Vollrath STOELTING U421-I2A User manual

Model U421-I2A & U431-I2A
SERVICE MANUAL
Manual No. 513721 Rev.0

This manual provides basic information about the machine. Instructions and suggestions are
given covering its operation and care.
The illustrations and specifications are not binding in detail. We reserve the right to make
changes to the machine without notice, and without incurring any obligation to modify or pro-
vide new parts for machines built prior to date of change.
DO NOT ATTEMPT to operate the machine until instructions and safety precautions in this
manual are read completely and are thoroughly understood. If problems develop or questions
arise in connection with installation, operation, or servicing of the machine, contact Stoelting.
stoeltingfoodservice.com
Stoelting Foodservice Equipment
502 Highway 67
Kiel, WI 53042-1600
U.S.A.
White Glove Service Network
Phone: [phone]
© 2018 Stoelting

Safety Alert Symbol:
This symbol Indicates danger, warning or caution.
Attention is required in order to avoid serious per-
sonal injury. The message that follows the symbol
contains important information about safety.
Signal Word:
Signal words are distinctive words used throughout
this manual that alert the reader to the existence and
relative degree of a hazard.
CAUTION
The signal word “CAUTION” indicates a potentially
hazardous situation, which, if not avoided, may result
in minor or moderate injury and equipment/property
damage.
A Few Words About Safety
Safety Information
Read and understand the entire manual before
operating or maintaining Stoelting equipment.
This manual provides the operator with information
for the safe operation and maintenance of Stoelting
equipment. As with any machine, there are hazards
associated with their operation. For this reason safety
is emphasized throughout the manual. To highlight
specific safety information, the following safety defini-
tions are provided to assist the reader.
The purpose of safety symbols is to attract your at-
tention to possible dangers. The safety symbols, and
their explanations, deserve your careful attention
and understanding. The safety warnings do not by
themselves eliminate any danger. The instructions
or warnings they give are not substitutes for proper
accident prevention measures.
If you need to replace a part, use genuine Stoelting
parts with the correct part number or an equivalent
part. We strongly recommend that you do not use
replacement parts of inferior quality.
WARNING
The signal word “WARNING” indicates a potentially
hazardous situation, which, if not avoided, may result
in death or serious injury and equipment/property
damage.
CAUTION
The signal word “CAUTION” not preceded by the
safety alert symbol indicates a potentially hazardous
situation, which, if not avoided, may result in equip-
ment/property damage.
NOTE (or NOTICE)
The signal word “NOTICE” indicates information or
procedures that relate directly or indirectly to the
safety of personnel or equipment/property.

TABLE OF
CONTENTS
Section Description Page
1 Introduction
1.1 Description.................................................................................................. 1
1.2 Specifications ............................................................................................. 2
1.3 Component Settings ................................................................................... 4
2 Refrigeration System
2.1 Refrigeration System .................................................................................. 5
2.2 Refrigerant Recovery and Evacuation........................................................ 6
2.3 Refrigerant Charging .................................................................................. 6
2.4 Compressor ................................................................................................ 6
2.5 Condenser .................................................................................................. 8
2.6 Valves ......................................................................................................... 8
A. Thermostatic Expansion Valve (TXV) ..................................................................8
B. Check Valve .........................................................................................................9
C. High Pressure Cutout...........................................................................................9
D. Evaporator Pressure Regulator (EPR).................................................................10
E. Water Valve (Water Cooled Models Only)............................................................ 10
2.7 Solenoid (Air Cooled Remote Only) ........................................................... 11
2.8 Filter Drier................................................................................................... 12
3 Electrical and Mechanical Control Systems
3.1 IntelliTec2 Control ....................................................................................... 13
3.2 Contactors .................................................................................................. 13
3.3 Drive Motor ................................................................................................. 13
3.4 Capacitors .................................................................................................. 14
3.5 Gearbox...................................................................................................... 15
3.6 Condenser Fan Motor (Air-Cooled Only).................................................... 15
3.7 Cab Condenser Fan Motor ......................................................................... 16
3.8 Switches ..................................................................................................... 16
A. Spigot Switch .......................................................................................................16
B. Pump Pressure Switch.........................................................................................17
3.9 Temperature Control Sensor ...................................................................... 18
4 Troubleshooting
4.1 Error Codes ................................................................................................ 19
4.2 Troubleshooting .......................................................................................... 19
4.3 Troubleshooting - Machine ......................................................................... 22

