A.O. Smith 100 Series Instruction manual

Service Handbook
COMMERCIAL GAS HIGH EFFICIENCY WATER HEATERS
500 Tennessee Waltz Parkway
Ashland City, TN 37015
FOR MODELS:
SUF 60120 THRU SUF 100250
SUF 119300 THRU SUF 119500
SERIES 200/201
INSTALLATION CONSIDERATIONS - PRE SERVICE CHECKS CONSTRUCTION - OPERATION & SERVICE - TROUBLESHOOTING
SERVICING SHOULD ONLY BE PERFORMED BY A QUALIFIED SERVICE TECHNICIAN
PRINTED IN THE U.S.A. 0914
329298-000
TABLE OF CONTENTS
INTRODUCTION........................................................................................2 VENTING..................................................................................................33
Qualifications.........................................................................................2
General Venting Information......................................................... 33
Service Warning....................................................................................2 INTAKE AIR CONNECTION.....................................................................34
Service Reminder..................................................................................2 ELECTRICAL CONNECTIONS – ALL MODELS......................................35
Electrical Wiring...................................................................................35
Tools Recommended.............................................................................2
INSTALLATION CONSIDERATIONS.........................................................3
Power Supply Connections.................................................................35
Instruction Manual.................................................................................3
Enable/ Disable Switch........................................................................36
Closed Water Systems..........................................................................3
Power Supply Test...............................................................................36
Thermal Expansion................................................................................3 INSTALLATION CHECK LIST..................................................................37
Air Requirements...................................................................................3 OPERATION AND SERVICE...................................................................38
Contaminated Air...................................................................................3
How It Works.......................................................................................38
FEATURES AND COMPONENTS.............................................................4
Combustion Blower.............................................................................38
Combustion Blower & Burner Assembly................................................4
Modulation...........................................................................................38
Top View: SUF 60120 - 100250 Models................................................5 BLOWER SPEED CONTROL – SUF 119300 THRU 119500...................40
Top View: SUF 119300 - 119500 Models...............................................5 VARIABLE FREQUENCY DRIVE – SUF 119300 THRU 119500.............41
SEQUENCE OF OPERATION FLOW CHART...........................................6 BURNER ASSEMBLY..............................................................................42
FAULT AND WARNING CODES................................................................7 COMBUSTION BLOWER AND BURNER REMOVAL/ INSTALLATION
INSTRUCTIONS.......................................................................................43
1. Low Gas Pressure.............................................................................7
SPARK IGNITER......................................................................................44
High Altitude..................................................................................7
GAS ORIFICE - SUF 119300 THRU 119500 MODELS...........................46
Gas Pressure Specifications......................................................... 7
Orifice Chart - SUF 119300 thru 119500 Models.................................46
Gas Supply Systems.....................................................................8
CCB (CENTRAL CONTROL BOARD)......................................................47
Supply Gas Regulator...................................................................8
CCB Cover Removal And Replacement..............................................48
Gas Pressure Test.........................................................................9
CCB Circuit Board Layout...................................................................49
2. Blower Operation Error....................................................................11
CCB Connection Identification.............................................................50
Pressure Switches........................................................................11
WIRING DIAGRAM – SUF 60120 THRU 100250....................................52
Control System Monitoring............................................................11
WIRING DIAGRAM – SUF 119300 THRU 119500...................................53
Pressure Switch Tests...................................................................12
CONTROL OVERVIEW............................................................................54
Continuity Test During Standby..................................................... 12
Continuity Test During Operation.................................................. 13
Pressure Test During Operation.................................................... 13
Pressure Switch Settings..............................................................14
3. Blower Prover Open........................................................................16
4. Ignition Failure.................................................................................17
5. Blocked Air Intake............................................................................20
6. Blocked Exhaust..............................................................................21
7. Flame Sensor Error.........................................................................22
Gas Control Valve.........................................................................22
Gas Control Valve Voltage Tests................................................... 23
Flame Sensor................................................................................24
Flame Sensing Operation.............................................................24
Flame Sensing Current Test..........................................................25
8. No Water..........................................................................................26
Powered Anodes...........................................................................26
Power anode cleaning and removal.............................................. 26
9. Anode Shorted.................................................................................28
10. Temperature Probe Short (Upper or Lower)..................................29
Temperature Probe.......................................................................29
Temperature Sensor Test..............................................................30
ECO Continuity Test......................................................................30
11. Temperature Probe Open (Upper or Lower)..................................32
1
INTRODUCTION
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 Qualified Agency (as defined
by ANSI below) in the field 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 2006 Sec. 3.3.83: “Qualified Agency” - “Any individual, firm, 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 qualified (as defined by ANSI above) and licensed or certified 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) - flame sensing current, see "Flame Sensing Current Test" on Page 25.
2
Servicing should only be performed by a Qualified Service Technician
INSTALLATION 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 flow 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 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 flammable 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 configuration 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.
Servicing should only be performed by a Qualified Service Technician
3
FEATURES AND COMPONENTS
COMBUSTION BLOWER & BURNER ASSEMBLY
Combustion Blower
Low Gas Pressure Switch
Gas Control Valve/
Venturi Assembly
Air Intake Assembly
Spark Igniter Ground Wire
Blower Gasket
Spark Igniter
Flame Sensor
Spark Igniter Gasket
Blower Adapter
Burner Gasket
Ignition Cable
Burner
Sight Glass
Sight Glass Gasket
Burner Plate
Burner Plate Gasket
(150-250 Models Only)
SS Heat Shield
(150-250 Models Only)
Flue Ring Gasket
SUF 60120 - 100250 Models
Ignition Cable
Spark Igniter
Air Intake Assembly Flame Sensor
Spark Igniter Gasket
Combustion Blower
Blower Gasket
Venturi
Sight Glass
Burner
Sight Glass Gasket
Burner Plate Gasket
SS Heat Shield
Burner Plate
Pyrolite Insulation Disk
SS Bolts & Washers
Insulation Spacers
SUF 119300 - 119500 Models
4
Servicing should only be performed by a Qualified Service Technician
TOP VIEW: SUF 60120 - 100250 MODELS
Powered Anode
(Short, SUF 100150-100250
Models Only)
Junction Box
Assembly
Burner/ Blower
Assembly
Ignition Control
Powered Anode
(Long)
Blower Prover
Switch
(Label Color: Green)
CCB Assembly
Blocked Air
Intake Switch
(Label Color: Blue)
Blocked Exhaust
Switch
(Label Color: Red)
Exhaust/
Condensate Elbow
Water Outlet
1 - 1/2” NPT
UIM
Upper Temperature Probe
TOP VIEW: SUF 119300 - 119500 MODELS
VFD
Junction Box
Assembly
Burner/ Blower
Assembly
Blower Prover Switch
(Label Color: Green)
Ignition Control
Blocked Air
Intake Switch
(Label Color: Blue)
Powered Anode
(Short)
Blocked Exhaust
Switch
(Label Color: Red)
CCB
Assembly
Powered Anode
(Long)
Water Outlet
1 - 1/2” NPT
UIM
Upper Temperature
Probe
Exhaust/
Condensate Elbow
Servicing should only be performed by a Qualified Service Technician
5
SEQUENCE OF OPERATION FLOW CHART
Sequence is shown with Enable/Disable Switch in the Enable position
If tank temperature drops below Operating Set Point minus
Differential setting a heating cycle is activated
Control System performs diagnostic checks
Normal State of all pressure switches and ECO are checked
Blower Prover pressure switch verified open
All other pressure switches and ECO are verified closed
NO
Control System Locks Out
Displays Fault Msg
Combustion Blower is energized
Pre-Purge cycle
Blower Prover switch contacts confirmed
closed by control system
NO
Control System Locks Out
“Blower Prover Open”
Fault Msg is displayed
Spark Ignition Control 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)
YES
Water is heated to
set point
24 Volt Gas Valve
de-energized
24 Volt Gas Valve
de-energized
Inter-Purge cycle
Post-Purge cycle
Water heater goes
into standby mode
6
NO
Retries up to
two more times
Control System
Locks Out
“Ignition Failure”
Fault Msg is
displayed
Servicing should only be performed by a Qualified Service Technician
FAULT AND WARNING CODES
1. LOW GAS PRESSURE
CAUSES:
Low Gas Pressure
• The Low Gas Pressure Switch is detecting gas
pressure below the value required for proper
operation.
Fault occurred 2 mins ago
Gas pressure is below minimum
required to operate this unit. Check
gas pressure and switch.
Call a service professional:
Your Company Name Here
(press [DOWN] for more....)
CHANGE
BACK
ADVANCED
CHECK/ REPAIR:
• Check Low Gas Pressure Switch wiring and connectors. Connectors must be clean and tight.
• Determine proper minimum pressure from rating plate.
