Vogt TUBE-ICE P-118F, Service Manual

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P118F Service Manual
SERVICE OPERATIONS
1/6/09
9-14
FIGURE 9-7
Loaded Operation (during freeze).
This capacity control valve is controlled by an electric
solenoid. When the solenoid is de-energized, the valve loads the cylinder bank (2 cylinders) as
shown in the above figure.
In the normal (full capacity) operating position with the solenoid valve de-energized, the needle
valve is seated on the lower port, and the unloading plunger chamber is exposed to suction pressure
through the suction port. Since the face of the plunger is open to the suction chamber, the gas
pressures across the plunger are equalized, and the plunger is held in the open position by the spring.
Unloaded Operation (during thaw only). During the thaw cycle, the solenoid coil is energized.
The needle valve is seated on the upper port, and the unloading plunger chamber is exposed to
discharge pressure through the discharge pressure port. The differential between discharge and
suction pressure forces the plunger down, sealing the suction port in the valve plate, thus preventing
the entrance of suction vapor into the unloaded cylinders.