Section Description Page
5 Replacement Parts
5.1 Brushes, Decals, and Lubrication............................................................... 23
5.2 Auger Shaft and Door Parts ....................................................................... 24
5.3 Cab Tubing ................................................................................................. 25
5.4 Trays........................................................................................................... 26
5.5 Panels & Screws ........................................................................................ 26
5.6 Cabinet ....................................................................................................... 27
5.7 Cabinet Evaporator..................................................................................... 28
5.8 Pump Parts................................................................................................. 29
5.9 Spigots........................................................................................................ 31
5.10 Electrical ..................................................................................................... 32
5.11 Motor .......................................................................................................... 33
5.12 Cabinet Condensing Unit............................................................................ 34
5.13 Side View.................................................................................................... 35
5.14 Air-Cooled Remote Condensers................................................................. 36
5.15 Kits and Miscellaneous............................................................................... 37
6 Refrigeration Diagram and Wiring Diagrams
6.1 Refrigeration Diagrams............................................................................... 39
6.2 Wiring Diagrams ......................................................................................... 40
A. U421-48I2A..........................................................................................................40
B. U421-409I2A........................................................................................................41
C. U421-109I2A........................................................................................................42
E. U431-48I2A..........................................................................................................43
F. U431-38I2A..........................................................................................................44
G. U431-18I2A..........................................................................................................45
H. U431-409I2A........................................................................................................46
I. U431-309I2A........................................................................................................47
J. U431-109I2A........................................................................................................48

Service Manual #513721 1 U421-I2A & U431-I2A Model Machines
SECTION 1
DESCRIPTION AND SPECIFICATIONS
1.1 DESCRIPTION
The Stoelting U421-I2A and U431-I2A floor model ma-
chines are pressure fed. They are equipped with fully
automatic controls to provide a uniform product.
This manual is designed to assist qualified service per-
sonnel with troubleshooting and repairing the U421-I2A
and the U431-I2A.
NOTE
Thesemachinesare offeredwithtwotypesof spigot
handles,swing gateand pull-down. Theswing gate
styleis opened bymoving the handle to theleft and
must be closed when finished dispensing. The
pull-down style is opened by pulling downwards
and are self-closing.
Figure 1-1 Model U431-I2A
Figure 1-1 Model U421-I2A

Service Manual #513721 2 U421-I2A & U431-I2A Model Machines
1.2 SPECIFICATIONS
Air Cooled
U421-I2A & U431-I2A Air Cooled Remote U421-I2A & U431-I2A Water Cooled U421-I2A & U431-I2A
Dimensions Machine with crate Machine with crate Machine with crate
width 26-3/4’’
(67,9 cm)
34’’
(86,4 cm)
26-3/4’’
(67,9 cm)
34’’
(86,4 cm)
26-3/4’’
(67,9 cm)
34’’
(86,4 cm)
height 68-3/4’’
(174,6 cm)
78’’
(198,1 cm)
67-3/4’’
(172,1 cm)
78’’
(198,1 cm)
67-1/2’’
(171,5 cm)
78’’
(198,1 cm)
depth 39-1/2’’
(100,3 cm)
48’’
(121,9 cm)
39-3/4’’
(101,0 cm)
48’’
(121,9 cm)
39-1/2’’
(100,3 cm)
48’’
(121,9 cm)
Weight 785 lbs
(356,0 kg)
935 lbs
(424,1 kg)
760 lbs
(344,7 kg)
908 lbs
(411,8 kg)
760 lbs
(344,7 kg)
908 lbs
(411,8 kg)
Electrical 1 PH 3 PH 1 PH 3 PH 1 PH 3 PH
circuit ampacity
(per barrel) 32A 20A 36A Left /
31A Right 20A 32A 20A
overcurrent protection
device (per barrel) 50A 30A 50A Left /
45A Right 30A 50A 30A
The machine requires one dedicated electrical circuit per barrel.
Compressor Two - 19,000 Btu/hr
Cabinet - 1,300 Btu/hr Compressor (R-134a)
Drive Motor Two - 2 hp
Cooling Air cooled units require 6”
(15,2 cm) air space on all
sides and open at the top.
Remote air cooled
requires two remote
condensers and two
precharged line sets.
Water cooled units require
1/2” N.P.T. water and
drain fittings. Maximum
water pressure of 130
psi. Minimum water flow
rate of 3 GPM per barrel.
Ideal EWT of 50°-70°F.
The machine requires 6”
(15,2 cm) air space on
all sides for the cabinet
refrigeration system.
Mix Storage Up to six 5-gallon bags
Freezing Cylinder
Volume Two - 1.33 gallon (5,03 liters)

