Page 1
PLUS-TWELVETM
PRESSURELESS STEAM COOKER
Warning
Improper Installation, adjustment,
alteration, service, or maintenance can
cause property damage, injury, or death.
Read the installation, operating, and
maintenance instructions thoroughly
before installing or servicing this
equipment.
For Your Safety
Do not store or use gasoline or other
flammable vapors or liquids in the vicinity
of this or any other appliance.
MODEL: m ST-12 COVERING:
m Installation
m Operation
m Service & Parts
INSTALLATION, OPERATION & MAINTENANCE MANUAL
35 Garvey Street l Everett l MA l 02149
Tel: (617) 387-4100
E-Mail: custserv@mfii.com
Form Number: S-4475 Rev: A 06/03 Printed in U.S.A.
l Fax: (617) 387-4456 l Fax: (Outside MA) 1-800-227-2659
l Website: http://www.mfii.com
Page 2
Page 3
TABLE OF CONTENTS
PARAGRAPH
SECTION 1 INTRODUCTION
1.1Description ............................................
1.2Basic Functioning .................................
1.3Service ..................................................
SECTION 2 INSTALLATION
2.1Assembly ..............................................
2.2Setting in Place .....................................
2.3Mechanical Connections ......................
2.4W ater Connections ...............................
2.5Installation Check-Out ..........................
2.5.1Initial Control Settings ...........................
2.5.2Cooker Check-Out ................................
2.5.3Shut-Down Procedure ..........................
2.6Reversing the Doors .............................
SECTION 3 OPERATION
3.1Operating Controls & Indicators ...........
3.2Operating Procedures ..........................
3.2.1Steam Source Operation ......................
3.2.2Preheating ............................................
3.2.3Cooking ................................................
3.2.4Shut-Down Procedure ..........................
3.3Cleaning ...............................................
3.4Drainage ...............................................
3.4.1Cooking Compartment Drainage ..........
3.4.2Drip/Spill Trough Drainage ...................
3.5T est Kitchen Bulletin .............................
PAGE
1-1
1-1
1-1
2-1
2-1
2-1
2-1
2-1
2-2
2-2
2-2
2-2
3-1
3-1
3-1
3-1
3-1
3-1
3-2
3-2
3-2
3-2
3-2
PARAGRAPH
5.4.8Buzzer ..................................................
5.4.9Cold W ater Condener Circuit ................
5.4.10Wiring ...................................................
SECTION 6 MAINTENANCE
6.1General .................................................
6.2Preventive Maintenance .......................
6.2.1Cooking Compartment Cleaning ..........
6.3Repair & Replacement .........................
6.3.1Door Latch Tension Adjustment ............
6.3.2Door Handle Tension Adjustment .........
6.3.3Door Gasket Replacement ...................
6.3.4Exterior Panel Removal ........................
6.3.5Steam & W ater Solenoid Valve
Replacement ........................................
SECTION 7 ILLUSTRATED PARTS LIST
7.1General .................................................
7.2Ordering Information .............................
7.3Index of Illustrated Parts List ................
7.4Illustrated Parts List ..............................
LIST OF TABLES
TABLE
SECTION 3 OPERATION
3-1Controls & Indicators ............................
PAGE
5-6
5-7
5-7
6-1
6-1
6-1
6-1
6-1
6-2
6-2
6-2
6-2
7-1
7-1
7-1
7-2/7-6
3-3
SECTION 4 PRINCIPLES OF OPERATION
4.1General .................................................
4.2Plumbing Circuits ..................................
4.2.1Steam Inlet Line ....................................
4.2.2Steam Exhaust & Drain Lines ...............
4.2.3Steam Exhaust Condensing System ....
4.3Electrica Circuits ...................................
4.3.1Control Circuit Components .................
4.3.1.160 Minute Timer ....................................
4.3.1.2Indicator Lights .....................................
4.3.1.3Buzzer ..................................................
4.3.1.4Door Interlock Switch ............................
4.3.1.5Thermostatic Switch .............................
SECTION 5 TROUBLE-SHOOTING
5.1General .................................................
5.2T rouble-Shooting ..................................
5.3Electrical Fault Isolation ........................
5.4Elec Trouble-Shooting Procedures .......
5.4.1Incoming Power ....................................
5.4.2Electrical Inspection ..............................
5.4.360 Minute Timer ....................................
5.4.3.1Timer Contacts .....................................
5.4.3.2Timer Motor ..........................................
5.4.4Door Interlock Switch ............................
5.4.5Steam Solenoid V alves .........................
5.4.6Indicator Lights .....................................
5.4.7Cooking Compartment Thermostat
Switch ...................................................
4-1
4-1
4-1
4-1
4-1
4-2
4-3
4-3
4-3
4-3
4-3
4-3
5-1
5-1
5-1
5-1
5-2
5-2
5-3
5-3
5-3
5-6
5-6
5-6
5-6
SECTION 5 TROUBLE-SHOOTING
5-1General Trouble-Shooting Guide ..........
5-2Electrically Fault Isolation Guide ..........
LIST OF ILLUSTRATIONS
FIGURE
SECTION 2 INSTALLATION
2-1T ypical Door Layout ..............................
SECTION 3 OPERATION
3-1Controls & Indicators ............................
SECTION 4 PRINCIPLES OF OPERATION
4-1Pictorial Diagram -
Steam & W ater Circuits ........................
SECTION 5 TROUBLE-SHOOTING
5-1Wiring Diagram, ST -12 .........................
5-2Schematic Diagram, ST -12 ...................
SECTION 7 ILLUSTRATED PARTS LIST
7-1Cabinet Assembly .................................
7-2Door Assembly .....................................
7-3Control Panel Assembly .......................
7-4Condenser Assembly ............................
5-1
5-2
2-3
3-2
4-2
5-4
5-7
7-3
7-4
7-5
7-6
i
Page 4
SECTION 1 INTRODUCTION
This service and parts manual contains general information, installation instructions, principles of operation, trouble-shooting,
and maintenance information for Market Forge ST-12 Pressureless Steam Cooker. Also included is a part list in which each
replaceable part is identified and shown in an accompanying exploded view.
1.1 Description
The ST-12 is a pressureless steam cooker consisting of a
controlled compartment enclosed in a single cabinet. The
compartment is equipped with a separate three-piece door
with inner gasket plate isolated from the exterior surface.
The door latch design ensures positive sealing of the inner
door. Steam delivery and steam-condensing circuits are
both electrically controlled. The operating controls are
displayed on a single front-mounted panel that includes a
timer with an indicator light for the selection of constant
steam or 60-minute-long duration cooking.
A separate steam source is required for operation of the
Pressureless Cooker and is normally purchased with it,
please refer to the respective manual for guidance.
1.2 Basic Functioning
The Model ST-12 compartment is equipped with controls,
allowing selection of constant steam or 60-minute timer
operation. The cooker becomes operational when it is set
to constant steam, or the timer is set at the desired
cooking time and the compartment door is closed. The
indicator light comes on and the steam solenoid valve
opens, allowing steam to flow into the compartment.
1.3 Service
Required service, both preventive and corrective, is
explained in Section 6. Should repairs be required, a
network of authorized service agencies is available to
assist with prompt service. A current Directory of
Authorized Service Agencies may be obtained by
contacting:
Product Service Department
Market Forge Industries Inc.
35 Garvey Street l Everett l MA l 02149
Tel: (617) 387-4100 l Fax: (617) 387-4456
Fax: (Outside MA) 1-800-227-2659
E-Mail: custserv@mfii.com l Website: http://www.mfii.com
The model and serial number must be referenced when
corresponding with Market Forge service personnel. The
data plate containing the serial number pertaining to the
equipment is located on the top front trim of the cabinet
base and also on the top panel of the steamer.
When steam flowing inside the compartment has raised
the interior temperature to 195°F, the contacts of a
thermostatic switch automatically close, completing the
circuit to the timer motor and starting the selected cooking
time period. At the end of the set interval, timer contacts
switch to shut off the cooking operation and sound a signal
buzzer. The buzzer is silenced by returning the timer dial
to the OFF position.
