A.O. Smith GPDH User manual

1PART NO. 184707-001
GPDH/GPDT/GPDX
GAS MODELS
with
Hot Surface Ignition
CAUTION
TEXT PRINTED OR OUTLINED IN RED CONTAINS
INFORMATION RELATIVE TOYOUR SAFETY. PLEASE READ
THOROUGHLYBEFORE INSTALLING AND USING THIS
APPLIANCE.
KEEP THIS MANUALIN THE POCKET ON HEATER FOR FUTURE REFERENCE
WHENEVER MAINTENANCE ADJUSTMENT OR SERVICE IS REQUIRED.
PRINTEDINU.S.A. 0805
Thank you for buying this energy efficient water heater from
A.O. Smith Water Products Company. We appreciate your
confidence in our products.
You should thoroughly read this manual before installation and/
or operation of this water heater. Please pay particular attention
to the important safety and operating instructions as well as the
WARNINGS and CAUTIONS.
ADIVISION OFA.O.SMITHCORPORATION
www.aosmithwaterheaters.com
GET TO KNOW YOURWATER HEATER ......................2
GENERALSAFETYINFORMATION .............................3
INSTALLATION ....................................................... 3-11
LIGHTINGAND OPERATING LABEL.........................12
OPERATION .......................................................... 13-14
MAINTENANCEAND
TROUBLESHOOTING ........................................... 14-18
WARRANTY................................................................19
TABLE OF CONTENTS
PAGE
OWNER'S MANUAL
GAS WATER HEATER
RESIDENTIAL

2
GET TO KNOW YOUR WATER HEATER
REPLACEMENTPARTS AND DELIMINGPRODUCTS A VENTPIPE-EXHAUST
B ANODE
C HOTWATEROUTLET
D OUTLET(115 V.AC)
E FLUEBAFFLE
F GASSUPPLY
G MAINMANUAL GAS
SHUTOFF VALVE
H GROUNDJOINTUNION
J DIRTLEG
K OUTERDOOR
L UNION
M INLETWATERSHUT
OFF VALVE
N COLDWATERINLET
O INLETDIPTUBE
P TEMPERATUREAND
PRESSURERELIEFVALVE
Q RATINGPLATE
R INSULATION
S VENTTERMINALEXHAUST
T DRAIN VALVE
U HSIASSEMBLY
V FLUE
W DRAINPAN
X GAS VALVE
Y CONTROLHARNESS
Z INTAKEAIRPIPE
AA VENT TERMINAL INTAKE
BB INNER DOOR
CC BURNER ASSEMBLY
FIGURE1.
* CAUTION: 115VAC IN CONTROL
HARNESSANDINSIDEJACKET
GAS MODEL
GPDH/GPDT/GPDX
WITH HOT SURFACE IGNITION
CERTAIN MODELSAREEQUIPPED
WITH SIDE PLUMBING
CONNECTIONS FOR SPACE
HEATING. HOT AND COLD FITTING
ASSEMBLIESPARTNO. 900126-2.
TEMPERATURE INDICATORS
TEMPERATURE ADJUSTMENT BUTTONS
TYPICALNATURALGAS PILOT
& MAIN BURNER
HOTSURFACE
IGNITIONASSEMBLY
Replacement parts and recommended delimer may be
ordered through authorized servicers or distributors. Refer to
the Yellow Pages for where to call or contact the A.O. Smith
Water Products Company, 125 Southeast Parkway, Franklin,
TN 37068, 1-800-433-2545. When ordering parts, provide
complete model and serial numbers (see rating plate), quantity
and name or part desired (as listed in Figure 1). Standard
hardware items may be purchased locally.
CC
U
X
U

3
GENERAL SAFETY INFORMATION
EXTERNAL DAMAGE
Do not operate the water heater until it has been fully checked
out by a qualified technician, if the water heater:
• Has been exposed to fire or damage.
• Displays evidence of sooting.
• Produces steam or unusually hot water.
If the water heater has been flooded it must be replaced.
