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—12—
SELECTION PROCEDURE (WITH EXAMPLE)
I DETERMINE COOLING AND HEATING REQUIREMENTS
AT DESIGN CONDITIONS:
Given:
Required Cooling Capacity (TC).......................34,500 Btuh
Sensible Heat Capacity (SHC)......................... 26,000 Btuh
Required Heating Capacity...............................60,000 Btuh
Condenser Entering Air Temperature...........................95°F
Indoor-Air Temperature ........................80°F edb 67°F ewb
Evaporator Air Quantity .....................................1200 CFM
External Static Pressure....................................... 0.2 in. wg
Electrical Characteristics.......................................230-1-60
II SELECT UNIT BASED ON REQUIRED COOLING
CAPACITY.
Enter Net Cooling Capacities table at condenser entering
temperature of 95 F. Unit 036 at 1225 cfm and 67 F ewb
(entering wet bulb) will provide a total capacity of 36,500
Btuh and a SHC of 27,600 Btuh. Calculate SHC correction,
if required, using Note 4 under Cooling Capacities tables.
III SELECT HEATING CAPACITY OF UNIT TO PROVIDE
DESIGN CONDITION REQUIREMENT.
In the Heating Capacities and Efficiencies table on page 4,
note that the unit 036090 will provide 70,000 Btuh with an
input of 90,000 Btuh.
IV DETERMINE FAN SPEED AND POWER REQUIRE-
MENTS AT DESIGN CONDITIONS.
Before entering the air delivery tables, calculate the total
static pressure required. From the given example, the Wet
Coil Pressure Drop Table, and the Filter Pressure Drop table
on page 16, find at 1200 cfm:
Wet Coil Pressure Drop 0.032 in. ws
External Static Pressure 0.2 in. wg
Filter Pressure Drop 0.13 in. wg
Total Static Pressure 0.362 in. wg
Enter the table for Dry Coil Air Delivery — Horizontal and
Downflow Discharge. At 0.362 ESP (external static
pressure), the fan will deliver 1235 cfm with the NOM Speed
pin selected.
V SELECT UNIT THAT CORRESPONDS TO POWER
SOURCE AVAILABLE.
The Electrical Data table shows that the unit is designed to
operate at 208/230-1-60.
12
43
x
y
574B CORNER WEIGHTS
CORNER # 024 030 036 042 048 060
1 70 78 92 100
254 60 7278
3 84 94 111 120
4 141 156 188 201
TOTAL WEIGHT 350 388 463 499