SERVICE MANUAL
VSX BOILER BASE SERIES
CONVECTION STEAMERS
(GAS, ELECTRIC, DIRECT AND REGENERATED)
VSX24D ML-52827
VSX24E ML-52164
VSX24G ML-52163
VSX36D ML-52830
VSX36E ML-52829
VSX36G ML-52360
VSX36R ML-52831
VSX42DT ML-52834
VSX42ET ML-52833
VSX42GT ML-52376
VSX42RT ML-52835
- NOTICE -
This Manual is prepared for the use of trained Vulcan Service
Technicians and should not be used by those not properly
qualified.
This manual is not intended to be all encompassing. If you have
not attended a Vulcan Service School for this product, you should
read, in its entirety, the repair procedure you wish to perform to
determine if you have the necessary tools, instruments and skills
required to perform the procedure. Procedures for which you do
not have the necessary tools, instruments and skills should be
performed by a trained Vulcan Service Technician.
The reproduction, transfer, sale or other use of this Manual,
without the express written consent of Vulcan, is prohibited.
This manual has been provided to you by ITW Food Equipment
Group LLC ("ITW FEG") without charge and remains the property
of ITW FEG, and by accepting this manual you agree that you will
return it to ITW FEG promptly upon its request for such return at
any time in the future.
A product of Vulcan-Hart 3600 North Point Blvd Baltimore, MD 21222
F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS
TABLE OF CONTENTS
GENERAL .................................................................................................. 4
INTRODUCTION ....................................................................................... 4
SPECIFICATIONS ...................................................................................... 4
TOOLS ................................................................................................. 6
WATER CONDITIONING ............................................................................... 6
STEAMER OPERATION .................................................................................... 7
CABINET BASE BOILERS .............................................................................. 7
BOILER BLOWDOWN AND STEAMER SHUT OFF ..................................................... 8
COOKING COMPARTMENT CONTROLS ............................................................... 9
COMPONENT FUNCTION AND LOCATION ............................................................... 10
CABINET BASE BOILER CONTROLS ................................................................. 10
COOKING COMPARTMENT CONTROLS ............................................................. 13
SERVICE PROCEDURES ................................................................................. 14
CABINET BASES ..................................................................................... 14
BOILER INSPECTION / CLEANING ............................................................... 14
WATER LEVEL CONTROLS ...................................................................... 15
WATER LEVEL GAUGE ASSEMBLY .............................................................. 16
PRESSURE SWITCHES .......................................................................... 16
HIGH LIMIT THERMOSTAT ....................................................................... 17
BOILER ASSEMBLY REMOVAL / REPLACEMENT ................................................ 17
FILL AND COLD WATER SOLENOID VALVES .................................................... 18
WATER NOT BEING SUPPLIED TO BOILER ...................................................... 18
BLOWDOWN SOLENOID VALVE DOES NOT DRAIN .............................................. 19
SLOW PRESSURE BUILD UP ..................................................................... 19
STRAINERS ...................................................................................... 20
HEAT - GAS MODELS ............................................................................ 21
MANIFOLD PRESSURE ADJUSTMENT ........................................................... 24
HEAT - ELECTRIC MODELS ...................................................................... 24
HEAT - DIRECT STEAM MODELS ................................................................ 26
HEAT - REGENERATED STEAM MODELS (STEAM COIL) ........................................ 26
COOKING COMPARTMENT .......................................................................... 27
CONTROLS ....................................................................................... 27
STEAM SUPPLY SOLENOID ...................................................................... 27
WATER ACCUMULATING IN COMPARTMENT .................................................... 28
COOKING CYCLE CANNOT BE ACTIVATED ...................................................... 28
INTAKE SHUT-OFF VALVE ADJUSTMENT ........................................................ 28
DOOR ASSEMBLY ................................................................................ 28
ELECTRICAL OPERATION ................................................................................ 32
WATER LEVEL CONTROLS .......................................................................... 32
SOLID STATE - LOW LEVEL CUT OFF AND DIFFERENTIAL CONTROL .......................... 32
SOLID STATE AUXILIARY LOW LEVEL CUT OFF ................................................. 32
ELECTRO MECHANICAL - LOW LEVEL CUT OFF AND DIFFERENTIAL CONTROL ............... 33
ELECTRO MECHANICAL - AUXILIARY LOW LEVEL CUT OFF .................................... 34
SEQUENCE OF OPERATIONS ........................................................................ 35
GAS MODELS .................................................................................... 35
COOK CYCLE .................................................................................... 37
WATER REFILL (AFTER INITIAL FILL) ............................................................ 38
BOILER BLOWDOWN / DRAIN .................................................................... 38
ELECTRIC MODELS .............................................................................. 38
COOK CYCLE .................................................................................... 40
WATER REFILL (AFTER INITIAL FILL) ............................................................ 40
BOILER BLOWDOWN / DRAIN .................................................................... 41
SCHEMATICS, GAS STEAMERS, BOILER CONTROLS VSX24G, 36G AND 42GT ..................... 42
F24627 (0916) Page 2 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS
WIRING DIAGRAMS, GAS STEAMERS, BOILER CONTROLS VSX24G, 36G AND 42GT ............... 47
SCHEMATICS, ELECTRIC STEAMERS, BOILER CONTROLS VSX24E, 36E AND 42ET ................ 55
WIRING DIAGRAMS, ELECTRIC STEAMERS, BOILER CONTROLS VSX24E, 36E AND 42ET ......... 59
WIRING DIAGRAMS, ELECTRIC HEATER CIRCUITS VSX24E, 36E AND 42ET ........................ 71
SCHEMATIC, DIRECT STEAMERS, CABINET BASE VSX24D, 36D AND 42DT ........................ 73
WIRING DIAGRAM, DIRECT STEAMERS, CABINET BASE VSX24D, 36D AND 42DT .................. 74
WIRING DIAGRAMS, REGENERATED STEAMERS, BOILER CONTROLS VSX36R
AND 42RT (OLDER MODELS) .................................................................... 75
SCHEMATIC ALL MODELS - COMPARTMENT CONTROLS ........................................... 77
WIRING DIAGRAM, ALL MODELS - COMPARTMENT CONTROLS .................................... 78
TROUBLESHOOTING ..................................................................................... 79
ALL MODELS ......................................................................................... 79
© VULCAN 2016
Page 3 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - GENERAL
GENERAL
Introduction
GENERAL
This manual is applicable for all models listed on the
cover page. A convection steamer on a 42 inch base
with a tilting kettle is pictured below for reference.
Fig. 1
Steam Cooking
Pressure-less steamers offer an efficient way to
produce many foods in small portions or larger
batches. Pressure-less, convection steam cooking will
steam cook fresh foods or will steam defrost and cook
frozen foods providing the maximum color, flavor and
nutritional value with the least expenditure of energy
and labor. The pressure-less steaming compartment
allows the operator to open and close the door,
anytime during a cooking cycle. The steam supply will
shut off when the door is opened, then re-start when
the door is closed.
Cal-Code Construction Redundant controls in the
electrical safety circuits that, if tripped, must manually
be reset after the condition causing the trip subsides.
These controls consist of a dual function water level
cycling and low level cut off control, a single function
low water level cut-off control (Aux - LLCO), and a high
pressure relief switch in conjunction with a mechanical
pressure relief valve.
CSD-1 Construction Redundant controls in the
electrical safety circuits that, if tripped, must manually
be reset after the condition causing the trip subsides.
These controls consist of a dual function water level
cycling and low level cut off control, a single function
low water level cut-off control (LLCO), and a high
pressure relief switch in conjunction with a mechanical
pressure relief valve. Additionally, both circuits have
individual indicator lights that will illuminate for a visual
verification of the shutdown mode.
Cal-Code and CSD-1 construction both require
operator intervention in the event of a shutdown.
CSD-1 is more informative by using indicator lights to
show which safety system was shutdown.
Model Designations
NUMBER OF PANS PER
COMPARTMENT
2 4.0
3 2.5
6 1.0
Pan Size 12" x 20"
Boiler Code Descriptions
Vulcan-Hart incorporates redundant controls in
compliance with California Code (Cal-Code) and
CSD-1 as an option on steam equipment when
required by state and/or local building code
requirements. Descriptions of the codes are listed
below.
F24627 (0916) Page 4 of 82
DEPTH (INCHES)
Gas Steamers
Specifications
VSX BOILER BASE SERIES CONVECTION STEAMERS - GENERAL
Electric Steamers
AMPERAGE
MODEL TOTAL KW
VSX24E 24* 116 100 67 58 29 34
24* 67 58 29 34
36 100 878 44 50
VSX36E
42 117
48 116 58 67
24* 67 58 29 34
VSX42ET
36 100 87 44 50
*Standard
Steam Supply
Dry steam must be provided to the steamer. If the
steam is heavy with condensate, a ball float trap must
be used in the line and plumbed in before the pressure
Supply Pressure 15 psi (max.) 15 psi (max.)
Flow Rate 100 lb. per hour total (min.) 125 lb. per hour total (min.)
Pressure Reducing Valve Output 10 psi (furnished)
*Potable steam is not required for regenerated models but could be used.
Water Supply
Supply pressure should be 20-80 psig
In line strainer for supply line (Not Supplied)
1 PHASE 3 PHASE 3 PHASE - 4 WIRE
208V 240V 208V 240V 480V
reducing valve. To ensure rapid heat up of heavy cold
loads, the steam supply line must be sized to maintain
pressure as outlined below.
DIRECT STEAM STEAMERS
(POTABLE)
REGENERATED STEAM
STEAMERS (*NON-POTABLE)
set accordingly for good steam
generation but no higher than 15 psi.
(furnished)
220/380V and
240/415V
Page 5 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - GENERAL
Supply connection cold
Total dissolved solids (TDS)* less than 60 ppm
Total alkalinity less than 20 ppm
Silica less than 13 ppm
Chloride less than 30 ppm
PH factor 7 to 8
(*17.1 ppm = 1 grain of hardness)
Tools
Standard
• Standard set of hand tools.
• Volt-Ohm-Meter (VOM) with AC current tester.
(Any quality VOM with a sensitivity of at least
20,000 ohms per volt can be used.)
• Gas leak checking equipment.
• Gas pressure manometer.
Special
• CLR Treatment Kit - Used to remove Calcium/
Lime/Rust from a boiler (Contact Vulcan
Authorized Service Centers ).
• Adaptor to test thermocouple closed circuit
voltages (DC) on gas models with manual
ignition (purchase locally).
NOTE: Adaptors vary between manufacturers. An
example of one adaptor type is shown in Fig. 4.
the inside of the boiler, heating elements, thermostat
bulbs and water level probes. Because of the high
temperature of these surfaces, the precipitated
minerals bake onto them and become very difficult to
remove.
This causes several problems:
1. Reduce the heat transfer efficiency of the heating
system.
2. Cause premature failure of electric heaters.
3. Water level probes will give false readings.
4. Thermostat bulbs will sense temperature
incorrectly.
These problems are common to any manufacturer's
steamer regardless of design, but they can all be
prevented by furnishing the boiler with soft water.
Vulcan recommends the water contain less than
60ppm of “total dissolved solids” (TDS) and have a PH
factor between 7 to 8. These water properties can be
achieved by using a properly maintained water
softener.
Other chemical properties in water supplies can also
affect good steam generation and vary from within
each state and locality.
ionized water since it is "non conductive" and the
water level can not be detected.The water level
probes in the boiler use ions in the water to detect the
water level.
Fig. 4
Water Conditioning
Furnishing the boiler with soft water to reduce scale
formation is important. Scale formation will reduce
steam output, cause premature component failure,
and shorten equipment life. Most water supplies
contain scale producing minerals such as Calcium
and Magnesium. As steam is generated, the minerals
remain and dissolve into the water. As the
concentration of these minerals increases past a
certain point, they precipitate from the water and coat
F24627 (0916) Page 6 of 82
NOTE: The use of strainers, or filters will not remove
minerals from the water.
Vulcan recommends that a local water treatment
specialist be consulted before the installation of any
steam generating equipment.
Steamers that operate over a long period of time
without the benefit of a water softener, which have
developed a heavy scale build up, should be cleaned
before using a water softener.
CAUTION Do not use fully demineralized or de-
VSX BOILER BASE SERIES CONVECTION STEAMERS - STEAMER OPERATION
STEAMER OPERATION
The steamer and its parts are hot. Use care when operating, cleaning or servicing the steamer.
The cooking compartment contains live steam. Stay clear when opening each door.
Cabinet Base Boilers
Ensure that all utility connections to the steamer have
been made and are turned on.
On models that are Cal-Code/CSD-1 equipped,
amber colored lights for Hi pressure and low water
level will illuminate and stay on until the boiler is full
and the manual reset switch pressed.
Gas Powered Steam Boiler
1. Open the cabinet door and turn main power
switch ON.
• The red light will illuminate.
• Water will begin filling the boiler.
• The blowdown solenoid valve will close.
2. The boiler should fill in four to eleven minutes.
NOTE: Both valves on gauge glass assembly must
be open to fill the gauge.
NOTE: On older models equipped with a manual
“ball” type blowdown valve, the valve must be closed
for the boiler to fill.
3. Observe water level gauge glass:
• Verify that water is in boiler.
• Gauge glass is about half full.
4. The cycling pressure switch will maintain the
proper steam pressure in the boiler by cycling the
heating system on and off to generate steam
pressure.
NOTE: The knob on the gas combination control
valve has three positions (On-Pilot-Off) for control of
main burners and pilot.
5. Manual Ignition Models
A. Turn knob on gas combination valve to
PILOT then depress and light pilot burner
with a lit taper.
