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SELECTION PROCEDURE (with example)
I DETERMINE COOLING REQUIREMENTS AT DESIGN
CONDITIONS.
Given:
Gross Cooling Capacity
Required (TC). . . . . . . . . . . . . . . . . . . . . . . . . 39,000 Btuh
Sensible Heat Capacity (SHC) . . . . . . . . . . . . 30,500 Btuh
Temperature of Air Entering Condenser. . . . . . . . . . . 95 F
Temperature of Air Entering
Evaporator. . . . . . . . . . . . . . . . . . . . .80 F edb/67 F ewb
Evaporator Air Quantity . . . . . . . . . . . . . . . . . . .1,200 cfm
External Static Pressure:
Condenser . . . . . . . . . . . . . . . . . . . . . . . . . . 0.50 in. wg
Evaporator (includes static pressure
drop of factory-supplied filter
of 0.06 in. wg) . . . . . . . . . . . . . . . . . . . . . . 0.20 in. wg
II SELECT UNIT BASED UPON REQUIRED COOLING
CAPACITY.
Enter cooling capacity table at temperature of air entering
condenser of 95 F. The 502A036 unit at 1200 cfm and
67 F ewb will provide a Total Capacity (TC) of 44,200 Btuh
and a Sensible Heat Capacity (SHC) of 31,300 Btuh.
Since the entering air is 80 F edb, an SHC correction is
not required.
III DETERMINE EVAPORATOR FAN PERFORMANCE.
Enter Evaporator Fan Performance table at 1200 cfm
and 502A036 data. The external static pressure shown
(0.23 in. wg) will exceed the 0.20 in. wg required. The fan
motor will require 0.52 kW.
IV DETERMINE CONDENSER FAN PERFORMANCE AND
MOTOR PULLEY SETTING REQUIREMENTS.
Enter Condenser Fan Performance table at the selected
cfm and required static pressure of 0.50 in. wg. The fan
motor will require 0.73 kW and the motor pulley should be
set at 2 turns open at 1350 cfm of condenser air required.
NOTE:
Unit 502A024 contains a direct-drive condenser
fan assembly.
PERFORMANCE DATA
GROSS COOLING CAPACITIES
See Legend on page 7.
502A024
Temp
Air Ent
Condenser
(F)
Evaporator Air Quantity — Cfm/BF
600/0.02 800/0.03 1000/0.04
Evaporator Air Ewb Temp (F)
72 67 62 72 67 62 72 67 62
85
TC
27.1 25.3 23.0 27.7 26.4 24.6 27.8 26.9 25.8
SHC
13.5 17.0 20.2 14.7 19.4 23.7 15.6 21.5 25.8
kW
1.64 1.62 1.61 1.65 1.63 1.62 1.65 1.64 1.63
95
TC
26.6 24.5 20.8 27.4 25.8 22.9 28.0 26.5 25.2
SHC
13.4 16.7 19.1 14.7 19.4 22.8 16.0 21.7 25.2
kW
1.85 1.84 1.80 1.86 1.85 1.82 1.87 1.85 1.84
105
TC
25.8 22.3 18.4 27.1 24.5 21.2 27.7 25.6 23.6
SHC
13.1 15.8 17.9 14.7 18.9 21.2 16.2 21.5 23.6
kW
2.09 2.05 1.99 2.11 2.08 2.04 2.12 2.10 2.07
115
TC
24.6 19.9 16.5 26.1 22.0 19.8 26.8 23.6 22.3
SHC
12.7 14.8 16.5 14.4 17.9 19.8 16.0 20.7 22.3
kW
2.36 2.29 2.22 2.39 2.33 2.29 2.39 2.35 2.33
502A036
Temp
Air Ent
Condenser
(F)
Evaporator Air Quantity — Cfm/BF
900/0.01 1050/0.01 1200/0.02
Evaporator Air Ewb Temp (F)
72 67 62 72 67 62 72 67 62
85
TC
45.0 41.1 37.3 45.8 42.3 38.6 46.5 43.4 39.8
SHC
22.5 27.7 32.6 23.6 29.9 35.6 24.6 32.0 38.3
kW
3.19 3.07 2.96 3.22 3.11 3.00 3.25 3.14 3.04
95
TC
43.0 38.8 34.3 44.1 40.1 35.8 45.0 44.2 37.4
SHC
21.8 26.8 31.1 23.1 29.1 34.1 24.4 31.3 36.8
kW
3.42 3.28 3.15 3.46 3.33 3.20 3.49 3.37 3.25
105
TC
40.4 35.8 29.6 41.6 37.1 31.3 42.6 38.2 33.2
SHC
20.9 25.6 28.5 22.3 27.9 30.8 23.7 30.2 33.2
kW
3.63 3.48 3.38 3.68 3.53 3.44 3.73 3.58 3.49
115
TC
37.7 30.6 25.8 38.7 31.6 37.8 39.7 32.8 29.7
SHC
19.9 23.3 25.8 21.3 25.5 27.8 22.7 27.8 29.7
kW
3.85 3.71 3.59 3.90 3.76 3.67 3.94 3.80 3.73