Service Manual #513721 3 U421-I2A & U431-I2A Model Machines
Menu Display U421 I2A & U431 I2A
Basic Enable Control Temp/Temp
CutOut Consist Offset 5
CutIn Consist Offset 55
CutIn Temp 40 °F
CutOut Temperature 12 °F
Cycles In Serve Mode 50
Advanced Standby On Time 10 sec
Standby Off Time 360 sec
Standby Time 120 min
Stir On 10 sec
Stir Off 1200 sec
Sleep 2 CutIn 70 °F
Sleep 2 CutOut 54 °F
Default Off Time 900 sec
Storage Storage Refrigeration Active
Storage CutIn 39 °F
Storage CutOut 36 °F
Storage Offset 2 °F
Storage Off Time 4 min
Storage On Time 360 sec
Storage Max On 10 min
Storage Recovery 1 min
Storage Too Warm 50 °F
Storage Too Warm 2 hr
U421-I2A & U431-I2A
Refrigerant R-404A
Charge A/C - 48 oz W/C - 36 oz
Remote - 224 oz
Suction Pressure 19-21 psig
Discharge Pressure
at 80ºF Ambient
A/C - 235-240 psig
W/C - 225-235 psig
Cabinet
Refrigerant R-134A
Charge 8 oz
EPR Valve 32-34 psig

Service Manual #513721 4 U421-I2A & U431-I2A Model Machines
1.3 COMPONENT SETTINGS
Following are the settings for the components in the
U421-I2A and U431-I2A machines.
A. COMPRESSOR WINDINGS
When testing the compressor windings the resistance
through the windings should be as follows:
B. CAPACITORS
Refer to the following table for the capacitance of all the
capacitors in the machine:
C. PUMP PRESSURE SWITCH
The pump pressure switch, located in the cabinet, main-
tains 21-24 psig in the mix line.
°F Resistance °F Resistance
-22 176950 40 26100
-20 165200 42 24725
-18 154300 44 23400
-16 144200 46 22175
-14 134825 48 21000
-12 126125 50 19900
-10 118050 52 18875
-8 110550 54 17900
-6 103550 56 17000
-4 97075 58 16125
-2 91025 60 15325
0 85400 62 14550
2 80150 64 13825
4 75275 66 13150
6 70725 68 12500
8 66475 70 11875
10 62500 72 11300
12 58800 74 10750
14 55325 76 10250
16 52100 78 9750
18 49075 80 9300
20 46250 82 8850
22 43600 84 8450
24 41125 86 8050
26 38800 88 7675
28 36625 90 7325
30 34575 92 7000
32 32675 94 6675
34 30875 96 6375
36 29175 98 6100
38 27600 100 5825
D. TEMPERATURE CONTROL SENSOR
The following table shows the relationship between the
thermistor resistance and the suction line temperature.
Compressor Electrical S to C R to C
282106 1 PH 60Hz 1.340.94
282107 3 PH 60Hz 1.531.21
282108 3 PH 50Hz 3.811.33
Rating
Capacitor Part MFD VAC
Cab Compressor 230667 80 MFD 220 VAC
Compressor - Run 231047 45 MFD 370 VAC
Compressor - Start 230638 88-106 MFD 330 VAC
Drive Motor - Run 231075 30 MFD 370 VAC
Drive Motor - Start 230622 200 MFD 250 VAC
Fan Motor 230654 5 MFD 400 VAC
Pump Motor 1171960 15 MFD 370 VAC