B. Maintain knob in depressed position for
about 30 seconds and release. Observe that
pilot burner flame stays on. If the flame
should go out, wait 5 minutes before
relighting.
C. Turn knob on gas combination control valve
to ON. If the water level in the boiler has
reached the minimum level, burners will
ignite and begin to heat the water in the
boiler.
D. After approximately 15 minutes, steam
should be present for cooking product.
Observe that the boiler pressure gauge
indicates steam pressure of 8-10 psi.
CAUTION Do not attempt to manually light the pilot
in an automatic-type ignition system.
NOTE: The knob on the gas combination control
valve has two positions (On-Off) for control of main
burners and pilot.
6. Automatic Ignition Models
• For the automatic ignition system to work,
the knob must be set in the ON position or
gas for the pilot and main burners will not
flow.
• The ignition control module ON/OFF/
RESET switch must be in the ON position to
operate. This switch is located on the upper
left side of the electrical control box for the
ignition control module.
• A red light will illuminate when the switch is
in the ON position.
A. After the main power switch is turned ON
and the ignition control modules RESET
switch is in the ON position, sparking will
begin three seconds later to light the
standing pilot.
NOTE: If a pilot flame is not established immediately,
sparking will continue for 90 seconds. After that
duration, the ignition control module will lock out and
needs to be reset to start the pilot and burner lighting
cycle again.
B. If the pilot lights, a signal is sent back
through the ignition cable indicating the
presence of pilot flame and sparking stops.
C. If the water level in the boiler has reached
the minimum level, the burners will ignite
and begin to heat the water in the boiler.
Page 7 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - STEAMER OPERATION
D. After approximately 15 minutes, steam
should be present for cooking product.
Observe that the boiler pressure gauge
indicates steam pressure of 8-10 psi.
Electrically Powered Steam Boiler
1. Open the cabinet door and turn main power
switch ON.
2. The red light will illuminate, water will begin filling
the boiler and the blowdown solenoid valve will
close.
• The boiler should fill in 4 to11 minutes.
3. Observe water level gauge glass:
• Verify that water is in boiler.
• Gauge glass is about half full.
NOTE: Both valves on gauge glass assembly must
be open to fill the gauge.
NOTE: On older models equipped with a manual
“ball” type blowdown valve, the valve must be closed
for the boiler to fill.
4. If the water level in the boiler has reached the
minimum level:
NOTE: On older models equipped with a manual
“ball” type blowdown valve, the valve must be closed
for the boiler to fill.
• Water will begin filling the boiler.
• The blowdown solenoid valve will close.
2. The boiler should fill in approximately 15 minutes.
NOTE: Both valves on the gauge glass assembly
must be open to fill the gauge.
3. Observe water level gauge glass:
• Verify that water is in boiler.
• Gauge glass is about half full.
4. When the water reaches the minimum level, the
steam solenoid valve will open, allowing steam to
enter the steam coil in the heat exchanger tank
and begin heating the water.
5. After approximately 20 minutes, a sufficient
amount of pressurized steam should be present
for cooking product.
Boiler Blowdown and Steamer Shut
Off
• The magnetic contactors will close.
• The heaters will energize and begin to heat
the water in the boiler.
A. Observe that the boiler pressure gauge
indicates steam pressure of 11-13 psi.
B. After approximately 15 minutes, steam
should be present for cooking product.
Direct Steam Powered Cooker
1. Open the cabinet door and turn main power
switch ON.
• The red light on the switch will illuminate.
2. If steam pressure is above the minimum setting
on the cooking compartment pressure switch:
• The pressure switch will close.
• The ready light will come ON.
• Power is supplied to other controls.
3. Observe that the steam pressure gauge in the
cabinet base indicates 10-12 psi.
4. Steamer is ready to cook product.
Regenerated Steam Powered Boiler
1. Open the cabinet door and turn main power
switch ON.
• The pilot light will illuminate.
F24627 (0916) Page 8 of 82
Turn the steamer off at least once daily and blow down
the boiler to remove sediments, scalants and lime
build-up in the boiler. Always blowdown the boiler
when it is under maximum pressure and no steam is
being used.
1. Automatic Blowdown (Newer Models)
2. Automatic Blowdown (Older Models)
A. Open the cabinet door and turn main power
switch OFF.
• The red light will go out.
• The blowdown/drain solenoid valve will
de-energize.
• The boiler will begin to drain.
B. The cold water condenser solenoid will
continue to operate, as needed, to
condense steam and to cool the water going
into the drain.
A. Turn power switch OFF.
B. Depress blowdown timer button.
• Blowdown timer will operate for 4
minutes.
C. At the end of blowdown, turn fill switch to ON
and allow boiler to fill.
VSX BOILER BASE SERIES CONVECTION STEAMERS - STEAMER OPERATION
3. Manual Blowdown (All Models)
A. Turn power switch OFF.
B. Open blowdown valve located on the bottom
front of the cabinet base.
C. After the boiler has completely drained,
close blowdown valve and turn fill switch to
ON and allow boiler to fill.
Cooking Compartment Controls
NOTE: If a cooking timer is set immediately after the
ready light comes on, a loud clanking sound will be
heard (oil canning) and the ready lights will flash for
several seconds. This condition is caused by the
manifold pressure being on the “fringe” of the pressure
switch set point. When a cook timer is set, the
compartment steam solenoid valve opens causing the
manifold steam pressure to drop, slightly below the
pressure switch set point. At the same time, steam
pressure is still increasing in the boiler. This opposing
condition causes a pressure “bounce” to occur but
after the steam pressure passes approximately 4 psi
this condition subsides. Under normal steam cycling
pressures, this condition will not be seen.
NOTE: To silence buzzers, turn timer knobs to off
position.
5. When timer knobs reach "0"
• Buzzers will sound.
• Steam generation will stop.
• Cooking lights will go off.
• Ready lights will come on.
NOTE: On direct steam units, no steam cycling will
occur due to the regulated constant steam supplied
from the building. Steam will come on for cooking
when a cook timer is set and go off at the end of that
time.
6. During a cooking cycle, the heating system will
cycle on and off as necessary to maintain steam
pressure in the boiler.
7. Turn power switch off to remove power from the
steamer and the red light will go out.
8. Blowdown the boiler. See Boiler Blowdown and
Steamer Shut Off.
When the steam pressure in the cooking compartment
manifold reaches approximately 3 psi:
• The cooking compartment pressure switch
closes and supplies power to the other controls.
• The ready lights will illuminate.
After approximately one minute, the steam pressure
in the boiler will reach the upper limit of 10 psi. If the
pressure drops below approximately 3 psi, the
pressure switch will open, removing power from the
cooking compartment controls.
1. With both timer knobs at the off position, open the
compartment doors and observe that no steam
has entered the cooking compartments, then
close the doors.
2. Set both timer knobs at 2 minutes. The ready
lights will go off, the cooking lights will come on,
and steam will begin to enter the compartments.
3. After one minute, open each door and observe
that steam has ceased to enter each
compartment, cooking lights go back to ready,
and one minute is remaining on each cook timer.
4. Close doors and steam generation and cook
timing will resume. Observe the floor drain to
ensure that live steam from compartments is
being cooled by cold water from the cold water
condenser solenoid valve.
Page 9 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - COMPONENT FUNCTION AND LOCATION
COMPONENT FUNCTION AND LOCATION
The steamer and its parts are hot. Use care when operating, cleaning or servicing the steamer.
The cooking compartment contains live steam. Stay clear when opening each door.
The steamer and its parts are hot. Use care when operating, cleaning or servicing the steamer.
The cooking compartment contains live steam. Stay clear when opening each door.
Cabinet Base Boiler Controls
For detailed information about the cabinet base boiler components and controls, refer to Fig. 5, Fig. 6, and the
paragraphs below.
Fig. 5
F24627 (0916) Page 10 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - COMPONENT FUNCTION AND LOCATION
Water Level Gauge Assembly. The gauge permits
visual confirmation that water level is being
maintained in the boiler during operation.
• The correct water level is one-half the height of
the glass.
• The manual valves at the top and bottom of this
assembly must be fully open. Only close a valve
if the glass tube is damaged.
NOTE: The appearance of extreme murkiness in the
water indicates inadequate water quality and will
Page 11 of 82 F24627 (0916)
Fig. 6
cause failure of controls and the steamer. Warranty
does not cover malfunction due to poor water
conditions. Blowdown and/or clean out the boiler as
outlined in Boiler Blowdown and Steamer Shut Off.
• The water should be clean and clear.
Water Level Control and Level Sensing Probes.
The probes monitor the water level in the boiler.
• They determine if sufficent water is present or
more water is required.
VSX BOILER BASE SERIES CONVECTION STEAMERS - COMPONENT FUNCTION AND LOCATION
• They will shut off the heat source to the boiler if
the water level drops too low.
NOTE: Controls may not function and serious
clogging will occur if a daily blowdown procedure is
not followed.
The water level control works by using three different
probe lengths to monitor the water level. The probes
are:
• High Level (HL)
• Low Level (LL)
• Low Level Cut Off (LLCO)
The level sensing probes may easily be removed to
inspect for lime build up. As a rule, the condition of
these devices will indicate the overall water condition
of the boiler. Clean the probes if needed.
Boiler Fill Solenoid Valve. The valve admits water to
the boiler when demanded by the water level control
to maintain the correct water level in the boiler.
Cold Water Condenser Solenoid Valve. The valve
allows cold water flow into the boiler blowdown drain
box to condense steam and cool the hot water before
its discharge into the drain.
Cycling Pressure Switch. The switch controls boiler
pressure between prescribed limits by turning the heat
source on and off.
unwanted particles out of the system. A "Y" strainer
should be inserted upstream of the fill solenoid valve.
Power Switch. When the switch is turned ON, power
is supplied to the controls and the steam generating
process is started in the boiler. The power switch is
located on the front of the boiler control box.
Water Inlet Valve. The valve is used to stop water flow
to the steamer when the steamer is being serviced.
This valve should remain open during normal
operation.
• Newer models will have a small Petcock type
valve.
• Older models will be a “ball” type valve.
High Limit Thermostat. This is a protective device
that shuts off the heat source if the boiler temperature
exceeds a specified limit. All standard models are
equipped with a surface high limit thermostat.
Descaler. The descaler hangs submerged in water
inside the boiler and is used to help control boiler
surface scaling. Two descalers are used in each
boiler.
Handhole Cover Assembly. This cover, when
unbolted and removed, allows internal examination /
cleaning of boiler shell and its components.See
BOILER INSPECTION / CLEANING for additional
information.
High Limit Pressure Switch. The switch is physically
identical to the cycling pressure switch but is used as
a high limit. The pressure settings are at higher and
lower limits than the cycling pressure switch in order
to turn off the heat source before the boiler pressure
reaches its limit and automatically resets after the
pressure drops below the lower limit set point.
Blowdown/Drain Solenoid Valve. The valve is
plumbed into the drain pipe of the boiler.
• Newer steamer models will automatically
blowdown when power is turned off by using a
normally open solenoid valve.
• Older models can have a solenoid valve that is
activated by depressing a separate blowdown
timer button or have a manual “ball” type valve.
Daily boiler blowdown is essential to proper operation
and component life by removing sediment and
scalants that may be lodged in the chamber of the
boiler.
NOTE: On models using a direct steam supply, a
strainer is used in the pressure regulating valve.
Strainers. A strainer is used in the water inlet line to
prevent foreign matter from becoming lodged in the fill
or cold water condenser solenoid valves and to keep
F24627 (0916) Page 12 of 82
Pressure Gauge. This gauge indicates boiler steam
pressure. Normal operating pressures are listed
below.
Steamer Type PSI
Gas 8-10
Electric 11-13
Direct 10-12
Regenerated 10-12
Drain. This component drains steam condensate and
water from cooking compartments and boiler.
Check Valve. On models with the delime piping
assembly option, the check valve prevents the
ejection of hot water and steam out of the delime
funnel if the manual delime fill valve were to be
opened.
Delime Port Assembly. On models with the delime
piping assembly option, this assemly allows the boiler
and other internal components to easily be delimed to
remove calcium, lime and rust build up. See BOILER
INSPECTION / CLEANING for additional information.
Standing Pilot (Gas Boilers). The pilot should
always remain lit to light the main burners upon a call
VSX BOILER BASE SERIES CONVECTION STEAMERS - COMPONENT FUNCTION AND LOCATION
for heat unless the steamer will not be in use for an
extended period. If the pilot flame goes out, wait 5
minutes before relighting.
Main Burners (Gas Boilers). The main burners heat
the water in the boiler to generate steam.
Combination Control Valve (Gas Boilers). This gas
solenoid valve opens to allow gas flow when a call for
heat is made and also regulates the manifold gas
pressure.
Pressure Regulating Valve (Direct & Regenerated
Steam). This valve regulates the manifold steam
pressure between 10-12 psi.
Magnetic Contactor (Electric Boilers). This
contactor, when energized, supplies power to the
electric heating elements.
Heating Elements (Electric Boilers). These heat the
water in the boiler to generate steam.
Cooking Compartment Controls
The upper section of the steamer consists of two
separate cooking compartments. Each compartment
functions independently with its own set of controls.
Power is supplied to the controls only after the steam
pressure rises above 3 psi to close the compartment
pressure switch. The switch remains closed as long
as steam pressure stays above 3 psi but will open if
the pressure drops below that setting.
Buzzer (Fig. 8). This signals end of a cook cycle, must
be turned off manually.
Door Switch. The door switch removes electrical
power to the timer.
Steam Solenoid Valve. This valve, when energized,
opens to allow steam into the cooking compartment
(normally closed valve).