CHEMICAL VAPOR CORROSION
WARNING
CORROSION OF THE FLUEWAYS AND VENT SYSTEM MAY
OCCUR IF AIR FOR COMBUSTION CONTAINS CERTAIN
CHEMICALVAPORS WHICH WILL BREAK DOWN INTOACIDS
AT HIGH TEMPERATURE. SUCH CORROSION MAY RESULT
IN FAILURE AND RISK OF ASPHYXIATION.
Spray can propellants, cleaning solvents, refrigerator and air
conditioning refrigerants, swimming pool chemicals, calcium and
sodium chloride (water softener salt), waxes, and process
chemicals are typical compounds which are potentially corrosive.
Do not store products of this sort near the heater. Also, air which
is brought in contact with the heater should not contain any of
these chemicals. If necessary, uncontaminated air should be
obtained from remote or outside sources. The limited warranty
is voided when failure of water heater is due to a corrosive
atmosphere. (Refer to the limited warranty for complete terms
and conditions).
EXTENDED NON-USE PERIODS
WARNING
HYDROGEN GAS CAN BE PRODUCED IN A HOT WATER
SYSTEM SERVED BY THIS HEATER THAT HAS NOT BEEN
USED FOR A LONG PERIOD OF TIME (GENERALLY TWO
WEEKS OR MORE). HYDROGEN GAS IS EXTREMELY
FLAMMABLE. To reduce the risk of injury under theseconditions,
itis recommendedthat thehot water faucet be opened for several
minutes at the kitchen sink before using any electrical appliance
connected to the hot water system. If hydrogen is present, there
will probably be an unusual sound such as air escaping through
the pipe as the water begins to flow. THERE SHOULD BE NO
SMOKINGOR OPEN FLAME NEAR THE FAUCETATTHETIME
IT IS OPEN.
INSULATION BLANKETS
Insulation blankets available to the general public for external
use on gas water heaters are not necessary with A.O. Smith
products. The purpose of an insulation blanket is to reduce the
standby heat loss encountered with storage tank water heaters.
Your A. O. Smith water heater meets or exceeds the National
Appliance Energy Conservation Act standards with respect to
insulation and standby loss requirements, making an insulation
blanket unnecessary.
WARNING
Should you choose to apply an insulation blanket to this heater,
youshould follow these instructions, see Figure 1 for identification
of components mentioned below. Failure to follow these
instructions can restrict the air flow required for proper
combustion, potentially resulting in fire, asphyxiation, serious
personal injury or death.
•Do not cover the outer door, thermostat or temperature
& pressure relief valve.
•Do not cover the instruction manual. Keep it on the side of
the water heater or nearby for future reference.
•Doobtain newwarning and instruction labels from A.O. Smith
for placement on the blanket directly over the existing labels.
LIQUID PETROLEUM MODELS
WARNING
Water heaters for propane or liquefied petroleum gas (LPG) are
different from natural gas models. A natural gas heater will not
function safely on LP gas and no attempt should be made to
convert a heater from natural gas to LP gas.
LP gas must be used with great caution. It is highly explosive
and heavier than air. It collects first in the low areas making its
odor difficult to detect at nose level. If LP gas is present or even
suspected, do not attempt to find the cause yourself. Go to a
neighbor’s house, leaving your doors open to ventilate the house,
then call your gas supplier or service agent. Keep area clear
until a service call has been made.
At times you may not be able to smell an LP gas leak. One
cause is odor fade, which is a loss of the chemical odorant that
gives LP gas its distinctive smell. Another cause can be your
physical condition, such as having a cold or a diminishing sense
of smell with age. For these reasons, the use of a propane gas
detector is recommended.
IF YOU EXPERIENCEAN OUT-OF-GAS SITUATION, DO NOT
TRY TO RELIGHT APPLIANCES YOURSELF. Ask your
LP delivery person to relight pilots for you. Only trained LP
professionals should conduct the required safety checks in
accordance with industry standards.
INSTALLATION
REQUIRED ABILITY
INSTALLATION OR SERVICE OF THIS WATER HEATER
REQUIRES ABILITY EQUIVALENT TO THAT OF A LICENSED
TRADESMAN IN THE FIELD INVOLVED. PLUMBING, AIR
SUPPLY, VENTING AND GAS SUPPLY ARE REQUIRED.
