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One of the primary advantages of CLVB systems is that the
systems do not
rely on an aquifer. Our systems will function in any kind of geological
formation, therefore hitting water when drilling is not vital. This removes a lot of
the uncertainty, and potential expense, when drilling.
In addition, once a CLVB system is installed, it gets filled with a clean supply
of water/glycol that will recirculate for years, with no addition of silt,
sand or minerals that you would potentially obtain from a well-based system.
This results in less scaling and contamination in the heat pumps and far greater
reliability.
Furthermore, with a closed system, the circulator pumps can be significantly
smaller, typically 1/26 to 1/13 hp units, rather than the 1/2 and 3/4 hp well
pumps required with water well type systems. Not only does this reduce the
initial investment, but the energy consumption of the system as well.
Because we use a much smaller drill than the typical water well drill, the
impact on your property is significantly reduced. Our air type TEI Rock Drill
uses a " down the hole hammer" or DTH. This type of drilling is extremely well
suited to the granite formations here in the Northeast, and is most commonly
used in the quarry and blasting industries. Naturally, should your system
require it, we can provide well-type drills.
Typically, in a CLVB system, we drill 3-4" wide holes, about 100' in depth
about 20' feet apart, until there are enough vertical bores to handle the
capacity of the installed heat pumps plus the heat loss of the building. Our
design software calls for about 150' of borehole per ton of heat pump when
drilling into granite. We call this type of installation a "Mini-Borefield".
Into each of these holes we drop a loop of 3/4" HDPE pipe. The HDPE
tubing is heat fused to
IGSHPA procedure and the bores
are grouted using special Bentonite Geothermal Grout to provide maximum heat transfer. The system is then filled with a 15% food grade
propylene glycol anti freeze/water solution for maximum thermal transfer
efficiency and freeze protection. |
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Closed Loop Vertical Bore Systems involve no exchange of
groundwater. This type of system, while considered a well for DEP purposes, is
not subject to testing requirements; only a Geothermal Registration Form needs
to be filed with the state. The Department of Environmental Protection provides
a supplemental geothermal well information form at:
http://maine.gov/dep/blwq/docstand/uic/geothermal.pdf.
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The Maine Department of Environmental Protection requires all
geothermal systems to be registered, and if they are water well systems, tested
for a variety of elements and chemicals and pollutants such as Gas,
Diesel, Volatile Organic Compounds (VOCs), Arsenic, Uranium, Manganese, and
other chemicals that naturally occur in the ground water. A water well
system test costs approximately $550.00 It is the owner's responsibility to register their installation
and submit test data prior to using the system
There are many occasions where a Standing Column Well (SCW) is a preferable
choice for a geothermal system. Normally, if a client is building a home, needs a
well drilled anyway, and has a good location for disposing of bleed water, an SCW is often the right choice. It is very economical to use the well as both
the heat and domestic water supply. SCW systems have excellent performance
numbers, as long as the wells are drilled deep enough and have enough "wet
hole" per ton of heat pump capacity. Most Standing Column Wells systems will
require about 80' of standing water per ton of heat pump capacity.
Many wells are capable of supplying huge amounts of water, and if the client
is willing to test their water, and has someplace to dump it where it will not
run into the groundwater, stream, or pond, they should consider an SCW
option. Open loop water well systems typically flow about 3 gallons per minute
per ton of heat pump, and this is a lot of water on the ground if it doesn't
have anywhere to drain. In the case of an SCW, only about 10-15% of the flow
goes out onto the ground. Most of the time, the bulk of the water will be dumped
back into the well. Typically, bleed water happens in the coldest months, to
keep the well from cooling or freezing. |
