LG ATNH24GPLE2 User Manual page 68

SINGLE ZONE
2. Guideline for each installation process
2.7.3 Choosing a vacuum pump
The necessity for counter flow prevention
After the vacuum process of the refrigerant cycle, the inside of the hose will be vacuumed after stopping the vacuum pump,
the oil of vacuumpump may flow back. Moreover, if the vacuum pump stops during the operation for some reason.
Therefore, in order to prevent the counter flow from the vacuum pump, a check valve is reguired.
1) Vacuum pump performance
The 2 most important things for determining vacuum pump performance are as follows:
(1) Exhaust velocity
(2) Degree of vacuum
(1) Exhaust velocity
Exhaust volume is usually expressed as l/min or ft
Generally speaking, the faster the exhaust velocity, the larger and heavier the vacuum pump itself is.
Commercially available vacuum pumps (exhaust velocity of 20~30 ℓ/min(0.71~1.06 ft
long time to achieve vacuum. (We recommend a vacuum pump of approx. 60~100 ℓ/min(2.12~3.53 ft
(2) Degree of vacuum
Ultimate vacuum varies largely according to use of the vacuum pump. Vacuum pumps used for vacuum forming cannot
be used for vacuum drying. (A vacuum pump with a high degree of vacuum is required.)
When selecting a vacuum, you should select one which is capable of achieving 0.2 Torr of ultimate vacuum.
Degree of vacuum is expressed in Torr, micron, mmHg, Pascal(Pa), and psi. The units correlate as follows:
Gauge Pressure
Absolute Pressure
Torr
Micron
mmHg
hPa
psi
Degree of vacuum must be within the range expressed by
0 Torr
0 hPa
0 mmHg
0 psi
Perfect vacuum
32 _
Heat pump 60Hz/R410A
3 /min. The larger the number, the faster the vacuum is achieved.
Unit Standard atmospheric pressure
kg/cm 2
kg/cm 2 abs
Torr
Micron
mmHg
hPa
psi
5 Torr
6.67 hPa
5 mmHg
0.096 psi
Vacuum target value
3 /min) usually take an extremely
0
1.033
760
760000
760
1013.33
14.70
1013.33 hPa
760 mmHg
14.70 psi
Standard atmospheric pressure
3 /min)
Perfect vacuum
-1.033
0
0
0
0
0
0
760 Torr