Selection Procedure - Carrier 50HX024-060 Product Data

Selection procedure

I Determine cooling and heating requirements at
design conditions.
Given:
Required Cooling Capacity (TC) . . . . . . 28,000 Btuh
Sensible Heat Capacity (SHC) . . . . . . . 20,500 Btuh
Required Heating Capacity . . . . . . . . . . 28,550 Btuh
Outdoor Entering-Air Temperature . . . . . . . . . . . 95 F
Outdoor-Air Winter Design Temperature . . . . . . 20 F
Indoor-Air Winter Design Temperature . . . . . . . 70 F
Indoor Entering-Air Temperature . . . . . . . . 80 F edb,
Indoor-Air Quantity . . . . . . . . . . . . . . . . . . . 1125 cfm
External Static Pressure . . . . . . . . . . . . . . 0.40 in. wg
Electrical Characteristics (V-Ph-Hz) . . . . . . . 230-1-60
edb — entering dry bulb
ewb — entering wet bulb
II Select unit based on required cooling capacity.
Enter Cooling Capacities table at condenser entering
temperature of 95 F, indoor air entering at 1125 cfm
and 67 F ewb (entering wet bulb). The 50HX030 unit
will provide a total cooling capacity of 28,800 Btuh
and a sensible heat capacity of 21,900 Btuh.
For indoor-air temperature other than 80 F edb (en-
tering dry bulb), calculate sensible heat capacity
correction, as required, using the formula found in
Note 3 following the cooling capacities tables.
NOTE: Unit ratings are net capacities.
III Select electric heat.
Enter the unit 50HX030 Heating Capacities table at
1125 cfm. At 70 F return indoor air and 20 F air en-
tering outdoor coil, the integrated heating capacity is
15,300 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 28,550 Btuh. There-
fore, 13,250 Btuh (28,550 — 15,300) additional elec-
tric heat is required.
Determine additional electric heat capacity in kW.
13,250 Btuh
3414 Btuh/kW
Enter the 50HX Electric Heater Packages — 208/240 V,
Single-Phase, Single-Point Wiring Connections table
on page 22 for unit 50HX030. The 5-kW heater
at 240 v most closely satisfies the heating required. To
calculate kW at 230 v, multiply the heater kW by
multiplication factor 0.92 found in the Wattage Multi-
plication Factors table on page 19.
67 F ewb
5 kW x 0.92 = 4.6 kW
4.6 x 3414 = 15,704 Btuh
To calculate kW at 208 v, see Wattage Multiplication
Factors table on page 19.
Total unit heating capacity is 31,004 Btuh (15,300
+ 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, the
Accessory Electric Heat Pressure Drop table, Wet Coil
Pressure Drop table, and the Filter Pressure Drop table,
find:
External static pressure
Filter
Electric heat
Wet coil
Total static pressure
Enter the table for Dry Coil Air Delivery — Hori-
zontal and Vertical Discharge at 1125 cfm and 230-v
high speed. By interpolation, the standard motor will
deliver 0.66 in. wg static pressure. This will adequately
handle job requirements.
= 3.9 kW of heat required
0.40 in. wg
0.08 in. wg
0.04 in. wg
0.06 in. wg
0.58 in. wg
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