Catalogue

8 RLC-PRC042D-EN
Application Considerations
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 RTAE evaporator. A simple piping change can alleviate this problem.
For example: a plastic injection molding process requires 80 gpm (5.0 l/s) of 50°F (10°C) water and
returns that water at 60°F (15.6°C). The selected chiller can operate at these temperatures, but has
a minimum flow rate of 106 gpm (6.6 l/s). The system layout in Figure 1 can satisfy the process.
Flow Proving
Trane provides a factory-installed water flow switch monitored by UC800 which protects the chiller
from operating in loss of flow conditions.
Water Temperature
Leaving Water Temperature Limits
Trane RTAE chillers have three distinct leaving water categories:
• Standard, with a leaving solution range of 40 to 68°F (4.4 to 20°C)
• Low temperature process cooling, with leaving solution less than 40°F (4.4°C)
• Ice-making, with a leaving solution range of 20 to 68°F (-6.7 to 20°C)
Since leaving solution temperatures below 40°F (4.4°C) result in suction temperature at or below
the freezing point of water, a glycol solution is required for all low temperature and ice-making
machines. Ice making control includes dual setpoints and safeties for ice making and standard
cooling capabilities. Consult your local Trane account manager for applications or selections
involving low temperature or ice making machines.
The maximum water temperature that can be circulated through the RTAE evaporator when the
unit is not operating is 125°F (52°C). Evaporator damage may result above this temperature.
Leaving Water Temperature Out of Range
Many process cooling jobs require temperature ranges that are outside the allowable minimum
and maximum operating values for the chiller. Figure 2 below shows a simple example of a mixed
water piping arrangement change that can permit reliable chiller operation while meeting such
cooling conditions. For example, a laboratory load requires 238 gpm (15 l/s) of water entering the
process at 86°F (30°C) and returning at 95°F (35°C). The chiller’s maximum leaving chilled water
temperature of 68°F (20°C) prevents direct supply to the load. In the example shown, both the chiller
and process flow rates are equal, however, this is not necessary. For example, if the chiller had a
higher flow rate, there would simply be more water bypassing and mixing with warm water
returning to the chiller.
Figure 1. Flow rate out of range systems solution
LOAD
50°F (10°C)
80 gpm (5 l/s)
50°F (10°C)
32 gpm (2 l/s)
60°F (15.6°C)
80 gpm (5 l/s)
50°F (10°C)
114 gpm (7 l/s)
57°F (14°C)
114 gpm (7 l/s)
PUMP
PUMP