GENERAL
The installation must conform to these instructions and the local
code authority having jurisdiction. In the absence of local codes,
the installation must comply with the current editions of the
National Fuel Gas Code,ANSI Z223.1/NFPA54 and the National
Electrical Code, NFPA 70. The former is available from the

4
Canadian Standards Association, 8501 East Pleasant Valley
Road, Cleveland, OH 44131, and both documents are available
from the National Fire Protection Association, 1 Batterymarch
Park, Quincy, MA02269.
The appliance, when installed, must be electrically grounded
in accordance with local codes or in the absence of local
codes with the current edition of the National Electrical Code,
ANSI/NFPA70.
LOCATION OF HEATER
The heater is design certified by the Canadian Standards
Association for installation with the following minimum clearances
between the water heater and combustible and non-
combustible construction are: 0 inches from side, 0 inches
from back, 6 inches (152 mm) from front of jacket to closet door
and 12 inches (30.5 cm) from top of jacket to combustible and
non-combustible material. Minimum vent clearance: 0 inches.
Provide 24 inches (61 cm) front clearance for servicing and
adequateclearancebetweenthe jacket topandceiling for servicing
the flue area. Also see clearance for venting on pages 6 & 7.
WARNING
FAILURE TO HAVE REQUIRED CLEARANCES BETWEEN
WATER HEATER AND COMBUSTIBLE MATERIAL WILL
RESULT IN A FIRE HAZARD.
Adequate clearance for servicing this appliance should be
considered before installation, such as changing the anodes, etc.
When installing the heater, consideration must be given to proper
location. Location selected should be as close to the wall as
practicable and as centralized with the water piping system as
possible.
CAUTION
In cold climates provide protection against freeze-up.
THE HEATER SHOULD BE LOCATED IN AN AREA WHERE
LEAKAGE OF THE TANK OR CONNECTIONS WILL NOT
RESULT IN DAMAGE TO THE AREA ADJACENT TO THE
HEATER OR TO LOWER FLOORS OF THE STRUCTURE.
When such locations cannot be avoided, a suitable drain
pan should be installed under the heater, see Figure 1. The
pan should have a minimum length and width of at least
2 inches (51mm) greater than the diameter of the heater and
should be piped to an adequate drain. Drain pans suitable for
these heaters are available from your dealer orA. O. Smith Water
Products Company, 5621 W. 115th Street, Alsip, Illinois 60803.
WARNING
DO NOT INSTALL THIS WATER HEATER DIRECTLY ON A
CARPETED FLOOR. A FIRE HAZARD MAY RESULT. Instead
the water heater must be placed on a metal or wood panel
extending beyond the full width and depth by at least 3 inches
(76.2mm) in any direction. If the heater is installed in a carpeted
alcove or closet, the entire floor shall be covered by the panel.
Also, see DRAINING.
WATER CONNECTIONS
Refer to Figure 1 for typical installation. A suitable pipe thread
sealant must be used to prevent leakage.
WATER (POTABLE) HEATING AND
SPACE HEATING
1. All piping components connected to this unit for space
heating applications shall be suitable for use with potable
water.
2. Toxic chemicals, such as those used for boiler treatment,
shall NEVER be introduced into this system.
3. This unit may NEVER be connected to any existing heating
system or component(s) previously used with a non-potable
water heating appliance.
4. When the system requires water for space heating at
temperatures higher than required for domestic water
purposes, a tempering valve must be installed. Please refer
to Figure 2 for suggested piping arrangement.
FIGURE2.
Installation:
Do not install water heater
where flammable products will
be stored or used unless the
mainburner andpilot flames are
at least 18" above the floor. This
will reduce, but not eliminate, the
riskof vapors being ignited bythe
main burner or pilot flame.

5
CLOSED WATER SYSTEM
A closed system will exist if a back-flow preventer (check valve),
pressure reducing valve, or other similar device is installed in
the cold water line between the water heater and the street main
(or well). Excessive pressure may develop due to the thermal
expansion of heated water causing premature tank failure or
intermittentreliefvalveoperation. This typeoffailure is not covered
by the limited warranty. An expansion tank may be necessary in
the cold water supply to alleviate this situation, see Figure 1.
