Design of 3WAY VRF SYSTEM
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- 11
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1. Model Selecting and Capacity Calculator
Calculating the actual capacity of each indoor unit
Because the capacity of a multi air-conditioner changes according to the temperature conditions, tubing length, elevation dif-
ference 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.
Find the outdoor unit capacity correction coefficient for the following items.
(1) Capacity correction for the outdoor unit model
The capacity correction coefficient is 1.00.
(2)
Cooling:
Capacity correction for the outdoor unit temperature conditions
Heating:
(3) Capacity correction for the outdoor unit tubing length and elevation difference
(4) Capacity correction for outdoor unit frosting/defrosting during heating
Find the indoor unit capacity correction coefficient for the following items.
(2) Capacity correction for the indoor unit temperature conditions
(3) Capacity distribution ratio based on the indoor unit tubing length and elevation difference
First, in the same way as for the outdoor unit, use the tubing length and elevation difference for each indoor unit to find the
correction coefficient from the graph of capacity change characteristics on page
2
-14. Then divide the result by the outdoor
unit correction coefficient to find the capacity distribution ratio for each indoor unit.
<Cooling>
Outdoor unit corrected cooling capacity (5) = Outdoor unit rated cooling capacity × Correction coefficient for model ((1)
Page
2
-11) × Correction coefficient for outdoor temperature conditions ((2)
Page
2
-13) × Correction coefficient for tubing length and elevation difference
((3) Page
2
-14)
* However, if the outdoor unit corrected cooling capacity [5] is greater than 100%, then the outdoor unit corrected cooling
capacity [5] is considered to be 100%.
Corrected cooling capacity of each indoor unit (5) = Rated cooling capacity for that indoor unit × Correction coefficient for
indoor temperature conditions at that indoor unit ((2) Page
2
-14) × Distribution ratio based on tubing length and elevation dif-
ference at that indoor unit ((3) Page
2
-14)
However, the corrected cooling capacity of each indoor unit is found as shown below.
1-8. Calculation of Actual Capacity of Indoor Unit
1. Outdoor unit capacity correction coefficient
From the graph of capacity characteristics on page
2
-13 ( Graph of Outdoor Unit Capacity Characteristics),
use the outdoor temperature to find the capacity correction coefficient.
From the graph of capacity characteristics on page 2-15, use the outdoor temperature to find the capacity
correction coefficient.
* Indoor air intake temperature should be set to 68 °FDB.
From the graph of capacity change characteristics on page 2-14, use the tubing length and elevation difference to find the
capacity correction coefficient.
The outdoor unit correction coefficient is the value which corresponds to the most demanding indoor unit.
From the table on page
2
-13, find the capacity correction coefficient.
2. Indoor unit capacity correction coefficients
From the graph of capacity characteristics on page 2-14 ( Graph of Indoor Unit Capacity Characteristics), use the indoor
temperature to find the capacity correction coefficient.
Capacity distribution ratio for each indoor unit (3) = Correction coefficient for that indoor unit / Correction coefficient for the outdoor unit
The corrected capacities for the outdoor unit and each indoor unit are calculated form the formula below.
3. Calculating the corrected capacities for the outdoor unit and each indoor unit
If (2) < 100% and (2) × (3) > 100%: Corrected cooling capacity for that indoor unit [5] = Rated cooling capacity for that indoor unit
If (2) >100%: Corrected cooling capacity for that indoor unit (5) = Rated cooling capacity for that indoor unit × (2)
TD831158-00̲3WAY̲VRF̲SYS.indb 11
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Summary of Contents for U-72MF1U9
Page 118: ...Section 8 TENTATIVE ...