Daikin VRV II Series, Design, Installation & Testing Instructions, Page: 39 / 242

Si39-303 Installation
General Information 33
2. Vacuum pump maintenance
Because of their nature, most vacuum pumps contain large amounts of oil which lubricates bearings, etc.,
and functions to enhance airtightness of pistons. When using a vacuum pump to discharge air from
refrigerant piping, moisture in the air tends to get mixed in with the oil. You must therefore change oil
periodically and make sure the proper oil level is maintained. (Perform periodic inspections in accordance
with the operating instructions.)
3. Degree of vacuum measurement
An extremely accurate vacuum gauge is required to test degree of vacuum. You cannot accurately
measure degree of vacuum with the compound gauge on the gauge manifold. A Pirani vacuum gauge is
required to measure degree of vacuum accurately. Because Pirani gauges are very sensitive and require
extreme care when using, they are not very suitable for use in the field. You should therefore use the Pirani
gauge to calibrate the attached vacuum gauge on the gauge manifold and the degree of vacuum of the
vacuum pump.
4. Calibration method
1. Connect a Pirani vacuum gauge and the gauge manifold vacuum gauge (0 - 760 mmHg) to the vacuum
pump at the same time, and run the pump for about 3 minutes.
2. Make sure the reading of the Pirani vacuum gauge is 5 Torr (667 Pa) or less. The reading of
conventional vacuum pumps lowers to about 0.2 Torr.
If the reading is not 5 Torr or less, check the vacuum pump oil. (Oil is low in many cases.)
3. Check the attached gauge on the gauge manifold. Adjust the gauge if the reading is not exactly correct.
4. Adjust the gauge manifold valve so that the Pirani vacuum gauge reads 5 Torr.
5. Mark the position indicated by the gauge manifold gauge with an oil based ink pen.
6. Use the mark of the gauge manifold as a target when vacuuming in the field.
(Reference) Types of vacuum pump with respective maximum degree of vacuum
Type
Maximum Degree of Vacuum Use
Expulsion Capacity Vacuum Drying Air Expulsion
Oil Rotary
(Oil Using)
0.02 mmHg
100 l/min
Suitable Suitable
Oilless Rotary
(No Need of Oil)
10 mmHg
50 l/min
Unsuitable Suitable
0.02 mmHg
40 l/min
Suitable Suitable
←
Many handy
pumps fall into this
category