Car A/C Receiver Drier

By 8 August 2014

A receiver-drier (Fig. 2.32) is used when a thermostatic expansion valve metering device is used and is positioned between the condenser and the thermostatic expansion valve.

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).

Refrigerant entering the receiver-drier in an ideal system will be in a liquid state. If the system is under heavy load the condenser may have not been efficient enough to completely condense the refrigerant.This means a small amount of vapour may be present. Liquid and vapour can enter the receiver through the inlet where it will separate. Liquid will fall to the bottom of the receiver while vapour will rise to the top.The outlet is connected to a receiver tube internally which has a pickup point at the bottom of the receiver where the filter is positioned.

The refrigerant flows through the desiccant and filter to get to the outlet pickup tube. This ensures that only liquid refrigerant flows to the expansion valve.