Introduction:
A receiver-drier is used when a thermostatic expansion valve metering device is used and is positioned between the condenser and the thermostatic expansion valve. The accumulator is fitted between the evaporator and the compressor.
The receiver-drier
The function of the receiver drier is as follows:
1. To ensure the system is free from dirt preventing any excessive wear or premature failure of components.
2. To remove moisture from the refrigerant ensuring no ice can form on any components within the system which may cause a blockage and to ensure no internal corrosion can form.
3. To act as a temporary reservoir to supply the system under varying load conditions.
4. To allow only liquid refrigerant to flow to the expansion valve.
5. To act as a point for diagnostics (sight glass sometimes fitted).
Operation
Sight glass
A sight glass is not used on R134a systems because the refrigerant has a cloudy appearance in its normal condition.
Fusible plug (pressure relief valve)
If adequate cooling of the condenser is not provided or the cooling load becomes excessive a fusible plug will release the excessive pressure to reduce the possibility of a burst pipe. The fusible plug contains metal which has a melting point of approximately 100–110°C.
Pressure relief valve
The problem with a fusible plug is that once the metal melts you lose the full contents of the refrigerant.
Accumulator
An accumulator is used when an FOV metering device is used. The accumulator is fitted between the evaporator and the compressor. The function of the accumulator is as follows:
1. To ensure that the refrigerant leaves the accumulator as a vapour and not a liquid state for the compressor to induce.
2. To ensure it is free from dirt to stop any excessive wear or premature failure of components.
3. To remove moisture ensuring no ice can form on any components within the system which may cause a blockage and to ensure no internal corrosion can form.
4. To act as a temporary reservoir to supply the system under varying load conditions.
5. To add lubricating oil for system components like the compressor.6. Often to house the low pressure switch/sensor.
Operation