In the constant steam mode, operation will be continuous.
When steam and condensate is emitted from the
compartment it is directed through a drain screen inside
the compartment into the cooker drain line. A cold water
solenoid valve connected into the compartment drain line
is automatically actuated by a thermostatic switch in the
cooking compartment drain line to condense the steam to
water prior to discharge into the drain.
1-1
Page 5
SECTION 2 INSTALLATION
2.1 Assembly
The Pressureless Cooker is factory-mounted on a cabinet
base containing either a steam boiler or direct steam
connection controls for the cooker. The assembled unit is
shipped bolted to a skid, with cabinet feet in a separate
container. Steps required for assembly are as follows:
1. Remove the four bolts that fasten the equipment frame
to the skid.
2. Install feet in threaded mounting locations of the cabinet
frame.
3. Mount the two pan support racks in brackets and studs
inside cooking compartment.
4. Attach panels to lower cabinet. Detailed instructions are
enclosed with the panels.
5. Attach the drip trough on studs located on the face of
the unit.
2.2 Setting in Place
Level the unit in final location by turning the adjustable
feet. Using the cabinet top as a reference, obtain level
adjustment left-to-right and front-to-back.
2.3 Mechanical Connections
Since the Pressureless Cooker is interconnected at the
factory to the steam boiler or direct steam plumbing, no
field connections to the cooker are required. All electrical
and plumbing connections are routed to the steam boiler
cabinet through the 6-inch-high space between the floor
and the bottom edge of the cabinet frame. Connection
locations for the cooker mounted on steam boilers of
electric, gas, and steam coil utility and direct-connected
steam are shown in separate installation instructions for
each.
2.4 Water Connections
2.5 Installation Check-Out
Check-out procedures for the cooker mounted on steam
boilers of electric, gas, and steam coil or direct-connected
steam are given in separate installation instructions for
each. Procedures for the cooker only are included in
Subsection 2.5.2.
If the cooker fails to perform as described, consult Table 51 of the Trouble-Shooting Guide for corrective action. If
difficulty arises with the boiler, reference the separate
service and parts manual for that equipment.
Before making this check-out, the operator must be
thoroughly familiar with the operating procedures in
Section 3 and with the function of each control described
in Table 3-1. Reference Figure 3-1 for identification of
controls required in the following procedures.
2.5.1 Initial Control Settings
Before beginning the start-up procedures for the cooker,
the instruction plate and service manual for the steam
boiler must be consulted and all start-up procedures
completed to supply 15 PSI steam to the steam inlet line
for the cooker.
1. All steam boiler controls are in the operating mode and
15 PSI steam is applied to the cooker inlet plumbing.
2. Cooker timer for the compartment (Figure 3-1) is in the
OFF position.
3. Cooker compartment is empty of all information
materials, pan supports are mounted in place, and door
is open.
2.5.2 Cooker Check-Out
The cooker check-out procedures are as follows:
1. With the door open set timer to about the “4-minute”
position. Observe that indicator light is off and steam
does not enter compartment.
Before connecting water to this unit, have water supply
analyzed to make sure that hardness is no grater than
2.0 grains per gallon and pH level is within the range of
7.0–8.5. Water that fails to meet these standards should
be treated by the installation of a water conditioner.
EQUIPMENT FAILURE CAUSED BY INADEQUATE
WATER QUALITY IS NOT COVERED UNDER
WARRANTY!
CAUTION
PVC or CPVC are not acceptable materials for drains.
2. Close cooker compartment door. Observe that indicator
light turns on, and steam can be heard rushing into the
compartment simultaneously with the door closing.
3. Observe the boiler drain line for passage of steam into
the open floor drain. Correct steam condenser operation
is evidenced by presence of water flowing from the
drain line.
4. Observe cooker operation for several minutes. Operation is correct if timer dials begin to rotate after a short
delay period required for preheating. After the delay
period plus the “4-minute” initial setting, the timer dials
will return to the “0-Minute” position, at which a buzzer
sounds. The buzzer is silenced by turning the dial to the
OFF position.
2-1
Page 6
SECTION 2 INSTALLATION
2.5.3 Shut-Down Procedure
No shut-down procedure is required for the Pressureless
Cooker except to check that the timer dial is in the OFF
position and the compartment door are open. Consult the
steam boiler instruction plate and complete the shut-down
procedures for the boiler.
2.6 Reversing the Doors
The Pressureless Steam Cooker has a reversible cooking
compartment door. This section contains instructions for
reversing this door.
1. Turn off power to the unit.
2. Open the cooking compartment door
3. Remove the two screws that attach the top hinge to the
front of the unit.
4. Slide the door upwards, off the bottom hinge.
5. Remove the two screws that attach the bottom hinge to
the front of the units.
6. Remove the right and left side panels by unscrewing the
1 screw on each panel and sliding the panel down.
7. Remove the door interlock assembly by unscrewing the
two nuts that hold it in place (assembly is attached to
the screws in the top right hinge mounting holes, see
fig. 2-1).
8. Remove the four screws in the right side hinge
mounting holes and install them in the left side hinge
mounting holes (where the hinges were originally
mounted).
12. Remove the two white hole plugs from the left door
latch mounting holes, and insert them into the right
door latch mounting holes (where the door latch
assembly was originally mounted).
13. Rotate the door latch assembly 180°, and install into
the left door latch mounting holes.
NOTE:
Each stud on the latch assembly should have a plastic
washer, a spring, a plastic washer and a Nyloc type nut.
14. To adjust the tension of the door latch, tighten both
nuts down until the springs are fully compressed, then
back each nut off 1 1/2 turn.
15. Rotate the door 180° for mounting.
16. Slide the remaining hinge into the top door bearing.
17. Slide the door and hinge assembly down onto the
hinge which you have already mounted to the front of
the unit. Use the two screws to mount the top hinge
into the right upper hinge mounting holes. DO NOT
COMPLETELY TIGHTEN THE HINGE MOUNTING
SCREWS YET.
18. Slowly push the cooking compartment door closed
until it is latched.
19. The cooking compartment door can now be raised,
lowered, and/or rotated into position by bumping it with
the palm of your hand or by using a small rubber
mallet.
20. First, check the alignment at the front of the door by
making sure that the striker in the door is centered with
the latch mechanism on the front of the unit.
9. Using the nuts removed in step #6, reinstall the door
interlock assembly onto the 2 screws in the lower left
hinge mounting holes (see fig. 2-1) with by moving the
assembly over the cooking cavity to the other side of the
unit. Rotate the door interlock assembly 180° for
installation, so that the switch is now facing up.
10. Reinstall the top hinge and screws into the right lower
hinge mounting holes. Rotate the hinge 180° for
installa- tion, so that the pin which the door rides on is
now facing up. The hinge must be rotated because it
will now function as the bottom hinge. DO NOT
COMPLETELY TIGHTEN THE HINGE MOUNTING
SCREWS YET. These will be used later for adjusting
the door.
11. Remove the door latch assembly from the face of the
unit. The 2 nuts mounting the door latch are located
behind the face of the unit and must be accessed
where the right side panel was removed.
21. Square the door to the unit by raising or lowering the
hinge side of the door, keeping the latch centered with
the striker.
22. Visually inspect the door. Be sure that the door is
square to the unit, the striker is centered with the latch,
and the gasket is in contact with the entire lip of the
cooking compartment.
23. Gently open the cooking compartment door, taking
care not to move it out of position.
24. Tighten all 4 door hinge bracket mounting screws.
25. Close and visually inspect the door again, as
described in step 22.
26. Reinstall the left and right side panels, using the
screws for each panel.
