9
SELECTION PROCEDURE (WITH EXAMPLE)
1. Determine cooling and heating requirements at
design conditions:
Given:
Required Cooling Capacity (TC) 10.4kW (35,000 Btuh)..
Sensible Heat Capacity (SHC) 7.3 kW (25,000 Btuh)....
Required Heating Capacity 6.4 kW (22,000 Btuh).......
Condenser Entering Air Temperature 35°C(95°F).......
Indoor-- Air Temperature 26.7°C(80°F) edb...........
19°C(67°F) ewb.................................
Evaporator Air Quantity 543 L/s (1150 CFM)...........
External Static Pressure 24.9 Pa (0.1 IN. W.C.)..........
Electrical Characteristics 400--3--50...................
2. Select unit b ased on required cooling capacity.
A. SI
Enter Net Cooling Capacities SI table at condenser entering
temperature of 35°C, which matches design Condenser Entering
Air Temperature. At 566 L/s and 19°C ewb (entering wet bulb)
will provide a total capacity of 12.5 kW and a SHC of 9.1 kW.
Calculate SHC correction, if required using Note 3 of Net Cooling
Capacities Table.
3. Select electric heat.
The required heating capacity is 6.4 kW (22,000 Btuh)--(given).
Determine additional electric heat capacity in kW.
.22,000 Btuh
= 6.44kW of heat required
3,414 Btuh/kW
Enter the Electric Heater table for the unit. The 6.5 kW heater at
400v most closely satisfies the heating required.
4. Determine fan speed and power requirements at
design conditions.
Before entering the air delivery tables, calculate the total static
pressure required. From the given Filter Pressure Drop Table find:
External Static Pressure 12.5 Pa (0.05 IN. W.C.)
Filter +20/0 Pa (0.12 IN. W.C.)
Total Static Pressure 42.4 Pa (0.17 IN. W.C.)
Enter the table for Wet Coil Air Delivery—Horizontal Discharge,
400 V. At 0.424 Pa (0.17 IN. W.C.) external static pressure and
low speed, the fan will deliver 561 L/s (1188 CFM).
50GL--A
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