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12. PIPING DESIGN
12-2. Piping Design
Rule for piping size selection
OU
A
1st Joint
1. Selecting joints
Select joints from Table 4-1 [Selection criteria for joints] based on the total capacity of indoor units on the downstream side.
When selecting the first joint for the system to which the outdoor unit listed in Table 4-2 [See the table below for the first joint of the
outdoor unit described below.] is connected, select the first joint from Table 4-2.
2. Selecting headers
Select headers from Table 5 [Header selection rule] based on the number of indoor units to be connected.
Refer to Table 5, which shows the total capacity limits, for the indoor units to be connected on the downstream side.
When connecting a header directly to the outdoor unit, select the header by referring to the notes in Table 5.
*The piping cannot be branched on the downstream of the header.
3. Selecting refrigerant pipe sizes
(1) Between outdoor unit and the 1st joint [A]
Select the appropriate size pipes for the selected outdoor unit from Table 1 [Piping "A" size selection rule].
(2) Between joints [B, C, D, and E]
Select the appropriate size pipes from Table 2 [Piping "B", "C", "D", ... size selection rule] based on the total capacity of indoor units on
the downstream side.
(3) Between joints and indoor units [a, b, c, d, e, f, and g]
Select the appropriate size pipes from Table 3 [Piping "a", "b", "c", "d", ... size selection rule] based on the capacity of indoor units.
(4) After selecting the pipe sizes in accordance with steps (1) through (3) above, if the size of the pipes on the downstream is larger than that
on the upstream, it is not necessary to be bigger than the upstream one.
(5) If any of the following applies to the selection made in Item 3-(1)-(4) above, reselect the pipe size.
(Not applicable to some models)
(a) If the length of the pipe to any indoor unit from the first joint exceeds 40 m [131 ft.], use one size larger liquid pipe after the joint that is
located before the point where the pipe length exceeds 40 m [131 ft.].
(b) Set indoor unit(s) which is vertically closer to the outdoor unit as "base unit(s)".
Only the indoor units that have a height difference of more than 15 m [49 ft.] from base unit will be termed "Target units".
Use one size larger liquid pipe from the target units to the joint prior to which 15 m [49 ft.] height difference has exceeded.
(Not applicable to the liquid pipes whose sizes were increased under item (5)-(a)).
(6) Calculate the amount of refrigerant to be added based on the pipe sizes selected in Items 1 through 3-(5) above, and make sure that the
total amount of the initial charge and the additional charge combined will not exceed the maximum allowable refrigerant charge amount.
If this amount exceeds the maximum allowable amount, redesign the system (i.e., piping length) so that the total refrigerant charge will not
exceed the maximum allowable amount.
MEES23K040
B
C
D
Joint
d
e
IU
IU
E
g
f
IU
IU
Header
Capped
a
b
c
IU
IU
IU
IU: Indoor unit , OU: Outdoor unit
Y-Series
181
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