Compartment Pressure Switch. This switch
supplies power to the controls only after the steam
pressure rises above 2.3 psi to close the compartment
pressure switch. The switch remains closed as long
as steam pressure stays above 2.3 psi but will open if
the pressure drops below that setting.
Manifold Pressure Gauge. This gauge indicates the
amount of steam pressure in manifold. The intake
shut-off valve should be adjusted so manifold
pressure remains at 9 psi with both compartments on.
Intake Shut-Off Valve.This valve is the main steam
supply shut-off from the boiler to the steam supply
manifold. This valve should NOT be left fully OPEN to
boiler steam supply. See INTAKE SHUT-OFF VALVE
ADJUSTMENT for additional information.
Ready Light (Green) (Fig. 7). When lit, indicates
steamer is ready to cook.
Cooking Light (Red). When lit, indicates steamer is
in a cooking cycle.
Cooking Timer. Used to set desired cooking cycle
time between 0-60 minutes. When a timer is set, the
steam supply solenoid valve is energized to allow
steam into the cooking compartment but only after the
boiler has reached its operating pressure. Also,
energizes the buzzer when time expires.
Fig. 7
Fig. 8
Page 13 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
SERVICE PROCEDURES
Cabinet Bases
Certain procedures in this section
require electrical test or measurements while power is
applied to the machine. Exercise extreme caution at
all times. If test points are not easily accessible,
disconnect power and follow lockout / tagout
procedures, attach test equipment and reapply power
to the test.
BOILER INSPECTION / CLEANING
CAUTION To ensure proper steamer operation,
periodic service must be performed as outlined in
these procedures.
It is recommended that the boiler be thoroughly
inspected for excessive scale and lime build up on a
quarterly basis. In hard water areas or for units heavily
used, a more frequent interval should be used. This
inspection consists of an internal examination and
cleaning of the boiler shell, an examination and
possible replacement of the descaler, a check of lime
build up on the water level sensing probes, and a
check of all boiler controls, including the pressure
switches.
Read and follow the instructions on
the CLR bottle. Use plastic or rubber gloves to avoid
skin contact. If CLR liquid comes in contact with the
skin, rinse with clean water.
Clean-Out (All Boiler Models)
1. Turn steamer OFF and drain boiler.
2. Remove hand hole plate and gasket (top front)
from the boiler by removing the nut and clamp,
then tapping the cover lightly to free it while
holding the cover stud. This prevents the cover
from dropping into boiler.
NOTE: Boiler water capacities vary between seven to
nine gallons for both gas and electric models
depending on the boiler size and BTU/KW rating.
NOTE: If deliming solution accidently comes in
contact with steamer components, lightly rinse off with
clean water.
8. Mix the deliming solution according to the
instructions for the chemical in use then add
solution to boiler as follows.
• Models with Blowdown Timer. Mix the
solution in accordance with the instructions
on its container. Pour deliming solution into
boiler shell. Proceed to Step 9.
• Models without Blowdown Timer. Turn off
the incoming water supply. Turn the unit ON
to close the drain valve. Mix the solution in
accordance with the instructions on its
container. Pour deliming solution into boiler
shell. Proceed to Step 9.
• Models with Deliming Port Assembly.
Before mixing and pouring deliming solution
into boiler, clean the seating surfaces for the
hand hole gasket and then install a new
gasket. Position the hand hole plate and
tighten down. Turn off the incoming water
supply. Turn the unit ON to close the drain
valve. Mix the solution in accordance with
the instructions on its container. Open the
deliming assembly valve and pour the
deliming solution into the port (Fig. 9). Close
the deliming assembly valve and proceed to
Step 10.
3. Remove old descaler retaining springs if present.
4. With a wire brush, or equivalent, dislodge and
remove all loose scale from boiler shell. The
loose material must be either scooped from the
boiler or flushed through the drain.
5. Check probe canister and float valve assembly
(regenerated models) for a scale build up and
clean as necessary.
6. Check drain hole for obstructions.
7. Install two new descalers.
F24627 (0916) Page 14 of 82
Fig. 9
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
9. Clean the seating surfaces for the hand hole
gasket and then install a new gasket. Position
and tighten the hand hole plate.
10. Cooking compartment timers are to be in the OFF
position. Turn the boiler switch ON and open
water valve if necessary.
11. Allow boiler to operate under pressure for 90
minutes or per the instructions for the chemical
in use.
12. Drain boiler by normal methods. Refill boiler and
allow heat until fully pressurized.
13. Repeat Step 12 three times.
14. The steamer is now ready for normal operation.
Deliming Only (Models with Deliming Port
Assembly)
NOTE: Boiler deliming should be performed on a
weekly, bi-weekly or monthly basis, depending on the
quality of the local water supply.
On steamers using a water purification system, follow
the instructions for that system to delime the boiler.
Only use the type of chemical recommended or
described in the instructions for deliming with this type
of system.
1. Turn steamer OFF and drain boiler.
2. Mix the deliming solution according to the
instructions for the chemical in use then add
solution to boiler.
NOTE: Boiler water capacities vary between seven to
nine gallons for both gas and electric models
depending on the boiler size and BTU/KW rating.
NOTE: If deliming solution accidently comes in
contact with steamer components, lightly rinse off with
clean water.
• Models with Blowdown Timer. Mix the
solution in accordance with the instructions
on its container. Open the deliming
assembly valve and pour the deliming
solution into the port. Close the deliming
assembly valve and proceed to Step 3.
• Models without Blowdown Timer. Turn off
the incoming water supply. Turn the unit ON
to close the drain valve. Mix the solution in
accordance with the instructions on its
container. Open the deliming assembly
valve and pour the deliming solution into the
port. Close the deliming assembly valve and
proceed to Step 3.
3. Top compartments are to be in the OFF position.
Turn the boiler switch ON and open water valve
if necessary.
4. Allow boiler to operate under pressure for 90
minutes or per the instructions for the chemical
in use.
5. Drain boiler by normal methods. Refill boiler and
allow to heat up and build steam pressure.
6. Repeat Step 5 three times.
7. Unit is now ready for normal operation.
Descaler
NOTE: The descaler is accessible through the hand
hole opening. It is a coiled wire wound around a solid
cylindrical core. It hangs by an open loop from the
shell's horizontal stay rod, about 4 inches from the
front of the shell.
If the wire is eaten through, or if the core of the
descaler is eaten away to half its original size, a new
descaler should be installed.
CAUTION The descaler must not contact the
bottom of the boiler shell, electric heating elements, or
the regenerating steam coils on units so equipped.
To install a new descaler, stretch its wire coil so that
the descaler hangs with its core completely below the
minimum water level in the boiler, but hanging free.
WATER LEVEL CONTROLS
The steamer incorporates both low level cut-off and
differential controls. These controls can be either solid
state or electro-mechanical.
Solid State Controls
1. Ensure that water is filling the boiler.
2. Check for correct voltage being applied to the
board.
3. Verify the water level control board operation as
outlined in Water Level Controls and as follows:
A. The HL LED turns on and the HL relay
energizes to change the contact state at
power on.
B. As the boiler fills the LLCO LED turns on and
the LLCO relay energizes to change the
contact state after the water level reaches
the LLCO probe.
C. The HL LED turns off and the HL relay de-
energizes. This allows the contact state to
switch back to its starting condition after the
water level reaches the HL probe.
Page 15 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
NOTE: If water is in the boiler but is not being detected
by the water level probes, the probes may need
cleaned and/or boiler delimed.
4. After checking the above items, if the water level
control board does not appear to be functioning
as outlined, then:
A. Replace the water level control board.
B. Check unit for proper operation.
Electro Mechanical Controls
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
Loose electrical connections may prevent the heat
from coming on or may cause the boiler to overfill.
Accumulation of boiler scale on or near the sensing
probes may cause them to retain water on the
insulator surface. This may prevent the boiler from
filling or cause dry firing. Dry firing will result in damage
to heating elements or to the boiler. Verify the water
level controls operation as outlined in Water Level
Controls.
With the individual probe lead wire removed, check
the probes and contactors as outlined below:
1. With an ohmmeter, check the probe between the
wire connection and shell. An open circuit should
be present when the boiler is empty. If resistance
is present, remove and clean the probes. Also
check for a cracked insulator, then reinstall
probes and check. When the boiler is full of water,
a resistance reading should be measurable
between the probes and shell only.
NOTE: Actual resistance reading will depend on
water quality and probe condition.
2. Check low level and differential water level
controls. With the power switch ON, use a
voltmeter to check the input voltage across
terminals 1 and 2. Meter should read 115V. With
the boiler empty, across terminals 9 and 10,
meter should read 300 to 350V. If these voltages
are not present, the coil is bad and the contactor
should be replaced.
A. Remove the bolted cover over the sensor
cluster.
B. Disconnect the wire from the probe.
C. Use a wrench to unthread the probe.
CAUTION Do not use an abrasive on the insulator
or damage may occur.
4. Clean probe thoroughly with a soft cloth. Make
sure to remove ALL deposits from the insulator.
5. Inspect through the probe socket for the
presence of water. Water must drain from the
probe housing. If in doubt, pour water into the
housing and observe that it drains quickly. If the
housing fails to drain, remove the housing or
housing cover and clean the interior
mechanically.
WATER LEVEL GAUGE ASSEMBLY
1. Remove the water level gauge assembly glass
tube as follow:
A. Close the valves at the top and at the bottom
of the gauge assembly.
B. Unscrew the packing nuts at the top and
bottom of the glass tube.
C. Slide the glass tube upwards, until the
bottom of the tube is clear of the fitting.
D. Lift the glass tube out of the fitting.
2. Install the water level gauge assembly glass tube
as follow:
A. Place new sealing washers on both ends of
the glass tube.
B. Place the glass tube in the lower fitting and
slide up into the upper fitting.
CAUTION Do not over tighten the packing nuts; it
could break the gauge glass.
C. Tighten the packing nuts hand tight.
D. Open the valves at the top and at the bottom
of the gauge assembly.
PRESSURE SWITCHES
Gas and electric models incorporate pressure
switches to control steamer operation.
CAUTION Be careful to note the location of each
probe and the number of the wire connected to it.
Incorrectly connected wires will cause the controls to
malfunction.
3. Remove the sensing probe as follows:
NOTE: The pressure switch on the left is the cycling
or primary control; the one on the right is the high limit
F24627 (0916) Page 16 of 82
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
control. They are identical switches, differing only in
their settings.
1. Remove the boiler control box cover to access
the two pressure switches.
2. Turn the power ON and let the boiler come up to
pressure.
3. After the ready light comes ON, turn one of the
cooking compartment timers on to exhaust
steam from the boiler.
4. Observe boiler pressure gauge readings for
several cycles and compare them with the
pressure settings listed in the table below.
PRESSURE SETTING (PSI)
Unit
Gas 8 10 6 15
Electric 11 13 6 15
NOTE: Two slotted and square headed adjustment
screws extend through the top of the switch case with
dials and pointers to indicate the approximate setting.
The adjustment screw directly above the dial changes
both the cut-out (off) and the cut-in (on) points. Turning
the screw clockwise increases the pressure.
If the readings differ from the table values, adjust
the pressure settings as described below.
A. Set the cut-out adjustment screw for the
B. Set the cut-in adjustment screw for the
HIGH LIMIT THERMOSTAT
NOTE: On gas boilers, the high limit thermostat is
located behind a small metal cover on the face of the
boiler close to the sight glass on the right side.
NOTE: On electric boilers, the high limit thermostat is
located behind the contactor box cover. On electric
boilers with two heating elements, the thermostat is
connected to one of the heating element lugs. On
electric boilers with four heating elements, the
thermostat is located between the center pair of
elements at the top of the elements.
Inspect the high limit thermostat and mounting
surfaces as follows:
CYCLING HIGH LIMIT
ON OFF ON OFF
desired pressure.
desired pressure.
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
1. Remove thermostat (bi-metallic disk type) and
inspect flat surface of thermostat for corrosion or
rust.
• No rust or corrosion allowed. Replace the
thermostat if its base is rusted.
CAUTION To ensure proper operation, the
thermostat and associated mounting surfaces must
be cleaned one a year.
NOTE: A good metal-to-metal contact is essential for
proper functioning of the thermostat.
2. If required, clean thermostat and thermostat
mounting surfaces.
3. Reinstall the thermostat.
BOILER ASSEMBLY REMOVAL / REPLACEMENT
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
Shut off the gas before servicing the
unit.
All gas joints disturbed during
servicing must be checked for leaks. Check with a
soap and water solution (bubbles). Do not use an open
flame.
• Check all joints prior to the gas valve
(solenoid) before lighting the unit.
• Check all joints beyond the gas valve
(solenoid) after lighting the unit.
Newer Steamer Models
1. Remove the boiler as follows:
A. Check / ensure that all utilities to the
steamer are off.
B. Blow down the boiler and allow to cool, if
necessary.
C. Drain any excess water from the boiler.
D. Disconnect the steam supply line, power
leads and drain lines from the cooking
compartment top to the boiler base.
NOTE: The bolts are located behind the small
louvered access panels on the left and right side of the
steamer.
E. Remove the cooking compartment top by
unscrewing the bolts holding the cooking
compartment top to the boiler base.
Page 17 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
F. Lift the top off the boiler base and place to
the side.
G. Remove the remaining plumbing and
electrical connections from the boiler to the
controls.
2. Reverse the steps above to install the boiler.
Older Steamer Models
1. Remove the boiler as follows:
A. Check / ensure that all utilities to the
steamer are off.
B. Blow down the boiler and allow to cool, if
necessary.