Contact the local plumbing authority.
If the temperature and pressure relief valve on the appliance
discharges periodically, this may be due to thermal expansion
in a closed water supply system. Contact the water supplier or
local plumbing inspector on how to correct the situation. Do not
plug the temperature and pressure relief valve.
GAS CONNECTIONS
The minimum gas supply pressure for input adjustment is
5.0" W.C. (1.25 kPa) for natural gas 11.0" W.C. (2.74 kPa) for propane.
THEHEATERISNOTINTENDED FOROPERATIONATHIGHER
THAN 10.5" (2.6 kPa) FOR NATURAL & 13.0" (3.24 kPa) FOR
PROPANE WATER COLUMN SUPPLYPRESSURE. EXPOSURE
TO HIGHER GAS SUPPLY PRESSURE MAY CAUSE DAMAGETO
THECONTROLWHICHCOULDRESULTIN FIRE OR EXPLOSION.
If overpressure has occurred such as through improper testing of gas
lines or emergency malfunction of the supply system, the control must
becheckedfor safe operation. Makesurethat the outsideventson 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.
IT IS IMPORTANT TO GUARD AGAINST CONTROL FOULING
FROM CONTAMINANTS IN THE GAS WAYS. SUCH FOULING
MAYCAUSE IMPROPER OPERATION, FIREOREXPLOSION.
All piping must comply with local codes and ordinances or with
the National Fuel Gas Code (ANSI Z223.1, NFPA 54) whichever
applies. Copper and brass tubing and fittings (except tin lined
copper tubing) shall not be used.
REFER TO FIGURE 1 FOR CONNECTION DETAILS. BEFORE
ATTACHING THE GAS LINE BE SURE THATALL GAS PIPE IS
CLEAN ON THE INSIDE.
TOTRAPANYDIRTORFOREIGNMATERIALINTHEGASSUPPLY
LINE, A DIRT LEG (SOMETIMES CALLED DRIP LEG) MUST BE
INCORPORATED IN THE PIPING, SEE FIGURE 1.The dirt leg must
be readily accessible. Install in accordance with recommendations of
serving gas supplier. Refer to the current edition of ANSI Z223.1.
To prevent damage, care must be taken not to apply too much
torque when attaching gas supply pipe to gas valve inlet. The
valve inlet has a hexagon shape for use with a backup wrench.
Apply joint compounds (pipe dope) sparingly and only to the
male threads of pipe joints. Do not apply compound to the first
two threads. Use compounds resistant to the action of liquefied
petroleum gases. Do not use teflon tape on gas valve.
DISCONNECT THE APPLIANCE AND ITS INDIVIDUAL SHUT OFF
VALVE FROM THE GAS SUPPLY PIPING SYSTEM DURING ANY
SUPPLY PRESSURE TESTING EXCEEDING 1/2 PSI
(3.5 kPa). GAS SUPPLY LINE MUST BE CAPPED WHEN
DISCONNECTEDFROMTHEHEATER.FORTESTPRESSURESAT
1/2 PSI (3.5 kPa) OR LESS, THE APPLIANCE NEED NOT BE
DISCONNECTED, BUT MUST BE ISOLATED FROM THE SUPPLY
PRESSURETESTBYCLOSINGTHEMAIN MANUALGAS VALVE.
BEFORE PLACING THE HEATER IN OPERATION, CHECK
FOR GAS LEAKAGE. USE SOAP AND WATER SOLUTION OR
OTHERMATERIALACCEPTABLEFORTHISPURPOSE.DONOT
USE MATCHES, CANDLES, FLAME OR OTHER SOURCES OF
IGNITIONTOLOCATE GASLEAKS.
RELIEF VALVE (P)- See FIGURE 1.
