Mitsubishi Electric CITY MULTI PUMY-P112VKM6 Service Manual page 15

5-1-2. Heating
Outdoor wet bulb temperature
Total heating load
Room 1 Indoor dry bulb temperature
Heating load
Room 2 Indoor dry bulb temperature
Heating 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
■ Heating calculation
• Tentative selection of indoor units
Room1: PEFY-P50
Room2: PEFY-P71
In this case, the total capacity is 15.3. (6.3 + 9.0 = 15.3)
• Tentative selection of outdoor unit
Proper outdoor unit in this case is P125 as the total capacity of the indoor units is 15.3.
PUMY-P125
• Calculation for the corrected capacity of the total indoor units (CTi)
Correction factor for indoor temperature: Room 1 (23°C)
CTi = Σ (Rated capacity of indoor unit × Correction factor for indoor temperature)
= 6.3 × 0.88 + 9.0 × 0.88
= 13.5 kW
• Calculation for the corrected capacity of the outdoor unit (CTo)
Correction factor for outdoor temperature (2°C WB)
Correction factor for piping length (60 m)
Correction factor for defrosting
CTo = Rated capacity of outdoor unit × Correction factor for outdoor temperature × Correction factor for piping length ×
Correction factor for defrosting
= 16.0 × 1.00 × 0.96 × 0.89
= 13.7 kW
Table 1 Table of correction factor for frosting and defrosting
Outdoor inlet air temp. (°C)
Correction factor
• Determination of maximum system capacity (CTx)
Comparison between CTi and CTo:
CTi = 13.5 < CTo = 13.7, thus, select CTi.
CTx = CTi = 13.5 kW
• Comparison with essential load
Against the essential load 13.2 kW, the maximum system capacity is 13.5 kW: Proper indoor units have been select-
ed.
• Calculation for the maximum indoor unit capacity of each room
When CTx = CTi, use the calculation formula below.
Room1: Rated capacity of Indoor unit × Correction factor for indoor temperature
= 6.3 × 0.88
= 5.5 kW
The capacity is enough for the heating load of Room 1 (5.4 kW): A proper indoor unit is selected.
Room2: Rated capacity of indoor unit × Corrected capacity for the indoor design temperature
= 9.0 × 0.88
= 7.9 kW
The capacity is enough for the heating load of Room 2 (7.8 kW): A proper indoor unit is selected.
Note:
• If CTx = CTo, refer to the calculation formula in "Cooling" to calculate the maximum indoor unit capacity of each
room.
• The selection of units is completed when proper units are selected.
OCH790 _15
Design condition
2°C
13.2 kW
23°C
5.4 kW
23°C
7.8 kW
60 m
10 15 — 20
1.4 1.9 — 2.5
— 15 18 20
— 1.7 2.1 2.3
6.3kW.(Rated)
9.0kW.(Rated)
16.0 kW
Room 2 (23°C)
6 4 2 0 -2
1.00 0.98 0.89 0.88 0.89
— 25 32 — 40 —
— 3.2 4.0 — 5.0 —
22 25 — 35 — 42
2.5 2.9 — 4.0 — 4.8
0.88 (Refer to Figure 3.)
0.88 (Refer to Figure 3.)
1.00 (Refer to Figure 4.)
0.96 (Refer to "Correcting Capacity".)
0.89 (Refer to Table 1.)
-4 -6 -8 -10 -15
0.90 0.95 0.95 0.95 0.95
50 — 63 71 80 100
6.3 — 8.0 9.0 10.0 12.5 16.0 18.0
50 60 — 71 80 100
5.7 6.9 — 8.1 9.3 11.2
-20
0.95
125 140
— —
— —