C. Drain any excess water from the boiler.
D. Remove the screws holding any control box
that would obstruct removal of the boiler
through the front of the base.
E. Disconnect the 1/4 inch diameter water inlet
tubing.
F. Disconnect the wire and conduit from the
low water cut-off probes, high limit
thermostat, and the automatic blowdown
valve (if so equipped).
A. Remove the coil assembly from the valve
stem by lifting up on the retaining cap at the
top of the solenoid valve and sliding the
metal cover plate off.
B. Clamp the body of the valve in a vise.
C. Mark a scribe line on the stem nut to the
valve body for proper retightening.
D. Remove the stem locking nut to remove the
stem from the valve body.
3. Inspect the solenoid valve (Fig. 10) as follows:
• Check rubber seal on bottom of plunger.
• Check plunger spring.
• Check plunger spring.
• Check ports in valve body.
G. Uncouple the union on the steam outlet and
blow down the lines.
H. Remove all the screws holding the flue and
flue collector to the base.
I. Remove the anchor screws holding the
boiler to the frame.
CAUTION The burner box, anchored only by the
boiler, must be prevented from sliding forward with the
boiler.
J. Slide the boiler forward and set aside
2. Reverse the steps above to install the boiler.
FILL AND COLD WATER SOLENOID VALVES
1. Remove the solenoid valve as follows:
A. Turn off the water supply to the steamer.
B. Open the base doors and remove the two
screws from the top of the boiler control box.
C. Pull the quick connect power leads off the
solenoid valve being serviced.
NOTE: It is recommended that the valve be removed
from the unit for cleaning to prevent damage to the
lines and fittings when the stem is removed from the
body.
Fig. 10
4. Reverse Step 2 to reassemble the solenoid
valve.
5. Reverse Step 1 to reinstall the solenoid valve.
WATER NOT BEING SUPPLIED TO BOILER
1. Check that water is connected / supplied to
steamer.
2. Turn the steamer on.
3. If, after approximately 10 minutes, no water is
observed in the water level gauge sight glass,
check the following components:
• Water level control probes.
• Water solenoid valves.
Water Level Control Probe
NOTE: This condition indicates extremely poor water
quality being supplied to the boiler and/or boiler clean
out/and deliming has not been performed. Scalants
may be covering the water level control probe giving
a false indication of a sufficient water level in the
boiler.
2. Disassemble the solenoid valve as follows:
F24627 (0916) Page 18 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
1. Detach, remove, and thoroughly clean the water
level probe and canister assembly to remove
scalants and lime build up.
2. If cleaning does not resolve the problem, replace
the water level probes and canister assembly.
3. Perform a boiler clean-out and deliming
procedure. Refer to BOILER INSPECTION /
CLEANING for detailed instructions.
Water Solenoid Valve
NOTE: An open boiler blowdown solenoid valve as
will allow water to drain as quickly as it’s fed to the
boiler.
Check for the following:
• Loose / damaged wiring.
• Burned out coil.
• Dirty / damaged valve seat.
Newer Steamer Models
NOTE: Newer steamer models use a plunger type rod
that raises and lowers to permit steam/water flow out
of boiler.
1. Inspect the water orifice.
2. If required, clean the water orifice.
3. If valve still leaks:
A. Remove and disassemble the valve. Refer
to FILL AND COLD WATER SOLENOID
VALVES for detailed instructions.
B. Remove any debris found on the sealing
surfaces.
C. Reassemble and reinstall the valve.
4. Remove any debris found on the sealing
surfaces.
5. Reassemble and reinstall the valve.
6. If valve still malfunctions, replace it and recheck
for proper operation.
BLOWDOWN SOLENOID VALVE DOES NOT
DRAIN
The pressurized water contained in the boiler should
be blown through this valve and be noticeably visible
exhausting out the steamer drain.
NOTE: The automatic blowdown solenoid valve is not
present on all models.
Older Models.These steamers have a blowdown
timer button. When this button is pressed, the boiler
blowdown valve opens and pressure is released.
Newer Models.These steamers have a normally
open solenoid valve. When the main power switch is
turned ON, the valve energizes (closes) to allow
pressure to build up. When the main power switch is
turned OFF, the solenoid valve de-energizes and
pressure is released.
If the blowdown operation appears to function
sluggishly or not at all, considerable scalants may be
lodged in the drain pipe and/or the valve.
1. Disconnect the valve from the drain line.
2. Inspect both the valve and the drain pipe fixed to
the boiler.
If considerable scalants or lime build up is apparent,
both the valve and the boiler must be cleaned. Refer
to BOILER INSPECTION / CLEANING and FILL AND
COLD WATER SOLENOID VALVES for detailed
cleaning instructions.
D. If valve still malfunctions, replace it and
recheck for proper operation.
Older Steamer Models
NOTE: Older steamer models have a movable blade.
When closed, the blade reacts as a guillotine that
should be free to move fully down into the valve pocket
(projection at bottom of valve) so that the pierced hole
in the blade aligns perfectly with the body opening.
1. Remove the valve. Refer to FILL AND COLD
WATER SOLENOID VALVES for detailed
instructions.
2. Remove the two assembly bolts and separate the
brass valve body parts.
3. Remove the loose internal parts from the valve
body portion.
Page 19 of 82 F24627 (0916)
SLOW PRESSURE BUILD UP
If the boiler requires more than 15 minutes (20 minutes
for regenerated models) to achieve normal operating
pressure as listed in below, then check the conditions
listed in the table below.
Normal Operating Pressures
Unit Range (PSI)
Gas 8 - 10
Electric 11 - 13
Direct 10 - 12
Regenerated 10 - 12
All Models (With Boiler)
NOTE: A heavy build-up of scalants will hamper heat
transfer.
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
1. Unbolt and remove the hand hole cover plate and
gasket assembly.
2. Examine interior of boiler and if scalants and/or
lime build up is apparent, perform a boiler cleanout and deliming procedure.
Refer to BOILER INSPECTION / CLEANING for
detailed instructions.
3. If considerable scalants are evident, then both
the boiler blowdown solenoid valve and the water
level control must also be examined.
Gas Models
NOTE: Low incoming gas pressure causes reduced
BTU output.
1. Check incoming line and manifold gas pressures
as outlined in Manifold Pressure Adjustment.
2. If the pressures are acceptable, check for:
• Gas combination control valve malfunction.
If pressure adjustments are made and
manifold pressure remains low, replace the
combination valve and test unit for proper
operation.
NOTE: After a period of time, gas burners can
accumulate carbon in their ports or become clogged
by food and grease debris from kitchen cleaning,
restricting performance.
• Gas burner ports clogged or obstruction
around air shutter. To clean burners,
remove them from burner box and boil in
water for 10 -15 minutes to dislodge clog.
Clean-out any remaining debris from the
gas ports using a wire brush, scribe or pick
type metal instrument. Remove any other
foreign objects that appear to be obstructing
the gas ports or air shutters.
• One or more electric heating elements
malfunctioning.
• One or more magnetic contactors not activating
to power heating elements.
• If unit operates under three phase power, then
one of the phases might be lost.
Direct Steam Models
Check for the following:
• Low steam supply pressure.
• Cooking compartment steam solenoid valve
malfunction.
• Steam pressure regulator adjusted too low.
• Clogging in the steam line.
Regenerated Steam Models
Check for the following:
• Low steam supply pressure.
• Cooking compartment steam solenoid valve
malfunction.
• Heavy scale build up inside copper steam coil.
STRAINERS
Inlet Water Strainer
NOTE: The in-line Y strainer should be located
upstream of the fill valve solenoid.
1. Unscrew the cap from the Y-strainer leg pointing
toward the floor.
2. Remove the screen and any foreign particles
trapped in the opening.
3. Rinse the screen thoroughly to remove
accumulated debris and replace the screen in the
valve body.
NOTE: It is possible for debris to become lodged in
the small gas orifice opening over time.
• Gas orifice clogged or obstructed around air
shutter. Clean-out the gas orifice using a
round metal instrument of the same hole
diameter or slightly smaller. Clean as
needed. If clogging reappears, the orifice
should be removed, cleaned and
reinstalled. Remove any other foreign
objects that appear to be obstructing the gas
orifice or air shutters.
Electric Models
Check for the following:
• Heavy scale build up on heating element.
F24627 (0916) Page 20 of 82
4. If screen can not be thoroughly cleaned, replace
5. Reinstall the cap. Ensure that the Y-strainer is
Pressure Regulating Strainer
NOTE: The pressure regulating valve strainer will
become clogged if dirty steam lines are connected to
direct steam models.
1. Remove the hex nut on the bottom of the
2. Remove the strainer.
3. Clean the strainer and valve seat.
it with a new one.
positioned so the cap is pointing downward to
catch debris.
pressure regulating valve.
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
4. Install the pressure regulating valve cap. Tighten
it handtight.
HEAT - GAS MODELS
Pilot, Thermocouple, Gas Combination Control
Valve, Main Burners
When heated, the pilot thermocouple supplies a
millivolt signal (DC) to an internal solenoid valve on
the gas combination control valve. The solenoid valve
is designed to shut off the gas flow to the pilot and
main burners in case of a malfunction in the system.
When energized by the thermocouple voltage, the
valve is held in the open position to permit gas flow.
The pilot burner flame is controlled by an adjustable
needle valve located under a small cap screw on the
combination control valve.
When experiencing nuisance pilot outages, visually
check pilot flame (Fig. 11) for the proper contact on
thermocouple and the flame color. Also, check to see
that unusually strong floor drafts are not interfering
with proper heating of the thermocouple by the pilot
flame.
NOTE: If adjustments in gas or pilot pressure settings
are made, always replace the adjustment cover screw
to assure proper gas control operation.
The pilot flame should be a steady blue flame that
envelopes the thermocouple tip. The flame should be
about one inch long with half its length extending
beyond the outer edges of the pilot shield. If the pilot
flame does not appear to be this length and color, then
an adjustment is necessary. See Pilot, Thermocouple,
Gas Combination Control Valve, Main Burnersfor
examples of unsatisfactory pilot flames.
Fig. 11
NOTE: The pilot operates unregulated at gas supply
pressures while the pressure regulator in the
combination control valve regulates pressure to the
main burners only.
Turn clockwise to decrease pilot flame and
counterclockwise to increase.
If adjustment does not result in a pilot flame of proper
size, then gas might not be flowing properly to the
pilot. Check for:
• Plugged pilot orifice.
• Kinked or plugged pilot gas supply tube.
• Low gas supply pressure.
If these are acceptable, visually check:
• The thermocouple tip (hot end) and tube lead for
kinks and pinches.
• The thermocouple connector tip for corrosion,
tarnish and/or dirt.
If the pilot flame is correct and there are no drafts, then
the problem is in the thermocouple output voltage or
the gas solenoid valve in the combination control.
NOTE: If a meter is not available, replace the
thermocouple with a new one and recheck operation.
Page 21 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
Check the thermocouple output voltage (DC millivolts)
as follows:
1. Use a VOM and adapter to take a closed circuit
reading with the pilot on.
2. Take an open circuit reading as follows:
A. Disconnect the thermocouple tube from the
valve.
B. Connect the meter leads to the tube and
threaded end.
C. Manually press and hold down OFF/PILOT/
ON knob and light the pilot,
D. Allow the pilot to heat the thermocouple for
one to two minutes and compare the
readings with the table below.
Thermocouple Output (DC
Millivolts)
Closed Circuit Open Circuit
Typical 15 NA
Range 10 - 20 20 - 35
7. Check for proper operation.
Shut off the gas before servicing the
unit.
All gas joints disturbed during
servicing must be checked for leaks. Check with a
soap and water solution (bubbles). Do not use an open
flame.
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
CAUTION
serviceable and should not be disassembled. Do not
attempt to repair the gas combination control valve, it
must be replaced.
If, after replacing thermocouple, the pilot or main
burners are still not functioning properly, the gas
combination control valve should be replaced as
follows:
Gas combination control valves are not
NOTE: The connection of the tubing from the
thermocouple tip to the control valve is an electrical
connection and must be clean. Do not use any sealing
compound on the threads or over tighten the threaded
connection.
If either of the readings is less than the minimum or
thermocouple is not operating as described, replace
the thermocouple as follows:
1. Remove the pilot assembly by disconnecting
thermocouple and pilot gas supply tubing from
the combination control valve.
2. Remove the two screws holding the pilot
assembly to its bracket.
3. Replace the thermocouple or pilot assembly.
4. Use two screws to secure the pilot assembly to
the bracket.
CAUTION Over tightening the nut can crush the
insulator and short the thermocouple.
5. Finger tighten the thermocouple nut plus 1/4 turn
with a wrench.
All gas joints disturbed during
servicing must be checked for leaks. Check with a
soap and water solution (bubbles). Do not use an open
flame.
6. Connect the pilot gas supply tubing to the
combination control valve and tighten finger tight.
1. Remove the two screws and the control box
cover.
2. Disconnect electrical supply wires and conduit
running to the combination control valve.
3. Disconnect the thermocouple lead and pilot gas
supply tube from control and pipe connections on
each side of the control.
4. Reverse procedure to install the replacement
valve.
5. Check the unit for proper operation.
The main burners are lanced port steel burners (5 or
7 burners, depending on the unit) and have adjustable
air shutters. Fixed orifice type hoods are used to
establish the gas flow to each burner. Set each burner
air shutter opening just large enough to eliminate any
yellow tip in the burner flame.
Replace the main burners as follows:
1. Lift burner and slide it to the rear just enough to
clear the gas orifice hood.
2. Lower the front end of burner and bring it forward
under the manifold pipe.
