Mitsubishi Electric CITY MULTI Data Book page 339

1. Piping Design
1-2. Piping Design
Rule for piping size selection
HU
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 heat source unit listed in Table 4-2 [See the table below for the first joint of the
heat source 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 heat source 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 heat source unit and the 1st joint [A]
Select the appropriate size pipes for the selected heat source 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.
4. Checking the refrigerant charge
Calculate the amount of refrigerant to be added based on the pipe sizes selected in Items 1 through 3 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.
MEES19K187
B
C
D
Joint
d e
IU IU
E
g
f
IU IU
Header
Capped
a b c
IU IU IU
IU: Indoor unit , HU: Heat source unit
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