Selection Procedure - Carrier 50HS 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 outdoor entering-air
temperature of 95 F, indoor air entering at 1125 cfm
and 67 F ewb (entering wet bulb). The 50HS030 unit
will provide a total cooling capacity of 29,300 Btuh
and a sensible heat capacity of 22,100 Btuh.
For indoor-air temperature other than 80 F edb (en-
tering dry bulb), calculate sensible heat capacity cor-
rection, 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 50HS030 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
14,900 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, 13,650 Btuh (28,550 – 14,900) additional elec-
tric heat is required.
10
Determine additional electric heat capacity in kW.
13,650 Btuh
3414 Btuh/kW
Enter the Electric Heater Packages table on page 19
for 208/240 v, single-phase, 50HS030 unit. The 5-kW
heater at 240 v most closely satisfies the heating re-
quired. To calculate kW at 230 v, multiply the heater
kW by multiplication factor 0.92 found in the Multipli-
cation Factors table on page 21.
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 Electric Heater Pack-
ages table on page 19.
Total unit heating capacity is 30,604 Btuh (14,900
+ 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 Ac-
cessory 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 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.
= 4.0 kW of heat required
0.40 in. wg
0.11 in. wg
0.04 in. wg
0.11 in. wg
0.66 in. wg