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36
SELECTION PROCEDURE (with 580F060 example)
I DETERMINE COOLING AND HEATING REQUIRE-
MENTS AT DESIGN CONDITIONS.
Given:
Required Cooling Capacity (TC). . . . . . . . . . . 55,000 Btuh
Sensible Heat Capacity (SHC) . . . . . . . . . . . . 40,000 Btuh
Required Heating Capacity. . . . . . . . . . . . . . . 60,000 Btuh
Condenser Entering Air Temp. . . . . . . . . . .95 F (Summer)
Evaporator Entering Air Temp. . . . . . . . . . . . . . . 80 F edb,
67 F ewb
Evaporator Air Quantity . . . . . . . . . . . . . . . . . . .2,000 cfm
External Static Pressure . . . . . . . . . . . . . . . . . . . 0.6 in. wg
Electrical Characteristics (V-Ph-Hz) . . . . . . . . . . 230-3-60
Vertical discharge unit with optional EconoMi$er IV
required.
edb — Entering dry-bulb
ewb — Entering wet-bulb
II SELECT UNIT BASED ON REQUIRED COOLING
CAPACITY.
Enter Cooling Capacities table for 580F060 (page 33) at
condenser entering temperature 95 F, evaporator air
entering at 2,000 cfm and 67 F wb. The 580F060 unit will
provide a total cooling capacity of 60,900 Btuh and a sen-
sible heating capacity of 45,300 Btuh. For air entering
evaporator at temperatures other than 80 F edb, calculate
sensible heat capacity correction as required using the for-
mula in the notes following the Cooling Capacities tables.
NOTE: Unit ratings are gross capacities and do not
include the effect of evaporator-fan motor heat. To calcu-
late net capacities, see Step V.
III SELECT HEATING CAPACITY OF UNIT TO PROVIDE
DESIGN CONDITION REQUIREMENTS.
In the Heating Capacities and Efficiencies table (page 9)
note that the 580F060 074 will provide an output capacity
of 59,200 Btuh, which is adequate for the given
application.
IV DETERMINE FAN SPEED AND POWER REQUIRE-
MENTS AT DESIGN CONDITIONS.
Before entering the Fan Performance tables, calculate the
total static pressure required based on unit components.
From the given and the Accessory/FIOP Static Pressure
table on page 75 find:
External static pressure 0.60 in. wg
EconoMi$er IV static pressure 0.12 in. wg
Total Static 0.72 in. wg
Enter the standard motor Fan Performance table 580F060
Vertical Discharge (page 39) at 2,000 cfm and 0.72 in. wg
external static pressure. The standard motor cannot
provide 0.87 in. wg external static pressure. Enter the
alternate motor Fan Performance table for 580F060, verti-
cal discharge. At 2,000 cfm and 0.72 in. wg external static
pressure, find that the rpm is 1219, the Bhp is 1.31, and
the watts are 1168 (interpolation required).
V DETERMINE NET COOLING CAPACITY.
Cooling capacities are gross capacities and do not include
indoor (evaporator) fan motor (IFM) heat. Use the watts
input power to the motor calculated in Section IV above.
IFM Watts = 1168
Determine net cooling capacity using the following
formula:
The calculations show that a 580F060 unit with the alter-
nate motor and drive is the correct selection for the given
conditions.
Net capacity = Gross capacity – IFM heat
)
= 60,900 Btuh – 1168 Watts
(3.412
Btuh
Watts
= 60,900 Btuh – 3985 Btuh
= 56,915 Btuh
Net sensible capacity = 45,300 Btuh – 3985 Btuh
= 41,315 Btuh
580F036-151