• Use manometer or gauge to check gas pressure during all stages of operation with all other
appliances firing.
• 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 certified 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 PRESSURE SPECIFICATIONS
Natural
60120‑100250
Propane
60120‑100250
Natural
119300/119400/119500
Propane
119300/119400/119500
Maximum Gas Supply
Pressure
14.0" WC
(3.49 kPa)
14.0" WC
(3.49 kPa)
14.0" WC
(3.49 kPa)
14.0" WC
(3.49 kPa)
Nominal Gas Supply
Pressure
7.0" WC
(1.74 kPa)
11.0" WC
(2.74 kPa)
7.0" WC
(1.74 kPa)
11.0" WC
(2.74 kPa)
Minimum Gas Supply
Pressure (Low Gas
Press. Switch Setting)
4.4" WC
(1.10 kPa)
8.5" WC
(2.12 kPa)
4.8" WC
(1.19 kPa)
8.5" WC
(2.12 kPa)
0" WC
(0 kPa)
0" WC
(0 kPa)
0" WC
(0 kPa)
0" WC
(0 kPa)
MODELS
*Manifold Pressure
*The Manifold Pressure is the factory setting and is not adjustable. A negative pressure will be seen with just the blower running without
the Gas Control Valve open.
Servicing should only be performed by a Qualified Service Technician
7
GAS SUPPLY SYSTEMS
Low pressure building gas supply systems are defined 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 fire 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 field 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 specified 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.
For Natural Gas SUF 60120 - 100250 models require a minimum gas supply pressure of 4.4" W.C., SUF
119300 - 119500 models require 4.8" W.C., and all models require 8.5" W.C. for propane gas. The minimum
supply pressure is measured while gas is flowing (dynamic pressure) along with all additional gas appliances
operating on the same gas supply system. The supply pressure should be measured with all gas fired
appliances connected to the common main firing at full capacity. If the supply pressure drops more than
1.5” W.C. (0.05 PSI Gauge) when the water heater is operating at high fire rate, then the supply gas system
including the gas line and/or the gas regulator may be restricted or undersized. See Supply Gas Regulator
section below. The Gas Control Valve on all models has a maximum gas supply pressure limit of 14” W.C.
(1/2 PSI Gauge). The maximum supply pressure is measured while gas is not flowing (static pressure) to any
appliances connected to the same gas supply system.
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) 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 specifications.
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.
8
Servicing should only be performed by a Qualified Service Technician
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.
Service notes:
• The manifold gas pressure is factory set and cannot be adjusted in the field.
• There are two pressure test ports on the water heater’s 24 Volt Gas Control Valve, see Figure below. The
Gas Control Valve outlet pressure test port is closest to the Combustion Blower, see Figure below. There
is a needle valve in each test port that is opened/closed with a small slotted screwdriver. Turn the needle
valve counter-clockwise to open the test port valve and clockwise to close it.
• The hose from the Gas Control Valve supply gas pressure test port should be connected to the positive
pressure port of a manometer; the other pressure port of a manometer should be left open.
• 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 flowing.
• 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 flame 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, see Figures below. Turn the needle
valve slotted head 1/2 to 1 full turn counter-clockwise with a small slotted screwdriver to open the valve.
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
flowing) supply gas pressure.
MANIFOLD GAS
PRESSURE
TEST PORT
SUPPLY GAS
PRESSURE
TEST PORT
AIR INTAKE PRESSURE
REFERENCE CONNECTION
GAS CONTROL
VALVE
COMBUSTION
BLOWER
CONNECTION
COMBUSTION
AIR INLET
VENTURI
SUF 60120 - 100250 Models
MANIFOLD GAS
PRESSURE
TEST PORT
SUPPLY GAS
PRESSURE
TEST PORT
SUF 119300 - 119500 Models
Servicing should only be performed by a Qualified Service Technician
9
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.
Putting The Water Heater Back In Service
10.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.
11.Close the main gas shutoff valve serving the water heater.
12.Disconnect manometer sensing tube.
13.Close the Supply Gas Pressure Test Port on the Gas Control Valve. Turn the needle valve slotted head
clockwise until tight.
14.Open the main gas shutoff valve serving the water heater and check for leaks at the Gas Control Valve
test ports.
15.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.
16.Run the water heater through a complete heating cycle before leaving to ensure it is operating properly.
Return the Operating Set Point Temperature to its original setting. Draw water from the nearest faucet to
make sure that the water temperature does not pose a scalding hazard due to the increased temperature
set points that were used in this procedure.
10
Servicing should only be performed by a Qualified Service Technician
2. BLOWER OPERATION ERROR
Blower Operation Error
Fault occurred 2 mins ago
Blower Prover Pressure Switch may
have failed closed. Check/replace
pressure switch.
CAUSES:
• The Blower Prover Pressure Switch was detected
closed before blower operation.
Call a service professional:
Your Company Name Here
(press [DOWN] for more....)
CHANGE
BACK
ADVANCED
CHECK/ REPAIR:
• This switch is normally open and is used to prove blower operation. This switch should be open when
blower is not running. Check continuity of pressure switch. See "Pressure Switch Tests" section on Page
12 thru Page 15.
PRESSURE SWITCHES
The water heaters covered in this Service Handbook are factory equipped with four pressure switches
(including the Low Gas Pressure Switch). "Top View" Figures on Page 5 shows the location of the three
pressures switches on top of the water heater. This section of the Service Handbook covers pressure switch
construction, operation and the test procedures used to diagnose operational problems associated with
pressure switches. The pressure switches are identified with colored labels; Blower Prover Switch is Green,
Blocked Air Intake Switch is Blue, & Blocked Exhaust Switch is Red.
CONTROL SYSTEM MONITORING
The Control System monitors the “state” of the pressure switch contacts individually through three separate
circuits, see "Wiring Diagrams" on Page 52 & Page 53. The state of the switch refers to whether the switch
contacts are open or closed.
At the beginning of a heating sequence, before the Combustion Blower is energized, the Control System
enters the Input Verification operating state. During Input Verification the Control System monitors all three
pressure switches to ensure their contacts are in the correct "normal" state. The Blower Prover switch contacts
must be open. The contacts for the Blocked Air Intake Switch and Blocked Exhaust Switches must be closed.
If any of the pressure switch contacts are not in their correct normal state during Input Verification the Control
System will lock out and display a fault message on the UIM indicating which pressure switch caused the
fault condition. If all system checks pass during the Input Verification operating state the Control System
enters the Pre-Purge operating state and energizes the Combustion Blower. The Heater Status Screen and
functionality of the water heater can be used for troubleshooting.
After the Combustion Blower is energized the Control System must confirm the Blower Prover switch contacts
have closed, see the "Sequence Of Operation Flow Chart" on Page 6. The Blocked Air Intake Switch and
Blocked Exhaust Switch contacts must remain closed at all times.
If the Blower Prover switch contacts are closed during the Input Verification the Control System will lock out
and display Blower Prover Failure on the UIM. If the Blower Prover switch contacts do not close after the
Combustion Blower is energized the Control System will lock out and display Blower Prover Open on the
UIM. If either the Blocked Air Intake Switch or Blocked Exhaust Switch contacts open at any time during a
heating sequence the Control System will lock out and display Blocked Air Intake or Blocked Exhaust
on the UIM. Wires connecting to air switches are labeled near the terminals. Ensure no mis-wiring among
terminals.
Servicing should only be performed by a Qualified Service Technician
11
PRESSURE SWITCH TESTS
Complete pressure switch testing involves three procedures:
• "Continuity Test During Standby" below.
• "Continuity Test During Operation" on Page 13.
• "Pressure Test During Operation" on Page 13 thru Page 15.
CONTINUITY TEST DURING STANDBY
This test is performed while the Combustion Blower is not running with the water heater turned off. This is a
"normal state" continuity test of the contacts inside each pressure switch. Disconnect the two wires to each
pressure switch for this test.
1. If the water heater is in a heating cycle lower the Operating Set Point to end the cycle.
2. Turn off the circuit breaker that serves the water heater.
3. Disconnect both wires at each pressure switch.
4. Using an ohm meter set for continuity testing, check for continuity between the two wiring terminals at
each pressure switch, see Figure below.
5. After completing the tests, confirm that all of the pressure switch wires are reconnected including the
replacement part if necessary based on the Results/Actions listed below. Restore the electrical power
to the water heater. Reset the Operating Temperature Set Point if it was adjusted. Run the water heater
through a complete heating cycle before leaving to ensure it is operating properly.
Results/Actions
Passed Results: If the Blower Prover switch contacts are open during this test (infinite ohms/open circuit)
the Blower Prover switch has passed the test. If the Blocked Air Intake Switch and Blocked Exhaust Switch
contacts are closed during this test, (zero ohms/direct short), these switches have passed the test.
