A.O. Smith VWH 500, VWH 200 Technical Documents

VFS-SER Rev A

Service Manual

Models: 500 - 2000

Up To 4:1 Turndown

Setup/Return

 WARNING

Save/Clear

Run/Stop

This manual must only be
used by a qualified heating
installer / service technician.
Read all instructions, including
this manual and the VF Series
Installation and Operation
Manual, before installing.
Perform steps in the order given.
Failure to comply could result in
severe personal injury, death, or
substantial property damage.

Save this manual for future reference.

Contents

CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Hazard Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

PLEASE READ BEFORE PROCEEDING . . . . . . . . . . . . . 3

Handling Ceramic Fiber Materials . . . . . . . . . . . . . . . . . . . 3

When servicing appliance . . . . . . . . . . . . . . . . . . . . . . . 3

Appliance operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Appliance water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

WHAT IS IN THIS MANUAL . . . . . . . . . . . . . . . . . . . . . . . 4

1. SERVICE

The VF Series Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Control Module Inputs . . . . . . . . . . . . . . . . . . . . . . . . . 6

Control Module Outputs . . . . . . . . . . . . . . . . . . . . . . . . 7

General Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Sequence of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Display Panel Menu Access . . . . . . . . . . . . . . . . . . . . . . 10

Display Panel Parameter Access . . . . . . . . . . . . . . . . . . . 11

Parameter Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Viewable and Changeable Control Parameters . . . . . 13-15

2. MAINTENANCE

Maintenance and Annual Startup . . . . . . . . . . . . . . . . 16-24

3. TROUBLESHOOTING

Before Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Check Control Module Fuses . . . . . . . . . . . . . . . . . . . . . 25

Table 3A - Troubleshooting Chart - No Display . . . . . . . . 26

Checking Temperature Sensors . . . . . . . . . . . . . . . . . . . 27

Table 3B - Inlet/Outlet Resistance vs. Temperature . 27
Table 3C - Flue Temperature Sensor Resistance vs.

Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 3D - Tank Sensor Resistance vs. Temperature 27

Table 3E - Troubleshooting Chart - Noisy System . . . . . 28

Table 3F - Troubleshooting Chart - Fault Messages . 29-35

Revision Notes . . . . . . . . . . . . . . . . . . . . . . . . . Back Cover

Hazard definitions

The following defined terms are used throughout this manual to bring attention to the presence of hazards of various risk
levels or to important information concerning the life of the product.

 DANGER

 WARNING

 CAUTION

CAUTION

NOTICE

DANGER indicates an imminently hazardous situation which, if not avoided, will result in death or
serious injury.

WARNING indicates a potentially hazardous situation which, if not avoided, could result in death or
serious injury.

CAUTION indicates a potentially hazardous situation which, if not avoided, may result in minor or
moderate injury.

CAUTION used without the safety alert symbol indicates a potentially hazardous situation which, if not
avoided, may result in property damage.

NOTICE indicates special instructions on installation, operation, or maintenance that are important but
not related to personal injury or property damage.

2

Please read before proceeding

Service Manual

 WARNING

NOTICE

Installer – Read all instructions,
including this manual and the VF Series
Installation and Operation Manual,
before installing. Perform steps in the
order given.

User – This manual is for use only
by a qualified heating installer/service
technician. Refer to the VF Series
Installation and Operation Manual for
your reference.

Have this appliance serviced/inspected
by a qualified service technician at least
annually.

Failure to comply with the above could
result in severe personal injury, death or
substantial property damage.

When calling or writing about the
appliance – Please have the appliance
model and serial number from the
appliance’s rating plate.

Consider piping and installation when
determining appliance location (see the
VF Series Installation and Operation
Manual).

Any claims for damage or shortage in
shipment must be filed immediately
against the transportation company by
the consignee.

When servicing appliance –

• To avoid electric shock, disconnect electrical supply
before performing maintenance.

• To avoid severe burns, allow appliance to cool before
performing maintenance.

Appliance operation –

• Do not block flow of combustion or ventilation air to
the appliance.

• Should overheating occur or gas supply fail to shut off,
do not turn off or disconnect electrical supply to
circulator. Instead, shut off the gas supply at a location
external to the appliance.

• Do not use this appliance if any part has been under water.
The possible damage to a flooded appliance can be
extensive and present numerous safety hazards. Any
appliance that has been under water must be replaced.

Appliance water –

• Thoroughly flush the system (without appliance
connected) to remove sediment. The high-efficiency
heat exchanger can be damaged by build-up or
corrosion due to sediment.

• Do not use petroleum-based cleaning or sealing
compounds in the appliance system. Gaskets and seals in
the system may be damaged. This can result in
substantial property damage.

• Do not use “homemade cures” or “appliance patent
medicines”. Serious damage to the appliance, personnel,
and/or property may result.

3

What is in this manual?

Service Manual

Service

The VF Series display

• Display panel readout, buttons and their functions

Control module inputs

• Control module inputs and options

Control module outputs

• Control module outputs and options

General

• How the appliance operates

• How the control module operates

• Access modes -- user and installer

• Sequence of operation -- Domestic Hot Water
(DHW)/space heating

Control panel menu access

• Accessing programming mode and locating menus

Control panel parameter access

• Accessing and changing parameters from the display panel

Maintenance

• Service and maintenance schedules

• Address reported problems

• Inspect appliance area and appliance interior

• Clean condensate system

• Check all piping for leaks

• Flue vent system and air piping

• Check water system

• Check expansion tank

• Check control settings

• Check igniter

• Check all appliance wiring

• Check flue gas passageways

• Flame inspection

• Inspect and clean burner

• General maintenance

• Checking manifold gas pressure

• Combustion analysis procedure

• Gas valve adjustment procedure

• Cleaning heat exchanger

• Review with owner

Troubleshooting

Quick start information -- parameter table

• An index of available adjustments and readouts, where to
access them and where to find detailed information.

VF Series operation

• A: General

• B: Data Logging

• C: Functions

• D: DHW Settings

• E: Control Modes

• F: Building Management System (BMS)

• G: Circulation Pump

• H: Service Notification

• Troubleshooting table - No display

• Checking temperature sensors

• Troubleshooting table - Noisy system

• Troubleshooting table -Fault messages displayed on Operator
Interface

4

1 Service

The VF Series display

SETUP/RETURN

SAVE/CLEAR

RUN/STOP

Service Manual

+

BACK

FORWARD

5

1 Service

Control inputs

(FIELD SUPPLIED)

(FACTORY SUPPLIED)

ON/OFF / 0-10V

Service Manual

(FIELD SUPPLIED)

(FIELD SUPPLIED)

6

1 Service (continued)

Control outputs

Service Manual

(FIELD SUPPLIED)

(IF EQUIPPED)

7

1 Service

General Operation

Service Manual

How the appliance operates

The water heater uses a copper-finned tube heat exchanger to
transfer heat from the flue products to the water. An electronic
control module monitors various inputs to initiate a call for
heat. The blower provides both primary and secondary air to
the burner and forces the flue products out of the combustion
chamber and into the vent system. The control module regulates
the blower speed to control the firing rate of the appliance. The
modulating gas valve monitors the amount of combustion air
being pulled into the blower and regulates the amount of gas
supplied, which then mixes with the combustion air and is
supplied to the burner.

How the control module operates

The VF Series control module receives input from appliance
sensors. The control module activates and controls the blower
and gas valve to regulate heat input and switches the DHW
pump on and off as needed. The user/installer programs the
module to meet system needs by adjusting control parameters.
These parameters set operating temperatures and heater
operating modes. Appliance operation can be based on heater
return water temperature, tank temperature, tank temperature
thermostat, and/or remote enable switch.

Sequence of operation

Access modes

User

The user can adjust the tank setpoint using the (+) and (-)
buttons at any time during normal operation. By entering the
USER code (0101), the user can also change temperature units,
time and date, and night setback settings. In user mode, the
following parameters can be viewed but not changed: heater
model number; software version; total operating hours, total
cycles and last 10 faults.

Installer

Most parameters are available only to the installer, accessible
only by entering the installer access code (2525).

