MXZ-SM48NAMHZ Service Manual

18
OCH789
Table 1 Table of correction factor at frost and defrost
Outdoor Intake temperature <W.B.°F (°C)> 43(6) 37(4) 36(2) 32(0) 28(−2) 25(−4) 21(−6) 18(−8) 14(−10) 5(−15) −4(−20) −13(−25)
Correction factor 1.0 0.98 0.89 0.88 0.89 0.9 0.95 0.95 0.95 0.95 0.95 0.95
0 50 100 150 200 250 300 350 400 450 500 550 600
0.70
0.75
0.80
0.85
0.90
0.95
1.00
(5) Outdoor Unit Correction Calculation
Outdoor Design Wet Bulb Temperature Correction (35.6ºF)
1.0 (Refer to Figure 5)
Piping Length Correction (328 ft)
Defrost Correction
0.94 (Refer to Figure 6)
0.89 (Refer to Table 1)
Total Outdoor Unit Capacity (CTo)
CTo = Outdoor Unit Rating × G(CTi)
*1
× Outdoor Design Temperature Correction
× Piping Length Correction × Defrost Correction
= 42.0 × 1.0 × 0.94 × 0.89
= 35.1 kBtu/h
(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 OK: fulfills the load 16.3 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 OK: fulfills the load 18.1 kBtu/h
Completed selecting units since the selected units fulfill the heating loads of Room 1, 2.
Figure 6 Correction of refrigerant piping length
*1 G(CTi) is used only when greater than 100% indoor model size are connected in total,
refer to STANDARD CAPACITY DIAGRAM.
Capacity ratio
Piping equivalent length (ft)
Total capacity of indoor unit
n: Total number of the indoor units
k: Number of the indoor unit
c
k
: Outdoor unit power input coefficient of k indoor unit room temp.
M
k
: Number part of the k indoor unit model (e.g. P80 → 80)
<Cooling>
3. Power input of outdoor unit
Outdoor unit: MXZ-SM36NAM
Indoor unit 1: PEFY-P15
Indoor unit 2: PEFY-P18
(1) Rated power input of outdoor unit 2.31 kW
1.04 (Refer to “4-2. CORRECTION BY TEMPERATURE”.)
(2) Calculation of the average indoor temperature power input coefficient
Coefficient of the outdoor unit for indoor unit 1 (Outdoor temp. 98.6°F [37.0°C] D.B., Indoor temp. 68.0°F [20.0°C] W.B.)
Maximum System Capacity (CTx) = Total Outdoor unit Capacity (CTo), so use the following formula
Total Indoor units capacity
15 + 18 = 33, thus, (CTi) = 0.9 (Refer to the tables in “4-4.STANDARD CAPACITY DIAGRAM”.)
PIo = Outdoor unit Cooling Rated Power Input × Correction Coefficient of Indoor temperature × (CTi)
= 2.31 × 0.94 × 0.9
= 1.95 kW
0.85 (Refer to “4-2. CORRECTION BY TEMPERATURE”.)
Coefficient of the outdoor unit for indoor unit 2 (Outdoor temp. 98.6°F [37.0°C] D.B., Indoor temp. 64.4°F [18.0°C] W.B.)
Correction Coefficient of Indoor temperature = 1.04 × 15/(15 + 18) + 0.85 × 18/(15 + 18)
= 0.94
n
k=1
n
k=1
Average indoor temp. power input coefficient ( c
ave
) = ∑ {c
k
× (M
k
/ ∑ M
k
)}
(4) Outdoor power input (PIo)
(3) Coefficient of the partial load (CTi)