Selection Procedure - Carrier 50JZ Product Data

Selection Procedure

I Determine cooling and heating requirements at design
conditions:
Given:
Required Cooling Capacity (TC) . . . . . . . . . 33,500 Btuh
Sensible Heat Capacity (SHC) . . . . . . . . . . . 24,500 Btuh
Required Heating Capacity . . . . . . . . . . . . . . 25,000 Btuh
Condenser Entering Air Temperature . . . . . . . . . . . . 95°F
Indoor-Air Temperature . . . . . . . . . . 80°F edb, 67°F ewb
Evaporator Air Quantity . . . . . . . . . . . . . . . . . . .1200 cfm
External Static Pressure. . . . . . . . . . . . . . . . . . . 0.2 in. wg
Electrical Characteristics. . . . . . . . . . . . . . . . . . . 208-1-60
II Select unit based on required cooling capacity.
Enter Net Cooling Capacities table at condenser entering
temperature of 95°F. The 50JZ036 unit at 1200 cfm and
67°F ewb (entering wet bulb) will provide a total capacity
of 36,600 Btuh and a SHC of 28,200 Btuh. Calculate SHC
correction, if required, using Note 4 under Cooling
Capacities tables.
III Select electric heat.
Enter the 50JZ036 unit Heating Extended Performance
table at 1200 cfm. At 70°F return indoor air and 20°F air
entering outdoor coil, the integrated heating capacity is
17,400 Btuh. (Select integrated heating capacity value
since deductions for outdoor-coil frost and defrosting have
already been made. No correction is required.)
The required heating capacity is 25,000 Btuh. Therefore,
7,600 Btuh (25,000 – 17,400) additional electric heat is
required
Determine additional electric heat capacity in kw.
7,600 Btuh
= 2.2 kw of heat required
3414 Btuh/kW
10
Enter the Electric Heater table on page 5 for 208/230 v,
single-phase, unit. The 5-kw heater at 240v most closely
satisfies the heating required. To calculate kw at 230v,
multiply the heater kw by multiplication factor 0.92 found
in the Multiplication Factors table on page 17.
5 kw x 0.92 = 4.6 kw
4.6 kw x 3414 Btuh/kw = 15,704 Btuh
Total unit heating capacity is 33,104 Btuh (17,400 +
15,704).
IV Determine fan speed and power requirements at design
conditions.
Before entering the air delivery tables, calculate the total
static pressure required. From the given, Filter Pressure
Drop Table, Electrical Heat Pressure Drop table, and the
Wet Coil Pressure Drop table, find:
External static pressure
Filter
Electric Heaters
Total static pressure
Enter the table for Wet Coil Air Delivery — Horizontal
Discharge, 230 and 460v. At 0.33 in. wg external static
pressure and medium speed, the motor delivers 1171 cfm,
and 467 watts. Adjusting for 208v, the motor delivers 1054
cfm (deduct 10%) and 420 watts.
V Select unit that corresponds to power source available.
The Electrical Data table shows that the unit is designed to
operate at 208-1-60.
0.200 in. wg
0.130 in. wg
0.000 in. wg
0.330 in. wg