Failed Results: If the Blower Prover switch contacts are closed (zero ohms/direct short/beep) during this
test, the Blower Prover switch must be replaced. If the Blocked Air Intake Switch and/or Blocked Exhaust
switch contacts are open during this test, the switch(s) must be replaced.
Proceed to the Continuity Test During Operation on next page.
12
Servicing should only be performed by a Qualified Service Technician
CONTINUITY TEST DURING OPERATION
This test is performed while the Combustion Blower is running at high speed during the Pre-Purge operating
state. The test is performed on all three pressure switches. Disconnect the two wires to each pressure switch
- one at a time, check continuity and then reconnect the wires to that switch before testing the next switch.
1. Turn off the circuit breaker that serves the water heater.
2. Ensure the sensing tubes from each pressure switch are connected to the correct sensing port on the
water heater.
3. Disconnect the two wires for the switch to be tested.
4. When testing the Blocked Exhaust and Blocked Air Intake Switches, connect a jumper wire between the
two wires disconnected. This will temporarily prevent the Control System from locking out during the test.
When the test for these two switches is complete, remove the jumper wire and reconnect the pressure
switch wiring before moving on to the next switch.
5. Restore power to the water heater, if the water heater does not begin a heating cycle raise the Operating
Set Point to activate a heating cycle.
6. Using an ohm meter set for continuity testing, check for continuity between the two wiring terminals at the
pressure switch after the Combustion Blower has started and ramped up to high speed during the PrePurge operating state. Record the results; open or closed.
7. Repeat this procedure for each pressure switch.
8. Turn off the circuit breaker that serves the water heater. Confirm that all of the pressure switch wires
are reconnected including the replacement part if necessary based on the Results/Actions listed below.
Restore the electrical power to the water heater. Reset the Operating Temperature Set Point if it was
adjusted. Run the water heater through a complete heating cycle before leaving to ensure it is operating
properly. Draw water from the nearest faucet to make sure that the water temperature does not pose a
scalding hazard due to the increased temperature set points that were used in this procedure.
Results/Actions
Passed Results: If the Blower Prover switch contacts activate/close (zero ohms/direct short) during this test
the switch has passed this test. If the Blocked Air Intake Switch and Blocked Exhaust Switch contacts remain
closed during this test, (zero ohms/direct short), these switches have passed the test.
Failed Results: If the Blower Prover switch contacts do not close during this test, the Pressure Test During
Operation below must be performed to determine if the switch is defective. If the Blocked Air Intake Switch
or Blocked Exhaust switch contacts open during this test, the Pressure Test During Operation below must be
performed to determine if the switch(s) is defective. Proceed to the Pressure Test During Operation below.
PRESSURE TEST DURING OPERATION
This test will be performed while the Combustion Blower is running at high speed during the Pre-Purge
operating state. This test is necessary when a pressure switch has passed the "Continuity Test During
Standby" shown on Page 12 but has failed the Continuity Test During Operation above to determine if the
pressure switch is defective or not. This test requires a digital manometer, see "Tools Recommended" on
Page 2.
Service Notes:
• Before performing this test examine the sensing tube connections on the water heater’s sensing ports
and on the pressure switch. Check for wear, cracks, leaks, kinks, or any kind of debris or condensate in
the sensing tubes, repair/replace as necessary.
• To determine if a pressure switch is operating properly you must first know the "switch action" (whether
the switch activates on a rise or a fall in pressure) and the "activation pressure" the switch will activate
at. Activation pressures are provided in "Pressure Switch Settings" Table on Page 14. Switch actions are
as follows:
Servicing should only be performed by a Qualified Service Technician
13
• Blower Prover Switch - normally open contacts, close on a rise in pressure.
• Blocked Air Intake Switch - normally closed contacts, open on a fall in pressure.
• Blocked Exhaust Switch - normally closed contacts, open on a rise in pressure.
Activation Pressures: Pressure Switch Settings Table below shows the activation pressures and tolerance
for each of the three pressure switches. A + sign before the pressure indicates a positive pressure; above
atmospheric pressure. A - sign before the pressure indicates a negative pressure (in a vacuum); below
atmospheric pressure. Tolerances are specified to allow reasonable leeway for imperfections and inherent
variability without compromising performance.
PRESSURE SWITCH SETTINGS
Models
Blower Prover
(+/- 0.05" WC)
Blocked Air
Intake
(+/-0.05" WC)
Blocked Exhaust
(+/-0.05" WC)
Low gas (+/-0.04" WC Nat/
+/-0.05" WC LP)
SUF 60120
0.75" W.C.
-2.50" W.C.
2.00" W.C.
4.4" W.C. Nat/8.5" W.C. LP
SUF 100150 - 100250
1.00" W.C.
-2.50" W.C.
2.00" W.C.
4.4" W.C. Nat/8.5" W.C. LP
SUF 119300 - 119500
1.00" W.C.
-2.30" W.C.
2.00" W.C.
4.8" W.C. Nat/8.5" W.C. LP
Pressure Test:
1. Turn off the circuit breaker that serves the water heater.
2. Disconnect the sensing tube from the switch being tested and add a 3/16" tee to the sensing tube. Add a
short piece of sensing tube connecting the tee and the pressure switch being tested.
3. Connect a digital manometer to the open side of the tee with another piece of sensing tube.
4. Restore power to the water heater, if the water heater does not begin a heating cycle raise the Operating
Set Point to activate a heating cycle.
5. When the Combustion Blower comes on and ramps up to full speed, record the pressure reading.
6. Repeat this test for all three pressure switches as necessary.
7. Compare the pressure readings taken to the activation pressures in the Table above.
8. Ensure all sensing tubes are properly routed and reconnected when testing is complete. The pressure
switches will not operate properly if there are leaks in the tubing. Reset the Operating Temperature Set
Point if it was adjusted. Run the water heater through a complete heating cycle before leaving to ensure
it is operating properly. Draw water from the nearest faucet to make sure that the water temperature does
not pose a scalding hazard due to the increased temperature set points that were used in this procedure.
Results/Actions
Blower Prover: If the pressure reading taken at the Blower Prover switch sensing tube is at or above the
activation pressure shown in the above Table AND the switch contacts did not close during the "Continuity
Test During Operation" shown on Page 13 - the switch is defective and must be replaced. If the pressure
reading taken does not reach or rise above the activation pressure in the above Table the pressure switch IS
NOT defective and should not be replaced - call the toll free phone number on the back cover of this Service
Handbook for further technical assistance. Have the complete Model, Series and Serial number (located on
the water heater's rating label) for the water heater being serviced on hand before calling.
14
Servicing should only be performed by a Qualified Service Technician
Blocked Air Intake: Note these are negative pressures; in a vacuum. If the pressure reading taken at the
Blocked Air Intake Switch sensing tube does not reach or drop lower than the pressure shown in the above
Table AND the switch contacts were opening during the "Continuity Test During Operation" shown on Page
13 - the switch is defective and must be replaced. If the pressure reading taken reaches or drops lower
than the pressure shown in the "Pressure Switch Settings" Table on Page 14 and the switch contacts were
opening during the "Continuity Test During Operation" shown on Page 13 - the switch IS NOT defective and
should not be replaced. Check for restrictions at the intake air connection on the water heater, check for too
small of pipe installed, too many equivalent feet and/or too many elbows in the intake air piping. Check for
low points in the intake air piping where water may be collecting and blocking the intake air piping. Check for
any restrictions or debris at the intake air termination outdoors. Check for condensate/water in the sensing
tube/switch, if the sensing tube has water in it, replace the Blocked Air Intake Switch and the tube. Ensure
the sensing port is oriented properly, see "Intake Air Connection" on Page 34.
Blocked Exhaust: If the pressure reading taken at the Blocked Exhaust switch sensing tube does not
reach or rise above the activation pressure given in the above Table AND the switch contacts were opening
during the "Continuity Test During Operation" on Page 13 - the switch is defective and must be replaced. If
the pressure reading taken reaches or exceeds the pressure shown in the "Pressure Switch Settings" Table
on Page 14 and the switch contacts were opening during the "Continuity Test During Operation" on Page
13 - the switch IS NOT defective and should not be replaced. Ensure the condensate drain connected to the
exhaust elbow on the water heater is not clogged and is draining freely. Check for restrictions or blockage in
the vent pipe, check for too small of pipe installed, too many equivalent feet and/or too many elbows in the
vent piping. Check for low points in the vent pipe where water may be collecting and blocking the vent piping.
Check for any restrictions or debris at the vent termination outdoors.
Servicing should only be performed by a Qualified Service Technician
15
3. BLOWER PROVER OPEN
Blower Prover Open
Fault occurred 2 mins ago
The blower prover switch remains
open after the blower has been
energized.
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CAUSES:
• The control has detected an open Blower Prover
Pressure Switch during operation.