2-2
Page 7
SECTION 2 INSTALLATION
INTERLOCK ASSEMBLY
ORIGINAL POSITION
DOOR LATCH ASSEMBLY
ORIGINAL POSITION
TOP RIGHT HINGE
MOUNTING HOLES
LOWER RIGHT HINGE
MOUNTING HOLES
TOP LEFT HINGE
MOUNTING HOLES
LEFT DOOR LATCH
MOUNTING HOLES
LOWER LEFT HINGE
INTERLOCK ASSEMBLY
POSITION WHEN DOOR IS
REVERSED
2-3
Figure 2-1 Typical Door Layout
MOUNTING HOLES
Page 8
SECTION 3 OPERATION
3.1 Operating Controls and Indicators
The controls and indicators required to operate the
Pressureless Steam Cooker are listed in Table 3-1,
together with a short functional description of each.
Figure 3-1 shows the physical location of each control and
indicator.
3.2 Operating Procedures
The ST-12 Pressureless Steam Cooker defrosts frozen
foods and cooks fresh and defrosted foods. The cooking
compartment permits selection of continuous (constant
steam) cooking or timed (0–60 minutes) cooking.
Instructions for operation are included in this section.
Consult Test Kitchen Bulletin for detailed cooking
information.
3.2.1 Steam Source Operation
The Pressureless Cooker is supplied mounted on a
cabinet containing either a steam boiler or controls for
direct-connected steam. Manual controls are accessed by
opening the cabinet door. The start-up procedure for the
steam source is completed once before each daily
operating period of the cooker. (For steam boilers, see
instruction plate.)
3.2.2 Preheating
3. Set timer cooking time:
a. constant steam—for continuous cooking
b. 60-minute timer—for timed cooking.
4. Set appropriate timer to the required cooking time (see
pages 3.3 to 3.6).
5. Turn off buzzer, which sounds to indicate cooking is
complete, by setting timer dial (1) to the OFF position.
6. Open door sightly at first letting most of the steam out of
the compartment and then fully open the door.
7. Unload by sliding pans of food from pan supports,
taking care to avoid hitting compartment opening.
3.2.4 Shut-Down Procedure
No shut-down procedure is required for the cooker except
to check the timer dial (1) are in the OFF position and that
the compartment door is open. When all cooking has been
completed for the day, the steam source must be shut off.
(For steam boilers, see instruction plate.)
CAUTION
When the unit is not in use, leave the cooking
compartment door slightly ajar to prolong the life of
the door gasket.
Before each initial operation of the cooker, and at any
other time when the cooking compartment is cold, a 1minute preheating period is required. To preheat the
cooker, put steam source into operation and proceed as
follows:
1. Close cooking compartment door.
2. Set 60-Minute Timer Dial (1) to “4-minute” setting.
NOTE:
Total elapsed preheating time equals the timer
setting plus a short delay period needed to active a
thermostatic switch included in the controls.
3. Turn off buzzer, which sounds to indicate cooking is
complete, by setting the Timer Dial (1) to OFF position.
3.2.3 Cooking
Before loading the cooker, be sure compartment is hot.
See Subsection 3.2.2 for preheating instructions.
1. Slide pans of food into cooking compartment pan
supports.
2. Close cooking compartment door.
3.3 Cleaning
After each period of daily operation (more frequently as
required to maintain cleanliness), the cooker should be
thoroughly cleaned by completing the following steps:
1. Remove left, right & center pan supports, and drain
screen by lifting up and off mounting studs. Wash with a
mild detergent. Rinse and set aside for reassembly.
2. Wash cooking compartment interior using a mild
detergent and water. Rinse and dry thoroughly.
3. Replace pan supports, and drain screen in compartment
and leave door slightly ajar.
3.4 Drainage
3.4.1 Cooking Compartment Drainage
The bottom of the cooking compartment is angled slightly
toward the rear of the unit. This assures that any
condensate build-up or spills will be directed toward the
drain hole, which is located at the rear bottom center of the
cooking compartment. Any liquid exiting the cooking
compartment runs down the cooking compartment drain
tube and into the drain line.
3-1
Page 9
SECTION 3 OPERATION
PLUS - 12
TIMER
2
1
3
6
4
TIMED
STEAM
5
9
8
7
START
CLEAR
0
STOP
4
O
OFF
3.4.2 Drip/Spill Trough Drainage
The ST-12 Pressureless Steam Cooker has a drip/spill
trough below the cooking compartment door. It will catch
CONSTANT
STEAM
any condensate gathering on the front of the unit when the
door is opened.
3
5
5
MANUAL OPTION
1
STEAM
UPPER COMPARTMENT
&
LOWER COMPARTMENT
o
OFF
STEAM
LOWER COMPARTMENT
&
KETTLE
STEAM
UPPER COMPARTMENT
&
LOWER COMPARTMENT
o
OFF
STEAM
LOWER COMPARTMENT
&
KETTLE
C
O
N
S
F
T
F
O
A
N
S
T
T
E
A
M
0
60
5
10
15
20
40
25
35
30
55
50
45
DIGITAL OPTION
2
REF. NUMBER
1
2
3
4
TABLE 3-1
CONTROLS & INDICATORS
(See Figure 3-1)
DESCRIPTION
Timer/Constant Steam
Indicator Light
Digital Timer
Mode Switch
FUNCTION
Controls cooking up to
60 Minutes or uses
constant operation.
Indicates cooker is in
operation.
Control cooking up to
99 minutes or constant.
Constant Steam/Timer
O
OFF
CONVECTION
STEAM
COOKER
Figure 3-1 Controls & Indicators
3-2
Page 10
SECTION 3 OPERATION
TEST KITCHEN BULLETIN
Model ST-12 Pressureless Cooker
Facts On Parade
3.5 TEST KITCHEN BULLETIN
1. Frozen vegetables should always be cooked in perforated 12” x 20” x 2 1/2” (1/1 65mm) pans.
2. Frozen entrees should be underlined with a perforated pan for best results. If they are defrosted first, the heating
time will be decreased.
3. Fresh foods may also be cooked in this unit. Vegetables and other foods where the stock is not to be retained
should be cooked in perforated 12” x 20” x 2 1/2” (1/1 65mm) pans for the most nutritious results.
4. There is a thermostatic time delay built into this unit which adapts the unit to the proper cooking time. This means
that the total time will usually be longer than the time setting.
5. There is a safety interlock switch on the door which shuts off the steam each time the door is opened if the unit is in
the cooking cycle.
6. Compartments may be filled and timer set simultaneously.
7. Sheet pans will fit in compartment with the center rack removed.
8. All foods, except cakes and pastry, can be cooked in a steam cooking unit.
9. Steam cooked meals have greater nutritional value since they retain most of their vitamins and minerals.
10. Because foods are cooked faster by the higher temperatures of steam cooking, they can be prepared closer to
serving time, insuring maximum freshness.
11. Steam cooked foods have a higher percent yield more portions per dollar spent.
12. Food may be served from the same pan in which it is steam cooked, thus reducing food breakage since there is no
extra handling or transferring of food from cooking pans to serving pans. It also reduces pot washing tasks.
13. Some important advantages of steam cooking are labor saving, reduced operating costs, space saving, and the
lifting of heavy stock pots is eliminated.
14. Rice and spaghetti products, if thoroughly wet at the start of the cooking process, are very easily prepared.
15. Food such as potatoes, poultry, seafood, and some meats may be blanched in the steam cooker, thus reducing the
total cooking time and grease absorption.
16. Fuel is used only when the steam cooking unit is in operation.
17. The steam cooker will loosen foods burned on pans making washing easier.
18. Solid pans are recommended when liquid is to be retained and perforated pans when the liquid is not to be retained.
19. Eggs may be cooked out of the shell if they are to be chopped which eliminates peeling after steaming.
20. The steam cooker can be opened during the cooking period to add or remove items. If any time is lost, an
adjustment may be made on the timer.
21. Steam cooking information, including recommended pan size and type, weight per pan, cooking times and pan
yields are given on the following pages of this manual.
