A.O. Smith Cyclone XL 100 Series How to use

SERVICING SHOULD ONLY BE PERFORMED BY A QUALIFIED SERVICE TECHNICIAN
PRINTED 0220 100314732 2000568400 Rev. A
Service Handbook
COMMERCIAL GAS WATER HEATERSCOMMERCIAL GAS WATER HEATERS
MODELS
BTHS 750A & 1000A
SERIES 100 & 101
INSTALLATION - OPERATION
- SERVICE - MAINTENANCE

2
CONTENTSCONTENTS
INTRODUCTION...................................................................... 3
Qualications........................................................................ 3
Service Warning................................................................... 3
Service Reminder................................................................. 3
Tools Recommended ........................................................... 3
INSTALLATION CONSIDERATIONS ....................................... 4
Instruction Manual................................................................ 4
Closed Water Systems......................................................... 4
Thermal Expansion .............................................................. 4
Air Requirements ................................................................. 4
Contaminated Air.................................................................. 4
FEATURES AND COMPONENTS ........................................... 5
Top View............................................................................... 8
SEQUENCE OF OPERATION FLOW CHART......................... 9
FAULT AND ALERT CODES .................................................. 10
1. Low Gas Pressure.......................................................... 10
2. Ignition Failure................................................................ 12
3. Blocked Air Intake .......................................................... 14
4. Blocked Exhaust ............................................................ 15
5. Flame Sensor Error........................................................ 15
6. No Water ........................................................................ 17
7. Anode Shorted ............................................................... 18
8. Temperature Probe Short............................................... 18
9. Temperature Probe Open............................................... 20
10. Flue Gas Temperature Probe Short/Open ................... 21
11. Flue Gas Temperature High Limit................................. 21
12. Flow Not Detected........................................................ 21
13. Flow Switch Stuck Closed............................................ 22
VENTING................................................................................ 24
General Venting Information .............................................. 24
INTAKE AIR CONNECTION................................................... 25
ELECTRICAL CONNECTIONS – ALL MODELS.................... 26
Power Fluctuations and Electrical Noise ........................... 26
Dedicated Power Wiring and Breakers .............................. 26
Electrical Wiring ................................................................. 26
Power Supply Connections ................................................ 26
Enable/ Disable Switch ...................................................... 27
Power Supply Test ............................................................. 27
INSTALLATION CHECK LIST ................................................ 28
OPERATION AND SERVICE ................................................. 29
How It Works...................................................................... 29
Combustion Blower ............................................................ 29
Modulation.......................................................................... 29
BLOWER SPEED CONTROL ................................................ 30
BURNER ASSEMBLY ............................................................ 30
COMBUSTION BLOWER AND BURNER REMOVAL/
INSTALLATION ..................................................................... 31
Combustion Blower/ Burner Removal ................................ 31
Combustion Blower/ Burner Installation ............................. 31
SPARK IGNITER .................................................................... 32
CCB (CENTRAL CONTROL BOARD).................................... 33
CCB Cover Removal And Replacement ............................ 34
CCB Circuit Board Layout .................................................. 35
CCB Connection Identication ........................................... 36
CPAM – Commercial Power Anode Module ...................... 38
WIRING DIAGRAM ................................................................ 39
CONTROL OVERVIEW.......................................................... 40
ICOMM Remote Monitoring System .................................. 40

3
INTRODUCTIONINTRODUCTION
This Service Handbook covers the water heater model and series numbers listed on the front cover only. The instructions and
illustrations contained in this service handbook will provide you with troubleshooting procedures to verify proper operation and diagnose
and repair common service problems.
QUALIFICATIONS
QUALIFIED INSTALLER OR SERVICE AGENCY
Installation and service of this water heater requires ability equivalent to that of a Qualied Agency (as dened by ANSI below) in the
eld involved. Installation skills such as plumbing, air supply, venting, gas supply and electrical supply are required in addition to
electrical testing skills when performing service.
ANSI Z223.1: “Qualied Agency” - “Any individual, rm, corporation or company that either in person or through a representative is
engaged in and is responsible for (a) the installation, testing or replacement of gas piping or (b) the connection, installation, testing,
repair or servicing of appliances and equipment; that is experienced in such work; that is familiar with all precautions required; and that
has complied with all the requirements of the authority having jurisdiction.”
SERVICE WARNING
If you are not qualied (as dened by ANSI above) and licensed or certied as required by the authority having jurisdiction to perform a
given task do not attempt to perform any of the procedures described in this service handbook. If you do not understand the instructions
given in this service handbook do not attempt to perform any procedures outlined in this service handbook.
SERVICE REMINDER
When performing any troubleshooting step outlined in this service handbook always consider the wiring and connectors between
components. Perform a close visual inspection of all wiring and connectors to and from a given component before replacement. Ensure
wires were stripped before being crimped in a wire connector, ensure wires are crimped tightly in their connectors, ensure connection
pins in sockets and plugs are not damaged or worn, ensure plugs and sockets are mating properly and providing good contact.
Failure to perform this critical step or failing to perform this step thoroughly often results in needless down time, unnecessary parts
replacement, and customer dissatisfaction.
TOOLS RECOMMENDED
• Instruction Manual that came with the water heater.
• All tools common to installation and service of commercial water heaters such as hand tools, screwdrivers, pipe wrenches etc.
• Long (8-10”) T handle 1/8 inch hex (Allen key) wrench for Combustion Blower removal and installation.
• Hex (Allen) wrench sizes: 5/32”, 1/8”, 1/4” and 5/16” - for Burner, and 24 Volt Gas Control Valve removal and installation.
• Digital manometer: Range -20.00 to +20.00” W.C. Resolution - 0.01” W.C. Required to test pressure switch performance and supply
gas pressure.
• Digital Multi Meter; capable of measuring:
• AC/DC Voltage.
• Ohms.
• DC micro amps (μA) - ame sensing current, see Flame Sensing Current Test (page 16).