• Blower Prover Pressure Switch sensing tube
disconnected or kinked.
• Loose or open wiring connections to Blower
Prover Pressure Switch.
• Blower not running when expected.
• Blower Prover Pressure Switch not operating
(Replace Blower Prover Switch).
CHECK/ REPAIR:
• The blower prover pressure switch will close its contacts on a pressure rise. See "Pressure Switch Tests"
section on Page 12 thru Page 15 under "Blower Operation Error" on Page 11.
16
Servicing should only be performed by a Qualified Service Technician
4. IGNITION FAILURE
CAUSES:
Ignition Failure
Fault occurred 2 mins ago
Flame not detected. Clean flame rod.
Check gas supply.
• On an “Ignition Failure” error, either the burner is
not igniting or the burner is igniting, but the Flame
Sensor is not detecting ignition (flame).
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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 flame (if you are getting an Ignition Failure error, the flame, if the burner ignites, will only be
present for 2-3 seconds).
BURNER IGNITES (BRIEFLY)
• If the burner ignites briefly then shuts off with an “Ignition Failure” error message, follow these steps:
• Remove the connector from flame 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.
CONTROL SYSTEM
APPLIES AC CURRENT
TO FLAME SENSOR
SPARK
IGNITER
FLAME SENSOR
CERAMIC INSULATOR
METAL CONDUCTOR
AC 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
AND THE BURNER.
BURNER
FLAME
BURNER
(MUST BE GROUNDED)
Servicing should only be performed by a Qualified Service Technician
17
• 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 flame sense rod still fails
to detect flame, contact Commercial Technical Support.
BURNER DOES NOT IGNITE
Failure to ignite (no flame) usually means a gas supply or Gas Control Valve problem. If you do not see a
brief blue flame through the sight glass during the ignition cycle (at the moment the Gas Control Valve icon
appears on the display), follow these steps:
• Remove and reinsert the Gas Control Valve electrical connector. Make sure the electrical connections
(pins) are clean and that the connector fits tightly.
24 VAC SOLENOID
& WIRE HARNESS
GAS CONTROL
VALVE
SUPPLY GAS
CONNECTION
LOW GAS
PRESSURE SWITCH
COMBUSTION
AIR INLET
VENTURI
GAS CONTROL VALVE ASSEMBLY: SUF 60120 - 100250 MODELS
SUPPLY GAS
CONNECTION
LOW GAS
PRESSURE
SWITCH
24 VAC SOLENOID
& WIRE HARNESS
GAS CONTROL VALVE ASSEMBLY: SUF 119300 - 119500 MODELS
18
Servicing should only be performed by a Qualified Service Technician
• Remove and reinsert the circuit board end of the Gas Control Valve connector. Make sure it is connected
tightly and that the pins are clean.
• Recycle unit again to start another ignition cycle. If you still do not see a brief blue flame through the sight
glass at the moment the Gas Control Valve icon appears on the display, verify that 24 VDC is present on
the connector pins 1 and 5. Use care to not bend or damage the pins while testing.
• Connect test leads to the Gas Control Valve connector’s pins. Gently connect probes to Gas Control Valve
connector’s two outer pins. Set the meter to DC volts.
• Recycle unit again to start an ignition cycle.
• At the moment the Gas Control Valve icon appears on the display, you should see 24 VDC on your meter.
This electrical signal will only last for 2-3 seconds (if the burner does not ignite or the flame sensor does
not detect ignition).
24 VDC PRESENT
• If 24 VDC is present on the Gas Control Valve connector during the beginning of an ignition cycle, reinstall
the connector and recycle the unit again.
• Check the gas supply pressure during ignition using test procedure from "Gas Pressure Test" on Page 9.
• During the ignition cycle, the gas supply pressure should drop about 0.5” to 1.5” W.C. when the Gas Control
Valve icon appears if the Gas Control Valve is working. If the gas supply pressure does not drop at the
beginning of the ignition cycle, the Gas Control Valve may be defective—contact Commercial Technical
Support. A pressure drop of more than 1.5” W.C indicates an issue with the gas supply (pipe too long or
too small, bad regulator, etc.).
24 VDC NOT DETECTED
• If 24 VDC is not detected on the connector terminals when the Gas Control Valve icon appears on the
display, contact Commercial Technical Support.
Servicing should only be performed by a Qualified Service Technician
19
5. BLOCKED AIR INTAKE
Blocked Air Intake
Fault occurred 2 mins ago
Restriction in air intake. Check
intake pipe and termination for
blockage.
CAUSES:
• The Blocked Air Intake Switch has detected a
possible restriction in the air intake pipe.
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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. See "Pressure Switch Tests" section
on Page 12 thru Page 15 under "Blower Operation Error" on Page 11.
20
Servicing should only be performed by a Qualified Service Technician
6. BLOCKED EXHAUST
Blocked Exhaust
Fault occurred 2 mins ago
Restriction in exhaust pipe. Check
exhaust pipe and termination for
blockage.
CAUSES:
• The Blocked Exhaust Switch has detected a
possible restriction in the exhaust pipe.
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ADVANCED
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. See "Pressure Switch Tests" section
on Page 12 thru Page 15 under "Blower Operation Error" on Page 11.
Servicing should only be performed by a Qualified Service Technician
21
7. FLAME SENSOR ERROR
CAUSES:
Flame Sensor (error)
• The Flame Sensor has detected flame when the
Gas Control Valve is supposed to be off.
Fault occurred 1 mins ago
Flame Sensor rod detected flame
when gas valve should be off.
Shut off gas until repaired.
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ADVANCED
CHECK/ REPAIR:
• Look through sight glass. If flame is present, shut the main gas supply off. See Gas Control Valve section
below to confirm proper operation.
• If flame 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. See "Flame
Sensor" section on Page 24 thru Page 25.
GAS CONTROL VALVE
The 24 Volt Gas Control Valve on these water heaters is DC voltage valve. The CCB sends 24 VAC to the
valve and the AC voltage is rectified into a DC voltage by electronics contained inside the plug end of the 24
Volt Gas Control valve wiring harness, see Figures below.
24 VAC SOLENOID
& WIRE HARNESS
GAS CONTROL
VALVE
SUPPLY GAS
CONNECTION
LOW GAS
PRESSURE SWITCH
COMBUSTION
AIR INLET
VENTURI
GAS CONTROL VALVE ASSEMBLY: SUF 60120 - 100250 MODELS
22
Servicing should only be performed by a Qualified Service Technician
SUPPLY GAS
CONNECTION
LOW GAS
PRESSURE
SWITCH
24 VAC SOLENOID
& WIRE HARNESS
GAS CONTROL VALVE ASSEMBLY: SUF 119300 - 119500 MODELS
GAS CONTROL VALVE VOLTAGE TESTS
1. The animated Gas Control Valve Status Icon is displayed on the Control System UIM during these
operating states. See "(UIM) User Interface Module Screen" Figure on Page 54. Check for 24 VAC
supplied to the 24 Volt Gas Control Valve at pins 11 and 12 of the J14 Plug on the CCB, see "CCB Cover
Removal And Replacement" on Page 48 and "CCB Circuit Board Layout" on Page 49. Using an "AC"
volt meter insert the two test probes into pins 11 and 12 of the J14 Plug on the CCB during the Ignition
Verification or Heating operating states, see Figure below. 24 VAC should be present. Note that the Gas
Control Valve Voltage is only present for a short period of time during the ignition period.
2. Check for 24 VDC at the plug end of the 24 Volt Gas Control Valve wiring harness during the Ignition
Verification operating state. Loosen the retaining screw for the 24 Volt Gas Control Valve wiring harness
plug and disconnect the plug, see "Gas Control Valve" on Page 22. Lay the plug end upside down on a
flat surface. Using an "DC" volt meter insert the two test probes into the two outside plug sockets, see
Figure below. 24 VDC should be present.
AC VOLTAGE TEST
DC VOLTAGE TEST
Servicing should only be performed by a Qualified Service Technician
23
FLAME SENSOR
Ignition of the Burner is controlled electronically. The principle of operation for electronic ignition relies on
flame sensing current to prove the fuel gas flowing to the Burner has been ignited.
Flame sensing requires an adequate earth ground to the water heater's Burner, see "Electrical Connections"
on Page 35.
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 flame will conduct a small amount of electrical current.
• The burner must be properly grounded for current to flow from the Flame Sensor to the Burner.
• During ignition the burner flame must make complete and continuous contact with the Flame Sensor.
• As the AC current flows from the Flame Sensor through the burner flame to the (grounded) Burner the
AC current is "rectified" and becomes a DC current.
• The current flowing 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 2.
CONTROL SYSTEM
APPLIES AC CURRENT
TO FLAME SENSOR
SPARK
IGNITER
FLAME SENSOR
CERAMIC INSULATOR
METAL CONDUCTOR
AC 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
AND THE BURNER.
