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• Comparison with essential load
Against the essential load 67.5 kBtu/h, the maximum system capacity is 68.35 kBtu/h: Proper indoor units have been
selected.
• Calculation for the maximum indoor unit capacity of each room
When CTx = CTo, use the calculation formula below.
Room1: CTx × Corrected capacity for Room1/CTi
= 68.35 × (34.0 × 1.00)/70.8
= 32.8 kBtu/h
The capacity is enough for the heating load of Room 1 (32.2 kW): A proper indoor unit is selected.
Room2: CTx × Corrected capacity for Room1/CTi
= 68.35 × (40.0 × 0.92)/(70.8)
= 35.5 kW
The capacity is enough for the heating load of Room 2 (35.3 kW): A proper indoor unit is selected.
Note:
• The selection of units is completed when proper units are selected.
5-1-3. Power input of outdoor unit
• Outdoor unit: MXZ-SM72TAM
• Indoor unit 1: PEFY-P30
Indoor unit 2: PEFY-P36
■ Cooling
• Nominal power input of outdoor unit
• 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. 64.4°F [18.0°C] W.B.)
0.93 (Refer to Figure 2 in 5-2-1)
- 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.)
0.93 (Refer to Figure 2 in 5-2-1.)
- Average indoor temp. power input coefficient (Cave) =
n:
Total number of the indoor units
k:
Number of the indoor unit
ck: Outdoor unit power input coefficient of k indoor unit room temp.
Mk: Number part of the k indoor unit model (e.g. P80: 80)
- Correction Coefficient of Indoor temperature = 0.93 × 30/(30 + 36) + 0.93 × 36/(30 + 36)
• Coefficient of the partial load ƒ(CTi)
Total indoor units capacity = 30 + 36 = 66, thus, ƒ(CTi) = 0.89 (Refer to the tables in 5-4. "Standard Capacity Dia-
gram".)
• Outdoor power input (PIo)
Maximum System Capacity (CTx) = Total outdoor unit capacity (CTo), so use the following formula:
PIo = Outdoor unit cooling nominal power input × Correction coefficient of indoor temperature × ƒ(CTi)
= 5.67 × 0.93 × 0.89
= 4.69 kW
■ Heating
• Nominal power input of outdoor unit
• Calculation of the average indoor temperature power input coefficient
- Coefficient of the outdoor unit for indoor unit 1 (Outdoor temp. 35.6°F [2.0°C] W.B., Indoor temp. 69.8°F [21.0°C]
D.B.)
1.20 (Refer to Figure 4 in 5-2-2.)
- Coefficient of the outdoor unit for indoor unit 2 (Outdoor temp. 35.6°F [2.0°C] W.B., Indoor temp. 73.4°F [23.0°C]
D.B.)
1.04 (Refer to Figure 4 in 5-2-2.)
- Average indoor temp. power input coefficient (Cave) =
n:
Total number of the indoor units
k:
Number of the indoor unit
ck: Outdoor unit power input coefficient of k indoor unit room temp.
Mk: Number part of the k indoor unit model (e.g. P80: 80)
- Correction Coefficient of Indoor temperature = 1.20 × 30/(30 + 36) + 1.04 × 36/(30 + 36)
• Coefficient of the partial load ƒ(CTi)
Total indoor units capacity = 30 + 36 = 66, thus, ƒ(CTi) = 0.9 (Refer to the tables in 5-4. "Standard capacity diagram".)
• Outdoor power input (PIo)
Maximum System Capacity (CTx) = Total Indoor unit capacity (CTi), so use the following formula
PIo = Outdoor unit heating nominal power input × Correction coefficient of indoor temperature × ƒ(CTi)
= 5.36 × 1.11 × 0.9
= 5.35 kW
OCH800A_17
5.67 kW
n
n
{Ck × (Mk/ Mk)}
k=1
k=1
= 0.93
5.36 kW
n
n
{Ck × (Mk/ Mk)}
k=1
k=1
= 1.11
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