SERVICE MANUAL
VHX BOILER BASE SERIES
HIGH EFFICIENCY GAS
STEAMERS
VHX24G
VHX24G5 ML-126590
MHB24G ML-114954 (BASE ONLY)
ML-114795
VHX24G SHOWN
- NOTICE -
This Manual is prepared for the use of trained Vulcan Service
Technicians and should not be used by those not properly
qualified. If you have attended a Vulcan Service School for this
product, you may be qualified to perform all the procedures
described in this manual.
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.
Reproduction or other use of this Manual, without the express
written consent of Vulcan, is prohibited.
A product of VULCAN-HART
LOUISVILLE, KY 40201-0696
F24700 (October 2001)
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VHX SERIES STEAMERS
Air Pressure Switch Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Gas Pilot Pressure Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Gas Manifold Pressure Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Ignition Control Module Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Cooking Compartment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Intake Shut-Off Valve Adjustment (Steam Flow) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Door Sealing Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Door Latch Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
ELECTRICAL OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Water Level Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Low Level Cut-Off & Differential Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Auxiliary Low Level Cut-Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Relay Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Board Layout and LED Legend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Boiler Operational Status (LED Indicator) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Sequence of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
New Style Controls - Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Old Style Controls - Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Cooking Compartment Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Models Built After 5/25/00 (New Style Boiler Controls) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Models Built Before 5/25/00 (Old Style Boiler Controls) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Cooking Compartment Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Models Built After 5/25/00 (New Style Boiler Controls) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Models Built Before 5/25/00 (Old Style Boiler Controls) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Cooking Compartment Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
CONDENSED SPARE PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
© VULCAN 2001
Page 3 of 68
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VHX SERIES STEAMERS - GENERAL
GENERAL
Model Designations
INSTALLATION
Refer to the Installation and Operation Manual for
detailed installation instructions.
MAINTENANCE
Refer to the Installation and Operation Manual for
specific maintenance instructions.
CLEANING
Refer to the Installation and Operation Manual for
specific cleaning instructions.
INTRODUCTION
Boiler Code Descriptions
Vulcan-Hart incorporates redundant controls in
compliance with the CSD-1 controls and safety
devices for boiler construction on these High
Efficiency Steam models. A Description of the code
is listed below.
Steam Cooking
Convection cooking in pressure-less steaming
compartments 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 compartments on the VHX series
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.
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 - (1) dual
function water level cycling and low level cut off
control and (1) single function low water level cut-off
control (Aux LLCO) and a high pressure relief switch
in conjunction with a mechanical pressure relief
valve. Additionally, both circuits have individual
indicator lights for low water and high pressure that
will illuminate for a visual verification of the
shutdown mode.
Compartment Pan Capacity
PAN
DEPTH
(INCHES)
NUMBER OF PANS
PER COMPARTMENT
MODEL
CSD-1 construction requires operator intervention in
the event of a shutdown. The indicator lights show
the operator which safety system was shutdown.
2
4.0
2.5
1.0
4.0
2.5
1.0
VHX24G
3
6
3
VHX24G5
5
10
Pan Size 12" x 20"
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VHX SERIES STEAMERS - GENERAL
Boiler Control Styles
VHX Steamers manufactured using the old style boiler controls ended on 5/19/00. Steamers that were in stock at
the time of the boiler control changeover were removed and equipped with the new style controls without
recording the serial number for tracking.
Refer to the pictures below to differentiate between the old style and new style boiler controls.
Page 5 of 68
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VHX SERIES STEAMERS - GENERAL
WATER CONDITIONING
SPECIFICATIONS
Furnishing the boiler with treated 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 the inside of the boiler, heating elements, and
water level sensors. Because of the high
Water Supply
The fact that a water supply is potable is no
guarantee that it is suitable for steam generation.
The supply connection to the steam generator
should be “treated” water and must be within the
guidelines listed below. For drain water cooling only,
an “untreated“ water supply connection should be
used.
Supply pressure should be
In line strainer for supply line
Supply connection
Total dissolved solids (TDS)*
Total alkalinity
20-60 psig
(Not Supplied)
cold
temperature of these surfaces, the precipitated
minerals bake onto them and become very difficult
to remove.
less than 60 ppm
less than 20 ppm
less than 13 ppm
less than 30 ppm
7 to 8
This may cause several problems:
1. Reduced heat transfer efficiency.
2. Premature heating element failures.
3. False readings from water level sensors.
Silica
Chloride
PH factor
(*17.1 ppm = 1 grain of hardness)
These problems are common to any manufacturer's
steamer regardless of design, but they can all be
minimized by furnishing the boiler with treated
water.
Electrical
Voltage - 120/60/1
Amps - 3.0 (max)
Other factors affecting steam generation are iron
content, amount of chlorination and dissolved
gases.
The desired water properties can best be achieved
by using a properly maintained water treatment
system.
Boiler Pressure
Operating - 8 to 10 psi
Maximum - 15 psi
The water level probes in the boiler use ions in the
water to detect the water level. Do not use fully
demineralized or de-ionized water since it is
"non conductive" and the water level can not be
detected.
The use of strainers or non approved filters will not
remove minerals from the water.
Water supplies vary from state to state and from
locations within a state. Therefore, a water
treatment specialist should 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 treatment system,
which have developed a heavy scale build up,
should be cleaned before using the system.
F24700 (October 2001)
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VHX SERIES STEAMERS - GENERAL
Gas Supply
MODEL
LINE PRESSURE
(INCHES W.C.)
MANIFOLD
PRESSURE
(INCHES W.C.) (INCHES W.C.)
PILOT
PRESSURE
INPUT
(BTU/HR)
NATURAL
MINIMUM
PROPANE
MINIMUM
MAXIMUM
ALLOWED
NAT.
PROP. NAT. PROP. NAT. PROP.
RECOMMENDED RECOMMENDED
200,000 200,000
270,000 270,000
200,000 200,000
270,000 270,000
200,000 200,000
270,000 270,000
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
7.0
7.0
7.0
7.0
7.0
7.0
11.0
11.0
11.0
11.0
11.0
11.0
VHX24G
VHX24G5
MHB24G
14.0
1. Output Boiler Horsepower (BHP): 4.3 BHP for 200,000 BTU; 5.5 BHP for 270,000 BTU.
2. Input BTU/HR difference is based on gas orifice size and air orifice size.
NOTE
:
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
Temperature meter and thermocouple.
Special
The recommended deliming chemical for the water treatment system in use, for deliming of the boiler.
Contact Vulcan Authorized Service Centers.
Heat Exchanger Gasket (joint sealant strip, Teflon) P/N 854058-1.
Page 7 of 68
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VHX SERIES STEAMERS - OPERATION
STEAMER OPERATION
2) If pilot burner flame is not
CABINET BASE BOILER
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 main burner lighting
cycle again.
Ensure that all utility connections to the steamer
have been made and are turned ON and that the
knob on the main gas valve is in the ON position.
The VHX Series steamers are CSD-1 compliant and
are equipped with amber colored lights on the boiler
control panel for High Pressure and Low Water level
that illuminate and stay on until the boiler is full and
the manual reset switch pressed.
New Style Controls - Power to the
Pilot gas valve operates on a "timer"
circuit allowing gas flow to the pilot
for approximately 15 seconds, during
ignition trial, then turns off.
1. Turn power switch ON.
D. Main gas valve opens, burner ignites and
begins to heat the water in the boiler. After
approximately 15 minutes, steam should
be present for cooking product. Observe
that the boiler pressure gauge indicates a
steam pressure of 8-10 psi before the
burner shuts OFF.
A. Amber colored lights on the boiler control
panel for High Pressure and Low Water
level will illuminate. and stay on until the
boiler is full and the reset switch is
pressed.
B. Water will begin filling the boiler and the
blowdown solenoid valve will close. The
boiler should fill, in four to eleven minutes.
3. The cycling pressure switch will maintain steam
pressure in the boiler by cycling the main
burner ON and OFF.
C. As water fills the boiler, observe water
level gauge glass to verify that water is in
boiler. See "WATER LEVEL GAUGE
ASSEMBLY" in "COMPONENT
COOKING COMPARTMENT
CONTROLS
FUNCTION” and COMPONENT
LOCATION “ under "REMOVAL AND
REPLACEMENT OF PARTS".
When the steam pressure in the cooking
compartment manifold reaches approximately 3 psi,
the cooking compartment pressure switch closes,
suppling power to the other cooking compartment
controls. The ready lights will illuminate and 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
controls.
D. Once the water in the boiler reaches the
minimum level, the green ready light on
the boiler control panel will illuminate.
NOTE: If the fill has stopped, one visible inch
of water should be in the gauge glass.
2. Press the reset switch on the boiler control
panel.
A. Low water level safety circuit will be reset
and the Low Water level light (amber) will
turn off.
NOTE: On initial startup, if a cooking timer is set
immediately after the ready light comes on, steam
solenoid chattering will be heard (oil canning) and
the ready lights will flash for several seconds. This
condition is caused by the manifold steam 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. After the
steam pressure passes approximately 4 psi this
condition subsides. During normal operation, this
condition will not be seen.
B. High pressure safety circuit will be reset
and the High Pressure light (amber) will
turn off.
C. Sparking will begin three seconds later to
light the pilot burner.
1) If the pilot burner lights, a signal is
sent back through the ignition cable
indicating the presence of pilot burner
flame and sparking stops.
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VHX SERIES STEAMERS - OPERATION
1. With both timer knobs at the off position, open
BOILER BLOWDOWN AND
STEAMER SHUT OFF
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.
Turn the steamer off at least once daily to blowdown
the boiler. This will aid in the removal of sediment
and scale build-up in the boiler.
NOTE: Boiler should be with-in normal operating
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.
pressures.
1. Turn power switch OFF.
2. Boiler blowdown sequence starts.
A. The blowdown/drain solenoid valve will be
de-energized and the boiler will begin to
drain.
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.
B. The cold water condenser solenoid will
operate, as needed, to condense steam
and to cool the water going into the drain.
5. When timer knobs reach "0", buzzers will
sound, steam generation will cease, cooking
lights will go off and ready lights will come on.
To silence buzzers, turn timer knobs to off
position.
6. During idle time or 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.
A. Boiler blowdown starts.
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VHX SERIES STEAMERS - COMPONENT FUNCTION
COMPONENT FUNCTION
CABINET BASE BOILER CONTROLS
Power Switch (ON/OFF) . . . . . . . . . When turned ON, supplies power to the control circuit.
Reset Switch (Manual) . . . . . . . . . . Resets the low water level safety circuit on initial startup or the
occurrence of a low water condition and allows the boiler to fill with
water. Also, resets the high pressure level safety circuit on initial startup
or the occurrence of a high pressure condition and allows the gas
ignition cycle to start.
Boiler Fill Solenoid 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 . . . . . . . . . . . . . . . . . Allows cold water flow into the boiler blowdown drain box to condense
steam and cool the hot water before its discharge into the drain.
Blowdown/Drain
Solenoid Valve . . . . . . . . . . . . . . . . . A normally open valve (N.O.) that closes to allow boiler to fill and
pressurize when power switch is turned ON and opens when power
switch is turned off to blowdown and drain the boiler. This valve is
plumbed into the drain line of the boiler.
Cycling Pressure Switch . . . . . . . . . Controls boiler pressure between prescribed limits by turning the heat
source on and off.
High Limit Pressure Switch . . . . . . Protects the boiler from pressures above 15 psi by removing power from
the heating circuit. This pressure setting is higher than the cycling
pressure switch in order to turn off the heat source before the boiler
pressure reaches its limit. After the pressure drops below approximately
12psi, press the rest switch of the front control panel to rest the safety
circuit.
Main Water Level Control . . . . . . . . A dual functioning control that allows water to fill and maintain the
proper level in the boiler providing differential water level control; and
shuts off the main gas valve if the water level drops too low providing
low level cut-off protection. The water level control works by using three
different probe lengths to monitor the water level. The probes consist of
a high level (HL), low level (LL) and low water cut-off (LLCO).
Auxiliary Water Level Control . . . . . A back up to the low level cut-off on the main control. Protects the boiler
and heating system components from a low water cut-off condition by
opening the 24VAC voltage path to the heating system circuit. Also,
energizes the low water "light" on the front control panel.
Transformer . . . . . . . . . . . . . . . . . . . Provides 24VAC power to ignition control module and heating circuit.
Ignition Control Module . . . . . . . . . Controls and monitors gas heating. Energizes pilot valve coil to supply
gas to pilot, generates spark to ignite gas at the pilot, monitors the
presence of flame and energizes the main and pilot valve coils on the
main gas valve upon a call for heat.
Main Gas Valve . . . . . . . . . . . . . . . . A gas solenoid valve that opens to allow gas flow to the main burner
after the successful ignition of the pilot burner when a call for heat is
made.
Pilot Gas Valve . . . . . . . . . . . . . . . . A gas solenoid valve that opens to allow gas flow to the pilot to ignite the
main burner when a call for heat is made. The valve is energized by a
time delay circuit on the relay board during ignition trial for
approximately 15 seconds. New style controls only.
Combustion Blower . . . . . . . . . . . . Provides forced air to the gas/air mixture for gas pilot and main burner
combustion.
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VHX SERIES STEAMERS - COMPONENT FUNCTION
Relay Board . . . . . . . . . . . . . . . . . . . Provides a centralized location for wire harness connections and power
transfer through board relays (K1-K7) to the steamer controls. Also,
provides a condition or component troubleshooting indicator by utilizing
seventeen LED’S on the board to represent the status of the condition or
component in the operation sequence. For an LED legend, see "RELAY
BOARD" under "ELECTRICAL OPERATION". New style controls only.
NOTE: The relay’s below are mounted on the relay board and are not individually replaceable.
K1 Relay . . . . . . . . . . . . . . . . . . . . . . Energized when Aux LLCO is satisfied and turns ready light (green) ON
if high limit pressure switch is closed. Also, K1 allows K3 to be energized
when the reset switch is pressed.
K2 Relay . . . . . . . . . . . . . . . . . . . . . . Energized when high limit pressure switch is closed (high limit pressure
condition satisfied). When K1 & K2 are energized, the ready light (green)
will be ON.
K3 Relay . . . . . . . . . . . . . . . . . . . . . . When Aux LLCO is satisfied and the manual reset switch is activated,
K3 is energized. When K3 is energized, turns water error light OFF and
allows the ignition sequence to begin. K3 must be energized for ignition
sequence to begin.
