Hot Gas Line Design and Installation

• Common goal: Limit Hot Gas Line pressure drop to 2 F (equivalent pressure drop)

Goals

• Ensure oil leaving compressor travels to the condenser
  
  
• Avoid trapping
  
  
• Use proper vibration devices
  
  
• Use noise dampening devices
  
  
• Prevent refrigerant and oil from returning to the compressor during the off-cycle
  
  
• Ensure a minimum gas velocity of 500 Fpm. for horizontal runs
  
  
• Ensure a minimum gas velocity of 1000 Fpm. for vertical runs
  
  
• A trap at the base of all hot gas risers over 8 ft. (good to 25 ft.)
  
  
• Use double hot gas riser if system capacity can be reduced to 50% of full load
  

• Ensure a max gas velocity of 4000 fpm. is not exceeded
  
  
• Pitch all horizontal runs ½” per 10 ft. in the direction of flow
  
  
• Avoid bull heading of common discharge
  
  
• Result of bull heading….excessive noise, vibration, excessive pressure drops migration to the heads
  
  
  FOLLOW CODE REQUIREMENTS
  
  

Purpose of traps on the riser

• Collect any oil on the riser during off cycle
  
  
• As it starts back up oil is collected by high pressure refrigerant and atomizes
  
  
• Above 25 ft. or more (DOUBLE TRAP)
  
  
• Second trap is placed half way to the top
  
  
• To collect extra oil (no slugging)
  
  

Purpose of the inverted trap

• Prevent oil going up secondary from dropping down primary (always on larger  diameter riser tube)

To Avoid Bull Heading (on common discharge)

• Use tee as a y (y’s are very expensive)