Bryant 581A/B manual Selection Procedure, Determine NET Cooling Capacities

SELECTION PROCEDURE

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

Given:

Required Gross Cooling

Capacity (TC) . . . . . . . . . . . . . . . . . . . . . 168,000 Btuh Gross Sensible Heat

Capacity (SHC) . . . . . . . . . . . . . . . . . . . . 121,000 Btuh Required Heating Capacity . . . . . . . . . . . . . 190,000 Btuh Condenser Entering Air

Temperature . . . . . . . . . . . . . . . . . . . . . . . 95 F Summer Indoor Air Temperature . . . . . . . . . . . .80 F edb, 67 F ewb Evaporator Air Quantity . . . . . . . . . . . . . . . . . . . 6,000 cfm External Static Pressure . . . . . . . . . . . . . . . . . 1.40 in. wg Electrical Characteristics (V-Ph-Hz). . . . . . . . . . . 230-3-60

IISELECT UNIT BASED ON REQUIRED COOLING CAPACITY.

Enter Cooling Capacities table for 581A180 at condenser entering temperature of 95 F, evaporator air quantity of 6,000 cfm, and indoor air temperature of 67 F. The 581A180 unit will provide a total cooling capacity of 190,000 Btuh and a SHC of 136,000 Btuh. For evaporator air temperatures other than 80 F, calculate SHC correction using formula in notes under cooling capacity tables.

Unit meets design conditions for TC and SHC.

NOTE: Unit ratings are gross capacities and do not include the effect of indoor fan motor heat. To calculate net capacities, see Step V.

IIISELECT HEATING CAPACITY OF UNIT TO PROVIDE DESIGN CONDITION REQUIREMENT.

In Heating Capacities and Efficiencies table, note that 581A180275 unit will provide 223,000 Btuh with an input of 275,000 Btuh.

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. Tabulated fan performance includes filters and wet evapo- rator coil. Refer to Accessory/FIOP Static Pressure table for added pressure drops.

Calculate pressure drop:
Design External Static Pressure	1.40
EconoMi$er IV	0.07
	1.47 in. wg (ESP)

Enter Fan Performance tables for 581A180 (low heat units) at 6,000 cfm and 1.47 in. wg. The rpm is 1228 and the Bhp is 4.73. The factory-installed 5 hp motor and alter- nate high-static drive are sufficient for this operation.

VDETERMINE NET COOLING CAPACITIES.

Cooling capacities are gross capacities and do not include indoor (evaporator) fan motor (IFM) heat. To determine input power to the motor, enter the Fan Performance tables for 581A180 (low heat units) at 6,000 cfm and 1.47 in. wg. Input watts to the motor are 4035.

Determine net cooling capacity and net sensible cooling capacity using the following formulas:

IFM Heat = Input Watts x 3.412 Btuh/Watt

=4035 x 3.412

=13,767 Btuh

Net Capacity = Gross Capacity – IFM Heat

=190,000 – 13,767

=176,233 Btuh

Net Sensible Cap. = Gross Sensible Cap. – IFM Heat

=136,000 – 13,767

=122,233 Btuh

The calculations show that a 581A180275 unit is the cor- rect selection for the given conditions.

VI SELECT THE UNIT THAT CORRESPONDS TO POWER SOURCE AVAILABLE.

The electrical data table shows that the 230-3-60 unit is available.

581A155-300

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