Bradford White UCG100H399 User manual

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Manual 238-51306-00A REV 12/14
SERVICE
MANUAL
Troubleshooting Guide
and Instructions for Service
(To be performed ONLY by
qualified service providers)
Effective: December, 2014
ECO 7956
Models Covered
by This Manual:
UCG100H399*N
(*) 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
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SAVE THISMANUAL FOR FUTURE REFERENCE REV 12/14 238-51306-00A
Introduction
The Bradford White Ultra Low NOx Atmospheric Vent Water Heater is designed to deliver a
remarkableamount of hot water at 82% thermal efficiency in aquiet running unit with atop exhaust
vent connection that allows for installation in existing locations. Whilethis unit is vented
atmosphericallythere is no damper required to maintain heat loss during off cycle. Several
technologicallyadvanced 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 professionalson 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 aturbulent flame down into the water
backed combustion chamber. This turbulence causes athorough mixing of gas and air for optimum
combustion. The combustion gases then travel through atwo pass flue system keeping the gases
moving at ahigh 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 modulemonitors 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 modulecontains 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 helpin determining the cause of system lockouts.
The contents in this manual are detailed informational toolsto assist in the proper diagnosis of the
Ultra Low NOx Atmospheric Vent Water Heater operational faults. Please read this service manual
completelyand record as much information regarding the Ultra Low NOx Atmospheric Vent Water
Heater operation and installation specifics related to any concerns.
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How to Use ThisManual
Itis 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 greatlyto 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. Shouldyou need to call for technical support, please provide the information
shown on this form to the support technician to helpensure 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 aseries of test procedures to determine root cause of failure.
Component replacement procedures directlyfollow the test procedures for agiven component.
Insome difficultto diagnose conditions, it may be necessary to isolate the heater from the vent
system to determine root cause.
Contact Technical support immediatelyif diagnosis is not determined using the methods described in
this service manual.
ToolsRequired for Service
Manometer: Two types available, aliquid “U” tube type or adigital (magna-helic) type. This device is
used to measure gas and/or air pressures and vacuum.
Multi-Meter: Adigital type is stronglyrecommended. 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 supplypressure. Also used to determine tank
pressure by adapting to the drain valve of the heater.
Jumper Leads: Alength 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 #2tip, ¼" nut driver, pliers (common & needlenose), socket set including a1-1/16 deep
well socket, wire cutters, wire strippers, wire crimpers, torpedo level, small shop vac, step ladder, and
flashlight.
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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.
xSinglecontrol board with plug in wiring controlstemperature, 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 - Ahigh 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.
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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 ¼810 52 ½ 55 ½ 69 ¾ 63 ¼30 28 ¼63 ¼1½ ¾ 1657
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 117.2371 1962 203 254 1334 1410 1772 1607 762 718 1607 38 19 25 297
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Specifications
Power SupplyDedicated 120 VAC, 60Hz, 15A GFI
Gas SupplyMinimum 1” Nat
(Schedule40black 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
AtmosphericallyVented, Type BVenting 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 voltfrom transformer. Controlstank
temperature, ignition functions, combustion blower. See
ignition timings in sequence of operation for Integrated
Control.
Transformer 120 VAC primary, 24 VAC secondary, 40VA.
Spark Rod Igniter 0.22” nominal gap to the burner surface.
Flame Sensor Output Minimum 1micro amp. Typical range 5to 30 micro
amps.
Gas Valve Negative regulation, 24 VAC, ½” PSI max., 4.5” W.C.
minimum running inlet.
Vent Safety Switch Normallyclosed, opens @ 240°F, manual reset.
Blower 120 VAC, 60 Hz, 1.5-3.5amps, 8000 RPM
Combustion LevelsCO2:8-11%, CO: less than 0.04% (400 PPM) air free

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Specifications
Vent Tables
(Intake Only)
Model Number Max Intake Vent Length (feet) 3" Max Intake Vent Length (feet) 4"
UCG100H399 2550
WARNING!The UCG100H399 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 NOTuse 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 5feet of venting for every 90° elbow.
3. Add 2 ½feet of venting for every 45° elbow.
4. Total vent length cannot exceed “Max Intake Vent Length” on the venting tableshown above.
Exampleof Total Intake Vent Length for UCG100H399 installation:
A3” venting system has atotal of two 90-degree elbows and atotal straight pipe length of 10 feet.
Equivalent vent length for elbows: 2 x5feet = 10 feet.
Total equivalent vent distance = 10 feet + 10 feet = 20 feet total equivalent vent length. Thisisbelow
the maximum allowed distance of 25 feet for thismodel using 3” vent.
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Sequence of Operation
1. Thermostat callsfor heat.
2. Combustion blower starts.
3. Blower pre-purge period of 30 seconds.
4. Trial for Ignition. (5 seconds, 3trials).
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 aminimum of 1.0microamp through flame sense
rod to prove flame.
c. Ifthe blocked vent safety switch contacts (normallyclosed) 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. Ifthe normallyclosed blocked vent safety switch opens, the gas valve closes, the blower continues to
operate indefinitelyand error code 67 will be displayed after acoupleminutes (up to 5minutes) with
“Service Needed.”
6. Thermostat satisfied.
7. Gas valve closes, burner extinguished.
8. Blower post purge for 30 seconds.
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Sequence of Operation
LockoutConditions
The system will go into lock out mode for the following reasons:
1. ERROR CODE110
a. Control board will go into “Soft Lockout”if the main burner cannot be lit or failsto prove flame after 3
ignition trials. The water heater display indicates alockout 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. Ina“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 3seconds.
2. ERROR CODE80
a. Ifthe top of the tank shouldexceed 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 onlybe reset in the “Service Mode,”which is detailed in the “Troubleshooting”section of this Service
Manual.
3. ERROR CODE67
a. Ifthe vent safety switch located on the draft hood shouldopen, 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
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