Bradford White UCG100H3993N User manual

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Manual 238-51306-00B REV 11/15
SERVICE
MANUAL
Troubleshooting Guide
and Instructions for Service
(To be performed ONLY by
qualified service providers)
Effective: November, 2015
ECO 7964
Models Covered
by This Manual:
UCG(80,100)H399*(N,X)
(*) Denotes Warranty Years
Ultra Low NOx Atmospheric Vent
Water Heaters with Direct Spark Ignition

2
Ultra Low NOx Atmospheric Vent Water Heaters
with Direct Spark Ignition
Table of Contents
Introduction...................................................................................................................3
How to Use This Manual ..............................................................................................4
Tools Required for Service...........................................................................................4
Features .......................................................................................................................5
Specifications ...............................................................................................................6
Sequence of Operation ................................................................................................9
Troubleshooting.......................................................................................................... 11
Service Procedure I: Thermostat Circuit Testing and Replacement..........................16
Service Procedure II: Combustion System Testing and Replacement......................21
Service Procedure III: Burner Tube Inspection and Replacement ............................25
Service Procedure IV: Gas Valve Replacement........................................................27
Service Procedure V: Blower Testing and Replacement ..........................................28
Service Procedure VI: Flame Sensor Testing and Replacement ..............................30
Service Procedure VII: Spark Rod Gap Adjustment and Replacement.....................32
Service Procedure VIII: Ignition Module/Control Board Replacement....................... 34
Service Procedure IX: Blocked Vent Switch Inspection and Replacement ...............35
Service Procedure X: Anode Inspection and Replacement ......................................36
Service Procedure XI: Display Module Replacement................................................ 37
Service Procedure XII: Transformer Replacement....................................................38
Water Heater Installation Check list ...........................................................................39
Water Heater Service Report ..................................................................................... 40
Parts List ....................................................................................................................41
Glossary of Terms ......................................................................................................44
Notes..........................................................................................................................44
2

SAVE THIS MANUAL FOR FUTURE REFERENCE REV 11/15 238-51306-00B
Introduction
The Bradford White Ultra Low NOx Atmospheric Vent Water Heater is designed to deliver a
remarkable amount of hot water at up to 82% thermal efficiency in a quiet running unit with a top
exhaust vent connection that allows for installation in existing locations. While this unit is vented
atmospherically there is no damper required to maintain heat loss during off cycle. Several
technologically advanced design features are incorporated that will require additional knowledge on
the part of the qualified service provider. The information in this manual will instruct service and
maintenance professionals on the function, proper diagnosis and repair of The Bradford White Ultra
Low NOx Atmospheric Vent Water Heater.
The Bradford White Ultra Low NOx Atmospheric Vent Water Heater uses an ultra low NOx premix
power burner located at the top of the water heater to direct a turbulent flame down into the water
backed combustion chamber. This turbulence causes a thorough mixing of gas and air for optimum
combustion. The combustion gases then travel through a two pass flue system keeping the gases
moving at a high velocity. The combination of high turbulence and velocity results in an optimum
transfer of heat from the flue gases into the water.
Burner operation is controlled using an electronic ignition module. The module monitors the status of
the electronic thermostat, blocked vent limit switch, flame sensor to control output voltage to blower
motor, spark rod and gas valve. The module contains programming which determines the sequence
of operation and timings for purge periods, trial for ignition, flame sensing and lockout. The module
will also provide diagnostic information to help in determining the cause of system lockouts.
The contents in this manual are detailed informational tools to assist in the proper diagnosis of the
Ultra Low NOx Atmospheric Vent Water Heater operational faults. Please read this service manual
completely and record as much information regarding the Ultra Low NOx Atmospheric Vent Water
Heater operation and installation specifics related to any concerns.
3