Saving parameters

To save parameters and exit programming:

Press the SAVE/CLEAR button, then the SETUP/RETURN
button 3 times.

To keep parameter settings only for a current operating cycle:

Press the SETUP/RETURN button 3 times after making all
desired parameter changes.

Table 1A shows control module normal sequences of operation
for DHW operation.

To enter a parameter and continue programming:

Press the SETUP/RETURN button 1 time to return to the
parameter listings; press again to return to the menu listings.
Remember to press the SAVE/CLEAR button when finished
programming in order to save the changes made.

8

1 Service (continued)

Sequence of operation

Table 1A_Sequence of Operation - Space Heating and DHW

OPERATION DISPLAY

Service Manual

1. The manual reset high limit must be closed before any
action will take place.

2. Upon a call for heat the control turns on the DHW pump. The
flow switch and low water cutoff (if equipped) must close.

3. • The gas pressure switch(es) (if equipped) must close.

• The contacts for the louvers close. The louver proving,
blocked drain switch, and auto reset high limit inputs must
close.

• If the air pressure switch is open, the prepurge cycle then
begins by starting the combustion blower. Once started,
the air pressure switch must close.

4. After prepurge, the blower slows down and the hot surface
igniter (HSI) is energized.

5. Once the HSI is hot, the trial for ignition begins with the
opening of the gas valve.

6. If the control does not sense flame, it will lock out.

HTR: Standby
OUT: 123.8F(129)

HTR: Standby
OUT: 123.8F(129)

HTR: Standby
OUT: 123.8F(129)

HTR: PREPURGE
OUT: 123.9F(129)

HTR: IGNITION
OUT: 123.9F(129)

HTR: POSTPURGE, LOCKOUT
OUT: 123.9F(129)

7. If the control senses flame, it will fire the burner to maintain
the setpoint. The firing rate will modulate as required to hold
the tank temperature at the setpoint.

8. Once the call for heat is satisfied, the control will turn
off the burner. The blower will remain on for the postpurge
cycle. The DHW pump will continue to run for its pump
delay time, then turn off.

9. Pump off.

HTR: DHW 20% RATE
OUT: 124.8F(129)

HTR: POSTPURGE

OUT: 127.4F(129)

HTR: Standby

OUT: 124.7F(129)

9

1 Service

Display panel menu access

Table 1B_Use this procedure to access menus from the display panel

SAVE/

CLEAR

SETUP/

RETURN

Service Manual

(+)

FORWARD

(+)

FORWARD

(+)

FORWARD

(+)

SAVE/

CLEAR

SAVE/CLEAR

2

0

0

0

2

0

0

0

0

2

0

5

0

2

0

5

0

2

2

5

0

2

2

5

5

2

2

5

he FORWARD and BACK buttons

(+)

(-)

10

(-)

(-)

(-)

(-)

SAVE/CLEAR

Service Manual

1 Service (continued)

Display panel parameter access

Table 1C_This is a typical example of accessing a parameter, shown for pump delay parameter

(-)

(-)

(-)

(-)

SAVE/

CLEAR

SAVE/

CLEAR

(+)

(-)

SAVE/

CLEAR

SETUP/

RETURN

SETUP/

RETURN

30 sec

45 sec

y

The DHW Pump Delay menu item
is shown

y

The DHW Pump Delay setting is
shown

y

y

The new setting is saved and the
menu item is shown

DHW

a

11

1 Service

Parameter table

Table 1D_This table lists control module parameters and where to access them

Service Manual

Menu

A

GENERAL

B

DATA

LOGGING

C

FUNCTIONS

D

DHW

SETTINGS

SUB

ITEM

1 Heater Model 13 Yes No Yes No
2 User Code 13 Yes Yes Yes Yes
3 Date and Time 13 Yes Yes Yes Yes
4 Software Version 13 Yes No Yes No
5 Temperature Units 13 Yes Yes Yes Yes

6 Night Setback Temperature 13 Yes Yes Yes Yes
7 Night Setback Times 13 Yes Yes Yes Yes

1 Hours Running DHW 13 Yes No Yes No

2 Ignition Attempts 13 Yes No Yes No

3 Show Last 10 Errors 13 Yes No Yes No

1 Reset Last 10 Errors 13 No No Yes Yes

2 Service Mode Delay 13 No No Yes Yes

1 Tank Setpoint 14 Yes Yes Yes Yes

2 Tank Offset 14 No No Yes Yes

3 Tank Differential 14 No No Yes Yes

Description

See

Page

User Access Installer Access

Display Modify Display Modify

E

MODES

CONTROL

F

BMS

G

PUMPS

CIRCULATION

H

SERVICE

NOTIFICATION

1 Enable Input 14 No No Yes Yes

2 0-10V Building Management Input 14 No No Yes Yes

1 Voltage at Minimum 14 No No Yes Yes
2 Voltage at Maximum 14 No No Yes Yes
3 Minimum Power 14 No No Yes Yes

4 Maximum Power 14 No No Yes Yes

1 DHW Pump Delay 15 No No Yes Yes

1 Service Notification in Months 15 No No Yes Yes

2 Service Notification Running Hours 15 No No Yes Yes

3 Service Notification Cycles 15 No No Yes Yes

4 Reset Service Notification Counter 15 No No Yes Yes

5 Accept PPlug 15 No No Yes Yes

12

1 Service (continued)

Viewable and changeable control parameters

Service Manual

NOTICE

Before changing parameters, note the
settings so that the unit can be returned to
its original operating parameters.

A: General

Heater model

The control will display “VWH500 - 2000” as the model
number because the same control is used on several models.
This will be displayed when parameter A1 has been accessed.
This parameter is not changeable.

User code

The User Code allows the user to access and change a limited
number of control parameters. The access code can be changed
by the user or the installer to a code of their choosing. To
change the code, parameter A2 must be accessed. The default
code is 0101. The code can be changed one digit at a time by
using the arrow keys on the display.

Date and time

The control uses an internal clock for the night setback feature
and for logging of events. For these features to work correctly,
the clock must be set when the unit is first installed or any time
the unit has been powered off for more than 30 days. To set
the clock, parameter A3 must be accessed. The date and time
are displayed as “YY:MM:DD W hh:mm”. YY = year, MM =
month, DD = date, W = day (1 = Monday, 2 = Tuesday, etc.),
hh = hour (24 hour time; 2:00 PM = 14:00), mm = minutes.

NOTICE

Software version

The software version allows the user to view the software version
in use by the control. This software controls the operation of
the unit. When a new software version becomes available, the
existing control can be replaced with a new control to update
the software.

Temperature units

The control can be configured to display temperature in either
°C or °F. This parameter can be changed by the user or the
installer by accessing parameter A5. The default is °F.

Night setback temperature

Once the internal clock has been set correctly, the night setback
feature can be used to program a lower water temperature
setpoint for the tank. This parameter can be changed by the user
or the installer by accessing parameter A6. The temperature
range for this parameter is 32°F (0°C) to 261°F (127°C). If set
higher than the tank setpoint (parameter D1) the tank setpoint
will be used. The feature is turned off with a setting of 32.0°F
(0°C). The default value is 32.0°F (0°C).

The internal clock does not adjust for
Daylight Savings Time and therefore, will
require a manual adjustment.

Night setback times

If parameter A6 is set to anything other than 32.0°F (0°C), the
night setback feature becomes active. This will require start
and stop times to be programmed for the days that reduced
temperatures are required. These times can be changed by the
user or the installer by accessing parameter A7. Each day of the
week (Monday through Sunday) will have an on and off time.

Example: Monday ON: 22:30, Tuesday OFF: 6:45. If you wish
to skip a day and have no night setback, leave the on and off
times the same. The default times for each day will be 08:00
(OFF) and 18:00 (ON).

B: Data logging

Hours running DHW

The hours running DHW parameter shows the total number
of hours the unit has been in the DHW firing position. This
parameter can be viewed by the user and the installer by
accessing parameter B1.

Ignition attempts

The ignition attempts parameter shows the total number of
times the unit has attempted to fire. This parameter can be
viewed by the user and the installer by accessing parameter B2.