Service Manual #513721 5 U421-I2A & U431-I2A Model Machines
2.1 REFRIGERATION SYSTEM
The U421-I2A and U431-I2A have three separate refrigeration systems; one for each freezing cylinder and one for
the cabinet.
The freezing cylinder systems are designed for use with R404A refrigerant and the cabinet system is designed for
use with R134A refrigerant. The proper charges are indicated on the information plate.
SECTION 2
REFRIGERATION SYSTEM
Figure 2-1 U421-I2A and U431-I2A Refrigeration Systems
Cabinet Refrigeration System
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Service Manual #513721 6 U421-I2A & U431-I2A Model Machines
2.2 REFRIGERANT RECOVERY AND
EVACUATION
Refer to the following procedures to properly recover and
evacuate the refrigeration system. Do not purge refriger-
ant into the atmosphere.
NOTE
Forqualifiedservice personnelonly.Anybodywork-
ing with refrigerants must be certified as a Techni-
cian TYPE I as required by 40 CFR 82 Subpart F
and hold all State and/or local refrigerant handling
certifications.In addition, allhandling, storage, and
disposalof refrigerants mustbe in accordancewith
EnvironmentalProtectionAgency(EPA) guidelines
and standards and all State and local guidelines
and standards.
A. REFRIGERANT RECOVERY
1. Disconnect the machine from electrical supply
before removing any panels for servicing.
2. Remove all panels.
3. Connect the recovery unit to the suction and
discharge service valves of the compressor.
4. Operate the recovery unit per manufacturer’s
instructions
B. EVACUATING THE REFRIGERATION SYSTEM
1. Close any open ports in the refrigeration system.
2. Connect a vacuum gauge to one of the Schrader
valves next to an evaporator.
3. Connect the evacuation unit to the suction and
discharge service valves of the compressor.
4. Evacuate the system until the gauge reads 300
microns of mercury (300Hg) for 5 continuous
minutes.
5. If the system does not maintain a standing vacuum
test with the vacuum pump off (gauge increases
towards atmosphere), find the leak, fix it, and
evacuate again.
2.3 REFRIGERANT CHARGING
Refer to the following procedures to properly charge
the refrigeration system. Stoelting recommends liquid
refrigerant charging.
NOTE
Forqualifiedservice personnelonly.Anybodywork-
ing with refrigerants must be certified as a Techni-
cian TYPE I as required by 40 CFR 82 Subpart F
and hold all State and/or local refrigerant handling
certifications.In addition, allhandling, storage, and
disposalof refrigerants mustbe in accordancewith
EnvironmentalProtectionAgency(EPA) guidelines
and standards and all State and local guidelines
and standards.
A. Ensure the electrical supply has been removed
before continuing.
B. If the system has been opened or if there was a
leak, refer to Section 2.2 - Refrigerant Recovery
and Evacuation to evacuate the system prior to
charging.
C. Refer to machine’s information plate for total
charge requirements.
NOTE
The refrigeration system of the O231 is critically
charged.Besure tocharge thesystemto theweight
listed on the machine’s information plate.
D. For liquid refrigerant charging, connect refrigerant
cylinder to the discharge Schrader valve of the
compressor.
E. Add the proper amount of refrigerant according
to the machine’s information plate.
2.4 COMPRESSOR
The U421-I2Aand U431-I2Ahave two scroll compressors
for the freezing cylinders and one hermetic reciprocating
compressor for the cabinet.(Refer to Figure 2-2 and 2-3).
A. WINDING TEST
To test the motor windings for possible problems, perform
the following steps:
A. Disconnect the machine from electrical supply
before removing any panels for servicing.
B. Remove the panels to gain access to the
compressor terminals.
C. Pull the compressor connector plug off of the
compressor.
WARNING
Hazardous voltage
Make sure the machine is off when disassembling
for servicing. The machine must be disconnected
from electrical supply before removing any access
panel. Failure to disconnect power before servicing
could result in death or serious injury.

Service Manual #513721 7 U421-I2A & U431-I2A Model Machines
D. Test windings with an ohmmeter and refer to the
following table:
Cabinet compressor resistances are as follows:
S to C: 16.4
R to C: 10.2
F. To check if windings are shorted to ground, connect
one ohmmeter lead to a bare metal part on the
compressor (such as any copper line leading to
or from the compressor) and check terminals C,
R, and S.
B. COMPRESSOR REMOVAL
A. Disconnect the machine from electrical supply
before removing any panels for servicing.
B. Remove the back and side panels.
C. Disconnect the electricalplug fromthe compressor.
D. Recover refrigerant charge per the instructions
in Section 2.2.
E. Leave the suction and discharge ports open to
prevent pressure buildup during compressor
removal.
F. Remove six inches of insulating tubing on
the suction line going to the compressor and
unsweat the suction and discharge line from the
compressor.
G. Cap or plug the refrigeration system if the
compressor will not be replaced immediately
(within 10 minutes) to prevent contamination.
H. Remove the four nuts and washers from the base
of the compressor.
I. Remove the compressor from the machine.
J. Remove the four rubber compressor mounts from
the compressor.
K. Crimp and braze all open ports of the old
compressor.
NOTE
A compressor returned to Stoelting with any open
ports void the warranty. ALWAYS crimp and braze
ports on a compressor that has been removed.
C. COMPRESSOR INSTALLATION
A. Make sure the machine is disconnected from the
electrical supply before servicing.
B. Install the four rubber mounts on the compressor.
C. Install the compressor into the machine, fitting
the base over the four bolt holes.
D. Install the four washers and nuts onto the bolts
and tighten securely.
E. Remove all tubing plugs from the replacement
compressor.
NOTE
Thecompressor plugsprotect thecompressor from
moisture in the air. Do not remove the plugs until
you are ready to install. The compressor must not
be opened to the atmosphere for more than 10
minutes.
F. Leave the suction and discharge ports open to
prevent pressure buildup. Braze the suction and
discharge line to the compressor.
G. Connect the electrical plug to the compressor.
H. Replace the drier per the instructions in Section
2.8.
I. Evacuate the system per the instructions in Section
2.2
J. Recharge the system per the instructions in
Section 2.3.
K. Replace the insulating tubing on the suction line.
Compressor Electrical S to C R to C
282106 1 PH 60Hz 1.340.94
282107 3 PH 60Hz 1.531.21
282108 3 PH 50Hz 3.811.33
Figure 2-2 Freezing Cylinder Compressor
Figure 2-3 Cabinet Compressor

