Appendix Si39-303
110 General Information
7.3 Allowable Piping Length
7.3.1 Branch with refnet joint
(Connection of 8 indoor units Heat pump system)
One outdoor
unit installed
(RXYQ5 ~ 16)
Branch with refnet joint
When multiple
outdoor units
installed
(RXYQ18 ~)
a
ABCDEFG
bcdef
g
hi j kl mn
1234567
8
H2
Outdoor unit
REFNET joint (C)
Indoor units (1-8)
H1
ABC
D
EFG
ab c d e f
g
8
H2
H1
H3
P
Indoor units (1-8)
Outdoor unit
REFNET joint (A-G)
hi j kl mn
1234567
First outdoor
branch
Maximum
allowable
length
Between outdoor
and indoor units
• Actual pipe length
Pipe length between outdoor and indoor units
≤
150m
Example unit 8: a + b + c + d + e + f + g + p
≤
150m
• Equivalent length
Equivalent pipe length between outdoor and indoor units
≤
175m
(assume equivalent pipe length of refnet joint to be 0.5m, that of refnet header to be 1m,
calculation purposes)
• Total extension length
Total piping length from outdoor unit* to all indoor units
≤
300m
Between outdoor branch and outdoor unit
(Only for RXYQ18 or more)
• Actual pipe length
Piping length from outdoor branch to outdoor unit
≤
10m
(Approximately length: max 13m)
Allowable
height
length
Between outdoor and indoor units
• Difference in height
Difference in height between outdoor and indoor units (H1)
≤
50m
(Max 40m if the outdoor unit is below)
Between indoor and indoor units
• Difference in height
Difference in height between adjacent indoor units (H2)
≤
15m
Between outdoor and outdoor units
• Difference in height
Difference in height between outdoor unit (main) and outdoor unit (sub) (H3)
≤
5m
Allowable
length after
the branch
• Actual pipe length
Pipe length from first refrigerant branch kit (either refnet joint or refnet header) to indoor unit
≤
40m
Example unit 8: b + c + d + e + f + g + p
≤
40m
*If the system capacity is RXYQ18 or more, re-read to
the first outdoor branch as seen from the indoor unit.
r
t
s
Outdoor unit
r ≤ 10m
s ≤ 10m
t ≤ 10m
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