4
How to Use This Manual
It is intended for this manual to be used by qualified service personnel for the primary purpose of
troubleshooting analysis and repair of the Bradford White UCG100H399. Understanding the
sequence of operation section of this manual will contribute greatly to troubleshooting this product.
An “Installation Check List” is shown towards the end of this manual. Compare the installation against
the installation check list to confirm all requirements are met.
A “Service Report” is shown towards the end of this manual. Completing this form will assist in the
troubleshooting efforts. Should you need to call for technical support, please provide the information
shown on this form to the support technician to help ensure accurate troubleshooting.
Troubleshooting begins with “System Observation” to determine failure mode as indicated by the
error code on the system display. Troubleshooting continues with “Failure Modes and Probable
Cause” directing the service provider to a series of test procedures to determine root cause of failure.
Component replacement procedures directly follow the test procedures for a given component.
In some difficult to diagnose conditions, it may be necessary to isolate the heater from the vent
system to determine root cause.
Contact Technical support immediately if diagnosis is not determined using the methods described in
this service manual.
Tools Required for Service
Manometer: Two types available, a liquid “U” tube type or a digital (magna-helic) type. This device is
used to measure gas and/or air pressures and vacuum.
Multi-Meter: A digital type is strongly recommended. This device is used to measure electrical
values. The meter you select must have the capability to measure volts AC, volts DC, Amps, micro-
amps and ohms.
Thermometer: Used to measure water temperature. An accurate thermometer is recommended.
Water Pressure Gage: Used to measure water supply pressure. Also used to determine tank
pressure by adapting to the drain valve of the heater.
Jumper Leads: A length of wire (12" min.) with alligator clip at both ends.
Various Hand Tools: Pipe wrench, channel locks, open end wrench set, 12" crescent wrench, Allen
wrench set, torx bit set, screw drivers (common & phillips), long reach (12") magnetic tip phillips head
screw driver #2 tip, ¼" nut driver, pliers (common & needle nose), socket set including a 1-1/16 deep
well socket, wire cutters, wire strippers, wire crimpers, torpedo level, small shop vac, step ladder, and
flashlight.
4

5
Features
Features of Honeywell Integrated Control System

xAttractive digital water heater display on control panel for setting and displaying the temperature
setpoint. Pressing temperature UP and DOWN buttons changes the temperature setpoint.
Temperature format may be displayed in °F or °C.
xSingle control board with plug in wiring controls temperature, ignition, and blower operation.
xReduced number of parts for servicing and wiring.
xPlug in wiring reduces chance of miswiring.
xBurner ignition with direct spark ignition - A high voltage spark jumps from the spark rod to the
burner surface to ignite the gas. Eliminates burned out hot surface igniter replacements.
xWater heater display will show diagnostic codes in the event the water heater needs servicing.
Aids in diagnosing and servicing the water heater.
xWater heater display can show previous error code history to further aid in servicing the water
heater.
5

6
Specifications
Model Description Dimensions (INCHES)
Model No.
Input
Rate
BTU/h
Storage
Capacity
U.S.
Gallons
A
Floor
to
Top
of
Vent
B
Vent
Dia.
C
Floor
to
Cold
Water
Conn.
D
Floor
to
T&P
E
Floor
to Hot
Water
Conn.
F
Floor
to Top
of
Water
Heater
G
Floor
to
Gas
Conn.
H
Depth
J
Jacket
Dia.
K
Floor
to
Top
Conn.
Water
Conn.
Dia.
Gas
Conn.
Dia.
Relief
Valve
Open
Shipping
Weight
(lbs)
UCG100H399 399,000 100 77 ¼ 8 10 52 ½ 55 ½ 69 ¾ 63 ¼ 30 28 ¼ 63 ¼ 1 ½ ¾ 1 657
UCG80H399 399,000 80 68 ¾ 8 10 44 47 61 ¼ 55 ¾ 30 28 ¼ 55 ¾ 1 ½ ¾ 1
Model Description Dimensions (MM)
Model No.
Input
Rate
KW
Storage
Capacity
Liters
A
Floor
to
Top
of
Vent
B
Vent
Dia.
C
Floor
to
Cold
Water
Conn.
D
Floor
to
T&P
E
Floor
to Hot
Water
Conn.
F
Floor
to Top
of
Water
Heater
G
Floor
to
Gas
Conn.
H
Depth
J
Jacket
Dia.
K
Floor
to
Top
Conn.
Water
Conn.
Dia.
Gas
Conn.
Dia.
Relief
Valve
Open
Shipping
Weight
(kg)
UCG100H399 117.2 371 1962 203 254 1334 1410 1772 1607 762 718 1607 38 19 25 297
UCG80H399 117.2 297 1746 203 254 1118 1194 1556 1416 762 718 1416 38 19 25
6

