SELECTION PROCEDURE (with 559F180 example)

559F180-300

I DETERMINE COOLING REQUIREMENTS AT DESIGN CONDITIONS.

Given:

Required Cooling Capacity . . . . . . . . . . . . . . 170,000 Btuh Sensible Heat Capacity . . . . . . . . . . . . . . . . 111,000 Btuh Condenser Entering Air Temp. . . . . . . . . . .95 F (Summer) Evaporator Entering Air Temp. . . . . . . . . . . . . . . 80 F edb, 67 F ewb Evaporator Air Quantity . . . . . . . . . . . . . . . . . . . 4,500 cfm

External Static Pressure . . . . . . . . . . . . . . . . . . . 0.6 in. wg Electrical Characteristics (V-Ph-Hz) . . . . . . . . . . 460-3-60

Vertical discharge unit with optional economizer required.

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

IISELECT UNIT BASED ON REQUIRED COOLING CAPACITY.

Enter Cooling Capacities table for 559F180 (page 119) at condenser entering temperature 95 F, evaporator air enter- ing at 4,500 cfm and 67 F wb. The 559F180 unit will pro- vide a total cooling capacity of 178,000 Btuh and a sensible heating capacity of 117,000 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 IV.

IIIDETERMINE 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 125 find:

External static pressure

0.60 in. wg

Economizer static pressure

0.04 in. wg

Total static pressure

0.64 in. wg

Enter the Fan Performance table 559F180 (page 123) at 4,500 cfm and 0.64 in. wg external static pressure. By interpolation, find that the rpm is 905 and the watts are 1503.

IV 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 III above.

IFM Watts = 1503

Determine net cooling capacity using the following formula:

Net capacity = Gross capacity – IFM heat = 178,000 Btuh – 1503 Watts

Btuh

(3.412 Watts )

=178,000 Btuh – 5128 Btuh

=172,872 Btuh

Net sensible capacity = 117,000 Btuh – 5128 Btuh = 111,872 Btuh

The calculations show that a 559F180 unit with the standard motor and standard low-medium static drive is the correct selection for the given conditions.

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Bryant 551B SELECTION PROCEDURE with 559F180 example, I Determine Cooling Requirements At Design Conditions, 559F180-300

551A, 551B, 558F specifications

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