Refrigerant Charging 
Air purge(at the time of new installation only)
Close the gas pipe side valve by turning it clockwise.
Connect the pressure gauge to the low pressure side service valve, and then open the gas pipe side valve again.
Connect it to the refrigerant filling tank.
Start cooling operation.
Check the pressure of the pressure gauge. Check whether the low pressure side is within the range of 4.5~5.6kg/cm2G
(outside temperature 35°C).
Open the tank and refill the refrigerant until arriving at the proper pressure.
(Refill the refrigerant slowly checking the pressure.)
OUTDOOR UNIT
Gas 
pipe side
Liquid pipe side
Stop operation.
Close the gas pipe side valve, and loosen the pressure gauge connected.
Then open the gas pipe side valve again.
Tighten the cap of each valve using a specified tool.
Always use R22 refrigerant to avoid damage of the unit or an explosion.
Must keep the quantity of refrigerant by using a balance. Do not use a manometer or not depend on your experiences.