AC System Driers

There are four main types of driers found in AC systems.   They can be identified based on their location in the system.

  1. Accumulator – located in the circuit between the evaporator and the compressor in a system using an orifice tube as the expansion device – a typical cycling clutch orifice tube system (CCOT).
  2. Receiver – located in the circuit between the condenser and the thermal expansion valve (TXV).
  3. Sub-cool Receiver – located between the second to last pass and the last pass in a parallel flow condenser.
  4. Desiccant Bag or Cartridge – same location as #3 but used to service parallel flow condensers with receiver tanks that are brazed permanently to the condenser.



Accumulator                 Receiver             Sub-cool Receiver           Desiccant Bag


In order to properly service an AC system and return it to near factory condition each component should be cleaned of all residual oil and debris before re-assembly, evacuation, and recharge.   Since it is impossible to clean a drier one should always replace them.

Driers have a limited capacity for absorbing and retaining moisture and once they are saturated they cannot protect the refrigerant circuit. Most driers also incorporate a filter screen which traps debris from other components such as normal wear particles from the internal parts of the compressor.  

Another reason for replacing the drier when a system is serviced is to remove contaminated refrigerant oil they have collected.   PAG oil that is saturated with moisture or other contaminants will not provide proper lubrication for the compressor.

In actual practice drier types 3 & 4 are always used in systems which have parallel flow condensers (PFC).   Since these condensers cannot be cleaned they often require replacement and the new condenser will generally be supplied with an attached drier.   For more information about these types of condensers please refer to the tech tip titled “Condensers with Integrated Receiver Driers”.




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