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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 that 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 each end of the copper tubing 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)
Deburring
Before
After
Fig. 5-1
NOT 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 the copper tube with a flare tool.
(Fig. 5-3)
NOT E
A good flare should have the following characteristics:
● inside surface is glossy and smooth
● edge is smooth
● tapered sides are of uniform length
Copper
tubing
Reamer
Flare nut
Copper
tubing
Flare tool
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 on 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
Fig. 5-2
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
Fig. 5-3
from the wall with the outdoor-side tubing.
Indoor Unit Tubing Connection (
Indoor unit type
Gas tubing (mm)
Liquid tubing (mm)
(2) To fasten the flare nuts, apply specified torque.
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 in refrigerant leakage and cause injury or
asphyxiation to room occupants.
14
Apply refrigerant lubricant.
Flare nut
Union
,
...
1
2
200
ø25.4
ø9.52
Torque wrench
Indoor unit
Outdoor unit
Fig. 5-4
Fig. 5-5
)
n-1
250
ø25.4
ø12.7
Spanner
Fig. 5-6
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