Filter Drier Types

• Liquid line drier
• Suction line drier
  

Strainers:

Purpose – to collect foreign matter

Desiccant: Purpose – a material that removes and traps moisture and acids in the refrigerant liquid

Term:  ADSORB

• Process in which a substance accumulates on the surface of a solid forming a thin film one molecule thick
  
  
• Example: activated charcoal can adsorb certain gases
  
  

ABSORB

• Process in which a substance is dissolved into another substance
  
  
• Example: water absorbs Ammonia in a natural chemical process
  
  

Types of Desiccants Used:

• Silica gel
  
  
• Molecular sieve (adsorbent substances)
  
  
• Activated charcoal  (acid/wax removal)
  
  
• Activated alumina  (acid removal)
  
  

Purpose:

• Protects components from the effects of moisture
  
  
• Removes solids to prevent blockage and prevent acid build up that can cause damage
  
  

Construction:

• Sealed Core
  
  
• Replacement Core (high or normal capacity)
  
  
• Warning do not try to reconstitute (heat to remove moisture)
  
  

Refrigerant Drying Capacity

• Normally rated at approximately 75 degrees or 125 degrees F
  
  
• Drier size is based on system capacity rating
  
  
• R-22 systems require larger drier than R-12 due to the difference in the refrigerants ability to hold moisture
  
  

Refrigerants:

• Most CFC and HCFC refrigerants should be dried to a: max allowable moisture content of 15 PPM

• Most HFC refrigerants are very dry already and should be dried to a: max allowable moisture content of approximately 25 PPM
  
  
• Moisture content exceeding the above levels causes the system contamination which results in the following:
  
  
• Oil breakdown   
  
  
• Sludge
  
  
• Copper plating – acid strips off layer of copper and plates on hot bearing surface
  
  
• Motor burnouts
  
  

Installation

• Brazing: no cleaning requires if caps remain on until ready to be brazed
  
  
• Heat rapidly and direct flow away from shell * use a wet cloth
  
  

Flare Connection:

• Keep the drier capped until readily to seat the system
  
  

Liquid Line Drier Location:

• As close to evaporator inlet as possible and practical
  
  
• Should be permanent accessory to any system
  
  
• Driers are directional
  
  
• Installed upstream or down stream from moisture indicator
  
  
• Should install up stream from L.L.S. Solenoid
  
  
• Normal operation NO TD across the drier
  
  

Suction Line Driers:

Construction:

• Similar to liquid line drier
  
  
• Normally larger size than L. L. Drier
  
  
• Has access valves
  
  

Types of Desiccants Used:

• Combination of molecular sieve
  
  
• Charcoal
  
  
• Activated alumina
  
  

Use:

• Installed as close to compressor inlet as possible
  
  
• Removal or replacement determined by pressure drop across the assembly or after 72 hours of operation