A.O. Smith BTR 120-400 How to use

COMMERCIAL GAS HIGH EFFICIENCY WATER HEATERS
Service Handbook
PRINTED IN THE U.S.A. 1016 100277701_2000536453_Rev A
500 Tennessee Waltz Parkway
Ashland City, TN 37015
FOR MODELS:
BTR 120 thru 400(A) Series 118 & 119
INSTALLATION CONSIDERATIONS - PRE SERVICE CHECKS -
CONSTRUCTION - OPERATION & SERVICE - TROUBLESHOOTING
SERVICING SHOULD ONLY BE PERFORMED BY A QUALIFIED SERVICE TECHNICIAN

1
TABLE OF CONTENTS
INTRODUCTION.......................................................................................2
Qualications................................................................................2
Service Warning...........................................................................2
Service Reminder.........................................................................2
Tools Recommended ...................................................................2
INSTALLATION CONSIDERATIONS.......................................................3
Instruction Manual........................................................................3
Closed Water Systems.................................................................3
Thermal Expansion ......................................................................3
Air Requirements .........................................................................3
Contaminated Air..........................................................................3
VENTING.................................................................................................4
Power Vent Kits For Sidewall Venting...........................................5
GAS CONTROL VALVE...........................................................................6
GAS SUPPLY SYSTEMS.........................................................................7
Supply Gas Regulator ..................................................................7
Gas Piping....................................................................................8
FEATURES AND COMPONENTS ..........................................................10
The Eliminator (Self-Cleaning System) ........................................10
Automatic Flue Damper ...............................................................10
Uncrating......................................................................................10
White Rodgers Integrated Temperature Control-High Limit Switch
......................................................................................................11
Electronic Ignition Control/ Ignition Module..................................12
SEQUENCE OF OPERATION FLOW CHART........................................13
FAULT AND WARNING CODES .............................................................14
Ignition Module.............................................................................14
Flue Damper ................................................................................14
Diagnostics Codes – Ignition Module (BTR 118/119 Series)........15
TROUBLESHOOTING CHECKLIST .......................................................17
GENERAL SERVICE CHART .................................................................18
FAULT AND WARNING CODES - CONTINUED.....................................19
Step 1. Troubleshooting The BTR Water Heaters........................19
EFFIKAL RVGP-KSF-Series Flue Damper Troubleshooting Guide
......................................................................................................21
Step 2: Test For 24Vac Between Black And Orange On Damper PC
Board............................................................................................22
Step 3: Adjust End Switch To Cam Contact ................................. 22
Step 4: Test For 24VAC Between Black And Yellow On Damper PC
Board............................................................................................23
Step 5: Wire Harness Test ...........................................................23
Step 6: IID Module Test (Power To The Pilot Valve)..................... 24
Step 7: Pilot Spark Test................................................................25
Step 8: Flame Rectication ..........................................................26
Step 9: IID Module Test................................................................27
Step 10: Main Burner Test............................................................ 28
WIRING DIAGRAM - BTR 118/119 SERIES ...........................................29
WIRING DIAGRAM - BTR 118/119 SERIES CONTROLS ......................30
NOTES ....................................................................................................31

2Servicing should only be performed by a Qualied Service Technician
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 Qualied Agency (as dened
by ANSI below) in the eld involved. Installation skills such as plumbing, air supply, venting, gas supply and
electrical supply are required in addition to electrical testing skills when performing service.
ANSI Z223.1 2006 Sec. 3.3.83: “Qualied Agency” - “Any individual, rm, corporation or company that either
in person or through a representative is engaged in and is responsible for (a) the installation, testing or
replacement of gas piping or (b) the connection, installation, testing, repair or servicing of appliances and
equipment; that is experienced in such work; that is familiar with all precautions required; and that has
complied with all the requirements of the authority having jurisdiction.”
SERVICE WARNING
If you are not qualied (as dened by ANSI above) and licensed or certied as required by the authority
having jurisdiction to perform a given task do not attempt to perform any of the procedures described in this
service handbook. If you do not understand the instructions given in this service handbook do not attempt to
perform any procedures outlined in this service handbook.
SERVICE REMINDER
When performing any troubleshooting step outlined in this service handbook always consider the wiring
and connectors between components. Perform a close visual inspection of all wiring and connectors to and
from a given component before replacement. Ensure wires were stripped before being crimped in a wire
connector, ensure wires are crimped tightly in their connectors, ensure connection pins in sockets and plugs
are not damaged or worn, ensure plugs and sockets are mating properly and providing good contact.
Failure to perform this critical step or failing to perform this step thoroughly often results in needless down
time, unnecessary parts replacement, and customer dissatisfaction.
TOOLS RECOMMENDED
• Instruction Manual that came with the water heater.
• All tools common to installation and service of commercial water heaters such as hand tools, screwdrivers,
pipe wrenches etc.
• Hex (Allen) wrench sizes: 5/32”, 1/8”, 1/4” and 5/16"
• Digital manometer: Range -20.00 to +20.00" W.C. Resolution - 0.01" W.C. Required to test supply gas
pressure.
• Digital Multi Meter; capable of measuring:
• AC/DC Voltage.
• Ohms.
• DC micro amps (μA).

