Vogt Tube-Ice HFO10, Service Manual

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2-7
To prevent refreezing, make sure all ice clears the freezer with at least 30 seconds to spare
before the next freezing period begins.
Refrigeration System Overview
The refrigeration system uses hydrofluoroolefin (HFO) blend refrigerant R513A.
It contains:
•
Bitzer semi-hermetic compact screw compressor (CSH) with integral oil separator
•
Refrigerant float switch
•
Expansion valve
•
Flooded evaporator (freezer)
•
Hot gas defrost
As shown in the piping schematic, the compressor discharge gas leaves the compressor and goes into the
condenser. Here, the gas is condensed into liquid as heat is removed from the water as it passes through the
condenser during the freezing period.
A reservoir of liquid is accumulated in the receiver and flows as required, passing through the thawing chamber
(located in the lower section of the freezer) then through the filter/dryer. The liquid line solenoid valve (A)
opens and closes in response to the liquid level in the freezer, as determined by the refrigerant float switch
mounted on the side of the freezer.
Liquid refrigerant floods the evaporator and comes in contact with the outside of the ice-making tubes through
which water is being circulated. The heat contained in this water passes through the walls of the tubes, lowering
the temperature of the water, causing it to freeze and to form a long tube of ice that adheres to the inside of
each freezer tube. Since the purest water freezes first, the flowing water keeps the accumulated ice clear by
washing separated solids down into the sump area of the water tank. The blowdown valve on the circulating
water pump discharge helps to rid the water tank of increased dissolved solids found in harder water by flushing
them out of the overflow during water pump operation.
During the harvest period, the water pump stops, therefore, all the water circulating in the freezer drops to the
tank, the tank level increases, and the overflow will get rid of that extra water. The overflow is a hole at the top
of the tank. Refer to Chapter 9 for more information about automatic blowdown.
The transfer of heat from the water to the liquid refrigerant causes it to boil and convert into a liquid-vapor
mixture at the suction connection at the top of the freezer. This liquid-vapor mixture passes through the suction
accumulator, where liquid droplets are removed and boiled off from the internal heating coil. The suction line
heat exchanger boils off any residual droplets that may have passed through the suction accumulator, providing
ample protection for the screw compressor.
As the ice forms in the freezer tubes, the suction pressure steadily decreases until it causes the freezer pressure
switch (FPS) to close, initiating the harvest period.
During the harvest period, the thaw gas solenoid valve (D) is open, allowing warm high-pressure gas from the
receiver to enter the freezer. This heat melts a thin film from the outside of the ice, reducing the outside
diameter slightly, allowing it to fall free from the freezer tubes. This period lasts approximately 2-1/2 minutes.
Note: Freezing times will vary, depending on makeup water temperature and setting of the freezer pressure
switch. As you become more familiar with the operation of your machine, you will be able to recognize and
correct minor irregularities as they occur, which will help prevent major problems.