Si39-303
Installation
General Information
31
3.2.6
Vacuum Drying
What is vacuum
drying?
Vacuum drying is:
“The use of a vacuum pump to vaporize (gasify) the moisture (liquid) inside the pipes and expel it leaving
the pipes completely dry inside.”
At 1 atm (760 mmHg) the boiling point (evaporating temperature) of water is 100°C but if a vacuum is
created inside the pipes using a vacuum pump then the boiling point is rapidly reduced as the degree of the
vacuum is increased. If the boiling point is reduced to a level below that of the ambient temperature then
the moisture in the pipes will evaporate.
The evacuation of air conditioner piping provides the following effects.
1. Vacuum drying
2. Removes air and nitrogen (used in air-tightness test) from the inside of pipes.
Therefore, it is necessary to ensure that the both purposes have been achieved in the vacuum drying
operation.
<Example>
When outside temperature is 72°C
As shown in the table on the right, the degree
of vacuum must be lowered below –75.2mmHg.
Boiling point
of water (°C)
Pressure
∗
mmHg
Pa
Torr
40
–705
7333
55
30
–724
4800
36
26.7
–735
3333
25
24.4
–738
3066
22
22.2
–740
2666
20
20.6
–742
2400
18
17.8
–745
2000
15
15.0
–747
1733
13
11.7
–750
1333
10
→
7.2
–752
1066
8
0
–755
667
5
Above figures (mmHg) are gauge pressure readings.
Key points
Lower the degree of vacuum to below –755mmHg
(V1216)
Summary of Contents for VRV II Series
Page 6: ...Si39 303 iv Table of Contents...
Page 31: ...Si39 303 Installation General Information 25 Flaring Procedure...
Page 124: ...Appendix Si39 303 118 General Information 3P114237A...
Page 141: ...Si39 303 Appendix General Information 135 RXYQ8MY1B RXYQ10MY1B RXYQ12MY1B 4D040338A...
Page 142: ...Appendix Si39 303 136 General Information RXYQ14MY1B RXYQ16MY1B 4D040339A...
Page 144: ...Appendix Si39 303 138 General Information 7 11 Wiring Diagrams 7 11 1 Outdoor Unit RXYQ5MY1B...
Page 145: ...Si39 303 Appendix General Information 139 RXYQ8MY1B RXYQ10MY1B RXYQ12MY1B 3D038582...
Page 146: ...Appendix Si39 303 140 General Information RXYQ14MY1B RXYQ16MY1B 3D038058...
Page 147: ...Si39 303 Appendix General Information 141 7 11 2 Field Wiring RXYQ5 16MY1B 3D040746...
Page 148: ...Appendix Si39 303 142 General Information RXYQ18 32MY1B 3D040747...
Page 149: ...Si39 303 Appendix General Information 143 RXYQ34 48MY1B 3D040748...
Page 158: ...Appendix Si39 303 152 General Information...
Page 180: ...Refrigerant Piping Si39 303 174 Installation Manual...
Page 226: ...Troubleshooting Si39 303 220 Operation Manual...