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SELECTION PROCEDURE (WITH EXAMPLE)
I
DETERMINE COOLING AND HEATING REQUIREMENTS
AT DESIGN CONDITIONS:
Given:
. . . Required Cooling Capacity (TC).....................35,000 Btuh
. . . Sensible Heat Capacity (SHC).........................25,000 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....................................... 0.1 in. wg
. . . Electrical Characteristics.......................................208-1-60
II
. SELECT UNIT BASED ON REQUIRED COOLING
CAPACITY.
Enter Net Cooling Capacities table at condenser entering
temperature of 95 F. Unit 48GX036 at 1200 cfm and 67 F
ewb (entering wet bulb) will provide a total capacity of
35,000 Btuh and a SHC of 25,200 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 48GX036090 will provide 71,910 Btuh
with an input of 88,000 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:
External Static Pressure
0.1 in. wg
Wet Coil
0.1 in. wg
Filter
0.2 in. wg
Total Static Pressure
0.4 in. wg
Enter the table for Dry Coil Air Delivery — Horizontal and
Downflow Discharge on page 15. For 208 v operation,
deduct 10% from value given. At 0.4 ESP (external static
pressure), the fan will deliver 1213 cfm at medium speed.
The fan speed should be set at medium speed.
V SELECT UNIT THAT CORRESPONDS TO POWER
SOURCE AVAILABLE.
The Electrical Data table on page 21 shows that the unit is
designed to operate at 208-1-60.
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