anti-freeze
is available for climates needing freeze protection.
Can I
do the loops myself?
It isn't
recommended that an individual install their loops. The heat
fusion is critical for long life on the geothermal system.
Most manufactures require schooling on proper heat fusion
and earth-to-loop contact. Poor installation can result in
unsatisfactory performance and possible shortened equipment
life. The money saved (if any) will be overshadowed by an
uncomfortable home, higher than necessary utility bills, or
maintenance.
What
kind of warranty do I get with the loop?
50 - 55 years is the standard
warranty on the loop if the geothermal system is installed
by a licensed and certified mechanical contractor.
How
big are the pipes?
Normally,
¾" for the actual loop itself and 1¼" pipe going from the
geothermal unit to the loop field. This area is called a
header pit where the 1¼" ties into the ¾."
How
much water is in the loops?
¾" pipe
takes .028 gallons per foot. An average three ton loop in my
area would take approximately 40 gallons.
What
kind of temperatures can I expect in a closed loop system?
Temperatures range from the
40's in the northern states to the upper 90's in the more
southern states.
What
are the drawbacks to closed loop systems?
Cost is the main drawback to closed loop systems. Drilling
can be expensive in some areas of the country.
What
about using an open loop instead of a closed loop?
Open loop geothermal systems
have been used for years. Many areas no longer allow open
loop geothermal systems saying they are bad for the
environment since they may delete water supplies. Open loops
are actually a great source of heat transfer since ground
water stays relatively the same temperature year round.
What
are the drawbacks to open loop systems?
The main drawbacks are the amount of wasted water since 6 -
9 gallons is normal for an open loop system. Possible
mineral deposits can ruin a geothermal system causing major
repair bills.
How
hard is it to install a geothermal system?
The difficulty varies from
home to home. New construction is the easiest as long as
there is coordination between the homeowner, the builder,
and the mechanical contractor. Space is the only real
drawback to installing geothermal equipment since everything
is inside the home.
There
is no outside unit?
One of
the advantages of the geothermal system is the lack of the
outside unit. Many people enjoy the more pleasing landscape
with no outside unit to contend with. Also, the average life
expectancy is 20-25 years since the geothermal system
doesn't have to deal with outside temperatures.
What
about noise?
Geothermal systems are no
different than anything else you buy in life. Paying a
little now normally means you get less in return. A
well-built and properly installed geothermal unit will give
you years of quiet operation.
Can a
geothermal system heat water?
Yes. The
geothermal makes free hot water and can reduce your power
consumption for hot water up to 60% depending on the amount
of people using hot water in your home. Not only does the
system make hot water, in many situations it makes "more
than free" hot water. Meaning the unit actually becomes more
efficient when producing hot water.
Is
there a gas version of geothermal?
No. You
can add a split system geothermal system to a gas furnace.
This isn't normally done due to additional costs and lack of
any real savings on utility (gas and power) consumption.
Can I
use my existing ductwork?
Normally,
yes. Ductwork should be checked to verify that there isn't
any leakage and there is proper sizing. You should really
consider changing the duct system on any home comfort system
if there is a lot of leakage or you are up sizing your
system.
How
much supplemental heat will I need?
That depends on your heat loss calculation that your
mechanical contractor should be able to provide for you.
Many climates don't require any auxiliary heat. Over-sizing
the geothermal unit to meet your heating requirements will
cause dehumidification problems in the cooling mode. There
is no defrosting cycle with a geothermal system helping to
eliminate the need for auxiliary heat.
How
efficient is a geothermal heat pump?
Most geothermal systems are a minimum of three times more
efficient than fossil fuel systems. Geothermal simply moves
heat instead of actually making it. In some instances,
geothermal systems produce five units of heat to one unit of
electricity.
What
about the comfort levels with a geothermal system?
Geothermal systems have a good
reputation for giving the highest possible comfort for the
least amount of operating money. In the winter, heat
normally comes out between 90 and 105 degrees throughout
your home using a well-installed duct system.
How
much does a geothermal system cost?
Costs vary from region to region. The main difference in
cost is the loops. In Northwest Florida, most geothermal
systems cost about twice as much as a high efficiency gas or
air-to-air heat pump system. That kind of comparison isn't
really accurate though. You should also consider:
- Life
cycle cost. How long will normal heating/cooling systems
last? Typically, 12 years is the average. A geothermal
system normally lives twice that long.
- Operating
cost. Even the highest efficient heating/cooling system
can't compare to a geothermal system. Operating cost is
sometimes figured as "payback." Take the projected
operational cost of the systems comparing and see how long
it will take to recover your money. More comfortable
people will get payback quicker due to higher energy
consumption. Payback is typically 3-7 years depending on
local utility rates and initial cost.
-
Availability of resources. Be sure to look at the history
of utilities in your area. Geothermal becomes more
enticing the more rates change for electricity or gas.
-
Maintenance costs. What is the warranty time frame for all
systems being compared and how much does the mechanical
contractor anticipate your repair bills to be through the
years.
Do you
need to have a back up heating system with Geothermal?
No back up heat is typically
required. In fact, according to our records, we haven't
installed auxiliary back-up heat in a geothermal system
since August 1999. There really isn't a need for back-up
heat in a geothermal system since there isn't a defrost
cycle and outside temperatures does not impact geothermal
systems like it does air source heat pumps. (Added
10-10-02)
Is hot water generated in all
seasons or only in the summer when you are removing heat
from the house? Hot water is generated year
round but typically only 100% of your domestic hot water
will be generated 4-8 months out of the year. (Added
10-10-02 in regards to two people residing in the home)
What should I look for if I am
willing to make this kind of investment?
Ask for referrals. Don't be reluctant to request the
information where the mechanical contractor is basing the
size and projected operational cost. Also, ask what the
qualifications of the mechanical contractor are and how long
they have been in business and installing geothermal
systems. There really isn't a correct answer to the last
question, just an opportunity to get a feel on the
contractor.
Is
there a particular brand that is better than the rest?
Look for the best contractor
first. The best home comfort system will leave you
unsatisfied if installed incorrectly. A quality contractor
will avoid the equipment with bad reputations. Expect to pay
more and expect to get more. |