7
Specifications
Power Supply Dedicated 120 VAC, 60 Hz, 15A GFI
Gas Supply Minimum 1” Nat
(Schedule 40 black iron pipe recommended)
Approved gas Type Natural. Unit must match gas type supplied
Gas Pressure (Nat.) 14.0” W.C. maximum static, 4.5” W.C. minimum running
(recommend 7.0” W.C. min running)
Venting System
Atmospherically Vented, Type B Venting system or
approved chimney. Follow the current National Fuel
Gas Code requirements or in Canada, the Natural Gas
and Propane Installation Code.
Minimum Clearance for
Servicing 18” from top, 24” from front, 4” sides and rear.
Maximum Water Supply
Pressure 150 PSI
Thermostat Sensor
11,900 Ohms @ 70°F, ECO opens @ 207°F Max.
Redundant sensor for ECO. Sensor inside well for easy
replacement of sensor.
Control Display
Digital display, 24 volts. temperature Range: 70-180
degree F. Used to set tank temperature (deg. F or deg.
C), show operating status, display error codes, error
code history, limit maximum setpoint temperature.
Control Board
Operates from 24 volt from transformer. Controls tank
temperature, ignition functions, combustion blower. See
ignition timings in sequence of operation for Integrated
Control.
Transformer 120 VAC primary, 24 VAC secondary, 40 VA.
Spark Rod Igniter 0.22” nominal gap to the burner surface.
Flame Sensor Output Minimum 1 micro amp. Typical range 5 to 30 micro
amps.
Gas Valve Negative regulation, 24 VAC, ½” PSI max., 4.5” W.C.
minimum running inlet.
Vent Safety Switch Normally closed, opens @ 240°F, manual reset.
Blower 120 VAC, 60 Hz, 1.5-3.5 amps, 8000 RPM
Combustion Levels CO2: 8-11%, CO: less than 0.04% (400 PPM) air free

7

8
Specifications
Vent Tables
(Intake Only)
Model Number Max Intake Vent Length (feet) 3" Max Intake Vent Length (feet) 4"
UCG100H399 25 50
UCG80H399 25 50
WARNING! The UCG(80,100)H399 model is not approved for 2 inch diameter vent pipe. Venting with 2 inch pipe may
result in damage to the water heater or cause an unsafe condition. DO NOT use 2 inch Vent Air Intake Pipe!
Determining required intake vent length
1. Determine the total length of straight vent pipe (in feet) required for the intake.
2. Add 5 feet of venting for every 90° elbow.
3. Add 2 ½ feet of venting for every 45° elbow.
4. Total vent length cannot exceed “Max Intake Vent Length” on the venting table shown above.
Example of Total Intake Vent Length for UCG100H399 installation:
A 3” venting system has a total of two 90-degree elbows and a total straight pipe length of 10 feet.
Equivalent vent length for elbows: 2 x 5 feet = 10 feet.
Total equivalent vent distance = 10 feet + 10 feet = 20 feet total equivalent vent length. This is below
the maximum allowed distance of 25 feet for this model using 3” vent.
8

9
Sequence of Operation
1. Thermostat calls for heat.
2. Combustion blower starts.
3. Blower pre-purge period of 30 seconds.
4. Trial for Ignition. (5 seconds, 3 trials).
a. Flame establishing period (3 seconds), gas valve opens, sparks from spark rod to burner surface to ignite
the gas.
b. Burner on, flame proving period (2 seconds). Requires a minimum of 1.0 microamp through flame sense
rod to prove flame.
c. If the blocked vent safety switch contacts (normally closed) opens, then the ignition sequence will not
start and an error code 67 (Vent safety switch failed to close/open) will be shown on the display.
5. Steady State Operation: Burner continues to operate until:
a. Thermostat circuit opens, gas valve closes, blower continues to operate for 30 second post-purge period.
b. If the normally closed blocked vent safety switch opens, the gas valve closes, the blower continues to
operate indefinitely and error code 67 will be displayed after a couple minutes (up to 5 minutes) with
“Service Needed.”
6. Thermostat satisfied.
7. Gas valve closes, burner extinguished.
8. Blower post purge for 30 seconds.
9

