Airtightness Test; Vacuuming - Mitsubishi City Multi PURY-P400 Service Handbook

[4] Airtightness Test

No changes from the conventional method. Note that a refrigerant leakage detector for R22 cannot detect R407C
leakage.
NO
Items to be strictly observed :
1. Pressurize the equipment with nitrogen up to the design pressure and then check the equipment's airtightness,
taking temperature variations into account.
2. When investigating leakage locations using a refrigerant, be sure to use R407C.
3. Ensure that R407C is in a liquid state when charging.
Reasons :
1. Use of oxygen as the pressurized gas may cause an explosion.
2. If gas refrigerant is used, the composition of the remaining refrigerant in the cylinder will change and this refrigerant
will become unusable.
Note :
• A leakage detector for R407C is sold commercially, and it should be purchased.
[5]

Vacuuming

1. Vacuum pump with check valve
A vacuum pump with a check valve is required to prevent the vacuum pump oil from flowing back into the refrigerant
circuit when the power supply is cut off due to power failure. A check valve may be added to a vacuum pump not
equipped with one.
2. Standard degree of vacuum for the vacuum pump
Use a pump which reaches 0.5 Torr (500 MICRON) or below after 5 minutes of operation.
Be sure to use a vacuum pump that has been properly maintained and oiled with the specified oil. If the vacuum pump
is not properly maintained, desired degree of vacuum may not be achieved.
3. Neccessary accuracy of the vacuum gauge
Use a vacuum gauge that can measure up to 5 Torr. Do not use a general gauge manifold since it cannot measure a
vacuum of 5 Torr.
4. Evacuating time
• Evacuate the equipment for 1 hour after –755 mmHg (5 Torr) has been reached.
• After envacuating, leave the equipment for 1 hour and make sure that the vacuum is not lost.
5. Operating procedure when the vacuum pump is stopped
In order to prevent a backflow of the vacuum pump oil, open the relief valve on the vacuum pump side or loosen the
charge hose to drawn in air before stopping operation.
The same operating procedure should be used when using a vacuum pump with a check valve.
Halide torch
NO
R22 leakage detector
–7–