AIR CONDITIONING 26 11.9 MAIN PARTS OF A.C. SYSTEM 1. COMPRESSOR: It is the heart of A.C. system where, low temperature, low pressure vapour refrigerant is compressed and converted to high temperature high pressure gas. 2. CONDENSER: It is the place where heat dissipation takes place. Hot compressed gas enters the condenser and is cooled off and converted into high pressure liquid at the condenser outlet. 3. RECEIVER DRIER INTEGRATED WITH CONDENSER: It serves as a reservoir for excess refrigerant where it removes any traces of moisture and filters out dirt in the system. 4. LINEAR PRESSURE SWITCH: It is used to limit pressure conditions in a closed refrigerant cycle for series / parallel logic. High Low Pressure Settings: If the system Pressure reaches impermissible levels i. e. if the pressure is less than 2 ± 0.2 kg/cm2 or if the pressure is higher than 32 ± 2 kg/cm2 then the compressor is switched off. This avoids its consequential damage. Medium Pressure Settings: Due to these pressure settings, both the condenser fan and radiator fan start immediately after the A. C. is switched ON. Both the fans run at slow speed until the system pressure exceeds 20.5 kg / cm2 Above this pressure, both the fans run at full speed. When the system pressure drops below 15.5 kg / cm2, both the fans will run at slow speed. 5. EXPANSION VALVE: It senses the pressure of the refrigerant coming into the evaporator as well as the temperature of the refrigerant into the evaporator. By sensing the temperature and the pressure of the gas leaving the evaporator, the expansion valve prevents the evaporator from being flooded, and thereby returning liquid refrigerant to the compressor. 6. EVAPORATOR: It serves as a heat absorption unit. Here it removes heat from inside the vehicle and dehumidifies it. The refrigerant enters the bottom of evaporator as a low pressure liquid. The warm air passing through evaporator fins causes the refrigerant to boil; it can absorb large amounts of heat. The heat is then carried off with the refrigerant to the outside of vehicle. 7. ANTI FREEZE SWITCH: It is a temperature sensing device, which protects the A.C. systems from damage. It switches off the compressor when condensed water tends to form ice on the fins of evaporator. Thus it maintains the evaporator temperature within a specified range. 8. MAGNETIC CLUTCH: A magnetic clutch is used to connect and disconnect the compressor from the engine. Main components are stator, rotor, and pressure plate. PRINCIPLE: When the current is fed to the coil (as shown fig. B on the right), magnetic force is generated in iron II which attracts iron I.
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