10
Sequence of Operation
Lockout Conditions
The system will go into lock out mode for the following reasons:
1. ERROR CODE 110
a. Control board will go into “Soft Lockout” if the main burner cannot be lit or fails to prove flame after 3
ignition trials. The water heater display indicates a lockout condition by showing an error code number
110 with “Service Needed” in the control display window. Refer to error codes in the diagnostic section of
this Service Manual. In a “Soft Lockout” condition, the control will wait for 15 minutes and then make 3
more attempts to light the main burners. Soft lockout reset is accomplished by depressing the lower right
button under “Reset” for 3 seconds.
2. ERROR CODE 80
a. If the top of the tank should exceed 207°F, then the high limit control will shut off the burner and the water
heater will go into a “Hard Lockout.” Error code 80 will be shown in the water heater display. The control
can only be reset in the “Service Mode,” which is detailed in the “Troubleshooting” section of this Service
Manual.
3. ERROR CODE 67
a. If the vent safety switch located on the draft hood should open, the gas valve will close, the blower will
post-purge and error code 67 will appear on the display. The lockout condition will reset once the
problem is corrected and the switch reset. Refer to “Vent Safety Switch Testing and Replacement” in this
Service Manual.
CONNECTION/WIRING DIAGRAM
10

11
120 volt potential exposure. Use caution making voltage checks
to avoid personal injury.
WARNING
Use caution not to damage connectors when making voltage
measurements or jumping terminals
CAUTION
Troubleshooting
System Observation for Models with Direct Spark Ignition
Water Heater Fault: Water heater does not operate
Display Error Code: Water heater display does not
operate - blank display
Check main power supply to water heater –
fuse, circuit breaker, plug receptacle, line cord or
wiring to water heater.
Check to make sure switch on front of control
panel is in the ON position.
Verif
yp
rimar
y
volta
g
e at the transformer.
Refer to control board illustration.
Voltage at transformer across black and
white wires should be 110-120 VAC.
Check line cord with volt meter. Replace
line cord if defective.
Verif
y
secondar
y
volta
g
e at the control board.
Refer to control board illustration.
Voltage at connector location J8 across
blue and yellow wires should be 24VAC.
If not, check transformer. Replace
transformer if defective.
Does water heater display
operate? Increase thermostat
setting if tank is warm.
Is 24VAC present between
RED and BLACK wire pin
connections on the back of
control display?
Display operates-See next page. Display operates-See next page.
Replace control board.
Check wire
harness for proper
continuity.
Check wires for proper
termination to control display.
Are wire terminations connected
properly to control display?
Replace
control
board.
Make proper wire
terminations.
Y
Y
Y
Y
N
N
NN
Yellow &
Blue
wires.
Black &
White
wires.
11

12
Troubleshooting
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
WARNING
Use caution not to damage connectors when
making voltage measurements or jumping terminals
CAUTION
From previous page.
Does combustion
blower operate?
Error code #67 on display. Measure voltage
between black and white wires, of the 3 wire
harness, at the blower (make sure the
control display shows “heating” in the status
mode, if not increase the setpoint). Is there
110-120 VAC?
Replace power cord/blower harness if
display shows “heating” and no voltage
is present to the blower.
Check that the 5 wire blower
modulation harness is plugged
in to the blower
Plug in the wire harness. (Note: If
this harness is unplugged blower
will run constantl
y
.
)
Can sparking be
seen/heard at the spark
rod to the burner?
Remove high voltage wire connected at
the spark rod and hold approximately ¼”
from metal ground with insulated pliers
during the ignition cycle (3 second spark
trial period). Is there spark to ground?
Check resistance of high voltage
cable. Resistance should be 0-1
ohms. If resistance is high, replace
spark cable. If spark cable is good,
replace control board.
Check continuity of spark rod and spark
rod gap to burner. (see section “Spark
Rod Gap Adjustment.”
Does main burner light?
Error code #110 on display.
See main burner lights, no
flame signal in section
“Combustion System Testing
and Replacement.”
(See “Combustion System
Testing and Replacement”).
Does burner continue until
thermostat set point is
reached? See setting
display in Service Mode
and displaying
temperature sensors.
Does blower post-purge for
30 seconds?
System okay
Check to see if control display shows any other error codes
(pressure switch, vent safety switch, or high limit). If so, refer to
the appropriate section for testing and replacement.
Replace
Blower
Replace
Control
Module
Measure voltage
between yellow and
green wires. Is there
17-30 VDC?
NN
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
12