3-3
Page 11
SECTION 3 OPERATION
The ST-12 Pressureless Cooker is a one compartment unit. The compartment holds twelve 12” x 20” x 2 1/2” or six 12” x
20” x 4” pans. This unit enables the cook to prepare foods close to the time of service. The cooking times given are timer
settings and should be set in a preheated compartment. There is a thermostatic time delay in the compartment that
adjusts the total time depending on the temperature and amount of the food. Therefore the total time will be greater than
the timer setting. At the end of the timer cooking cycle the buzzer will sound, steam will stop flowing and the food can be
removed.
FROZEN VEGETABLES
ITEM
Asparagus Spears
Beans, Green Regular
Beans, Green French Cut
Beans, Lima
Broccoli
Brussel Sprouts
Carrots
Cauliflower
Corn-Cut
Mixed Vegetables
Peas (Loose)
Spinach
Squash
Approx. Frozen
Weight
Per Pan
7 1/2 lbs. (3.4 kg)
6 lbs. (2.7 kg)
6 lbs. (2.7 kg)
7 1/2 lbs. (3.4 kg)
6 lbs. (2.7 kg)
7 1/2 lbs. (2.7 kg)
6 lbs. (2.7 kg)
6 lbs. (2.7 kg)
7 1/2 lbs. (3.4 kg)
7 1/2 lbs. (3.4 kg)
7 1/2 lbs. (3.4kg)
9 lbs. (4kg)
12 lbs. (5.4 kg)
Recommended
12” x 20” (1/1)
Perforated Pan
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
Number
of Pans
12
12
12
12
12
12
12
12
12
12
12
12
12
Timer
Settings in
Minutes
12-15
10-15
5-7
12-15
4-6
10-15
10-15
7-12
8-12
8-12
3-5
Must be defrosted
Must be defrosted
Approx. Number
Cooked Servings
Per Pan
30 3 oz. (85 g)
25 3 oz. (85g)
25 3 oz. (85 g)
30 3 oz. (85 g)
25 3 oz. (85 g)
30 3 oz. (85 g)
25 3 oz. (85 g)
25 3 oz. (85 g)
30 3 oz. (85 g)
30 3 oz. (85 g)
30 3 oz. (85 g)
30 4 oz. (115 g)
50 3 oz. (85 g)
ITEM
Lobster Tails
6-8 oz. (170-255 g)
Shrimp, C.D.P.
Shrimp Green
Bulk Pack Frozen
Bulk Pack Defrosted
ITEM
Canned Vegetables
FROZEN PREPARED ENTREES
Weight Per Pan
7-8 lbs. (3.2-3.6 kg)
16-20 lbs. (7-9 kg)
16-20 lbs. (7-9 kg)
3 1/2-4 lbs. (1.6-1.8 kg)
3 1/2-4 lbs. (1.6-1.8 kg)
VEGETABLES (CANNED)
Weight Per Pan
7 lbs. (3.2 kg)
Recommended
12” x 20” (1/1)
Perforated Pan
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
Recommended
12” x 20” (1/1)
Perforated Pan
2 1/2” (65mm)
3-4
Number
of Pans
12
12
12
12
12
Number
of Pans
12
Timer
Settings in
Minutes
15-25
8-11
11-15
35-45
25-35
Timer
Settings in
Minutes
5-10
Approx. Number
Cooked Servings
Per Pan
15 6 oz. (170 g)
75 3 oz. (85g)
50 3 oz. (85 g)
10 6 oz. (170 g)
10 6 oz. (170 g)
Approx. Number
Cooked Servings
Per Pan
25-30 3oz. (85 g)
Page 12
SECTION 3 OPERATION
PRESSURELESS STEAM COOKING TIMER SETTINGS & PORTIONS
VEGETABLES
ITEM
Beans, Snap Green
or Waxed
Beets (50mm) 2” E
Broccoli 1/2-3/4”
(12-20mm) Stalks
Carrots Sliced
Cauliflower, Trimmed
1 1/2-2” (38-50 mm)
Corn on Cob Husked
Cabbage Head 1/4-1/6
Cored
Onions (50 mm) 2" E
Peas, Shelled
Potatoes, French Fry Cut
Potatoes, Regular
Cut, 3” (75 mm)
Approx. Frozen
Weight
Per Pan
6 lbs. (2.7 kg)
7 1/2 lbs. (3.4 kg)
6 lbs. (2.7 kg)
9 lbs. (4 kg)
6 lbs. (2.7 kg)
1 doz.
5 lbs. (2.25 kg)
6 lbs. (2.7 kg)
5 lbs. (2.25 kg)
10 lbs. (4.5 kg)
10 lbs. (4.5 kg)
Recommended
12” x 20” (1/1)
Perforated Pan
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
Number
of Pans
12
12
12
12
12
12
12
12
12
12
12
Timer
Settings in
Minutes
18-22
40-50
14-18
18-21
12-16
10-15
14-18
20-25
5-6
18-21
35-40
Approx. Number
Cooked Servings
Per Pan
25-30 3 oz. (85 g)
30-35 3 oz. (85g)
25-30 3 oz. (85 g)
35-40 3 oz. (85 g)
30-35 3 oz. (85 g)
12
15-20 4 oz. (115 g)
25-30 4 oz. (115 g)
25-30 3 oz. (85 g)
50 3 oz. (85 g)
50 3 oz. (85 g)
Spinach, Cleaned Cut
Squash, Summer, Sliced
1” thick (25 mm)
Squash, Winter Peeled
Diced Turnip
ITEM
Chicken Cut-up
Chicken, 4 lbs. Whole
Fowl, 5lbs. or more Whole
Fish, Fillets
Frankforts
Hamburgers3 oz. (85 g)
Meatballs 1 oz. (30 g)*
3 lbs. (1.4 kg)
7 lbs. (3.2 kg)
9 lbs. (4 kg)
5 lbs. (2.25 kg)
Weight Per Pan
8 lbs (3.6 kg)
3 each
2 each
3 lbs (1.4 kg)
5 lbs (2.3 kg)
5 lbs (2.3 kg)
6 lbs (2.7 kg)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
MEAT, POULTRY & FISH
Recommended
12” x 20” (1/1)
Perforated Pan
2 1/2” (65mm)
4” (100 mm)
4” (100 mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
Number
of Pans
12
12
12
12
2
6
6
12
12
12
12
3-5
7-10
10-15
28-32
Timer
Settings in
Minutes
20-30
45-50
50-60
10-15
3-5
18-22
20-25
10-12 3 3/4 oz. (105 g)
30-35 3 oz. (85 g)
25-30 3 oz. (85 g)
20-25 4 oz. (115 g)
Approx. Number
Cooked Servings
Per Pan
15-20 2 oz. Protein (55 g)
25-30 2 oz. Protein (55 g)
20-25 2 oz. Protein (55 g)
12-15 2 oz. (55 g)
35-40 2 oz. (55 g)
20-25 2 oz. Protein (55 g)
20-25 2 oz Protein (55 g)
3-5
Page 13
SECTION 3 OPERATION
PRESSURELESS STEAM COOKING TIMER SETTINGS & PORTIONS
MEAT, POULTRY & FISH CONTINUED
ITEM
Meatloaf*
Pork Chops, 4 oz.
Loin Bone (115 g)
Sausage 1 1/2 oz. (45 g)
Turkey On Carcass
TurkeyOff Carcass
ITEM
Eggs In Shell
Eggs Out of Shell
Rice — Bulletin 16
gives direction
Spaghetti — Bulletin 13
gives direction
Approx. Frozen
Weight
Per Pan
15 lbs (6.8 kg)
6 lbs (2.7 kg)
6 lbs (2.7 kg)
20-22 lbs (9-10 kg)
10-12 lbs (4.5-5 kg)
Weight
Per Pan
3 dozen
4 dozen
4 lbs. (1.8 kg)
3 lbs. (1.4 kg)
Recommended
12” x 20” (1/1)
Perforated Pan
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
MISCELLANEOUS
Recommended
12” x 20” (1/1)
Perforated Pan
2 1/2” (65mm)
2 1/2” (65mm)
2 1/2” (65mm)
4” (100mm)
Number
of Pans
12
12
12
2
12
Number
of Pans
12
12
12
6
Timer
Settings in
Minutes
40-50
25-30
18-21
2-2 1/2 hrs.