BURNER
FLAME
BURNER
(MUST BE GROUNDED)
MINIMUM FLAME SENSING CURRENT
To prove burner flame during the Ignition Verification state the Control System monitors flame sensing
current, the DC micro amp (μA) current flowing through the Flame Sensor. The Control System must sense a
minimum amount of current to “prove” flame. The minimum flame sensing current is 1.0 μA. If flame 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 flame 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" on Page 6.
24
Servicing should only be performed by a Qualified Service Technician
FLAME SENSING CURRENT TEST
During the heating cycle the flame 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 flame sensing current. With heavier use, more
heating cycles/greater load, this will occur more quickly.
Measuring flame sensing current requires a test meter with a DC micro amp function, see "Tools Recommended"
on Page 2. The meter’s selector is set to DC micro amps. The two test leads from the meter are placed in
series with the flame sensing circuit. This can be done at the spade (male/female) flame sensing wiring
connectors. See Figure below.
To measure flame 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 flame 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 flame sensing current is below 8 µA or the Burner has
been removed. Clean the Flame Sensor with ultra fine 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 flame 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" on Page 25.
• The Burner not being grounded will cause Ignition Failure - see "Electrical Connections" on Page 35.
Ensure the water heater and the Burner are properly grounded.
Servicing should only be performed by a Qualified Service Technician
25
8. NO WATER
CAUSES:
Alert:
• 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.
No Water
Alert occurred 2 mins ago
No water detected by Powered
Anode.
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CHECK/ REPAIR:
POWERED ANODES
The water heaters covered by this Service Handbook are equipped with powered anodes. SUF 60120
models only use 1 powered anode, all others will have two. 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.
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.
26
Servicing should only be performed by a Qualified Service Technician
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.
FRONT ANODE REPLACEMENT METHOD:
1. Remove blue wire from anode brass terminal.
2. Using a (1-1/16”) socket remove the anode.
3. Use a round wire brush to clean the spud threads. If reusing the same anode, clean the bottom disc on
the anode flange.
4. Apply Teflon tape pipe sealant to the new anode threads (as shown below), then insert anode and tighten
securely.
5. Reconnect blue wire to anode brass terminal.
6. If necessary, bend brass terminal tab up to allow for socket tool to fit properly.
REAR ANODE REPLACEMENT METHOD:
1. Remove the two blower connectors from the blower; remove gas valve power plug and the two wires from
the low gas pressure switch.
2. Remove air intake rubber boot from blower.
3. Disconnect gas supply connection from gas valve.
4. Remove the four (4) blower mounting screws to remove blower. Using a T-handle or hex head wrench
usually provides adequate access.
5. Remove blower assembly with gas valve attached.
6. Repeat steps 1-6 from the Front Anode Replacement Method.
RE-ASSEMBLY:
1. Replace blower gas valve assembly; re-install the four (4) blower mounting screws.
2. Re-connect gas supply to the gas valve.
3. Re-install the air intake rubber boot to the blower.
4. Connect the two blower connector wires; connect the gas valve power supply plug and the two low gas
pressure switch wires.
5. Turn on the water supply; be sure tank is filled with water.
6. Check the power anode voltage to measure the tank potential.
7. Turn on the gas and power supply.
8. Restart the heater.
Servicing should only be performed by a Qualified Service Technician
27
9. ANODE SHORTED
CAUSES:
Alert:
Anode Shorted
Alert occurred 0 mins ago
The Powered Anode is shorted
to earth ground or the tank.
• The controller has detected a low resistance or
short to earth ground or the tank.
Note: This is an alert. The unit
will continue to heat water in
(press [DOWN] for more....)
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ADVANCED
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"
section on Page 26.
28
Servicing should only be performed by a Qualified Service Technician
10. TEMPERATURE PROBE SHORT (UPPER OR LOWER)
CAUSES:
Upper Temp Probe (Short)
• 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.
Fault occurred 0 mins ago
Upper Temperature Probe may be
shorted. Check connector and
resistance of Probe.
Press the Advanced button for
(press [DOWN] for more....)
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ADVANCED
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 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" on Page 49 and "CCB
Connection Identification" on Page 50.
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). The ECO temperature setting is non adjustable; the contacts open at
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.
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). 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 "Temperatures" Table on next
page.
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 "(UIM) User Interface Module Screen" Figure on Page 54.
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).
Servicing should only be performed by a Qualified Service Technician
29
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) of the plug end from the Temperature 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.
TEMPERATURES
WATER TEMPERATURE
CELSIUS
FAHRENHEIT
TEMPERATURE SENSOR
RESISTANCE IN OHMS
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 Temperature Probe outside the CCB enclosure in the middle, see
Figure on Page 31.
4. Ensure tank temperature is less than 100°F (38°C) - dump water to lower tank temperature if necessary.
5. Using an ohm meter set the range for continuity testing.
6. Check continuity between the two outside pins (red wires) of the plug end from the Temperature Probe,
see Figure on Page 31.
30
Servicing should only be performed by a Qualified Service Technician
Results/Actions
• If the ohm meter shows continuity (closed circuit) between the two outside pins (red wires) 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) and the
tank temperature is known to be at or below 100°F (38°C) - replace the Temperature Probe. Follow
the draining and filling 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.
Servicing should only be performed by a Qualified Service Technician
31
11. TEMPERATURE PROBE OPEN (UPPER OR LOWER)
Lower Temp Probe (Open)
Fault occurred 0 mins ago
Lower Temperature Probe may be
open. Check connector and
resistance of Probe.
CAUSES:
• The Upper or Lower 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.
Press the Advanced button for
(press [DOWN] for more....)
CHANGE
BACK
ADVANCED
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 Temperature Probe
section under "Temperature Probe Short (Upper or Lower)" section on Page 29.
32
Servicing should only be performed by a Qualified Service Technician
VENTING
This section of the Service Handbook is not a complete venting installation instruction. Refer to the Instruction
Manual that came with the water heater; ensure the venting has been installed per all Instruction Manual
requirements. Costs to correct installation errors are not covered under the limited warranty.
GENERAL VENTING INFORMATION
The water heaters covered in this Service Handbook are operationally equivalent to Category IV appliances
and may be installed in either a Power Vent or Direct Vent configuration.
Category IV Appliance
Category IV appliances operate with a positive vent (exhaust) static pressure and with vent gas temperatures
low enough to produce condensate in the vent piping.
Power Vent Configuration
Power Vent configurations derive all combustion air from the room where they are installed and discharge all
flue gases to the outdoor atmosphere through a sealed vent (exhaust) pipe. Power vent configurations have
one vent pipe connected to the water heater which can be terminated in a vertical or horizontal arrangement.
Direct Vent Configuration
Direct Vent configurations derive all combustion air directly from the outdoor atmosphere through a sealed
intake air pipe and discharge all flue gases to the outdoor atmosphere through a sealed vent (exhaust) pipe.
Direct Vent configurations have two pipes connected to the water heater, one vent pipe and one intake air
pipe. Direct Vent configurations can also be terminated in a vertical or horizontal arrangement.
PIPE SIZE REQUIREMENTS
Ensure the correct size pipe has been used for the length of intake air and/or vent piping installed. Refer to
the Instruction Manual supplied with the water heater for the correct size and length of vent piping.
Servicing should only be performed by a Qualified Service Technician
33
INTAKE AIR CONNECTION
The intake air connection has a screen and a hose barb installed at the factory, see Figure below.
The intake air connection screen is installed to prevent debris from entering the Combustion Blower and/or
Burner. This screen is left in place when the water heater is installed in a Power Vent configuration but must
be removed before connecting the intake air piping on Direct Vent installations. Once the intake air pipe is
installed the screen, if not removed, would be hidden from view and may become clogged with debris over
time. This can cause poor combustion and Blocked Air Intake fault conditions and Control System lock outs.
Ensure this screen has been removed on all Direct Vent installations if experiencing Blocked Air Intake fault
conditions.
AIR INTAKE SCREEN
AIR INTAKE SCREEN
(remove for Direct Vent)
(remove for Direct Vent)
3 INCH INTAKE AIR CONNECTION
FACTORY INSTALLED
INTAKE AIR CONNECTION DETAIL
4” x 3” REDUCER
COUPLING - FACTORY INSTALLED
INTAKE AIR CONNECTION DETAIL
SUF 60120 - 100250 Models
SUF 119300 - 119500 Models
AIR INTAKE SCREEN
Service Notes:
• Plastic debris left on the edges of intake air pipe sections after cutting must be removed on Direct Vent
installations. This debris can collect inside and clog the Burner which can cause poor combustion,
sooting, rough starting, rough operation and Ignition Failure fault conditions and Control System lock
outs. The Burner is a radial design that can trap debris, see "Combustion Blower & Burner Assembly"
section on Page 4.
