12
SELECTION PROCEDURE (WITH EXAMPLE)
1. Determine cooling and heating requirements at
design conditions:
Given:
Required Cooling Capacity (TC) 34,000 Btuh..........
Sensible Heat Capacity (SHC) 25,000 Btuh............
Required Heating Capacity 60,000 Btuh...............
Condenser Entering Air Temperature 95°F(35°C).......
Indoor--Air Temperature 80°F(26°C)edb 67°F(19°C)ewb.
Evaporator Air Quantity 1200 CFM..................
External Static Pressure 0.10 in. W.C..................
Electrical Characteristics 208--1--60...................
2. S elect unit based on required cooling capacity.
Enter Net Cooling Capacities table at condenser entering
temperature of 95°F(35°C). Unit 036 at 1200 cfm and 67°F
(19°C) ewb (entering wet bulb) will provide a total capacity of
34,200 Btuh and a SHC of 27,400 Btuh. Calculate SHC correction,
if required, using Note 4 under Cooling Capacities tables.
3. S elect heating capacity of u nit to provide design
condition requirement.
In the Heating Capacities and Efficiencies table, note that the unit
036090 will provide 72,000 Btuh with an input of 90,000 Btuh.
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 example, the Wet Coil Pressure
Drop Table, and the Filter Pressure Drop Table:
External Static Pressure 0.10 in. wc
Filter 0.07 in. wc
Wet Coil Pressure Drop 0.18 in.
wc
Total Static Pressure 0.28 in. wc
Enter the table for Dry Coil Air Delivery—Horizontal and
Downflow Discharge. At .287 in. wc ESP, the closest speed to
1200 CFM is Med--Low (pink wire), which delivers 1262 CFM at
.3 in ESP.
5. Select unit that corresponds to power source
available.
The Electrical Data Table shows that the unit is designed to operate
at 208--1--60.
577C-- --A
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