Mitsubishi Electric PUMY-P36NKMU3 Technical & Service Manual page 15

<Heating>
Outdoor Design Wet Bulb Temperature
Total Heating Load
Room1
Indoor Design Dry Bulb Temperature
Heating Load
Room2
Indoor Design Dry Bulb Temperature
Heating Load
<Other>
Indoor/Outdoor Equivalent Piping Length
Capacity of indoor unit
Model Number
Model 04 Model 05 Model 06 Model 08 Model 12 Model 15 Model 18 Model 24 Model 27 Model 30 Model 36 Model 48 Model 54
for indoor unit
Model
4.5
Capacity
2. Heating 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-P36NKMU3
(4) Total Indoor Units Capacity Correction Calculation
Room1
Indoor Design Dry Bulb Temperature Correction (69.8ºF)
Room2
Indoor Design Dry Bulb Temperature Correction (73.4ºF)
Total Indoor Units Capacity (CTi)
CTi = Σ (Indoor Unit Rating × Indoor Design Temperature Correction)
= 17.0 × 1.00 + 20.0 × 0.92
= 35.4 kBtu/h
(5) Outdoor Unit Correction Calculation
Outdoor Design Wet Bulb Temperature Correction (35.6ºF)
Piping Length Correction (328 ft)
Defrost Correction
Total Outdoor Unit Capacity (CTo)
CTo = Outdoor Unit Rating × G(CTi)
× Piping Length Correction × Defrost Correction
= 42.0 × 1.0 × 0.94 × 0.89
= 35.1 kBtu/h
*1 G(CTi) is used only when greater than 100% indoor model size are connected in total,
refer to STANDARD CAPACITY DIAGRAM.
Table 1 Table of correction factor at frost and defrost
Outdoor Intake temperature <W.B.°F (°C)>
Correction factor
(6) Determination of Maximum System Capacity
Comparison of Capacity between Total Indoor Units Capacity (CTi) and Total Outdoor Unit Capacity (CTo)
CTi = 35.4 > CTo = 35.1, thus, select CTo.
CTx = CTo = 35.1 kBtu/h
(7) Comparison with Essential Load
Against the essential load 34.4 kBtu/h, the maximum system capacity is 35.1 kBtu/h: Proper outdoor units have been selected.
(8) Calculation of Maximum Indoor Unit Capacity of Each Room
CTx = CTo, thus, calculate by the calculation below
Room1
Maximum Capacity × Room1 Capacity after the Temperature Correction/(Room1,2 Total Capacity after the Temperature Correction
= 35.1 × (17.0 × 1.00) / (17.0 × 1.00 + 20.0 × 0.92)
= 16.9 kBtu/h
Room2
Maximum Capacity × Room1 Capacity after the Temperature Correction/(Room1,2 Total Capacity after the Temperature Correction
= 35.1 × (20.0 × 0.92) / (17.0 × 1.00 + 20.0 × 0.92)
= 18.2 kBtu/h
Completed selecting units since the selected units fulfill the heating loads of Room 1, 2.
OCH733
Design Condition
5.6 6.7 9.0 13.5
17.0 kBtu/h (Rated)
20.0 kBtu/h (Rated)
42.0 kBtu/h
*1
× Outdoor Design Temperature Correction
43(6) 37(4) 36(2) 32(0)
1.0 0.98 0.89 0.88
OK: fulfills the load 16.3 kBtu/h
OK: fulfills the load 18.1 kBtu/h
35.6ºF (2.0ºC)
34.4 kBtu/h
69.8ºF (21.0ºC)
16.3 kBtu/h
73.4ºF (23.0ºC)
18.1 kBtu/h
328 ft
17.0 20.0 27.0
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
59
15
Figure 4 Indoor unit temperature correction
1.4
1.3
1.2
1.1
1.00 (Refer to Figure 4)
1.0
0.9
0.8
0.7
0.92 (Refer to Figure 4) 0.6
0.5
0.4
-13
-25
Figure 5 Outdoor unit temperature correction
1.00
1.0 (Refer to Figure 5)
0.94 (Refer to Figure 6)
0.95
0.89 (Refer to Table 1)
0.90
0.85
0.80
0.75
0.70
0
Figure 6 Correction of refrigerant piping length
28(−2) 25(−4) 21(−6) 18(−8) 14(−10)
0.89 0.9 0.95 0.95 0.95
15
30.0 34.0 40.0 54.0
60.8 62.6 64.4 66.2 68 69.8 71.6 73.4 75.2 77 78.8 80.6
16 17 18 19 20 21 22 23 24 25 26
Indoor Temperature
To be used to correct indoor unit only
21.1°C (70.0°F) D.B.
-4 5 14 23 32 41 50
-20 -15 -10 -5 0 5 10
Outdoor Temperature
To be used to correct outdoor unit only
Total capacity of indoor unit
50 100 150 200 250 300 350 400 450 500
Piping equivalent length (ft)
5(−15) −4(−20) −13(−25)
0.95 0.95 0.95
(kBtu/h)
60.0
[°F D.B.]
[°C D.B.]
27
Indoor
Temperature
59
[°F W.B.]
15 [°C W.B.]
550 600