Mitsubishi Electric PUZ-WZ50VAA Service Manual page 11

OK
Brazing filler metal
Downward
Make sure to prevent fire. (Cover area around brazing point and prepare fire extinguisher/water.)
Take care to avoid burning yourself.
Confirm that the pipe and joint gap is appropriate to prevent leakage.
(11) Airtightness Test
In order to pressurize the refrigerant piping to the air conditioner's designed pressure using nitrogen gas, connect equip-
ment as shown in the following diagram.
< Connection diagram for airtightness testing devices >
Do not use chlorine-based refrigerant or oxygen/combustible gas as pressurized gas under any circumstances. (Using
oxygen as pressurized gas will cause an explosion).
Do not pressurize to the designed pressure all at once. Instead, pressurize gradually in multiple steps.
STEP 1
Pressurize to 0.5 MPa (5 kgf/cm
pressure.
STEP 2
Pressurize to 1.5 MPa (15 kgf/cm
STEP 3
Next, increase pressure to the designed pressure of the air conditioner and record the ambient temperature and
pressure. Leave for approximately one day at the designed pressure. If the pressure does not drop, the test is successful.
Be careful to consider pressure increases and decreases based on ambient temperature.
If there is a loss in pressure, there is a leak. Find the leak and repair it.
If there is a leak, check welding points using soapy water, etc.
(12) Vacuum Drying
It needs to carry out vacuum drying to remove the air, moisture and nitrogen gas used during the airtightness test, etc. in
the pipes.
- If the air is mixed into the refrigerant circuit, the pressure will rise to an abnormally high, which may cause compressor
malfunction.
- If a small amount of moisture (atmospheric moisture) is mixed into the refrigerating circuit, this may cause air condi-
tioner malfunction.
- If moisture is mixed into the refrigerant circuit, it may freeze in the expansion valve and cause air conditioner malfunc-
tion.
Connect equipments refer to the below diagram.
Remove a sufficient level of pressure using vacuum pump.
The refrigerant oil used in refrigerant circuit has high moisture absorbency, and has the characteristic of generating acidic
OCH816
OK
Brazing filler metal
Horizontally
Gauge manifold
Nitrogen
Lo knob
gas
2
), stop pressurization, wait for at least five minutes, and confirm that there is no loss in
2
), wait again for at least five minutes and confirm that there is no loss in pressure.
11
NG
Brazing filler
metal
Upward
Service port
Hi knob
(Outdoor unit)
Continued to the next page.