Catalogue

8 RLC-PRC006M-EN
Application Considerations
temperature or ice making machines.The maximum water temperature that can be circulated
through an evaporator when the unit is not operating is 108°F (42°C).
Flow Rates Out of Range
Many process cooling jobs require flow rates that cannot be met with the minimum and maximum
published values for the Model RTAC evaporator. A simple piping change can alleviate this
problem. For example: A plastic injection molding process requires 80 gpm (5.1 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 120 gpm (7.6 l/s).The system layout in Figure A1 can
satisfy the process.
Flow Control
Trane requires the chilled water flow control in conjunction with the Air-Cooled Series R Chiller to
be done by the chiller.This will allow the chiller to protect itself in potentially harmful conditions.
Supply Water Temperature Drop
The performance data for theTrane air-cooled Series R chiller is based on a chilled water
temperature drop of 10°F (5.6°C). Chilled water temperature drops from 6 to 18°F (3.3 to 10°C) may
be used as long as minimum and maximum water temperatures and flow rates are not violated.
Temperature drops outside this range are beyond the optimum range for control and may
adversely affect the microcomputer's ability to maintain an acceptable supply water temperature
range. Further, temperature drops of less than 6°F (3.3°C) may result in inadequate refrigerant
superheat. Sufficient superheat is always a primary concern in any refrigerant system and is
especially important in a package chiller where the evaporator is closely coupled to the
compressor.When temperature drops are less than 6°F (3.3°C), an evaporator runaround loop may
be required.
Leaving WaterTemperature Out of Range
Many process cooling jobs require temperature ranges that cannot be met with the minimum and
maximum published values for the Model RTAC evaporator. A simple piping change can alleviate
this problem. For example: A laboratory load requires 120 gpm (7.6 l/s) of water entering the
process at 85°F (29.4°C) and returning at 95°F (35°C).The accuracy required is better than the
cooling tower can give.The selected chiller has adequate capacity, but a maximum leaving chilled
water temperature of 60°F (15.6°C).
In Figure A2, both the chiller and process flow rates are equal.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.
Figure 1. Flow rate out of range system layout