K4 Relay . . . . . . . . . . . . . . . . . . . . . . Energized when K2 contacts are closed and manual reset switch is
activated. When K4 is energized, the high pressure light is OFF. When
K3 and K4 are both energized, power to the ignition system is supplied.
K5 Relay . . . . . . . . . . . . . . . . . . . . . . Energized when operating conditions are met and reset switch is
activated. Provides power to start combustion blower.
K6 Relay . . . . . . . . . . . . . . . . . . . . . . Energized by time delay circuit for approximately 15 seconds. When K6
and K7 are energized, power is supplied to the pilot gas valve.
K7 Relay . . . . . . . . . . . . . . . . . . . . . . Energized when pilot voltage (PV) from the ignition module is present.
Also used in the time delay circuit.
Pilot . . . . . . . . . . . . . . . . . . . . . . . . . Ignites to light the main burner upon a call for heat.
Main Burner . . . . . . . . . . . . . . . . . . . Heats the water in the boiler to generate steam.
Water Level
Gauge Assembly . . . . . . . . . . . . . . . Permits a visual confirmation the water level is being maintained in
boiler during operation. The correct water level is approximately one
visible inch in the glass. The manual valves at the top and bottom of this
assembly must be fully open and only closed if the glass tube is
damaged.
Water Inlet Valve (manual) . . . . . . . The water inlet valve is used to stop water flow to the steamer when the
steamer is being serviced. This valve should remain open during normal
operation.
Inline Water Strainer . . . . . . . . . . . . A "Y" strainer is installed upstream of the blowdown solenoid valve to
prevent foreign matter from becoming lodged in the valve. A strainer
(not supplied) should also be installed in the water supply line to prevent
foreign matter from becoming lodged in the fill or cold water condenser
solenoid valves and to keep unwanted particles out of the system.
Pressure Relief Valve . . . . . . . . . . . A mechanical device that opens to relieve steam pressure in the boiler if
the pressure exceeds 13 psi.
High Pressure Relief Valve . . . . . . . A back-up mechanical device that opens to relieve steam pressure in
the boiler if the pressure exceeds 15 psi.
Descaler . . . . . . . . . . . . . . . . . . . . . . Hangs below the water level inside the boiler and is used to help control
boiler surface scaling. Two descalers are used in each boiler.
Boiler Pressure Gauge . . . . . . . . . . Indicates the amount of steam pressure in the boiler.
Steam Header Assembly . . . . . . . . . Main steam supply line from the boiler to the steam header inlet in the
cooking control compartment.
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VHX SERIES STEAMERS - COMPONENT FUNCTION
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 the compartment pressure switch setting to close the N.O. contacts.
Ready Light (Green) . . . . . . . . . . . . When lit, indicates steamer is ready to cook.
Cooking Light (Red) . . . . . . . . . . . . When lit, indicates steamer is in a cooking cycle.
Cooking Timer . . . . . . . . . . . . . . . . . Use 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.
Buzzer . . . . . . . . . . . . . . . . . . . . . . . Signals end of a cook cycle, must be turned off manually.
Door Switch . . . . . . . . . . . . . . . . . . . Removes electrical power to the timer. If time is dialed on the cooking
timer and compartments are steaming, removes power to the steam
solenoid valve when the compartment door is opened.
Steam Solenoid Valve . . . . . . . . . . . When energized, opens to allow steam into the cooking compartment
(normally closed valve).
Compartment Pressure Switch . . . . Supplies power to the controls only after the steam pressure rises above
approximately 3 psi to close the compartment pressure switch. The
switch remains closed as long as steam pressure stays above this
pressure.
Manifold Pressure 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.
Steam Supply Manifold . . . . . . . . . . Main steam supply line from the boiler for each cooking compartment.
Supplies steam up to the steam solenoid valve.
Intake Shut-Off Valve . . . . . . . . . . . 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 (STEAM FLOW)" in
“SERVICE PROCEDURES AND ADJUSTMENTS".
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
REMOVAL AND REPLACEMENT OF PARTS
COMPONENT LOCATIONS
Cabinet Base Boiler Controls
Page 13 of 68
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
Cabinet Base Boiler Controls Continued
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
Cooking Compartment Controls
WATER LEVEL CONTROLS
(MAIN OR AUXILIARY LLCO)
RELAY BOARD
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
1. Open the cabinet base door.
1. Open the cabinet base door.
2. Remove the cover from the main control box to
access the relay board. Refer to "CABINET
BASE BOILER CONTROLS" under
2. Remove the cover from the pressure switch
control box to access the water level controls.
Refer to "CABINET BASE BOILER
CONTROLS" under "COMPONENT
LOCATIONS" in "REMOVAL AND
"COMPONENT LOCATIONS" in "REMOVAL
AND REPLACEMENT OF PARTS".
3. Disconnect all lead wires from the board.
REPLACEMENT OF PARTS".
4. Compress the locking tab on the board
mounting "standoffs" and remove the relay
board.
3. Disconnect lead wires from the board being
replaced.
4. Compress the locking tab on the board
mounting "standoffs" and remove the water
level control.
5. Reverse procedure to install and check for
proper operation.
5. Reverse procedure to install and check for
proper operation.
Page 15 of 68
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
1) Remove the mounting screws on the
WATER LEVEL GAUGE
ASSEMBLY
back side of the control box and lift
out the pressure switch. Proceed to
step 5.
B. High limit control - disconnect the lead
wires.
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
5. Disconnect the pressure fittings at the bottom
of the switch.
6. Preset the new pressure switch to the
approximate cut-out (OFF) and cut-in (ON) set
points before installing. Refer to "PRESSURE
SWITCHES" in "SERVICE PROCEDURES
AND ADJUSTMENTS".
1. Open the cabinet base door and remove the
right side panel.
2. Close the valve at the top and at the bottom of
the gauge assembly.
7. Reverse procedure to install.
3. Unscrew the packing nuts at the top and bottom
of the glass tube.
8. Adjust the pressure switch(s) final set points as
outlined under "PRESSURE SWITCHES" in
"SERVICE PROCEDURES AND
4. Slide the glass tube upwards until the bottom of
the tube is clear of the fitting and lift it out.
ADJUSTMENTS".
NOTE: Clean tube if dirty or clogged and replace if
damaged or broken.
BOILER ASSEMBLY
NOTE: Do not over tighten the packing nuts or
gauge glass may break.
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
5. Install the tube using new sealing washers.
6. Open the top and bottom valves.
7. Turn the power switch ON and allow boiler to
come up to pressure.
WARNING: SHUT OFF THE GAS BEFORE
8. Check gauge glass for water/steam leaks and if
necessary, gradually tighten packing nuts until
leak stops.
SERVICING THE UNIT.
WARNING: 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.
PRESSURE SWITCHES
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
1. Blowdown the boiler and, if necessary, allow to
cool.
2. Disconnect the steam supply line, power leads
and drain lines from the cooking compartment
top to the boiler base.
1. Open the cabinet base door and remove the
left side panel.
3. Refer to "HEAT EXCHANGER" and perform
steps 3 through 12A.
2. Remove the cover from the pressure switch
control box to access the pressure switches.
Refer to "CABINET BASE BOILER
CONTROLS" under "COMPONENT
LOCATIONS" in "REMOVAL AND
4. Remove bolts securing the boiler to frame.
5. Drain any remaining water from the boiler.
A. The suggested methods are:
REPLACEMENT OF PARTS".
1) Where the drain line exits the boiler
on the lower left side, separate the
drain line union.
3. The pressure switches are located at the
bottom of the box. The pressure switch on the
left is the cycling or primary control; the one on
the right is the high limit control.
2) Remove the access panel between
the boiler and the cooking
compartment on the right side.
4. If replacing:
3) Disconnect the steam supply hose
from the cooking compartment steam
manifold.
A. Cycling control - remove cover from
pressure switch and disconnect the lead
wires.
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
a. From the bottom right side, raise
the boiler two to three inches so
it tilts to the left. When the
remaining water has drained out,
lower the boiler before.
WARNING:
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.
proceeding.
NOTE: Gas combination control valves are not
serviceable and should not be disassembled. Once
the problem has been isolated to this component,
replace it. Do not attempt to repair the assembly.
B. Remove the drain/scale clean-out plug
from the bottom of the boiler.
6. Slide the boiler forward and remove it from
base frame.
1. Open the cabinet door to access the Pilot gas
valve.
7. Install a new boiler and secure it to frame.
2. Disconnect the lead wires.
8. Refer to "HEAT EXCHANGER" and perform
steps 13 through 15.
3. Remove pilot gas tubing from the top of the
valve (outlet side).
9. Reconnect all steam, water, drain and power
connections and check for proper operation.
4. Remove the valve from the gas supply piping.
5. Reverse procedure to install and adjust pilot
pressure as outlined under "GAS PILOT
PRESSURE ADJUSTMENT" in "SERVICE
PROCEDURES AND ADJUSTMENTS".
BOILER FILL AND COLD WATER
CONDENSER SOLENOID VALVES
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
MAIN GAS VALVE
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
1. Turn off the water supply to the steamer.
2. Open the cabinet base door and remove the
cover from the pressure switch control box to
access the solenoid valves. Both solenoid
valves are located side by side at the rear of
the box with the boiler fill near the bottom and
the cold water condenser near the middle.
Refer to "CABINET BASE BOILER
WARNING: SHUT OFF THE GAS SUPPLY
BEFORE SERVICING THE UNIT.
WARNING: 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.
CONTROLS" under "COMPONENT
LOCATIONS" in “REMOVAL AND
REPLACEMENT OF PARTS”.
NOTE: Gas combination control valves are not
serviceable and should not be disassembled. Once
the problem has been isolated to this component,
replace it. Do not attempt to repair the assembly.
3. Disconnect the power lead wires from the
solenoid valve being serviced.
4. Disconnect the water lines for the valve being
serviced and remove the valve.
1. Open the cabinet base door to access the main
gas valve.
5. Reverse procedure to install.
2. Disconnect the lead wires.
PILOT GAS VALVE
3. Separate the union above the gas valve (outlet
side).
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
4. Remove the valve from the gas supply piping.
5. Reverse procedure to install and adjust
manifold pressure as outlined under "GAS
MANIFOLD PRESSURE ADJUSTMENT" in
"SERVICE PROCEDURES AND
WARNING: SHUT OFF THE GAS BEFORE
SERVICING THE UNIT.
ADJUSTMENTS".
Page 17 of 68
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
BURNER HEAD ASSEMBLY
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
WARNING: SHUT OFF THE GAS SUPPLY
BEFORE SERVICING THE UNIT.
1. Remove the pressure gauge tubing and power
cable from the rear of the control panel then
remove the panel.
2. Disconnect the spark ignition cable from the
ignitor terminal.
3. Disconnect pilot gas tubing from the air
pressure switch tee.
3. Remove the four nuts from the burner tube
assembly then slowly pull the assembly straight
out from the heat exchanger.
4. Separate the union above the main gas valve
and remove the gas valve piping assembly.
NOTE: Removal of the gas valve piping assembly
assumes the use of a gas line quick connect or
union at the gas supply inlet to the steamer.
5. Remove the screws from the burner head
assembly end plate and pull the assembly out
from the complete burner assembly.
6. Reverse procedure to install and check for
proper operation.
COMPLETE BURNER
ASSEMBLY
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
WARNING: SHUT OFF THE GAS SUPPLY
BEFORE SERVICING THE UNIT.
1. Refer to steps 1 through 4 under "BURNER
HEAD ASSEMBLY".
CAUTION: Use care while removing as to not
damage the ceramic insulation surrounding the
burner.
2. Remove the four nuts from combustion blower
mounting flange and remove blower from
burner tube assembly.
4. Reverse procedure to install and check for
proper operation.
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
NOTE: Removal of the gas valve piping assembly
assumes the use of a gas line quick connect or
union at the gas supply inlet to the steamer.
HEAT EXCHANGER
WARNING: SHUT OFF THE GAS BEFORE
SERVICING THE UNIT.
8. Remove the four nuts from combustion blower
mounting flange and remove blower from
burner tube assembly.
WARNING: 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.
1. Blowdown the boiler and, if necessary, allow to
cool.
2. Disconnect the electrical power to the machine
at the main circuit box. Place a tag on the
circuit box indicating the circuit is being
serviced.
3. Remove the pressure gauge tubing and power
cable from the rear of the control panel then
remove the panel.
4. Disconnect the electrical lead wires exiting the
boiler control box from:
A. Auxiliary LLCO probe (Orange).
B. Burner ground (green).
9. Remove the four bolts connecting the
horizontal flue (left of boiler) to the flue
"transition" piece.
C. Air pressure switch (yellow & yellow/white
stripe).
D. Main gas valve (purple & grey).
E. Pilot burner valve (red & grey).
F. Spark ignition cable.
5. Remove bolts securing the boiler control box
(front) to the base frame.
A. Lift up on left side of box and slide out.
6. Disconnect pilot gas tubing from the air
pressure switch tee.
A. Separate the horizontal flue from flue
"transition" piece, leaving the horizontal
flue in place.
10. Remove the four nuts from the complete
burner tube assembly then slowly pull the
assembly straight out from the heat exchanger.
CAUTION: Use care while removing as to not
damage the ceramic insulation surrounding the
burner.
11. Remove the flue "transition" piece from the
heat exchanger.
7. Separate the union above the main gas valve
and remove the gas valve piping assembly.
Page 19 of 68
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
12. For clearance of the heat exchanger only,
13. To install heat exchanger:
remove the drain nut (petcock) and the lower
adjustment knob from the water level gauge.
A. Clean the mating surfaces on the heat
exchanger and boiler.
A. Remove the remaining bolts on the heat
exchanger then pull heat exchanger
straight out from the boiler.
B. Install a new gasket on the boiler side of
the mounting flange.
C. Insert the heat exchanger back into the
boiler and line up the mounting holes
being careful not to disturb gasket.
D. Attach a 2" C-Clamp between the heat
exchanger mounting flange and the boiler
side mounting flange. Tighten clamp only
enough to allow starting of bottom bolt into
mounting hole.
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
NOTE: It may be necessary to use two clamps
to draw the bottom of the heat exchanger close
enough to be clamped. Start one clamp at a 3
o’clock position then install other clamp near
the bottom. Once the bolts are tight enough, C-
Clamp will fall away.