Show last 10 errors

The control will log the 10 most current errors with the date and
time the error occurred. This parameter can be viewed by the
user and the installer by accessing parameter B3.

C: Functions

Reset last 10 errors

The reset last 10 errors parameter allows the error counter to be
reset to 0. This parameter can only be cleared by the installer by
accessing parameter C1. Once accessed, press the SAVE/CLEAR
button to clear the counter.

Service mode delay

By pressing the hidden button on the front of the display for
five (5) seconds, the control will be placed in Service Mode.
This will override all other heat demands. The Service Mode
allows the installer to set the unit to any desired firing rate for
the purpose of combustion analysis. The delay sets the length of
time the unit will stay in the Service Mode if no keys have been
pressed before going back to its original state. This parameter
can only be changed by the installer by accessing parameter C2.
The time range of this parameter is 0 to 40 minutes. The default
value is 20 minutes.

13

1 Service

Service Manual

D: DHW settings

Tank setpoint

When a temperature sensor is installed in the tank, the tank
setpoint sets the target temperature of the water in the tank. The
user or installer can adjust this setpoint by accessing parameter
D1. The temperature range of this parameter is 60°F (15°C) to
190°F (88°C). The default value is 120°F (49°C).

Tank offset

The tank offset is the number of degrees the tank temperature
must go above the tank setpoint before the water heater will
turn off. The installer can adjust this setpoint by accessing
parameter D2. The temperature range of this parameter is 0° to
10°F (5°C). The default value is 4°F (2°C).

Tank differential

The tank differential is the number of degrees the tank
temperature must go below the tank setpoint before the heater
will start to heat the tank. The installer can adjust this setpoint
by accessing parameter D3 The temperature range of this
parameter is 0° to 40°F (22°C). The default value is 6°F (3°C).

E: Control modes

Enable input

The tank thermostat input can be used in two different ways.
When a tank aquastat is used, this input can start a heat demand
when the aquastat closes. When a tank sensor is used, this
input can be used to enable/disable the water heater using an
external contact. This setting can be used by the installer by
accessing parameter E1. To use this input with an aquastat, set
this parameter to “Aquastat”. To use this input with a remote
enable contact, set this parameter to “Remote Enable”. The
default setting is “Aquastat”.

0-10V building management input (BMS)

F: Building Management System (BMS)

Voltage at minimum

This setting determines the voltage at which the external
signal begins to increase either the modulation or the setpoint.
Below this voltage, the modulation or setpoint will be at
their minimum values. This parameter can be adjusted by
the installer by accessing parameter F1. The range for this
parameter is 0V - (F2 - 0.1V). The default value is 2V.

Voltage at maximum

This setting determines the voltage at which the external signal
forces the modulation to its maximum value. This parameter,
along with the previous parameter, determines how much
the modulation changes as the BMS input voltage changes.
The modulation will change in proportion to the change in
voltage between the minimum and maximum voltage settings.
This parameter may be adjusted by the installer by accessing
parameter F2. The range for this parameter is (F1 + 0.1V) ­10V. The default setting is 10V.

Minimum power

This setting determines the modulation of the unit when the
BMS input voltage is at or below the Voltage at Minimum
setting. This parameter is active only when the BMS type is set
to Power. This parameter can be as low as 25%. This parameter
may be adjusted by the installer by accessing parameter F3. The
range for this parameter is 0 - 100%. The default value is 20%.

Maximum power

This setting determines the modulation of the unit when the
BMS input voltage is at or above the Voltage at Maximum
setting. This parameter is only active when the BMS type is
set to Power. This parameter can be adjusted by the installer
by accessing parameter F4. The range for this parameter is 0 ­100%. The default value is 100%.

When the building management input is enabled, the control
modulates the unit based on the voltage on the 0-10V input on
the connection board. The 0-10V input controls the modulation
of the unit(s). This setting is adjustable by the installer by
accessing parameter E2. The default value is Inactive. See
menu Section F to adjust the parameters that control the BMS
operation.

14

1 Service (continued)

Service Manual

G: Circulation pumps

DHW pump delay

The DHW pump delay parameter sets the length of time the
DHW pump (if connected) will run after a DHW demand has
been satisfied. This parameter is adjustable by the installer by
accessing parameter G1. The time range for this parameter is 1
second to 40 minutes. The default time is 30 seconds.

H: Service Notification

Service notification in months

When the control determines that a scheduled service is due
based on days of installation, the display will alternate the
standard display text with the message SERVICE DUE every
5 seconds. This parameter is adjustable by the installer by
accessing parameter H1. The time range for this parameter is 0
months to 36 months. The default time is 12 months.

Service notification running hours

When the control determines that a scheduled service is due
based on the hours of actual operation, the display will alternate
the standard display text with the message SERVICE DUE
every 5 seconds. This parameter is adjustable by the installer by
accessing parameter H2. The time range for this parameter is 0
hours to 100,000 hours. The default time is 10,000 hours.

Accept PPlug

After replacing a control board, the new control will require
the installer to verify the model in which it is installed. As soon
as the power is turned on, the screen will display “Wrong ID
Plg”. Look behind the control panel at the connector plugged
into X5 on the control board. Note the number written on the
connector. Access parameter H5. That number should appear
after the word “Setting:” on the bottom line. If this number
matches the number on the connector, press the SAVE/CLEAR
button.

Service notification cycles

When the control determines that a scheduled service is due
based on the number of cycles, the display will alternate the
standard display text with the message SERVICE DUE every
5 seconds. This parameter is adjustable by the installer by
accessing parameter H3. The range for this parameter is 0 cycles
to 100,000 cycles. The default is 10,000 cycles.

Reset service notification counter

Once servicing has been completed, the service notification
counter should be reset. This parameter can be reset by the
installer by accessing parameter H4. Once accessed, press the
SAVE/CLEAR button to reset the service notification counter.

15

2 Maintenance

Maintenance and annual startup

Table 2A_Service and Maintenance Schedules

Service Manual

Service technician

(see the following pages for instructions)

General:

• Address reported problems

• Inspect interior; clean and vacuum if
necessary;

• Inspect condensate system and flush with
fresh water

• Check for leaks (water, gas, flue,
condensate)

• Examine venting system

• Check system water pressure/system
piping/expansion tank

• Check control settings

• Check igniter

• Check wiring and connections

ANNUAL START-UP

• Check flue gas passageways

• Flame inspection (stable, uniform)

Owner maintenance

• Check appliance area

Daily

Monthly

• Check pressure/temperature
gauge

• Check vent piping

• Check air piping

• Check relief valve

• Check condensate drain system

• Inspect and clean the burner

• Check manifold gas pressure

• Perform start-up checkout and
performance verification per Section 7
in the VF Series Installation and Operation
Manual.

If combustion or performance
indicate need:

• Clean heat exchanger

• Remove and clean burner using
compressed air only

• Clean the blower wheel

16

Every

6 months

• Test low water cutoff (if used)

• Reset button (low water cutoff)

• Check appliance piping (gas and
water) for leaks

• Operate relief valve

2 Maintenance (continued)

Service Manual

 WARNING

 WARNING

 WARNING

Follow the service and maintenance procedures given throughout this manual and in component literature
shipped with the appliance. Failure to perform the service and maintenance could result in damage to the
appliance or system. Failure to follow the directions in this manual and component literature could result in
severe personal injury, death, or substantial property damage.

The appliance should be inspected annually only by a qualified service technician. In addition, the maintenance
and care of the appliance designated in Table 2A and explained on the following pages must be performed to
assure maximum appliance efficiency and reliability. Failure to service and maintain the appliance and system
could result in equipment failure.

Electrical shock hazard – Turn off power to the appliance before any service operation on the appliance except
as noted otherwise in this instruction manual. Failure to turn off electrical power could result in electrical shock,
causing severe personal injury or death.

