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Operating Procedures
Maintain Glycol Level
When the chiller has a water set point that is below the
freezing point of the water/glycol in use, take precautions
against freezing.
Table 24. Glycol performance impact factors
Range Factor
Propylene Glycol
Concentration
Lowest Ambient Temperature
Recommended Minimum
Leaving Fluid Temperature
Leaving Temperature
70 °F (21 °C)
60 °F (15.6 °C)
55 °F (13 °C)
50 °F (10 °C)
A 20% 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
62
Glycol Concentration Percentages and Performance Impact
30%
10 °F (-12 °C)
25 °F (-4 °C)
Capacity
Pressure Drop
Reduction Factor
Factor
0.96
1.27
0.95
1.31
0.95
1.31
0.94
1.33
The glycol concentration should be based on the lowest
fluid design temperature. See
guidelines for adding propylene glycol.
40%
-4 °F (-10 °C)
10 °F (-12 °C)
Capacity
Pressure Drop
Reduction Factor
Factor
0.93
1.43
0.92
1.47
0.92
1.50
0.91
1.51
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.
Table 25, p. 63
provides
50%
-20 °F (-29 °C)
-10 °F (-23 °C)
Capacity
Pressure Drop
Reduction
Factor
Factor
0.91
1.63
0.90
1.68
0.89
1.73
0.88
1.75
ARTC-SVX014A-EN
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