E. Install two bolts at the bottom and two
bolts at the top on the heat exchanger
flange and tighten the bolts a few turns at
a time. Starting with the bottom bolts,
tighten the bolts in an alternating pattern
between the bottom and top for a flush
mounting of the heat exchanger flange
and an even compression of the gasket.
NOTE: If a bolt is not threading in properly by
hand, clean out the threads with the proper size
tap.
F. Once those bolts are tight, install the two
bolts to the left and the two bolts to the
right on the heat exchanger flange. On the
left side, be sure to install the rectangular
flue gas plate then tighten the bolts in an
alternating pattern.
15. Starting at step 12, reverse procedure to install
the remaining components.
16. Check for water leaks and proper operation.
COOKING COMPARTMENT
DOOR(S)
Removal
1. Remove top cover.
2. Open the door.
3. Pull hinge rod up.
4. Reverse the procedure to install, making sure
the door bushings are in place.
Gasket
1. Open the door.
2. Remove screws from the gasket plate.
3. Pull the gasket plate out from the door housing
and remove the gasket.
4. Position the new gasket on the gasket plate
and reverse the procedure to install. Adjust the
door as outlined in "DOOR SEALING
ADJUSTMENT" under "COOKING
COMPARTMENT".
14. To install flue "transition" piece:
A. Clean the mating surfaces on the
"transition" piece and the heat exchanger
face.
B. Install new gasket on the "transition" piece
then secure to the heat exchanger using
the remaining bolts.
NOTE: Do not over tighten gasket plate screws as
this will compress the gasket excessively and
interfere with proper door sealing.
NOTE: Damage to the gasket sealing surface, such
as nicks or cuts, will cause steam leakage.
Page 21 of 68
F24700 (October 2001)
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VHX SERIES STEAMERS - REMOVAL AND REPLACEMENT OF PARTS
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.
5. Reverse procedure to install.
Latch Assembly
Handle
1. Open the door.
1. Open the door.
2. Remove screws from the top and bottom of the
door.
2. Remove screws from the top and bottom of the
door.
3. Pull the inner door panel out from the door
housing with the gasket plate and gasket still
attached.
3. Pull the inner door panel out from the door
housing with the gasket plate and gasket still
attached.
4. Remove the screws from the side edge of the
door that secure the latch mechanism and
remove the latch from the door.
NOTE: When installing, the latch lever must rest on
top of the handle latch screw.
5. Reverse procedure to install.
4. Remove the nuts and spacers from the handle
screws and remove the handle from the door.
F24700 (October 2001)
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
SERVICE PROCEDURES AND ADJUSTMENTS
WARNING: CERTAIN PROCEDURES IN THIS SECTION REQUIRES 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, ATTACH TEST
EQUIPMENT AND REAPPLY POWER TO TEST.
A. Remove the strainer clean out plug, turn
BOILER
the steamer on and allow the boiler "fill
water" to flush-out the drain line. Turn the
steamer off, remove the cap and strainer
screen and clean, if necessary, before
replacing the screen and clean-out plug.
Inspection
It is recommended the boiler be inspected for
excessive lime scale build up in a time frame
dependant on the quality of the local water supply
and steamer usage. In hard water areas or for
steamers heavily used, a frequent interval should be
used. This inspection consists of an internal
examination and cleaning of the boiler, an
examination of the two hanging descalers, and for
lime build up on the water level probes. Also, a
check of all boiler controls, including the pressure
switches.
7. Inspect condition of the descalers as outlined
under "DESCALER (Cathodic Protector)" in this
section, and replace if necessary.
8. Install a new gasket and replace the burner
assembly and heat exchanger by reversing the
removal procedure from step 2.
9. Delime the boiler as outlined under
"DELIMING" in this section.
Deliming
Periodic service must be performed as outlined in
these procedures. See “WATER CONDITIONING”
under “GENERAL”.
Boiler deliming should be performed in a time frame
dependant on the quality of the local water supply
and steamer usage. In hard water areas or for
steamers heavily used, a frequent interval should be
used. See “WATER CONDITIONING” under
“GENERAL”.
Clean-Out
1. Turn power switch OFF.
A. Boiler should automatically start
blowdown/drain cycle.
On steamers using a water treatment 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.
2. Remove the burner assembly and heat
exchanger as outlined under "HEAT
EXCHANGER" in "REMOVAL AND
REPLACEMENT OF PARTS".
If a water treatment system is not used, follow the
instructions for deliming the boiler as outlined in the
steps below.
NOTE: Access to the interior of the boiler through
the hand hole cover is very limited on this model
and is recommended to be removed for deliming
purposes only.
1. Turn power switch OFF.
3. Remove old descalers (cathodic protectors).
4. With a wire brush or equivalent:
A. Boiler should automatically start
blowdown/drain cycle.
2. Remove hand hole plate and gasket (top front)
from the boiler by removing the nut and clamp,
then tap the cover lightly to free it. Hold the
stud in the plate while tapping to prevent the
plate from dropping into boiler.
A. Dislodge and remove all loose scale from
boiler shell. The loose material must be
scooped from the boiler or flushed through
the washout drain.
B. Remove all loose scale form the heat
exchanger.
3. Clean the mating surfaces of the hand hole
opening and plate.
C. Clean the mating surfaces of the heat
exchanger and boiler.
4. Delime the boiler:
A. If the boiler was delimed through a water
treatment system, proceed to step 7.
5. Check probe housing and water level probes
for scale build up and clean as necessary.
Refer to "WATER LEVEL CONTROLS TEST".
B. If the boiler has not been delimed,
proceed to step 5.
6. Check the drain line exiting the boiler for
obstructions.
Page 23 of 68
F24700 (October 2001)
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
WARNING: READ AND FOLLOW THE
INSTRUCTIONS FOR THE DE-LIMING CHEMICAL
BEING USED. USE PLASTIC OR RUBBER
GLOVES TO AVOID SKIN CONTACT. IF THE
CHEMICAL COMES IN CONTACT WITH SKIN,
RINSE WITH CLEAN WATER.
5. Mix deliming solution according to the
instructions for the chemical being used.
NOTE: Boiler water capacity is approximately seven
gallons.
NOTE: If deliming solution comes in contact with
steamer components, lightly rinse off with clean
water.
A. Turn OFF water supply.
B. Turn power switch ON to close the drain
valve.
C. Pour deliming solution into the boiler shell.
The descaler materials serve as a sacrificial
"Anode" and "Cathode" combination that chemically
reacts with the contents of the boiler to meet the
three objectives outlined above.
6. Install a new gasket on the hand hole plate then
position and tighten the plate to the boiler.
7. Ensure cooking compartment timers are OFF.
If the coiled wire has eroded away or if the
cylindrical core of the descaler has eroded away to
approximately half its original diameter, a new
descaler should be installed. The size of a new
descaler is approximately: 1 3/8" diameter and 3
3/4" long at the core.
8. Turn power switch ON and open water supply
valve.
9. Allow the boiler to reach operating pressure
and run for 90 minutes or per the instructions
for the deliming chemical in use.
NOTE: While the diameter of the descaler
decreases through erosion, the length of the
descaler will increase. If the descaler has increased
to a length that is touching the bottom of the boiler
shell, the descaler should be replaced.
A. Turn power switch OFF and allow the
boiler to completely drain.
B. Turn power switch ON to refill boiler and
allow to heat until fully pressurized.
10. Steps 9A and 9B must be repeated three times
The descalers are accessible through the "heat
exchanger" opening in the boiler only. For removal
of the heat exchanger refer to "HEAT
EXCHANGER" under "REMOVAL AND
REPLACEMENT OF PARTS".
to thoroughly rinse the boiler.
11. Steamer is now ready for normal operation.
Descaler (Cathodic Protector)
Two descalers are installed inside the boiler shell
and are used to as a preventative measure to:
To install a new descaler, stretch the coiled wire at
the top to elongate the wire and form an open loop.
Hang the descaler on the front horizontal support
rod so that its core will be completely below the
minimum water level in the boiler but hanging free.
The descaler must not contact the boiler shell or the
heat exchanger casting.
•
•
•
Reduce scale deposit buildup
Help remove existing scale deposits
Inhibit boiler and component corrosion
The type of descaler used has a coiled wire
(Cathode) wrapped around a solid cylindrical core
(Anode) that hangs by an open loop from the front
horizontal support rod inside the boiler.
WATER LEVEL PROBE
HOUSING BLOWDOWN
The water contained in the probe housing, being
under pressure, should be "blown through" this
manual valve and be noticeably visible exhausting
out the steamer drain. The probe housing blowdown
should be performed in a time frame dependant on
the quality of the local water supply and steamer
usage. In hard water areas or for steamers heavily
F24700 (October 2001)
Page 24 of 68
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
used, a frequent interval should be used. This
should be inspected.
blowdown procedure is essential to proper operation
and component life by removing sediment and
scalants that may be lodged in the probe housing.
WARNING: THE FOLLOWING STEPS REQUIRE
POWER TO BE APPLIED TO THE UNIT DURING
THE TEST. USE EXTREME CAUTION AT ALL
TIMES.
NOTE: Boiler should be within normal operating
pressures.
Main Water Level Control
1. Remove the left side boiler base panel to
access the ball valve.
NOTE: The main water level control is a dual
functioning control that provides for low level cut-off
protection and differential water level control
2. Turn the power switch ON and allow the boiler
to reach operating pressure.
1. Turn power switch ON and verify:
WARNING: THE STEAMER AND ITS PARTS ARE
HOT. USE CARE WHEN OPERATING, CLEANING
OR SERVICING THE STEAMER. THE BOILER
CONTAINS LIVE STEAM. STAY CLEAR WHEN
OPENING THE VALVE.
A. Low water light is illuminated (front control
panel).
B. HL LED is illuminated on the water level
control board.
3. Open the ball valve for approximately one
minute while under pressure to thoroughly flush
the probes and housing.
C. Boiler is filling with water.
1) If boiler isn’t filling with water:
a. Verify 120 Volt AC is being
applied to the fill valve.
4. Close the ball valve and replace left side panel.
5. Press the reset switch (manual) on the boiler
control panel and allow boiler to reach
operating pressure.
b. Verify fill valve isn’t clogged.
c. Verify 120 Volt AC is on main
water level control board.
6. Steamer is now ready for use.
2) If water level control board doesn’t
WATER LEVEL CONTROLS
TEST
have 120 Volt AC:
a. Check it’s power source at the
10 pin J3 connector, pin 1
(white) and pin 2 (black).
Disconnect the 10-pin J3
connector from the relay board
in the main boiler control box.
The procedure below applies to the water level
control boards for both the old and new style boiler
controls. For additional information related to the
new style controls, refer to "RELAY BOARD" and
"SEQUENCE OF OPERATION" under
"ELECTRICAL OPERATION". For specific
information related to the water level controls
operation, refer to "WATER LEVEL CONTROLS"
under "ELECTRICAL OPERATION".
b. If no voltage is measured on J3
pins 1and 2, check the F1 fuse
(resettable circuit breaker) in the
main control box, and the power
switch connections in the power
switch box.
Loose electrical connections may prevent the
steamer from operating properly.
c. If 120 volt AC was measured on
J3 connector pins 1 and 2 but
not on the water level control
board, verify wire connections.
There should be continuity
An accumulation of lime scale on or near the water
level sensing probes may cause them to retain
water (moist) on the probe surface and give a false
reading. Also, a cracked or damaged insulator may
give a false reading.
between L1 on the water level
control board and J3 pin 7.
There should also be continuity
between L2 on the water level
control board and J3 pin 6. This
path includes connections thru
the J1 connector.
These conditions may cause one or more of the
following to occur:
•
•
•
•
Gas burner no ignition
Boiler no fill
2. At the end of the initial fill:
Boiler overfill.
A. Verify approximately one inch of water
visible in the boiler sight glass.
Boiler no fill and dry fire
NOTE: Dry firing may cause damage to the heat
exchanger, burner assembly or the boiler. If this
condition is suspect, the affected components
B. Verify "green" ready light in the reset
switch is illuminated.
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C. Verify LED’s on the water level control C. Repeat at least twice to verify correct
board, HL LED should be off, and LLCO LLCO operation.
LED should be illuminated.
Auxiliary Low level Cut-Off Control
3. Open the ball valve in the probe housing
assembly (boiler left side) about half way, to
gradually remove boiler water and activate a fill
cycle. Do not press the reset switch to start
the ignition cycle. The next step requires a
visual sight glass measurement that cannot be
obtained, if there is boiling action in the vessel.
5. Continued testing with focus on the auxiliary
LLCO circuit. With water below the lowest
visible level in the sight glass (below Aux LLCO
probe), and boiler in state of initial fill:
A. Verify Aux LLCO LED is off on the Aux
water level control board.
B. Verify Low Water light is illuminated (front
control panel).
A. Verify water level in the boiler sight glass
drops 1/4" to 3/8" before a fill cycle is
initiated. Repeat at least twice to verify
correct fill.
C. Verify 24 volt AC is on Aux LLCO COM,
and 0 volt is on Aux LLCO N.O. contacts.
1) If proper fill wasn’t obtained:
1) With the water level above the Aux
LLCO probe and in the initial fill state:
a. Verify probes 50, 51, and 52
have the correct colored wire to
them and to the water level
control board.
a. Verify Aux LLCO LED is
illuminated on the auxiliary low
water board.
b. Remove the 3 probe assembly,
clean lime scale build-up from
the probes and compare probe
lengths to drawing.
b. Verify N2 on the relay board is
illuminated (new style boiler
controls only).
c. Verify the "green" ready light in
the reset switch is illuminated.
d. Verify 24 volt AC is on the Aux
LLCO common and normally
open contacts of the auxiliary
water level control board.
2) With the main gas valve turned off,
water supply valve turned off, and
probe housing assembly ball valve
opened, press the reset switch.
c. Remove 3/8” flex line from the
probe housing assembly to the
boiler and remove any
a. Verify low water light (front
control panel).
b. Blower comes on.
obstructions. The 1/4"
compression fitting elbow and
1/4" tee into the boiler shell for
the balance tube are sloped 1/8"
so condensation drains into
boiler. When replacing, the
assembly must have this slope
to prevent a blockage from
condensate build-up.
c. Gas pilot cycles at
approximately 15 seconds on
and 5 seconds off.
3) Shortly after water level drops below
the lowest visible level in the sight
glass, the Aux LLCO circuit should be
activated.
a. Low water light turns on.
b. Aux LLCO led turns off.