3. Remove the burner from the unit.
NOTE: When reinstalling burners, ensure that
locating pin is in the hole for proper positioning and to
prevent burner from rolling over.
4. To reinstall, reverse the steps above.
F24627 (0916) Page 22 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
Automatic Ignition Systems
When the main power switch is turned ON and the
ignition control modules reset switch is in the ON
position, the ignition control module (Fig. 12) is
energized with 24 volts between terminals five and six.
High voltage is sent from terminal nine to the spark
electrode and an output of 24 volts is sent from
terminals two and three to the pilot coil in the
combination valve, allowing gas to flow to the pilot.
The sparking will continue for 90 seconds or until the
flame sensor has confirmed that an adequate pilot
flame is present.
Once the pilot flame is confirmed, a 24 volt output from
terminal one will be sent, allowing the cycling coil of
the combination valve to operate at the request of the
cycling pressure switch.
3. Pilot Voltage. 24VAC will be present on terminal
#3 at the instant an input voltage is supplied to
the module. This voltage will remain present on
terminal #3 providing an adequate pilot flame is
established within 90 seconds. In the event that
an adequate pilot flame is not established within
90 seconds this output voltage will drop out.
4. Ground (Burner).
5. Ground (24VAC Neutral).
6. 24VAC Input.
7. High Voltage. This signal is supplied to spark
electrode (The pilot flame current is sensed by
the module via the spark electrode high voltage
wire and terminal #9).
Spark Ignition Control Test
1. If the ignition control module does not appear to
be sparking to ignite gas, perform the following
checks:
A. Check to ensure that all electrical terminal
connections on the ignition control module
and the ignitor are clean and tight.
Fig. 12
Terminals
1. Main Voltage. 24VAC will be present on terminal
#1 with the pilot sensing electrode sensing an
adequate pilot fame. This output will remain
present as long as the pilot flame remains
adequate.
2. Common (MV/PV).
B. Verify that the ignition control module and
the ignitor have good ground wire
connections. The ignitor mounting bracket
should have good metal to metal contact to
its mounting surface.
C. Turn the main power switch ON. Turn the
ignition control modules re-set switch OFF
then ON.
D. Check for 24VAC output on the ignition
control module transformer.
1) If 24VAC is present then replace
ignition control module and re-test.
2) If 24VAC is not present then ensure
that transformer is receiving 120VAC
input. If ignition control module
transformer is receiving proper
voltage, then replace ignition control
module transformer and re-test.
2. If the ignition control module and transformer are
functioning properly, then check the following
ignitor conditions.
A. The gap between the spark probe (Fig. 13)
and the ground clip should be approximately
1/8 inch. If the gap appears to be excessive
or poor sparking is occurring, remove the
electronic ignition pilot and adjust gap.
Page 23 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
Fig. 13
B. Inspect the ceramic flame rod insulator for
cracks or evidence of exposure to extreme
heat, which can permit leakage to ground. If
either of these conditions exist, then replace
the pilot ignitor assembly.
C. Check the ignition cable for tightness or
damaged insulation.
3. Recheck unit for proper operation.
Manifold Pressure Adjustment
Measure the pressure as follows:
1. Open the front cabinet doors.
2. Turn the gas combination control valve (Step 2)
to OFF.
4. Turn the gas combination control valve and the
main power switch to ON.
5. Observe the manometer pressure reading and
compare to the pressure chart near the end of
this procedure.
6. If other appliances are connected to the same
gas line:
A. Turn them all ON.
B. Check manometer pressure reading again.
• If a pressure drop of ½ inch water
column or more is observed, then the
gas supply needs to be checked by the
gas line installer or the local gas
company for adequate sizing.
7. If no other gas appliances are connected to the
gas line and the manifold pressure still requires
adjustment, perform the steps below.
NOTE: Accurate gas pressure adjustments can only
be made with the gas ON and the burner lit.
A. Remove the adjustment screw cap to
access the pressure adjustment screw.
• To increase pressure, turn the screw
clockwise.
• To decrease pressure, turn the screw
counterclockwise.
NOTE: If the incoming line pressure is less than the
minimum stated, then the manifold pressure can not
be set correctly.
Fig. 14
3. Remove the 1/8 inch NPT plug (pressure tap) on
the outlet (manifold) side of the valve and attach
a manometer.
F24627 (0916) Page 24 of 82
HEAT - ELECTRIC MODELS
B. After the burner lights, set the pressure as
outlined below.
C. Once the correct pressure has been set:
1) Turn the power switch OFF.
2) Replace the adjustment screw cap and
1/8 inch NPT plug (pressure tap) on the
outlet side of the valve.
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
Magnetic Contactor
A noisy contactor (hum or chatter) is generally due to
enough dust or dirt on the armature pole faces or
around the armature core that the magnet coil cannot
pull the armature into a completely sealed position.
This can usually be corrected by blowing or wiping the
pole faces clean.
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
Inspect the contactor as follows:
1. Remove two screws and the contactor cover.
2. Look at the electrical contacts for damage (pits
and / or burns).
3. If damage is found, replace contactor.
Certain procedures in this section
require electrical test or measurements while power is
applied to the machine. Exercise extreme caution at
all times. If test points are not easily accessible,
disconnect power and follow lockout / tagout
procedures, attach test equipment and reapply power
to the test.
1. Measure the voltage at the heating element
terminals and verify it against the data plate
voltage.
A. If voltage is correct then proceed to Step 2.
B. If voltage is not correct, check the following:
• Fuses or breaker blown.
• Power to contactor coils.
• Contactors not pulling in (mechanical
linkage damaged).
2. Check current draw (amps) through the heating
element lead wires. See Table 10.
A. If current draw is correct then heating
element is ok.
B. If current draw is not correct then proceed to
Step 3.
3. Disconnect the heating element lead wires.
4. Use a VOM to check the element resistance.
• If resistance readings are not correct,
replace the heating element.
Heating Element
AMPS PER LINE RESISTANCE
VOLTAGE TOTAL KW
208 18 2 9 87 50 14.42
240 18 2 9 75 44 19.20
480 18 2 9 NA 22 76.80
*220 / 380
18 2 9 NA 25 19.20
240 / 415
208 24 4 6 116 68 21.63
240 24 4 6 100 58 28.80
480 24 4 6 NA 29 115.20
*220 / 380
24 4 6 NA 57.8 28.80
240 / 415
208 24 2 12 116 68 10.82
240 24 2 12 110 58 14.40
480 24 2 12 NA 29 57.60
*220 / 380
24 2 12 NA 34 14.40
240 / 415
NUMBER OF
ELEMENTS
KW PER
ELEMENT
1PH 3 PH
PER ELEMENT
1 PH 3 PH
(OHMS)
Page 25 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
AMPS PER LINE RESISTANCE
VOLTAGE TOTAL KW
208 36 4 9 NA 100 14.42
240 36 4 9 NA 87 19.20
480 36 4 9 NA 44 76.80
*220 / 380
36 4 9 NA 50 19.20
240 / 415
208 42 4 10.5 NA 117 12.36
240 48 4 12 NA 116 14.40
480 48 4 12 NA 58 57.60
*220 / 380
48 4 12 NA 67 14.40
240 / 415
NOTE:
• Values in the table are nominal. Tolerance is
+/-10 %.
NUMBER OF
ELEMENTS
KW PER
ELEMENT
1PH 3 PH
B. If required clean the flange and tube
mounting surfaces.
C. Install a new gasket on the heating element.
PER ELEMENT
1 PH 3 PH
(OHMS)
• Asterisk (*) indicates 3 phase/4wire.
• Each heater has three internal elements.
• 6.0 KW heaters used on older models and
included for reference.
CAUTION Use only mechanical cleaning methods
on heating elements. Do not immerse elements in a
chemical solution to descale.
NOTE: If the removed element shows a pronounced
scale build-up on its heating tubes, the other elements
should be removed and mechanically cleaned to
remove the scale.
Replace a heating element as follows:
1. Remove
A. Drain the water from boiler shell.
B. Remove cover of contactor box.
C. Disconnect electric wires from the element
terminals.
D. Remove bolts that secure the element in
place.
E. Pull the element out of the unit.
NOTE: Always replace the gasket when a heating
element is removed / replaced.
2. Install
A. Look at the flange and tube mounting
surfaces.
D. Inset the heating element in the unit and
secure in place with bolts. Tighten the bolts
hand tight plus a quarter turn.
E. Reconnect the electrical wires to the heating
element terminals. Tighten the fasteners
hand tight.
F. Install the cover on the contactor box.
3. Refill the boiler and check for proper operation.
HEAT - DIRECT STEAM MODELS
These models consist of a pressure regulator and
gauge that run off a buildings potable steam supply.
The maximum input pressure to the regulator should
be 15 psi. Incoming power (120VAC) for the
compartment controls is supplied from a junction box
in the base.
HEAT - REGENERATED STEAM MODELS (STEAM
COIL)
CAUTION The regulator should be set ONLY when
steam is flowing (steam solenoid valve is open).
NOTE: If steam is heavy with condensate, a ball float
trap can be installed in the steam line before the
pressure regulating valve.
The steam coils are intended for use at a steam supply
pressure of 15 psi maximum. A pressure regulating
valve is available as optional equipment for steamers
where the steam supply pressure exceeds 15 psi. The
regulator:
• Must be adjustable.
F24627 (0916) Page 26 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
• Must be set for a discharge pressure of 15 psi.
Replace a steam coil as follows:
1. Remove
A. Disconnect the union in steam supply line to
the coils.
B. Disconnect the union in condensate
discharge line from the coils.
C. Disconnect the union at each coil to remove
the steam supply header.
D. Disconnect the union at each coil to remove
the coil condensate collection header.
E. Remove the four bolts that secure the coil in
place.
F. Pull the coil out of the unit.
G. Refill the boiler and check for proper
operation.
NOTE: Always replace the gasket when a heating
element is removed / replaced.
2. Install
A. Look at the flange and mating surfaces.
B. If required clean the flange and mating
surfaces.
C. Install a new gasket on the coil mate face.
D. Insert the coil in the unit and secure in place
with bolts. Tighten the bolts hand tight plus
a quarter turn.
Clean pipe threads and apply thread
sealant that is suitable for use with propane gases.
E. Reconnect the unions and tighten them
hand tight.
3. Turn steamer power switch ON.
4. Allow steam generation and pressure to rise to
normal operating level.
5. Turn power switch OFF for a final purging of
boiler and steam supply lines.
6. Steamer is now ready for use.
Cooking Compartment
Certain procedures in this section
require electrical test or measurements while power is
applied to the machine. Exercise extreme caution at
all times. If test points are not easily accessible,
disconnect power and follow lockout / tagout
procedures, attach test equipment and reapply power
to the test.
CONTROLS
For access to compartment controls, remove the right
side compartment panel. Check for failure of the
control circuit in the following order:
1. Ensure that voltage is reaching control circuit
through compartment pressure switch, when the
main power switch is turned ON.
2. On electric heat models with a transformer,
check step down transformer for proper
operation.
3. Check door switch for proper operation.
4. Check cooking timer function and contact
position. See Schematic All Models Compartment Controls.
5. Check that timer motor operates when
connected to power. If a problem is found in
timer, replace it, do not take timer apart.
6. Check wiring for damaged insulation / short
circuit.
7. Check that all connections and terminals are
securely fastened.
8. Check that all connections are made according
to compartment control wiring diagram.
STEAM SUPPLY SOLENOID
Each cooking compartment is supplied steam by its
own individual steam supply solenoid. These solenoid
valves are a standard type and can be disassembled
for cleaning.
Newer Steamer Models
• The magnetic coil of the solenoid valve is
removed from the valve by removing the snap
catch at the top.
• Unions or compression fittings are provided to
allow easy removal of the valve bodies.
• The solenoid valves must be removed for
disassembly as outlined under FILL AND COLD
WATER SOLENOID VALVES.
Older Steamer Models
Page 27 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
NOTE: Older steamer models have a movable blade.
When closed, the blade reacts as a guillotine that
should be free to move fully down into the valve pocket
(projection at bottom of valve) so that the pierced hole
in the blade aligns perfectly with the body opening.
1. Remove and disassemble the valve as follows:
A. Remove two screws and inlet port of valve
body.
B. Unthread and remove the plunger tube.
C. Remove the plunger and valve blade.
D. Remove the plastic seat from the valve
body.
2. Inspect the valve:
• The blade must be clean.
• The blade mating surfaces of the plastic
seat members must be flat and undamaged.
• The plunger and plunger tube must be
clean.
• The plunger must slide freely in the tube.
3. If the steamer ready light is on, then proceed to
Step 6.
4. If the boiler is off, then turn main power switch ON
and allow boiler to heat up until steamer ready
light comes on.
5. Turn both cooking timers on and allow boiler to
cycle 2 to 3 times, then proceed to Step 7.
6. Turn both cooking timers on.
7. Monitor the boiler until heat source turns off.
NOTE: Adjust the valve when the boiler pressure is
at the upper cycling limit.
8. Adjust the intake shut-off valve until the manifold
pressure gauge reads 9 ±1 psi.
9. Monitor gauge reading 1 to 2 cycles to ensure
pressure is set correctly.
10. Once the valve is set:
A. Turn both cooking timers off.
B. Reinstall right side control panel.
• The compression spring which fits in the
hole in the top of the plunger must be clean
and move freely.
WATER ACCUMULATING IN COMPARTMENT
Water accumulation on the bottom of the cooking
compartment(s) is primarily condensed steam. Failure
to drain out quickly and completely may be due to:
• Debris in the compartment drain screen.
