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Enertech Global IOM, XT Models
Antifreeze Overview
In areas where minimum entering loop temperatures
drop below 40°F, or where piping will be routed
through areas subject to freezing, antifreeze is
required. Alcohols and glycols are commonly used
as antifreeze. However, local and state/provincial
codes supersede any instructions in this document.
The system needs antifreeze to protect the coaxial
heat exchanger from freezing and rupturing. Freeze
protection should be maintained to 15°F below the
lowest expected entering source loop temperature.
For example, if 30°F is the minimum expected
entering source loop temperature, the leaving
source loop temperature could be 22 to 25°F. Freeze
protection should be set at 15°F (30-15 = 15°F). To
determine antifreeze requirements, calculate how
much volume the system holds. Then, calculate how
much antifreeze will be needed by determining
the percentage of antifreeze required for proper
freeze protection. See Tables 4 and 5 for volumes
and percentages. The freeze protection should
be checked during installation using the proper
hydrometer to measure the specic gravity and
freeze protection level of the solution.
Antifreeze Characteristics
Selection of the antifreeze solution for closed loop
systems require the consideration of many important
factors, which have long-term implications on the
performance and life of the equipment. Each area
of concern leads to a different “best choice” of
antifreeze. There is no “perfect” antifreeze. Some
of the factors to consider are as follows (Brine =
antifreeze solution including water):
Safety: The toxicity and ammability of the brine
(especially in a pure form).
Cost: Prices vary widely.
Thermal Performance: The heat transfer and viscosity
effect of the brine.
Corrosiveness: The brine must be compatible with
the system materials.
Stability: Will the brine require periodic change out
or maintenance?
Convenience: Is the antifreeze available and easy
to transport and install?
Codes: Will the brine meet local and state/provincial
codes?
The following are some general observations about
the types of brines presently being used:
Methanol: Wood grain alcohol that is considered
toxic in pure form. It has good heat transfer, low
viscosity, is non-corrosive, and is mid to low price.
The biggest down side is that it is ammable in
concentrations greater than 25%.
Ethanol: Grain alcohol, which by the ATF (Alcohol,
Tobacco, Firearms) department of the U.S.
government, is required to be denatured and
rendered unt to drink. It has good heat transfer,
mid to high price, is non-corrosive, non-toxic
even in its pure form, and has medium viscosity.
It also is ammable with concentrations greater
than 25%. Note that the brand of ethanol is very
important. Make sure it has been formulated for
the geothermal industry. Some of the denaturants
are not compatible with HDPE pipe (for example,
solutions denatured with gasoline).
Section 5: Unit Piping Installation
Flushing the Interior Piping (Non-Pressurized)
Do not use the ush cart to purge the interior piping
and ow center in a non-pressurized system. Once
the loop has been ushed the ball valves may be
opened above the ush ports. Take a garden hose
from the ush port connected to the water out to
the loop pipe, and run the other end of the hose
into the top of the canister. Fill the canister with
water and turn the pumps on. Continue to ll the
canister until the water level stays above the dip
tube. Once lling is complete, remove the hose
and close the ush port. Turn the system on. Any air
that may still be in the system will burp itself out of
the top of the canister. Leave the top open for the
rst 1/2 hour of run time to ensure that all of the air
is bled out. Tighten the cap on the ow center to
complete the ushing and lling procedure (hand
tighten only -- do not use a wrench).
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