4
INSTALLATION CONSIDERATIONSINSTALLATION CONSIDERATIONS
This section of the Service Handbook covers some of the critical installation requirements that, when overlooked, often result in
operational problems, down time and needless parts replacement. Costs to correct installation errors are not covered under the limited
warranty. Ensure all installation requirements and instructions contained in the Instruction Manual that came with the water heater have
been followed prior to performing any service procedures.
INSTRUCTION MANUAL
Have a copy of the Instruction Manual that came with the water heater on hand for the model and series number being serviced.
Installation information given in this Service Handbook is not a complete installation instruction. Installation information given in this
Service Handbook has a limited focus as it applies to servicing the water heater. This Service Handbook does not replace or supersede
the Instruction Manual that came with the water heater. Always refer to the Instruction Manual for complete installation instructions. If
the Instruction Manual is not on hand, copies can be obtained from the manufacturers web site or by calling the technical support phone
number shown on the back cover of this Service Handbook.
CLOSED WATER SYSTEMS
Water supply systems may, because of code requirements or such conditions as high line pressure, among others, have installed
devices such as pressure reducing valves, check valves, and back ow preventers. Devices such as these cause the water system to
be a closed system.
THERMAL EXPANSION
As water is heated, it expands (thermal expansion). In a closed system the volume of water will grow when it is heated. As the volume
of water grows there will be a corresponding increase in water pressure due to thermal expansion. Thermal expansion can cause
premature tank failure (leakage). This type of failure is not covered under the limited warranty. Thermal expansion can also cause
intermittent Temperature-Pressure Relief Valve operation: water discharged from the valve due to excessive pressure build up. This
condition is not covered under the limited warranty. The Temperature-Pressure Relief Valve is not intended for the constant relief of
thermal expansion.
A properly sized and pressurized thermal expansion tank must be installed on all closed systems to control the harmful effects of
thermal expansion. Contact a local plumbing service agency to have a thermal expansion tank installed.
AIR REQUIREMENTS
Carefully review the requirements for combustion and ventilation air in the Instruction Manual that came with the water heater. Failure to
meet these requirements when the water heater is installed or overlooking their importance when servicing the water heater often
results in needless down time, unnecessary parts replacement, and customer dissatisfaction.
An inadequate supply of air for combustion and ventilation often causes operational problems. A lack of combustion and ventilation air
can create a negative ambient air pressure in the installed space which can lead to improper combustion and operational problems with
pressure switches.
CONTAMINATED AIR
Combustion air that is contaminated can greatly diminish the life span of the water heater and water heater components such as
Igniters and Burners. Propellants of aerosol sprays, beauty shop supplies, water softener chemicals and chemicals used in dry cleaning
processes that are present in the combustion, ventilation or ambient air can cause such damage.
Vapors from volatile compounds such as solvents, cleaners, chlorine based chemicals and refrigerants in addition to being highly
ammable in many cases, can also react to form highly corrosive substances such as acids inside the combustion chamber. The results
can be hazardous and cause product failure.
If the water heater is installed in beauty shops, barber shops or laundries with dry cleaning equipment, it is imperative the water heater
be installed in a Direct Vent conguration so that air for combustion is derived directly from the outdoor atmosphere through a sealed
intake air pipe. See the venting installation section in the Instruction Manual that came with the water heater for more information on
Direct Vent installations.

5
FEATURES AND COMPONENTSFEATURES AND COMPONENTS
1
2
3
4
105
6
8
27
7
22
21
2019
(Behind UIM)
23
31
23
29
28
24
32
25
33
26
Figure 1.Front View
13 12 11
14
8
9
7
Figure 2.Blower Burner Assembly
18
17
6
17
30 16
15
17
4
Figure 3.(Top View (without plastic cover
Important: The Enable/Disable switch listed in this manual is NOT an “on/off” switch and does not disconnect 120 volt power to the
CCB and other heater components.
1. Water Heater’s Enable/Disable Switch. When in the “Disabled” position the switch removes electrical power from the gas valve so
that water heating is disabled. The display, CCB, and other electrical components will still be energized and the display will read
“Water Heating Disabled.”
2. UIM (user interface module). The UIM includes the display circuit board and the control system’s LCD Touch Display. Used to
adjust various user settings and view operational information.
3. Central Control Board (CCB) enclosure. This enclosure houses the control system’s main circuit board, power supply board, power
transformer, and conguration key. The CCB regulates water temperature and controls all water heater functions. See Control
System Operation (page 37).
4. 120 VAC junction box. Incoming power supply, ground connections, and other eld installed electrical connections are made here.
See Power Supply (page 13) and Power Supply Connections (page 33).
5. Blocked Intake Air switch. Normally closed contacts that open on fall in pressure. This switch is used to insure intake (combustion)
air to the water heater is not restricted. The control system monitors this switch and will disable heating operation if its contacts are
open during a heating cycle.

