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The addition of glycol to water yields a solution with a
freezing point below that of water. This has led to the
extensive use of glycol-water solutions as cooling media at
temperatures appreciably below the freezing point of water.
Instead of having sharp freezing points, glycol-water
solutions become slushy during freezing. As the
temperature falls, the slush becomes more and more
viscous and finally fails to flow.
Table 25. Freeze and burst protection chart
Water/Glycol
Freeze Protection
Temperature
20 °F (-7 °C)
18% glycol mixture
10 °F (-12 °C)
29% glycol mixture
0 °F (-17.8 °C)
36% glycol mixture
-10 °F (-23 °C)
42% glycol mixture
-20 °F (-29 °C)
46% glycol mixture
The precise concentration of glycol for a particular chiller is
affected by several key factors such as ambient
temperature extremes, entering and leaving water
temperatures, and chiller size. A chillers optimum glycol
concentration is modified by these considerations as
reflected in
Table 24, p.
62. These capacity correction
factors are the best informed estimates for chiller with
copper evaporators. The percentages may vary depending
on the materials and alloys of the heat exchangers, total
surface area, the amount of present or future fouling, and
the brand of glycol used.
Storage Provisions
The chiller controls are designed for storage in ambient
temperatures from -20 °F (-29 °C) to 145 °F (63 °C) with
relative humidity from 0% to 100%. The glycol should be
ARTC-SVX014A-EN
Burst Protection
12% glycol mixture
20% glycol mixture
24% glycol mixture
28% glycol mixture
30% glycol mixture
removed from the chiller if the unit is to be stored for
extended periods. Although fluids can be drained via the
plug in the bottom of the evaporator, the inhibitors in an
approved glycol solution will best protect the surfaces of
the evaporator against oxidation if the glycol remains inside
the chiller during storage.
Figure 31. Water/Glycol concentration freezing points
(in degrees Fahrenheit)
Operating Procedures
63
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