Bryant 548F, 549B manual SELECTION PROCEDURE WITH 542J180 EXAMPLE, 542J150,180, Capacity

SELECTION PROCEDURE (WITH 542J180 EXAMPLE)

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

Given:

Required Cooling Capacity (TC). . . . . . . . . . 164,000 Btuh

Sensible Heat Capacity (SHC) . . . . . . . . . . . 120,000 Btuh

Required Heating Capacity. . . . . . . . . . . . . . 170,000 Btuh

Outdoor-Air Temperature (Cooling) . . . . . . . . . . . . . . 95 F

Indoor Entering-Air Temperature

(Cooling) . . . . . . . . . . . . . . . . . . . . . 80 F Edb/67 F Ewb

Outdoor Coil Entering-Air Temperature

(Heating) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0° F Indoor Winter Design Temperature . . . . . . . . . . . . . . . 70 F Indoor-Air Quantity . . . . . . . . . . . . . . . . . . . . . . . 6000 Cfm External Static Pressure (ESP . . . . . . . . . . . . . 1.30 in. wg Electrical Characteristics (V-Ph-Hz) . . . . . . . . . . 230-3-60

EconoMi$er is specified.

Edb — Entering dry bulb

Ewb — Entering wet bulb

II SELECT UNIT BASED ON REQUIRED COOLING

CAPACITY.

Enter Cooling Capacity table on page 109 at outdoor-

entering temperature of 95 F, indoor air entering at

6000 cfm and 67 F ewb. The 542J180 will provide a total

capacity (TC) of 180,800 Btuh, a sensible heat capacity

Enter the Electric Heating Capacities table at 230-3-60. The 34-kW heater satisfies the electric heater requirements.

IV DETERMINE FAN SPEED AND MOTOR HORSEPOWER REQUIREMENTS AT DESIGN CONDITIONS.

Before entering Fan Performance table, calculate the total static pressure required based on unit components. From the given and the Accessory/FIOP Static Pressure table on page 112, find:

External static pressure	1.30 in. wg
EconoMi$er static pressure	0.07 in. wg
Electric heat static pressure	0.09 in. wg
Total static pressure	1.46 in. wg

Enter the Fan Performance table on page 111. At 6000 cfm and 1.46 in. wg external static pressure, the fan speed is 1214 and the bhp is 3.95 (interpolation required). The standard motor and alternate high static drive are suitable.

VDETERMINE NET CAPACITIES.

Capacities are gross and do not include the effect of indoor-fan motor (IFM) heat.

Determine net cooling capacity as follows: Net capacity = Gross capacity – IFM heat

2545 Btuh

(SHC) of 136,400 Btuh and a total unit kW of 15.88.

= 180,800 – 3.95 bhp x

hp

For indoor-air temperature other than 80 F edb, calculate

sensible heat capacity correction, as required, using the

formula found in Note 3 following the Cooling Capacities

table on page 109.

NOTE: Unit ratings are gross capacities and do not

include the effect of indoor-fan motor heat. To calculate net

capacities, see Step V.

III SELECT ELECTRIC HEAT.

Enter the Integrated Heating Capacities table on page 110

at 6000 cfm. At 70 F return indoor air and 0° F air entering

the outdoor coil, the integrated heating capacity is

58,500 Btuh with a unit input kW of 11.71 (interpolation

required).

The required heating capacity is 170,000 Btuh; therefore,

111,500 Btuh (170,000 – 58,500) additional electric heat is

necessary.

Determine the additional electric heat capacity in kW.

.85

=180,800 – 11,827

=168,973 Btuh

Net sensible capacity = 136,400 – 11,827

=124,573 Btuh

Determine net heating capacity as follows: Net capacity =

Gross capacity + IFM heat + Electric heat capacity

=58,500 + (IFM kW x 3412) + (Elec. kW x 3412)

=58,500 + 11,827 + (34 x 3412)

=58,500 + 11,827 + 116,008

=186,335 Btuh

111,500 Btuh

= 32.6 kW

3412 Btuh/kW

542J150,180

108