1-1 1/4hrs.
Timer
Settings in
Minutes
9-11
6-8
18-22
18-22
Approx. Number
Cooked Servings
Per Pan
50-60 2 oz. Protein (55 g)
24 2 oz. Protein (55 g)
18-20 2oz. (55 g)
50-60 2 oz. Protein (55 g)
55-65 2 oz. Protein (55 g)
Approx. Number
Cooked Servings
Per Pan
36 -1 egg each
48 - 1 egg each
60-65 3oz. (85 g)
40-45 4oz. (115 g)
3-6
Page 14
SECTION 4 PRINCIPLES OF OPERATION
4.1 General
The ST-12 Pressureless Steam Cooker consists of one
cooking compartment in a single cabinet assembly. The
compartment is fitted with an independent electrically
controlled steam circuit and spring-loaded, self-sealing
door with a slam action latch. The compartment can be
used for either constant steam or 60-minute timing. The
principles of operation in this section include an
explanation of steam, steam condensing, and electrical
circuits and their functioning.
4.2 Plumbing Circuits
The plumbing circuit consists of the piping, steam solenoid
valve, steam jet-pipe, drain, and cold water condenser
required to provide controlled steam application to the
cooking compartments. A simplified diagram of this circuit
is shown in Figure 4-1.
NOTE:
Figure 4-1 is strictly a pictorial schematic diagram and is
not intended to show the actual configuration of the
plumbing. All components are shown in correct
relationship with each other. However, the diagram does
not show their actual locations or position within the
cooker.
As shown in the diagram, steam inlet and exhaust
connections are connected at the factory directly into a
steam boiler or direct-connected steam plumbing enclosed
within the base cabinet on which the cooker is mounted.
The boiler (or direct-connected steam control system) is
equipped to supply constant, regulated steam at
14–15 PSI. Steam exhaust, having been reduced to water
by the cold water condenser, is directed into the boiler (or
direct-connected steam control) drain system.
Steam inlet lines for the compartment are equipped with a
normally closed solenoid valve operated by the electrical
control circuit. The inlet valve is opened whenever the
compartment control circuit is activated by use of the 60minute timer.
4.2.1 Steam Inlet Line
A steam supply line is plumbed from the boiler output (or
direct-connected steam control) to a 1/2-inch barb fitting
connected to the input sides of the steam inlet solenoid
valve. When a cooking compartment is not in use, the
valve for the compartment remains closed to prevent
steam from entering. During operation, the appropriate
inlet solenoid valve is opened by activation of the control
circuit.
Steam is projected onto the surface of pans of food loaded
into the compartment by an orifice located inside the
compartment. Steam continues to flow through the
compartment in this manner until the control circuit closes
the solenoid valve.
4-1
4.2.2 Steam Exhaust and Drain Lines
Perforated strainers at the drain line opening inside the
compartment allow only steam, condensation, and liquid
cooking drainage to enter. Prior to discharge into the boiler
drain system, steam is converted to water by the cold
water condensing system for the compartment.
4.2.3 Steam Exhaust Condensing System
The steam condensing system consists of a, two-position,
normally closed cold water solenoid valve, with outlet
sides connected into the exhaust plumbing for each
cooking compartment. A spray nozzle directs cold water
about the inside of the drain lines to increase cold water
contact with exhausted steam. Valve inlet side is
connected remote from the supply line of the steam boiler
(or direct-connected steam plumbing). The valve responds
to a thermostatic switch located inside the compartment.
When the timer starts the cold water solenoids will
energize.
4.3 Electrical Circuits
The electrical circuits of the cooker control the power to
activate timer motors and energize solenoid-operated
valves and circuits, which in turn control application of
steam to the cooking compartment and condensation of
steam from the exhaust line. The cooker operates on
120V, 2 amp, 60Hz electrical service connected to all
circuits from the circuits of the steam boiler (or directconnected steam controls) contained within the cabinet on
which the cooker is mounted. Power is supplied to the
control circuit at all times when the shut-off device (Circuit
Breaker) for the unit (installed by an certified Electrician) is
in the ON position.
4.3.1 Control Circuit Components
A brief description of the electrical circuit elements follows.
4.3.1.1 60 Minute Timer/Constant Steam
The timer contains a 120-volt AC synchronous motor that
drives a timing dial through a gear reduction and clutch
mechanism. The timer dial is manually set for any interval
of operation from 0 to 60 minutes or constant steam as
read on the calibrated dial face. The manual rotation of the
dial moves the common element (1) of the timer switch
from the neutral (OFF) position to contact (3), which
connects with the steam inlet solenoid valve operating
circuit.
The cooker is placed into automatic operation with the
setting of the timer dial. Its timing cycle, however, is
automatically delayed by a thermostatic switch, which
assures operating temperature is achieved before the
timer motor begins to “time out.”
Page 15
SECTION 4 PRINCIPLES OF OPERATION
WATER INLET TO
TOP CAVITY
STEAM JET PIPE
(2 PER COMPARTMENT)
STEAM LINE
TO CAVITY
WATER INLET
FROM BOILER
Figure 4-1 Pictorial Diagram, Steam & Water Circuits (Model ST-20 Shown Here)
When the timer motor has operated for the preset
duration, the common element is transferred to contact (4),
returning the inlet solenoid valve to the closed position and
energizing the buzzer. Contact to the buzzer circuit
remains closed until the dial is manually turned to the OFF
position, returning the common element (1) of the timer
switch to the neutral position.
4.3.1.2 Indicator Lights
WATER TO
DRAIN LINE
STEAM LINE
TO CAVITY
STEAM LINE
FROM BOILER
mally open contacts. The switch is operated by the
proximity of a magnet within the door. When the door is
open, the switch contacts remain in the open position.
When the door is closed and securely latched in place, the
magnet is near the switch to close the contacts.
Connected between the operating contact (3) of the timers
and the steam inlet solenoid valve, the door switch acts as
a protective device to interrupt valve operation unless the
door is closed.
An indicator light is included for the compartment. The light
remains on (red) at all times when the coinciding timer dial
is set and the door interlock switch is closed. The light
turns off at the end of the timed cooking duration or when
the set time has elapsed.
4.3.1.3 Buzzer
The buzzer is an alarm device that operates by oscillation
of a striker against the core of an electromagnet. When the
60-minute timer dials reach the “0-Minute” position, the
buzzer coil is energized to sound the buzzer. Movement of
the timer dial to the OFF position opens the contact to the
buzzer coil to shut it off.
4.3.1.4 Door Interlock Switch
The interlock switch is a single-pole proximity switch with
normally open contacts. The switch is operated by the nor-
4.3.1.5 Thermostatic Switch
The thermostatically operated switch is a two-position,
normally open switch mounted on the cooking
compartment. The switch functions to activate the cold
water solenoid valves of the steam condensing system
and to delay timer motor operation until the compartment
temperature reaches 195°F, thus assuring that cooking
temperature exists throughout the timed duration.
4.3.1.6 Digital Timers (Optional)
The timer controls the steam to the cavity by either a
constnat steam setting or a used defined timer that will be
programmed by the user into the timer
4-2
Page 16
SECTION 5 TROUBLE-SHOOTING
5.1 General
The information in this section is intended to assist both
the operator and service personnel in locating the general
source of problems that may occur with the cooker. Before
following any of the procedures given in this section, the
operator should be thoroughly familiar with the operating
instructions and the function of all controls that are
described in Section 3. If the problem cannot be readily
corrected, the operator should contact the nearest Market
Forge service agency for assistance.
5.2 Trouble-Shooting Guides
A trouble-shooting guide for use by service personnel is
given in Table 5-1.
TABLE 5-1 GENERAL TROUBLE-SHOOTING GUIDE
PROBLEM
1. INDICATOR LIGHT FAILS TO
LIGHT WITH TIMER SET.