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
fin type. The machine must have a minimum of 6” of clear-
ance on all sides for proper air flow.
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 airflow. 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

Service Manual #513721 9 U421-I2A & U431-I2A Model Machines
TXV REPLACEMENT
To replace the TXV, perform the following procedures:
A. Position the TXV with a heat sink into the system.
B. With the suction and discharge ports open, braze
the TXV into the system using appropriate brazing
material.
C. Remove the heat sink from the TXV.
D. Install bulb on suction line exiting the evaporator
using existing clamp. The bulb has an indent
which must be placed against the tubing.
NOTE
Goodcontact betweenthe bulb andthe suctionline
is necessary for proper operation of the valve. The
bulb must also be well insulated.
E. Tighten clamp to 20 in/lb using a torque wrench.
F. Replace insulation to the TXV and surrounding
lines.
G. Replace the drier per the instructions in Section
2.8.
H. Evacuate the system per the instructions in Section
2.2.
I. Recharge the system per the instructions in
Section 2.3.
B. CHECK VALVE
The machine has 2 magnetic check valves (Refer to
Figure 2-6). Each valve is positioned in the suction line
and prevents backflow of refrigerant into the evapora-
tor. If there is reversed flow, the product in the freezing
cylinder softens and liquid refrigerant can flood into the
compressor on startup.
If a check valve needs to be replaced, use a heat sink (wet
cloth) when installing the new valve to prevent damage.
C. HIGH PRESSURE CUTOUT
There is a high pressure cutout for each freezing cylinder
(Fig 2-7) and one for the cabinet refrigeration (Fig 2-8).
The high pressure cutout stops the compressor if the
discharge pressure reaches the cutout, 445 psig for the
freezing cylinders and 405 psig for the cabinet.
The high pressure cutout for the freezing cylinders auto-
matically reset. The cutout for the cabinet refrigeration is
a manual reset located behind the back panel.
HIGH PRESSURE CUTOUT TEST
A. Connect a gauge to the Schrader valve on the
discharge line.
B. Disconnect cooling:
In a water-cooled machine, shut off the water
supply.
In an air-cooled machine, shut off the fan motor
in the IntelliTec2 control. Refer to Section 4.6 for
details.
For the cabinet fan, disconnect the fan motor.
Figure 2-6 Check Valve
Figure 2-7 High Pressure Cutout
Freezing Cylinders
Figure 2-8 High Pressure Cutout
Cabinet Refrigeration

Service Manual #513721 10 U421-I2A & U431-I2A Model Machines
C. High pressure cutout should trip when pressure
reaches 445 psig ±9 in the freezing cylinder
system and 405 psig in the cabinet system.
HIGH PRESSURE CUTOUT REMOVAL
A. Remove the side panel.
B. Recover refrigerant charge per instructions in
Section 2.2.
C. Leave the suction and discharge ports open to
prevent pressure buildup during removal.
D. Unsweat capillary tube from suction line.
E. Cap or plug the refrigeration system if the high
pressure cutout will not be replaced immediately
(within 10 minutes) to prevent contamination.
F. Disconnect terminals from high pressure cutout.
HIGH PRESSURE CUTOUT REPLACEMENT
A. With the suction and discharge ports open, braze
the capillary tube to the discharge line.
C. Replace the drier per the instructions in Section
2.8.
D. Braze bulb into place on suction line.
E. Evacuate the system per the instructions in Section
2.2.
F. Recharge the system per the instructions in
Section 2.3.
G. Connect the terminals to the high pressure cutout.
H. Attach the high pressure cutout using the two
screws with star washers.
D. EVAPORATOR PRESSURE REGULATOR (EPR)
There is one EPR in the refrigeration system (Refer to
Figure 2-9). It is located on the suction line of the cabinet
evaporators and regulates evaporator refrigerant pressure.
EPR TEST AND ADJUSTMENT
Adjustment to the EPR must be made when the cabinet
refrigeration is running
A. Disconnect the machine from electrical supply
before removing any panels for servicing.
B. Remove the rear panel.
C. Connect a gauge to the Schrader valve on the
suction line between the cabinet evaporator and
the EPR.
D. Connect power to the machine.
E. Turn the machine on by pressing the Main Power
Off/On button. Listen for the cabinet compressor
to start.
F. The gauge should read 32-34 psig. If it does not,
then adjustment is needed.
G. Remove the plastic cap and loosen the locknut
on the EPR. Using a small screwdriver, turn the
adjustment screw counterclockwise 1/2 turn, then
adjust as necessary. Turn the valve stem clockwise
for higher pressure or counterclockwise for lower
pressure.
H. Allow the system to stabilize for 5 minutes to
ensure pressure remains stable.
EPR REMOVAL
A. Remove the rear panel.
B. Recover refrigerant charge per instructions in
Section 2.2.
C. Leave the suction and discharge ports open to
prevent pressure buildup during EPR removal.
D. Unsweat the EPR and remove.
E. Cap or plug the refrigeration system if the EPR will
not be replaced immediately (within 10 minutes)
to prevent contamination.
EPR REPLACEMENT
To replace the EPR, perform the following procedures:
A. Apply a heat sink (wet cloth) to the EPR.
B. With an open port, braze the EPR into the system.
C. Remove the heat sink from the hot gas bypass.
D. Replace the filter drier. Refer to Section 2.8 for
details.
E. Evacuate and recharge system per instructions
in Section 2.2.
E. WATER VALVE (WATER COOLED MODELS ONLY)
The water valve monitors refrigerant pressure and opens
on an increase of pressure. The opening point pressure
is the refrigerant pressure required to lift the valve disc
off the valve seat. (Figure 2-10)
Figure 2-9 EPR Valve
Figure 2-10 Water Valve