4. Test the water level control board LLCO circuit.
A. With the boiler full with water, turn off the
water supply and open the ball valve in the
probe housing assembly.
c. Combustion blower is de-
energized.
B. Shortly after the water drops below the
lowest visible level in the sight glass, the
LLCO LED on the water level control
board should turn off, LLCO relay should
de-energize and the normally open
d. Gas pilot stops cycling.
4) Press reset switch to verify lockout.
5) Disconnect lead wire from Aux LLCO
probe. If there is any measurable
contacts should return there shelf state.
resistance between the probe and the
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
boiler shell, remove and clean the
Aux LLCO probe.
4. The cycling pressure switch will maintain the
steam pressure setting in the boiler by cycling
the main burner ON and OFF.
a. Replace the probe and check
resistance again. If resistance is
still present, install a new probe.
High Limit
Adjusting the High Limit pressure switch from a cold
startup is the preferred condition of the boiler. On
the initial cold startup, the highest overshoot
pressure (drift) is achieved after the burner cycles
OFF for the first time. If the boiler is already
operating, the pressure setting can still be made
after following the procedures outlined below.
b. Replace lead wire on probe and
repeat steps "2) thru 4)" to verify
proper operation.
PRESSURE SWITCHES
1. The high limit pressure switch should be
adjusted to allow a maximum pressure in the
boiler of 14.5 to 15.0 PSI. Before making
adjustments to the high limit pressure setting,
the 13 PSI pressure relief valve (PRV- left side)
must be temporarily disabled. This will allow a
high enough pressure in the boiler to properly
set the switch.
WARNING: THE FOLLOWING STEPS REQUIRE
POWER TO BE APPLIED TO THE UNIT DURING
THE TEST. USE EXTREME CAUTION AT ALL
TIMES.
Remove the cover from the pressure switch control
box to access the two pressure switches. The
pressure switch near the front is the cycling pressure
switch and the one beside it is the high limit
pressure switch.
A. The suggested methods to prevent the
valve from releasing pressure are:
Cycling
1) Use a wooden block, a hand tool or
other object to hold the valve plunger
down.
1. If the boiler is already operating, proceed to
step 2. If the boiler is not already operating,
start the boiler as outlined under "CABINET
BASE BOILER" in "STEAMER OPERATION".
2) Use a metal wire threaded through
the hole in the valve handle and tie
the pressure relief valve handle to the
piping below it.
2. Turn one of the cooking compartment timers
ON to exhaust steam from the boiler.
3. Monitor the boiler pressure gauge for several
cycles and note the pressures at which the
burner comes ON and goes OFF.
3) If neither of the two methods keep the
valve fully closed without leaks, an
alternate method is:
A. The main burner should come ON at 8 PSI
and go OFF at 10 PSI. If the readings
differ, adjust the pressure settings as
described below.
a. Turn the power switch OFF and
allow the boiler to blowdown.
b. Remove the discharge piping
from the valve outlet and insert a
pipe plug for temporary use
only.
1) Two pressure adjustment screws
extend through the top of the switch
case. The screw directly above the
right side pointer raises or lowers both
the cut-out (OFF) and the cut-in (ON)
set points simultaneously, without
affecting the differential.
2. Turn the power switch ON and allow the boiler
to completely fill.
A. High Pressure and Low Water indicator
lights (amber) come ON.
The screw directly above the left side
pointer raises or lowers the cut-in
(ON) set point and changes the
differential.
3. When water in the boiler reaches the minimum
level, the green light on the reset switch will
come ON.
A. Press the reset switch on the front control
panel to reset the High Pressure and Low
Water safety controls.
2) Turn the adjustment screw above the
right side pointer to obtain the proper
cut-out (OFF) setting first, then adjust
the other screw to obtain the proper
cut-in (ON) setting.
1) Ignition sequence starts, main burner
lights and water in the boiler begins to
heat.
a. A clockwise rotation increases
the pressure setting while a
counterclockwise rotation
4. Monitor the boiler pressure gauge and note the
pressure at which the high limit switch opens.
decreases the pressure setting.
NOTE: In front of the boiler there is an additional
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
Mechanical Pressure relief valve factory set to
approximately 15 PSI. If the pressure in the boiler
reaches this level, the valve will OPEN.
FILL AND COLD WATER
SOLENOID VALVES
A. High pressure light (amber) will come ON.
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
1) If the pressure switch opens at a
pressure range other than 14.5 to
15.0 PSI then an adjustment to the
switch setting should be made.
a. Proceed to step 5.
1. Check to ensure the solenoid valve is receiving
power.
CAUTION: While making the adjustment, do not
press on the wheel with extreme force. The
switch may rotate and develop a leak at the
compression fittings or in some cases, the rear
lead wire may touch the control box and create
an electrical short.
A. If the solenoid valve is receiving power but
the valve is not opening, the coil may be
malfunctioning.
1) Remove the lead wires from the
solenoid coil and check for continuity.
5. Turn the adjustment wheel several clicks to
change the pressure switch set point.
a. If continuity is measured,
proceed to step "1. B.".
A. A counterclockwise rotation lowers the
pressure switch set point while a
clockwise rotation raises the pressure
switch set point.
b. If no continuity is measured,
replace the solenoid valve and
check for proper operation.
B. If the solenoid valve is receiving power
and the valve appears to be opening but
little or no water is flowing through it, then
the valve ports may be clogged with debris
or a valve component malfunctioning.
NOTE: For every click of the adjustment wheel
during rotation, the pressure setting is changed
approximately 1/8 PSI. Make the adjustment
in small increments.
6. Raise the handle on the 15 PSI mechanical
pressure relief valve and open the valve for
approximately 4 minutes. This will exhaust
steam down the drain line and lower the boiler
pressure.
2. To check solenoid valve further, proceed to
step 3 through 8 for disassembly and inspection
of internal components.
3. Shut water supply off, disconnect the water line
from the valve body then remove the solenoid
valve from the steamer.
A. High limit pressure switch closes at
approximately 12 PSI (non-adjustable).
4. 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.
1) Press the reset switch to reset the
High Pressure safety control.
a. High pressure light (amber) goes
out.
5. Clamp the body of the valve in a vise.
B. Lower the boiler pressure to approximately
8 PSI.
6. Mark a scribe line on the stem nut to the valve
body for proper re-tightening.
C. Ignition sequence starts, main burner
lights and water in the boiler begins to
heat.
7. Remove the stem locking nut to remove the
stem from the valve body.
8. All parts are now accessible for inspection and
cleaning.
7. Repeat steps 4 through 6 until the High Limit
Pressure Switch opens at the correct pressure.
NOTE: If internal solenoid parts appear to be
damaged or worn, then replace the solenoid valve.
Do not reuse damaged or worn parts. No internal
solenoid parts are available as a service
replacement.
8. If the 13 PSI pressure relief valve (PRV- left
side) was temporarily disabled as outlined in
step 1:
A. Turn the power switch OFF and allow the
boiler to blowdown.
A. Check rubber seal on bottom of plunger.
B. Check plunger spring.
B. Return the valve to its original state.
9. Check steamer for proper operation.
C. Check O-ring in valve body.
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
D. Check ports in valve body. A. If the boiler blowdown is ok, then the drain
line and valve are clear of debris and the
valve is functioning properly.
B. If considerable lime scale debris is
apparent, then not only the blowdown
valve, but also the boiler and water level
probes must be thoroughly cleaned. See
"FILL AND COLD WATER SOLENOID
VALVES" for an inspection and cleaning
procedure of a solenoid valve and
"BOILER" for a procedure on boiler
inspection, clean-out and deliming.
INLINE WATER STRAINER
CLEANING
9. Reverse procedure to install.
BOILER BLOWDOWN/DRAIN
SOLENOID VALVE
The procedure outlined below can be used to
inspect and clean the inline water strainer for the
blowdown solenoid valve and, if installed, the inline
water strainer for the boiler fill solenoid valve. Inline
Y strainers should always be located upstream of a
water solenoid valve.
The water contained in the boiler, being under
pressure, should be "blown through" this valve and
be noticeably visible exhausting out the steamer
drain. 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: For proper operation, the strainer must be
installed so the water flow is directed towards the
solenoid valve and the leg of the Y with a threaded
cap is pointing downwards to catch debris.
The boiler blowdown/drain process is an automatic
function and should start whenever the power switch
is turned OFF after a normal operating cycle. The
blowdown solenoid is a normally open (N.O.) valve
that CLOSES when energized by the power switch.
When the power switch is turned OFF, the
1. Turn the power switch OFF to and allow the
boiler to blowdown.
2. When blowdown completes, shut OFF the
water supply.
blowdown solenoid is de-energized and the valve
OPENS to allow the boiler to blowdown.
3. Remove the cap and strainer screen from the
leg of the Y pointing downwards toward the
floor.
If the blowdown operation appears to function
sluggishly or not at all, considerable scalants may
be lodged in the drain line plumbing exiting the
boiler, strainer, and/or the blowdown valve.
4. Remove the screen from the cap and clean any
accumulated debris from the screen and also
remove any debris trapped in the opening of
the strainer body.
1. Turn the power switch OFF and allow boiler to
blowdown.
NOTE: If screen can not be thoroughly cleaned,
2. Turn the ON/OFF knob on the main gas valve
to OFF.
replace it with a new one.
5. Insert screen into cap then re-install cap to
strainer body.
3. Remove the strainer clean-out plug located in
the center of cap.
6. Turn the water supply and power switch ON
and allow the boiler to reach operating
pressure.
4. Turn the power switch ON and allow the boiler
"fill water" to flush-out the drain line until no
debris is seen exiting the clean-out hole.
7. Turn the power switch OFF and check strainer
for leaks, as the boiler blows down.
5. Turn the power switch and the water supply
OFF.
6. Turn the ON/OFF knob on the main gas valve
back to ON.
7. Remove and clean the strainer as outlined
under "INLINE WATER STRAINER
CLEANING".
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
A. N13 on relay board ON (air pressure
MAIN BURNER IGNITION
CHECKS
switch CLOSED and condition satisfied).
B. Pilot gas valve energized and ignition
sequence starts.
The complete gas burner assembly is located inside
the heat exchanger casting in the boiler. The
perforated burner head functions as both pilot and
main gas burner. The inner portion of the perforated
burner head serves as the pilot to light the main
burner during the trial for ignition. Once the main
burner lights, the flame encompasses the entire
perforated burner head and the pilot flame
extinguishes.
NOTE: If N13 is not ON or Pilot gas valve is
not energized, then check the air pressure
switch setting as outlined under "AIR
PRESSURE SWITCH ADJUSTMENT".
5. Verify 24VAC to ignition module and pilot
valve.
A. N1 on relay board ON (24VAC is being
supplied for the system).
If burner ignition problems are encountered, perform
the following checks to ensure components are
adjusted properly.
B. N13 on relay board ON (24VAC is being
supplied to the ignition module).
C. N14 & N15 on relay board ON (24VAC is
being supplied to the pilot ignition timing
circuit and the pilot valve.
1. Turn power switch ON and allow the boiler to
fill.
2. Verify "low water" and "high pressure" safety
circuits are satisfied.
6. Verify spark and pilot ignition.
A. If pilot lights, proceed to step 7.
A. Water Level in boiler.
B. If sparking occurs but pilot does not light,
then check the pilot pressure setting as
outlined under "GAS PILOT PRESSURE
ADJUSTMENT".
1) Approximately one visible inch of
water in the sight glass.
2) Auxiliary LLCO is satisfied.
a. N2 on relay board ON (low water
C. If spark is not occurring:
safety circuit satisfied).
1) Restart power ON sequence by
"rapidly" turning the power switch
OFF then back ON. A rapid switching
is needed to keep the boiler from
starting automatic blowdown.
b. LED on auxiliary water level
board ON.
B. High Limit Pressure Switch
1) Zero reading on boiler pressure
gauge.
2) Remove ignition cable boot from the
ignitor rod terminal and check ignitor
position in the burner head assembly.
NOTE: Burner cycles ON at less than or
equal to 8 PSI and OFF at 10 PSI.
3) Measure distance the ignitor terminal
extends past the ignitor nut. Distance
should measure approximately 3/4" to
7/8". See diagram 5898 "COMPLETE
BURNER ASSEMBLY" at the end of
this procedure.
NOTE: High Limit Pressure Switch
automatically resets at approximately 12
PSI.
C. Press the reset switch to reset the safety
circuits.
NOTE: Touch ignitor terminal only
and not the ceramic insulator.
NOTE: Hi Pressure and low water lights on
front control panel should be OFF.
a. If distance is ok, proceed to step
5) below and perform step "a"
and "b" then continue with step
"6)".
1) N3 on relay board ON (high pressure
safety circuit satisfied).
3. Verify blower is running and its operation is
quiet.
b. If distance is other than stated,
loosen ignitor nut, set the ignitor
position and then re-tighten the
ignitor nut.
NOTE: A "noisy" blower rotation may
indicate bearing wear and reduce air
pressure output.
c. Re-connect ignition cable.
A. N12 on relay board ON (120VAC supplied
to the blower).
4) Press reset switch to start the ignition
process.
4. Verify air pressure switch is CLOSED.
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
a. If ignitor sparks and pilot lights,
proceed to step 7.
Verify the burner tube insulation and
heat exchanger casting are intact.
b. If ignitor does not spark, proceed
to step "5)" below.
NOTE: The suggested method for
inspection is to mount a small mirror
to a 2 foot long rod and insert the
mirror inside the burner tube and use
a flashlight to illuminate the area.
5) Restart power ON sequence by
"rapidly" turning the power switch
OFF then back ON. A rapid switching
is needed to keep the boiler from
starting automatic blowdown.
NOTE: If necessary, the complete
burner tube assembly can be
removed to aid in performing the
measurement and inspections.
a. Grasp the ignitor terminal and
rotate the ignitor approximately
45°.
a. Inspect the ceramic insulation for
damage at the area around the
burner head inside the burner
tube.
b. Re-connect ignition cable.
6) Press the reset switch to start the
ignition process.
b. Measure ceramic insulation
insertion depth/location from the
end of the insulation that
a. If ignitor sparks and pilot lights,
proceed to step 7.
surrounds the burner head to the
opposite end of the burner tube
(end plate mounting flange). The
dimension should measure
approximately 23 5/8 inches
±1/8. See diagram 5898
"COMPLETE BURNER
ASSEMBLY" at the end of this
procedure.
b. If ignitor does not spark, repeat
steps "5)" through this step until
rod has been rotated 360°.
