Enertech Global, LLC
17
WS Rev. E Models
Installation and Operations Manual
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 heat
exchanger from freezing and rupturing. Freeze protection
should be maintained to 15°F below the lowest expected
entering loop temperature. For example, if 30°F is the
minimum expected entering loop temperature, the leaving
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 Pipe Fluid Volume and Antifreeze
Percentages by Volume Tables on the next page page for
volumes and percentages. The freeze protection should be
checked during installation using the proper hydrometer to
measure the specific 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 flammability 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 flammable 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 unfit 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 flammable
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).
Propylene Glycol:
Non-toxic, non-corrosive, mid to high price,
poor heat transfer in high concentrations, and potential for
high viscosity when cold (in high concentrations). It has also
been known to form a “slime-type” coating inside the pipe
when inhibitors are not used. Do not use food grade glycol,
since it does not include inhibitors. A 25% to 30% brine
solution is a minimum concentration for required inhibitors,
depending upon brand of glycol. If using a lower
concentration (e.g. 20% provides 19°F freeze protection),
additional inhibitors must be added. Note that some states/
provinces have toxicity requirements that must be verified
based upon the chemical composition of the inhibitors.
Ethylene Glycol:
Considered toxic and is not recommended
for use in earth loop applications.
Antifreeze Charging
Calculate the total amount of pipe in the system and use the
Pipe Fluid Volume Table
to calculate the amount of volume
for each specific section of the system. Add the entire volume
together, and multiply that volume by the proper antifreeze
percentage needed
(See Antifreeze Percentages by Volume)
for the freeze protection required in your area. Then, double
check calculations during installation with the proper
hydrometer and specific gravity chart
(See Antifreeze Specific
Gravity Table
) to determine if the correct amount of
antifreeze was added.
⚠
CAUTION
⚠
GROUND LOOPS MUST BE ANTIFREEZE PROTECTED.
INSUFFICIENT AMOUNTS OF ANTIFREEZE MAY
CAUSE SEVERE DAMAGE AND MAY VOID
WARRANTY.
⚠
WARNING
⚠
USE EXTREME CARE WHEN OPENING, POURING,
AND MIXING FLAMMABLE ANTIFREEZE SOLUTIONS.
REMOTE FLAMES OR ELECTRICAL SPARKS CAN
IGNITE UNDILUTED ANTIFREEZES AND VAPORS. USE
ONLY IN A WELL VENTILATED AREA. DO NOT SMOKE
WHEN HANDLING FLAMMABLE SOLUTIONS. FAILURE
TO OBSERVE SAFETY PRECAUTIONS MAY RESULT IN
FIRE, INJURY, OR DEATH. NEVER WORK WITH 100%
ALCOHOL SOLUTIONS.
Section 6: Antifreeze