Address reported problems

1. Inspect any problems reported by the owner and correct
before proceeding.

Inspect appliance area

1. Verify that appliance area is free of any combustible
materials, gasoline and other flammable vapors and liquids.

Inspect appliance interior

Figure 2-1_Condensate Trap

1. Remove the outer access panels and inspect the interior of
the appliance.

2. Vacuum any sediment from inside the appliance and
components. Remove any obstructions.

Clean condensate system

1. Inspect the condensate drain line, condensate PVC fittings,
and condensate trap.

Flush condensate trap with water

1. Remove the four (4) screws securing the top cover to the
condensate trap and remove the cover (reference FIG. 2-1).

2. Locate the plastic ball inside the float tube. Verify there is
nothing under the ball causing it to not seat properly.

3. If necessary, flush with fresh water until the water begins to
pour out of the drain.

4. Replace the top cover on the condensate trap.

5. Replace the four (4) screws removed in Step 1.

Check all piping for leaks

1. Inspect all water and gas piping and verify to be leak free.

2. Look for signs of leaking lines and correct any problems
found.

3. Check gas line using the procedure found in Section 3 - Gas
Connections of the VF Series Installation and Operation
Manual.

17

2 Maintenance

Flue vent system and air piping

1. Check for gastight seal at every connection, seam of air
piping, and vent piping periodically inspected by a qualified
service agency.

 WARNING

Check water system

1. Verify all system components are correctly installed and
operational.

2. Watch the system pressure as the unit heats up (during
testing) to ensure pressure does not rise too high. Excessive
pressure rise indicates expansion tank sizing or performance
problem.

3. Inspect automatic air vents and air separators. Remove air
vent caps and briefly press push valve to flush vent. Replace
caps. Make sure vents do not leak. Replace any leaking
vents.

Check expansion tank

1. Expansion tanks provide space for water to move in and
out as the heating system water expands due to temperature
increase or contracts as the water cools. Tanks may be open,
closed, diaphragm or bladder type. See Section 4 - Water
Connections of the VF Series Installation and Operation
Manual for suggested best location of expansion tanks and
air eliminators.

Check relief valve

1. Inspect the relief valve and lift the lever to verify flow. Before
operating any relief valve, ensure that it is piped with its
discharge in a safe area to avoid severe scald potential. Read
Section 4 - Water Connections of the VF Series Installation
and Operation Manual before proceeding further.

Venting system must be sealed gastight
to prevent flue gas spillage and carbon
monoxide emissions, which will result in
severe personal injury or death.

 WARNING

 WARNING

2. After following the above warning directions, if the relief
valve weeps or will not seat properly, replace the relief valve.
Ensure that the reason for relief valve weeping is the valve
and not over-pressurization of the system due to expansion
tank waterlogging or undersizing.

Safety relief valves should be re-inspected
AT LEAST ONCE EVERY THREE YEARS,
by a licensed plumbing contractor or
authorized inspection agency, to ensure
that the product has not been affected by
corrosive water conditions and to ensure
that the valve and discharge line have not
been altered or tampered with illegally.
Certain naturally occurring conditions may
corrode the valve or its components over
time, rendering the valve inoperative. Such
conditions are not detectable unless the
valve and its components are physically
removed and inspected. This inspection
must only be conducted by a plumbing
contractor or authorized inspection agency
– not by the owner. Failure to re-inspect
the relief valve as directed could result in
unsafe pressure buildup, which can result in
severe personal injury, death, or substantial
property damage.

Following installation, the valve lever must
be operated AT LEAST ONCE A YEAR to
ensure that waterways are clear. Certain
naturally occurring mineral deposits may
adhere to the valve, rendering it inoperative.
When manually operating the lever, water
will discharge and precautions must be taken
to avoid contact with hot water and to avoid
water damage. Before operating lever, check
to see that a discharge line is connected to
this valve directing the flow of hot water
from the valve to a proper place of disposal.
Otherwise severe personal injury may result.
If no water flows, valve is inoperative. Shut
down the appliance until a new relief valve
has been installed.

Service Manual

18

2 Maintenance (continued)

Service Manual

Inspect/replace hot surface igniter

1. Turn off main electrical power to the appliance.

2. Turn off main manual gas shutoff to the appliance.

3. Carefully pull back the insulation flaps to expose the burner
mounting flange.

4. Locate the hot surface igniter. Disconnect the two power
leads to the hot surface igniter.

5. Loosen and remove the two wing nuts that mount the
igniter.

6. Lift the igniter vertically out of the burner mounting flange.
Use care, do not hit or break the silicon carbide igniter. Do
not contaminate the igniter by handling with oily or dirty
hands.

7. Check the replacement igniter for cracks or damage before
installing.

8. Ensure that the fiber gasket used to seal the base of the
igniter to the burner flange is reinstalled to seal the base of
the replacement igniter.

9. Carefully insert the igniter into the mounting point on the
burner flange and position on the mounting studs.

Perform start-up and checks

1. Start appliance and perform checks and tests specified
in Section 7 - Start-up of the VF Series Installation and
Operation Manual.

2. Verify cold fill pressure is correct and that operating
pressure does not go too high.

Check burner flame

Visually check main burner flames at each start-up after long
shutdown periods or at least every six months. A burner
viewport is located on the burner mounting flange.

 WARNING

Figure 2-2_Flame Pattern Illustration

The area around the burner viewport is hot
and direct contact could result in burns.

10. Reinstall the two wing nuts and tighten by hand only. Over
tightening the wing nuts may break the ceramic mounting
flange.

11. Ensure that the igniter gasket is properly installed and
seals the point of contact between the igniter and burner
mounting flange.

12. Reconnect the power leads to the igniter.

13. Replace the insulation blanket flaps.

14. Turn on main gas supply and main power.

15. Test fire the appliance to ensure proper operation.

Check all wiring

1. Inspect all wiring, making sure wires are in good condition
and securely attached.

Check control settings

1. Set the control module display to Parameter Mode and
check all settings. See Section 1 of this manual. Adjust
settings if necessary. See Section 1 of this manual for
adjustment procedures.

2. Check settings of external limit controls (if any) and adjust
if necessary.

Normal Flame: A normal flame at 100% of burner input is
blue, with slight yellow tips, a well defined flame and no flame
lifting.

Yellow Tip: Yellow tipping can be caused by blockage or partial
obstruction of air flow to the burner.

Yellow Flames: Yellow flames can be caused by blockage of
primary air flow to the burner or excessive gas input. This
condition MUST be corrected immediately.

Lifting Flames: Lifting flames can be caused by over firing the
burner, excessive primary air or high draft.

If improper flame is observed, examine the venting system,
ensure proper gas supply and adequate supply of combustion
and ventilation air.

19

2 Maintenance

Check flue gas passageways

Access to the burner will require the following steps:

Service Manual

Any sign of soot around the inner jacket, outer jacket, flue
pipe connections, burner or in the areas between the fins on
the copper heat exchanger indicates a need for cleaning. The
following cleaning procedure must only be performed by a
qualified serviceman or installer. Proper service is required to
maintain safe operation. Properly installed and adjusted units
seldom need flue cleaning.

CAUTION

 CAUTION

All gaskets/sealants on disassembled
components or jacket panels must be replaced
with new gaskets/sealants on reassembly.
Gasket and sealant kits are available from
your distributor.

When a Category IV vent system is
disconnected for any reason, the flue must
be reassembled and resealed according to the
vent manufacturer’s instructions.

Inspect and clean burner

The burner should be removed for inspection and cleaned
on an annual basis. An appliance installed in a dust or dirt
contaminated environment may require cleaning of the burner
on a 3 to 6 month schedule or more often, based on severity of
the contamination. The fan assisted combustion process may
force airborne dust and dirt contaminants, contained in the
combustion air, into the burner. With sustained operation,
non-combustible contaminants may reduce burner port area,
reduce burner input or cause non-warrantable damage to the
burner.

Use extreme care when operating an appliance for temporary
heat during new construction. Airborne contaminants such
as dust, dirt, concrete dust or drywall dust can be drawn into
the burner with the combustion air and block the burner
port area. An external combustion air filter is provided with
the appliance. This filter helps ensure clean air is used for the
combustion process. Check this filter every month and replace
when it becomes dirty. The burner of an appliance used for
temporary heat without a combustion air filter installed will
probably require a thorough cleaning before the unit is placed
into normal service.

