Section 7 Refrigeration System7-19ANALYZING DISCHARGE PRESSUREDURING FREEZE OR HARVEST CYCLEProcedure1. Determine the ice machine operating conditions:Air temp. entering condenser ______Air temp. around ice machine ______Water temp. entering float valve ______2. Refer to Operating Pressure Chart for ice machinebeing checked. (These charts begin on page 7-31.)Use the operating conditions determined in Step 1to find the published normal discharge pressures.Freeze Cycle ______ Harvest Cycle ______3. Perform an actual discharge pressure check.Freeze CyclePSIGHarvest CyclePSIGBeginning of Cycle __________ __________Middle of Cycle __________ __________End of Cycle __________ __________4. Compare the actual discharge pressure (Step 3)with the published discharge pressure (Step 2).The discharge pressure is normal when the actualpressure falls within the published pressure rangefor the ice machine’s operating conditions.Freeze Cycle Discharge Pressure High ChecklistPossible Cause Check/CorrectImproper installation • See “Installation/Visual Inspection Checklist” on page 7-10Restricted condenserair flow (air-cooled models)• High inlet air temperature (110°F/43.3°C max.)• Condenser discharge air recirculation• Dirty condenser filter• Dirty condenser fins• Defective fan cycling control• Defective fan motorRestricted condenser waterflow (water-cooled models)• Low water pressure (20 psi min.)• High inlet water temperature (90°F/32.2°C max.)• Dirty condenser• Dirty/defective water regulating valve• Water regulating valve out of adjustmentImproper refrigerant charge • Overcharged• Non-condensibles in system• Wrong type of refrigerantOther • Non-Manitowoc components in system• High side refrigerant lines/component restricted (before mid-condenser)• Defective head pressure control valve (remote models)Freeze Cycle Discharge Pressure Low ChecklistPossible Cause Check/CorrectImproper installation • See “Installation/Visual Inspection Checklist” on page 7-10Improper refrigerant charge • Undercharged• Wrong type of refrigerantWater regulating valve(water-cooled condensers)• Out of adjustment• DefectiveOther • Non-Manitowoc components in system• Defective head pressure control valve (remote models)• Defective fan cycle controlNOTE: Do not limit your diagnosis to only the items listed in the checklists.
