ARTC-SVX007A-EN
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A 10% to 50% solution of glycol should be added to
prevent pipe corrosion regardless of the fluid temperature.
Propylene glycol has corrosion inhibitors that protect piping
and components from corrosion and buildup of rust and
other deposits. Trane recommends against using water/
glycol solution in excess of 50% regardless of the ambient
temperature conditions.
NOTICE
Equipment Damage!
Failure to follow instructions below could result in
permanent damage to pump and internal cooling
surfaces.
Do not use automotive antifreeze.
Note: If glycol-free solutions are mandated at the chiller
site, special inhibitors are available for rust
prevention, mineral deposit inhibition, and biological
suppression. Adding these inhibitors to the water
solution is strongly recommended.
Heaters, heat tracing cable, and closed cell insulation can
be installed on any exposed "wet" chiller components for
protection against freezing in low ambient temperature and
low refrigerant pressure conditions. However, the best
freeze prevention is using the appropriate concentration of
glycol. Trane does not warranty any component that fails
due to freezing.
Prevent Freezing
Many liquids expand in volume upon cooling. This
expansion may cause pipes and other enclosed systems
containing a liquid to rupture or burst when exposed to low
temperature conditions. Burst protection is needed to
protect piping and other enclosed systems when they are
inactive as they could rupture due to expansion during cold
weather or low refrigerant pressure.
In order to maintain a high-quality glycol solution, the water
used in the glycol mixture must have very few impurities.
Impurities in the water can increase metal corrosion,
aggravate pitting of cast iron and steel, reduce the
effectiveness of the corrosion inhibitors, and increase the
depletion rate of the inhibitor package.
To assure inhibitor effectiveness, the levels of chlorides
and sulfates in the water should not exceed 25 ppm each.
The total hardness in terms of calcium carbonate should be
less than 100 ppm. For best long-term results, de-ionized
or distilled water is recommended.
Propylene Glycol
Glycol-based fluids provide such burst protection in water
solutions due to their low freezing points. As a glycol-based
fluid cools below the solution’s freezing point, ice crystals
begin to form, and the remaining solution becomes more
concentrated in glycol. This ice/water/glycol mixture results
in a flowable slush, and remains fluid, even as the
temperature continues to cool.
The fluid volume increases as this slush forms and the
temperature cools, flowing into available expansion volume
in the chiller. If the concentration of glycol is sufficient, no
damage to the chiller from fluid expansion should occur
within the temperature range indicated in . When liquids are
cooled, they eventually either crystallize like ice or become
increasingly viscous until they fail to flow and set up like
glass. The first type of behavior represents true freezing.
The second is known as super-cooling.
Glycols do not have sharp freezing points. Under normal
conditions, propylene glycol sets to a glass-like solid, rather
than freezing.
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 18. Freeze and burst protection chart
Water/Glycol
Temperature
Freeze Protection Burst Protection
20 °F (-7 °C) 18% glycol mixture 12% glycol mixture
10 °F (-12 °C) 29% glycol mixture 20% glycol mixture
0 °F (-17.8 °C) 36% glycol mixture 24% glycol mixture
-10 °F (-23 °C) 42% glycol mixture 28% glycol mixture
-20 °F (-29 °C) 46% glycol mixture 30% 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 chiller’s optimum glycol
concentration is modified by these considerations as
reflected in Table 17, p. 54. 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
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.
Operating Procedures
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