• Exceeding the equivalent length limitations for the vent piping will cause Blocked Exhaust fault
conditions and Control System lock outs.
• Exceeding the equivalent length limitations for the intake air piping will cause Blocked Air Intake fault
conditions and Control System lock outs.
• Exceeding the maximum number of elbows allowed for the intake air and/or vent piping will also cause
Blocked Air Intake and Blocked Exhaust fault conditions and Control System lock outs.
• Using smaller intake air and/or vent pipe than required for the installed equivalent length will also cause
Blocked Air Intake and Blocked Exhaust fault conditions and Control System lock outs.
34
Servicing should only be performed by a Qualified Service Technician
ELECTRICAL CONNECTIONS – ALL MODELS
The water heaters covered in this Service Handbook require a 120 VAC, 1Ø (single phase), 60Hz, 15 amp
power supply and must also be electrically grounded in accordance with local codes or, in the absence of
local codes, with the National Electrical Code, ANSI/NFPA 70 or the Canadian Electrical Code, CSA C22.1.
POWER FLUCTUATIONS AND ELECTRICAL NOISE
The water heater’s control system requires a source of stable clean electricity for proper operation. Connecting
the water heater to a branch circuit that is subject to fluctuations in voltage level or electrical line noise
such as EMI (electro magnetic interference) or RFI (radio frequency interference) may cause erratic control
system operation and malfunction.
A high quality power supply filter/suppressor must be installed if the above conditions exist. Call the technical
support phone number listed on the back cover of this Service Handbook for more information.
Note: Malfunctions caused by power supply and costs to install power supply filters are not covered under
the limited warranty.
DEDICATED POWER WIRING AND BREAKERS
Dedicated power supply wires, ground wiring and dedicated circuit breakers often reduce electrical line noise
and are required when installing the water heater.
ELECTRICAL WIRING
All electrical work must be installed in accordance with the National Electrical Code, ANSI/NFPA 70 or the
Canadian Electrical Code, CSA C22.1 and local requirements.
When installed, the water heater must be electrically grounded in accordance with local codes or, in the
absence of local codes, with the National Electrical Code, ANSI/NFPA 70 or the Canadian Electrical Code,
CSA C22.1.
If any of the original wire as supplied on the water heater must be replaced, it must be replaced with UL Listed
Power Limited Circuit Cable of the same size and rating as original wiring.
POWER SUPPLY CONNECTIONS
The 120 VAC black (hot) wire from the power supply must connect to the black lead wire or the "L1" terminal
block location in the junction box and the 120 VAC white (neutral) wire must connect to the white lead wire
or the "Neutral" terminal block location in the junction box for correct polarity. See "Junction Box Assembly"
Figure on next page.
Power supply connections must be made as follows:
1. Turn off the electrical circuit breaker that serves the water heater.
2. Remove the junction box cover.
3. Connect the 120 VAC black (hot) wire from the power supply to the black lead wire or the terminal
block location marked "L1" inside of the junction box located on top of the water heater. If the black
lead wire is used make the connection inside of the junction box with a properly sized wire nut. See
"Junction Box Assembly" Figure on next page and "Wiring Diagrams" on Page 52 and Page 53.
Note: If electrical connection is made directly to terminal block remove black lead wire before making
connection.
4. Connect the 120 VAC white (neutral) wire from the power supply to the white lead wire or the
terminal block location marked "Neutral" inside of the junction box located on top of the water
heater. If the white lead wire is used, make the connection inside of the junction box with a properly
sized wire nut. See "Junction Box Assembly" Figure on next Page and "Wiring Diagrams" on Page
52 & Page 53.
Note: If electrical connection is made directly to terminal block remove white lead wire before making
connection.
Servicing should only be performed by a Qualified Service Technician
35
5. Connect the ground wire from the power supply to the grounding lug inside the junction box. See
Junction Box Assembly Figure below and "Wiring Diagrams" on Page 52 & Page 53.
6. Replace junction box cover when connections are complete.
Note: Do not apply power to the water heater before installation is complete and the water heater is filled
with water.
Ground Terminal
Heater Wiring
(Factory Installed)
Lead Wire
Ground
L1 (Black Wire)
Neutral (White Wire)
Junction Box Assembly
ENABLE/ DISABLE SWITCH
Enable/ Disable Switch
The Enable/Disable Switch is NOT an "on/off" switch and does not disconnect 120 volt power to the CCB and
other heater components. When in the "Disabled" position the switch removes electrical power from the Gas
Control 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". The Enable/Disable Switch can be used to
disable operation and reset error codes. To operate the water heater, make sure the switch is set to "Enabled"
position. Turn power off at the source (circuit breaker) during installation and servicing.
POWER SUPPLY TEST
Proper grounding and polarity can be verified with an AC volt meter by taking three voltage readings at the
power supply wiring inside the water heater's 120 VAC junction box.
Check for AC voltage between:
1. Hot & Neutral - should be approximately 120 VAC.
2. Hot & Ground - should be approximately 120 VAC.
3. Neutral & Ground - should be approximately 0 VAC.
36
Servicing should only be performed by a Qualified Service Technician
INSTALLATION CHECK LIST
The list below represents some of the most critical installation requirements that, when overlooked, often result
in operational problems, down time and needless parts replacement. Before performing any troubleshooting
procedures use the list below to check for installation errors. 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 observed and followed.
See "Fault And Warning Codes" beginning on Page 7 for service procedures relating to the fault conditions
mentioned below.
1. The vent (exhaust) pipe must not be combined or connected to any other appliance’s vent system or
chimney.
2. The intake air pipe must not be combined or connected to any other appliance’s intake air piping.
3. The water heaters covered in this Service Handbook are condensing appliances. Condensate will form
in the vent pipe during normal operation, condensate can also form in the intake air piping in certain
circumstances. Ensure the intake air and/or vent piping is not installed in a manner that will allow water
to be trapped in the piping. Install a condensate tee in the intake air and/or vent piping. Condensate
trapped in the intake air and/ or vent piping will lead to Blocked Exhaust and/or Blocked Air Intake fault
conditions and Control System lock outs.
4. Ensure the intake air and/or vent piping is the correct size for the installed length. See the venting
requirements section in the Instruction Manual that came with the water heater. Using smaller pipe than
is required will lead to Blocked Exhaust and/or Blocked Air Intake fault conditions and Control System
lock outs.
5. Ensure the intake air and/or vent piping are within the maximum equivalent lengths required in the
Instruction Manual that came with the water heater. Exceeding the maximum length or number of elbows
allowed will also lead to Blocked Exhaust and/or Blocked Air Intake fault conditions and Control System
lock outs.
6. The metal condensate elbow supplied with the water heater has a built in water trap; thus it is not
necessary to form another water trap. Condensate drain blockage will cause the exhaust elbow to fill with
water and lead to Blocked Exhaust fault conditions and Control System lock outs.
7. Ensure the vent and intake air terminations have adequate clearances from each other and the terminations
of other appliances. Failure to maintain adequate clearances can cause the recirculation of flue gases
between the vent and intake air piping. Recirculation of flue gases will cause poor combustion, sooting,
ignition failure, rough starts, rough operation, premature failure of the heat exchanger and icing of the
combustion air intake during severe cold weather.
8. Direct vent terminations being installed in dead air spaces such as alleys, atriums, and inside corners
can also cause the recirculation of flue gases between the vent and intake air piping. To prevent the
recirculation of flue gases, maintain as much distance as possible between the intake air and vent
terminations.
9. Ensure the screens in the factory supplied terminations are securely installed to prevent blockage in the
intake air and/or vent piping.
10.On Direct Vent installations ensure the screen at the intake air connection on the water heater was
removed before the intake air piping was connected, see "Intake Air Connection" on Page 34.
11.Ensure the water heater is properly grounded. The water heater Control System requires an adequate
earth ground for flame sensing (verification), see "Flame Sensing Operation" on Page 24. Inadequate
grounding to the water heater and/or the Burner will cause the Ignition Failure fault condition and Control
System lock out. See "Electrical Connections" section on Page 35.
Servicing should only be performed by a Qualified Service Technician
37
OPERATION AND SERVICE
HOW IT WORKS
This section of the Service Handbook will cover operation, common service procedures and water heater
construction. The water heater covered in this Service Handbook has a helical shaped coil heat exchanger
that is submerged in the storage tank. These water heaters use a top mounted down fired radial design
Burner. This is a forced draft burner; hot burning gases are forced through the heat exchanger under pressure
and exit through the exhaust/vent connection located at the bottom of the water heater.
Starting at the top air and fuel gas are drawn in by the Combustion Blower and Venturi. Flue gases and are
forced through the helical shaped heat exchanger by the Combustion Blower and out through the exhaust/
vent outlet.