3
Servicing should only be performed by a Qualied 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 ow preventers.
Devices such as these cause the water system to be a closed system.
THERMAL EXPANSION
As water is heated, it expands (thermal expansion). 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 can
cause recirculation of combustion products resulting in contamination that may be hazardous to life. Such
a condition often will result in a yellow, luminous burner ame, causing sooting of the combustion chamber,
burners and ue tubes and creates a risk of asphyxiation.
CONTAMINATED AIR
Combustion air that is contaminated can greatly diminish the life span of the water heater and water heater
components such as hot surface 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.
Do not store products of this sort near the water heater. Air which is brought in contact with the water heater
should not contain any of these chemicals. If necessary, uncontaminated air should be obtained from remote
or outdoor sources.

4Servicing should only be performed by a Qualied 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.
The instructions in this section on venting must be followed to avoid choked combustion or recirculation of
ue gases. Such conditions cause sooting or risks of re and asphyxiation.
Heater must be protected from freezing downdrafts. Remove all soot or other obstructions from the chimney
that will retard a free draft.
Type B venting is recommended with these heaters. For typical venting application refer to Technical Data
Venting in the Instruction Manual. This water heater must be vented in compliance with all local codes, the
current revision of the National Fuel Gas Code (ANSI-Z223.1) and with the Category I Venting Tables.
If any part of the vent system is exposed to ambient temperatures below 40°F it must be insulated to prevent
condensation.
• Do not connect the heater to a common vent or chimney with solid fuel burning equipment. This practice
is prohibited by many local building codes as is the practice of venting gas red equipment to the duct
work of ventilation systems.
• Where a separate vent connection is not available and the vent pipe from the heater must be connected
to a common vent with an oil burning furnace, the vent pipe should enter the smaller common vent or
chimney at a point above the large vent pipe.
All BTR water heaters are classied by ANSI as category I (non-condensing, negative pressure venting)
appliances. They are approved for Type B venting. For larger applications, BTR water heaters can be
common vented together either in a tapered manifold or constant size manifold. (Follow National Fuel Gas
Code requirements for sizing and installation.) BTRs may be common vented only with other category I
appliances. (See venting section in the National Fuel Gas Code).

5
Servicing should only be performed by a Qualied Service Technician
POWER VENT KITS FOR SIDEWALL VENTING
BTR water heaters can be used with power
vent kits for sidewall venting. A. O. Smith
offers power vent kits for use on installations
with a maximum of 100 equivalent feet
of vent piping. The power vent kits also
use type B vent materials. When power
venting, specic exterior clearances must be
maintained, as outlined in the National Fuel
Gas Code. (NFPA 54, ANSI A223.1, sec 7.8)

