10
50JX Corner weights ( In Pounds)
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
67°F ewb
Indoor-Air Quantity . . . . . . . . . . . . . . . . . . . . . . 1125 cfm
External Static Pressure . . . . . . . . . . . . . . . . . . 0.20 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 Extended Performance table at outdoor
entering-air temperature of 95°F, indoor air entering at
1125 cfm and 67°F ewb (entering wet bulb). The unit will
provide a total cooling capacity of 30,900 Btuh and a
sensible heat capacity of 24,800 Btuh.
For indoor-air temperature other than 80°F edb (entering
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 Heating Extended Performance table at 1125
cfm. At 70°F return indoor air and 20°F air entering
outdoor coil, the integrated heating capacity is 16,200 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. Therefore,
12,350 Btuh (28,550 – 16,200) additional electric heat is
required.
Determine additional electric heat capacity in kW.
12,350 Btuh
3414 Btuh/kW
Enter the Electric Heater table on page 5 for 208/230 v,
single-phase, unit. 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 Multiplication Factors table on page 17.
5 kW x 0.92 = 4.6 kW
4.6 kW x 3414 = 15,704 Btuh
Total unit heating capacity is 31,900 Btuh (16,200 +
15,704).
IV Determine fan speed and power requirements at design
conditions.
Before entering the air delivery tables, calculate the total
static pressure required.
= 3.6 kW of heat required
Selection Procedure (with example)
12
43
x
y
CORNER WEIGHTS (Small Cabinet) CORNER WEIGHTS (Large Cabinet)
Unit 24 30 36 —— Unit 42 48 60
Total Weight (lbs.) 299 320 328 —— Total Weight (lbs.) 350 375 428
Corner Weight 1 63 63 64 —— Corner Weight 1 75 81 92
Corner Weight 2 62 74 76 —— Corner Weight 2 49 52 60
Corner Weight 3 56 56 58 —— Corner Weight 3 95 102 116
Corner Weight 4 118 127 130 —— Corner Weight 4 131 140 160
Model 50JX
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