Mitsubishi Electric PUZ-WZ50VAA Service Manual page 10

(9) Remove the repair parts of the outdoor unit
Be sure to work according to the section "11 DISASSEMBLY PROCEDURE" of this service manual.
(10) Brazing a new parts
• Processing brazing connections
Conduct appropriate brazing as shown in the following table.
B
* When using silver solder, a gap of 0.05 - 0.1 mm provides the strongest connection.
• Non-oxidized brazing using nitrogen replacement method (nitrogen purging)
If nitrogen is not passed through the piping, a large oxide layer will form on the inner surface. This oxide layer may
cause blockage of the electromagnetic valve, capillary tubes and accumulator oil-return hole, as well the oil pump suc-
tion opening inside the compressor.
This may prevent normal operation. As a preventative measure to stop this, it is necessary to replace the air inside the
piping with nitrogen at the time of brazing. It is a very important task during the refrigerant piping brazing process.
Use nitrogen only. Do not use oxygen, carbon dioxide, HFCs, and HCs.
- The nitrogen gas pressure is to be 0.02 MPa or less.
- Oxygen: Causes refrigerant oil deterioration due to oxidation.
- Carbon dioxide: Degrades drying properties.
- HFCs: If contact with an open flame is made, toxic gas is generated. R32 is lower flammable, leakage may cause fire.
- HCs: If contact with an open flame, fire or explosion occur.
Be sure to use a pressure-reduction valve (regulator)
< Work method >
• Brazing work
Using the nitrogen replacement method is basic for brazing.
After brazing, remove the flux. (If the chlorine in the flux is left inside the piping, it will cause the refrigerant oil to deterio-
rate.)
Be sure there is appropriate ventilation and is not R290 refrigerant near the working area when performing brazing
work. Before and during working, be sure to check the area for refrigerant leaks with a suitable refrigerant detector.
Do not braze the pipe and unit which contain refrigerant.
Do not use low temperature solder alloy in the case of brazing the refrigerant pipes.
When brazing, point the pipe horizontally or downward. Avoid pointing it upward as much as possible to prevent leak-
age.
OCH816
<Minimum insertion depth and gap for copper pipe joints>
Pipe outer diameter (D)
More than 5, less than 8
More than 8, less than 12
More than 12, less than 16
A D
More than 16, less than 25
More than 25, less than 35
More than 35, less than 45
More than 45, less than 53
Brazing point
Nitrogen
Minimum insertion depth (B) Gap* (A-D) × 1/2
6
7
8
10
12
14
16
Pressure reduction valve
(regulator)
Taping Valve
10
Unit: mm
0.05 ~ 0.35
0.05 ~ 0.45
0.05 ~ 0.55
0.05 ~ 0.55
Nitrogen
Continued to the next page.