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Application Considerations
9
RLC-PRC005-E4
Certain application constraints should
be considered when sizing, selecting,
and installing Trane air-cooled Series R
chillers. Unit and system reliability is
often dependent on properly and
completely complying with these
considerations. When the application
varies from the guidelines presented, it
should be reviewed with your local
Trane sales engineer.
Unit Sizing
Unit capacities are listed in the
performance data section. Intentionally
oversizing a unit to ensure adequate
capacity is not recommended. Erratic
system operation and excessive
compressor cycling are often a direct
result of an oversized chiller. In addition,
an oversized unit is usually more
expensive to purchase, install, and
operate. If oversizing is desired, consider
using two units.
Water Treatment
Dirt, scale, products of corrosion, and
other foreign material will adversely
affect heat transfer between the water
and system components. Foreign matter
in the chilled-water system can also
increase pressure drop and,
consequently, reduce water flow. Proper
water treatment must be determined
locally, depending on the type of system
51°C [125°F], and selecting the low-
ambient option will increase the
operational capability of the water chiller
to ambient temperatures as low as 18°C
[0°F]. For operation outside of these
ranges, contact the local Trane sales
office.
Water Flow Limits
The minimum water flow rates are
given in Tables G-1 and G-2. Evaporator
flow rates below the tabulated values
will result in laminar flow and cause
freeze-up problems, scaling,
stratification, and poor control. The
maximum evaporator water flow rate is
also given in the general data section.
Flow rates exceeding those listed may
result in excessive tube erosion.
Flow Rates Out of Range
Many process cooling jobs require flow
rates that cannot be met with the
minimum and maximum published
values within the Model RTAC
evaporator. A simple piping change can
alleviate this problem. For example: a
plastic injection molding process
requires 5.0 Lps [80 gpm] of 10°C [50°F]
water and returns that water at 15.6°C
[60°F]. The selected chiller can operate at
these temperatures, but has a minimum
flow rate of 7.6 Lps [120 gpm]. The
following system can satisfy the process.
and local water characteristics. Neither
salt nor brackish water is recommended
for use in Trane air-cooled Series R
chillers. Use of either will lead to a
shortened chiller life. The Trane
Company encourages the employment
of a reputable water-treatment specialist,
familiar with local water conditions, to
assist in this determination and in the
establishment of a proper water-
treatment program.
Effect of Altitude on Capacity
Air-cooled Series R chiller capacities
given in the performance data tables are
for use at sea level. At elevations
substantially above sea level, the
decreased air density will reduce
condenser capacity and, therefore, unit
capacity and efficiency. The adjustment
factors in Table F-1 can be applied
directly to the catalog performance data
to determine the unit’s adjusted
performance.
Ambient Limitations
Trane air-cooled Series R chillers are
designed for year-round operation over
a range of ambient temperatures. The
air-cooled Model RTAC chiller will
operate in ambient temperatures of 4 to
46°C [25 to 115°F]. Selecting the high-
ambient option will allow the chiller to
operate in ambient temperatures of
10°C
7.6 Lps
13.7°C
7.6 Lps
CV pump
7.5 Lps
10°C
2.5 Lps
CV Pump
5 Lps
10°C
5 Lps
15.6°C
5 Lps
Figure 4 — GPM Out of Range
Load