6
6. Temperature-Pressure Relief Valve. See Temperature-Pressure Relief Valve (page 14).
7. 1” Honeywell modulating 24 VAC gas valve.
8. 6” PVC air intake connection.
9. Honeywell Venturi Mixing Unit.
10. Combustion blower.
11. Combustion sight glass.
12. Flame Sensor: The control system also monitors the ame sensor to conrm a ame is present at the Main Burner. If a ame is not
veried during the ignition trial period (3-5 seconds) the control system will immediately de-energize the 24 VAC Gas Valve. See
Sequence of Operation Flow Chart (page 54).
13. Spark Eletrode: The control system energizes the spark ignition control with 120 VAC during the ignition period. The spark ignition
control then sends a high-voltage electrical current to the spark igniter which in turn ignites the main burner air/gas mixture.
14. Premix burner.
15. Spark Ignition Control. When energized, sends the electrical current to the spark igniter.
16. Temperature Probe: The water heater’s control system monitors this probe to measure The heater’s water temperature. The probe
also houses the ECO (energy cut out) switch. This is a non adjustable high temperature limit switch. The ECO switch contacts are
normally closed and will open on a temperature rise. See High Temperature Limit Control (ECO) (page 36).
17. Powered anode rods: The water heater’s covered in this manual are equipped with 3 powered (non sacricial) anode rods at the
top. Protective current is fed by the control system to the titanium electrodes at the end of each anode rod. This current ows
through the water to the conductive surfaces inside the storage tank which diminishes the corrosive effect of water when it comes
in contact with steel.
18. Blocked Intake Air switch. Normally closed contacts that open on fall in pressure. This switch is used to insure intake (combustion)
air to the water heater is not restricted. The control system monitors this switch and will disable heating operation if its contacts are
open during a heating cycle.
19. Blocked Exhaust (vent) switch. Normally closed contacts that open on a rise in pressure. This switch is used to insure the Exhaust
(vent) piping connected to the water heater is not restricted. The control system monitors this switch and will disable heating operation
if its contacts are open during a heating cycle.
20. CPAM (Commercial powered anode module ).
21. Power supplier for CPAM.
22. 75VA transformer.
23. Side-mounted powered anodes.
24. Heater’s internal recirculation pump.
25. Flow switch, vertically mounted, used for conrmation of water owing through the secondary heat exchanger during the heater’s
running.
26. Flue temperature sensor.
27. 2” NPT Gas supply connection.
28. Water heater drain valve.
29. 2”NPT cold water inlet connection
30. 2” NPT hot water outlet connection.
31. 1” NPT building recirculation return connection.
32. ½” NPT condensate drain connection.
33. Cleanout access panel, covers water heater cleanout opening and ASME plate.

7
8
1
4
2
3
7
5
9
11
10
6
Figure 4. Combustion Blower & Burner Assembly
34. Heat shield & insulation
35. Burner ange gasket
36. Observation sight glass
37. Burner
38. Flame rod
39. Flame rod gasket
40. Blower discharge gasket
41. Burner gasket
42. Spark rod
43. Spark rod gasket
44. Ignition cable
4 3 2
1
Figure 5. Burner Blower Assembly
1. Gas Valve
2. Air Intake Adapter
3. Venturi
4. Blower

8
TOP VIEW
2
3
4
3
56
7
3
8
9
1
Figure 6. Top View
1. Burner/Blower Assembly
2. Blocked Intake Air switch
3. Powered anode rods
4. Temperature-Pressure Relief Valve
5. 2” NPT hot water outlet connection
6. Temperature Probe
7. Spark Ignition Control
8. 120 VAC junction box
9. Exhaust/Condensate Elbow

9
SEQUENCE OF OPERATION FLOW CHARTSEQUENCE OF OPERATION FLOW CHART
YES NO
120 V Recirculator
is energized 24 Volt Gas Valve
de-energized
Inter-Purge cycle
24 Volt Gas Valve
de-energized
Retries up to
two more times
Post-Purge cycle
Control System
Locks Out
“Ignition Failure”
Fault Msg is
displayed
Water heater goes
into standby mode
If tank temperature drops below Operating Set Point minus
Differential setting a heating cycle is activated
Spark Ignition Transformer is energized
24 Volt Gas Valve is energized
gas flows to Main Burner
Is flame sensed at the Main Burner?
(control system monitors the flame sensor)
Control System Locks Out
Displays Fault Msg
NO
Combustion Blower is energized
Pre-Purge cycle
Sequence is shown with Enable/Disable Switch in the Enable position
Control System performs diagnostic checks.
Normal state of all pressure switches, the flow switch, and
the ECO are checked.
Pressure Switches and the ECO are verified closed.
Water is heated to
set point
120 V Recirculator is
de-energized after
5-second delay
Figure 7. Sequence of Operation Flow Chart

