13
DESIGN REQUIREMENTS
The following design requirements must be known to select a package chiller.
1. Required cooling capacity in tons
2. Leaving chilled water temperature in
0
F (LCWT)
3. Chilled water flow rate in GPM
4. Chilled water cooling range in
0
F (water in temp. _ water out temp.)
5. Design ambient temperature
6. Minimum ambient temperature
7. Altitude
8. Electrical power supply
SAMPLE SELECTION
Select an Air Cooled Packaged chiller for the following conditions:
Required system capacity is 110 tons at 54
0
F entering chilled water
and 44
0
F leaving water. Design ambient temperature is 95
0
F.
Altitude is 2000 feet above sea level.
Water cooler fouling factor is 0.00010. Power supply: 380/415V-3Ph-50Hz.
STEP-1:
UNIT SELECTION
Entering the capacity performance data at given LCWT and ambient temperature.
ASQ115B chiller unit at sea level will produce 115.3 tons and 120.3 kW compressor
power input at 44
0
F leaving chilled water temperature with 10
0
F water temperature
difference and 95
0
F ambient temperature.
For the conditions required, the unit actual cooling capacity when corrected for
altitude (0.99) and fouling factor (1.0).
Capacity = 115.3x0.99x1.0 = 114.1 Tons, which then exceeds the requirements.
So the selection is correct.
STEP-2:
CHILLED WATER FLOW (GPM):
Water GPM =
Required capacity (Tons) x 24
=
110 x 24
= 264 GPM
Cooling Range,
∆
T 10
0
F
SELECTION PROCEDURE
(English units)
ELEVATION ABOVE
SEA LEVEL (FT.)
CAPACITY
CORRECTION
FACTOR
0
2000
4000
6000
8000
10000
1.00
0.99
0.98
0.97
0.96
0.95
TABLE - 2
EVAPORATOR FOULING
FACTOR (HR-FT
2
-
0
F/BTU)
0.00010
0.00025
0.00050
0.00075
0.00100
CAPACITY
CORRECTION
FACTOR
1.000
0.992
0.978
0.965
0.951
POWER
INPUT
FACTOR
1.000
0.997
0.990
0.984
0.978
ARI
STANDARDS
ARI-550/590-98
ARI-590-86
ARI-590-81
Referring to pressure drop chart (page # 22), pressure drop at 264 GPM = 13.3 ft. of water for selected model.
NOTE:
The total flow rate should be divided by 2 for models ASQ220B - ASQ440B to find out the total pressure drop.
STEP-3:
ELECTRICAL
Refer to electrical data at 380/415V-3Ph-50Hz, the main power wire size for ASQ115B is to be sized for a minimum circuit
ampacity (MCA) of 292 Amps and maximum over current protection (MOCP) of 411 Amps.
STEP-4:
CHILLED WATER PUMP SELECTION
For chilled water pump selection, add all pressure drop in the closed chilled water loop piping to the pressure drop
calculated in step 2.
STEP-5:
LCWT CORRECTION
Refer to table-3: Add correction factor to design leaving chilled water temperature (LCWT) when chilled water tempera-
ture range is above 10
0
F and subtract correction from design leaving chilled water temperature (LCWT) when water
temperature range is below 10
0
F.
EXAMPLE:
If LCWT rise is 12.5
0
F, enter correction curve at 12.5
0
F and read the correction factor of 0.2. The corrected LCWT is
44+0.2 = 44.2
0
F.
NOTE: 1.When the chilled water temperature rise is less than 5
0
F, the high water flow rate will result to excessive
pressure drop. In such cases, contact factory for special selection of a cooler with wider baffle spacing.
2.Please refer to water pressure drop curves.
TABLE - 1
TABLE - 3
CHILLED WATER TEMPERATURE RISE (
0
F)
CORRECTION F
A
C
T
OR (
0
F)
0
-0.2
-0.4
5
10
+0.4
+0.2
+0.6
15
20
