Manitowoc QuietQube SD0672C Technician's Handbook page 209

Diagnosing Air-Cooled Condensing Units
FREEZE CYCLE
1. Determine the air temperature entering the
remote condenser.
2. Determine if the head pressure is high or low in
relationship to the outside temperature. (Refer to
the proper "Operational Pressure Charts
page 239.") 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 list for
diagnosis.
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.
Condition
Discharge Pressure - High
Liquid Line Temperature -
Discharge Pressure - Low
Liquid Line Temperature -
Cold
Discharge Pressure - Low
Liquid Line Temperature -
Part Number 80-1505-3 6/11
Hot
Hot
Probable
Cause
Valve stuck in
bypass
Valve not
bypassing
Ice Machine
Low on
Charge
Corrective
Measure
Replace
valve
Replace
valve
Low on
Charge
Verification
209