COMBUSTION BLOWER
The Combustion Blower is an assembly that includes the blower housing, blower motor and an electronic
speed control. The Combustion Blower is controlled by the CCB (Central Control Board) and is powered by
a 3 pin wiring plug receiving 120 VAC from the Junction Box.
The CCB sends a signal from the J5 socket to a 5 pin wiring socket on the SUF 60120 - 100250 blower and
VFD on the SUF 119300 - 119500 top cover control assembly. The signal is an electronic instruction to start,
stop and control blower speed.
The Combustion Blower runs at higher speeds during the Pre/Post Purge operating states and runs at a
lower speed during the Trial For Ignition operating state. The Igniter Status icon is displayed on the UIM
during the Trial For Ignition operating state.
MODULATION
The water heaters covered by this Service Handbook are capable of modulating their firing rate. The CCB
monitors the water temperature in the tank and regulates the firing rate to achieve the target temperature
setpoint. The firing rate is dictated by the hot water draw, proximity to the tank temperature setpoint, and
various other temperature limitations. Periodically, when the heater is in modulation mode, the CCB will
increase the blower speed for a short period of time to clear out any condensation that may have accumulated
in the heat exchanger then decreases the blower speed back to the modulating firing rate required to maintain
the desired tank temperature setpoint. This ramping up and down of the blower speed is considered normal
operation of the water heater.
38
Servicing should only be performed by a Qualified Service Technician
Service Note:
The 5 pin PWM signal plug MUST remain plugged in to the 5 pin socket on the blower assembly at all times
(SUF 60120 - 100250 Models only). Disconnecting this plug will cause the Combustion Blower to stop. If the
electronic speed control is functioning properly Combustion Blower speed should noticeably reduce during
the Trial For Ignition operating state. If blower speed reduction does not occur during the Trial For Ignition
operating state ensure the 5 pin plug from the CCB is securely plugged into the matching 5 pin socket on
the blower assembly and that the J5 plug is securely plugged into the J5 socket on the CCB circuit board.
Perform a close visual inspection of the pins inside the plugs and sockets at the Combustion Blower and the
CCB, replace any worn or damaged wiring harnesses as necessary.
COMBUSTION BLOWER ASSEMBLY (SUF 60120 - 100250 MODELS)
BLOWER
HOUSING
5 PIN
WIRING
SOCKET
BLOWER MOTOR
AND ELECTRONIC
SPEED CONTROL
3 PIN
WIRING
SOCKET
Servicing should only be performed by a Qualified Service Technician
39
BLOWER SPEED CONTROL – SUF 119300 THRU 119500
The CCB monitors a feedback signal from a sensor that is installed on the blower. The CCB interprets the
pulse signal from the sensor and then sends a signal to the variable frequency drive (VFD) which in turn
transmits the proper frequency to the blower to produce the proper blower speed and input. Refer to the
Variable Frequency Drive on next page for its operation.
Below is a chart for the blower rpms and corresponding VFD Hertz Readings for those rpms displayed on
the VFD.
Note: These models are capable of modulating their input rate. Therefore, the RPM readings can be in
between the Heating Speed and Minimum Modulation Speed RPMs. The input rate should be verified
with the water heater operating at full input rate.
40
Model
Heating
Speed
RPM
SUF 119300 Nat
SUF 119300 LP
SUF 119400 Nat
SUF 119400 LP
SUF 119500 Nat
SUF 119500 LP
3450
3200
4625
4200
5750
5225
Heating
Speed
VFD Hertz
Reading
117.4
108.8
158.3
143.2
198.2
179.8
Minimum
Minimum
Modulation Modulation
RPM
VFD Hertz
Reading
2350
79.7
2310
78.5
2350
79.7
2310
78.5
2350
79.7
2310
78.6
Ignition
Speed
RPM
Servicing should only be performed by a Qualified Service Technician
4500
5770
4500
5770
4500
5770
Ignition
Speed
VFD Hertz
Reading
153.8
198.2
153.8
198.2
153.8
198.2
VARIABLE FREQUENCY DRIVE – SUF 119300 THRU 119500
The SUF 119300 - 119500 models have a variable frequency drive (VFD) that controls the rpm of the
blower motor. The VFD receives a signal from the central control board that instructs the VFD to transmit
the proper frequency to the blower to produce the proper blower speed and proper input.
Three conditions must be met for the frequency drive to start the blower:
1. 120VAC must be supplied to the VFD 120VAC input.
2. The ignition control board closes an enable circuit – terminals LI1 and +24V
3. The ignition control board sends a 1-10VDC instruction – terminals 0V and AI1.
VFD Display
VFD (Variable Frequency Drive)
Servicing should only be performed by a Qualified Service Technician
41
BURNER ASSEMBLY
The Burner is a radial design burner with a steel fiber jacket on the outer surface and is part of a larger Burner
Assembly. Figures below show side views of the complete Burner Assembly removed from the water heater
with key components identified. See the exploded view of the "Combustion Blower & Burner Assembly"
section on Page 4 also.
SUF 60120 - 100250 Models
SUF 119300 - 119500 Models
42
Servicing should only be performed by a Qualified Service Technician
COMBUSTION BLOWER AND BURNER REMOVAL/ INSTALLATION
INSTRUCTIONS
Refer to the Combustion Blower & Burner Assembly, Heater Top View images in this Service Handbook and
the Instruction Manual supplied with the heater for heater component locations.
COMBUSTION BLOWER/ BURNER REMOVAL
1. Turn the water heater’s Enable/Disable switch to the “Disable” Position.
2. Turn off the electrical circuit breaker that serves the water heater.
3. Close the Main Gas Shut Off Valve serving the water heater.
4. Disconnect the supply gas line to the water heater on the heater side of the Main Gas Shut Off Valve.
5. If the water heater has been installed in a Direct Vent configuration, disconnect the Blocked Air Intake
Switch sensing tube (light blue soft tubing) from the Air Intake Pipe Assembly and disconnect the intake
air pipe at the intake air connection on the water heater by loosening the hose clamp closest to the
Venturi and remove the Intake Air Assembly.
6. If the water heater has been installed in a Non-Direct Vent configuration, disconnect the Blocked Air
Intake Switch sensing tube (light blue soft tubing) from the Air Intake Pipe Assembly and disconnect the
intake air pipe at the intake air connection on the water heater by loosening the hose clamp closest to the
Venturi and remove the Intake Air Assembly.
7. Unplug the ignition cable from the spark igniter and the yellow wire from the Flame Sensor.
8. SUF 60120 - 100250 Models: Disconnect the 3-Pin and 5-Pin plugs from the Combustion Blower
Assembly. SUF 119300 - SUF 119500 Models: Disconnect the blower power wires at the three spade
connectors connecting the blower to the VFD and unplug the blower speed feedback connector from the
wiring harness.
9. Disconnect the 24 Volt power wires to the Gas Control Valve at the two spade connectors in the wiring
harness to the valve.
10.Disconnect the Blower Prover Switch sensing tube (light blue soft tubing) from the Combustion Blower
outlet sensing port.
11.Using a socket wrench with a ½” deep well socket remove the four (SUF 60120), six (SUF 100150 100250), or eight (SUF 119300 - 119500) ½” nuts from the studs holding the burner plate in place.
12.Slide the three burner ground wire eyelet connectors up and off of the studs.
Note: These ground wires must be reinstalled when reinstalling the Burner Assembly.
13.Ensure there are not any loose parts, tools, screws, or objects of any kind on top of the water heater
before removing the Burner Assembly as these objects could fall into the heat exchanger.
14.Carefully lift the Burner Assembly straight up and out of the heater exchanger opening.
15.Refer to the Flame Sensor and Spark Igniter sections of this Service Handbook for their servicing
specifications.
COMBUSTION BLOWER/ BURNER INSTALLATION
1. Install new white fiber Burner Plate (All Models) and Flue Ring (SUF 60120 - 100250 Models) before reinstalling the Blower/Burner Assembly.
2. To re-install the Burner Assembly follow the steps for removal in reverse order.
3. Do not overtighten the ½” nuts.
4. Connect the supply gas line to the water heater on the heater side of the Main Gas Shut Off Valve.
5. Slowly open the Main Gas Shut Off Valve serving the water heater.
6. Turn on the electrical circuit breaker that serves the water heater.
7. Turn the water heater’s Enable/Disable switch to the “Enable” Position.
8. Operate heater through at least one complete heating cycle to verify it is operating properly.
Servicing should only be performed by a Qualified Service Technician
43
SPARK IGNITER
The water heaters covered in this Service Handbook use a Spark Igniter. The Spark Igniter has two rods: the
sparking rod that has ceramic insulation and the grounding rod, see Figure below. During trial for ignition,
the Control System powers a high voltage transformer (Ignition Control) from J6, and the Ignition Control
supplies high voltage to the sparking rod via the ignition cable. The high voltage potential across the gap
between the sparking rod and the grounding rod generate a spark.