PROBABLE CAUSE
a. Power to Cooker OFF.
b. Door Interlock Switch contacts
not closed.
c. Door Interlock Switch faulty.
5.3 Electrical Fault Isolation
Correction of an electrical failure first requires isolation of
the fault to a single circuit or component. In most cases,
the nature of the failure and its effect upon the operation of
the cooker will be sufficient to narrow it down to one or
more circuit elements. Table 5-2 is provided as a guide for
isolating electrical faults.
5.4 Electrical Trouble-Shooting Procedures
Before performing the trouble-shooting procedures in this
section, the serviceman must be familiar with the function
of all controls as described in Section 3 as well as with the
Principles of Operation described in Section 4.
REMEDY
a. Locate External Circuit Breaker for
incoming power & place in ON position.
b. Shut cooker door to close switch contacts,
Check alignment of door with switch.
c. Replace Switch (see subsection 5.4.4).
2. STEAM FAILS TO ENTER
COOKING COMPARTMENT WITH
INDICATOR LIGHT ON.
3. STEAM ENTERS COMPARTMENT
CONTINUOUSLY. TIMER DIAL NOT
TURNING.
4. STEAM CONTINUES TO FLOW
INTO COMPARTMENT AND/OR
BUZZER FAILS OT SOUND AT
END OF TIMER SETTING.
5. STEAM FLOWS CONTINUSLY
FROM BOILER (
ECTED STEAM CONTROL
WITH COOKER IN OPERATION.
OR DIRECT CONN-
) DRAIN LINE
d. Indicator Light burned out.
e. Faulty Timer contacts.
f. Faulty Wiring.
a. Faulty Steam Solenoid Valve.
b. Faulty Wiring.
a. Constant Steam Position.
b. Faulty Thermostatic Switch.
c. Faulty Timer Motor.
d. Faulty Steam Solenoid Valve.
e. Faulty Wiring.
a. Timer Contacts Faulty.
b. Buzzer Faulty.
c. Faulty Wiring.
a. Cold water not connected.
b. Faulty Thermostat.
c. Faulty Cold water.
d. Replace Light.
e. Replace Timer (see subsection 5.4.3).
f. Inspect condition od wire & tightness of all
connections, Correct as needed.
a. Replace Valve (see subsection 5.4.5).
b. Inspect condition od wire & tightness of all
connections, Correct as needed.
a. Move knob to timing location.
b. Replace Switc (see subsection 5.4.7).
c. Replace Timer (see subsection 5.4.3).
d. Replace Valve (see subsection 5.4.5).
e. Inspect condition od wire & tightness of all
connections, Correct as needed.
a. Replace Timer (see subsection 5.4.3).
b. Replace Buzzer (see subsection 5.4.8).
c. Inspect condition od wire & tightness of all
connections, Correct as needed.
a. Turn on external shut-off valve.
b. Replace Thermostat (see subsection 5.4.7).
c. Replace Valve.
d. Faulty Wiring.
d. Inspect condition od wire & tightness of all
connections, Correct as needed.
5-1
Page 17
SECTION 5 TROUBLE-SHOOTING
The electrical trouble-shooting procedures that follow
require access to components and terminals of the
electrical control panel shown in Figure 7-3. Electrical
controls are reached by removing screws that fasten the
control panel to the frame. The panel may be pulled
forward for testing while interconnected to the cooker
circuits or disconnected at the pin connection for complete
removal and repair.
5.4.1 Incoming Power
Before trouble-shooting any of the electrical parts or
assemblies, verify that power is being supplied to the
cooker. Incoming power is connected at the boiler (or
direct-connected steam) control box located in the base
cabinet. With power connected to the cooker, an AC voltmeter is used to measure 120 volts across L1 and L2. If
120 volts is present, and the cooker will not operate, the
fault lies within the electrical circuits of the cooker.
5.4.2 Electrical Inspection
The first step in any electrical trouble-shooting procedure
is a thorough physical inspection of all wiring connections.
To access electrical components, remove the control panel
as explained in Subsection 6.3.4.
Warning
Before removing control panel or checking connections
and wiring, be sure that the circuit breaker for incoming
power is OFF. When power is supplied, all exposed
terminals of the control panel carry 120 volts.
Check all wiring connections by hand to assure that both
ends of all connection points are tightly secured. Use a
screwdriver to tighten connection points. If necessary,
visually inspect all quick-disconnect terminals for evidence
of corrosion. Terminals in this condition should be
separated, cleaned with emery cloth until shiny, and tightly
reconnected.
5.4.3 60-Minute Timer
5.4.3.1 Timer Contacts
Defective timer contacts will result in failure of either
cooker compartment to operate. When this occurs, remove
the control panel (see Subsection 6.3.4), and proceed as
follows:
1. Turn off power to the cooker at external circuit breaker.
timer contacts are defective and the timer must be
replaced.
5. Move ohmmeter leads to terminals 1 and 4.
6. Rotate timer dial to “0-Minute” position (an audible click
indicates correct position). If zero ohm reading cannot
be obtained, the timer is defective and must be
replaced.
7. Remove ohmmeter and replace all five leads on timer
terminals as shown in Figure 5-1.
5.4.3.2 Timer Motor
A defective timer motor will cause continuous operation in
the Time mode, with the timer dial failing to return to the
“0-Minute” position. Since thermostatic switch failure can
cause the same symptom, fault must first be isolated to
the timer by testing the thermostat (see Subsection 5.4.8).
To confirm timer motor condition, proceed as follows:
1. Carefully check motor wire leads and tighten loose
connections.
WARNING
Use care while working with control panel. Terminals carry
120 volts.
2. Turn on power to the cooker.
3. Set timer dial (any setting beyond “0-minute”). If
operation is correct, the motor fails to operate, it is
defective and the entire timer must be replaced.
4. Shut off power to the cooker.
5.4.4 Door Interlock Switch
Malfunction of the cooker door interlock switch prevents
timer indicator lights from turning on and steam solenoid
from opening when the timer dial is set. If steam does not
enter the compartment and the indicator light fails to turn
on with the door latch securely engaged, the fault may be
in the door interlock switch. Proceed as follows:
1. Turn off power to the cooker.
2. Disconnect wires to the door switch terminals
(see Figure 5-1).
2. Disconnect all five wires from timer terminals
(see Figure 5-1).
3. Connect an ohmmeter between terminals 1 and 3.
4. Rotate timer dial beyond the “0-Minute” point (any
setting) to obtain a reading of zero ohms on the
ohmmeter. If zero ohm reading cannot be obtained,
3. Connect an ohmmeter between the terminals of the
switch.
4. Actuate the switch by closing the cooking compartment
door. If a zero reading cannot be obtained, the switch is
defective and must be replaced.
5. Remove the ohmmeter and replace the leads on switch
terminals (see Figure 5-1).
5-2
Page 18
SECTION 5 TROUBLE-SHOOTING
TO FRONT
FRAME GRD
STUD
14
5
47
B
A
A
THERMOSTAT
SWITCH S3
B
13
9
59
COLD WATER
CONDENSER
V1
33
B
60
60
50
A
BUZZER
B1
(UPPER)
5
7
105
1 2 3 7 8
B
9
PILOT-LIGHT
LT1 GRN
A B
2 1
TB1
6
TIMER
24
DONE RUN
ON
21
11
A
TIMER
60 MIN. TIMER
TMR1 (UPPER)
CONNECTOR
1111
1212
11
BLK
109654
4
106
22
55
12
B
53
3
8
10
11
2
2
9
9
3
3
5655
27
101
29
BLK
34
51
30
BLK
WHT
WHT
REED SWITCH
S1
A
RELAY R1
14
5
B
13
9
56
51
BLK
102
WHT
28
WHT
31
59
36
WHT
A
STEAM SOL.