10
FAULT AND ALERT CODESFAULT AND ALERT CODES
1. LOW GAS PRESSURE
The minimum gas supply pressure is measured while gas is owing (dynamic pressure) along with all additional gas appliances
operating on the same gas supply system. Cyclone XL water heater can operate smoothly when gas supply pressure is as low as 3.5”
WC dynamic for natural gas and 8.0” WC dynamic for LP models. There is no low gas pressure switch installed to the heater. If the gas
supply pressure is below the minimal as indicated on the heater rating plate, issues such as ignition failure, rough ignition and so on
may arise.
CHECK/ REPAIR:
• Determine proper minimum pressure from rating plate.
• Use manometer or gauge to check gas pressure during all stages of operation with all other appliances ring.
• If pressure falls below rating plate requirement, supply pipe may be too small for application or supply regulator may be operating
improperly. See Gas Pressure section below.
HIGH ALTITUDE
The water heaters covered in this Service Handbook are certied for elevations up to 10,100 feet (3,078 meters). For higher elevations
call the toll free support phone number shown on the back cover of this Service Handbook for technical assistance.
GAS SUPPLY SYSTEMS
Low pressure building gas supply systems are dened as those systems that cannot under any circumstances exceed 14” W.C. (1/2
PSI Gauge). These systems do not require additional pressure regulation. Measurements should be taken to insure that gas pressures
are stable and fall within the requirements stated on the water heater rating plate. Readings should be taken with all gas burning
equipment off (static pressure) and with all gas burning equipment running at maximum rate (dynamic pressure). The gas pressure
supplied to this unit must be below the maximum and above the minimum pressures listed on the unit’s rating plate and must not drop
more than 1.5” W.C. when unit is operating at the high re rate along with all additional gas appliances operating on the same gas
supply system. Pressure drops that exceed 1.5” W.C. may cause rough starting, noisy combustion or nuisance outages. Increases or
spikes in static pressure during off cycles may cause failure to ignite or in severe cases damage to appliance Gas Control Valves. If
your low pressure system does NOT meet these requirements, do not operate this unit. The installer is responsible for ensuring that the
gas supply pressures meet the requirements described above and listed in the table. Failure of the gas supply to meet these
requirements is not covered under the warranty.
High Pressure building supply systems use pressures that exceed 14” W.C. (1/2 PSI Gauge). These systems must use eld supplied
regulators to lower the gas pressure to less than 14” W.C. (1/2 PSI Gauge). Water heaters require gas regulators that are properly sized
for the water heater’s BTU input and capable of delivering the rating plate specied pressures. Gas supply systems where pressure
exceeds 5 PSI often require multiple regulators to achieve desired pressures. Systems in excess of 5 PSI building pressure should be
designed by gas delivery professionals for best performance. Water heaters connected to gas supply systems that exceed 14” W.C.
(1/2 PSI Gauge) must be equipped with a gas supply regulator capable of preventing the gas supplied to the unit from exceeding 14”
W.C. under any upstream supply pressure or condition.
SUPPLY GAS REGULATOR
The maximum allowable gas supply pressure for the water heaters covered in this Service Handbook is 14.0 inches W.C. (3.49 kPa)
static for natural and propane gas. Install a positive lock-up gas pressure regulator in the gas supply line if inlet gas pressure can
exceed these pressures at any time. Regulators must be sized to equal or exceed the BTU input requirements of the heater model and
installed, used, and maintained according to manufacturer’s specications.
If a positive lock-up regulator is installed follow these instructions:
1. Positive lock-up gas pressure regulators must be rated at or above the input Btu/hr rating of all the gas appliances that are on the same
system as the water heater.
2. Supply gas regulators shall have inlet and outlet connections not less than the minimum supply gas line size for the water heater they
supply.
3. Refer to the gas pressure regulator’s manufacturers installation instructions to determine its installation location requirements.
4. After installing the positive lock-up gas pressure regulator(s) an initial nominal supply pressure setting of 7.0” W.C. (1.74 kPA) for
Natural Gas and 11.0” W.C. (2.74 kPA) for Propane (LP) while the water heater is operating is recommended and will generally provide
good water heater operation. Adjustments to the regulator maybe required to maintain a steady gas supply pressure.
5. When installing multiple water heaters in the same gas supply system it is recommended that individual positive lock-up gas pressure
regulators be installed at each unit from the supply gas connection on the water heater.

11
Service notes:
• The manifold gas pressure is non-adjustable as these are zero-governing gas systems.
• There is usually a drop in supply gas pressure noticed when the water heater’s 24 Volt Gas Control Valve opens during ignition. The
manifold pressure will go from a negative value (during pre-purge) to near zero when gas is owing.
• A sustained drop in supply gas pressure of 1.5” W.C. or more during ignition may indicate the supply gas line is undersized. If the
water heater is experiencing a sustained drop in supply gas pressure of 1.5” W.C. or more and the water heater is experiencing
repeated Ignition Failure fault conditions, intermittent loss of ame or rough starting ensure the supply gas line is sized in
accordance with the current edition of National Fuel Gas Code (ANSI Z223.1/NFPA 54) or the Natural Gas and Propane Installation
Code (CAN/CSA B149.1).
GAS PRESSURE TEST
1. Use the Enable/Disable Switch located on the front of the water heater and put the unit in disabled mode.
2. Turn off the supply gas to the water heater at the main gas shutoff valve serving the water heater.
3. Open the Supply Gas Pressure Test Port on the Gas Control Valve or use the pressure port on the gas valve inlet ange. See Figure 8.
4. A digital manometer (see “Tools Recommended” on Page 2) is needed to check supply gas pressure. To monitor supply gas pressure,
attach a sensing tube from Gas Control Valve Supply Gas Pressure Test Port to one digital manometer.
5. Open the main gas shutoff valve serving the water heater.
6. The manometer connected to the Supply Gas Pressure Test Port should read the “static” (gas is not owing) supply gas pressure.
2" GAS INLET
PORT #2: SUPPLY-GAS
PRESSURE TEST PORT
OFF-SET ADJUSTMENT
UNDER SCREW COVER
THROTTLE ADJUSTMENT
UINDER BLUE COVER
GAS PRESSURE
TEST PORT
Figure 8. BTHS 750-1000 Gas Control Valve Assembly
7. Record the supply gas pressure.
8. Use the Enable/Disable Switch located on the front of the water heater and put the unit in enabled mode. The settings on the water
heater may need to be changed to cause the water heater to operate.
Note: The Operating Temperature Set Point so that the unit can be returned to this setting at the conclusion of this test
procedure. Increase the Operating Set Point if necessary to cause the water heater to have a call for heat.
9. Record the supply gas pressure when the Ignition Activation operating state begins; when the animated Gas Control valve Status Icon
appears on the UIM Screen.
• The supply gas pressure will typically drop as the Gas Control Valve opens.

