21
5-2. Connecting Tubing Between Indoor and Outdoor
Units
(1) Tightly connect the indoor-side refrigerant tubing extended
from the wall with the outdoor-side tubing.
(2) To fasten the flare nuts, apply specified torque as shown in
the table below.
● When removing the flare nuts from the tubing connections,
or when tightening them after connecting the tubing, be sure
to use 2 adjustable wrenches or spanners. (Fig. 5-6)
If the flare nuts are over-tightened, the flare may be
damaged, which could result refrigerant leakage and cause
injury or asphyxiation to room occupants.
Fig. 5-6
● For the flare nuts at tubing connections, be sure to use the
flare nuts that were supplied with the unit, or else flare nuts
for R410A (type 2). The refrigerant tubing that is used must
be of the correct wall thickness as shown in the table below.
Tube diameter
Tightening torque
(approximate)
Tube thickness
ø6.35 (1/4")
14 – 18 N · m
(140 – 180 kgf · cm)
0.8 mm
ø9.52 (3/8")
34 – 42 N · m
(340 – 420 kgf · cm)
0.8 mm
ø12.7 (1/2")
49 – 55 N · m
(490 – 550 kgf · cm)
0.8 mm
ø15.88 (5/8")
68 – 82 N · m
(680 – 820 kgf · cm)
1.0 mm
ø19.05 (3/4")
100 – 120 N · m
(1000 – 1200 kgf · cm)
1.2 mm
Because the pressure is approximately 1.6 times higher than
conventional refrigerant pressure, the use of ordinary flare nuts
(type 1) or thin-walled tubes may result in tube rupture, injury, or
asphyxiation caused by refrigerant leakage.
● In order to prevent damage to the flare caused by over-
tightening of the flare nuts, use the table on this page as a
guide when tightening.
● When tightening the flare nut on the liquid tube, use an
adjustable wrench with a nominal handle length of 200 mm.
Torque wrench
Spanner
Indoor unit
Outdoor unit
5-3. Insulating the Refrigerant Tubing
Tubing Insulation
● Standard Selection of Insulation Material
Under the environment of the high temperature and high
humidity, the surface of the insulation material is easy to
become condesation. This will result in leakage and dew
drop. Refer to the chart shown below when selecting the
insulation material. In case that the ambient temperature and
relative humidity are placed above the line of the insulation
thickness, the condensation may occasionally make a dew
drop on the surface of the insulation material. In this case,
select the better insulation efficiency.
* However, since the condition will be different due to
the sort of the insulaton material and the environmental
condition of the installation place, see the chart shown
below as a reference when making a selection.
Standard Selection of Tubing Insulation
Calculating condition
Sort of insulation material
Polyethylene heat resisting
material
Thermal conductivity of
insulation material
Based on JIS A9501
Calculating formula used
when calculating thickness
Based on JIS A9501
Refrigerant temperature 2°C
40
10 20 304050 1020 304050
10 20 30405010 20 304050
10 20 304050
50
60
70
80
90
100
o6.35
40
50
60
70
80
90
100
o9.52
40
50
60
70
80
90
100
o12.7
40
50
60
70
80
90
100
o15.88
40
50
60
70
80
90
100
o19.05
Fig. 5-7
Thickness
30 mm
Thickness
20 mm
Thickness
10 mm
Ambient relative humidity [%]
Ambient relative humidity [%]
Thickness
30 mm
Thickness
20 mm
Thickness
10 mm
Ambient relative humidity [%]
Ambient relative humidity [%]
Thickness
30 mm
Thickness
20 mm
Thickness
10 mm
Thickness
30 mm
Thickness
20 mm
Thickness
10 mm
Ambient relative humidity [%]
Thickness
30 mm
Thickness
20 mm
Thickness
10 mm
Liquid tubing Gas tubing
Insulation
Ambient temperature [°C] Ambient temperature [°C]
Ambient temperature [°C]Ambient temperature [°C]
Ambient temperature [°C]
Two tubes arranged together
MiniVRFeng.indd21MiniVRFeng.indd21 2011/08/2613:45:202011/08/2613:45:20
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