Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook

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[5] Airtightness Test
No changes from the conventional method. Note that a refrigerant leakage detector for R22 cannot detect R407C
leakage.
Halide torch R22 leakage detector
Items to be strictly observed:
1. Pressurize the equipment with nitrogen up to the design pressure and then judge 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. Charging with R407C gas will lead the composition of the remaining refrigerant in the cylinder to change and this
refrigerant can then not be used.
Note:
• A leakage detector for R407C is sold commercially and it should be purchased.
[6] 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 vacuum pump power is turned off (power failure).
It is also possible to attach a check valve to the actual vacuum pump afterwards.
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.
In addition, be sure to use a vacuum pump that has been properly maintained and oiled using the specified oil. If the
vacuum pump is not properly maintained, the degree of vacuum may be too low.
3. Required 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 the that 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.