13
Troubleshooting
Step 1: Press and hold the lower right button under “Next” in the lower right display for at least 3 seconds.
Step 2: The display will show the flame sense current in microamps when the burner is operating.
Step 3: Press the lower right “Next” button and the display will show flash and show the number of any Alert codes.
These are not currently used.
WARNING
The following procedure is for service and installation personnel only. Resetting lockout conditions
without correcting the malfunction can result in a hazardous condition.
13

14
Troubleshooting
Step 4: Press lower right “Next” button and the display will flash and show the number of any Lockout codes.
Step 5: Press lower right “Next” button and the display will show the temperature sensor reading.
Step 6: End of screens in Diagnostic Mode. Press “Done” button on lower left to exit Diagnostic Mode back to DHW
setpoint in the User Mode.
NOTICE
The screens will stay in the Diagnostic Mode for 12.5 minutes after the last button press for viewing
unless “Done” button is pressed to exit Diagnostic Mode.
14

15
Troubleshooting
DIAGNOSTIC ERROR CODES AND TROUBLESHOOTING PROCEDURES FOR EF100T399 MODELS WITH
HONEYWELL LOW FIRE START CONTROL SYSTEM
Error Code Definition of Code Cause of Problem and Actions Taken to Correct
No code –
blank display
xCheck power supply to the water heater.
xMake sure water heater is plugged in and the breaker is on.
xCheck if there is 120 volts power supply to the LINE connections on the
control board.
xIf 120 volts is present, check for 24 volts output to SECONDARY
terminals on the Control Board.
xCheck for loose wires, defective transformer.
xCheck wire harness connections from display to the control board.
3-48, 58-60 Internal Faults
xVerify wiring to the control board with wiring diagram.
xCheck power supply to make sure voltage and frequency is correct.
xCheck for 24 volts from the transformer to the control board.
xReset module by interrupting power or pressing the reset button on the
module.
49 Voltage too low or high
xMeasure the incoming line voltage.
xVoltage should be 115-125 volts.
xIf the voltage is not within this range or there is drastic fluctuation, then
have the incoming power supply checked.
xIf the line voltage is satisfactory, check the output from the transformer
to make sure it is 22-26 volts.
xReplace transformer or wiring if defective.
53 AC Inputs phase
reversed
xCheck the module and display connections.
xCheck the module power supply and make sure that frequency, voltage
and VA capacity of the transformer meet specifications.
xCheck to make sure the wiring connections on the control module from
terminals J4-10 and J8-2 are connected together.
62 Fan speed not proved
xCheck the blower modulation wire harness connection from the blower
to the control module at J2 connection.
xMake sure the pin terminals make solid contact.
xMeasure the resistance of each wire in the wire harness from the
terminal ends.
xReplace wire harness if defective.
xCheck if there is 17-30 volts DC between the yellow and green wires on
the blower 5 wire harness.
xCheck if there is 17-30 VDC between the yellow and green wires on the
blower 5 wire harness.
67 ILK Off (Interlock Off)
xCheck wiring to the normally closed blocked vent safety.
xUse a voltmeter to find out if the blocked vent safety switch has
opened.
xIf so, determine the cause (blocked vent terminal, recirculation).
xIf limit switch is closed, check wiring for shorts.
xMeasure continuity.
xIf limit switch and wiring check O.K., replace control module.
Troubleshooting
15