VALVE V3
50
4 4
32
49
TO 120/240V
SUPPLY BOX
185
184
5 5
6 6
7 7
10 10
8 8
P1 J1
TO FRONT
FRAME GRD
STUD
NOTES:
1. ALL WIRES 18 AWG AND YELLOW EXCEPT WHERE INDICATED OTHERWISE.
2. FOR WIRE LEAD SCHEDULE REFER TO DRAWING C 91-6472.
Figure 5-1 Wiring Diagram Mechanical Controls, Model ST-12
L1
N (L2)
BLK
EXISTING
WIRES
TO 120/240V
SUPPLY BOX
48
11 3
L1
BOILER CONTROL BOX
(AUTOMATIC BOILERS)
(OPTIONAL)
47
186
N
TO 120/240V
SUPPLY BOX
5-3
Page 19
SECTION 5 TROUBLE-SHOOTING
NOT AVAILIABLE AT THIS TIME
Figure 5-1 Wiring Diagram Digital Controls, Model ST-12 (NOT AVAILIABLE AT THIS TIME)
5-4
Page 20
SECTION 5 TROUBLE-SHOOTING
5.4.5 Steam Solenoid Valve
When either inlet solenoid valve fails to operate, the fault
may be a defective coil. A defective coil is found using an
AC volt-meter to check the voltage at the coil wire
terminals, with the cooker compartment operating in either
constant steam or 60-minute timer mode. If voltage of
120 volts is present and the coil fails to open the valves,
the fault is in the valve coil. Defective valve coils are not
separately replaceable, requiring complete valve
replacement.
5.4.6 Indicator Lights
If the cooker compartment functions correctly, with the
single exception that the indicator light fails to light during
operation, the fault is a defective indicator light. A “burned
out” or defective light is verified by using an AC volt-meter
at the leads, with input power on the selector switch in the
correct position for that timer, the timer set, and the door
latches closed. If 120 volts is present, the fault is in the
indicator light and requires replacement. If 120 volts is not
present, the fault is in the wiring or control components
(selector switch, timer, or door switch).
5.4.7 Cooking Compartment
Thermostatic Switch
A thermostatic switch included in the circuit for the timer
motor delays timer operation until steam flowing into the
compartment satisfies the temperature-actuated switch
device. If a timer motor fails to operate within about one
minute after the indicator light comes on (with cooker
compartment empty), the cause may be a defective
thermostatic switch. To test the switch, proceed as follows:
buzzer coil connections with input power on and selector
switch and coinciding timer dial set at the “0-Minute”
position. If voltage is 120 volts, the fault is in the buzzer,
which must be replaced. If 120 volts is not present, the
fault is in the wiring or control components (timer or
selector switch).
5.4.9 Cold Water Condenser Circuit
If during cooker operation steam exits from the drain line
opening (located in lower boiler compartment) and the
condensing system fails to operate, as evidenced by
repeated discharge of water from the drain line, the
condensing circuit is malfunctioning. The failure can be
caused by a defective condenser thermostat or cold water
solenoid coil, or by wiring failure. To test condenser
thermostat, refer to Subsection 5.4.8.
If the condenser thermostat functions correctly, but either
of the cold water solenoid valves fails to operate, the
cause might be a faulty valve coil. A defective coil is found
using an AC volt-meter to check the voltage at the coil wire
terminals with the cooker compartment in operation. If
voltage of 120 volts is present and the valve fails to open,
the fault is in the valve coil. Defective valve coils are
separately replaceable.
5.4.10 Wiring
All of the electrical components of the cooker (timers,
indicator lights, etc.) are connected to each other by wiring
shown in Figure 5-1. If all of the electrical components are
operating correctly (and the incoming power has been
checked), but the cooker fails to operate, the fault lies in
the wiring.
1. Disconnect the two wires connected to the thermostatic
switch terminals.
2. Connect an ohmmeter between the two terminals of the
switch.
3. Place the cooker into operation and observe ohmmeter
dial. Within one minute of operation, the switch contacts
close automatically to register a zero ohm reading on
the dial. If a zero ohm reading is not obtained, the
switch is defective.
4. Shut off cooker, disconnect ohmmeter leads, and
replace wires on switch terminals.
5.4.8 Buzzer
If the buzzer does not sound at the termination of the
operator-selected timer setting (timer dial returned to “0Minute” position), the fault may be a defective buzzer.
Buzzer operation is verified using an AC volt-meter at the
Figure 5-1 is a diagram that shows all terminals and
interconnections within the electrical circuits. All numbered
terminals are identified and all leads number-coded as
shown. Connections can be easily removed. Figure 5-2
shows the same information schematically and is an aid in
isolating circuits for testing.
Using an ohmmeter, wiring continuity between the
connections shown on the wiring diagram (Figure 5-1) is
readily verified. This is best done in stages, removing only
those wires required for each continuity check. As each
lead is replaced, it should be checked for evidence of
corrosion, and cleaned if necessary. All leads must be
tightly attached so as to provide a good electrical
connection.
5-5
Page 21
SECTION 5 TROUBLE-SHOOTING
Figure 5-3 Ladder Diagram, Plus 12 (1) Compartment
5-6
Page 22
SECTION 6 MAINTENANCE
6.1 General
This section contains both preventive and corrective
maintenance information. Preventive maintenance may be
performed by maintenance personnel at the establishment
in which the cooker is installed. It is recommended that
user personnel never attempt to make repairs or
replacements to the equipment without the assistance of
authorized service. Assistance in service methods or a
current Directory of Authorized Agencies may be obtained
from Market Forge (see Subsection 1.3).
6.2 Preventive Maintenance
A good preventive maintenance program begins with the
daily cleaning procedure described in Subsection 3.3.
Additional preventive maintenance operations are
presented in this section. In establishments that employ
full-time maintenance personnel, the tasks described can
be assigned to them. For other installations, tasks
requiring mechanical or electrical experience should be
performed by an authorized service agency.
The following paragraphs set forth minimum preventive
maintenance procedures that must be completed
periodically to assure continued trouble-free operation of
the cooker.
2. Remove the control panel by removing the eight
mounting screws and disconnecting the wire plug and
restraining wire.
3. Tighten both nuts down until the springs are fully
compressed.
4. Back each nut off 1/2 turn.
5. Remount the control panel, reconnecting wire plug and
restraining wire.
6.3.2 Door Handle Tension Adjustment
Procedure:
1. Open the cooking compartment door.
2. Remove the six screws and washers from the top edge
and bottom edge of the door.
3. Remove the inner door gasket mounting plate assembly
from the outer door. Do not disassemble these three
components—remove them as an assembly.
4. Tighten both nuts down until the springs on the outer
door are fully compressed.
CAUTION
Under no circumstances should hardware (or parts) be
replaced with a different length, size, or type other than as
specified in the parts list. The hardware used in the cooker
has been selected or designed specifically for its
application, and the use of other hardware may damage
the equipment and will void any warranty.
6.2.1 Cooking Compartment Cleaning
A daily cleaning of the cooking compartment and pan
supports is required. See Subsection 3.3 for details.
6.3 Repair & Replacement
Section 7 of this manual contains a listing of all
replaceable parts and associated exploded views of the
ST-12 Cooker. In most cases, disassembly procedures will
be obvious from the exploded views. Instructions follow for
procedures that are not readily apparent.
6.3.1 Door Latch Tension Adjustment
CAUTION
Shut off main electrical power to unit.
Procedure:
1. Open the cooking compartment door.
5. Back each nut off 1/2 turn.
6. Remount the inner door gasket mounting plate
assembly by assembling the six screws and washers.
6.3.3 Door Gasket Replacement
The cooking compartment door gaskets are made of a
silicone-type rubber material that is very durable but
subject to wear during normal operation. Should the
gasket leak, readjust the door gasket to the unit or replace
it.
Procedure—Replace Gasket:
1. Open the cooking compartment door.
2. Remove the six screws on the outside of the door, and
remove the inner door assembly.
3. Remove the eight nuts from the door gasket mounting
plate on the inside of the inner door assembly.
4. Remove the door gasket mounting plate and the door
gasket.
5. Install the new door gasket (see Figure 7-2 for part
number) to the mounting plate.
