Mitsubishi Electric CITY MULTI PUMY-P112VKM6 Service Manual page 14

5 DATA
5-1. Selection of indoor and outdoor units
5-1-1. Cooling
Outdoor dry bulb temperature
Total cooling load
Room 1 Indoor dry bulb temperature
Indoor wet bulb temperature
Cooling load
Room 2 Indoor dry bulb temperature
Indoor wet bulb temperature
Cooling load
Other Indoor/Outdoor piping equivalent length
Capacity of indoor unit
P·FY series Model class of indoor unit
Model capacity (kW)
M series Model class of indoor unit
S series
Model capacity (kW)
P series
■ Cooling calculation
• Tentative selection of indoor units
Room1: PEFY-P50
Room2: PEFY-P71
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
• Calculation for the corrected capacity of the total indoor units (CTi)
Correction factor for indoor design wet bulb temperature: Room 1 (20°C)
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)
Correction factor for piping length (60 m)
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.
OCH790 _14
Design condition
39ºC
10.6 kW
27ºC
20ºC
4.6 kW
24ºC
18ºC
6.0 kW
60 m
10 15 — 20
1.2 1.7 — 2.2
— 15 18 20
— 1.5 1.8 2.0
5.6 kW (Rated)
8.0 kW (Rated)
14.0 kW (Rated)
— 25 32 — 40 —
— 2.8 3.6 — 4.5 —
22 25 — 35 — 42
2.2 2.5 — 3.5 — 4.2
1.03 (Refer to Figure 1.)
Room 2 (18°C) 0.94 (Refer to Figure 1.)
0.92 (Refer to Figure 2.)
0.88 (Refer to "Correcting Capacity".)
50 — 63 71 80 100
5.6 — 7.1 8.0 9.0 11.2 14.0 16.0
50 60 — 71 80 100
5.0 6.0 — 7.1 8.0 10.0
125 140
— —
— —