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Caution Before Connecting Tubes Tightly
(1) Apply a sealing cap or water-proof tape to prevent dust or
water from entering the tubes before they are used.
(2) Be sure to apply refrigerant lubricant (ether oil) to the inside
of the flare nut before making piping connections. This is
effective for reducing gas leaks.
Apply refrigerant
lubricant.
(3) For proper connection, align the union tube and flare tube
straight with each other, then screw in the flare nut lightly at
first to obtain a smooth match.
● Adjust the shape of the liquid tube using a tube bender at
the installation site and connect it to the liquid tubing side
valve using a flare.
Cautions During Brazing
● Replace air inside the tube with nitrogen gas to prevent
copper oxide film from forming during the brazing
process. (Oxygen, carbon dioxide and Freon are not
acceptable.)
● Do not allow the tubing to get too hot during brazing.
The nitrogen gas inside the tubing may overheat,
causing refrigerant system valves to become damaged.
Therefore allow the tubing to cool when brazing.
● Use a reducing valve for the nitrogen cylinder.
● Do not use agents intended to prevent the formation
of oxide film. These agents adversely affect the
refrigerant and refrigerant oil, and may cause damage
or malfunctions.
Flare nut
Union
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 the following specified torque:
● When removing the flare nuts from the tubing connections,
or when tightening them after connecting the tubing, be sure
to use a torque wrench and a spanner.
Indoor unit
If the flare nuts are over-tightened, the flare may be
damaged, which could result refrigerant leakage and cause
in injury or asphyxiation to room occupants.
● 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 following table.
Tube diameter
ø6.35 (1/4")
ø9.52 (3/8")
ø12.7 (1/2")
ø15.88 (5/8")
ø19.05 (3/4")
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 above 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.
43
Torque wrench
Spanner
Outdoor unit
Tightening torque,
Tube thickness
approximate
16±2 N · m
{160±20 kgf · cm}
38±4 N · m
{380±40 kgf · cm}
55±6 N · m
{550±60 kgf · cm}
75±7 N · m
{750±70 kgf · cm}
110±10 N · m
{1100±100 kgf · cm}
0.8 mm
0.8 mm
0.8 mm
1.0 mm
1.2 mm
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