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Here is the instruction show you guide on how to charge air conditioner with refrigerant for HITACHI EX5600 excavator.

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Necessity of Purging
The following problems can arise if air or other gases remain in the air conditioning circuit. Be sure to perform purging the air conditioner circuit with a vacuum before charging with refrigerant (R134a).

1. Pressure rise in the high pressure side
If air remains in the air conditioner circuit, this disturbs the heat exchange between refrigerant and air in the condenser. This causes pressure to rise in the high pressure side (compressor side).
 

Refrigerant gas is easily liquefied, but air cannot be liquefied and remains as a gas in the condenser because the temperature at which air liquefies is extremely low. Therefore, liquidation of the refrigerant gas in the condenser decreases by the amount of air in the circuit, and the gas pressure in the high pressure side increases accordingly.
 

2. Metal corrosion
If air remains in the air conditioner circuit, a chemical reaction between refrigerant and moisture in the air takes place, and as a result, hydrochloric acid is produced. Hydrochloric aid corrodes metals such as aluminum, copper and iron.
3. Plugging of the expansion valve by moisture When high pressure refrigerant gas passes through the expansion valve, gas pressure decreases and temperature drops. Moisture included in high pressure refrigerant gas in the air conditioner circuit freezes at the expansion valve orifice, plugging refrigerant flow.
Operation of the air conditioner becomes unstable and cooling efficiency lowers. 

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