Heating Calculation; Temporary Selection Of Indoor Units; Total Indoor Units Capacity; Selection Of Outdoor Unit - Mitsubishi Electric PUMY-P250YBM Technical & Service Manual

<Heating>
Outdoor Design Wet Bulb Temperature
Total Heating Load
Room1, Room2
Indoor Design Dry Bulb Temperature
Heating Load
Room3, Room4
Indoor Design Dry Bulb Temperature
Heating Load
<Other>
Indoor/Outdoor Equivalent Piping Length
Capacity of indoor unit
P•FY Series Model Number for
indoor unit
Model
Capacity
M Series Model Number for
indoor unit
Model
Capacity

2. Heating Calculation

(1) Temporary Selection of Indoor Units

Room1, Room2
PEFY-P63
Room3, Room4
PEFY-P71

(2) Total Indoor Units Capacity

P63 + P63 + P71 + P71 = P268

(3) Selection of Outdoor Unit

The P300 outdoor unit is selected as total indoor units capacity is P268
PUMY-P300YBM
(4) Total Indoor Units Capacity Correction Calculation
Room1, Room2
Indoor Design Dry Bulb Temperature Correction (24ºC)
Room3, Room4
Indoor Design Dry Bulb Temperature Correction (25ºC)
Total Indoor Units Capacity (CTi)
CTi = Σ (Indoor Unit Rating × Indoor Design Temperature Correction)
= 8.0×0.84 + 8.0×0.84 + 9.0×0.80 + 9.0×0.80
= 27.8 kW
(5) Outdoor Unit Correction Calculation
Outdoor Design Wet Bulb Temperature Correction (2ºC)
Piping Length Correction (30 m)
Defrost Correction
Total Outdoor Unit Capacity (CTo))
CTo = Outdoor Unit Rating × Outdoor Design Temperature Correction × Piping Length
Correction × Defrost Correction
= 37.5 × 1.00 × 0.98 × 0.89
= 32.7 kW
(6) Determination of Maximum System Capacity
Comparison of Capacity between Total Indoor Units Capacity (CTi) and Total Outdoor Unit Capacity (CTo)
CTi = 27.8 < CTo = 32.7, thus, select CTi.
CTx = CTi = 27.8 kW
(7) Comparison with Essential Load
Against the essential load 25.0kW, the maximum system capacity is 27.8 kW: Proper outdoor units have been selected.
(8) Calculation of Maximum Indoor Unit Capacity of Each Room
CTx = CTi, thus, calculate by the calculation below
Room1, 2
Indoor Unit Rating × Indoor Design Temperature Correction
= 8.0 × 0.84
= 6.7 kW
Room3, 4
Indoor Unit Rating × Indoor Design Temperature Correction
= 9.0 × 0.80
= 7.2 kW
Note: If CTx = CTo, please refer to the <Cooling> section to calculate the Maximum Indoor Unit Capacity of Each Room.
Completed selecting units since the selected units fulfill the heating loads of Room 1 to 4.
OCH760
Design Condition
Model Model Model Model Model
10 15 20 25
1.4 1.9 2.5 3.2 4.0
Model Model Model Model Model
15 18 20 22
1.7 2.1 2.3 2.5 2.9
8.0 kW (Rated)
9.0 kW (Rated)
37.5 kW
OK: fulfills the load 6.0 kW
OK: fulfills the load 6.5 kW
2ºC
25.0 kW
24ºC
6.0 kW
25ºC
6.5 kW
30 m
Model Model Model Model
32 40 50 63 71
5.0 6.3 8.0 9.0
Model Model Model
─
25 35 42 50
4.0 4.8 5.7 ─
0.84 (Refer to Figure 4)
0.80 (Refer to Figure 4)
1.00 (Refer to Figure 5)
0.98 (Refer to Figure 6)
0.89 (Refer to Table 1)
Table 1 Table of correction factor at frost and defrost
Outdoor Intake
Temperature (°C W.B.)
Correction factor
12
Model Model Model Model Model
80 100 125 140 200
10.0 12.5 16.0 18.0 25.0
─ ─ ─ ─
─ ─ ─ ─
1.2
1.1
1.0
0.9
0.8
0.7
0.6
15 16 17 18 19 20 21 22
Indoor Temperature [°C D.B.]
Figure 4 Indoor unit temperature correction
To be used to correct indoor unit only
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
-20 -15 -10 -5 0
Outdoor Temperature [°C W.B.]
Figure 5 Outdoor unit temperature correction
To be used to correct outdoor unit only
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0 20 40 60 80 100
Piping equivalent length (m)
Figure 6 Correction of refrigerant piping length
6 4 2 0 -2 -4 -6
1.00 0.98 0.89 0.88 0.89 0.90 0.95 0.95 0.95 0.95 0.95
Unit: kW
Model
250
31.5
─ ─
─ ─
23 24 25 26 27
Indoor temperature
20°C D.B.
5 10 15
120 140 160 180
-8 -10 -15 -20