7. Verify main burner ignition.
A. If main burner lights and remains lit with
no intermittent problems, then burner is
functioning properly.
B. If main burner does not light or shows
intermittent problems, then check the main
burner pressure setting as outlined under
"GAS MANIFOLD PRESSURE
c. Verify that casting debris is not
clogging the "heat transfer fins"
at the end of heat exchanger
casting and that the fins have
not eroded away.
ADJUSTMENT".
1) If pressure is ok but intermittent
burner problems continue, then the
following components must be
examined.
d. Inspect the interior of heat
exchanger casting for signs of
water leakage. Also, signs of
water leakage into the heat
exchanger casting may be
determined by examining the
bottom area of the flue transition
piece and floor.
2) Turn the power switch OFF and allow
the boiler to blowdown.
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
WARNING: SHUT OFF THE GAS BEFORE
SERVICING THE UNIT.
3) Remove burner head assembly as
outlined under "BURNER HEAD
ASSEMBLY" in "REMOVAL AND
REPLACEMENT OF PARTS".
4) The complete or intermittent loss of
burner ignition or a burner operation
that is loud and noisy may indicate
the burner tube insulation or heat
exchanger casting is damaged.
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F24700 (October 2001)
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
AIR PRESSURE SWITCH
ADJUSTMENT
The air pressure switch senses the pressure level
produced by the blower for combustion. When the
pressure is sufficient, the switch closes and supplies
power to the ignition control module. The gas
ignition sequence starts to light the gas pilot and
then main burner. If the gas pilot is not lighting
(valve not energized), the ignition control module
may not be receiving power, assuming the minimum
water level is satisfied. Check the air pressure
switch operation then adjust if necessary as outlined
in the procedure below.
1. Turn the power switch OFF.
2. Remove the left side panel from the cabinet
base.
A. Inspect the air intake to the blower for
debris build up and clogging.
A. Turn the adjustment screw fully clockwise
to the highest setting.
B. Slowly turn the adjustment screw
counterclockwise until the pilot gas valve
energizes then add ½ turn to the
adjustment.
NOTE: The screw head should not extend out
past the screw housing.
1) If Pilot gas valve energizes, proceed
to step 5.
2) If Pilot gas valve does not energize,
check the following:
a. Remove the lead wires from the
switch and verify with a meter
that the switch contacts are
closing with the blower ON. If
necessary, continue to turn the
adjustment screw several turns
counterclockwise to CLOSE the
switch contacts.
1) If debris is found, clean it away from
the air intake.
B. Turn the power switch ON and verify main
burner ignition.
b. If the switch contacts are not
closing, turn the power switch
OFF, remove the pressure
1) If burner ignites then no adjustment to
the pressure switch setting is
necessary.
switch from the TEE and check
the air orifice for debris build up
and clogging. If debris is found,
clean it away from the orifice.
2) If burner does not ignite, proceed to
step 3.
3. Open the cabinet base door and turn the
ON/OFF knob for the main gas valve to OFF.
4. Adjust the air pressure switch setting as
follows:
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
2) Press the reset switch to start the
ignition process.
C. Listen for main gas burner ignition to
verify operation.
GAS PILOT PRESSURE
ADJUSTMENT
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
WARNING: SHUT OFF THE GAS BEFORE
SERVICING THE UNIT.
1. Open the cabinet base door to access pilot gas
valve.
2. Remove the pilot pressure plug tap from the
outlet side of valve.
c. Replace the orifice, pressure
switch and connect the lead
wires to the switch. Turn the
power switch ON and adjust the
pressure switch again as outlined
in steps 4A and 4B. Verify the
pilot gas valve is energizing.
d. If the pilot gas valve is not
energizing and power is
available to the pressure switch,
turn the power switch OFF.
Replace with a new air pressure
switch and adjust the switch as
outlined from step 3 thru the end
of this procedure.
5. Restart the ignition sequence by "rapidly"
turning the power switch OFF then back ON. A
rapid switching is needed to keep the boiler
from starting automatic blowdown.
A. Press the reset switch to start the ignition
process.
1) Listen for gas pilot ignition to verify
operation.
a. If gas pilot ignition is successful,
turn the ON/OFF knob for the
main gas valve back to ON.
A. Install a hose barb adaptor and attach a
gas pressure manometer.
3. Turn the gas supply and power switch ON.
b. Listen for main gas burner
ignition to verify operation.
A. Once the boiler fills, press the reset switch
to start the ignition process.
B. Verify the pilot and main burner both ignite
in succession.
NOTE: The reset switch can be pressed after
the green ready light on the switch comes ON.
This indicates the water level in the boiler is at
the minimum operating level.
1) Restart the ignition sequence by
"rapidly" turning the power switch
OFF then back ON. A rapid switching
is needed to keep the boiler from
starting automatic blowdown.
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
4. After the main burner lights, allow the boiler to
reach operating pressure then turn the ON/OFF
knob for the main gas valve to OFF.
5. Restart the ignition sequence by "rapidly"
turning the power switch OFF then back ON. A
rapid switching is needed to keep the boiler
from starting automatic blowdown.
8. With the burner lit, set the pressure as outlined
below.
A. To increase pressure, turn the screw
clockwise.
A. Press the reset switch to start the ignition
process.
B. To decrease pressure, turn the screw
counterclockwise.
6. After the pilot burner lights, compare the
manometer pressure reading to the pressure
chart near the end of this procedure.
NOTE: Accurate gas pressure adjustments can only
be made with the gas ON and the burner lit.
NOTE: The pilot gas valve operates on a time delay
circuit and will only be energized for approximately
15 seconds to light the main burner then shut OFF.
The pilot pressure reading must be taken while the
pilot valve is energized within this time interval.
After the main burner ignition time expires, the
ignition control module will sense there is no flame
present and will then try to re-establish a flame to
light the main burner. This cycle will continue to
repeat until the main gas valve is turned back ON.
PRESSURE READINGS (INCHES W.C.)
LINE
GAS TYPE
PILOT
MINIMUM
RECOMMENDED
MANIFOLD
MAX
Natural
3.5
3.5
7.0
14.0
Propane
11.0
A. If the pressure is not correct, proceed to
step 7 to adjust.
NOTE: If the incoming line pressure is less than the
minimum recommended, then the manifold pressure
can not be set correctly.
B. If the pressure is correct, turn the power
switch OFF, replace the adjustment screw
cap and pilot pressure plug tap to the gas
valve. Turn the knob on the main gas
valve back to ON.
9. Once the correct pressure has been set, turn
the gas supply and power switch OFF. Replace
the adjustment screw cap and pilot pressure
plug tap on the valve.
7. Remove the adjustment screw cap to access
the pressure adjustment screw.
10. Turn the knob on the main gas valve to ON,
the gas supply ON and check for proper
operation.
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
A. If other appliances are connected to the
GAS MANIFOLD PRESSURE
ADJUSTMENT
same gas line, turn them all ON and check
manometer pressure reading again. If the
pressure drops ½ inch water column or
more, then the gas supply needs to be
checked by the gas line installer or the
local gas company for adequate sizing.
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
NOTE: The gas supply line to the steamer
should be a minimum of one inch diameter
(ID).
WARNING: SHUT OFF THE GAS SUPPLY
BEFORE SERVICING THE UNIT.
B. If the pressure does not drop as described
above but the manifold pressure still
1. Open the cabinet base door to access main gas
valve.
requires adjustment, proceed to step 5.
5. Remove the adjustment screw cap to access
the pressure adjustment screw.
2. Remove the manifold pressure tap plug from
the outlet side of valve.
6. With the burner lit, set the pressure as outlined
below.
A. To increase pressure, turn the screw
clockwise.
B. To decrease pressure, turn the screw
counterclockwise.
NOTE: Accurate gas pressure adjustments can only
be made with the gas ON and the burner lit.
A. Install a hose barb adaptor and attach a
gas pressure manometer.
PRESSURE READINGS (INCHES W.C.)
3. Turn the gas supply and power switch ON.
A. Once the boiler fills, press the reset switch
to start the ignition process.
LINE
GAS TYPE
BURNER
MINIMUM
RECOMMENDED
MANIFOLD
MAX
NOTE: The reset switch can be pressed after
the green ready light on the switch comes ON.
This indicates the water level in the boiler is at
the minimum operating level.
Natural
3.0
3.0
7.0
14.0
Propane
11.0
4. After the main burner lights, allow the boiler to
reach operating pressure then compare the gas
manometer pressure reading to the pressure
chart near the end of this procedure.
NOTE: If the incoming line pressure is less than the
minimum stated, then the manifold pressure can not
be set correctly.
F24700 (October 2001)
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
7. Once the correct pressure has been set, turn
F. "Rapidly", turn the power switch OFF then
ON. A rapid switching is needed to keep
the boiler from starting automatic
the gas supply and power switch OFF. Replace
the adjustment screw cap and manifold
pressure plug tap plug on the valve.
blowdown. Then press the reset button.
8. Turn the gas supply on and check for proper
operation.
NOTE:
If the power is not re-set, the ignition
module continues sparking for a total of 90
seconds, then locks out. The module remains
locked out until the power switch is turned to
OFF then back ON and the reset switch is
pressed to re-start the ignition trial cycle.
IGNITION CONTROL MODULE
CHECKS
1. Turn the power switch ON and allow the boiler
to fill.
2. Aux. water level control satisfied and high limit
closed.
3. Press the reset switch.
A. Combustion blower comes on and
generates pressure to close the air
pressure switch contacts.
B. Ignition control module is energized and
trial for ignition starts. Check for 24VAC
between terminals five and six.
C. Ignition module closes the internal pilot
valve contacts. Check for 24 volts
between terminals two and three.
1) High voltage is sent from terminal
nine to the spark electrode and
sparking begins.
Terminals:
1. Main Valve - 24VAC will be present on terminal
#1 with the flame sensing electrode sensing an
adequate burner fame. This output voltage will
remain present as long as the burner flame
remains adequate.
2) At the same time, pilot timing circuit
(control board) and pilot valve are
both energized allowing gas flow to
the pilot.
2. MV/PV (common).
NOTE: The pilot valve will be energized
by the relay board timer circuit for
approximately 15 seconds to light the
main burner.
3. Pilot Valve - 24VAC will be present on terminal
#3 at the instant an input voltage is supplied to
the module. This output 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.
D. Pilot ignition is established (pilot lit), and
main gas valve is energized. Check for 24
volts between terminals one and two.
1)
Sparking stops.
4. Ground (burner).
5. 24VAC Neutral (ground).
6. 24VAC Input.
2) Ignition module monitors main burner
flame.
3) After 15 seconds relay board timer
times out.
7. High Voltage to spark electrode. Provides high
output voltage (13kv peak) to the spark
electrode to light the gas pilot. Once pilot is lit,
provides a path for flame current sensing by
the Ignition Module via the spark electrode high
voltage cable on terminal #9.
a. Pilot valve de-energized.
E. As long as the ignition control module is
sensing a burner flame through the ignition
cable on terminal nine, the internal main
voltage (MV) and pilot (PV) contacts
(N.O.) remain closed.
NOTE: If pilot flame is not sensed within 15
seconds, you can re-start the ignition
sequence.
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F24700 (October 2001)
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
1) If pilot lights, then ignition system is
Spark Verification Test
working properly.
1. Turn the power switch OFF.
2) If ignitor does not spark, repeat steps
E thru this step until rod has been
rotated 360°.
2. Check to ensure that all electrical terminal
connections on the ignition control module and
the ignitor rod are clean and tight. If the ignition
cable appears to be damaged, replace it and
re-try lighting burner.
3) If ignitor still does not spark, proceed
to step 6.
WARNING: SHUT OFF THE GAS BEFORE
SERVICING THE UNIT.
3. Verify that the ignition control module and the
burner ground have a good ground connection.
6. Turn the power switch OFF.
A. If loose connections are found, make the
necessary adjustments and check for
proper operation.
7. Remove the burner head assembly as outlined
under "BURNER HEAD ASSEMBLY" in
"REMOVAL AND REPLACEMENT OF PARTS"
and check the following:
B. If connections are ok but sparking does
not occur, proceed to step 4.
A. The gap between the spark probe and the
ground pin should be approximately 0.090"
to 0.100". Adjust as necessary. See
diagram 5899 "BURNER HEAD
4. Remove ignition cable boot from the ignitor rod
terminal and check ignitor position in the burner
head assembly.
A. Measure distance ignitor terminal extends
past ignitor nut, approximately 3/4" to 7/8".
See diagram 5898 "COMPLETE BURNER
ASSEMBLY" under "MAIN BURNER
IGNITION CHECKS”.
ASSEMBLY" under "MAIN BURNER
IGNITION CHECKS".
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 ignitor rod and re-test.
NOTE: Touch ignitor terminal only and not
the ceramic insulator.
1) If distance is ok, proceed to step 5
and perform steps B thru E.
1) If replacing ignitor rod, loosen the
ignitor rod mounting nut and remove
the ignitor rod from the burner head
assembly.
2) If distance is other than stated, loosen
ignitor nut, set the ignitor position.
WARNING: THE FOLLOWING STEPS REQUIRE
POWER TO BE APPLIED TO THE UNIT DURING
THE TEST. USE EXTREME CAUTION AT ALL
TIMES.
3) Re-connect ignition cable.
B. Turn the power switch ON and allow the
boiler to fill.
C. Press reset switch to start the ignition
process.
8. Verify spark at electrode.
A. Place the assembly on the floor and attach
a temporary ground wire from the burner
ground on the heat exchanger to the
burner head assembly.
1) If pilot lights, then ignition system is
working properly.
2) If ignitor does not spark, proceed to
step 5.
B. Turn the power switch ON and press the
reset switch.
5. Turn the power switch OFF.
C. Observe spark condition from ignitor.
A. Remove ignition cable boot from the
ignitor rod terminal.
1) If a good spark from ignitor is present
then the ignition system is working
properly.
B. Grasp the ignitor terminal and rotate the
ignitor approximately 45°.
2) If ignitor is still not sparking, replace
the ignition control module and repeat
steps 8A and 8B to check for proper
operation.
NOTE: Touch ignitor terminal only and not the
ceramic insulator.
C. Re-connect ignition cable.
D. Turn the power switch ON and allow the
boiler to fill.
