Table of Contents
Advertisement
Operating Procedures
Maintain Glycol Level
The temperature of the refrigerant in a brazed plate
evaporator is not uniform throughout the heat exchanger.
The refrigerant temperature is approximately 6 °F to 12 °F
colder than the corresponding fluid temperature depending
on many factors such as the heat exchanger design, glycol
Table 16. 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/
heat pump 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/heat pump
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
50
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
percentage, operating fluid temperatures, refrigerant,
system flow rate, etc. When the chiller/heat pump has a set
point that is within 12 °F (6.7 °C) of the freezing point of the
water/glycol in use, take precautions against freezing. See
Table below for the recommended glycol concentrations
and performance impact.
40%
-4 °F (-20 °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
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 17, p.
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/heat pump.
Equipment Damage!
Failure to follow instructions below could result in
permanent damage to pump and internal cooling
surfaces.
Do not use automotive antifreeze.
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 solutions freezing point, ice crystals
begin to form, and the remaining solution becomes more
50%
-20 °F (-29 °C)
-10 °F (-23 °C)
Capacity
Pressure Drop
Reduction
Factor
Factor
0.91
0.90
0.89
0.88
51.
NOTICE
ARTC-SVX010A-EN
1.63
1.68
1.73
1.75
Advertisement
Table of Contents
