The chiller capacity tables presented on pages 26-35 cover the most frequently encountered leaving water temperatures. The tables reflect a 10 F (6 C) temperature drop through the evaporator. For temperature drops other than 10 F (6 C), refer to Tables F-1 -F-31, and apply the appropriate Performance Data Adjustment Factors. For chilled brine selections, refer to Figures F-3 and 4 for Ethylene and Propylene Glycol Adjustment Factors.

To select a Trane air-cooled Series R^® chiller, the following information is required:

1 Design load in tons of refrigeration

2 Design chilled water temperature drop

3 Design leaving chilled water temperature

4 Design ambient temperature

Evaporator flow rates can be determined by using the following formulas:

NOTE: Flow rates must fall within the limits specified in Tables G-1, G-2 and G-3 (for GPM or for l/s).

Selection Example

Given: Required System Load = 140 Tons Leaving Chilled Water Temperature (LCWT) = 44 F Chilled Water Temperature Drop = 10 F Design Ambient Temperature = 95 F Evaporator Fouling Factor = 0.00025

1 To calculate the required chilled water flow rate we use the formula given below:

2 From Table P-8 (RTAA Performance Data), an RTAA 140 at the given conditions will produce 141.1 tons with a compressor power input of 165.9 KW and a unit EER of 9.4.

3 To determine the evaporator pressure drop we use the flow rate (GPM) and the evaporator water pressure drop curves, Figure F-2. Entering the curve at 336 GPM, the pressure drop for a nominal 140 ton evaporator is 21 feet.

4 For selection of chilled brine units or applications where the altitude is significantly greater than sea level or the temperature drop is different than 10 F, the performance adjustment factors from Table F-8 should be applied at this point.

For example: Corrected Capacity = Capacity (unadjusted) x Glycol Capacity Adjustment Factor

Corrected Flow Rate = Flow Rate (unadjusted) x Glycol Flow Rate Adjustment Factor

5 The final unit selection is:

• QTY (1) RTAA 140
• Cooling Capacity = 141.1 tons
• Entering/Leaving Chilled Water Temperatures = 54/44 F
• Chilled Water Flow Rate = 336 GPM
• Evaporator Water Pressure Drop = 21 ft.
• Compressor Power Input = 165.9 KW
• Unit EER = 9.4

Minimum Leaving Chilled Water Temperature Setpoint

The minimum leaving chilled water temperature setpoint for water is 40 F. For those applications requiring lower setpoints, a glycol solution must be used. Contact the local Trane sales engineer for additional information.