Carrier 48GS Guide User Manual download pdf (Page 11)

Selection procedure (with example)

I 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

. . . Indoor-Air Temperature .......................80°F edb 67°F ewb

. . . Evaporator Air Quantity ....................................1200 CFM

. . . External Static Pressure ......................................0.4 in. wg

. . . Electrical Characteristics ......................................230-1-60

II Select unit based on required cooling capacity.

Enter Net Cooling Capacities table at outdoor entering

temperature of 95°F. Unit 48GS036 at 1200 cfm and 67°F

ewb (entering wet bulb) will provide a total capacity of

34,400 Btuh and a SHC of 25,400 Btuh.

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 48GS036090 will provide 71,910

Btuh with an input of 90,000 Btuh.

IV 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 on page 16, find at 1200 cfm:

External Static Pressure 0.40 in. wg

Wet Coil 0.10 in. wg

Filter/Economizer 0.12 in. wg

Total Static Pressure 0.62 in. wg

Enter the table for Dry Coil Air Delivery — Horizontal and

Downflow Discharge for 230 V and 460 V on page 15. The

fan will deliver 1360 CFM at 0.60 ESP (external static

pressure) at high speed and 1167 cfm at 0.60 ESP at

medium speed. The fan speed should be set at high.

V Select unit that corresponds to power source available.

The Electrical Data table on page 23 shows that the unit is

designed to operate at 230-1-60.

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Carrier 48GS Guide User Manual Page 11