• Improper leveling of the steamer.
To clean the drain screen:
1. Pull it out of the cooking compartment.
2. Thoroughly clean it until no debris remains.
3. Reinstall it in the cooking compartment..
COOKING CYCLE CANNOT BE ACTIVATED
When the power switch on boiler control box is ON,
set the timer knob to 2 minutes. Both READY lights
should go off, COOKING lights should come on and
steam should be entering both compartments. If that
does not occur, inspect all wire terminations to ensure
they are properly connected and secure.
INTAKE SHUT-OFF VALVE ADJUSTMENT
NOTE: The intake shutoff valve controls the amount
of steam supplied to steam control solenoid valve.
Fig. 16
DOOR ASSEMBLY
Door
1. Remove
A. Remove top cover.
1. Remove right side control panel.
2. Open the intake shut-off valve (Fig. 16)
completely.
F24627 (0916) Page 28 of 82
B. Open the door.
C. Pull hinge rod up.
D. Remove the door from the steamer.
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
2. Install
A. Inspect the door and steamer to ensure the
door bushings are in place.
B. Align the door in the steamer.
C. Slide the hinge rod down through the door.
D. Close the door.
E. Install the top cover.
Door Gasket
1. Remove
A. Open the door.
B. Remove the screws (Fig. 17) and gasket
plate from the door housing.
C. Remove the gasket from the gasket plate.
3. Adjust
A. Check the door gasket quality.
• If unacceptable, replace the gasket.
• If acceptable, proceed with
adjustment.
B. Loosen screws until the screw heads no
longer touch the gasket plate.
C. Tighten screws until screw head touches
gasket plate and at that point begin counting
turns.
D. Tighten all screws approximately two turns.
E. Close the door and check unit for proper
operation.
F. If necessary, tighten all screws an additional
½ turn and repeat .
G. Repeat until the door closes properly and no
steam leaks are seen around the gasket
seal.
Handle
Fig. 17
2. Install
NOTE: Damage to the gasket sealing surface will
allow steam leakage.
A. Inspect the replacement gasket. No
damage to the sealing surface is allowed.
B. Position the gasket on the gasket plate.
NOTE: Over-tightening the screws will compress the
gasket and interfere with proper door sealing.
1. Remove
A. Open the door.
B. Remove screws from the top and bottom of
the door.
C. Pull the inner door panel (Fig. 18) out from
the door housing with the gasket plate and
gasket still attached.
D. Remove the nuts and spacers from the
handle screws and remove the handle from
the door.
2. Install
NOTE: When installing the spacers, the smaller
diameter fits into the slot in the door and the latch lever
must rest on top of the handle latch screw.
A. Install the handle (Fig. 19) on the door and
secure in place with nuts and spacers.
Tighten the nut hand tight.
B. Install the inner door panel / gasket plate in
door housing.
C. Align the inner door panel and secure in
place with screws. Tighten the screws hand
tight.
D. Close the door.
C. Align the gasket plate on the door housing
and secure in place with screws. Do not over
tighten the screws.
Page 29 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
Fig. 20
C. Pull the inner door panel out from the door
housing with the gasket plate and gasket
still attached.
D. Remove the side edge screws (Fig. 21) that
secure the latch mechanism in the door.
Fig. 18
Fig. 19
Latch
CAUTION Should the cooker door jam and can not
be opened, DO NOT FORCE OR PRY the door as
damage will occur.
First, try lifting up on the bottom of the door at the
handle end to disengage the latch. If that does not
work, remove the right side panel. The striker that
catches on the door latch is located behind the front
face of the cooking cavity. Remove the striker nut (Fig.
20) this will release it from the panel.
1. Remove
A. Open the door.
B. Remove screws from the top and bottom of
the door.
E. Remove the latch from the door.
Fig. 21
2. Install
A. Place the latch in the door and align the
mounting holes.
B. Use screws to secure the latch in the door.
Tighten the screws hand tight.
C. Align the inner door panel and secure in
place with screws. Tighten the screws hand
tight.
D. Close the door.
3. Adjust
A. If necessary, loosen the nut and align the
striker with the slot pointing upwards.
B. Finger tighten the nut.
C. Close the door to center the striker in the
oval mounting hole.
D. Open the door and check the strikers’ slot
for horizontal alignment (Fig. 22). The slot
on the striker must be kept horizontal in
order for the door latch to catch it properly
and latch.
F24627 (0916) Page 30 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
E. Once the proper slot alignment has been
set, hold the striker close to its base using a
rag and vise grips.
F. Tighten the striker nut hand tight plus a
quarter turn. Be careful not to damage the
striker slot when tightening or door may not
latch properly.
Fig. 22
Page 31 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
ELECTRICAL OPERATION
Water Level Controls
SOLID STATE - LOW LEVEL CUT OFF AND
DIFFERENTIAL CONTROL
The steamer is equipped with three water level
sensing probes (High Level [HL], Low Level [LL], and
Low Level Cut Off [LLCO]) and a single Water Level
Control (WLC) board. The WLC board (Fig. 23)
performs two functions:
• Provide low level cut-off protection to shut off the
heat source in case the water level drops below
the LLCO probe.
• Perform as a differential level control to maintain
the water level between the HL and LL probes.
Fig. 23
The WLC board has input voltage (120VAC) across
terminals 11 and 12 (Fig. 24) which powers the
primary side of the transformer. On one side of the
transformer secondary, power is provided to the
control by a series path through chassis ground
(terminal 10). The other side of the transformer
secondary (12VAC) is attached to the probe that
directs power to the other side of the internal relays
(LLCO, HL and Inverse Latching [IL]). As water enters
the boiler, it becomes part of the water level control’s
circuit. When the water level in the boiler reaches a
probe, that circuit is completed.
The IL relay is deenergized, leaving the ILR-1 (N.O.)
and ILR-2 (N.C.) contacts in their shelf state.
When the main power switch is turned ON, power is
supplied to the WLC board which energizes the HL
relay and turms on the HL relay LED. With the HL-3
contacts close, the boiler fill solenoid is energized and
water begins filling the boiler.
Fig. 24
When the water level reaches the LLCO probe, the
LLCO relay energizes and turns on the LLCO LED.
With the LLCO-2 contacts closed the heat source is
then energized. The LLCO relay will remain energized
and its LED will stay lit until the water level in the boiler
drops below the LLCO probe.
When the water level reaches the LL probe, power to
terminal 2 on the WLC board is present but no
switching occurs.
After the water level reaches the HL probe, the IL relay
energizes and is locked ON through the LL probeand
ILR-1 contacts. With ILR-2 contacts open, this deenergizes the HL relay and the HL LED goes out. With
the HL-3 contacts open, the boiler fill solenoid is deenergized, stopping the flow of water into the boiler.
When the water level drops below the LL probe, power
is removed from the IL relay, the HL relay energizes
through ILR-2 and HL contacts change state. The fill
solenoid is energized through HL-3 to refill the boiler
and the HL LED is lit. The HL relay and LED will toggle
ON and OFF during a cooking cycle as needed.
SOLID STATE AUXILIARY LOW LEVEL CUT OFF
This control (Fig. 25) serves as a safety backup to the
main water level control (WLC) board to meet CalCode and CSD-1 code requirements. The operation
of the auxiliary control is identical to the Low Level Cut
Off (LLCO) function of the main WLC board.
F24627 (0916) Page 32 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Fig. 25
However, it performs a single function:
• It provides auxiliary low level cut-off protection to
shut off the heat source in case the water level
drops below the low level cutoff (LLCO) probe.
A single LLCO probe, identical to the LLCO probe on
the main WLC board, is connected to the auxiliary
control.
The auxiliary water level control has input voltage
(120VAC) across terminals 11 and 12 (Fig. 26) which
powers the primary side of the transformer. On one
side of the transformer secondary, power is provided
to the control by a series path through chassis ground
(terminal 10). The other side of the transformer
secondary (12VAC) is attached to the control that
directs power to the other side of the internal relay
(LLCO). As water enters the boiler, it becomes part of
the auxiliary water level control’s circuit. When the
water level in the boiler reaches the LLCO probe, the
circuit is completed.
When the main power switch is turned ON, power is
supplied to the auxiliary WLC board but no switching
occurs. On CSD-1 models, the low water level
indicator light (amber) on the boiler control box comes
on.
When the water level reaches the LLCO probe, the
LLCO relay is energized (LLCO-2 close) and the
LLCO LED turns on. The LLCO relay will remain
energized and its LED will stay lit until the water level
in the boiler drops below the LLCO probe.
Fig. 26
When the boiler stops filling, press the manual reset
button on the boiler control box. On CSD-1 models,
this energizes the low water relay, turns off the low
water light and energizes the heat source auxiliary
control. On Cal-Code models, this closes and locks
the manual reset switch contacts to energize the heat
source auxiliary control.
ELECTRO MECHANICAL - LOW LEVEL CUT OFF
AND DIFFERENTIAL CONTROL
The steamer is equipped with three water level
sensing probes (High Level [HL], Low Level [LL], and
Low Level Cut Off [LLCO]) , a differential level control
(1G1DO) and a low level cut-off control (1D1DO). The
low level cut-off is an additional control that is identical
to the differential level control but serves as the safety
backup to shut off the heat source in case the water
level drops below the LLCO probe. The differential
level control maintains the water level between the LL
and HL probes.
Each control is powered by input voltage (120VAC) on
terminals 1 and 2 (Fig. 27) which also connect to the
primary side of the internal transformer. The
transformer secondary (300VAC) will provide power
to the internal contactor coil through a series path
going from one side of the secondary winding, through
the contactor coil, through the water level control
probe, through the water in the boiler and to the boiler
for ground. The other side of the transformer
secondary is attached to the probe that directs power
to the other side of the internal contactor coil.
When the main power switch is turned ON, both water
level controls are energized. The boiler fill solenoid is
then energized through the normally closed contacts
(terminals 3 & 4) on the 1G1DO control and water
begins filling the boiler.
When the water level reaches the LLCO probe, the
internal contactor coil on the low water level control is
energized. With the contacts on terminals 7 & 8 now
closed, the heat source is then energized. The internal
contactor coil will remain energized until the water
level in the boiler drops below the LLCO probe.
Page 33 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
When the water level reaches the LL probe, power to
terminal 7 on the 1D1DO control will be present but no
switching occurs.
After the water level reaches the HL probe, the 1D1DO
contactor coil is energized and the normally closed
contacts on terminals 3 & 4 open, which de-energizes
the boiler fill solenoid and stops the flow of water into
the boiler. The internal contactor coil will have a
locking path through contacts 7 & 8 to the low level
probe to keep the coil energized after the water level
drops below the HL probe.
When the water level drops below the LL probe, the
internal contactor coil is de-energized, returning
contacts 3 & 4 back to their normally closed state and
energizing the boiler fill solenoid to refill the boiler. The
water level must then fill to the LL probe again, to
energize the internal contactor coil. The 1D1DO
control will toggle ON and OFF during a cooking cycle
as needed.
ELECTRO MECHANICAL - AUXILIARY LOW
LEVEL CUT OFF
This control serves as a safety backup to the main low
level cut-off (LLCO) control to meet Cal-Code
requirements. The operation of the auxiliary control is
identical to the main low level cut-off control but
performs a single function:
• It provides auxiliary low level cut-off protection to
shut off the heat source in case the water level
drops below the LLCO probe.
Fig. 27
A single LLCO probe identical to the LLCO probe on
the main low level cut-off control is connected to the
auxiliary control.
The auxiliary control is powered by input voltage
(120VAC) on terminals 1 and 2 (Fig. 28) which also
connect to the primary side of the internal transformer.
The transformer secondary winding (300 VAC) will
provide power to the internal contactor coil through a
series path going from one side of the secondary
winding, through the contactor coil, through the water
level control probe, through the water in the boiler and
to the boiler for ground. The other side of the
transformer secondary is attached to the LLCO probe
which directs power to the other side of the internal
contactor coil.
When the main power switch is turned ON, the
auxiliary low level control is energized but no switching
occurs.
When the water level reaches the LLCO probe, the
internal contactor coil on the low level control is
energized, closing the contacts on terminals 7 & 8.
The internal contactor coil will remain energized until
the water level in the boiler drops below the LLCO
probe.
When the boiler stops filling, press the manual reset
button on the boiler control box. This closes and locks
the manual reset switch contacts to energize the heat
source auxiliary control.
F24627 (0916) Page 34 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sequence of Operations
GAS MODELS
This sequence of operation is written for steamers with
automatic ignition, solid state water level controls and
the CSD-1 (code) option. Refer to Schematics, Gas
Steamers, Boiler Controls VSX24G, 36G and 42GT.
Initial Fill and Preheat
1. Conditions.
• Power switch OFF.
• Ignition module reset switch ON.
• Doors shut (N.O. door switch CLOSED).
• Cooking timers OFF.
• Unit connected to correct voltage (120VAC).
• L1 to one side of the cooking
compartment pressure switch (N.O.),
then to the other compartment
controls; to one side of the cold water
condenser thermostat; to one side of
the power ON/OFF switch.
• NEUTRAL to one side of the cooking
compartment controls; to one side of
the Cold Water Condenser (CWC)
solenoid valve; to one side of the power
ON/OFF switch.
• Unit properly grounded (boiler and water
level control share a common ground).
Fig. 28
• Water supply valve ON.
• Gas supply valve ON.
• Gas combination control valve ON.
• Control (cycling) pressure switch CLOSED.
• High limit pressure switch CLOSED.
• CWC thermostat OPEN.
• Blowdown solenoid valve (drain) OPEN.
• Boiler empty.
