Test Operation & Troubleshooting & Maintenance 
 
5.3 Repair 
5.3.1 Key Components 
It is the heart of the cooling system, mainly used to turn the 
low-temperature, low-pressure refrigerant vapor to 
high-temperature high-pressure vapor and then discharge it to 
the evaporator. The two-stage enthalpy-adding compressor is 
adopted herein, which can improve the heating performance of 
the unit largely. 
Electrostatic 
Expansion Valve 
It is one of four main components and used to turn the 
hi-pressure liquid refrigerant to low-temperature, low-pressure 
vapor-liquid mixture and adjust the refrigerant flow rate entering 
the evaporator. 
It is installed at the side of the suction line, and used to prevent 
liquid refrigerant entering the compressor, which if not avoided 
will lead to wet compression or even liquid slugging.   
It is used the switch flow direction of refrigerant and then realize 
switchover between cooling and heating. It also can be used for 
defrosting through the counterflow.