1. Turn off main electrical power to the appliance.

2. Turn off main manual gas shutoff to the appliance.

3. Remove the front outer control panel covers. Slide out the
inner control panel to increase service clearances and
carefully remove the multi-pin wiring connectors on the
back of the control panel. Remove the screws along the
front and rear edge of the top outer jacket panel to remove
top. Remove the control panel to allow access to
the components in the top of the appliance.

4. Remove the sensing tubes from the low air pressure switch
to the combustion air blower.

5. Disconnect the wiring connections on the top of the
combustion air blower.

6. Remove the six (6) hex head bolts attaching the gas/air
venturi to the inlet of the combustion air blower.

7. Remove the four (4) nuts holding the combustion air
blower to the top of the burner and remove the combustion
air blower assembly.

8. Use care when removing the combustion air blower
assembly to prevent damage to the venturi and burner
gaskets.

9. Disconnect the power wires to the hot surface igniter.

10. Remove the hot surface igniter. The hot surface igniter is
fragile. Use care to prevent impact damage to the silicone
carbide igniter surface when removing the igniter.

11. Remove the eight (8) nuts holding the burner to the
heat exchanger.

12. The burner can now be lifted vertically out of the heat
exchanger chamber.

13. Use care when removing the burner to prevent damage
to the woven burner port surface or gaskets on removal.

14. Remove any visible dust or dirt blockage from the
surface of the burner with a vacuum. Compressed air
may also be blown across the burner surface to clean
the “pores” of the woven burner port material.

20

15. Reassemble in reverse order.

2 Maintenance (continued)

Service Manual

Checking manifold gas pressure

The gas manifold pressure tap is located on the venturi
connection of the gas manifold assembly (FIG. 2-3). The
manifold gas pressure tap can be accessed by removing the
upper left access panel on the front of the appliance.

Follow the steps below when checking manifold gas
pressure:

1. Turn the appliance power switch to the “OFF” position.

2. Turn the latch counterclockwise and open the upper
door.

3. Remove the screws along the front and rear edge of
the top outer jacket panel. Disconnect the ventilation
fan’s 2-pin connector hanging from the top panel
cover inside the unit. Remove the top outer jacket
panel.

4. Loosen the set screw on the venturi connection of
the gas manifold assembly one full turn from inside
the pressure tap to read manifold gas pressure. Place
the tubing of the manometer over the tap once the
set screw is loosened.

5. Turn the appliance power switch to the “ON” position.

6. Place the appliance into the active position by pressing
the SAVE/CLEAR button on the display board (see
page 5) until HTR:Standby appears in the display
window.

7. Locate the pinhole button below the SAVE/CLEAR
button (see page 5). Press the button once and hold for
five (5) seconds to place the appliance into Service
Mode. In Service Mode the appliance will fire and
operate at 100% of rate.

Figure 2-3_Gas Train Assembly

Table 2B_Gas Manifold Pressure Chart

Natural Gas

Model No.

500 -6.7 to -7.2 -7.9 to -8.4

750 -3.0 to -3.5 -4.0 to -4.5

1000 - 6.1 to -6.6 -8.4 to 8.9

1500 -3.9 to -4.6 -2.1 to -2.6

2000 -3.9 to -4.6 -2.1 to -2.6

10. Once the gas manifold pressure has been checked, press the
SAVE/CLEAR button on the display board to take the
appliance out of Service Mode. The appliance will go to
shutdown and the display will show HTR:OFF.

11. Turn the appliance power switch to the “OFF” position.

12. Remove the manometer and related fitting(s) from the
connection tap and replace the 1/8” hex plug (on F9 models
only).

Water Column

(w.c.)

LP Gas

Water Column

(w.c.)

8. As the appliance comes on and fires, record the inches
of water column of displacement on both sides of the
manometer. The sum of these two readings will be the
gas manifold pressure. Reference Table 2B - Gas
Manifold Pressure Chart for the proper measurement.

9. This is a reference pressure only and is not field
adjustable. An appliance supplied with the required
minimum gas supply pressure will operate at the
correct manifold gas pressure.

13. Replace the top jacket panel and reconnect the ventilation
fan’s 2-pin connector hanging from the top panel cover.

14. Replace the upper left access panel.

15. Turn the appliance power switch to the “ON” position.

16. Press the SAVE/CLEAR button on the display board until
HTR:Standby appears in the display window.

21

2 Maintenance

Combustion analysis procedure

1. Turn the appliance power switch to the “OFF” position.

2. Remove the flue temperature sensor from the flue pipe.
Note: Combustion measurements will be made at this
point.

3. Turn the appliance power switch to the “ON” position.

4. Place the appliance into the active position by pressing the
SAVE/CLEAR button on the display board (see page 5)
until HTR:Standby appears in the display window.

5. Locate the pinhole button below the SAVE/CLEAR
button. Press the button once and hold for 5 seconds to
place the appliance into Service Mode. In Service Mode the
appliance will fire and operate at 100% of rate.

6. Insert the probe from a combustion analyzer into the hole
left by the removal of the flue temperature sensor.

7. Compare the combustion measurement to the values listed
in Table 2C.

8. If the combustion is not within the specified range,
reference the Troubleshooting Chart below for possible
causes and corrective actions.

Table 2D_Combustion Troubleshooting Chart

Possible Cause

Vent / Air Intake
Length or Obstruction

Gas Supply Pressure

Service Manual

Corrective Action

- Refer to Section 2 - Venting in the
VF Series Installation and
Operation Manual for the proper
venting and air intake methods.

- Check for obstructions in the
vent / air intake terminals.

- Refer to Section 3 - Gas
Connections in the VF Series
Installation and Operation
Manual for the proper gas supply
for the VF Series.

Table 2C_Combustion Measurements

Model No.

500 - 1300 8.2 to 8.7 9.0 to 9.5

1500 8.6 to 9.1 9.6 to 10.1

2000 7.6 to 8.2 8.6 to 9.2

Natural Gas

CO2 (%)

LP Gas
CO2 (%)

- Refer to page 20 of this manual

Dirty / Damaged
Burner

Gas Valve Adjustment

9. Once the combustion analysis is complete, press the
SAVE/CLEAR button on the display board to take the
appliance out of Service Mode. The appliance will go to
shutdown and the display will show HTR:OFF.

10. Turn the appliance power switch to the “OFF” position.

11. Replace the flue temperature sensor into the flue pipe.

12. Turn the appliance power switch to the “ON” position.

13. Press the SAVE/CLEAR button on the display board until
HTR:Standby appears in the display window.

 WARNING

for burner removal and cleaning
procedures.

- Replace burner if necessary.

- Refer to page 23 of this manual
for the gas valve adjustment
procedure.

You must replace the flue temperature
sensor to prevent flue gas spillage into the
room. Failure to comply could result in
severe personal injury, death, or substantial
property damage.

22

2 Maintenance

2 Maintenance (continued)

Service Manual

Gas valve adjustment procedure

1. Turn the appliance power switch to the “OFF” position.

2. Remove the screws along the front and rear edge of
the top outer jacket panel. Disconnect the ventilation
fan’s 2-pin connector hanging from the top panel cover
inside the unit. Remove the top outer jacket panel.

3. Follow the Combustion Analysis Procedure on page 22
of this manual to measure combustion.

4. With the appliance operating in the Service Mode,
locate the throttle adjustment screw on the gas valve
(see FIG. 2-4) . Using an Allen wrench turn the throttle
adjustment screw a 1/4 turn counterclockwise to
increase CO2 levels and a 1/4 turn clockwise to decrease
CO2 levels.

5. After one adjustment of the valve, measure the
combustion.

6. If the combustion is still not within the specified range,
repeat the procedure. This procedure SHOULD NOT
be performed more than four (4) times. If after four
(4) adjustments the combustion is still not within the
specified range, revisit the possible causes in Table 2D
on page 22 of this manual.

7. Once the combustion analysis is complete, press the
SAVE/CLEAR button on the display board to take the
appliance out of Service Mode. The appliance will go
to shutdown and the display will show HTR:OFF.

