Vollrath STOELTING U421-I2A, Service Manual, Page: 14 / 54

Service Manual #513721 8 U421-I2A & U431-I2A Model Machines
2.5 CONDENSER
The U421-I2A and U431-I2A are available with either an
air-cooled, water-cooled, or air cooled remote condenser.
The capacity of the machine is directly related to keeping
the condenser clean and free of debris.
The air-cooled condenser is a copper tube and aluminum
fi n type. The machine must have a minimum of 6” of clear-
ance on all sides for proper air fl ow.
The water-cooled condenser is a tube and shell type. This
condenser requires cool, clean water to function properly.
Inlet and discharge lines must be 1/2” ID minimum.
The remote air cooled condenser must have enough clear-
ance for proper air
fl ow. Refer to the remote condenser
documentation for details.
CONDENSER TESTING
The condenser can be checked for leaks using the bubble
test or using a leak detector.
2.6 VALVES
A. THERMOSTATIC EXPANSION VALVE (TXV)
The Thermostatic Expansion Valve (TXV) is used to meter
the refrigerant to the freezing cylinder evaporator. It does
so by maintaining a constant pressure in the evaporator.
The self-regulating TXV is preset by the manufacturer and
adjustment is not recommended. Figure 2-4.
TXV TESTING & ADJUSTMENT
NOTE
The bulb has an indent which must be positioned
against the tubing. Good contact between the
bulb and the suction line is necessary for proper
operation of the valve. The bulb must also be well
insulated.
A. Connect a gauge to the Schrader valve on the
suction line.
B. Connect a thermocouple to the suction line next
to the evaporator.
C. Immediately before the refrigeration cycle ends,
the gauge should read between 19-21 psig. The
superheat should be 7-10°F.
D. If the pressure reading is higher than expected
and the superheat is low, check to see if there is
an overcharge of refrigerant.
E. If the pressure reading is lower than expected and
the superheat is high, check to see if there is a
low refrigerant charge or if there is a restriction
in the system.
NOTE
The TXV is the LAST component to adjust in the
refrigeration system.
F. The TXV can be adjusted after the steps above are
completed. When adjusting, do not turn the valve
over 1/4 turn (90°). Turn the valve stem clockwise
to increase the superheat or counterclockwise to
decrease the superheat.
TXV REMOVAL
A. Remove the side panel.
B. Remove bulb from suction line exiting from the
evaporator.
C. Recover refrigerant charge per instructions in
Section 2.2.
D. Leave the suction and discharge ports open to
prevent pressure buildup during TXV removal.
E. Remove any insulation from the TXV and
immediate surrounding lines.
F. Apply a heat sink (wet cloth) to the valve dome
(Figure 2-5).
G. Unsweat the TXV and remove.
H. Cap or plug the refrigeration system if the TXV will
not be replaced immediately (within 10 minutes)
to prevent contamination.
Figure 2-4 TXV
Figure 2-5 TXV Removal