OCH790 _14
5 DATA
5-1. Selection of indoor and outdoor units
5-1-1. Cooling
Design condition
Outdoor dry bulb temperature
39ºC
Total cooling load
10.6 kW
Room 1
Indoor dry bulb temperature
27ºC
Indoor wet bulb temperature
20ºC
Cooling load
4.6 kW
Room 2
Indoor dry bulb temperature
24ºC
Indoor wet bulb temperature
18ºC
Cooling load
6.0 kW
Other
Indoor/Outdoor piping equivalent length
60 m
Capacity of indoor unit
P·FY series Model class of indoor unit
10
15
—
20
—
25
32
—
40
—
50
—
63
71
80
100 125 140
Model capacity (kW)
1.2
1.7
—
2.2
—
2.8
3.6
—
4.5
—
5.6
—
7.1
8.0
9.0
11.2 14.0 16.0
M series
S series
P series
Model class of indoor unit
—
15
18
20
22
25
—
35
—
42
50
60
—
71
80
100
—
—
Model capacity (kW)
—
1.5
1.8
2.0
2.2
2.5
—
3.5
—
4.2
5.0
6.0
—
7.1
8.0
10.0
—
—
■
Cooling calculation
• Tentative selection of indoor units
Room1: PEFY-P50
5.6 kW (Rated)
Room2: PEFY-P71
8.0 kW (Rated)
In this case, the total capacity is 13.6. (5.6 + 8.0 = 13.6)
• Tentative selection of outdoor unit
Proper outdoor unit in this case is P125 as the total capacity of the indoor units is 13.6.
PUMY-P125
14.0 kW (Rated)
•
Calculation for the corrected capacity of the total indoor units (CTi)
Correction factor for indoor design wet bulb temperature: Room 1 (20°C) 1.03 (Refer to Figure 1.)
Room 2 (18°C) 0.94 (Refer to Figure 1.)
CTi = Σ (Rated capacity of indoor unit × Correction factor for indoor temperature)
= 5.6 × 1.03 + 8.0 × 0.94
= 13.3 kW
•
Calculation for the corrected capacity of the outdoor unit (CTo)
Correction factor for outdoor temperature (39°C)
0.92 (Refer to Figure 2.)
Correction factor for piping length (60 m)
0.88 (Refer to "Correcting Capacity".)
CTo = Rated capacity of outdoor unit × Correction factor for outdoor temperature × Correction factor for piping length
= 14.0 × 0.92 × 0.88
= 11.3 kW
•
Determination of maximum system capacity (CTx)
Comparison between CTi and CTo:
CTi = 13.3 > CTo = 11.3, thus, select CTo.
CTx = CTo = 11.3 kW
•
Comparison with essential load
Against the essential load 10.6 kW, the maximum system capacity is 11.3 kW: A proper outdoor unit is selected.
•
Calculation for the maximum indoor unit capacity of each room
When CTx = CTo, use the calculation formula below.
Room1: CTx × Corrected capacity for Room1/CTi
= 11.3 × (5.6 × 1.03)/13.3
= 4.9 kW
The capacity is enough for the cooling load of Room 1 (4.6 kW): A proper indoor unit is selected.
Room2: CTx × Corrected capacity for Room2/CTi
= 11.3 × (8.0 × 0.94)/13.3
= 6.4 kW
The capacity is enough for the cooling load of Room 2 (6.0 kW): A proper indoor unit is selected.
Note:
•
If CTx = CTi, refer to the calculation formula in "Heating" to calculate the maximum indoor unit capacity of each
room.
•
Go on to the selection of units for heating after the selection for cooling has successfully completed. If failed, try
again until proper units are selected.