8. Turn the appliance power switch to the “OFF” position.

9. Replace the flue temperature sensor into the flue pipe.

10. Replace the top jacket panel and reconnect the 2-pin
connector hanging from the top panel cover.

11. Replace the upper left access panel.

12. Turn the appliance power switch to the “ON” position.

13. Press the SAVE/CLEAR button on the display board
until HTR:Standby appears in the display window.

Figure 2-4_Throttle Adjustment Screw

 WARNING

Overfire and underfire hazards!
Possible fire, explosion, overheating,
and component failure. Do not attempt
to adjust firing rate of the water heater.
The firing rate must be adjusted only by
factory trained personnel.

23

2 Maintenance

Inspect and clean the heat exchanger

1. Turn off all power to the appliance.

2. Turn off main gas to appliance.

3. Remove the front outer jacket panel.

4. Remove the inner jacket panel (see FIG. 2-5).

5. Check the heat exchanger surface for soot. If soot is
present, the heat exchanger must be cleaned and the
problem corrected.

6. Remove the burner as described in the Inspect and
Clean Burner section of this manual.

7. Check the “V” baffles on the heat exchanger. Remove
and clean if necessary.

8. Remove soot from the heat exchanger with a stiff bristle
brush. Use a vacuum to remove loose soot from
surfaces and inner chamber.

9. The heat exchanger can be removed by disconnecting
all water piping to the heat exchanger, removing the
screws holding the heat exchanger to the top of the
inner jacket and sliding the heat exchanger towards the
front of the appliance. Once the heat exchanger is
removed, a garden hose can be used to wash the tubes
to ensure that all soot is removed from the heat
exchanger surfaces. Note: Do not wet the insulation

blankets on the inside of the outer jacket panels.

10. Ensure that any soot present on the burner is removed.
See Inspect and Clean Burner section.

11. Carefully reinstall the heat exchanger and “V” baffles if
removed from the appliance.

12. Reinstall the inner jacket panel, burner, manifolds,
wires, and hoses. Use new gasket material to ensure a
proper air seal.

13. Reassemble all gas and water piping. Test for gas leaks.

CAUTION

Upon completion of any testing on the gas
system, leak test all gas connections with a
soap and water solution while main burners
are operating. Do not spray soap and water
solution on the control module housing.
The use of an excessive amount of soap
and water solution can damage the control.
Immediately repair any leak found in the gas
train or related components. Do not operate
an appliance with a leak in the gas train,
valves, or related piping.

Figure 2-5_Location of the Heat Exchanger Inside
Jacket

Service Manual

Review with owner

1. Review the VF Series Installation and Operation Manual
with the owner.

2. Emphasize the need to perform the maintenance schedule
specified in this manual.

3. Remind the owner of the need to call a licensed contractor
should the appliance or system exhibit any unusual behavior.

4. Remind the owner to follow the proper shutdown procedure
and to schedule an annual start-up at the beginning of the
next heating season.

Oiled bearing circulators

Inspect the pump every six (6) months and oil as necessary. Use
SAE 30 non-detergent oil or lubricant specified by the pump
manufacturer.

14. Reassemble outer jacket panels.

15. Cycle unit and check for proper operation.

24

3 Troubleshooting

Service Manual

 WARNING

 WARNING

Label all wires prior to disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation. Always
disconnect power to the appliance before
servicing. Failure to comply could result in
severe personal injury, death, or substantial
property damage.

Never jumper (bypass) any device except
for momentary testing as outlined in the
Troubleshooting chart. Severe personal
injury, death, or substantial property damage
can result.

Before troubleshooting:

1. Have the following items:
a. Voltmeter that can check 120 VAC, 24 VAC, and
12 VDC.
b. Continuity checker.
c. Contact thermometer.

2. Check for 120 VAC (minimum 102 VAC to maximum

132 VAC) to appliance.

Check control module fuses

NOTICE

1. Turn OFF the power to the appliance at the external line
switch.

2. Remove front access cover.

3. Inspect fuses F1, F2, F3, F5, and F6, see FIG. 3-1 below.

Figure 3-1_Control Module Fuses

ALWAYS check control module fuses before
replacing control module or any major
components (blower, etc.). If one of these
fuses is blown, it can prevent the control
module or other components from operating.

3. Make sure either the tank thermostat or tank sensor is

calling for heat. If the enable input is set to remote enable
(see page 14), the tank thermostat input must be closed
and the tank temperature sensor must be below the DHW
setpoint minus the tank differential. Check for 24 VAC
between the tank thermostat connections and ground.

4. Make sure all external limit controls are installed and

operating.

Check the following:

1. Wire connectors to control module are securely plugged in

at the module and originating control.

2. Gas pressures:

Refer to Section 3 - Gas Connections of the VF Series
Installation and Operation Manual for detailed information
concerning the gas supply.

4. The appliance is shipped with three (3) spare fuses in a
plastic bag attached to the control panel.

5. If necessary, replace open fuse (F1 and F6 are 1.6 amps, F3
is 3.15 amps, F2 and F5 are 5 amps).

Note: Fuses F1 - F6 are all slow blow fuses.

 WARNING

6. Install front access cover after fuse inspection.

Do not jumper fuse or replace with any fuse
except as specified. Failure to comply could
result in severe personal injury, death, or
substantial property damage.

7. Restore power to the appliance at the external line switch

and verify water heater operation (Section 7 - Start-up in
the VF Series Installation and Operation Manual) after
completing water heater service.

25

Service Manual

3 Troubleshooting

Table 3A Troubleshooting Chart - No Display

FAULT CAUSE CORRECTIVE ACTION

• Check external line switch, fuse, or breaker.

• Check position of ON/OFF switch. Turn switch to the

No Display

- No 120 VAC supplied to unit.

- Bad wiring connection.

ON position.

• Check 120 VAC through the ON/OFF switch. No
voltage through switch, replace switch.

• Check wiring harness connection between the display
board and the main control board. Connect the harness
at both points.

No Burner

Operation

Unit Does

Not Modulate

Above 50%

- Blown fuse.

- Bad display board. • Replace board.

- Bad main control board. • Replace main control board.

- Main control board temperature setpoint
satisfied.

- Remote enable switch open.

- Unit locked out on fault.

- Controlled by BMS. • Check BMS parameter settings.

• Replace fuse F6 on the main control board, see
FIG. 3-1 on page 25 of this manual.

• Review temperature setting.

• Review tank thermostat setting.

• Consult display for specific fault. Refer to fault
descriptions on pages 29 - 35 of this manual for
corrective actions.

26

Service Manual

3 Troubleshooting (continued)

Checking temperature sensors

The appliance temperature sensors (inlet water, outlet water, system water, tank water, flue, and outdoor air) are all resistance
type devices. The following tables show the correct values for the sensors at various temperatures. Use an ohmmeter to read
the resistance of the sensor at a known temperature. If the resistance of the sensor does not closely match its corresponding
table, replace the sensor.

Table 3B Inlet/Outlet Resistance vs. Temperature

Temperature (°F) Resistance Temperature (°F) Resistance

50 18,780 158 1,990

68 12,263 176 1,458

86 8,194 194 1,084

104 5,592 212 817

122 3,893

140 2,760

Table 3C Flue Temperature Sensor Resistance vs. Temperature

Temperature (°F) Resistance Temperature (°F) Resistance

68 125,500 158 16,870

77 100,000 176 12,000

86 80,220 194 8,674

104 52,590 212 6,369

122 35,270 230 4,744

140 24,160 248 3,581

Table 3D Tank Sensor Resistance vs. Temperature

Temperature (°F) Resistance Temperature (°F) Resistance

32 32,650 158 1,752

50 19,900 176 1,258

68 12,490 194 918

86 8,057 212 680

104 5,327

122 3,603

140 2,488

27

Service Manual

3 Troubleshooting

Table 3E Troubleshooting Chart - Noisy System

FAULT CAUSE CORRECTIVE ACTION

- Gas supply problem. • Refer to Section 3 - Gas Connections of the VF Series
Installation and Operation Manual for detailed
information concerning the gas supply.

