Operating Procedures
48 ARTC-SVX005A-EN
The glycol concentration should be based on the lowest
fluid design temperature. See Table 11, p. 49, provides
guidelines for adding propylene glycol.
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.
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 and
tank and pump modules 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.
Freeze points and burst points of glycol-water solutions
are shown in Table 10, p. 48.
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. Trane can
provide concentrated solutions of Dowfrost, propylene
glycol, or premixed solutions for use with the chiller.
Propylene Glycol
Important: 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/
heater. If the concentration of glycol is
sufficient, no damage to the chiller/heater
from fluid expansion should occur within
the temperature range indicated in
Figure 28, p. 49. 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
Table 10. Glycol performance impact factors
Range Factor Glycol Concentration Percentages and Performance Impact
Propylene Glycol Concentration 30% 40% 50%
Lowest Ambient Temperature 10 °F (-12 °C) -4 °F (-10 °C) -20 °F (-29 °C)
Recommended Minimum
Leaving Fluid Temperature
25 °F (-4 °C) 10 °F (-12 °C) -10 °F (-23 °C)
Leaving Temperature
Capacity
Reduction
Factor
Pressure Drop
Factor
Capacity
Reduction
Factor
Pressure Drop
Factor
Capacity
Reduction
Factor
Pressure Drop
Factor
70 °F (21 °C) 0.96 1.27 0.93 1.43 0.91 1.63
60 °F (15.6 °C) 0.95 1.31 0.92 1.47 0.90 1.68
55 °F (13 °C) 0.95 1.31 0.92 1.50 0.89 1.73
50 °F (10 °C) 0.94 1.33 0.91 1.51 0.88 1.75
NOTICE
Equipment Damage!
Failure to follow instructions below could result in
permanent damage to pump and internal cooling
surfaces. Do not use automotive antifreeze.
NOTICE
Equipment Damage!
Failure to follow instructions below could result in
permanent damage to pump and internal cooling
surfaces. Do not use automotive antifreeze.
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