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DC Inverter Multi
VRF Service Manual
Cooling
o avoid getting a burn in following processes, common wet cloth (humidity content is low, meaning that there shall
not be water drips when welded part is cooled; and because shrinkage factor of copper is different from that of welding
material, too quick cooling that would cause cracking of braze welding shall be avoided) can be used for cooling welded
parts.
The following items shall be checked after welding is completed
● Is there any pore or hole on welded part?
● Is there evident “sagging of brazing ller metal”?
5�8 Cleaning of Refrigerant Piping
After a section of pipeline is welded, cleaning of piping is necessary.
Nitrogen pressure is utilized to remove foreign matters (such as dust, water and beryllium oxide caused by welding)
in the piping.
5.8.1 Main purposes of cleaning are as follows
To eliminate oxide caused by insufciency of nitrogen-lled protection during pipe welding.
To remove foreign substances and water that may enter the piping due to improper storage and transport.
To check whether big leakage is existent at connections of the piping between indoor unit and outdoor unit
5.8.2 Cleaning steps:
a. Mount a pressure gauge on nitrogen cylinder;
Nitrogen bottle
Outdoor side
Liquid pipe
Air pipe
The opening of the pipe not to be purged
shall be blocked with blind plug.
Indoor unit A
Outdoor unit B
b. High pressure end of the pressure gauge is connected to the refrigerant lling nozzle of the small pipe (liquid pipe).
c. All copper pipe ports outside the A side of indoor unit shall be blocked by blanking plugs
Copper pipe
Blanking plug
Block with
insulation materials
Quick release
Cleaning process
Copper pipe ports not to be cleaned
shall be blocked by blanking plugs
d. The valve on nitrogen cylinder shall be opened to maintain pressure at 28Kgf/ cm2
e. Check whether nitrogen ows through the liquid pipe of indoor unit A
f. Cleaning
The mouth of the pipe shall be blocked with insulation material held by hand until pressure rises to a level difcult
to be withstood, and at the moment the insulation material shall be released quickly. And then the mouth shall be blocked
again. Repeat such procedures several times. Afterwards, use a wood board posted with white paper to check it. If there is
not evident dirt on the white paper, the pipe will be considered clean.
g. Shut off the main valve of nitrogen
h. Repeat the above procedures on indoor unit B
i. After cleaning of liquid pipe, gas pipe shall be cleaned in the same way.
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