6Servicing should only be performed by a Qualied Service Technician
GAS SUPPLY SYSTEMS
Low pressure building gas supply systems are dened as those systems that cannot under any circumstances
exceed 14” W.C. (1/2 PSI Gauge). These systems do not require 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 supply pressure must be stable
within 1.5” W.C. from static to dynamic pressure to provide good performance. 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 valves. If
your low pressure system does NOT meet these requirements, the installer is responsible for the corrections.
High Pressure building supply systems use pressures that exceed 14” W.C. (1/2 PSI Gauge). These systems
must use eld supplied regulators to lower the gas pressure to less than 14” W.C. (1/2 PSI Gauge). Water
heaters require gas regulators that are properly sized for the water heater input and deliver the rating plate
specied pressures. Gas supply systems where pressure exceeds 5 PSI often require multiple regulators to
achieve desired pressures. Systems in excess of 5 PSI building pressure should be designed by gas delivery
professionals for best performance. Water heaters connected to gas supply systems that exceed 14” W.C.
(1/2 PSI Gauge) at any time must be equipped with a gas supply regulator.
All models require a minimum gas supply pressure of 4.5" W.C. for natural gas and 11.0" W.C. for propane
gas. The minimum supply pressure is measured while gas is owing (dynamic pressure). The supply pressure
should never fall below 4.5" W.C. for natural gas and 11.0" W.C. for propane gas. The supply pressure
should be measured with all gas red appliances connected to the common main ring at full capacity. If
the supply pressure drops more than 1.5” W.C. as gas begins to ow to the water heater then the supply
gas system including the gas line and/or the gas regulator may be restricted or undersized. See Supply Gas
Regulator section and Gas Piping section of this manual. The gas valve on all models has a maximum gas
supply pressure limit of 14” W.C. The maximum supply pressure is measured while gas is not owing (static
pressure).
SUPPLY GAS REGULATOR
The maximum allowable gas supply pressure for this water heater is 14 inches W.C. (3.48 kPa). Install a
positive lock-up gas pressure regulator in the gas supply line if inlet gas pressure can exceed 14 inches W.C.
(3.48 kPa) at any time. Regulators must be sized/used according to manufacturer’s specications.
If a positive lock-up regulator is required follow these instructions:
1. Positive lock-up gas pressure regulators must be rated at or above the input Btu/hr rating of the water
heater they supply.
2. Positive lock-up gas pressure regulator(s) should be installed no closer than 3 equivalent feet (1 meter)
and no farther than 8 equivalent feet (2.4 meters) from water heater’s inlet gas connection.
3. After installing the positive lock-up gas pressure regulator(s) an initial nominal supply pressure setting
of 7.0” W.C. while the water heater is operating is recommended and will generally provide good water
heater operation. Some addition adjustment maybe required later to maintain a steady gas supply
pressure.
4. 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.

7
Servicing should only be performed by a Qualied Service Technician
GAS PIPING
Contact your local gas service company to ensure that adequate gas service is available and to review
applicable installation codes for your area.
Size the main gas line in accordance with Table below. The gures shown are for straight lengths of pipe
at 0.5 in. W.C. pressure drop, which is considered normal for low pressure systems. Note: Fittings such as
elbows, tees and line regulators will add to the pipe pressure drop. Also refer to the latest version of the
National Fuel Gas Code.
Schedule 40 Steel or Wrought Iron Pipe is the preferred material for the gas line of this water heater. It
is imperative to follow the sizing recommendations in the latest version of the National Fuel Gas Code if
Corrugated Stainless Steel Tubing (CSST) is used as the gas line for this water heater.
The heater is not intended for operation at higher than 14.0" W.C.- natural gas, (1/2 pound per square inch
gage) supply gas pressure. Exposure to higher supply pressure may cause damage to the gas valve which
could result in re or explosion. If overpressure has occurred such as through improper testing of gas lines or
emergency malfunction of the supply system, the gas valve must be checked for safe operation. Make sure
that the outside vents on the supply regulators and the safety vent valves are protected against blockage.
These are parts of the gas supply system, not the heater. Vent blockage may occur during ice storms.
GAS SUPPLY PIPE LENGTHS (IN FEET)
Maximum Equivalent Pipe Length - Natural Gas Only
Input rate
(BTU/HR)
Schedule 40 Steel or Wrought Iron Pipe
1/2" 3/4" 1" 1 1/4" 1 1/2"
120,000 20 70 200 200 200
154,000 10 40 150 200 200
180,000 -30 100 200 200
199,000 - 30 90 200 200
250,000 -20 60 200 200
275,000 -10 50 200 200
310,000 -10 40 150 200
366,000 - - 30 100 200
390,000 - - 20 100 200
Fitting Type* Equivalent length in feet
45°Ell 0.7 1.0 1.2 1.6 1.9
90°Ell 1.6 2.1 2.6 3.5 4.0
Tee 3.1 4.1 5.2 6.9 8.0
Natural Gas 0.60 Specic Gravity, 0.50" W.C. Pressure Drop
*Screwed Fittings
It is important to guard against gas valve fouling from contaminants in gas ways. Such fouling may cause
improper operation, re or explosion.
If copper supply lines are used they must be internally tinned and certied for gas service. Before attaching
the gas line, be sure that all gas pipe is clean on the inside. The instructions in this section on venting must
be followed to avoid choked combustion or recirculation of ue gases. Such conditions cause sooting or risks
of re and asphyxiation.