16
Service Procedure I:
80 High Limit (Overheat
Condition)
x Check the wiring from the sensor to the control module.
x Measure the resistance of each outside wire to the center wire.
x If either outside wire has a much different resistance reading, replace
the sensor.
x Make sure the sensor is securely held inside the well with the clip.
x If the problem persists and the sensor and wiring check O.K., then
replace the control module.
93 DHW/TEMP
Sensor Fault
x Check the sensor wire harness from the sensor to the control module.
x Make sure there are no loose connections to the control plug.
x Check the resistance reading from each of the outside wires to the
center (common) wire.
x If the ohm readings are not fairly close, replace the sensor.
x Replace the control module if the problem persists and the sensor and
wire connections are not defective.
105 Flame detected out of
sequence
x Check to see if flame is present inside the combustion chamber before
or after the ignition cycle.
x If so, check to make sure the gas valve is wired correctly.
x Check for voltage at the gas valve connection.
x Replace the gas valve if defective.
x If no flame is visible outside of the ignition sequence/run cycle, then
make sure the flame sensor is wired to the correct terminal.
x Make sure the ignition cable is not crossing the flame sensor wire or
ignition ground wires.
x If problem persists and all other checks have been verified, replace the
control module.
110 Ignition Failure
Occurred
x Burner failed to light or stay lit after 3 retries.
x Hold condition – will reattempt ignition after 15 minute waiting period.
x Check gas valve wiring and gas valve operation during the ignition
cycle.
x If burner lights but quickly goes out, check the flame sensor wire or the
flame sensor.
x If the flame sensor rod is badly corroded with deposits, clean with
sandpaper or replace.
x Check the inlet gas supply to make sure the pressure is sufficient and
does not drop after the gas valve opens.
x Make sure the combustion blower is operating during the ignition and
run cycle.
x Check the venting system to make sure the inlet and exhaust terminals
and venting system is not blocked.
122 Light-off Rate Proving
Failed
x If blower speed is not verified from the PWM (Pulse Width Modulation)
signal within 5 minutes, the previously described error code “62”
changes from a hold condition to this lockout code condition.
x Check the harness and pin terminals for a good connection to the
control module.
x Replace the control module if the wire harness is good.
137 ILK Open
(Interlock Open)
x Check if blocked vent safety switch is open.
x If switch checks O.K., replace control module
16

17
Thermostat Circuit Testing and Replacement

IMPORTANT NOTE: This procedure assumes a cool tank.
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
WARNING
Use caution not to damage connectors when
making voltage measurements or jumping
terminals
CAUTION
Condition: Water heater not operating.
Display shows error code “93” (sensor
reading faulty)
N
Unplug or disconnect electrical power to the water heater.
Check continuity of wire harness to sensor. Resistance of
harness should be close to 0 ohms. Replace wire harness
if high resistance is measured (over .5 ohms). Check
wires for intermittent connections, shorts, frayed
insulation. Replace if necessary.
If wire harness is O.K., check sensor resistance detailed
in “Appendix – A: sensor resistance at various
temperatures” at the end of the thermostat testing and
re
p
lacement section. Re
p
lace sensor if needed.
Turn power ON to water heater. Run water heater through
heating cycle and verify proper operation. Sensor
temperature can be viewed when burner shuts off (see
section on viewin
g
the dis
p
la
y
in “Service Mode”
)
.
Condition: Water heater not operating. Display
shows error code “80” high water temperature
(
over 200 °F
)
.
WARNING
Do not reset the display from the hard lockout
state without correcting the cause of the
overheatin
g
condition.
Turn power OFF. Draw water to cool tank below 120 °F
Check sensor. Sensor is held in place with a clip fastened
to the well (see photo). Check sensor wire for potential
damage or breaks in the wire insulation. Is the sensor fully
inserted into the well?
If sensor clip is damaged replace
clip. Replace sensor if damaged.
Check sensor resistance (see Sensor
Resistance Testing, following section).
Continued on
next page.
Y
Checking
continuity of
sensor
(disconnected
from control board.
Sensor shown fully
inserted into well
Sensor clip shown
properly installed
17