3) After making the necessary
component adjustments or
replacements, re-assemble and
check for proper operation.
E. Press reset switch to start the ignition
process.
F24700 (October 2001)
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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS
Door Sealing Adjustment
COOKING COMPARTMENT
1. Check the door gasket quality. If damaged or
worn, replace as outlined in "REMOVAL" under
"COOKING COMPARTMENT DOOR(S)".
NOTE: For access to compartment controls,
remove the right side compartment panel.
2. Loosen screws until the screw heads no longer
touch the gasket plate.
Intake Shut-Off Valve Adjustment (Steam Flow)
1. With the right side compartment panel
removed, open the intake shut-off valve
completely.
3. Tighten screws until screw head touches gasket
plate and at that point begin counting turns.
4. Tighten all screws approximately two turns.
5. Close the door and check for proper operation.
2. If the steamer ready light is on, then proceed to
step 4.
A. If necessary, tighten all screws an
additional 1/2 turn and repeat step 5.
3. If the boiler is off, then turn main power switch
ON and allow boiler to heat up until steamer
ready light comes on. Allow boiler to cycle 2 to
3 times, then proceed to step 4.
6. Repeat step 5 until the door closes properly
and no steam leaks are seen around the gasket
seal.
4. Turn both cooking timers on.
5. Monitor the boiler until heat source turns off.
6. At that time, adjust the intake shut-off valve
until the manifold pressure gauge reads 9 ±1
psi. The valve setting should be made while the
boiler pressure is at the upper cycling limit.
7. Monitor gauge reading 1 to 2 cycles to ensure
pressure is set correctly.
8. Once the valve is set, turn both cooking timers
off and reinstall right side compartment panel.
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VHX SERIES STEAMER - ELECTRICAL OPERATION
Door Latch Adjustment
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 nut from the striker and this will release it from
the panel.
4. Once the proper slot alignment has been set,
hold the striker close to its base using a rag and
vise grips, then tighten the striker nut. Be
careful not to damage the striker slot when
tightening or door may not latch properly.
NOTE: Do not over tighten as the striker will begin
to turn and change alignment.
Once the nut and washer have been removed, door
will open freely.
Remove any burrs on the striker that may cause the
latch to stick. Reinstall the striker and adjust, so
door will not jam.
To adjust:
1. Reinstall the striker with the slot pointing
upwards and hand tighten nut only.
2. Close the door to center the striker in the oval
mounting hole.
3. Open the door and check the strikers’ slot for
horizontal alignment. The slot on the striker
must be kept horizontal in order for the door
latch to catch it properly and latch.
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
ELECTRICAL OPERATION
into the boiler.
WATER LEVEL CONTROLS
When the water level drops below the low level (LL)
probe, power is removed from the inverse latching
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.
Low Level Cut-Off & Differential Control
The steamer is equipped with three water level
sensing probes (high, low and low level cut-off) and
a single water level control board (solid state). The
water level control board performs two functions: 1)
Provide low level cut-off protection to shut off the
heat source in case the water level drops below the
low level cut-off (LLCO) probe. 2) Perform as a
differential level control to maintain the water level
between the low and high water level probes.
The water level control (WLC) has input voltage
(120VAC) across terminals 11 and 12 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 board relay coils
(LLCO and HL) and to the Inverse Latching Relay
(ILR) electronic circuit on the board. 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 inverse latching relay of the board is de-
energized, 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 high
level (HL) relay, closes HL-3 normally open
contacts, and illuminates the HL relay LED. With the
HL-3 contacts closed, the boiler fill solenoid is
energized and water begins filling the boiler.
When the water level reaches the low level cut-off
(LLCO) probe, the LLCO relay is energized and
illuminates 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. NOTE: Auxiliary control(s)
in the heating circuit must also be satisfied before
heating can start.
When the water level reaches the low level (LL)
probe, power to terminal 2 on the WLC board is
present but no switching occurs.
After the water level reaches the high level (HL)
probe, the inverse latching relay of the board is
energized and locked through the low level probe
(LL) and ILR-1 contacts. With ILR-2 contacts open,
this de-energizes the HL relay and the HL LED goes
out. With the HL-3 contacts open, the boiler fill
solenoid is de-energized, stopping the flow of water
Page 41 of 68
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VHX SERIES STEAMER - ELECTRICAL OPERATION
Auxiliary Low Level Cut-Off
This control serves as a safety backup to the main
water level control (WLC) board to meet 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 but performs a
single function: 1) Provide auxiliary low level cut-off
protection to shut off the heat source in case the
water level drops below the low level cut-off (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 (WLC) has input
voltage (120VAC) across terminals 11 and 12 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. Also, the low water level indicator
light (amber) on the boiler base control panel comes
on.
When the water level reaches the low level cut-off
(LLCO) probe, the LLCO relay is energized (LLCO-2
close) and the LLCO LED lights up. 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 boiler stops filling, press the manual reset
switch on the boiler base control panel. This turns
off the low water light, energizes the combustion
blower and allows the ignition cycle to begin.
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
RELAY BOARD
Board Layout and LED Legend
The relay board Provides a centralized location for wire harness connections and power transfer through board
relays (K1-K7) to the other steamer controls. Also, provides a condition or component troubleshooting indicator
by utilizing seventeen LED’S on the board to represent the status of the condition or component in the operating
sequence. When the condition for the component being monitored is satisfied or activated, an LED will light to
indicate its proper operation. If the corresponding LED does not light then the condition or component has not
been satisfied or is not activated.
LED LEGEND
LED ON = Condition satisfied or component activated. 1 LED OFF = Condition not satisfied or component de-activated.
LED
N1
DESCRIPTION
LED
N10
DESCRIPTION
Board powered (24vac).
Auxiliary water level satisfied (LLCO) and reset switch
activated.
N2
Auxiliary water level satisfied (LLCO).
N11
Boiler operating pressure condition satisfied and reset
switch activated.
N3
N4
N5
High limit pressure switch closed.
N12
N13
N14
Combustion blower ON.
Steamer is ready (ready light "green" is ON).
Auxiliary water level satisfied (LLCO) and reset switch activated.
Combustion blower air pressure switch satisfied.
Ignition module pilot voltage (PV) to board level timing
circuit.
N6 1 Low water condition exists (N2 LED ON) or previously existed. If
water level condition is satisfied and the reset switch is activated
then N6 LED will turn off.
N15 2 Pilot voltage (PV) to pilot gas valve.
N7
Boiler pressure condition satisfied and reset switch activated.
N16
N17
Ignition module main voltage (MV) to low water level
contacts (LLCO) on water board.
N8 1 Boiler High pressure condition exists (N3 LED ON) or previously
existed. If boiler pressure condition is satisfied and the reset switch
is activated then N8 led will turn off.
Low water level satisfied (LLCO) and main voltage (MV)
from ignition module is supplied to main gas valve.
N9
Cycling pressure switch CLOSED “call for heat”.
NOTES: 1. At initial power on, N6 & N8 led’s will be ON until conditions are satisfied and reset switch is activated.
NOTE: 2. Board level timing circuit energized and powers pilot gas valve for approximately 15 seconds then de-energizes.
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VHX SERIES STEAMER - ELECTRICAL OPERATION
Boiler Operational Status (LED Indicator)
Use the tables below to determine the operational status of a component or condition by utilizing the LED
indicators on the board. The operational state’s are divided into categories A thru F.
Initial Conditions: (STATE A)
- 120V, water and gas supplied to steamer
- Power Switch ON
- HIGH PRESS and LOW WATER lights ON (amber, front control panel)
- Green “ready” light OFF
- Water is filling boiler
STATUS
LED
DESCRIPTION
ELECTRICAL COMPONENTS CONDITION
ON OFF
N1
N2
N3
X
X
X
24V supplied to relay board
Aux Water level not satisfied
High limit pressure switch satisfied
Aux. LLCO contacts OPEN
K2 energized - K2(1) CLOSE, K2(2) CLOSE
Aux Water level is initially not
satisfied. Therefore N4 is OFF
N4
X
K1(1) OPEN
N5
N6
N7
X
Reset switch is not being energized
X
Aux Water level is/was not satisfied K3 not energized
Reset switch is not being energized
X
High Limit pressure switch is/was
K4 not energized
N8
N9
X
X
not satisfied
Cycling pressure switch is closed
and unit is calling for HEAT
N10 through N17 remain OFF
Aux Water Level Satisfied: (STATE B)
- Green “ready” light ON (ready light remains ON, until a LOW WATER or HIGH PRESSURE) condition occurs.
Status of LED’s are the same as “Initial Conditions” except for the following:
STATUS
LED
DESCRIPTION
ELECTRICAL COMPONENTS CONDITION
ON OFF
Aux. LLCO relay energized, Aux. LLCO contacts
CLOSED
N2
N4
X
Aux water level is satisfied
Aux LLCO water level and high limit
are satisfied. Green “ready” light ON.
X
K1 energized - K1(1) CLOSE
Reset Engaged: (STATE C)
User presses/engages the RESET button
- LOW WATER and HIGH PRESSURE lights OFF (amber, front control panel)
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
DESCRIPTION ELECTRICAL COMPONENTS CONDITION
same as “state A”
STATUS
ON OFF
LED
N1
N2
N3
N4
X
X
X
X
same as "state B"
same as “state A”
same as "state B
Reset switch is/was momentarily
energized
N5
N6
N7
X
K3 energized - K3(1) CLOSE (locking circuit)
K3 energized - K3(1) OPEN
Aux Water level is satisfied.
(Amber WATER light OFF)
X
X
Reset switch is/was momentarily
energized
X
K4 energized - K4(1) CLOSE (locking circuit)
K4 energized - K4(1) OPEN
High Limit is satisfied.
(Amber HIGH PRESS OFF)
N8
N9
X
X
same as “state A”
High limit is satisfied and reset
switch energized
N10
K3(2) CLOSE
Aux Water level is satisfied and
reset switch energized
N11
N12
X
X
K4(2) CLOSE, K5 energized
K5(1) CLOSE
Air intake blower receiving power
N13-N17 remain OFF
Air Pressure Switch Satisfied: (STATE D)
Assume water level control “LLCO” is satisfied (LLCO contacts closed)
N1 thru N12 same as “Reset Engaged: (state C)"
STATUS
LED
DESCRIPTION
ELECTRICAL COMPONENTS CONDITION
ON OFF
N13
N14
X
X
Air pressure switch satisfied
24V to ignition module (term 6)
PV CLOSE, 24V to K7
Ignition module PV coil energized
Pilot gas valve is energized.
Note: N15 and the pilot gas valve will
be ON for approximately 15 seconds,
then turn OFF.
K7 energized K7(1) CLOSE, relay board timer
circuit energized and starts time count. K6
energized K6(1) CLOSE, pilot gas valve coil
energized for 15 sec. only.
N15
X
Ignition module PV coil energized,
pilot ignition flame is detected
MV CLOSE, 24V to water level board LLCO
contacts
N16
N17
X
X
Water level board LLCO is satisfied
and main gas valve is receiving
power.
Main gas valve coil energized, main burner
lights and flame continues to be detected.
Burner ON, Boiler Heating to generate steam: (STATE E)
All LED’s ON except N6 & N8, N15 (still OFF from state D)
Burner OFF, Boiler Pressure Satisfied: (STATE F)
These LED’s should be OFF - N6, N8, N9, , N10, N11, N12, N13, N14, N15 (still OFF from state D) N16 & N17
These LED’s should be ON - N1 thru N5, N7
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F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
limit pressure switch contacts (N.C.).
SEQUENCE OF OPERATION
a. K2 contacts K2(1) N.O. & K2(2)
N.O. close, no power
transferred.
NEW STYLE CONTROLS - BOILER
This sequence of operation is written for boiler
bases with the new style boiler controls. See
"BOILER CONTROL STYLES" under "GENERAL".
Refer to schematic diagram TSP1480.
3) N9 lit. 24VAC to one side of K3(2)
N.O. contacts through cycling
pressure switch N.C.
3. Water level reaches LLCO probe for both water
level control and auxiliary low level control.
Initial Fill and Preheat
Conditions.
A. LLCO relay on water level board
energizes, LLCO contacts (N.O.) close
A. Power switch OFF.
1)
LED on board lights.
B. Boiler connected to correct voltage
(120VAC).
B. Aux. LLCO relay energizes, aux. LLCO
contacts (N.O.) close.
C. Boiler properly grounded.
1)
LED on board lights.
D. Gas and water supply valve(s) ON.
2) N2 lit. K1 is energized.
E. Main gas valve manual valve in ON
position
a. K1(1) N.O. close.
F. Cycling pressure switch closed.
G. High limit pressure switch closed.
b. N4 lit. Ready light (green) on the
control panel manual reset
switch, ON.
H. Cold water condenser (CWC) thermostat
open.
3) K1(2) N.O. close.
NOTE: No power is transferred until manual
reset switch pressed.
I.
Automatic blowdown solenoid valve
(A.B.D.) open and boiler empty.
NOTE: The LLCO and aux. LLCO relays will
remain energized and LLCO LED’S will remain
lit until the water level drops below the LLCO
probes or the power switch is turned OFF.
2. Turn power switch ON.
A. Automatic Blowdown valve (N.O.) is
energized and close.
B. Water level control (WLC) energized.
NOTE: The reset switch could be pressed to
start combustion blower & ignition cycle but it’s
preferred to let the boiler fill the to the "High
Level" before continuing.
1) High level (HL) relay energized, HL-3
contacts (N.O.) close.
a. Fill solenoid energized, water
begins filling the boiler (fill time
4-11 min.).
4. Water reaches LL (low level) probe.
5. Water reaches HL (high level) probe.
A. Fill solenoid is de-energized.
B. HL-LED
2) HL LED lit.
C. Auxiliary water level control is powered.
1) Aux. LLCO N.O. contacts remain
open.
6. Manual reset switch pressed.
A. N5 lit. K3 is energized (120VAC).
D. 120VAC to one side of K5(1) N.O., K1(1)
N.O., K3(1) N.O., K4(1) N.O. contacts.
NOTE: Relay K3 remains energized through
K3(1) N.O. locking circuit.
E. N6 lit. Low Water light (control panel) lit
thru K3(1) N.C.
1) N6 goes out. K3(1) N.O. contacts
close and K3(1) N.C. contacts open.
F. N8 lit. Hi Pressure light (control panel) lit
thru K4(1) N.C.
