Bryant 581A/B manual Selection Procedure With 580F240 Example

SELECTION PROCEDURE (With 580F240 Example)

I DETERMINE COOLING AND HEATING REQUIRE- MENTS AT DESIGN CONDITIONS.

Given:

Required Cooling Capacity . . . . . . . . . . . . . 230,000 Btuh Sensible Heat Capacity (SHC). . . . . . . . . . . 170,000 Btuh Required Heating Capacity . . . . . . . . . . . . . 215,000 Btuh Condenser Entering Air Temp . . . . . . . . . . 95 F (Summer) Evaporator Entering Air Temp . . . . . . . . . . . . . . .80 F edb,

67 F ewb Evaporator Air Quantity . . . . . . . . . . . . . . . . . . . 8,000 cfm External Static Pressure . . . . . . . . . . . . . . . . . . 0.6 in. wg Electrical Characteristics (V-Ph-Hz). . . . . . . . . . . 460-3-60

Vertical discharge unit with optional EconoMi$er IV required.

edb — Entering dry-bulb ewb — Entering wet-bulb

IISELECT UNIT BASED ON REQUIRED COOLING CAPACITY.

Enter Cooling Capacities table for 580F240 (page 183) at condenser entering temperature 95 F, evaporator air entering at 8,000 cfm and 67 F wb. The unit will provide a total cooling capacity of 249,000 Btuh and a sensible heat- ing capacity (SHC) of 188,000 Btuh. For air entering evap- orator at temperatures other than 80 F edb, calculate SHC correction as required.

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.

IIISELECT HEATING CAPACITY OF UNIT TO PROVIDE DESIGN CONDITION REQUIREMENTS.

In the ARI Heating Capacities and Efficiencies table note that the 580F240360 will provide an output capacity of 292,000 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 191 find:

External static pressure	0.60 in. wg
EconoMi$er IV static pressure	0.10 in. wg
Total static pressure	0.70 in. wg

Enter the Fan Performance table 580F240360 at 8,000 cfm and 0.70 in. wg external static pressure. By interpolation, find that the rpm is 1243 and the watts are 5368.

VDETERMINE 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 = 5368

Determine net cooling capacity using the following formula:

Net capacity = Gross capacity – IFM heat = 249,000 Btuh – 5368 Watts

(3.412 WattsBtuh )

=249,000 Btuh – 18,316 Btuh

=230,684 Btuh

Net sensible capacity = 188,000	Btuh – 18,316 Btuh
= 169,684	Btuh

The calculations show that a 580F240360 unit with the standard motor and standard low-medium static drive is the correct selection for the given conditions.

580F180-300

181