Service manual

Refrigeration System Section 7
7-24
Part No. 80-1206-3
Diagnosing Air Cooled Condensing Units
FREEZE CYCLE
1. Determine the air temperature entering the
condenser.
2. Determine if the head pressure is high or low in
relationship to the outside temperature. (Refer to the
proper “Operational Pressure Chart”) If the air
temperature is below 70°F (21.1°C), the head
pressure control will modulate to maintain the
correct liquid line temperature and head pressure.
3. Determine the temperature of the liquid line entering
the receiver by feeling it. This line is normally warm;
“body temperature.”
4. Using the information gathered, refer to the chart
below.
NOTE: A headmaster that will not bypass, will function
properly with condenser air temperatures of
approximately 70°F (21.1°C) or above. When the
temperature drops below 70°F (21.1°C), the headmaster
fails to bypass and the ice machine malfunctions.
Rinsing the condenser with cool water during the freeze
cycle will simulate lower ambient conditions.
Freeze Cycle Headmaster Control Valve Failure List
CVD0875/CVD1075/CVD1285/CVD1475/CVD1875/CVD2075
Freeze Cycle Headmaster Control Valve Failure List
CVD0675
Symptom Probable Cause Corrective Measure
Valve not maintaining pressures Non-approved valve Install a Manitowoc Headmaster control
valve with proper setting
Discharge pressure extremely high;
Liquid line entering receiver feels hot
Valve stuck in bypass Replace valve
Fan cycling control cycles condenser fan
motor, Liquid line entering receiver
fluctuates between warm and cold.
Valve not bypassing Replace valve
Discharge pressure low; Liquid line
entering receiver feels warm to hot
Ice machine low on charge Refer to “Low on Charge Verification”
Fan cycling control cycles condenser fan
motor, liquid line entering receiver feels
warm to hot
Ice machine low on charge Refer to “Low on Charge Verification”
Symptom Probable Cause Corrective Measure
Valve not maintaining pressures Non-approved valve Install a Manitowoc Headmaster control
valve with proper setting
Discharge pressure extremely high;
Liquid line entering receiver feels hot
Valve stuck in bypass Replace valve
Discharge pressure low; Liquid line
entering receiver feels extremely cold
Valve not bypassing Replace valve
Discharge pressure low; Liquid line
entering receiver feels warm to hot
Ice machine low on charge See “Low on Charge Verification”