Panasonic U-120MF2U9, Technical Data Manual, Page: 28 / 181

Design of 3WAY VRF SYSTEM
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1. Model Selection and Capacity Calculator
1. Model Selecting and Capacity Calculator
1-10. Calculation of Actual Capacity of Indoor Unit
Calculating the actual capacity of each indoor unit
Design of 2WAY VRF SYSTEM
Because the capacity of a multi air-conditioner changes according to the temperature conditions, tubing length,
elevation difference and other factors, select the correct model after taking into account the various correction values.
When selecting the model, calculate the corrected capacities of the outdoor unit and each indoor unit.
Use the corrected outdoor unit capacity and the total corrected capacity of all the indoor units to calculate the actual final
capacity of each indoor unit.
(A) Capacity correction for the outdoor unit temperature conditions, indoor unit temperature and indoor/ outdoor ratio (BTU/h)
Read the capacity correction for outdoor unit temperature, indoor unit temperature and indoor/ outdoor ratio as shown
in the section “8. CAPACITY TABLE”.
(B)
From the graph of capacity change characteristics resulting from tubing length and elevation difference on page “ 2-15 ”,
read the capacity correction coefficient.
* Indoor unit temperature is indoor unit rated capacity - weighted average temperature.
Rated capacity-weighted average temperature=
((a)×(b))
(a)
= 62.4 WB
* The indoor/ outdoor ratio should be selected according to the real rated capacity.
*Use the lowest capacity changing ratio. Usually, the furthest and highest or the lowest indoor unit is used.
(C)
From the graph of surplus capacity characteristics resulting from outdoor temperature on page “ 2-14 ”, read the capacity
correction coefficient.
(D)
Capacity correction coefficient for outdoor unit tubing length and elevation difference (%)
Surplus capacity correction coefficient for outdoor unit temperature conditions (%)
Capacity correction coefficient for outdoor unit frosting and defrosting during heating operation (%)
From the outdoor unit heating capacity correction coefficient during frosting / defrosting on page “ 2-14 ”, read the capacity
correction coefficient.
Example
Cooling operation
Example
There are 4 indoor units for class 9,12,15,18 and the outdoor unit type is 72 (72,000BTU/h in the cooling-mode, 81,000BTU/h
in the heating-mode).
1. Outdoor unit capacity correction
Outdoor unit capacity correction (BTU/h) = (A) × (B) × (C) × (D)
No.
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(a)Rated capacity
BTU/h
9,600
12,000
15,000
19,000
(b)Intake temperature
°F WB
66
64
62
60
(a)x(b)
633,600
768,000
930,000
1,140,000
Rated cooling capacity
BTU/h
9,600
12,000
15,000
19,000
55,600
72,000
77.2%
Rated heating capacity
BTU/h
11,000
14,000
17,000
21,000
63,000
81,000
77.8%
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4
Total
Outdoor
I/O ratio
No.
Design of 2WAY VRF SYSTEM
1. Model Selecting and Capacity Calculator
(E) Capacity correction for the indoor unit temperature conditions (BTU/h)
From the graph of indoor unit capacity characteristics on page “ 2-15 ”, read the capacity correction coefficient for indoor unit
temperature conditions.
(H)
From the graph of capacity change characteristics resulting from tubing length and elevation difference on page “ 2-15 ”,
read the capacity correction coefficient.
(E) = Capacity correction coefficient for indoor unit temperature conditions × Rated capacity
(F)
(F) =
(E)
(E)
(G)
Capacity correction coefficient for tubing length and elevation difference (%)
Calculate the Capacity distribution ratio (%)
Distribute the outdoor unit capacity among each indoor unit (BTU/h)
(G) = (A) × (F) (BTU/h)
2. Indoor unit capacity correction coefficient
Indoor unit capacity correction (BTU/h) = (G) × ( I ) × (D)
Indoor unit capacity correction ≤ (G)
7'B86$B:$<B95)LQGE
( I ) Capacity correction coefficient for outdoor unit (%)
( I ) = (H) x (C)
● In the case of (I) ≤ 100%, loss of capacity resulting from the tubing length can be supplied by the outdoor unit capacity.
●
When the outdoor air temperature is lower in cooling mode
●
When the outdoor air temperature is higher in heating mode
TD831183-00_北米向け3WAY.indb 12 15/12/17 16:05:09