Refrigeration Cycle

Refrigeration Cycle

The Compressor draws low pressure refrigerant from the evaporator and by compression, raises refrigerant temperature and pressure. High pressure, hot vaporized refrigerant enters the Condenser where it is cooled by the flow of ambient air. A change of state occurs as the refrigerant cools in the condenser and becomes a reduced temperature high pressure liquid.
From the condenser the liquid passes into the Receiver/Dryer which has three functions:
- Storage vessel for varying system refrigerant demand.
- Filter to remove system contaminants.
- Moisture removal via the desiccant.

With the passage through the receiver/dryer completed, the still high pressure liquid refrigerant enters the Expansion Valve where it is metered through a controlled orifice which has the effect of reducing the pressure and temperature.

The refrigerant, now in a cold atomized state, flows into the Evaporator and cools the air which is passing through the matrix.

As heat is absorbed by the refrigerant it once again changes state, into a vapor, and returns to the compressor for the cycle to be repeated.

There are two switches incorporated into the high side of the system which have the following functions:
- Trinary; This three function pressure switch, cuts electrical power to the compressor clutch if the system pressure is not in a range of 2 bar (1st function) to 27 bar (2nd function). The switch also provides a 12 volt supply to both engine cooling fans when maximum A/C cooling is required and operates at 20 bar input (3rd function).
- Pressure Switch Slow Cooling Fans; When the system pressure is 12 bar, medium A/C demand, the operation of this switch causes a 6 volt series feed to both engine cooling fans, thus providing half fan speed.

The division of HIGH and LOW side is simply the system pressure differential created by the compressor discharge (pressure), suction (inlet) ports and the relative sides of the expansion valve. This differential is critical to system fault diagnosis and efficiency checks.





1. Compressor
2. Condenser
3. Receiver/Drier
4. Expansion Valve
5. Evaporator
6. Trinary switch
7. Slow cooling fans switch