How To Process Tubing - Panasonic U-8ME1E8 Mode D'emploi

SUPPLEMENT

5. HOW TO PROCESS TUBING

The liquid tubing side is connected by a flare nut, and the gas
tubing side is connected by brazing.
5-1. Connecting the Refrigerant Tubing
Use of the Flaring Method
Many of conventional split system air conditioners employ the
flaring method to connect refrigerant tubes which run between
indoor and outdoor units. In this method, the copper tubes are
flared at each end and connected with flare nuts.
Flaring Procedure with a Flare Tool
(1) Cut the copper tube to the required length with a tube
cutter. It is recommended to cut approx. 30 – 50 cm longer
than the tubing length you estimate.
(2) Remove burrs at the end of the copper tube with a tube
reamer or file. This process is important and should be
done carefully to make a good flare.
Be sure to keep any contaminants (moisture, dirt, metal
filings, etc.) from entering the tubing. (Figs. 5-1 and 5-2)
N OT E
When reaming, hold the tube end downward and be sure that
no copper scraps fall into the tube. (Fig. 5-2)
(3) Remove the flare nut from the unit and be sure to mount it
on the copper tube.
(4) Make a flare at the end of copper tube with a flare tool.
(Fig. 5-3)
N OT E
A good flare should have the following characteristics:
● Inside surface is glossy and smooth
● Edge is smooth
● Tapered sides are of uniform length
Deburring
Before After
Fig. 5-1
Copper
tubing
Reamer
Fig. 5-2
Flare nut
Copper
tubing
Flare tool
Fig. 5-3
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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. (Fig. 5-4)
(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. (Fig. 5-5)
● 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.
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 at right:
● 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 as shown.
(Fig. 5-6)
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 table at
right.
Apply refrigerant
lubricant.
Fig. 5-4
Flare nut
Union
Fig. 5-5
Torque wrench
Spanner
Indoor unit
Outdoor unit
Fig. 5-6
Tightening torque,
Tube diameter Tube thickness
approximate
14 – 18 N · m
ø6.35 (1/4") 0.8 mm
(140 – 180 kgf· cm)
34 – 42 N · m
ø9.52 (3/8") 0.8 mm
(340 – 420 kgf· cm)
49 – 61 N · m
ø12.7 (1/2") 0.8 mm
(490 – 610 kgf· cm)
68 – 82 N · m
ø15.88 (5/8") 1.0 mm
(680 – 820 kgf· cm)
100 – 120 N · m
ø19.05 (3/4") 1.2 mm
(1000 – 1200 kgf· cm)
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.
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