A NEW TEMPERATURE AND PRESSURE RELIEF VALVE
COMPLYING WITHTHE STANDARD FORRELIEF VALVESAND
AUTOMATIC GAS SHUT OFF DEVICES FOR HOT WATER
SUPPLY SYSTEMS, ANSI Z21.22 (CURRENT EDITION) MUST
BE INSTALLED IN THE HEATER IN THE MARKED OPENING
PROVIDED. THE VALVE MUST BE OFA SIZE (INPUT RATING)
THAT WILLBE ADEQUATE FOR YOUR SIZE HEATER.
Check the metal tag on the relief valve and compare it to the
heater’s rating plate. The pressure rating of the relief valve must
not exceed the working pressure shown on the rating plate of the
heater. In addition, the hourly Btu rated temperature steam
discharge capacity of the relief valve shall not be less than the
inputrating of the heater. NOVALVEISTOBE PLACED BETWEEN
THERELIEFVALVEANDTANK. DO NOTPLUGTHERELIEFVALVE.
The drain line connected to this valve must not contain a reducing
coupling or other restriction and must terminate near a suitable
drain to prevent water damage during valve operation. The
discharge line shall be installed in a manner to allow complete
drainage of both the valve and line. DO NOT THREAD, PLUG OR
CAP THE END OF THE DRAIN LINE.
VENTING
WARNING
NEVER OPERATE THE HEATER UNLESS THE INTAKE AND
EXHAUSTAREVENTEDTOTHEOUTDOORSANDHASADEQUATE
AIR SUPPLY TOAVOID RISKS OF IMPROPER OPERATION, FIRE,
EXPLOSION,ORASPHYXIATION.IFTHEWATERHEATERISBEING
INSTALLED AS A REPLACEMENT FOR AN EXISTING POWER
VENTED HEATER IN PRE-EXISTING VENTING, A THOROUGH
INSPECTION OF THE EXISTING VENTING SYSTEM MUST BE
PERFORMEDPRIORTOANYINSTALLATIONWORK.VERIFYTHAT
THECORRECTMATERIALASDETAILEDABOVEHASBEENUSED,
AND THAT THE MINIMUM OR MAXIMUM VENT LENGTHS AND
TERMINALLOCATIONASDETAILEDINTHISMANUALHAVEBEEN
MET. CAREFULLY INSPECTTHE ENTIRE VENTING SYSTEM FOR
ANYSIGNSOFCRACKSORFRACTURES,PARTICULARLYATTHE
JOINTS BETWEEN ELBOWS AND OTHER FITTINGS AND THE
STRAIGHTRUNSOFVENTPIPE.CHECKTHESYSTEMFORSIGNS
OFSAGGINGOROTHERSTRESSESINTHEJOINTSASARESULT
OFMISALIGNMENTOFANYCOMPONENTSINTHESYSTEM.IFANY
OF THESE CONDITIONS ARE FOUND, THEY MUST BE
CORRECTED IN ACCORDANCE WITH THE VENTING
INSTRUCTIONS IN THIS MANUAL BEFORE COMPLETING THE
INSTALLATIONANDPUTTINGTHEWATERHEATERINTOSERVICE.
WARNING
THESE MODELS ARE CERTIFIED FOR VERTICAL VENTING
ANDSIDE WALLVENTING. THEUNITCONSISTSOFAN INTAKE
VENT TERMINALAND AN EXHAUST VENT TERMINAL WHICH
MUSTBEUSEDTOTERMINATETHE VENTINGARRANGEMENT.
IF THE VENT TERMINALS SUPPLIED WITH THIS UNIT ARE
NOT USED TO TERMINATE THE VENTING ARRANGEMENT,
THERISK OF IMPROPER OPERATION,FIRE, EXPLOSION, OR
ASPHYXIATION WILLINCREASE.

6
COMBUSTION AIR AND EXHAUST
WARNING
WHEN DETERMINING THE INSTALLATION LOCATION
FOR A POWER DIRECT VENT WATER HEATER, SNOW
ACCUMULATION AND DRIFTING SHOULD BE CONSIDERED
IN AREAS WHERE APPLICABLE.
Venting Through an Outside Wall - Clearances
• 0" clearance for 3" PVC,ABS, or CPVC Schedule 40 piping
from combustible surfaces.
• 18" (45.7 cm) minimum in all directions from any
obstruction, such as a wall, that may interfere.