Spark Igniter (1/8"
Spark Gap)
Spark Igniter
(5/16" Gap from
Burner)
Flame Sensor
(1/2" Gap from
Burner)
SUF 60120 - 100250 Models
44
Servicing should only be performed by a Qualified Service Technician
Spark Igniter (1/8"
Spark Gap)
Spark Igniter
(5/16" Gap from
Burner)
Flame Sensor
(13/16" Gap from
Burner at the tip
of Sensor Rod)
SUF 119300 - 119500 Models
The Control System is programmed to start sparking a few seconds before the Gas Control Valve opens. See
the "Sequence Of Operation Flow Chart" on Page 6.
Service Notes:
• The animated lighting bolt Status Icon is visible on the UIM. See "(UIM) User Interface Module Screen"
Figure on Page 54.
• Ensure the wiring and connections between the J6 Socket on the CCB and the Burner Adapter are not
broken, pinched or disconnected.
• Ensure there is approximately 120 VAC at the J6 Socket on the CCB.
• It is a good practice to check for any crack or damage to the ceramic insulator. If any crack is found,
replace the Spark Igniter. Do not contaminate the ceramic insulator as this could make a shortage pass
between the spark rod and grounding rod. Ensure good connection between the ignition cable and
Spark Igniter.
Servicing should only be performed by a Qualified Service Technician
45
GAS ORIFICE - SUF 119300 THRU 119500 MODELS
Refer to Orifice Chart below for correct gas orifice size. SUF 60120 thru 100250 Models and all Natural gas
models do not use a gas orifice.
w/LP Gas Orifice
Without Orifice
Gas Control Without Orifice Natural Gas
Gas Control With Orifice Propane (LP)
SUF 119300 - 119500 Models
ORIFICE CHART - SUF 119300 THRU 119500 MODELS
46
Models
119300
119400
119500
Natural
Propane (LP)
N/A
0.344"
N/A
0.344"
N/A
0.344"
Servicing should only be performed by a Qualified Service Technician
CCB (CENTRAL CONTROL BOARD)
The CCB is a printed circuit board mounted inside a protective plastic enclosure, see Figures below and on
next page. The CCB circuit board is the main control. All instructions for ignition and temperature control
originate from this circuit board. Diagnostic and operational messages are generated by the CCB and sent
to the UIM, see "(UIM) User Interface Module Screen" on Page 54.
Most of the water heater’s components, such as the Spark Igniter, Combustion Blower, 24 Volt Gas Control
Valve, and Temperature Probe are directly connected to one of the CCB’s socket connectors.
Power Supply Board
CCB Circuit Board
120 VAC X 24 VAC, 50 VA Transformer
Power Supply Board
Temperature Probe Connectors
Front Cover On
Power Transformer
CCB Circuit Board
Molded Clips
Front Cover Removed
Servicing should only be performed by a Qualified Service Technician
47
CCB COVER REMOVAL AND REPLACEMENT
The cover on the CCB enclosure must be removed for various service procedures outlined in this Service
Handbook. Refer to the instructions below when removing and replacing the CCB cover.
Wiring to and from the CCB and other water heater components enters the CCB enclosure on the bottom.
Removing the enclosure cover is a simple procedure. Care must be taken when replacing the CCB cover
to ensure the wiring is routed properly and the cover is replaced correctly. Follow the procedures below to
ensure the wiring is not pinched or damaged and no connectors are accidentally unplugged.
Cover Removal Procedure:
Refer to "CCB" section on Page 47 for these instructions.
1. Ensure power to the water heater is turned off.
2. Remove the upper and lower temperature probe connectors.
3. Unlock clips on both sides and remove the cover.
Cover Replacement Procedure:
1. Follow Cover Removal Procedure in reverse order to replace cover.
Service Notes:
If any operational problems, fault conditions or Control System lock outs occur after the CCB enclosure
cover has been removed and replaced, remove the cover again to ensure none of the wiring connectors are
unplugged and/or any of the wiring has been pinched, cut or damaged. Unlike previous water heaters in this
product line, the individual control boards inside the plastic enclosure are serviceable parts. See the Parts
List that was shipped with the water heater for the appropriate part numbers for each component.
48
Servicing should only be performed by a Qualified Service Technician
2
3
2
1
J12
4
3
2
1
1
2
3
J10
3
1
2
2
1
6 J1
4
J6
9
2 J15
4
7
1
3
4
8
1
2
3
J14
4
5
6
7
8
9
10
11
12
3
4
J9
J5 4 3 2 1
5 4 3 2 1
3 2 1
6 5 4 J16
8 7 6 5
J13
J3
8
1
1
1
4
3
2
6
5
J4
J17
6
5
4
CCB CIRCUIT BOARD LAYOUT
CCB (CENTRAL CONTROL BOARD)
POWER BOARD ASSEMBLY
Servicing should only be performed by a Qualified Service Technician
49
CCB CONNECTION IDENTIFICATION
J1 Socket - High Voltage In
PIN #
1
2
3
4
5
6
7
8
9
DESCRIPTION
Ground
AUX NC
AUX NO
AUX Common
Not Used
AUX NO
AUX Common
Line Voltage
Neutral
J5 Socket - Blower Logic (VFD/ Blower)
PIN #
1
2
3
4
5
DESCRIPTION
24V
PWM Signal
Not used
Blower Speed Feedback
Grounding
J6 Socket - 120V Out
PIN #
1
2
DESCRIPTION
Neutral
Line Voltage Out
J9 Socket - Temperature Probe
PIN #
1
2
3
4
DESCRIPTION
ECO
Thermistor
Thermistor
ECO
J12 Socket - Configuration Key
J13 Socket - Display/ AIN
50
Servicing should only be performed by a Qualified Service Technician
J14 Socket - Limit String
PIN #
1
2
3
4
5
6
7
8
9
10
11
12
DESCRIPTION
Anode
Grounding
Flame Sensor
Condensate
Not Used
Condensate
Gas Pressure Switch
Gas Pressure Switch
Gas Control Valve
Gas Control Valve
24V
24V Return
J15 Socket - Pressure Switches
PIN #
1
2
3
4
DESCRIPTION
Blower Prover Pressure Switch / Blocked Air Intake Pressure Switch
Blocked Air Intake Pressure Switch / Blocked Exhaust Pressure Switch
Blower Prover Pressure Switch
Blocked Exhaust Pressure Switch
J16 Socket - Low Voltage In
PIN #
1
2
3
4
5
6
DESCRIPTION
24V AC
24V AC
Not Used
12V DC
5V DC
Grounding
Servicing should only be performed by a Qualified Service Technician
51
WIRING DIAGRAM – SUF 60120 THRU 100250
52
Servicing should only be performed by a Qualified Service Technician
WIRING DIAGRAM – SUF 119300 THRU 119500
Servicing should only be performed by a Qualified Service Technician
53
CONTROL OVERVIEW
Interaction with the water heater controller is through an UIM display called the User Interface Module
(UIM). This screen is also referred to as the “desktop” or “desktop menu”. Up and down buttons and
three operation buttons allow navigation through the control menus and to make adjustments to the water
heater. Operation of the three lower buttons is defined immediately above them on the screen.
While the water heater is operating, the user interface will display the UIM screen (if there are no active
faults or warnings).
An example of this screen is shown below.
•
The first temperature on this screen is the temperature of the water inside the tank.
•
The second temperature on this screen is the Operating Set Point. The Operating Set Point is the
temperature at which the water heater will maintain the water inside the tank.
•
The third line on the screen is a text description of the Operational State of the water heater. The
operational state of the water heater is also indicated graphically by status icons.
UIM (User Interface Module)
LCD Screen
Information
Display
Status Icons
Title Bar
MANUFACTURER / MODEL INFORMATION
Tank Temperature
Operating Set Point
103°F
120°F
Status: Heating
OFF
DN
GAS O
N
MENU
UP
HELP
Operational buttons are multi functional. Their current function is defined by
the text that appears directly above each button on the LCD screen.
Up & Down buttons:
navigate menus,
adjust user settings
3 Operational buttons:
enter/exit menus,
select menu items,
activate adjustment modes,
confirm/cancel changes.
(UIM) User Interface Module Screen
54
Servicing should only be performed by a Qualified Service Technician
COMMERCIAL GAS HIGH EFFICIENCY WATER HEATERS
Visit the "Information Central" link of
www.statewaterheaters.com for a listing of available Service Handbooks.
For additional information contact:
State Water Heaters
500 Tennessee Waltz Parkway
Ashland City, TN 37015
1-800-527-1953
www.statewaterheaters.com
©2014 State Industries, Inc.
329298-000