Vulcan VSX24D Service Manual
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)
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