Service Manual #513721 11 U421-I2A & U431-I2A Model Machines
WATER VALVE ADJUSTMENT
A. Remove the lower front panel and side panel.
B. Connect a gauge to the compressor discharge
Schrader valve.
C. Connect the machine to the electrical supply, start
the refrigeration cycle, and read the pressure.
D. The proper gauge reading should be 225-235 psig.
The exit water temperature should be 95-107°F.
E. If the water temperature and high side pressure
are too low, the opening point pressure should
be increased to slow the water flow. Turn the
adjustment screw counterclockwise.
F. If the water temperature and high side pressure
are too high, the opening point pressure should
be decreased to increase the flow of water. Turn
the adjustment screw clockwise.
WATER VALVE REMOVAL
The water valve is connected to the refrigeration system
by capillary tube brazed to the discharge line.
A. Turn off and disconnect the water supply. Blow
out the water lines with compressed air or CO2.
B. Recover refrigerant charge per instructions in
Section 2.2.
C. Leave the suction and discharge ports open
to prevent pressure buildup during water valve
removal.
D. Unsweat the capillary tube from the discharge
line.
E. Cap or plug the refrigeration system if the water
valve will not be replaced immediately (within 10
minutes) to prevent contamination.
F. Remove the clamps from the water lines at the
valve.
G. Remove the two screws holding the water valve
to the frame and remove the valve.
WATER VALVE REPLACEMENT
To replace the water valve, perform the following proce-
dures:
A. Position the water valve and attach to the frame
using the two screws.
B. Install the water lines onto the valve with hose
clamps.
C. Leave the suction and discharge ports open
to prevent pressure buildup during water valve
installation.
D. Braze the capillary tube into the system.
E. Connect the water supply line and turn on the
water supply.
F. Check for leaks in the water lines. If there are no
leaks, turn off the water supply.
G. Replace the filter drier. Refer to Section 2.8 for
details.
H. Evacuate and recharge system per instructions
in Section 2.2.
I. Turn on the water and check for leaks in the water
lines with the refrigeration system running.
J. Adjust the valve as necessary.
2.7 SOLENOID (AIR COOLED REMOTE ONLY)
Solenoid valves are installed on the freezing cylinder liquid
lines in air cooled remote machines. A solenoid valve has
a magnetic coil that, when energized, lifts a plunger and
allows refrigerant to flow. The solenoids are activated by
the IntelliTec2 control and determine which evaporator
receives refrigeration.
ACTIVATING A SOLENOID
To activate a solenoid, follow these steps:
A. From the Current Status screen, press the right
arrow, SET, then the SEL button to access the
technician level on the control.
B. Navigate to the Left Output Control or Right Output
Control menu which is located under Utilities in
the Testing and Manual Operation screen. Refer
to Section 4 for details.
C. Activate the solenoid by moving the cursor to
the Liquid Solenoid option and pressing the SET
button.
NOTE
Any energized component will deenergize after
leaving the Testing and Manual Operations menu.
SOLENOID TESTING
The following test will check if a liquid line solenoid has
a leaking valve seat. The power to the solenoid is dis-
connected and refrigerant flow is monitored through the
system. If the valve seat does not leak, the suction pres-
sure during the test will be low.
A. Attach a gauge to the Schrader valve on the
suction line.
B. From the Current Status screen, press the right
arrow, SET, then the SEL button to access the
technician level on the control.
Figure 2-11 Solenoid Valve

