Vogt TUBE-ICE P-118F, Service Manual

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P118F Service Manual
SERVICE OPERATIONS
1/6/09
9-13
Whenever there is a compressor failure due to a motor burnout, it is important that they system be
thoroughly cleaned before replacing the damaged compressor or otherwise the new compressor may
also be damaged.
Solenoid Valves.
All solenoid valves are pilot operated with “floating” type diaphragms. For
satisfactory operation be sure that the manual opening stem is in the closed or automatic position.
This means the stem is backed all the way out. Correct direction of stem rotation should be labeled
on the stem seal nut.
FIGURE 9-6
“D” Solenoid Valve
Circulating Water Pump Motor . The motor bearings are prelubricated and sealed. They require
no further lubrication. The pump should operate with the water level above the impeller housing.
The pump is equipped with a mechanical seal which is self-adjusting and requires no lubrication.
However, the pump should not be operated unless circulating water. The pump manufacturer
recommends that a mechanical seal be kept as a spare. When ordering a seal, specify pump size,
type, serial number, and manufacturer’s name as indicated on the nameplate.
Capacity Control (Internal) Valve Construction. A schematic illustration of the internal valve
operation is shown in Figure 9-7.
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.
When the solenoid valve 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.
The seal on the unloading plunger minimizes any leakage in pressure so that a pumpdown cycle may
be used with the valve either energized or de-energized without excessive compressor cycling.