2. Power switch (located on boiler control box)
turned ON.
• Red power switch indicator light turns ON.
• Amber high pressure indicator light turns
ON.
• Amber low water level indicator light turns
ON.
NOTE: The amber high pressure indicator light will
remain on and the safety circuit de-energized until
boiler steam pressure is within operational limits (high
limit pressure switch closed) and the manual reset
button is pressed. The amber low water indicator light
will remain on and the safety circuit de-energized until
the water level in the boiler reaches the low level cutoff probes (minimum level) for the water level control,
the auxiliary low level cut-off control and the manual
reset switch is pressed. The gas burners will not light
until these conditions are satisfied.
Page 35 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
• Water Level Control (WLC) is powered ON.
• HL relay is energized, HL-3 (N.O.)
contacts close and HL LED turns ON.
• The IL relay remains de-energized,
leaving the ILR-1 (N.O.) and ILR-2
(N.C.) contacts in their shelf state.
• Auxiliary low water level cut-off control is
powered, LLCO-2 (N.O.) contacts remain
open.
• With the HL-3 and ILR-2 contacts closed,
the fill solenoid is energized and water boiler
begins filling.
• Blowdown solenoid valve is energized and
closes.
• Ignition module begins sparking to light pilot
after a 3-second delay.
• If pilot ignition is established (pilot lit)
then a micro amp flame sense current
is sent back to the ignition control
module through the ignition cable.
Sparking stops, pilot remains lit and is
ready to ignite burners.
• If pilot ignition is not established after
90 seconds, sparking stops and the
ignition control module locks out power
to the combination gas valve (pilot
valve and main valve remain closed).
The module remains locked out until
the reset switch on the ignition control
module box is switched to off then on
to re-start the ignition trial cycle.
NOTE: If the modules reset switch is in the OFF
position, no sparking will occur or if it’s turned off while
in READY or COOK mode then pilot and burners will
go out and not re-ignite upon call for heat by the
cycling pressure switch.
3. Water level reaches LLCO probe for the water
level control and to the auxiliary LLCO probe for
the auxiliary low level cut-off control.
• Power to terminal 9 on the water level
control.
NOTE: LLCO relays will remain energized and LLCO
LED’S will remain ON until the water level drops below
the LLCO probes or the power switch is turned OFF.
4. Water reaches LL probe.
• Power to terminal 2 on the water level
control is present but no switching occurs.
5. Water reaches HL probe (approximately 4-11
minutes).
• Power to terminal 6 on water level control.
• The IL relay is energized, changing the
state of ILR-1 (N.O.) and ILR-2 (N.C.)
contacts. The IL relay will remain
energized through the alternate
latching path of ILR-1 contacts until the
water level recedes below the LL
probe.
• With ILR-2 contacts open, HL relay is
de-energized, HL-3 (N.O.) contacts
open and HL LED turns OFF.
• Water fill solenoid is de-energized.
6. Manual re-set switch is pressed, energizing the
coils on the high limit and low water relays.
• Contacts 1 & 9 on the high pressure relay
change state and lock from N.C. to N.O. and
turn off the high pressure indicator light.
Concurrently, contacts 1 & 9 on the low
water relay change state and lock from N.C.
to N.O. and turn off the low water indicator
light.
• Contacts 5 & 9 on the high pressure relay
change state and lock from N.O. to N.C.,
supplying power (NEUTRAL) to one side of
the auxiliary gas solenoid valve.
Concurrently, contacts 5 & 9 on the low
water relay change state and lock from N.O.
to N.C., supplying power (L1) to the other
side of the auxiliary gas solenoid valve.
NOTE: For both relays to energize, the high pressure
switch must be closed and the water level in the boiler
must be above the LLCO probes in order for LLCO-2
(N.O.) contacts to close.
• LLCO relay energizes, LLCO-2 (N.O.)
contacts close and LED turns ON.
• Power to terminal LLCO on the auxiliary low
water level cut-off control.
• LLCO relay energizes, LLCO-2 (N.O.)
contacts close and LED turns ON.
F24627 (0916) Page 36 of 82
• Auxiliary gas solenoid valve is energized
and opens to allow gas flow.
• As long as the ignition control module is
sensing a pilot flame, the internal main valve
(MV) contacts close (N.O.) on the ignition
control module. The main gas valve is
energized and gas begins flowing.
• Burners light and boiler begins to heat up.
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
7. Cooking compartment pressure switch closes as
boiler steam pressure reaches 3 PSI
(approximately 14 minutes).
• Green READY light turns ON.
NOTE: If a cooking timer is set immediately after the
green READY light comes on, a loud clanking sound
will be heard (oil caning) and the ready light will flash
for several seconds. This condition is caused by the
manifold pressure being on the fringe of the pressure
switch set point. When a cook timer is set, the
compartment steam solenoid valve opens causing the
manifold steam pressure to drop, slightly below the
pressure switch set point. At the same time, steam
pressure is still increasing in the boiler. This opposing
condition causes a pressure bounce to occur but after
the steam pressure passes approximately 4 psi this
condition subsides. Under normal steam cycling
pressures, this condition will not be seen.
8. Boiler steam pressure reaches upper limit set
point of 10 PSI (approximately 15 minutes).
• Cycling pressure switch opens, main gas
solenoid valve de-energizes, gas flow shuts
off and burners go out.
• Boiler water level drops below the
LLCO probes for the water level and
the auxiliary low level cut-off controls
which then de-energizes the LLCO
relays, changing the contact state of
LLCO-2 (N.O.) back to open. This deenergize the main and auxiliary gas
solenoid valves. The gas solenoid
valves will remain off and the low water
level light will come on and stay lit until
the water level rises above the LLCO
probes and the manual re-set switch is
pressed.
Cook Cycle
1. A cook cycle should not be started, until the initial
fill and preheat is completed, in order for the
boiler steam pressure to be within operational
limits.
• Green READY light is ON.
• Product is inserted into steamer.
• Door is closed.
• Timer is dialed on timer.
NOTE: Steam should not be seen entering either
compartment until a cook time is set. This energizes
the steam solenoid valve of the cooking compartment
to allow steam flow.
9. Boiler steam pressure drops below lower limit set
point of 8 PSI and the cycling pressure switch
closes.
• Boiler steam pressure is maintained by the
cycling of the pressure switch between the
upper and lower set point limits. The cycling
pressure switch continues to energize and
de-energize the main gas solenoid valve
starting and stopping the flow of gas, which
in turn, cycles the burners on and off. This
sequence continues until one of the
following occurs:
• Boiler pressurizes to 15 PSI, causing
the high limit pressure switch to open.
At that time, the auxiliary gas valve deenergizes, shutting off the gas flow to
the burners and the high limit failure
light will come on. This light will stay lit
until the pressure drops below the
lower limit set point of 6 PSI and the
manual re-set switch is pressed.
2. Contacts 1/3 of cook timer close.
• Green READY light turns OFF.
• Red COOKING turns ON.
• Timer motor is energized.
• Compartment steam solenoid valve
energized and steam begins to enter the
compartment.
NOTE: Burners will re-light after the boiler pressure
drops below the low pressure set point limit (8 psi) and
will stay on until the high pressure set point (10 psi) is
reached. As long as steam pressure is within limits,
even while cooking, burners can go off. The boiler is
able to re-pressurize to the upper set point limit even
with both compartments in cook mode.
NOTE: The CWC thermostat remains closed and
CWC solenoid stays energized while cooking. If main
water is shut off after boiler fill, then no cold water is
present to condense steam/hot water and steam
vapors exit the floor drain.
3. Time expires on timer.
• Timer contacts 1/3 open.
• Steam solenoid valve de-energized,
stopping the flow steam into compartment.
• Red COOKING light turns OFF.
• Timer contacts 4/1 close and energize
buzzer until manually turned off.
Page 37 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
• Green READY light turns ON.
• Timer motor de-energized.
4. Timer manually turned off.
• Contacts 1/4 open
• Alarm buzzer de-energized and stops
buzzing.
5. Steamer reverts to preheat cycle until time is
dialed into timer and the door is shut, water level
drops below low level cut-off probe or the power
switch is turned off.
Water Refill (After Initial Fill)
1. Water level drops below LL probe.
• Power is removed from terminal 2 on the
water level control .
• The IL relay is de-energized, returning ILR-1
(N.O.) and ILR-2 (N.C.) contacts back to
their original state.
• HL relay is energized.
• Contacts HL-3 close.
• HL LED turns ON.
• Fill solenoid is energized and water
flows into tank.
2. Water reaches LL probe.
• Power to terminal 2 on the water level
control is present but no switching occurs.
3. Water reaches high level probe.
• The IL relay of the water level control is
energized, changing the state of ILR-1
(N.O.) and ILR-2 (N.C.) contacts.
• HL relay is de-energized.
• HL-3 opens.
• Power is removed from all components
except CWC thermostat and CWC solenoid
valve. The CWC thermostat cycles as
necessary to lower the discharge
temperature of the water and condense
steam going into the drain.
ELECTRIC MODELS
This sequence of operation is written for steamers with
solid state water level controls and the Cal-Code
option. Refer to Schematics, Electric Steamers, Boiler
Controls VSX24E, 36E and 42ET.
Initial Fill and Preheat
1. Conditions.
• Power switch OFF
• Doors shut (N.O. door switch CLOSED).
• Cooking timers OFF.
• Unit connected to correct voltage supply.
• L1 (HOT) to in-line fuse (10 amp.); to
one side of the primary on the step
down transformer (H1); from one side
of the secondary winding (X1) to one
side of the cooking compartment
pressure switch (N.O.), then to the
other compartment controls; to one
side of the Cold Water Condenser
(CWC) thermostat (N.O.); to one side
of the power ON/OFF switch.
• L2 (NEUTRAL) to in-line fuse (10
amp.); to the other side of the primary
on the step down transformer (H2);
from the other side of the secondary
winding (X1) to the other side of the
cooking compartment controls; to the
other side of the CWC solenoid valve;
to the other side of the power ON/OFF
switch.
• Fill solenoid de-energized and water
stops flowing into tank.
• HL LED turns OFF.
4. The water refill cycle will occur whenever the
water level is below the LL probe and will not
affect the operation of either the preheat or cook
cycle.
Boiler Blowdown / Drain
1. Main power switch turned OFF.
• Boiler blowdown sequence starts.
• The blowdown solenoid valve (N.O.) is de-
energized and valve opens to drain the
boiler.
F24627 (0916) Page 38 of 82
2. Power switch (located on boiler control box)
• Unit properly grounded (boiler and water
level control share a common ground).
• Water supply valve ON.
• Control (cycling) pressure switch CLOSED.
• High limit pressure switch CLOSED.
• CWC thermostat OPEN.
• Blowdown solenoid valve (drain) OPEN.
• Boiler empty.
turned ON.
• RED power switch indicator light turns ON.
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
• Water Level Control (WLC) is powered.
• HL relay is energized, HL-3 (N.O.)
contacts close and HL LED turns ON.
• The IL relay remains de-energized,
leaving the ILR-1 (N.O.) and ILR-2
(N.C.) contacts in their shelf state.
• Auxiliary LLCO control is powered, LLCO-2
(N.O.) contacts remain open.
• With the HL-3 and ILR-2 contacts close, the
fill solenoid is energized and boiler begins
filling.
• Blowdown solenoid valve is energized and
CLOSES.
3. Water level reaches LLCO probe for the water
level control and to the auxiliary LLCO probe for
the auxiliary LLCO control.
• Power to terminal 9 on the main water level
control.
• LLCO relay energizes, LLCO-2 (N.O.)
contacts close and LLCO LED lights.
• Power to terminal LLCO on the auxiliary
LLCO control.
• LLCO relay energizes, LLCO-2 (N.O.)
contacts close and LLCO LED lights.
• Manual reset switch contacts (N.O.) close
and lock.
• Heater contactors are energized, suppling
power to the heating elements.
• Water in boiler heats up.
7. Cooking compartment pressure switch closes as
boiler steam pressure reaches 3 PSI
(approximately 14 minutes).
• Green READY light turns ON.
NOTE: If a cooking timer is set immediately after the
green READY light comes on, a loud clanking sound
will be heard (oil caning) and the READY light will flash
for several seconds. This condition is caused by the
manifold pressure being on the fringe of the pressure
switch set point. When a cook timer is set, the
compartment steam solenoid valve opens causing the
manifold steam pressure to drop, slightly below the
pressure switch set point. At the same time, steam
pressure is still increasing in the boiler. This opposing
condition causes a pressure bounce to occur but after
the steam pressure passes approximately 4 psi this
condition subsides. Under normal steam cycling
pressures, this condition will not be seen.
8. Boiler steam pressure reaches upper limit set
point pressure of 13 PSI (approximately 15
minutes).
NOTE: LLCO relays will remain energized and LLCO
LED’S will remain ON until the water level drops below
the LLCO probes or the power switch is turned OFF.
4. Water reaches LL probe.
• Power to terminal 2 on the water level
control is present but no switching occurs.
5. Water reaches HL probe (approximately 4-11
minutes).
• Power to terminal 6 on the water level
control.
• The IL relay of the is energized,
changing the state of ILR- 1 (N.O.) and
ILR-2 (N.C.) contacts. The IL relay will
remain energized through the alternate
latching path of ILR-1 contacts until the
water level recedes below the LL
probe.
• With ILR-2 contacts open, HL relay is
de-energized, HL-3 (N.O.) contacts
open and HL LED turns OFF.
• Water fill solenoid is de-energized.
6. Manual re-set switch is pressed.
• Cycling pressure switch opens, heater
contactors de-energize and power to
heating elements is removed.