18
Service Procedure I:
Thermostat Circuit Testing and Replacement
Do not operate water heater without verifying
that the overheating condition has been
corrected.
WARNING
Condition: Water heater not operating. Display
shows error code “80” high water temperature
(over 200 °F) (continued from previous page).
Once cause of overheating condition has been diagnosed
and corrected, the control may be reset.
x Reconnect and switch on power to the water heater.
x Press button under “Reset” and hold for 3 seconds.
x Set thermostat to the desired setting.
x Water heater will start.
x Monitor temperatures for one complete heating cycle making sure
the maximum tank tem
p
erature remains below 200 °F.
18

19
Service Procedure I:
Thermostat Circuit Testing and Replacement
APPENDIX-A
Sensor Resistance at Various Temperatures
Be careful when making voltage measurements or jumping terminals not to damage or deform connectors or
connector pins.
Draw water from the T&P valve. Compare temperature with temperature ohms chart below.
Example: If the temperature is 84°F, then the resistance through the sensor would be 8449 (see shaded area).
Note: Sensor resistance increases as the temperature falls.
In Degrees F
°F 0 1 2 3 4 5 6 7 8 9
40 26109 25400 24712 24045 23399 22771 22163 21573 21000 20445
50 19906 19383 18876 18383 17905 17440 16990 16553 16128 15715
60 15314 14925 14548 14180 13823 13477 13140 12812 12494 12185
70 11884 11592 11308 11032 10763 10502 10248 10000 9760 9526
80 9299 9078 8862 8653 8449 8250 8057 7869 7685 7507
90 7333 7165 7000 6839 6683 6531 6383 6238 6098 5961
100 5827 5697 5570 5446 5326 5208 5094 4982 4873 4767
110 4663 4562 4464 4368 4274 4183 4094 4006 3922 3839
120 3758 3679 3602 3527 3453 3382 3312 3244 3177 3112
130 3048 2986 2925 2866 2808 2752 2697 2643 2590 2538
140 2488 2439 2391 2344 2298 2253 2209 2166 2124 2083
150 2043 2004 1966 1928 1891 1856 1820 1786 1753 1720
160 1688 1656 1625 1595 1566 1537 1509 1481 1454 1427
170 1402 1376 1351 1327 1303 1280 1257 1235 1213 1191
180 1170 1150 1129 1110 1090 1071 1053 1035 1017 999
190 982 965 949 933 917 901 886 871 857 842
200 828 814 801 788 775 762 749 737 725 713
In Degrees C
°C 0 1 2 3 4 5 6 7 8 9
0 32648 31026 29495 28049 26682 25389 24166 23010 21915 20879
10 19898 18968 18088 17253 16461 15710 14998 14322 13680 13071
20 12492 11942 11419 10922 10450 10000 9572 9165 8778 8409
30 8057 7722 7403 7099 6808 8532 6268 6016 5775 5546
40 5327 5117 4917 4726 4543 4368 4201 4042 3889 3742
50 3602 3468 3340 3217 3099 2986 2878 2774 2675 2579
60 2488 2400 2316 2235 2157 2083 2011 1942 1876 1813
70 1752 1693 1637 1582 1530 1480 1432 1385 1340 1297
80 1256 1216 1177 1140 1105 1070 1037 1005 974 944
90 916 888 861 835 810 786 763 741 719 698
19

20
120 volt potential exposure. Isolate the
appliance and reconfirm power is disconnected
using a multi-meter.
WARNING
Service Procedure I:
Thermostat Circuit Testing and Replacement
ThermostatSensor(Thermister)ReplacementProcedure
Step 1. Position main power switch to “OFF”
Step 2. Disconnect (unplug) water heater from 120 volt power
source.
Step 3. Un-latch and remove top surround cover from top of
heater.
Step 4. Disconnect temperature sensor from control (see photos below).
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Step 5. Unclip sensor from well and pull sensor to remove, do not remove well (see picture).
Step 6. Install new sensor assembly into well and reinstall senor clip.
Step 7. Reconnect the sensor connector to the control board and route the wire harness
through the same path that it was removed.
Step 8. Restore 120 volt power supply and water supply to water heater, check and repair any leaks found. Confirm
proper operation following the lighting instructions on the lighting instruction label or the lighting instruction
located in the installation and operating instruction manual.
Step 9. Replace surround cover on top of heater.
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Sensor clip sown
properly installed
Sensor shown fully inserted
into well
Disconnect sensor
harness from
control board
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