12
Putting The Water Heater Back In Service
1. Lower the Operating Set Point to end the heating cycle. Use the Enable/Disable Switch located on the front of the water heater and put
the unit in disabled mode.
2. Close the main gas shutoff valve serving the water heater.
3. Disconnect manometer sensing tube.
4. Close the Supply Gas Pressure Test Port on the Gas Control Valve. Turn the needle valve slotted head clockwise until tight.
5. Open the main gas shutoff valve serving the water heater and check for leaks at the Gas Control Valve test ports.
6. Use the Enable/Disable Switch located on the front of the water heater and put the unit in enabled mode. Increase the Operating Set
Point if necessary to cause the water heater to have a call for heat.
2. IGNITION FAILURE
ADVANCEDBACK
Ignition Failure
0 days 0 hrs 0 mins ago
Error Code:
B 2-70
Flame not detected. Clean flame
rod. Check gas supply.
Press the Advanced button for
more information
CAUSES:
• On an “Ignition Failure” error, either the burner is not
igniting or the burner is igniting, but the Flame Sensor is
not detecting ignition (ame).
CHECK/ REPAIR
• Determine whether or not the burner is igniting by looking through sight glass. Because the control system will shut off the Gas
Control Valve if 2-3 seconds if ignition is not detected, you must look in the sight glass at the exact moment the Gas Control Valve
icon appears on the display screen.
TESTING FOR IGNITION (FLAME):
• Set the Set Point Temperature high enough so there is a call for heat.
• Recycle the unit off and back on by turning the Enable/Disable switch to Disable for one second and then back to Enable.
• The unit will begin an ignition cycle.
• When the Gas Control Valve icon appears on display screen, immediately look through the sight glass for a brief blue ame (if you
are getting an Ignition Failure error, the ame, if the burner ignites, will only be present for 2-3 seconds).
IGNITION FAILURE FOR NEW INSTALLATIONS:
If Ignition failure happens to new installations during initial startup, check the following items rst:
1. Conrm that gas-supply line is fully purged all the way up to the gas valve.
2. Conrm that the gas-supply pressure at the gas-valve test port falls--but falls no more than 2”wc from static pressure when the gas
valve is energized (click sound can be heard when the gas valve is energized).
• If there’s no change in gas pressure reading and/or the gas valve does not become energized during the ignition, check gas valve
wiring connections and 24 Vac at the wire plug.
• If the supply pressure falls signicantly during the ignition, check the service regulator capacity and gas piping size to correct the
issue.
3. If you have conrmed Step 1 & Step 2, but NO ame is detected through the top-mounted combustion view-port, check the wiring
connections to the spark transformer and spark rod.
4. If you have conrmed Step 1 & Step 2, ame IS detected through the combustion view-port, BUT no ame icon displays on the UIM,
check ame rod and ame rod wiring connections.
5. If you have conrmed Step 1 & Step 2, the ame icon is displays on the UIM momentarily or you experience occasional ignition
failures, turn the gas valve throttle COUNTERCLOCKWISE 1/8 turn at a time.
If adjusting the gas valve resolves the ignition issue, you must use a combustion analyzer to verify the following:
a. That the combustion is clean.
b. That the CO2 reading from the combustion ue is within 8.9% - 9.3% during running.

13
BURNER IGNITES (BRIEFLY)
• If the burner ignites briey then shuts off with an “Ignition Failure” error message, follow these steps:
• Remove the connector from ame sense rod [picture of connector showing location on unit]. Inspect the connector for corrosion.
Replace if corroded or damaged. Remove Flame Sensor and clean metal end with steel wool.
• Check insulator for soot, cracks or other damage and replace if necessary.
SPARK
IGNITER
BURNER
FLAME
BURNER
(MUST
BE GROUNDED)
CERAMIC INSULATOR
FLAME SENSOR
METAL CONDUCTOR
CONTROL SYSTEM
APPLIES AC CURRENT
TO FLAME SENSOR
A
C CURRENT FLOWS FROM THE FLAME
SENSOR
TO THE BURNER. THE BURNER
MUST
BE GROUNDED FOR CURRENT TO
FLOW
. DURING THIS PROCESS THE AC
CURRENT
IS “RECTIFIED” AND BECOMES
A
DC CURRENT. DC MICRO AMP CURRENT
THEN FLOWS BETWEEN
THE FLAME SENSOR
A
ND THE BURNER.
Figure 9. Checking the Burner
• Reinsert connector on Flame Sensor and make sure the electrical connection is clean and tight.
• Recycle unit again to start another ignition cycle. If the burner ignites but the ame sense rod still fails to detect ame, contact
Commercial Technical Support.
BURNER DOES NOT IGNITE
Failure to ignite (no ame) usually means a gas supply, gas-control valve, or sparking problem. If you do not see a brief blue ame
through the sight glass during the ignition cycle (at the moment the gas control valve icon appears on the display), follow these steps:
1. Install a gas pressure gage at the gas valve’s inlet pressure port, and conrm that the gas-supply pressure DOES fall, BUT falls no
more than 2”wc from static pressure when the gas valve is energized (you will hear a click sound when the gas valve is energized):
• If there’s no change in the gas pressure reading and/or the gas valve does not energized during the ignition, check the gas valve
wiring connections and the 24 Vac at the wire plug.
• If the supply pressure falls signicantly during the ignition, check the service-regulator capacity and gas-piping size to correct the
issue.
2. If you have conrmed Step 1 & Step 2, but NO ame is detected through the top-mounted combustion view-port, check the wiring
connections to the spark transformer and spark rod.
3. If you have conrmed Step 1 & Step 2, ame IS detected through the combustion view-port, BUT no ame icon is displays on the UIM,
check ame rod and ame rod wiring connections.
4. If you have conrmed Step 1 & Step 2, the ame icon is displays on the UIM momentarily or you experience occasional ignition
failures, adjust the gas valve throttle by turning it COUNTERCLOCKWISE 1/8 turn at a time.
If the gas valve setting resolves the ignition issue, you must use a combustion analyzer to verify the following:
a. That the combustion is clean.
b. The CO2 reading from the combustion ue is within 8.9% - 9.3% during heating cycle after the throttle adjustment.

