Application Considerations - Trane CGAX/CXAX Manual

Certain applications contraints should be considered
when sizing, selecting and installing Conquest air-
cooled Scroll chillers. Unit and system reliability often
depend on proper and complete compliance with those
considerations.
Unit Size
Unit oversizing is often not recommended since erratic
unit operation and excessive compressor cycling are
often a direct result of an oversized chiller. If oversizing
is desired, consider the alternative of multiple units,
splitting the total capacity.
Water Treatment
The use of untreated or improperly treated water in
chillers may result in scaling, erosion, corrosion, and
algae or slime buildup. This will adversely affect heat
transfer between the water and system components.
Proper water treatment must be determined locally
and depends on the type of system and local water
characteristics.
Neither salty nor brackish water is recommend for use
in Trane air-cooled Conquest chiller. Usage of either
will lead to a shortened life. Trane encourages the
employment of a qualifi ed water treatment specialist,
familiar with local water conditions, to assist in the
establishment of a proper water treatment program.
Foreign matter in the chilled water system can also
increase pressure drop and, consequently, reduce water
fl ow. For this reason it is important to thoroughly fl ush
all water piping to the unit before making the fi nal piping
connections to the unit.
Effect of the altitude on the cooling capacity
At elevations substantially above sea level, the
decreased air density will decrease condenser capacity
and, therefore, unit capacity and effi ciency.
Water fl ow limits
The minimum water fl ow rates are given in the General
Data section of this catalog. Evaporator fl ow rates below
the tabulated values will result in laminar fl ow causing
freeze-up problems,scaling, stratifi cation and poor
control. The maximum evaporator water fl ow rate is also
given. Flow rates exceeding those listed may result in
very high pressure drop across the evaporator.
Flow Rates Out of Range
Many process cooling jobs require fl ow rates that cannot
be met with the minimum and maximum published
values within the Conquest chiller evaporator. A simple
piping change can alleviate this problem. For example:
a plastic injection molding process requires 5.0 l/s of
10°C water and returns that water at 15.6°C. The selected
chiller can operate at these temperatures, but has a
minimum fl ow rate of 6.6 l/s. The system layout in
Figure 7 can satisfy the process.
CG-PRC026C-GB

Application Considerations

Figure 7 - Flow rate out of range systems solution
10°C
5 l/s
10°C
7 l/s
10°C
2 l/s
14°C
7 l/s
L = Load
P = Pump
Flow Proving
Trane provides a factory-installed water fl ow switch
monitored by chilller controller CH535 which protects the
chiller from operating in loss of fl ow conditions.
Leaving Water Temperature Limits
Trane air-cooled Conquest chillers have two distinct
leaving water categories:
• standard, with a leaving solution range of 5.5 to 18°C
• low temperature process cooling, with leaving solution
range of -12 to 18°C
Since the leaving solution temperature below 5.5°C
results in suction temperature at or below the freezing
point of water, a glycol solution is required for all low
temperature.
Consult your local Trane sales engineer for applications
or selections involving low temperature. The maximum
water temperature that can be circulated through the
CGAX evaporator when the unit is not operating is
51.7°C. For the model CXAX the water temperature
limit is 60°C. Evaporator damage may result above this
temperature.
Figure 8 - Temperature out of range system solution
15°C
3.8 l/s
15°C
15 l/s
15°C
11.2 l/s
20°C
15 l/s
P
35°C
3.8 l/s
L = Load
P = Pump
15.6°C
5 l/s
30°C
15 l/s
P
35°C
11.2 l/s
35°C
15 l/s
L
7