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PRESSURE CONTROL SPECIFICATIONS
AND DIAGNOSTICS
Headmaster Control Valve
FUNCTION
The headmaster control valve maintains the correct
discharge pressure and liquid line temperature in the
Freeze and Harvest cycles
.
Manitowoc QuietQube
®
systems require headmaster
control valves with special settings. Replace defective
headmaster control valves only with “original”
Manitowoc replacement parts.
FREEZE CYCLE OPERATION
Air-Cooled Models
During low ambient conditions, it is normal for the
head pressure control valve to hunt (head pressure
may fluctuate up and down) on CVD condensing units.
Hunting varies by model and ambient, but generally
settles out within the first 6 minutes of the freeze cycle.
At ambient temperatures of approximately 70°F
(21.1°C) or above, refrigerant flows through the valve
from the condenser to the receiver inlet. At
temperatures below this (or at higher temperatures if it
is raining), the head pressure control starts to
modulate (closes the condenser port and opens the
bypass port from the compressor discharge line).
In this modulating mode, the valve maintains minimum
head pressure by building up liquid in the condenser
and bypassing discharge gas directly to the receiver.
Water-Cooled Models
The water regulating valve setting is higher than the
head pressure control valve set point. All refrigerant is
directed through the condenser and the water
regulating valve maintains the correct head pressure.
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