• 12" (30.5 cm) minimum from the ground and corners, 9"
(23 cm) ceiling overhang, see Figure 3.
FIGURE3.
• The Power Direct Vent outlet terminal shall terminate at
least 36" (91cm) above any forced air inlet located within
10 feet (305 cm), see Figure 4.
• The Power Direct Vent outlet terminal of 50,000 BtuH input
models or less shall terminate at least 9" (23 cm) below,
9" (23 cm) horizontally from or 9" (23 cm) above any door,
window or gravity air inlet into the building, see Figure 4.
• The Power Direct Vent outlet terminal of over 50,000 BtuH
input models shall terminate at least 12" (30.5 cm) below,
12" (30.5 cm) horizontally from or 12" (30.5 cm) above any door,
window or gravity air inlet into the building, see Figure 4.
• 18" (45.7 cm) minimum from other natural draft (gravity)
direct vent, power vent or power direct vent appliance inlet
and/or outlet vent(s) when directly above or 135° to either
side of center line, see Figure 5.
• 24" (61 cm) minimum from any appliance inlet and/or outlet
vents when directly below or 45° to either side of center
line, see Figure 5.
FIGURE5.
• The location selection must provide clearances for servicing
and proper operation of the water, see Figure 6.
FIGURE6.
• The venting system must be installed in a manner which
allows inspection of the installation of the venting pipes
and joints as well as periodic inspection after installation
as required by the National Fuel Gas Code ANSI Z223.1.
FIGURE4.

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WARNING
VENT TERMINATION MUST NOT BE WITHIN 4 FEET(122 cm)
OFANYITEMSSUCHASGASMETERS,GASVALVESOROTHER
GASREGULATINGEQUIPMENT.
WIRE FENCE
Whenthe water heateroutlet terminal islow enoughto be touched
accidentally, or is accessible to small children, a wire mesh
chain link fence (as show in Figure 7) may be used. Care should
be taken to maintain adequate ventilation around the outlet
terminal. If a chain link fence is installed, it must not be used as
a storage area for items that may block proper ventilation.
FIGURE7.
Venting Through Roof - Clearances
• 0" clearance for 3" PVC, ABS, or CPVC Schedule 40 piping
from combustible and noncombustible surfaces.
• The vent exhaust outlet and air inlet terminals shall terminate at
least 18 inches (45.7 cm) above the roof surface, see Figure 8.
• The venting system must be installed in a manner which
allows inspection of the installation of the venting pipes and
joints as well as periodic inspection after installation as
required by ANSI Standards.
AIR FOR VENTILATION FOR APPLIANCES
LOCATED IN CONFINED SPACES
Air for ventilation should be provided if installed in a confined
space. Refer to the National Fuel Gas Code, ANSI Z223.1.
FIGURE9.
Horizontal runs must be securely supported at 3 1/2 foot (8.9 cm)
intervals and vertical runs supported at 5 foot (1.5 cm) intervals.
VENTING THROUGH AN OUTSIDE WALL
A. ALL 75 GAL. (283.9L) 65,000 & 70,000 BTU/HR MODELS & 50
GAL.(189.3L)60,000 & 65,000BTU/HRMODELS, SEE FIGURE 10.
In the carton is supplied:
1. Two 3" inlet and outlet PVC Schedule 40 - 45° vent caps.
2. A3" ABS Schedule 40 - 90° street elbow; used to connect the
outlet vent pipe to the water heater when the outlet vent pipe
is to be turned horizontally directly off the blower.
3. A 5' (1.52 m) section of 3" ABS Schedule 40 outlet vent pipe
(more may be required and must be supplied locally).
FIGURE 10. HI BTU MODELS.
1. The water heater requires its own (separate) venting system.
2. Only 3" ABS Schedule 40 piping & fittings are acceptable
materials on the first 5' of outlet vent system. This applies to only 50
gal.(189.3 L) Hi BTU input models and all 75 gal. (283.9 L) models.
3. 3" PVC, ABS, or CPVC Schedule 40 piping & fittings are
acceptable materials for the inlet vent system and for the
outlet vent system after the first 5' (1.52 m).