- Gas/air mixture problem. • Refer to the Checking Manifold Gas Pressure and
Combustion Analysis Procedure on pages 21 and 22 of
this manual for the proper settings. Verify
that the vent/air intake lengths do not exceed the
maximum listed in the Venting section of the VF Series
Installation and Operation Manual.

Noisy

Operation

No Pump

Operation

- Dirty/damaged burner. • Refer to page 20 in this manual for the burner removal
and inspection procedure. Clean or replace the burner
as necessary.

- Low water flow through the heat exchanger. • Refer to Section 4 - Water Connections of the
VF Series Installation and Operation Manual for
minimum flow rates. Verify that the appliance is piped in
a primary/secondary fashion and that the appliance and
system pump are running on a call for heat.

- Air in the piping system. • Properly purge all air from the piping system.

- Low system water pressure. • Verify system pressure is a minimum of 12 PSI.

- Faulty pump.

- Internal fault on control board.

- System pressure exceeds relief valve

setting.

• Replace pump.

• Replace main control board.
Note: Make sure the pump horse power (hp) does not

exceed 1 hp.

• Lower the system pressure below the rating of
the supplied relief valve.

Relief Valve

Opening

28

- Improperly sized expansion tank. • Install properly sized expansion tank.

- Outlet water temperature in excess of 210°.

• Check setpoint of temperature control.

• Check temperature rise across heat exchanger. Refer to
the temperature rise chart in Section 4 - Water
Connections of the VF Series Installation and Operation
Manual.

3 Troubleshooting (continued)

Table 3F Troubleshooting Chart - Fault Messages Displayed on Operator Interface

FAULT DESCRIPTION CORRECTIVE ACTION

• Reset the pressure switches.

Service Manual

Gas Pressure SW

(Will require a manual

reset once the condition

has been corrected.)

Flow Switch/

LWCO

(Lockout will reset
automatically after

5 minutes or may be

reset immediately once

condition has been

corrected. Press the

SAVE/CLEAR button on

the display to reset.)

Blocked Drain SW

(Lockout will reset
automatically after

5 minutes or may be

reset immediately once

condition has been

corrected. Press the

SAVE/CLEAR button on

the display to reset)

Either the optional manual reset low gas
pressure switch or the optional manual reset
high gas pressure switch tripped.

Either the flow switch or the optional low
water cutoff is not making.

The blocked drain switch has detected
excessive condensate build up inside the
unit.

• Measure the supply gas pressure to determine
cause of failure. Refer to Section 3 - Gas
Connections of the VF Series Installation and
Operation Manual for detailed information
concerning the gas supply.

• Correct the supply gas pressure if necessary.

• Check pump operation on a call for heat.

• Check for closed valves or obstructions in the
water piping.

• Verify system is full of water and all air has been
purged from the system.

• Check condensate tube from unit to floor drain for
proper installation and obstructions.

• Inspect condensate trap for blockage. Clean if
necessary.

• Check for loose wiring connection at wire harness
plug.

• Bad blocked drain switch. Replace switch.

Flame Sequence

(Will require a manual

reset once the condition
has been corrected. Press
the SAVE/CLEAR button

on the display to reset.)

The flame detector circuit is seeing a flame
signal while no flame is present.

• Check supply voltage for proper polarity.

• Check external wiring for voltage feedback.

• Check the internal wiring for bad connections.

• Replace main control board.

29

Service Manual

3 Troubleshooting

Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Operator Interface

FAULT DESCRIPTION CORRECTIVE ACTION

• Inspect igniter and associated wiring for damage and
connection. Reference page 20 of this manual for
removal and cleaning procedure. Replace if
necessary.

• Check for proper electrical grounding of unit.

• Check incoming supply gas pressure. Refer to
Section 3 - Gas Connections in the VF Series
Installation and Operation Manual for detailed
information concerning the gas supply.

• Verify that the tube from the gas valve to the air inlet is

No Flame Ign

(Will require a manual
reset. Press the SAVE/

CLEAR button on the

display to reset.)

The unit has failed to prove main burner
flame upon ignition.

connected and is not damaged.

• Verify that the vent/air intake pipes are correctly
installed and that there are no obstructions.

• Inspect the burner. Reference page 20 of this manual
for removal and cleaning procedures. Replace if
necessary.

HSI Current Low

(Will require a manual

reset once the condition

has been corrected. Press

the SAVE/CLEAR button

on the display to reset.)

Flame CKT

Error

Amp draw of the hot surface igniter did not
meet the minimum requirement of 2.6 amps.

The main control board has detected an
internal fault.

• Refer to the Checking Manifold Gas Pressure and
Combustion Analysis Procedure on pages 21 and 22
of this manual for the proper settings.

• Check for 120 VAC to the gas valve during the ignition
attempt. If no voltage is present, check the wiring
between the gas valve and the main control board.

• Replace the wiring or the main control board as
necessary.

• Measure the amp draw of the hot surface igniter during
the trial for ignition stage. If less than 2.6 amps
replace the hot surface igniter.

• If more than 2.6 amps replace the control module.

• Replace the main control board.

30

Service Manual

3 Troubleshooting (continued)

Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Operator Interface

FAULT DESCRIPTION CORRECTIVE ACTION

The unit was running and lost the flame signal. • Inspect igniter and associated wiring for damage and

connection. Reference page 20 of this manual for
removal and cleaning procedure. Replace if
necessary.

• Check for proper electrical grounding of unit.

• Check incoming supply gas pressure. Refer to
Section 3 - Gas Connections of the VF Series
Installation and Operation Manual for detailed

No Flame

Running

(Will require a manual

reset once the condition

has been corrected. Press

the SAVE/CLEAR button

on the display to reset.)

information concerning the gas supply.

• Verify that the tube from the gas valve to the air inlet
is connected and is not damaged.

• Verify that the vent/air intake pipes are installed
correctly and there are no obstructions.

• Refer to the Checking Manifold Gas Pressure and
Combustion Analysis Procedure on pages 21 and 22
of this manual for the proper settings.

Auto Reset

High Limit

The outlet water temperature has exceeded the
fixed setting of the automatic reset high limit.

• Inspect the burner. Reference page 20 of this
manual for removal and cleaning procedures.
Replace if necessary.

• Replace the main control board.

• Verify that the system is full of water and that all air
has been properly purged from the system.

• Verify that the appliance is piped properly into the
heating system. Refer to Section 4 - Water
Connections of the VF Series Installation and
Operation Manual for the proper piping methods
for the VF Series.

• Check 120 VAC to DHW pump motor on a call for
heat. If voltage is not present, check wiring back
to the main control board. Replace the main
control board if necessary.

• If 120 VAC is present on a call for heat and the
pump is not operating, replace the pump.

• If the system pump is a variable speed pump,
ensure that the system flow is not less than the
flow.

• Check temperature setting of the main control
board.

• Check resistance of water sensors and compare to
Table 3B on page 27 of this manual. Replace
sensor if necessary.

• Replace high limit.

31

Service Manual

3 Troubleshooting

Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Operator Interface

FAULT DESCRIPTION CORRECTIVE ACTION

• Verify setting of adjustable high limit.

• Verify that the system is full of water and that all air
has been properly purged from the system.

• Verify that the appliance is piped properly into the
system. Refer to Section 4 - Water Connections of

Manual Reset

High Limit

(Will require a manual

reset once condition

has been corrected.

Press the SAVE/CLEAR

button on the display to

reset.)

The outlet water temperature has exceeded
the setting of the adjustable high limit.

the VF Series Installation and Operation Manual for
proper piping methods for the VF Series.

• Check 120 VAC to the pump motor on a call for heat.
If voltage is not present, check wiring leading to the
main control board. Replace the main control board if
necessary.

• If 120 VAC is present on a call for heat and the pump
is not operating, replace the pump.

• If the system pump is a variable speed pump, ensure
the system flow is not less than the flow.

• Check temperature setting of the main control board.

• Check resistance of water sensors and compare to
the tables on page 27 of this manual. Replace the
sensor if necessary.

• Replace high limit.

Inlet Low

Fan Low

OR

Fan Speed Low

(Will require a manual

reset once condition

has been corrected.

