Vogt TUBE-ICE 05TA, Service Manual

Page: 38 / 111

05TA Service Manual
START-UP AND OPERATION
8/13/01
5-1
5. Start-Up and Operation
Refrigeration System Review.
The refrigeration system uses R-22 or R-404a refrigerant, a
compressor, a refrigerant float switch, a flooded evaporator (freezer), and warm gas defrost.
Following the schematic, notice that during the freeze period of the machine’s cycle, the condenser
discharge gas leaves the compressor and goes to the condenser where it is condensed into liquid by
the removal of heat by either air or water passing through the condenser. A reservoir of liquid is
accumulated in the receiver and flows as required, passing through the filter/drier, the thawing
chamber (a lower separate section of the freezer) and the liquid feed solenoid valve (the “A” valve).
The position of the “A” valve during the freeze cycle allows the liquid to be metered by the float
switch. The “A” valve opens and closes in response to the refrigerant level in the freezer. Wet
refrigerant floods the evaporator and is in contact with the outside of the ice-making tubes in which
water is being circulated. The heat contained in this water passes through the wall of the tubes,
lowering the temperature of the water, causing it to freeze and form a long tube of ice that adheres to
the inside of each of the freezer tubes. The flowing water keeps the accumulated ice clear by washing
separated solids down into the sump area of the water tank.
The wet suction gas leaves the freezer and any remaining liquid droplets are removed by the
accumulator and suction line heat exchanger. The dry gas enters the compressor and is compressed
then discharged to the condenser completing the cycle.
As the ice is formed in the freezer, the suction pressure steadily reduces until it causes the freezer
pressure switch to close, initiating the harvest period.
During the harvest period, the thawing gas solenoid valve (the “D” valve) is open allowing the warm
high pressure gas to enter the freezer. This heat melts a thin film from the outside of the ice, reducing
the diameter and letting it fall free from the freezer tubes. This period lasts approximately 2 1/2
minutes.
Refrigerant Charge.
Included with the machine is the required charge (approximately 250 lbs.) of
Refrigerant 22 or 404a, depending on the model, which has been isolated in the receiver (15R).
Before shipment of the machine, the compressor service valves (34), (35), and the stop valves in the
various lines to the condenser and receiver have been closed. These valves are tagged with
instructions that the valves are to be opened prior to start-up of the machine. Before opening these
valves, it is advisable to check all joints for leaks that may have developed during shipment. If no
leaks are present, a positive pressure should show on the suction and discharge pressure gages. They
should indicate a pressure approximately equal to the ambient temperature. This pressure can be
found using the pressure temperature chart for R-22 or R-404a (as applicable), TABLE 10-7.
If it should ever become necessary to add refrigerant to the system, charging valve (28) is provided
for this purpose. Through this valve, refrigerant can be added in liquid form. See “Adding
Refrigerant." The compressor crankcase heater must be energized for a minimum of two hours prior
to starting and running the compressor.