SELECTION PROCEDURE (With 581B048 Example)
I DETERMINE COOLING AND HEATING REQUIRE- MENTS AT DESIGN CONDITIONS.
Given:
Required Cooling Capacity (TC) . . . . . . . . . . 44,600 Btuh Sensible Heat Capacity (SHC). . . . . . . . . . . . 32,000 Btuh Required Heating Capacity . . . . . . . . . . . . . . 85,000 Btuh Condenser
67 F ewb Evaporator Air Quantity . . . . . . . . . . . . . . . . . . . .1600 cfm External Static Pressure (ESP) . . . . . . . . . . . . 0.75 in. wg Electrical Characteristics
IISELECT UNIT BASED ON REQUIRED COOLING CAPACITY.
Enter the Cooling Capacities table (page 18) at condenser entering temperature of 95 F,
For this example:
Correction factor = 1.10 x (1
Multiply the correction factor of 1.738 by 1600 cfm (a total of 2781). From the Gross Cooling Capacities tables find that the sensible heat capacity at 80 F is 34.7 MBtuh (equivalent to 34,700 Btuh). Add 34,700 and 2781 to get the corrected sensible heat capacity of 37,481.
NOTE: Unit ratings are gross capacities and do not include the effect of
IIISELECT HEATING CAPACITY OF UNIT TO PROVIDE DESIGN CONDITION REQUIREMENTS.
IV DETERMINE FAN SPEED AND POWER REQUIRE- MENTS AT DESIGN CONDITIONS.
Before entering the Fan Performance tables, calculate the total static pressure required based on unit components. From the given and the Pressure Drop tables (page 40), find:
External static pressure | .75 in. wg |
Durablade economizer | .05 in. wg |
Total static pressure | = .80 in. wg |
Enter the Fan Performance table for
Using
1.17 (746)
Watts =
.75
Watts = 1164
V DETERMINE NET COOLING CAPACITY.
Cooling capacities are gross and do not include
Net capacity | = | gross capacity | – IFM heat |
| |
| = | 48,900 Btuh | – 1164 Watts |
| |
|
|
| (3.413 | Btuh | ) |
|
|
| Watts | ||
| = | 48,900 Btuh | – 3972 | Btuh |
|
Net capacity | = | 44,928 Btuh |
|
|
|
Net sensible capacity = 37,481 Btuh – 3972 Btuh
= 33,509 Btuh
In the Heating Capacities and Efficiencies table (page 5) note that unit
17