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Suction Pressure

Suction Pressure Too High

QuestionsCauseRemedy
Are suction lines insulated properly? i.e. from outside of box to compressor. (Hot weather)Suction lines improperly or not insulatedInsulate suction lines
Do you have the correct expansion valve?Oversized expansion valveReplace with properly sized expansion valve
Where is expansion valve bulb located?Expansion valve bulb in improper locationMove expansion valve bulb
Is expansion valve bulb insulated?Expansion valve bulb improperly or not insulatedInsulate expansion valve bulb properly
Is expansion valve in proper adjustment?Expansion valve overfeedingAdjust expansion valve until proper superheat is reached
Is system capacity sufficient for product load?Product load greater than system capacityAdd additional units or replace

 

Suction Pressure Too Low

QuestionsCauseRemedy
Is the evaporator coil clean?Dirty or iced evaporatorClean or defrost evaporator
Have you checked refrigerant charge?Refrigerant shortage.Repair leak & recharge.
Where is unit located? What is air temperature entering condenser?Condensing temperature too lowReplace or repair existing condenser control. Add if none exists
Are suction lines insulated properly? i.e. from outside of box to compressor. (Cold weather)Suction lines improperly or not insulatedInsulate suction lines
Do you have the correct expansion valve?Undersized expansion valveReplace with properly sized expansion valve
Is expansion valve in proper adjustment? Is superheat correct?Expansion valve underfeedingAdjust expansion valve until proper superheat is reached
Do you have a pressure drop across filter drier?Clogged filter drierReplace core(s) or entire suction filter
Do you have a pressure drop across suction filter?Clogged suction filterReplace core(s) or entire suction filter
Are suction lines restricted?Restricted suction linesRemove restrictions or replace