Service Manual #513721 12 U421-I2A & U431-I2A Model Machines
C. Navigate to the Left Output Control or Right Output
Control menu which is located under Utilities in
the Testing and Manual Operation screen. Refer
to Section 4 for details.
D. Activate the compressor by moving the cursor
to the compressor option and pressing the SET
button.
E. The gauge should read well below 21 psig after
1 minute.
F. A leaking valve seat may also show frost on the
liquid line tubing just past the solenoid and before
the evaporator.
SOLENOID MAGNETIC COIL REMOVAL
A. Remove the side panel.
B. Disconnect the electrical wires.
C. Remove the retainer screw from the top of the
solenoid and pull the magnetic coil off.
SOLENOID MAGNETIC COIL INSTALLATION
To replace the magnetic coil, perform the following pro-
cedures:
A. Push the coil on to the solenoid valve stem.
B. Connect the two electrical wires to the magnetic
coil.
C. Make sure there isn’t any foam insulation between
the valve coil and valve body. Trim any excess
insulation.
D. Install retainer screw onto top of coil.
SOLENOID VALVE REMOVAL
A. Identify and disconnect the two wires from the
solenoid coil.
B. Remove the retainer holding the coil to the solenoid
body and remove the coil.
C. Recover refrigerant charge per instructions in
Section 2.2.
D. Remove insulation around valve and attached
refrigeration lines.
E. Apply heat sinks (wet cloth) to the insulated
refrigerant lines near the valve.
F. Leave a port open to prevent pressure buildup
during solenoid removal
G. Unsweat the solenoid and remove.
H. Cap or plug the refrigeration system if the solenoid
valve will not be replaced immediately (within 10
minutes) to prevent contamination.
SOLENOID VALVE REPLACEMENT
To replace the solenoid, perform the following procedures:
A. Position the new solenoid with the arrow pointing
toward the direction of refrigerant flow.
B. Apply a heat sink (wet cloth) to the solenoid valve.
C. With the suction and discharge ports open, braze
the solenoid into the system.
D. Remove the heat sink from the valve.
E. Replace insulation around valve.
F. Replace the filter drier. Refer to Section 2.8 for
details.
G. Evacuate and recharge system per instructions
in Section 2.2.
2.8 FILTER DRIER
The filter drier must be replaced every time the refrigeration
system is opened for service. A new filter drier improves
operation of the entire refrigeration system by stopping
the circulation of moisture and by removing harmful con-
taminants (Refer to Figure 2-11).
FILTER DRIER REMOVAL
A. Recover refrigerant charge per instructions in
Section 2.2.
B. Cut the refrigeration line as close to the filter drier
as possible and remove drier.
C. Cap or plug the refrigeration system if the drier will
not be replaced immediately (within 10 minutes)
to prevent contamination.
D. Cap the ends of the drier using the plugs from
the new drier.
NOTE
The drier must be capped to prevent moisture from
the environment
FILTER DRIER REPLACEMENT
A. Position the filter drier so the arrow is pointing
toward the direction of refrigerant flow (pointing
away from the condenser).
B. Apply a heat sink (wet cloth) to the filter drier.
C. With the suction and discharge ports open, braze
the filter drier into the system.
D. Evacuate the system per instructions in Section
2.2.
E. Recharge the system per instructions in Section
2.3.
Figure 2-12 Filter Drier