8Servicing should only be performed by a Qualied Service Technician
To trap any dirt or foreign material in the gas supply line, a sediment trap must be incorporated in the piping
(see Figure below). The sediment trap must be readily accessible and not subject to freezing conditions.
Install in accordance with recommendations of serving gas suppliers. Refer to the latest version of the
National Fuel Gas Code.
To prevent damage, care must be taken not to apply too much torque when attaching gas supply pipe to
gas valve inlet. Apply joint compounds (pipe dope) sparingly and only to the male threads of pipe joints. Do
not apply compounds to the rst two threads. Use compounds resistant to the action of liqueed petroleum
gases.
Be sure the gas meter has sufcient capacity to supply the full rated gas input of the water heater as well as
the requirements of all other gas red equipment supplied by the meter. If gas meter is too small, ask the gas
company to install a larger meter having adequate capacity.
GAS PIPING AND SEDIMENT TRAP INSTALLATION
Fire and Explosion Hazard
Leak test before placing the water
heater in operation.
Disconnect gas piping and main gas
shutoff valve before leak testing.
Install sediment trap in accordance
with NFPA 54.
Use joint compound or Teflon tape
compatible with propane gas.
Any time work is done on the gas supply system perform a leak test to avoid the possibility of re or explosion.
1. For test pressures exceeding 1/2 psi (3.45 kPa) disconnect the water heater and its Main Gas Shutoff
Valve from the gas supply piping system during testing, see Figure above. The gas supply line must be
capped when disconnected from the water heater.
2. For test pressures of 1/2 psi (3.45 kPa) or less, the water heater need not be disconnected, but must
be isolated from the supply gas line by closing the Main Gas Shutoff Valve during testing.
3. Coat all supply gas line joints and connections upstream of the water heater with a non-corrosive soap
and water solution to test for leaks. Bubbles indicate a gas leak. Do not use matches, candles, flame or
other sources of ignition for this purpose.
4. Repair any leaks before placing the water heater in operation.
PURGING
Gas line purging is required with new piping or systems in which air has entered.
Purging should be performed per the current edition of NFPA 54 the National Fuel Gas Code.

9
Servicing should only be performed by a Qualied Service Technician
FEATURES AND COMPONENTS
THE ELIMINATOR (SELF-CLEANING SYSTEM)
These units include The Eliminator (Self-Cleaning System) installed in the front water inlet. The Eliminator
inlet tube can only be used in the front water inlet connection. Do not install the Eliminator inlet tube in either
the top or back inlet water connection. The Eliminator must be oriented correctly for proper function. There
is a marked range on pipe nipple portion of the Eliminator, that must be aligned with top of inlet spud. A label
above the jacket hole has an arrow that will point to marked portion of pipe nipple if the orientation is correct.
If the arrow does not point within the marked range on pipe nipple, adjust the pipe nipple to correct. A pipe
union is supplied with the Eliminator to reduce probability of misaligning the Eliminator accidentally while
tightening the connection to inlet water supply line. Improper orientation of the Eliminator can cause poor
performance of heater and can signicantly reduce outlet water temperatures during heavy draws.
THE ELIMINATOR MAY HAVE 1, 3 OR 7 CROSS TUBES
AUTOMATIC FLUE DAMPER
All units are equipped with an automatic ue damper that reduces heat loss during the OFF cycles. The
automatic ue damper drive assembly is a eld replaceable part and may be obtained by contacting A. O.
Smith Corporation at 500 Tennessee Waltz Parkway, Ashland City, TN 37015, 1-800-433-2545. In Canada,
contact A. O. Smith Enterprises LTD., P.O. Box, 310 - 768 Erie Street, Stratford, Ontario, Canada N5A 6T3,
1-800-265-8520.
Each automatic ue damper drive assembly is equipped with a “Service Switch”, as shown in Figure below.
The “Service Switch” has 2 positions: AUTOMATIC OPERATION and HOLD OPEN DAMPER. For normal
operation the switch should be in the AUTOMATIC OPERATION position.
If there is a problem with the damper the “Service Switch” can be placed in the HOLD OPEN DAMPER
position. When the switch is placed in the HOLD OPEN DAMPER position the damper disc will rotate to
the open position and the heater may be used until vent assembly is repaired or replaced. DO NOT turn the
damper disc manually; damage will occur to the drive assembly if operated manually. Refer to TESTING
DAMPER OPERATION section of this manual for additional information.
FLUE DAMPER
UNCRATING
The heater is shipped with the ue damper already installed. The wiring conduit runs from the thermostat to
the damper drive cover. Before turning unit on, check to make sure the wiring conduit is securely plugged
into damper drive.