Direct
Exchange
Heat
Pumps
Our heat
pumps are
based on
direct
exchange”
technology,
often
referred to
as "DX
geothermal."
We believe
DX is the
right heat
pump
technology
for many
heating and
cooling
applications.
In DX
geothermal,
refrigerant
is
circulated
through
highly
conductive
copper earth
loops buried
in the
earth,
enabling the
direct
transfer of
thermal
energy from
the earth to
the building
(or the
swimming
pool, for
example). A
few feet
below the
surface, the
earth
remains at a
stable
temperature
throughout
the year; in
New England
this is
about 55
degrees
Fahrenheit.
In the
summer
months, the
heat pump
operates
like the
compressor
in an
ordinary
refrigerator
or an
automobile
air
conditioner;
it transfers
heat from
the building
to the
earth, and
thus cools
the
building. In
the winter,
the pump's
action is
reversed,
and it
transfers
heat from
the earth to
the
building,
providing
comfort in
the coldest
weather.
These
devices are
remarkably
efficient.
According to
U.S.
Department
of Energy
sources,
they provide
three to
four units
of energy
for every
unit of
electrical
energy used
to run them
(see
Coefficient
of
Performance
figures
below).
Geothermal
Heat Pumps
come in six
sizes: 2
tons; 2.5
tons; 3
tons; 3.5
tons; 4
tons, and 5
tons. All
require 220
volts.
Specifications
are listed
in the table
that
follows: |
| Model |
Cooling
Capacity (Btuh) |
Cooling EER Btuh/Watt
|
HeatingCapacity
Btuh |
Coefficient
of Performance |
Cabinet
Dimensions |
DXG 240A
|
28,000 |
16.6 |
25,000 |
3.7 |
23.5w X 22.5”d X 28.5”h
|
DXG 300A
|
33,000 |
16.6 |
30,000 |
3.7 |
23.5w X 22.5”d X 28.5”h |
DXG 360A
|
39,000 |
16.6 |
36,000 |
3.7 |
23.5w X 22.5”d X 28.5”h |
DXG 420A
|
45,000 |
16.6 |
42,000 |
3.7 |
23.5w X 22.5”d X 28.5”h |
DXG 480A
|
51,000 |
16.6 |
49,000 |
3.7 |
23.5w X 22.5”d X 28.5”h |
DXG 600A
|
64,000 |
16.6 |
61,000 |
3.7 |
23.5w X 22.5”d X 28.5”h |
Installing Direct Exchange Geothermal Systems
DX geothermal installations can be done in several ways: vertical, horizontal, or in a trench configuration.
- Vertical method. This method involves drilling three-inch diameter holes in the earth near the building with a small drilling machine and installing small-diameter copper pipe loops in each hole. For each "ton" of heating/cooling capacity required, two 50-foot holes are drilled and copper loops and a grout that remains flexible are inserted. A 2,500 square foot home, for example, might require four "tons" and therefore eight 50-foot loops, joined together through a central station called a manifold or distributor.
- Diagonal method. This is a variation on the vertical method. It requires somewhat longer copper loops.
- Horizontal method. In this method, copper pipes are buried two or three feet below the frost line in a series of underground trenches.
- Trench method. A third method involves digging a deeper and wider pit, and inserting spiral loops of copper into it.
- The best method to use depends on the particular configuration of your property.
Whichever installation method is chosen, the copper tubes in the ground are connected to a manifold or distributor. The distributor is connected to the heat pump inside the building. The heat pump transfers energy between the earth and the building; the system heats the building in the winter and cools it in the summer. (The heat pump can also help heat the building's hot water, and does so at virtually no cost in summer.) After the drilling or excavating is done and the copper loops are inserted, the landscaping is returned to its normal state.
Installing the small and quiet heat pump and connecting it to the earth loops is not difficult for a properly trained heating/cooling installer. But it is important that the system be sized and designed correctly. Once properly installed, the heat pump system requires little or no maintenance. |
Water Source Geothermal Heat Pumps
Another geothermal technology called the water-source or "intermediate loop" heat pump, is familiar to many people. This type of heat pump is somewhat more complicated than the GeoDirect™ DX system. It is more expensive to install, and uses somewhat more electricity to operate. The water-source heat pump accesses the earth’s stable temperatures by way of an intermediate fluid traveling through a plastic loop, using a circulating pump as well as an additional heat exchanger. The drilling involved in installing water source systems is more extensive. These heat pumps are particularly well suited to use in large buildings, and are an alternative to DX systems, particularly in new construction of smaller ones.
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Other Renewable Energy Technologies
While we do not manufacture them, we recommend that people doing new construction consider the use of SIPs (structural insulated panels) as a substitute for traditional construction materials. These panels can be made to order to fit any construction need and offer superior strength, superior insulating properties, greatly reduced waste, and greatly reduced time to completion.
It is also important to insulate and prevent air infiltration in older buildings. Foam insulation is a very useful (though still expensive) approach to this problem.
We also keep abreast of another renewable energy technology that is becoming increasingly practical: photovoltaic panels that convert the sun's energy directly to electricity, and can be tied to the electric company's "grid." The energy that is not used is sold back to the electric company by the homeowner or business, and helps offset the cost of whatever electrical energy is being used for heating, cooling, lighting, etc. Photovoltaic panels are relatively uncomplicated to install. PV panels are still expensive, however, and their efficiency depends on the building’s location and orientation. Improvements in efficiency and cost-effectiveness are, however, expected within the next few years. We view this technology as a worthwhile adjunct to the use of geothermal energy.
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