2) Low water light (control panel) goes
out.
G. N1 lit. 24VAC transformer is energized
and relay board is powered.
3) N10 lit. K3(2) N.O. contacts close.
1) 24VAC to one side of auxiliary water
level control LLCO contacts (N.O.).
a. 24VAC to one side of K4(2) N.O.
contacts.
2) N3 lit. K2 energized through the high
B. N7 lit. K4 is energized (120VAC).
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
pilot, quickly cycle the reset switch to prevent
NOTE: Relay K4 remains energized through
the boiler from draining. If the pilot is not
established within 90 seconds from the ignitor
module being energized, the ignition module
locks out power to the gas valves. The module
remains locked out until the power switch is
turned to OFF then ON and the manual reset
switch is pressed to r e-start the ignition trial
cycle.
K4(1) N.O. locking circuit.
1) N8 goes out. K4(1) N.O. contacts
close and K4(1) N.C. contacts open.
2) High pressure light (control panel)
goes out.
C. N11 lit. K4(2) N.O. contacts close.
1) K5 is energized (24VAC).
D. As boiler heats up and builds pressure,
some by-pass water/steam is produced
which runs into the steam drain box. This
causes the cold water condenser (CWC)
solenoid to cycle, cooling the drain water
and condensing any steam vapors before
exiting the drain. The CWC solenoid is
powered through the CWC cycling
thermostat.
a. N12 lit. K5(1) N.O. contacts
close.
a) Combustion blower starts.
7. N13 lit. When the combustion blower
generates sufficient air pressure, the air
pressure switch N.O. contacts close.
A. Ignition module is powered (24VAC).
1) Ignition module starts sparking.
NOTE: On initial cold startup only, the boiler
pressure may overshoot and cause the
mechanical pressure relief valve to open
momentarily.
2)
N14 lit. Pilot voltage (PV) N.O.
contacts close.
E. As long as the ignition control module
senses a burner flame, the internal main
voltage (MV) contacts (N.O.) on the
ignition module remain closed, and main
gas valve stays ON.
a. K7 is energized.
a) K7(1) N.O. contacts close.
3) 15 sec. timer circuit (board level,
solid state timer) energized and
timing of pilot gas valve ON time
begins.
NOTE: PV N.O. contacts are also closed, but
K6 contacts are open to keep pilot valve
closed.
a. K6 energized.
8. Boiler steam pressure reaches upper limit set
point of 10 PSI (Approx. 15 minutes).
a) N15 lit. K6(1) N.O. close.
4) Pilot gas valve energized, pilot valve
opens for gas to flow.
A. Cycling pressure switch open.
1) N9, N10, N11, N12, N13 go out.
a. K5 de-energized.
B. Pilot flame established. Micro amp flame
"sense" current rectified to ignition module
through ignition cable.
a) K5(1) N.O. contacts open.
1) Sparking stops.
b. Combustion blower is de-
energized.
2) N16 lit. Main voltage (MV) N.O.
contacts close.
a) Air pressure switch opens.
B. Ignition module is de-energized
1) PV and MV contacts open.
a. N17 LED lit. Proves LLCO on
water level board closed.
b. Main gas valve opens, burner
lights and boiler begins to heat
up.
a. N14, N16, N17 go out.
b. Main gas valve closes, burner
goes out.
C. 15 seconds after ignition module
energized, relay board timer circuit times
out.
c. K7 de-energized.
a) K7(1) open
1) N15 goes out. K6 de-energized.
9. Boiler steam pressure drops below lower limit
set point of 8 PSI and the cycling pressure
switch close.
a. Pilot valve closes, gas flow stops
to pilot.
NOTE: If pilot ignition is not established within
the allotted 15 seconds, the ignition module
continues to spark. To attempt to relight the
A. Boiler steam pressure is maintained by the
cycling of the pressure switch between the
Page 47 of 68
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VHX SERIES STEAMER - ELECTRICAL OPERATION
upper and lower set point limits. The B. Boiler connected to correct voltage
cycling pressure switch continues to
energize and de-energize the heating
circuit to cycle the burner ON and OFF.
(120VAC).
1) Power to cooking compartment
controls. See "COOKING
This sequence continues until one of the
following occurs:
COMPARTMENT CONTROLS" later
in this section.
1) Power switch is turned OFF.
C. Boiler properly grounded (boiler and water
level controls share a common ground)
2) Boiler water level drops below the
LLCO probes for the main water level
control (WLC) and the auxiliary low
level control.
D. Gas and water supply valve(s) ON.
E. Main gas valve ON.
F. Cycling pressure switch CLOSED.
G. High limit pressure switch CLOSED.
3) Boiler pressurizes to 15 PSI, causing
the high limit pressure switch to open.
H. Cold water condenser (CWC) thermostat
OPEN.
Water Refill (After Initial Fill)
1. Water level drops below low level probe (LL).
A. HL relay is energized.
I.
Automatic blowdown valve (A.B.D.) OPEN
and boiler empty.
1) HL-3 (N.O.) contacts close.
2) Fill solenoid is energized.
3) HL LED comes ON.
2. Turn power switch ON.
A. Relay R4 energized and R4 contacts
(N.O.) CLOSE.
B. Power ON light (red) comes ON.
2. Water reaches LL (low level) probe.
3. Water reaches high level probe.
A. HL relay is de-energized.
1) HL-3 (N.O.) contacts open.
2) Fill solenoid is de-energized.
3) HL LED goes out.
C. Blowdown solenoid valve is energized and
CLOSES.
D. Auxiliary water level control is powered.
1) Aux. LLCO N.O. contacts remain
OPEN (Aux. LLCO relay de-
energized).
E. Low water level light (amber) comes ON.
4. The water refill cycle will occur whenever the
water level is below the low level probe and will
not affect the operation of either the preheat or
cook cycle.
NOTE: The low water indicator light will remain
ON and the safety circuit de-energized until the
water level in the boiler reaches the auxiliary
low level cut-off probes (aux. LLCO, minimum
level) for the aux. water level control, and the
manual reset switch is pressed.
Boiler Blowdown/drain
1. Power switch turned OFF.
A. Automatic blowdown solenoid valve (N.O.)
is de-energized and valve opens to drain
the boiler.
F. High pressure light (amber) comes ON.
NOTE: The high pressure indicator light will
remain ON and the safety circuit de-energized
until the manual reset button is pressed (high
limit pressure switch must be closed).
B. Power is removed from all components
except cold water condenser (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.
G. Power is connected through the high limit
pressure switch contacts (N.C.) to one side
of the push button reset switch.
H. Water level control is powered (Low Level
Cut-off & Differential Control).
OLD STYLE CONTROLS - BOILER
This sequence of operation is written for boiler
bases with the old style boiler controls. See
"BOILER CONTROL STYLES" under "GENERAL".
Refer to schematic diagram 5480.
1) High level (HL) relay is energized, HL
contacts (N.O.) CLOSE
a. HL LED lights up.
Initial Fill And Preheat
1. Conditions.
b. Fill solenoid is energized and
water begins filling boiler (fill
time 4-11 min.).
A. Power switch OFF.
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
3. Water level reaches LLCO (low water level cut- 3) Main voltage (MV) N.O. contacts
off) probe for the water level control and to the
auxiliary LLCO probe for the auxiliary low level
cut-off control.
CLOSE.
a. Main gas valve OPENS, burner
lights and boiler begins to heat
up.
A. LLCO relay energizes, LLCO contacts
(N.O.) CLOSE and LED lights.
NOTE: As boiler heats up and builds pressure,
some by-pass water/steam is produced which
runs into the steam drain box. This causes the
cold water condenser (CWC) solenoid to cycle,
cooling the drain water and condensing any
steam vapors before exiting the drain. The
CWC solenoid is powered by the CWC
thermostat.
NOTE: No power is transferred until ignition
sequence starts.
B. Aux. LLCO relay energizes, LLCO
contacts (N.O.) CLOSE and LED lights.
NOTE: The LLCO and aux. LLCO relays will remain
energized and LLCO LED’S will remain lit until the
water level drops below the LLCO probes or the
power switch is turned OFF.
NOTE: On initial cold startup only, the boiler
pressure may overshoot and cause the
mechanical pressure relief valve to OPEN
momentarily.
4. Water reaches LL (low level) probe.
5. Water reaches HL (high level) probe.
A. Fill solenoid is de-energized.
6. Press the manual reset switch.
A. Relay coil (R1) energized.
b. As long as the ignition control
module senses a burner flame,
the internal main voltage (MV)
contacts (N.O.) on the ignition
module remain closed, and main
gas valve stays ON.
1) High pressure light turns OFF.
B. Relay coil (R3) energized.
c. If sparking is allowed to continue
for a total of 90 seconds, then
the ignition module locks out
power to the gas valve (pilot
valve and main valve remain
closed). The module remains
locked out until the power switch
is turned to OFF then ON and
the manual reset switch is
pressed to re-start the ignition
trial cycle.
1) Low water light turns OFF.
2) Transformer (T1) energized.
7. 24VAC is connected through the cycling
pressure switch contacts to the following
components:
A. Normally open (N.O.) side of the air
pressure switch.
NOTE: No power is transferred until air
pressure switch CLOSES.
8. Boiler steam pressure reaches upper limit set
point of 10 PSI (approximately 15 min).
B. Relay coil (R2) is energized and R2
contacts (N.O.) CLOSE.
A. Cycling pressure switch opens and power
is removed from the following
components:
1) 120VAC is supplied to the
combustion air blower and blower
starts.
1) Combustion air pressure switch
normally open (N.O.) terminal.
C. Once the combustion blower develops
sufficient pressure, the air pressure switch
CLOSES.
2) Relay coil (R2) returning R2 contacts
to there N.O. shelf state.
1) 24VAC is then applied to the Ignition
control module and the ignition cycle
starts.
a. Combustion air blower de-
energized.
a. Pilot voltage (PV) N.O. contacts
CLOSE.
B. Ignition control module is de-energized,
PV and MV contacts OPEN.
b. Pilot gas valve energized, pilot
valve opens for gas to flow and
Ignitor begins sparking to light
pilot.
1) Main gas solenoid valve de-
energizes, gas flow shuts OFF and
burner goes out.
9. Boiler steam pressure drops below lower limit
set point of 8 PSI and the cycling pressure
switch CLOSES.
2) Pilot ignition is established (pilot lit)
and a micro amp flame "sense"
current is sent back to the ignition
module through the ignition cable.
A. Boiler steam pressure is maintained by the
cycling of the pressure switch between the
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VHX SERIES STEAMER - ELECTRICAL OPERATION
upper and lower set point limits. The
1) Cooking compartment ready light
(green) comes ON.
cycling pressure switch continues to
energize and de-energize the heating
circuit to cycle the burner ON and OFF.
3. Start a cook cycle.
A. Insert product into steamer and close door.
B. Set a cook time.
This sequence continues until one of the
following occurs:
NOTE: On initial startup, if a cooking timer is
set immediately after the ready light comes on,
steam solenoid chattering will be heard (oil
canning) and the ready lights will flash for
several seconds. This condition is caused by
the manifold steam 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. After the steam pressure
passes approximately 4 psi this condition
subsides. During normal operation, this
condition will not be seen.
1) Power switch is turned OFF.
2) Boiler water level drops below the
LLCO probes for the main water level
control and the auxiliary low level cut-
off control
3) Boiler pressurizes to 15 PSI, causing
the high limit pressure switch to
OPEN.
Water Refill (After Initial Fill)
1. Water level drops below low level probe (LL).
A. HL relay is energized.
1) HL N.O. contacts CLOSE, fill
solenoid is energized and HL LED
comes ON.
2. Water reaches LL (low level) probe.
3. Water reaches high level probe.
A. HL relay is de-energized.
C. Contacts 1/3 of cook timer CLOSE and
timer motor is energized.
1) Compartment steam solenoid valve
energized and steam begins to enter
the compartment.
1) HL N.O. contacts OPEN, fill solenoid
is de-energized and HL LED goes
out.
2) Ready light (green) goes out and
Cooking light (red) comes ON.
4. The water refill cycle will occur whenever the
water level is below the low level probe and will
not affect the operation of either the preheat or
cook cycle.
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.
Boiler Blowdown/Drain
1. Power switch turned OFF.
A. Boiler blowdown sequence starts.
4. Time expires on timer.
A. Timer contacts 1/3 OPEN, timer motor de-
energized.
B. The automatic blowdown solenoid valve
(N.O.) is de-energized and valve OPENS
to drain the boiler.
B. Steam solenoid valve de-energizes,
stopping the flow steam into compartment.
C. Power is removed from all components
except cold water condenser (CWC)
C. Timer contacts 4/1 CLOSE and energize
buzzer until manually turned OFF.
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.
D. Cooking light (red) goes out and Ready
light (green) comes ON.
5. Timer manually turned OFF.
A. Contacts 1/4 OPEN
COOKING COMPARTMENT CONTROLS
1. Conditions.
B. Alarm Buzzer de-energized and stops
buzzing.
A. Doors shut (closes the N.O. door switch
contacts).
6. Steamer reverts to preheat cycle until time is
dialed on timer and the door is shut, water level
drops below low level cut-off probe or the
power switch is turned OFF.
B. Cooking timers OFF.
C. Compartment pressure switch contacts
OPEN.
2. With boiler at operating pressure.
A. Cooking compartment pressure switch
CLOSES (approx. 3 PSI).
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
SCHEMATICS
Models Built After 5/25/00 (New Style Boiler Controls)
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
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VHX SERIES STEAMER - ELECTRICAL OPERATION
Models Built Before 5/25/00 (Old Style Boiler Controls)
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
Cooking Compartment Controls
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VHX SERIES STEAMER - ELECTRICAL OPERATION
WIRING DIAGRAMS
Models Built After 5/25/00 (New Style Boiler Controls)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
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VHX SERIES STEAMER - ELECTRICAL OPERATION
Models Built Before 5/25/00 (Old Style Boiler Controls)
F24700 (October 2001)
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VHX SERIES STEAMER - ELECTRICAL OPERATION
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VHX SERIES STEAMER - ELECTRICAL OPERATION
Cooking Compartment Controls
F24700 (October 2001)
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VHX SERIES STEAMER - TROUBLESHOOTING
TROUBLESHOOTING
BOILER BASE CONTROLS
WARNING: CERTAIN PROCEDURES IN THIS SECTION REQUIRE ELECTRICAL TESTS OR
MEASUREMENTS WHILE POWER IS APPLIED TO THE MACHINE. EXERCISE EXTREME CAUTION AT ALL
TIMES. IF TEST POINTS ARE NOT EASILY ACCESSIBLE, DISCONNECT POWER, ATTACH TEST
EQUIPMENT AND REAPPLY POWER TO TEST.