14
2" GAS INLET
PORT #2: SUPPLY-GAS
PRESSURE TEST PORT
OFF-SET ADJUSTMENT
UNDER SCREW COVER
THROTTLE ADJUSTMENT
UINDER BLUE COVER
GAS PRESSURE
TEST PORT
Figure 10. Gas Control Valve Assembly
3. BLOCKED AIR INTAKE
ADVANCED
BACK
B
locked
A
ir
I
ntake
0 days 0 hrs 0 mins ago
Error Code: A7-1201
Restriction in air intake.
Check intake pipe and
termination for blockage.
Press the Advanced button for
CAUSES:
• The Blocked Air Intake Switch has detected a possible
restriction in the air intake pipe.
CHECK/ REPAIR:
• Check pipe for restriction or excessive equivalent length.
• See Instruction Manual for pipe size, length and maximum number of elbows.
• Check actual pipe pressure with a manometer during blower operation.

15
4. BLOCKED EXHAUST
ADVANCED
BACK
B
locked
E
xhaust
0 days 0 hrs 0 mins ago
Error Code: A8-1201
Restriction in exhaust pipe.
Check exhaust pipe and
termination for blockage.
Press the Advanced button for
CAUSES:
• The Blocked Exhaust Switch has detected a possible
restriction in the exhaust pipe.
•
CHECK/ REPAIR:
• Check pipe for restriction or excessive equivalent length.
• See Instruction Manual for pipe size, length and maximum number of elbows.
• Check actual pipe pressure with a manometer during blower operation..
5. FLAME SENSOR ERROR
ADVANCEDBACK
Flame Sensor(error)
0 days 0 hrs 1 mins ago
Error Code: A9-17B
Flame Sensor rod detected flame
when gas valve should be off.
Shut off gas until repaired.
Call a service professional:
CAUSES:
• The Flame Sensor has detected ame when the Gas
Control Valve is supposed to be off.
CHECK/ REPAIR:
• Look through sight glass. If ame is present, shut the main gas supply off. See Gas Control Valve section below to conrm proper
operation.
• If ame is not present, cycle the unit Off by turning the Enable/Disable switch to Disable, wait for 5 seconds, and cycle the unit On by
turning the Enable/Disable switch to Enable to see if the error clears.
FLAME SENSOR
Ignition of the Burner is controlled electronically. The principle of operation for electronic ignition relies on ame sensing current to prove
the fuel gas owing to the Burner has been ignited.
Flame sensing requires an adequate earth ground to the water heater’s Burner. See Electrical Connections – All Models (page 26).
FLAME SENSING OPERATION
• The Flame Sensor is a metal (conductor) rod mounted in a ceramic insulator.
• The Control System applies an AC voltage to the Flame Sensor through a single wire.
• The burner ame will conduct a small amount of electrical current.
• The burner must be properly grounded for current to ow from the Flame Sensor to the Burner.
• During ignition the burner ame must make complete and continuous contact with the Flame Sensor.
• As the AC current ows from the Flame Sensor through the burner ame to the (grounded) Burner the AC current is “rectied” and
becomes a DC current.