6. Reassemble the mounting plate with gasket to the
inside of the inner door assembly using the eight nuts.
6-1
Page 23
SECTION 6 MAINTENANCE
7. Reassemble the inner door assembly using the six
screws on the outside of the door.
NOTE:
Remember that the lip on the door gasket mounting plate
must fit into the channel on the inside edge of the gasket
to insure a proper seal.
Procedure—To Adjust Gasket to Unit:
To prevent steam leaks around the door, adjust the gasket
tension to cavity. Adjust the gasket by loosening the six
screws on top and bottom of door, move inner door plate
in or out, left side or right side, and tighten the six screws.
6.3.4 Exterior Panel Removal
WARNING
To prevent hazard in servicing the cooker, be certain that
the steam supply boiler is shut down, the cold water shutoff valve is closed, and the electrical disconnect circuit
breaker for the cooker/boiler unit is off before removing
side panels.
Access to all internal plumbing and electrical assemblies is
from the right side and right front. The left-side panel is
removed by removing the bottom screw and pushing up on
the panel until the lower lip disengages the frame. The
panel is shown as item #25 in Figure 7-1. The electric
control panel, shown in Figure 7-3, may also be removed
as a unit by removing screws and pulling the panel
forward. Removal of the control panel is completed by
unplugging interconnecting wiring at the pin housing.
6.3.5 Steam & Water Solenoid Valve
Replacement
Replacements for the 1/2-inch steam solenoid valves and
the 1/4-inch water valves are available as complete units
from Market Forge Authorized Service Agencies. It is
necessary to replace an entire steam valve when the coil
is faulty or the diaphragm ruptures. Replacement coils are
available for the water valves. The valves are accessed as
explained in Subsection 6.3.4.
6-2
Page 24
7.1 General
SECTION 7 ILLUSTRATED PARTS LIST
This section contains a complete listing of all replaceable
parts of the ST-12. For the purpose of parts identification,
the unit is broken down into functional assemblies, and
each assembly is shown in an exploded view that is keyed
to the accompanying parts list. Each parts list contains the
figure index number, the Market Forge part number, and
an abbreviated description.
7.2 Ordering Information
Orders for repair parts should be directed to the nearest
authorized parts distributor. For a current Market Forge
Authorized Parts Distributor List, contact:
Product Service Department
Market Forge Industries Inc.
35 Garvey Street
Everett, Massachusetts 02149
Telephone: (617) 387-4100
All orders should contain the Market forge part number(s),
the part description(s), and the model and serial number of
the cooker for which the part or parts are ordered.
7.3 Index of Illustrated Parts List
Figure Part Page
7-1 Cabinet Assembly ...................................................7-2
7-2 Door Assembly ........................................................7-3
7-3 Control Panel Assembly ..........................................7-4
7-4 Condensor Assembly ..............................................7-5
7-1
Page 25
SECTION 7 ILLUSTRATED PARTS LIST
ITEM PART
NO. NO. DESCRIPTION QTY.
1 08-6308 REED SWITCH 1
2 98-1691 ASSY, PLUMBING DRAIN 1
3 98-1709 POST, REAR 2
4 08-4912 COUPLER, 1/2"NPT X 5/8"ID BARB 2
5 10-2793 ELBOW, 90, 1/2" IPS 2
6 08-6538 CHECK VALVE 3/8 OD BLACK 1
7 91-6491 GROMMET, SILICONE, RED 1
8 91-7318 WELD ASSY, TOP 1
9 10-9174 RELAY, TUBE 2
10 10-9175 RELAY, BASE 2
11 91-6940 BRACKET, RELAY 1
12 91-6475 HINGE, ASSY TOP 1
13 91-6476 HINGE, ASSY BOTTOM 1
14 91-7334 TROUGH, DRIP, ST-12/ST-24 1
15 91-7385 ASSY, DOOR, ST-12/ST-24 1
16 91-5621 ASSY, JET PIPE 2
17 91-6492 LATCH, DOOR 1
18 08-4600 SPRING, COMPRESSION 2
19 91-7684 STRAINER, CAVITY 1
20 98-1605 WELD ASSY, MIDDLE RACK 1
21 91-7699 RACK SIDE 2
22 10-4586 NUT, 1/2" IPS, S.S. W/TEFLON 3
23 10-8105 THERMOSTAT, SNAP DISC, PROBE TYPE 1
24 10-3343 NUT, BRASS, 1/2" IPS 1
25 10-1956 SCREW, TAPTIGHT, 8-32 X 3/8" 20
26 10-2571 NUT, LOCK, 8-32 17
27 08-1204 PLUG, HOLE WHITE 2
28 10-2184 SCREW, HEX HEAD, 10-32, 3/4" LG 4
29 98-1705 PANEL, SIDE 2
30 98-1708 PANEL, REAR 1
31 98-1632 INSULATION, FRONT 1
32
98-1631 INSULATION, REAR 1
33
08-7959 TUBING, NORPRENE 3/8" I.D. AS
MEASURED
34
08-7960 TUBING, NORPRENE 5/8" I.D. AS
MEASURED
35
98-1712
MECHANICAL CNTRL PANEL
1
36
~NPN~
DIGITIAL CNTRL PANEL
1
37
08-2702
BUSHING, DOOR, WHITE
2
38
91-7690
BRACKET, REED SWITCH
1
7-2
Page 26
SECTION 7 ILLUSTRATED PARTS LIST
Figure 7-1 Cabinet Assembly
7-3
Page 27
SECTION 7 ILLUSTRATED PARTS LIST
ITEM PART
NO. NO. DESCRIPTION QTY.
1 91-7386 OUTER DOOR 1
2 91-7387 INNER DOOR 1
3 91-7388 GASKET RETAINING PLATE 1
4 91-7389 DOOR GASKET 1
5 91-5745 DOOR HANDLE 1
6 09-1608 STRIKER 1
7 08-5027 MAGNET 1
8 91-5901 MAGNET BRACKET 1
9 08-4600 COMPRESSION SPRING 2
Figure 7-2 Door Assembly
7-4
Page 28
SECTION 7 ILLUSTRATED PARTS LIST
ITEM PART
NO. NO. DESCRIPTION QTY.
1 98-1706 CONTROL PANEL 1
2 98-1698 ARTWORK, CONTROL PANEL 1
3 08-6464 60 MIN. TIMER 2
4 08-6541 TERMINAL STRIP 2
5 91-6471 BRACKET, TERMINAL STRIP 2
6 10-7395 BUZZER 2
7 08-3826 KNOB, TIMER 2
8 10-5052 LIGHT, RED 2
Figure 7-3 Control Panel Assembly
7-5
Page 29
SECTION 7 ILLUSTRATED PARTS LIST
ITEM PART
NO. NO. DESCRIPTION QTY.
1 10-5859 VALVE, STEAM SOLENOID 1
2 08-4892 COUPLER, BRS 3/8ODX1/2THRD NPT 2
3 10-2885 UNION, FEMALE 1/2 IPS 1
4 10-2849 NIPPLE, CLOSE 1/2" NPT BRS 2
5 98-1477 COUPLERBRS,BARB 3/8"X3/8" NPT 1
6 08-6581 TEE, MALE 1/2" NPTX FEML 1/2" BRANCH 1
7 10-3739 1/2"X 3/8 REDUCING BUSHING 1
8 98-1630 WELDMENT, COLDH20/STEAM VALVE 1
9 10-1055 TEE, 3/8" ALL AROUND 1
10 10-3644 PLUG, SQ HEAD 3/8"IPS BRASS 1
11 08-7525 NIPPLE, CLOSE 3/8" NPT BRASS 2
12 08-6498 VALVE, 3/8" NPT, COLDW COND 1
13 08-4912 COUPLER, BARB 5/8"ODX1/2" IPS 1
14 08-7962 COUPLER, BARB 5/8"ODX3/8"THD 1
15 98-1477 COUPLER, BRS BRARB,3/8"X3/8" THD NPT 1
Figure 7-4 Condenser Assembly
7-6
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