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2. Allowable piping length
3. Additional limitations for twin-type
• Maximum allowable one-way piping length is the larger
numerical value between (Lo + La) and (Lo + Lb).
• For twin type, only the main piping can be reused among
the existing piping. Brandnew standard pipe should be
installed for branch pipe/branch piping.
10.1.7. Connecting The Pipes
• Use a clean pipe which does not include water or dust for inside of piping.
• When cutting the refrigerant pipes, a piping cutter must be used. Before connecting the refrigerant pipes, blow nitrogen and blow
off dust in the pipes.
(Never use tools which cause a lot of dust such as a saw and a magnet.)
• When waxing replace nitrogen inside the piping after removing dirt and dust. (In order to prevent oxidization scale from forming
inside the piping).
• The refrigerant pipes are of particular importance.
The installation work for refrigerant cycles in separate-type air conditioners must be carried out perfectly.
• Set the lower limit of the allowable pipe length to 7.5m.
If the pipe is shorter than 7.5m, the refrigerant may become overfilled and a problem such as abnormal high pressure could
occur.
1. Refer to the table below for the pipe diameters equivalent lengths and indoor/outdoor unit difference of elevation.
Pipe diameter Gas side Standard
Liquid side 1 size down Standard 1 size up
Allowable piping length (min. ~ max.) 7.5m ~ 10m 7.5m ~ 30m 7.5m ~ 15m
Height difference
between indoor and
outdoor unit
Outdoor unit is
located on upper side
5m or less 25m or less 15m or less
Outdoor unit is
located on lower side
5m or less 20m or less 10m or less
Pipe diameter Gas side Standard
Liquid side 1 size down Standard 1 size up
Allowable piping length Lo + La + Lb 7.5m ~ 10m 7.5m ~ 30m 7.5m ~ 15m
Max. allowable
one-way piping length
Lo + La
Lo + Lb
10m or less 20m or less 10m or less
Branch pipe length La , Lb 5m or less 10m or less 10m or less
Difference in branch
pipe lengt
La - Lb 3m or less 5m or less 5m or less
Height
difference
H2
Height
difference
between indoor
and outdoor
unit
Outdoor unit is
located on upper side
5m or less 25m or less 15m or less
Outdoor unit is
located on lower side
5m or less 20m or less 10m or less
H1 Height difference between indoor units 0.5m or less 0.5m or less 0.5m or less
Outdoor unit on upper side Outdoor unit on lower side
Pipe diameter (mm) Equivalent
length (m)
Difference of
elevation (m)
Difference of
elevation (m)
Liquid-side pipes Gas-side pipes
ø9.52 x t1.0 ø15.88 x t1.2 30 25 20
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