Service manual

Section 7 Refrigeration System
Part No. 80-1206-3 7-15
ANALYZING DISCHARGE PRESSURE
DURING FREEZE OR HARVEST CYCLE
Procedure
1. Determine the ice machine operating conditions:
Air temp. entering condenser ______
Air temp. around ice machine ______
Water temp. entering sump trough ______
2. Refer to Cycle Times/24 Hour Ice Production/
Refrigeration Pressure Chart for ice machine being
checked.
Use the operating conditions determined in step 1 to
find the published normal discharge pressures.
Freeze Cycle _______ Harvest Cycle_______
3. Perform an actual discharge pressure check.
4. Compare the actual discharge pressure (step 3) with
the published discharge pressure (step 2).
The discharge pressure is normal when the actual
pressure falls within the published pressure range for the
ice machine’s operating conditions. It is normal for the
discharge pressure to be higher at the beginning of the
freeze cycle (when load is greatest), then drop through
out the freeze cycle.
Freeze Cycle Discharge Pressure High Checklist
Freeze Cycle Discharge Pressure Low Checklist
NOTE: Do not limit your diagnosis to only the items listed in the checklists.
Freeze
Cycle PSIG
Harvest
Cycle PSIG
1 Minute into Cycle __________ __________
Middle of Cycle __________ __________
End of Cycle __________ __________
Possible Cause Check/Correct
Improper installation See “Installation/Visual Inspection Checklist”
Restricted condenser air flow (air-cooled models) High inlet air temperature
Condenser discharge air recirculation
Dirty condenser fins
Defective fan cycling control (CVD675/CVD1476 do not have a fan
cycle control)
Defective fan motor
Improper refrigerant charge Overcharged
Non-condensables in system
Wrong type of refrigerant
Other Non-Manitowoc components in system
High side refrigerant lines/component
Restricted (before mid-condenser)
Defective head pressure control valve
Water inlet valve is incorrectly adjusted (CVD1476 only)
Possible Cause Check/Correct
Improper installation See “Installation/Visual Inspection Checklist”
Improper refrigerant charge Undercharged
Wrong type of refrigerant
Other Non-Manitowoc components in system
High side refrigerant lines/component restricted (before mid-condenser)
Defective head pressure control valve (remote models)
Defective fan cycle control (CVD675/CVD1476 do not have a fan cycle
control)
Water inlet valve is incorrectly adjusted (CVD1476 only)