16
• The current owing between the Flame Sensor and Burner is DC micro amp current expressed as: µA (micro Amps). Flame sensing
current can be measured with a DC micro amp test meter, see “Tools Recommended” on Page 3.
SPARK
IGNITER
BURNER
FLAME
BURNER
(MUST BE GROUNDED)
CERAMIC INSULATOR
FLAME SENSOR
METAL CONDUCTOR
CONTROL SYSTEM
APPLIES AC CURRENT
TO FLAME SENSOR
A
C CURRENT FLOWS FROM THE FLAME
SENSOR TO THE BURNER. THE BURNER
MUST BE GROUNDED FOR CURRENT TO
FLOW. DURING THIS PROCESS THE AC
CURRENT IS “RECTIFIED” AND BECOMES
A
DC CURRENT. DC MICRO AMP CURRENT
THEN FLOWS BETWEEN THE FLAME SENSOR
A
ND THE BURNER.
MINIMUM FLAME SENSING CURRENT
To prove burner ame during the Ignition Verication state the Control System monitors ame sensing current, the DC micro amp (μA)
current owing through the Flame Sensor. The Control System must sense a minimum amount of current to “prove” ame. The
minimum ame sensing current is 1.0 μA. If ame sensing current does not reach 1.0 µA during ignition or falls below this amount
during a heating cycle the Control System will immediately de-energize the 24 Volt Gas Control Valve.
After 3 failed trials for ignition the Control System will lock out and display Ignition Failure (fault condition) on the UIM. If ame sensing
current drops below 1.0 μA during a heating cycle the Control System will de-energize the 24 Volt Gas Control Valve and enter the
Inter-Purge operating state. After the Inter-Purge operating state the Control System will try for ignition again if a call for heat is still
active. See the Sequence of Operation Flow Chart (page 9).
FLAME SENSING CURRENT TEST
During the heating cycle the ame sensing current is normally greater than 8.0 μA with a clean Flame Sensor. Over time the Flame
Sensor can degrade and this will reduce ame sensing current. With heavier use, more heating cycles/greater load, this will occur more
quickly.
Measuring ame sensing current requires a test meter with a DC micro amp function, see “Tools Recommended” on Page 3. The
meter’s selector is set to DC micro amps. The two test leads from the meter are placed in series with the ame sensing circuit. This can
be done at the spade (male/female) ame sensing wiring connectors. See Figure below.
To measure ame current disable water heating by turning off the Enable/Disable Switch located in the front of the water heater and
connect the test meter following the method shown in Figure below. Enable water heating and ensure a call for heat is active - when the
Control System energizes the 24 Volt Gas Control Valve the meter will measure ame sensing current during normal operation.
Service Notes:
• The most common cause of Ignition Failure lock out is a worn Flame Sensor. The Flame Sensor should be inspected and cleaned
anytime the measured ame sensing current is below 8 µA or the Burner has been removed. Clean the Flame Sensor with ultra
ne steel wool. DO NOT use a coarse abrasive material such as sand paper. Inspect the ceramic insulator on the Flame Sensor for
cracks, replace the Flame Sensor if it is damaged.
• An open ame sensing circuit caused by disconnected or loose connectors can also cause ignition failure. Check all wiring and wiring
connections between the Flame Sensor and the J14 connector on CCB circuit board. See CCB Circuit Board Layout (page 35).
• The Burner not being grounded will cause Ignition Failure. See Electrical Connections – All Models (page 26). Ensure the water
heater and the Burner are properly grounded.

17
6. NO WATER
No Water
0 days 0 hrs 0 mins ago
Error Code: D6-8
No water detected by Powered
Anode.
The control indicates a problem
with the anode protection. By
ADVANCED
BACKACCEPT
CAUSES:
• The controller has not detected a voltage potential of
water in the tank.
• No water or low water in tank.
• Loose or open wiring connections to Power Anode(s).
• Power Anode shorted to ground at wire connection. See
Powered Anodes section shown below.
CHECK/ REPAIR:
POWERED ANODES
The water heaters covered by this Service Handbook are equipped with powered anodes. There are three top-mounted anodes and
two side-mounted anodes. See Figure 11.These anodes do not need to be replaced unless damaged. The CCB monitors the current
through the anodes and will declare a fault if there is a disconnected wire or if there is no water in the tank.
Side-Mounted
Power Anodes (2)
Top-Mounted
Power Anodes (3)
Figure 11. Powered Anode Connections
Power Anode Cleaning and Removal
1. Shut off gas, water and power supply going to the heater.
2. Relieve water pressure by either opening Temperature-pressure relief valve (T & P relief valve), if it is piped to a drain, or drain some
water off by connecting a hose to the drain valve.
Cleaning Method:
If corrosion is present on the air side of the anode, use a wire brush to clean the outer nut and brass wire terminal tab. To clean the
inner nut, remove the outer nut and the brass wire terminal tab. DO NOT REMOVE inner nut. Clean with wire brush. Reassemble and
connect blue wire to brass terminal tab.

18
7. ANODE SHORTED
Anode Shorted
0 days 0 hrs 0 mins ago
Error Code: CC-B
The Powered Anode is shorted to
earth ground or the tank.
The control indicates a problem
with the anode
ADVANCED
BACK
CAUSES:
• The controller has detected a low resistance or short to
earth ground or the tank.
CHECK/ REPAIR:
• Bent anode shorting to tank.
• Contamination (solder, loctite, water, Etc.) between anode top and surrounding metal.
• Power anode shorted to ground at wire connection. See Powered Anodes section shown under “No Water” on page 17.
8. TEMPERATURE PROBE SHORT
ADVANCEDBACK
Temp Probe (Short)
0 days 0 hrs 0 mins ago
Error Code: 45-
0
The indicated temperature Probe
may be shorted or open. Check
connector and resistance of
Probe.
CAUSES:
• The Upper or Lower Temperature Probe appears to be
shorted (very low resistance). This fault code often means
the connector has been corroded by cleaning chemicals
or other substances.
CHECK/ REPAIR:
• Make sure connector is clean and tight.
• Check probe’s resistance.
• Replace the Temperature Probe if shorted (resistance is below 390 Ohms). See Temperature Probe section below.
TEMPERATURE PROBE
This section of the Service Handbook provides information on the Temperature Probe. The Upper Temperature Probe contains the ECO
(energy cut out) and a Temperature Sensor. The Temperature Probe connects to the J9 Socket on the CCB. See CCB Circuit Board
Layout (page 35) and CCB Connection Identication (page 36).
ECO High Temperature Limit Switch
The ECO (energy cut out) is a high temperature limit switch designed to protect against excessively high water temperatures inside the
water heater’s storage tank. The ECO is a normally closed switch that opens on a rise in temperature. The ECO switch is located inside
the Temperature Probe (two red wires/Pins 2 & 3). See page 30 for pin layout. The ECO temperature setting is non adjustable; the
contacts open at approximately 201°F (94°C) and will close at approximately 140°F (60°C).
The Control System constantly monitors the state of the ECO switch contacts. If the ECO activates (contacts open) due to abnormally
high water temperature the Control System will lock out and display Energy Cut Out (ECO) on the UIM.

