VOGT ICE TUBE-ICE P-24A, Service Manual

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P24A & P34A Service Manual
START-UP & OPERATION
12/10/12
5-1
5. Start-Up & Operation
Refrigeration System Review.
The refrigeration system uses anhydrous ammonia (R-717)
refrigerant. Following the piping schematic (Figure 4-1 or 4-2), you will see that during the
machine’s freeze cycle, the compressor discharge gas goes through the oil separator (14) to remove
any oil present in the discharge gas and return the oil to the compressor crankcase. From the oil
separator, the discharge gas continues through a heat coil in the lower part of the condenser/receiver
(15).
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It is then discharged into the condenser and condensed into a liquid by the removal of heat by
water passing through the condenser tubes. A reservoir of liquid R-717 (approximate 375 lbs for
P24A and 625 lbs. for P34A) is accumulated in the receiver and is required for thawing purposes.
Liquid from the receiver flows through the strainer to the “A” solenoid valve (20) which opens and
closes by action of the low side float switch (10). The liquid is then expanded through the hand
expansion valve (17) and into the evaporator (2) (freezer). The cold wet R-717 refrigerant floods the
evaporator and is in contact with the outside of the ice making tubes which water is being circulated
through. The heat contained in the 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
freezer tubes. Since the purest water freezes first, the circulating water continues to wash the
dissolved solids down into the sump area of the water tank. The flushing valve helps to rid the water
tank of increased dissolved solids by flushing them out the overflow during the harvest (thawing)
period.
The wet suction gas leaves the freezer and passes through the suction accumulator (88), where liquid
droplets are removed, allowing dry gas to enter the suction side of the compressor. The suction gas
is then compressed and discharged once again, completing the cycle. As ice continues to form in the
freezer tubes, the suction pressure steadily decreases until the freezer pressure switch is satisfied and
the contact closes, initiating the thaw (harvest) cycle.
Note: Freezing time will vary, depending on make-up water temperature and thickness of ice
produced.
During the harvest period, the “D” thawing gas valve (18) opens and the compressor unloads,
allowing the warm high pressure gas from the receiver to enter the freezer. As the tubes warm up to
slightly above freezing, the ice inside the tubes releases and falls down onto the rotating cutter for
sizing and discharging. Harvesting requires about three minutes, but can vary depending on ice
thickness, suction pressure, and discharge pressure (thawing gas temperature).
! IMPORTANT !
It is a good idea and will be profitable for you to observe and
become familiar with the proper operating characteristics of your
Tube-Ice
   
machine. It will help you to recognize and correct minor
irregularities as they occur in order to help prevent major problems.
“An ounce of prevention is worth a pound of cure.”
! IMPORTANT !
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Note: in the P24A the condenser and receiver are combined. In the P34A the condenser and the receiver are separated. The P34A receiver
contains the heating coil.