Panasonic U-72MF1U9 Technical Data Manual page 55

5. HOW TO PROCESS TUBING
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 to the matching
surfaces of the flare and union before connecting them
together. This is effective for reducing gas leaks.
(Fig. 2-22)
(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. 2-23)
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. 2-24)
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.
Indoor unit
Tube diameter
ø1/4" (ø6.35 mm)
ø3/8" (ø9.52 mm)
ø1/2"(ø12.7 mm)
ø5/8" (ø15.88 mm)
ø3/4" (ø19.05 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 7-7/8 in.
2 - 41
Design of 3WAY VRF SYSTEM
Apply refrigerant
lubricant
Fig. 2-22
Flare nut
Union
Fig. 2-23
Torque wrench
Spanner
Outdoor unit
Fig. 2-24
Tightening torque,
Tube thickness
approximate
120 – 160 lbs·inch 1/32"
(140 – 180 kgf·cm) (0.8 mm)
300 – 360 lbs·inch 1/32"
(340 – 420 kgf·cm) (0.8 mm)
430 – 480 lbs·inch 1/32"
(490 – 550 kgf·cm) (0.8 mm)
590 – 710 lbs·inch 5/128"
(680 – 820 kgf·cm) (1.0 mm)
870 – 1040 lbs·inch over 5/128"
(1.0 mm)
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