Gree GMV-Pdm450W/NaB-M

114
DC Inverter Multi
VRF Service Manual
a. Cleaning of portions for braze welding
Polishing……………………Removing metal materials at connection portion. (Removing oxidation lm using non-
woven fabric, abrasive cloth or abrasive paper)
Ungrease……………………If any oil stain is existent, acetone or spirit solvent shall be used for ungrease treatment.
At the same time, compressed air at 0.8MPa (gauge pressure) shall be used for cleaning The cleaning shall be
repeated not less than 3 times, until there is no dirt discharged.
b. Check whether clearance between pipe and connector is proper.
Put the connector into the pipe and face downward. If the connector does not fall down depending on friction force,
the clearance is considered proper.
c. Nitrogen-lled protection
● Since vigorous oxidation would occur on the surface of copper pipe at braze welding temperature, to effectively
restrain the generation of oxide coating in copper pipe, nitrogen-lled protection for copper pipe is necessary.
● After copper pipes are assembled, nitrogen shall be lled in copper pipe connectors
● Method for charging nitrogen into copper pipe
Nitrogen charging method:
Pressure is 0.5±0.1kgf/cm2. Nitrogen flow of 4~6L/min (gas flow can be sensed by hand) shall be guaranteed to
charge in work pieces.
After assembling, nitrogen begins to charge until welding is nished and will continue over 10s during cooling after
welding.
Main points of nitrogen charge(See the drawing below)
When nitrogen is charged, the press switch on the quick connector and inflator shall be closed to let nitrogen
totally lled in the pipe.
Make sure nitrogen reaches all welding connectors in order to effectively discharge air
A vent port must be available when nitrogen charge is continuously performed, or otherwise gas would escape
from gap around connector, making welding stufng difcult and prone to pores.
Nitrogen charge pipe
Copper pipe
Places requiring
protection during welding
Copper pipe
Vent port
Nitrogen( )
N
2
d. Welding heating
Notes:
● Braze welding is ame hard braze welding. Relevant safety operating regulations must be abided by.
● Conrm that nitrogen is owing through before copper pipe is heated.
● Neutral ame or slightly reducing ame shall be used for red copper braze welding. Outer ame is normally used.
Copper pipe connectors shall be heated uniformly. Take care to distribute heat in terms of dimension of pipe material.
Generally, insert pipe shall be preheated at rst for close matching and then swayed along length of connector to make
it heated uniformly until braze welding temperature is approached; then copper pipe is heated circularly to reach braze
welding temperature (copper pipe becomes light red) and at the same time brazing ller metal is added circularly to ll in
the clearance around the connector uniformly; and afterwards, the welding torch is slowly moved away from the pipe and a
small amount of brazing ller metal continues to be lled in until smooth llet is formed.
● During heating, welding rod shall not be burned directly by ame. Heating time shall not be very long.
● During welding, flame shall be controlled well on its direction and kept away from rubber casing, sponge and
cables.
e. Post-welding treatment(cooling)
●After welding, in the condition of nitrogen protection available, the connector shall be heated until the copper pipe
changes color (200-300
), i.e. annealing treatment.
● Before welding seam becomes completely solidied, welded pieces shall not be moved or shocked.
● For welded piece cooled by water, take care not to let water enter into copper pipe and try to prevent residue water