• As boiler heats up and builds steam
pressure, some by-pass water/steam is
produced which runs in to the steam drain
box. This causes the cold water condenser
(CWC) solenoid to cycle, cooling the drain
water. This solenoid is powered by the CWC
thermostat.
NOTE: Steam should not be seen entering either
compartment until a cook time is set. This energizes
the steam solenoid valve of the cooking compartment
to allow steam flow.
9. Boiler steam pressure drops below lower limit set
point of 11 PSI and the cycling pressure switch
closes.
• Boiler steam pressure is maintained by the
cycling of the pressure switch between the
upper and lower set point limits. The cycling
pressure switch continues to energize and
de-energize the heating element
contactor(s), which in turn, cycles the
heating elements on and off. This sequence
continues until one of the following occurs:
Page 39 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
• Boiler pressurizes to 15 PSI, causing
the high limit pressure switch to open.
At that time, the auxiliary heating
element contactors are de-energized,
shutting off power to the heating
elements. The pressure switch will
remain open until the pressure drops
below the lower limit set point of 6 PSI
and the manual reset switch is
pressed.
• Boiler water level drops below the
LLCO probes for the water level and
the auxiliary LLCO controls which deenergizes the LLCO relays and
changes the contact state of LLCO-2
(N.O.) back to open. This de-energize
the main and auxiliary heating element
contactors, shutting off power to the
heating elements. The heating
elements will remain off until the water
level rises above the LLCO probes and
the manual re-set switch is pressed.
Cook Cycle
1. A cook cycle should not be started, until the initial
fill and preheat is completed, in order for the
boiler steam pressure to be within operational
limits.
• Green READY is ON.
present to condense steam/hot water and steam
vapors exit the floor drain.
3. Time expires on timer.
• Timer contacts 1/3 open.
• Steam solenoid valve de-energized,
stopping the flow steam into compartment.
• Red COOKING light turns OFF.
• Timer contacts 4/1 close and energize
buzzer until manually turned off.
• Green READY light turns ON.
• Timer motor de-energized.
4. Timer manually turned off.
• Contacts 1/4 open.
• Alarm buzzer de-energized and stops
buzzing.
5. Steamer reverts to preheat cycle until time is
dialed into timer and the door is shut, water level
drops below LLCO probe or the power switch is
turned OFF.
Water Refill (After Initial Fill)
1. Water level drops below LL probe.
• Power is removed from terminal 2 on the
water level control.
• Product is inserted into steamer.
• Door is closed.
• Timer is dialed on timer.
2. Contacts 1/3 of cook timer close.
• Green READY light turns OFF.
• Red COOKING light turns ON.
• Timer motor is energized.
• Compartment steam solenoid valve
energized and steam begins to enter the
compartment.
NOTE: Heating elements will come on after the boiler
pressure drops below the low pressure set point (11
PSI) and will stay on until the high pressure set point
(13 PSI) is reached. As long as steam pressure is
within these limits, even while cooking, heating
elements can go off. The boiler is able to re-pressurize
to the upper set point, even with both compartments
in cook mode.
NOTE: The CWC thermostat remains closed and
CWC solenoid stays energized while cooking. If main
water is shut off after boiler fill, then no cold water is
• The IL relay is de-energized, returning
ILR-1 (N.O.) and ILR-2 (N.C.) contacts
back to their original state.
• HL relay is energized.
• Contacts HL-3 close. 2) HL
• HL LED turns ON.
• Fill solenoid is energized and water
flows into tank.
2. Water reaches LL probe.
• Power to terminal 2 on the water level
control is present but no switching occurs.
3. Water reaches HL probe.
• The IL relay of the is energized, changing
the state of ILR-1 (N.O.) and ILR-2 (N.C.)
contacts.
• HL relay is de-energized.
• HL-3 opens.
• Fill solenoid de-energized and water
stops flowing into tank.
• HL LED turns OFF.
F24627 (0916) Page 40 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
4. The water refill cycle will occur whenever the
water level is below the LL probe and will not
affect the operation of either the preheat or cook
cycle.
Boiler Blowdown / Drain
1. Main power switch turned OFF.
• Boiler blowdown sequence starts.
• The blowdown solenoid valve (N.O.) is de-
energized and valve opens to drain the
boiler.
• Power is removed from all components
except CWC thermostat and solenoid valve.
The CWC thermostat cycles as necessary
to lower the discharge temperature of the
water and condense steam going into the
drain.
Page 41 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Schematics, Gas Steamers, Boiler Controls VSX24G, 36G and 42GT
MANUAL IGNITION, STANDARD CONTROLS
F24627 (0916) Page 42 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
ELECTRONIC IGNITION, STANDARD CONTROLS
Page 43 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
MANUAL IGNITION, CSD-1 CODE CONTROLS
F24627 (0916) Page 44 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
ELECTRONIC IGNITION, CSD-1 CODE CONTROLS
Sheet 1
Page 45 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 46 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Wiring Diagrams, Gas Steamers, Boiler Controls VSX24G, 36G and 42GT
MANUAL IGNITION, STANDARD CONTROLS
Sheet 1
Page 47 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 48 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
ELECTRONIC IGNITION, STANDARD CONTROLS
Sheet 1
Page 49 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 50 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
MANUAL IGNITION, CSD-1 CONTROLS
Sheet 1
Page 51 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 52 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
ELECTRONIC IGNITION, CSD-1 CONTROLS
Sheet 1
Page 53 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 54 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Schematics, Electric Steamers, Boiler Controls VSX24E, 36E and 42ET
AUTO BLOWNDOWN, STANDARD CONTROLS
Fig. 42
Page 55 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWNDOWN, CAL-CODE CONTROLS
Fig. 43
F24627 (0916) Page 56 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWNDOWN, STANDARD CONTROLS
Fig. 44
Page 57 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWNDOWN, CAL-CODE CONTROLS
Fig. 45
F24627 (0916) Page 58 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Wiring Diagrams, Electric Steamers, Boiler Controls VSX24E, 36E and 42ET
AUTO BLOWDOWN, STANDARD CONTROLS
Sheet 1
Page 59 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 60 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWDOWN, CAL-CODE CONTROLS
Sheet 1
Page 61 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 62 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWDOWN, STANDARD CONTROLS
Sheet 1
Page 63 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 64 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWDOWN, STEP DOWN TRANSFORMER, STANDARD CONTROLS
Sheet 1
Page 65 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 66 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWDOWN, STEP DOWN TRANSFORMER, CAL-CODE CONTROLS (2 CONTACTORS)
Sheet 1
Page 67 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 68 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWDOWN, STEP DOWN TRANSFORMER, CAL-CODE CONTROLS (4 CONTACTORS)
Sheet 1
Page 69 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Sheet 2
F24627 (0916) Page 70 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Wiring Diagrams, Electric Heater Circuits VSX24E, 36E and 42ET
STANDARD AND CAL-CODE / CSD-1 CONTROLS (NEWER MODELS)
Fig. 58
Page 71 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
STANDARD AND CAL-CODE CONTROLS (OLDER MODELS)
Fig. 59
F24627 (0916) Page 72 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
3 PHASE / 4 WIRE (OLDER MODELS)
Fig. 60
Schematic, Direct Steamers, Cabinet Base VSX24D, 36D and 42DT
Page 73 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
See Wiring Diagram, All Models - Compartment Controls.
Wiring Diagram, Direct Steamers, Cabinet Base VSX24D, 36D and 42DT
See Wiring Diagram, All Models - Compartment Controls.
F24627 (0916) Page 74 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Wiring Diagrams, Regenerated Steamers, Boiler Controls VSX36R and 42RT
(Older Models)
MANUAL BLOWDOWN
Fig. 61
Page 75 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
AUTO BLOWDOWN
Fig. 62
F24627 (0916) Page 76 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Schematic All Models - Compartment Controls
Fig. 63
Page 77 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - ELECTRICAL OPERATION
Wiring Diagram, All Models - Compartment Controls
Fig. 64
F24627 (0916) Page 78 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - TROUBLESHOOTING
TROUBLESHOOTING
All Models
Certain procedures in this section
require electrical test or measurements while power is
applied to the machine. Exercise extreme caution at
all times. If test points are not easily accessible,
disconnect power and follow lockout / tagout
procedures, attach test equipment and reapply power
to the test.
SYMPTOM POSSIBLE CAUSES
Compartment leaks water around door.
Cold water condenser not operating properly.
Steam leaks around door.
Steam generated inside compartment when timer is off.
Heat coming on without water in boiler (Dry firing).
Pressure relief valve opening or leaking.
Base unit will not heat or build pressure.
Steamer not level.
Drain line obstructed or not to an open gap drain.
Cold water condenser solenoid inoperative or plugged.
Lack of water supply.
Cold water condenser thermostat malfunction or needs
adjustment.
No power to cold water condenser solenoid.
Plugged spray nozzle.
Worn gasket - See DOOR ASSEMBLY.
Damaged gasket.
Drain line obstructed or not to an open drain.
Steam supply solenoid not fully closing (clogged or dirty).
Replace the steam valve - see FILL AND COLD WATER
SOLENOID VALVES.
Timer contacts 1 & 3 closed.
Dirty water level probes (shorted to ground).
Retention of water in probe canister assembly.
Water level control malfunction.
Cycling pressure switch set to high. See .
Pressure relief valve malfunction.
Check incoming voltage.
Boiler not filled - check fill solenoid for power, clogging or
malfunction.
Water Level Control malfunction.
Water too “pure” for probes to properly conduct
electricity.
Contactor malfunction (electric only).
Heating element inoperative (electric only).
Cycling pressure switch open or set too high. Unit is
cycling on high limit.
High limit thermostat open.
Page 79 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - TROUBLESHOOTING
SYMPTOM POSSIBLE CAUSES
Problem with auto blowdown timer (older models).
Power switch malfunction.
Pressure reducing valve malfunction or needs cleaned
(direct or regenerated units only).
Low or no steam supply to unit (direct or regenerated
units only).
Steam trap malfunction.
Blocked steam injector ports. (Open door, press door
switch button and verify good steam flow into
compartment.)
Steam solenoid valve not fully opening or blocked.
Steam intake shut-off valve closed or out of adjustment.
See INTAKE SHUT-OFF VALVE ADJUSTMENT.
Cycling pressure switch malfunction or needs
Steam output low or slow cooking.
Unit leaks water.
Boiler water level too high.
Boiler does not fill.
Timer motor does not run.
Door not closing properly.
Door won’t open. Latch won’t release. See DOOR ASSEMBLY.
Buzzer not operating.
adjustment.
Steam header line (supply) blockage.
Heavy amount of condensate in the pressure controls
steam supply line.
Pressure relief valve leaking.
Steam supply lines leaking badly.
Steam trap malfunction.
Loose water, steam or drain line connections (top or
base).
Boiler hand hole gasket not sealing.
Leak at gauge glass.
Fill solenoid does not shut off.
High level probe dirty (open circuit).
Water level control malfunction.
Water supply not on.
Fill solenoid not opening or plugged.
Water level control malfunction.
Door open or door switch inoperative.
Timer not getting power.
Timer motor inoperative.
Door latch assembly malfunction or out of adjustment.
See DOOR ASSEMBLY.
Striker adjustment. See DOOR ASSEMBLY.
Timer malfunction.
Buzzer malfunction.
F24627 (0916) Page 80 of 82
VSX BOILER BASE SERIES CONVECTION STEAMERS - TROUBLESHOOTING
SYMPTOM POSSIBLE CAUSES
Burner won’t light.
Burner won’t stay lit.
Pilot not lit or goes out.
Spark Ignitor not sparking.
Gas not on.
Ignition control module reset switch in the OFF position
or malfunctioning.
Ignition module not receiving power. Check ignition
module transformer for 24VAC output to module on
automatic ignition systems.
Unit not properly grounded and/or polarity of incoming
power is incorrect on automatic ignition systems.
Low incoming gas pressure. See Manifold Pressure
Adjustment.
Ignition module malfunction.
Gas combination control valve malfunction.
Boiler not filling. Check fill solenoid for power, clogging or
malfunction.
Water level control malfunction.
Water too ”pure” for probes to properly conduct
electricity.
High limit thermostat open (if equipped).
High limit pressure switch open.
Cycling pressure switch open or set too high. Unit is
cycling on high limit. See PRESSURE SWITCHES .
Gas pressure low. See Manifold Pressure Adjustment.
Ignition module malfunction.
Check gas orifice for obstruction.
Gas not on.
Low incoming gas pressure.
Check thermopile millivolts.
Pilot going out due to drafts, excess steam from drain or
unit not level. Improper venting can direct the pilot flame
away from thermopile or flame sensor.
Pilot not adjusted correctly. See Pilot, Thermocouple,
Gas Combination Control Valve, Main Burners.
Burners ignite too violently. Check gas pressure to the
unit. See Manifold Pressure Adjustment”.
If auto ignition and no sparking - ignition module
malfunction.
Wrong pilot assembly used.
Incorrect spark gap setting. See Automatic Ignition
Systems.
Poor ground between pilot bracket and burner.
Loose, broken or damaged lead wires (including ground)
from ignition module to ignitor.
Ignitor boot on ignition cable loose, damaged or missing
causing excessive ignition voltage leakage.
Page 81 of 82 F24627 (0916)
VSX BOILER BASE SERIES CONVECTION STEAMERS - TROUBLESHOOTING
SYMPTOM POSSIBLE CAUSES
Ceramic flame rod insulator on ignitor cracked or
damaged from extreme heat.
Ignition module not receiving power.
Ignition module malfunction.
F24627 (0916) Page 82 of 82
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