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some local codes may limit its' use in earth loops. To
increase safety, a premixed form should be used on the
jobsite to increase the safety factor. Pure methanol can be
purchased from any chemical supplier.
Ethanol - Ethanol or grain alcohol exhibits good heat
transfer (slightly less than methanol), higher price, and is
flammable in concentrations greater than 10%. Ethanol is
generally non-corrosive and has medium viscosity.
Ethanol in its pure form is considered nontoxic and
shows promise as a geothermal heat transfer fluid,
however the U.S. Bureau of Alcohol, Tobacco, and
Firearms (ATF) limit its distribution. All non-beverage
ethanol is required to be denatured and rendered unfit to
drink. Generally this is done by adding a small
percentage of toxic substances such as methanol,
benzene, or gasoline as a denaturant. Many of these
denaturants are difficult to identify by the casual user and
many are not compatible with polyethylene pipe. Only
denatured ethanol can be purchased for commercial use.
HCI does not recommend the use of ethanol because of the
unknown denaturants included and their possible toxicity
and damage resulting to polyethylene piping systems.
Ethylene glycol - Generally non-corrosive, expensive,
medium heat transfer, however is considered toxic. Its
toxicity has prevented its widespread use in the ground
source industry in spite of its widespread use in traditional
watersource heat pump applications. We do not currently
recommend ethylene glycol as a ground source antifreeze.
It his highly recommended to utilize premixed antifreeze
fluid where possible to alleviate many installation
problems and extra labor.
The following procedure is based upon pure methanol
and can be implemented during the Full Flush procedure
with three way valves in the Figure 8D - Valve Position
D. If a premixed methanol of 15 F freeze protection is
used, the system can be filled and flushed with the
premix directly to prevent handling pure methanol
during the installation.
1) Flush loop until all air has been purged from system
and pressurize to check for leaks before adding any
antifreeze.
2) Run discharge line to a drain and hook up antifreeze
drum to suction side of pump (if not adding below
water level through approved container). Drain flush
reservoir down to pump suction inlet so reservoir can
accept the volume of antifreeze to be added.
3) Calculate the amount of antifreeze required by first
calculating the total fluid volume of the loop from
Table 3. Then using Table 4 for the appropriate freeze
protection level. Many southern applications require
freeze protection because of exposed piping and flow
controller ambient conditions.
ANTIFREEZE CHARGING
8
Propylene glycol - Nontoxic, non-corrosive, expensive,
hard to handle when cold, poorest heat transfer, has
formed "slime-type" coatings inside pipe. Poor heat
transfer has required its removal in some systems.
Propylene glycol (PG) is acceptable in systems anticipating
loops temperatures no colder than 40 F. these systems
typically are antifreeze because of ambient conditions
(outside plumbing or cooling tower, etc.). When loop
temperatures are below 40 F the fluid becomes very
difficult to pump and heat transfer characteristics suffer
greatly. We recommend only food grade propylene
glycol be used to prevent the corrosion inhibitors (often
present in other mixtures) from reacting with local water
and 'coming' out of solution to form slime type coatings
inside heat exchangers and thus hinder heat transfer.
GS4 (Potassium acetate) - Nontoxic, good heat transfer,
high price, non-corrosive with added inhibitors, low
viscosity. Due to its low surface tension, GS4 has been
known to leak through mechanical fittings and certain
thread sealants. A variant of the salt family, it can be
extremely corrosive when exposed to air. We do not
recommend the use of GS4 with its products due to the
leaking and (ultimately) corrosion problems associated
with it.
Table 3 - Fluid Volume of Common Piping Materials
Fluid Volume (gal/100' pipe)
Pipe
Copper
Rubber Hose
Polyethylene
Unit Heat Exchanger Typical
Flush cart tank
10" diam x 3 ft
Size
Volume
1"
1.25"
1.5"
1"
3/4" IPS SDR11
1" IPS SDR11
1-1/4" IPS SDR11
1-1/2" IPS SDR11
10.9
2" IPS SDR11
18.0
1-1/4" IPS SCH40
1-1/2" IPS SCH40
10.9
2" IPS SCH40
17.0
10.0
4.1
6.4
9.2
3.9
2.8
4.5
8.0
8.3
1.0
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