Service Manual #513721 13 U421-I2A & U431-I2A Model Machines
SECTION 3
ELECTRICAL AND MECHANICAL CONTROL SYSTEMS
NOTE
The wiring diagram is available in Section 5.
3.1 INTELLITEC2 CONTROL
The IntelliTec2 control consists of three main components;
a control board, a display board and a membrane switch
(touchpad).
The control board is modular and consists of a program
board and a relay board. Refer to the IntelliTec2 manual
for details.
3.2 CONTACTORS
The U421-I2A and U431-I2A have a total of six contac-
tors. Each side of the machine has a contactor for the
compressor, drive motor and IntelliTec2 control. The
contactor for the IntelliTec2 provides power to the fan
motor (in air-cooled machines) and the condensing unit
for the cabinet.
The compressor and drive motor contactors are mounted
to their respective evaporator and the IntelliTec2 contac-
tors are located in the header panel.
The IntelliTec2 control sends electronic signals to trigger
the contactors. Separate signals are used to control each
drive motor contactor and each compressor contactor.
The signals to the contactors are staggered, so the drive
motor always starts three seconds before the compres-
sor. By staggering the starting and stopping of the drive
motor, maximum starting torque is available and voltage
spikes are reduced.
A. CONTACTOR TESTS
The following tests help determine if a contactor is work-
ing properly.
1. Listen for the contactor to close. When the
spigot is opened or the Push To Freeze button is
pressed, the drive motor contactor closes. After
three seconds, the compressor contactor closes.
2. Check to ensure contactor is receiving signal.
Read voltage across the coils of the contactor
during a freezing cycle. Voltage should be about
230V. If there is no voltage reading, refer to Section
4 Troubleshooting.
3.3 DRIVE MOTOR
The U421-I2Aand U431-I2A have two drive motors which
rotate the auger assemblies. Internal, normally closed,
centrifugal switches start the drive motors. The motors
have an internal thermal overload.
A. DRIVE MOTOR TEST
1. Turn the machine off by pressing the Main Power
Off/On button and disconnect the machine from
the electrical supply.
2. Remove the back panel and a side panel.
3. Loosen the belttension adjustmentnut andremove
the belt (Refer to Figure 3-1).
4. Connect power to the machine.
5. Turn the machine on by pressing the Main Power
Off/On button.
6. Press the right arrow, SET, then the SEL button
to access the technician level on the control.
7. Activate the drive motor through the Left Output
Control or Right Output Control menus which are
located under Utilities in the Testing and Manual
Operation screen. Refer to the IntelliTec2 manual
for details.
WARNING
Hazardous voltage
Make sure the machine is off when disassembling
for servicing. The machine must be disconnected
from electrical supply before removing any access
panel. Failure to disconnect power before servicing
could result in death or serious injury.
Figure 3-1 Belt Tension Nut
Loosen belt tension
adjustment nut.
Loosen belt tension
adjustment nut.

Service Manual #513721 14 U421-I2A & U431-I2A Model Machines
6. Remove the motor mounting nuts and remove
the motor.
7. Loosen the two allen head screws from the pulley.
8. Remove the pulley and key from the motor shaft.
C. DRIVE MOTOR INSTALLATION
1. Place the motor onto the mounting bolts and
install the mounting nuts.
2. Place the pulley and key on the motor shaft.
NOTE
Do not tighten the pulley screws until after the belt
tension has been properly adjusted.
3. Install the tensioning assembly.
4. Install the belt and tighten the tension adjustment
nut.
5. Use a Burroughs Belt Tension Gauge to set the
tension for the drive belt. Set the belt tension to
55-60 lbs.
6. Using a straightedge, align the drive motor pulley
with the gearbox pulley. Tighten the two allen
head screws.
7. Install wiring according to wiring diagram (located
behind the left side panel). Install electrical cover
plate on the motor.
8. Install back and side panels.
3.4 CAPACITORS
The compressor start and run capacitors are only on
single phase machines. They are in the electrical box
behind the back panel.
The start and run capacitors for the drive motors are
mounted directly onto each motor body.
A. CAPACITOR TEST
1. Disconnect machine from electrical supply before
removing any panels for servicing.
2. Remove a lead from one of the capacitor terminals.
3. Using insulated pliers, discharge the capacitor
by connecting a 20K5W resistor across the
terminals.
NOTE
Discharge the capacitor even if there is a bleeder
resistoracrossthe terminals.Theremay beanopen
in the bleeder resistor preventing it from working
properly.
8. Go to the Test Monitoring screen under Utilities.
The motor current should be as follows:
Single Phase Machines: 6.1-6.3 Amps
Three Phase Machines: 4.0-4.2 Amps
NOTE
The motor amps are based on 230VAC supply
voltage.
9. After the test, stop the motor by exiting the Testing
and Manual Operation section. Turn the machine
off and disconnect from the electrical supply.
10. Install the belt and tighten the tension nut.
11. Use a Burroughs Belt Tension Gauge to set the
tension for the drive belt. Set the belt tension to
55-60 lbs.
12. Using a straightedge, align the drive motor pulley
with the speed reducer pulley. Align the pulley if
necessary.
B. DRIVE MOTOR REMOVAL
1. Disconnect machine from electrical supply before
removing any panels for servicing.
2. Remove the back panel and the side panel.
3. Remove the electrical cover plate from the back
of the motor.
4. Identify (mark) wires and remove them from the
motor.
5. Remove the tensioning nut and tensioning
assembly. Then remove the belts. (Refer to Figure
3-2)
Figure 3-2 Motor Mounting Assembly
Remove motor
mounting nuts.
Remove tensioning
assembly.
Remove motor
mounting nuts.
Remove tensioning
assembly.