Press the SAVE/CLEAR

button on the display to

reset.)

The inlet water temperature did not exceed
130° within 15 minutes of ignition.

The actual fan RPM is 30% lower than what
is being called for.

Blown fuse.

• Raise temperature setpoint above 130°.

• Install a 3-way valve per the piping diagram in
Section 4 - Water Connections of the VF Series
Installation and Operation Manual.

• Replace the main control board.

• Vent/air intake lengths exceed the maximum allowed
lengths. Refer to Section 2 - Venting of the
VF Series Installation and Operation Manual for
proper lengths.

• Check for obstruction or blockage in the vent/air
intake pipes or at terminations.

• Check wiring connections at the fan and at the
main control board.

• Replace the fan.

• Replace the main control board.

• Replace fuse F3 on the main control board, see
page 25 of this manual.

32

Service Manual

3 Troubleshooting (continued)

Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Operator Interface

FAULT DESCRIPTION CORRECTIVE ACTION

• Vent/air intake lengths exceed the maximum

Fan High

OR

Fan Speed High

(Will require a manual

reset once the condition
has been corrected. Press
the SAVE/CLEAR button

on the display to reset.)

The actual fan RPM is 30% higher than what
is being called for.

allowed lengths. Refer to Section 2 - Venting of the
VF Series Installation and Operation Manual for
proper lengths.

• Check for obstruction or blockage in the vent/air
intake pipes or at terminations.

• Check wiring connections at the fan and at the
main control board.

• Replace the fan.

• Replace the main control board.

Flue Open

OR

Flue Shorted

Sensor Open

(Will require a manual

reset once the condition
has been corrected. Press
the SAVE/CLEAR button

on the display to reset.)

Sensor Shorted

(Will require a manual

reset once the condition
has been corrected. Press
the SAVE/CLEAR button

on the display to reset.)

Louver Proving

(Lockout will reset
automatically after

5 minutes or may be

reset immediately once

condition has been

corrected. Press the

SAVE/CLEAR button on

the display to reset.)

The flue sensor wiring has been
disconnected, grounded, or the flue sensor
has been removed from the flue.

Either the inlet water or outlet water
temperature sensor has been disconnected.

Either the inlet water or outlet water
temperature sensor has been shorted.

An optional remote proving switch is not
making.

• Check the sensor and associated wiring. Repair or
replace sensor or wiring if damaged.

• Reinstall sensor in flue outlet.

• Check the sensors and their associated wiring.
Repair or replace the sensor or wiring if damaged.

• Measure the resistance of the sensors and compare
the resistance to the tables on page 27 of this
manual.

• Replace the sensor if necessary.

• Check the sensors and their associated wiring.
Repair or replace the sensor or wiring if damaged.

• Measure the resistance of the sensors and compare
the resistance to the tables on page 27 of this
manual.

• Replace the sensor if necessary.

• Check function of remote devices.

• Check for loose or misplaced jumper if proving switch
is not installed.

Tank Open

APS Open

(Lockout will reset

automatically after 5

minutes or may be

reset immediately once

condition has been

corrected. Press the

SAVE/CLEAR button on

the display to reset.)

Tank sensor not connected.

The air pressure switch did not make within
1 minute after the combustion air blower has
been energized.

• Repair or replace the sensor wiring if damaged.

• Replace the sensor if necessary.

• Check air filter. Clean or replace as necessary.

• Vent/air intake lengths exceed the maximum allowed
lengths.

• Check for blockage or obstruction in vent/air inlet pipe
or at terminations.

• Verify combustion air blower is operating. Replace if
necessary.

33

Service Manual

3 Troubleshooting

Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Operator Interface

FAULT DESCRIPTION CORRECTIVE ACTION

APS Closed

(Lockout will reset

automatically after 5

minutes or may be

reset immediately once

condition has been

corrected. Press the

SAVE/CLEAR button on

the display to reset.)

Wrong ID Plug

The control sensed that the air pressure
switch was closed before the combustion air
blower was energized.

Control module ID plug does not match
parameter H5.

• Check for jumper on air pressure switch.

• Check for an unusually high negative draft in the vent
stack.

• Verify that ID plug is connected properly to connector
X5 on the control module.

• Verify that the wiring in the ID plug is not cut or
damaged and that the wiring connectors are seated
properly in the plug.

• Verify that the number on the ID plug matches the
number in parameter L5. If not, replace the control
module.

• When replacing control modules, verify that the
number in parameter L5 matches the number on the
ID plug. If so, press the SAVE/CLEAR button on the
display. If not, replace the control module.

Temp O/Shoot

(Lockout will reset

automatically after 5

minutes or may be

reset immediately once

condition has been

corrected. Press the

SAVE/CLEAR button on

the display to reset.)

The stack temperature has exceeded the set
parameters for the water heater.

The temperature rise across the heat
exchanger has exceeded the set parameters
for the appliance.

• Inspect the heat exchanger. Reference page 20 of
this manual for the procedure on how to clean the flue
side of the heat exchanger.

• Inspect the flue sensor and associated wiring.
Measure the resistance of the flue sensor and
compare to Table 3C on page 27 of this manual.
Replace the sensor if necessary.

• Verify that the vent/air intake pipes are properly
installed and that there are no obstructions.

• Replace the main control board.

• Verify that the system is full of water and that all air
has been properly purged from the system.

• Verify that the appliance is piped properly into the
heating system. Refer to Section 4 - Water
Connections of the VF Series Installation and
Operation Manual for the proper piping methods.

• Check for 120 VAC to the pump motor on a call
for heat. If voltage is not present, check the wiring
leading to the main control board. Replace the main
control board if necessary.

• If 120 VAC is present on a call for heat and the
pump is not operating, replace the pump.

34

Service Manual

3 Troubleshooting (continued)

Table 3F (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Operator Interface

FAULT DESCRIPTION CORRECTIVE ACTION

• Verify that the system is full of water and that all air
has been properly purged from the system.

Temp O/Shoot

(continued)

(Lockout will reset
automatically after

5 minutes or may be

reset immediately once

condition has been

corrected. Press the

SAVE/CLEAR button

on the display to reset.)

Rem Ctrl Flt

Service Blk

Low Voltage

Watch Dog Error

Outlet water temperature has exceeded the
maximum outlet water temperature.

External control is cycling too often.

While the unit is in Service Mode, the outlet
temperature has exceeded 185°F (85°C).

120 VAC input to the main control board has
dropped below 80 VAC.

The main control board has detected an
internal fault.

• Verify that the appliance is piped properly into the
system. Refer to Section 4 - Water Connections of
the VF Series Installation and Operation Manual for
the proper piping methods.

• Check 120 VAC to the pump motor on a call for heat.
If voltage is not present, check wiring leading to the
main control board. Replace the main control board
if necessary.

• If 120 VAC is present on a call for heat and the pump
is not operating, replace pump.

• Replace the main control board.

• Check setpoint of the external control.

• Check the wiring between the external control and
the unit.

• Replace the control.

• Establish a heating load to remove heat from the
system.

• Verify that the system is full of water and that all air
has been properly purged from the system.

• Verify that the appliance is piped properly into the
system. Refer to Section 4 - Water
Connections of the VF Series Installation and
Operation Manual for the proper piping methods.

• Check 120 VAC to the pump motor on a call for
heat. If voltage is not present, check the wiring
leading to the main control board. Replace the main
control board if necessary.

• If 120 VAC is present on a call for heat and the
pump is not operating, replace the pump.

• Check 120 VAC supply to the transformer.

• Check wiring connections at the low voltage terminal
strip.

• Check the wire size/length to remote devices.

• Replace the main control board.

• Replace the main control board.

Write EEProm

Program EEProm

CRC Parameters

No Error Stored

The main control board has detected an
internal fault.

The main control board has detected an
internal fault.

The main control board has detected an
internal fault.

The main control board has detected an
internal fault.

• Replace the main control board.

• Replace the main control board.

• Replace the main control board.

• Replace the main control board.

35

Revision Notes: Revision A (ECO C12846) initial release.

VFS-SER Rev A

06/13