19
Should the ECO activate, the water temperature must drop below 140°F (60°C) before the Control System can be reset. Once the
water temperature has cooled below this point the electrical circuit breaker that serves the water heater must be turned off and on again
to reset the Control System.
Temperature Sensor
The Temperature Sensor located inside the Temperature Probe is a “thermistor” (two black wires/Pins 1 & 4). See page 30 for pin
layout. Thermistors are thermally sensitive resistors. As the water temperature rises the resistance (measured in ohms) of the sensor
will decrease; as the temperature falls the resistance will increase - see Table 1.
Figure 12. Temperature Sensor
The Control System interprets changes in the temperature sensor resistance as changes in water temperature and uses this data to
activate and deactivate heating cycles and displays this temperature in the Control System menus. See Figure 24 (page 40).
The Control System constantly monitors the Temperature Sensor. The Control System is programmed to declare a fault condition if the
resistance of the temperature sensor drops below 390 ohms (shorted) or above 56,000 ohms (open).
If the resistance of the Temperature Sensor is below 390 ohms the Control System will lock out and display Temp Probe Short on the
UIM. If the resistance of the temperature sensor is above 56,000 ohms the Control System will lock out and display Temp Probe Open
on the UIM. The electrical circuit breaker that serves the water heater must be turned off and on again to reset the Control System.
Note; the Control System will not reset unless the condition has been corrected.
TEMPERATURE SENSOR TEST
1. Turn off the circuit breaker that serves the water heater.
2. Remove the top cover on the water heater.
3. Disconnect the four pin plug/socket connection from the Temperature Probe outside the CCB enclosure in the middle, see Figures on
next page.
4. Using an ohm meter: set the ohm meter range to a scale just above 30,000 ohms.
5. Check resistance between the two inside pins (black wires/Pins 1 & 4) of the plug end from the Temperatures Probe, see Figures on
next page. Compare the measured resistance to the values given in “Temperatures” Table below. Temperature Probes are very reliable
and should only be replaced when:
• The resistance is above 56,000 ohms (open) or below 390 ohms (shorted).
• The nature of the service problem is temperature control and the resistance readings are considerably (± 25%) different than the
values in Temperatures Table below at the given temperature.
Table 1. Temperatures
Water Temperature Temperature Sensor
Resistance In Ohms
Celsius Fahrenheit
4° 40° 26,435
21° 70° 11,974
38° 100° 5,862
49° 120° 3,780
55° 130° 3,066
60° 140° 2,503
71° 160° 1,698
82° 180° 1,177
ECO CONTINUITY TEST
1. Turn off the circuit breaker that serves the water heater.
2. Remove the top cover on the water heater.
3. Disconnect the four pin plug from the Upper Temperature Probe, see Figure on Page 30.
4. Ensure tank temperature is less than 100°F (38°C) - dump water to lower tank temperature if necessary.

20
5. Using an ohm meter set the range for continuity testing.
6. Check continuity between the two outside pins (red wires/Pins 2 & 3) of the plug end from the Temperature Probe, see Figure on Page
20 pin layout.
Results/Actions
• If the ohm meter shows continuity (closed circuit) between the two outside pins (red wires/Pins 2 & 3) the ECO switch has reset
properly. If the Control System continues to lock out displaying Energy Cut Out (ECO) on the UIM with continuity through the ECO
present call the toll free support phone number listed on the back cover of this manual for further assistance.
• If the ohm meter shows no continuity (open circuit) between the two outside pins (red wires/Pins 2 & 3) and the tank temperature is
known to be at or below 100°F (38°C) - replace the Temperature Probe. Follow the draining and lling instructions in the
maintenance section of the Instruction Manual that came with the water heater when replacing the Temperature Probe.
• If the Control System continues to lock out displaying Energy Cut Out (ECO) on the UIM and the water temperature inside the
water heater is becoming excessive (at or above 201°F/94°C) check water system piping; ensure heat is not being added by any
other heating appliances or heat sources. If all these tests have been performed and the Control System continues to lock out call
the toll free support phone number listed on the back cover of this manual for further assistance.
Figure 13. Temperature Probe Pin Layout
9. TEMPERATURE PROBE OPEN
ADVANCEDBACK
Tem p Probe (Open)
0 days 0 hrs 0 mins ago
Error Code: 48-
0
The indicated temperature Probe
may be shorted or open. Check
connector and resistance of
Probe.
CAUSES:
• The Temperature Probe appears to be open (very high
resistance). This fault code often means the connector
has been corroded by cleaning chemicals or other
substances.
CHECK/ REPAIR:
• Make sure connector is clean and tight.
• Check probe’s resistance.
• Replace the Temperature Probe if open (resistance exceeds 56,000 Ohms). See 8. Temperature Probe Short (page 18).