Models with new style controls: Before performing any of the troubleshooting checks listed below, remove the
cover from the main control box and check the condition of the LED’S on the relay board for the status of the
condition or component in the operating sequence. By utilizing the troubleshooting LED’S, the Service
Technician can quickly and easily determine if a component is functioning properly or in need of repair. Refer to
"RELAY BOARD" under "ELECTRICAL OPERATION".
SYMPTOM
POSSIBLE CAUSES
1. No power to steamer.
Steamer does not operate.
2. F1 Fuse open.
3. Malfunctioning power switch.
4. Malfunctioning power switch latching relay (old style controls
only).
Steamer ON, cannot reset low water
condition.
1. Low water level in boiler.
A. Water inlet valve(s) OFF.
B. Fill solenoid not receiving power, clogged or
malfunctioning.
2. Manual blowdown valve on water level probe housing open.
3. Improper ground.
4. Lime scale build-up auxiliary water level probe.
5. Malfunctioning reset switch.
6. Malfunctioning auxiliary water level control board.
Steamer ON, cannot reset high pressure 1. Excessive pressure in boiler.
condition.
2. Malfunctioning reset switch.
3. Malfunctioning high pressure limit switch.
4. Malfunctioning pressure switch latching relay (old style controls
only).
Steamer ON, reset switch pressed but
blower does not operate when calling for
heat.
1. Blower malfunctioning or loose connection on blower cord.
2. 24 VAC transformer malfunctioning.
3. Malfunction in cycling pressure switch.
4. Malfunctioning "Low Water" or "Hi Pressure" light not indicating
true condition.
(boiler pressure within operating limits)
5. Blower relay malfunctioning (old style controls only).
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VHX SERIES STEAMER - TROUBLESHOOTING
POSSIBLE CAUSES
SYMPTOM
Blower operating, no pilot gas flow.
1. Main gas supply turned OFF.
2. Ignition module lockout. Turn power switch OFF for several
seconds then ON to reset the module.
3. Air pressure switch:
A. Not mounted in true vertical position.
B. Incorrect pressure setting.
C. Malfunctioning switch.
4. Malfunctioning Ignition module.
5. Malfunctioning pilot gas valve.
6. Blocked or dirty pilot gas orifice.
Pilot flame not proving or lighting main
burner.
1. Gas not ON.
2. Incorrect manifold pressure for pilot gas.
3. Poor connection between igniter and ignition cable.
4. Fouled spark igniter.
5. Incorrect gap in spark igniter.
6. Faulty igniter or cracked insulation.
7. Improper ground.
8. Low water level in boiler or boiler not filling.
9. Flame sensing current too low.
10. Cracked or incorrect burner head attachment.
11. Incorrect igniter positioning.
12. Incorrect pilot orifice.
Main burner not lighting correctly or
excessive ignition noise.
1. Blocked or dirty air orifice on blower.
2. Insufficient gas supply pressure.
3. Incorrect gas pilot pressure.
4. Incorrect gas manifold pressure.
5. Pilot flame not sensing correctly.
6. Burner tube insulation broken or deteriorated.
7. Blocked or restricted flue.
8. Incorrect pilot or main gas burner orifice size.
Excess combustion noise or combustion 1. Blocked or dirty air orifice on blower.
induced harmonics.
2. Incorrect gas manifold pressure.
3. Insufficient gas supply pressure.
4. Steam vapors introduced into blower inlet.
5. Loose flue connections.
Boiler not maintaining set pressure
and/or excessive burner on time.
1. Leaking boiler blowdown valve.
2. Manual blowdown valve on water level probe housing open.
3. Malfunctioning 13 psi overshoot relief valve.
4. Low incoming gas supply pressure.
5. Excessive load on steam outlet.
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VHX SERIES STEAMER - TROUBLESHOOTING
POSSIBLE CAUSES
SYMPTOM
Gas odor.
1. Leaks in pipe fitting connections or components.
2. Leaking pressure tap plug on pilot or main gas valve; loose or
missing pressure adjustment screw cap on main gas valve.
3. Leaking gaskets in air/gas mixture path.
4. Pilot or main gas valve malfunction (improper venting or vent
blocked).
5. Incorrect gas pressure.
6. Malfunctioning gas burner.
7. Blocked or dirty air orifice on blower.
8. Blocked or dirty gas orifice.
9. Malfunctioning blower.
10. No pilot ignition.
11. Improper hood venting, vent blocked or room not vented
properly.
Drain box leaking.
1. Clog in drain line plumbing.
2. Drain restricted to size below 1-1/4" pipe.
3. Drain extension plumbing not at the proper slope or plumbing
too lengthy.
4. Grommets not sealing.
5. Steamer draining while under pressure and relief valve opening
at the same time (flooding drain box).
6. Cold water condensing spray is "over spraying".
7. Drain box thermostat improperly set or malfunctioning.
Cold water condenser not operating
properly.
1. Water supply valves(s) turned off.
2. Cold water condenser solenoid not receiving power, inoperative
or valve plugged.
3. Cold water condenser thermostat malfunction or needs
adjustment.
4. Plugged spray nozzle.
5. Water supply pressure high (improper valve operation).
Heat coming on without water in boiler
(Dry firing).
1. Lime scale build-up on water level probes (shorted to ground).
2. Retention of water in probe housing (assembly or aux.LLCO).
3. Water level control malfunction.
4. Aux. water level control malfunction.
Spark Ignitor not sparking.
1. Ignitor boot on ignition cable loose, damaged or missing
causing excessive ignition voltage leakage.
2. Loose, broken or damaged lead wires (including ground) from
ignition module to ignitor.
3. Poor ground on ignitor assembly.
NOTE: Items 4, 5 & 7 see "IGNITION CONTROL MODULE
CHECKS" in "SERVICE PROCEDURES AND
ADJUSTMENTS".
4. Ignition module not receiving power.
5. Ignition module malfunction (no output voltages or spark).
6. Ceramic flame rod insulator on ignitor cracked or damaged
from extreme heat.
7. Incorrect spark gap setting.
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VHX SERIES STEAMER - TROUBLESHOOTING
POSSIBLE CAUSES
SYMPTOM
Boiler Slow to Pressurize
1. Low water supply pressure, inline water strainer clogged or fill
solenoid valve malfunction. See "INLINE WATER STRAINER
CLEANING" and "FILL AND COLD WATER SOLENOID
VALVES" in "SERVICE PROCEDURES AND
ADJUSTMENTS".
(over 15 min. to achieve operating
pressure)
2. Boiler blowdown solenoid valve clogged and not fully closing.
Check for a slow leak out of steamer drain. If not able to verify,
then proceed to step 3. If blowdown solenoid valve appears to
be functioning properly, then proceed to step 4.
3. Turn power switch OFF, disconnect lead wires from blowdown
solenoid and remove it for inspection.
4. A heavy build-up of scalants has coated the interior of the
boiler, creating an insulating effect. Examine interior of boiler
as outlined under “BOILER” in "SERVICE PROCEDURES AND
ADJUSTMENTS".
5. Low incoming gas pressure is reducing BTU output.
A. Verify gas supply line to the steamer is a minimum of one
inch diameter (ID).
B. Check incoming line and manifold gas pressures as
outlined in "GAS MANIFOLD PRESSURE ADJUSTMENT"
under "SERVICE PROCEDURES AND ADJUSTMENTS".
6. Gas valve malfunction.
A. Check incoming line and manifold gas pressures as
outlined in "GAS MANIFOLD PRESSURE ADJUSTMENT
under "SERVICE PROCEDURES AND ADJUSTMENTS".
Boiler will not heat or build pressure.
1. Gas not on.
2. Power/reset switch assembly malfunction.
3. Boiler not filling - check fill solenoid for power, clogging or
malfunction.
4. Gas pilot and/or gas manifold pressure low. See "GAS PILOT
PRESSURE ADJUSTMENT" and "GAS MANIFOLD
PRESSURE ADJUSTMENT" in "SERVICE PROCEDURES
AND ADJUSTMENTS".
5. Cycling pressure switch open or set too high. Steamer is
cycling on high limit.
6. High limit pressure switch open and not re-setting
(malfunction).
7. Water too "pure" for probes to properly conduct electricity.
NOTE: Items 8 & 9 see "WATER LEVEL CONTROLS TEST"
in "SERVICE PROCEDURES AND ADJUSTMENTS".
8. Water Level Control malfunction.
9. Aux. Water Level Control malfunction.
Pressure relief valve(s) opening or
leaking.
1. Pressure overshoot on initial startup or long burner on times
under heavy usage.
2. Pressure relief valve malfunction.
3. Cycling pressure switch set to high.
4. High limit pressure switch not set correctly or malfunctioning.
F24700 (October 2001)
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VHX SERIES STEAMER - TROUBLESHOOTING
POSSIBLE CAUSES
SYMPTOM
Steam output low or slow cooking.
1. Cooking Compartment.
A. Blocked steam injector ports. (Open door, press door
switch button and verify good steam flow into
compartment).
B. Steam solenoid valve not fully opening or blocked.
C. Steam intake shut-off valve closed or out of adjustment.
See "INTAKE SHUT-OFF VALVE ADJUSTMENT (STEAM
FLOW)" in "SERVICE PROCEDURES AND
ADJUSTMENTS".
2. Boiler Base.
A. Cycling pressure switch malfunction or needs adjustment.
B. Steam header line (supply) blockage.
C. Heavy amount of condensate in the pressure controls
steam supply line.
D. Pressure relief valve leaking.
E. Steam supply lines leaking badly.
Steamer leaks water.
Boiler water level too high.
Boiler does not fill.
1. Loose water, steam or drain line connections (top or base).
2. Heat exchanger gasket not sealing.
3. Leak at gauge glass.
1. Fill solenoid does not shut off.
2. Lime scale build-up (moist) on High level probe (open circuit).
3. Water level control malfunction.
1. Water supply not on.
2. Fill solenoid not opening or plugged.
3. Water level control malfunction.
Burner won’t light.
1. Gas not on.
2. Power/reset switch assembly malfunction.
3. Boiler not filling - check fill solenoid for power, clogging or
malfunction.
4. Air pressure switch:
A. Not mounted in true vertical position.
B. Incorrect pressure setting.
C. Malfunctioning switch.
5. Ignition module not receiving power.
6. Steamer not properly grounded and/or polarity of incoming
power is incorrect on spark ignition systems.
7. Ignition module malfunction.
8. Gas valve malfunction.
9. Water too "pure" for probes to properly conduct electricity.
10. Cycling pressure switch open or set too high. Steamer is
cycling on high limit.
11. High limit pressure switch open and not re-setting
(malfunction).
12. Water level control malfunction.
13. Aux. water level control malfunction.
Page 65 of 68
F24700 (October 2001)
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VHX SERIES STEAMER - TROUBLESHOOTING
COOKING COMPARTMENT CONTROLS
SYMPTOM
POSSIBLE CAUSES
Cooking compartments do not operate.
1. No power to compartments.
2. Pressure in boiler is below compartment pressure switch
setting.
3. Door switch malfunction.
4. Timer malfunction.
5. Malfunctioning pressure switch in compartment.
6. Verify correct compartment wiring and functioning
components.
Steam generated inside compartment
when timer is off.
1. Steam supply solenoid not fully closing (clogged or dirty). See
"FILL AND COLD WATER SOLENOID VALVES" in "SERVICE
PROCEDURES AND ADJUSTMENTS".
2. Timer contacts 1 & 3 closed.
Timer motor does not run.
Door not closing properly.
1. Door open or door switch inoperative.
2. Timer not getting power.
3. Timer motor inoperative.
1. Door latch assembly malfunction or out of adjustment. See
"DOOR SEALING ADJUSTMENT" in "SERVICE
PROCEDURES AND ADJUSTMENTS"
2. Striker adjustment. See "DOOR LATCH ADJUSTMENT" in
"SERVICE PROCEDURES AND ADJUSTMENTS".
Door won’t open.
1. Latch won’t release. See "DOOR LATCH ADJUSTMENT" in
"SERVICE PROCEDURES AND ADJUSTMENTS".
Buzzer not operating.
1. Timer malfunction.
2. Buzzer malfunction.
Compartment leaks water around door
or water accumulating in compartment .
1. Compartment drain screen clogged.
2. Drain line obstructed or not to an open gap drain.
3. Steamer not level.
Steam leaks around door.
1. Worn gasket - See "DOOR SEALING ADJUSTMENT" in
"SERVICE PROCEDURES AND ADJUSTMENTS".
2. Damaged gasket.
3. Drain line obstructed or not to an open drain.
F24700 (October 2001)
Page 66 of 68
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VHX SERIES STEAMER
- NOTES -
Page 67 of 68
F24700 (October 2001)
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VHX SERIES STEAMER - CONDENSED SPARE PARTS LIST
CONDENSED SPARE PARTS LIST
NEW STYLE CONTROLS ONLY
VHX24G, VHX24G5, MHB24G
PART NUMBER
DESCRIPTION
NOTES
853582-1
850778-1
850735-1
354344-4
851315-1
851316-1
880413
Igniter, Sensor
Switch, Air Pressure
Blower, Combustion
Valve, Pilot Gas
Valve, Main Gas
Valve, Pressure Relief 13 psi
Valve, Pressure Relief 15 psi
Valve(s), Cold Water Condenser and Boiler Fill
Switch, Pressure Cycling
Switch, Pressure High Limit
Thermostat, Condenser/drain Box
Transformer, 120vac to 24vac
Module, Ignition Control
817222
833488
851578-1
844062-1
411500-12
417980-1
844070-1
844069-1
852081-1
851613-1
851618-1
844130-3
853275-1
853273-1
411690-1
843836
Control, Aux. Low Water Board
Control, Water Board
Circuit, Breaker 5amp Slow Blow (fuse)
Boiler, Drain Valve (blowdown)
Power Cord, drain Valve
Cable, Ignitor 18"
Switch assembly, on/off, reset & lights
Relay Board
Timer, Cooking
Steam Solenoid Valves, Cooking Compartment
F24700 (October 2001)
Printed in U.S.A.
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