Mitsubishi Electric PUMY-P36NKMU2-BS Technical & Service Manual page 14

<Cooling>
Outdoor Design Dry Bulb Temperature
Total Cooling Load
Room1
Indoor Design Dry Bulb Temperature
Indoor Design Wet Bulb Temperature
Cooling Load
Room2
Indoor Design Dry Bulb Temperature
Indoor Design Wet Bulb Temperature
Cooling Load
<Other>
Indoor/Outdoor Equivalent Piping Length
Capacity of indoor unit
Model Number
Model 05 Model 06 Model 08 Model 12 Model 15 Model 18 Model 24 Model 27 Model 30 Model 36 Model 48 Model 54 Model 72
for indoor unit
Model
5.0 6.0
Capacity
1. Cooling Calculation
(1) Temporary Selection of Indoor Units
Room1
PEFY-P15
Room2
PEFY-P18
(2) Total Indoor Units Capacity
P15+ P18 = P33
(3) Selection of Outdoor Unit
The P36 outdoor unit is selected as total indoor units capacity is P33
PUMY-P36
(4) Total Indoor Units Capacity Correction Calculation
Room1
Indoor Design Wet Bulb Temperature Correction (68.0ºF)
Room2
Indoor Design Wet Bulb Temperature Correction (66.2ºF)
Total Indoor Units Capacity (CTi)
CTi = Σ (Indoor Unit Rating × Indoor Design Temperature Correction)
= 15.0 × 1.02 + 18.0 × 0.95
= 32.4 kBtu/h
(5) Outdoor Unit Correction Calculation
Outdoor Design Dry Bulb Temperature Correction (98.6ºF)
Piping Length Correction (250 ft)
Total Outdoor Unit Capacity (CTo)
CTo = Outdoor Rating × G(CTi)
× Piping Length Correction
= 36.0 × 0.98 × 0.93
= 32.8 kBtu/h
*1 G(CTi) is used only when greater than 100% indoor model size are connected in total,
refer to STANDARD CAPACITY DIAGRAM.
(6) Determination of Maximum System Capacity
Comparison of Capacity between Total Indoor Units Capacity (CTi) and Total Outdoor Unit Capacity (CTo)
CTi = 32.4 < CTo = 32.8, thus, select CTi.
CTx = CTi = 32.4 kBtu/h
(7) Comparison with Essential Load
Against the essential load 30.3 kBtu/h, the maximum system capacity is 32.4 kBtu/h: 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
Indoor Unit Rating × Indoor Design Temperature Correction
= 15.0 × 1.02
= 15.3 kBtu/h
Room2
Indoor Unit Rating × Indoor Design Temperature Correction
= 18.0 × 0.95
= 17.1 kBtu/h
Go on to the heating trial calculation since the selected units fulfill the cooling loads of Room 1, 2.
OCH695B
Design Condition
8.0 12.0 15.0 18.0
15.0 kBtu/h (Rated)
18.0 kBtu/h (Rated)
36.0 kBtu/h
*1
× Outdoor Design Temperature Correction
OK: fulfills the load 13.6 kBtu/h
OK: fulfills the load 16.7 kBtu/h
98.6ºF (37.0ºC)
30.3 kBtu/h
80.6ºF (27.0ºC)
68.0ºF (20.0ºC)
13.6 kBtu/h
75.2ºF (24.0ºC)
66.2ºF (19.0ºC)
16.7 kBtu/h
250 ft
24.0 27.0 30.0
1.2
1.0
0.8
0.6
0.4
Figure 1 Indoor unit temperature correction
1.4
1.3
1.2
1.1
1.0
1.02 (Refer to Figure 1)
0.9
0.8
0.7
0.6
0.95 (Refer to Figure 1)
0.5
5
-15
Figure 2 Outdoor unit temperature correction
1.00
0.95
0.98 (Refer to Figure 2)
0.90
0.93 (Refer to Figure 3) 0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
Figure 3 Correction of refrigerant piping length
14
36.0 48.0 54.0
59 60.8 62.6 64.4 66.2 68 69.8 71.6 73.4
15 16 17 18 19 20 21 22 23
Indoor Temperature
To be used to correct indoor unit only
14 23 32 41 50 59 68 77 86 95
-10 -5 0 5 10 15 20 25 30 35
Outdoor Temperature
To be used to correct outdoor unit only
Total capacity of indoor unit
0 50 100 150 200 250 300 350 400 450 500
Piping equivalent length (ft)
(kBtu/h)
72.0
75.2 [°FW.B.]
24 [°CW.B.]
Indoor
Temperature
19.4°C (67.0°F) W.B
[°F D.B.]
104 113
[°C D.B.]
40 45
18 [kBtu/h]
27 [kBtu/h]
36 [kBtu/h]
46.8 [kBtu/h]
550 600