4. It cannot be connected to existing vent piping or chimney.
5. When venting through an outside wall, the vents must
terminate horizontally to the outdoors.
B. ALL50GAL.(189.3L)38,000AND40,000BTU/HRMODELS & 40
GAL.(151.4L)36,000 & 40,000 BTU/HRMODELS,SEE FIGURE 11.
In the carton is supplied:
1. Two 3" inlet and outlet PVC Schedule 40 - 45° vent caps.
All other piping must be supplied by the supplier.
FIGURE8.

8
FIGURE11. STANDARD MODELS.
* If making an immediate horizontal run of vent off the blower,
two 3" PVC or ABS Schedule 40 street elbows are required.
1. The waterheater requiresits own (separate)venting system.
2. 3" PVC, ABS or CPVC Schedule 40 piping and fittings are
acceptable materials for the vent system.
3. It cannot be connected to existing vent piping or chimney.
4. When venting through an outside wall, the vents must
terminate horizontally to the outdoors.
VENTING SYSTEM EXAMPLE INSTALLATION
FOR ALL MODELS
The vent piping cannot under any circumstances be run downhill.
FIGURE12.
The vent piping can be installed as follows:
1. Horizontal runs require a minimum1/8"(3.2mm) rise per 5' (1.52 m).
FIGURE13.
FIGURE14.
FIGURE15.
2. The total vertical and horizontal vent runs cannot exceed
the maximum length with the number of 90° elbows as
specified in the table below. If more elbows are required,
the venting distance must be reduced 5 feet (1.52 m) for
every 90° elbows:
3" DIA. VENTS NUMBER OF 90° DEG.
MAX.LENGTH(FT.) ELBOWS*
45 (13.72 m) 1
40 (12.2 m) 2
35 (10.7 m) 3
*NOTE: Two 45° elbows are equivalent to one 90° elbow. One
90° elbow equals 5 feet (1.52 m) of equivalent vent length.
FIGURE16.
3. Minimum vent length for all models is 18 inches (45.7 cm).

9
FIGURE17.
Cementing PVC, ABS or CPVC Pipe and Fittings
Readandobserve all safetyinformation printed on printer, cleaner,
and cement container.
DANGER
Primer, cleaner, and cements are extremely flammable. They
are harmful or fatal if swallowed. The vapors are harmful. They
may irritate eyes and skin and can be absorbed through the skin.
PRECAUTIONS
Always store primers, cleaner, and cements in cool, dry, well
ventilatedplaces. Do not store these near heat, sparks, or flames.
Keep container closed. Use them in well ventilated areas. Wear
impervious clothing while handling. Do not smoke, eat, or drink
whilehandling. Wash thoroughly after handlingand beforeeating.
Wear eye protection when handling. If swallowed, drink water,
do not induce vomiting, and call a physician or poison control
center immediately. If inhaled, get fresh air and seek medical
attention if ill feelings persist. In case of eye and skin contact,
immediately flush with plenty of water for 15 minutes and seek
medical attention if irritation persists. KEEP OUT OF REACH OF
CHILDREN.
All primers, cleaners and cements must meet all local codes and
applicablestandardoftheAmerican Society ForTesting Materials
Standards.
Before using primers, cleaners, and cements, stir or shake,
making sure contents are liquid. Do not use if found to be lumpy
or jelly-like.
1. Cut pipe ends squarely, removing all burrs and dirt.
2. Dry fit pipe and fittings to be connected for proper fit.
3. Clean pipe and fitting with a primer/cleaner.
4. Applya thin coat of cement tofitting, avoiding puddling inside.
5. Apply a liberal coat of cement to pipe, leaving no voids.
6. QUICKLY assemble parts while cement is fluid! If you wait
too long, re-coat pipes.
7. Push pipe completely into socket of fitting, turning as it goes
until it bottoms.
8. Hold pipe and fitting together for 30 seconds. Then carefully
clean off excess with a cloth. Allow connections a sufficient
time to cure before disturbing.
9. Remember that vent pipes must be adequately and securely
supported.
APPROXIMATE SETTING TIME FOR 2-1/2" to 4" PIPE JOINTS.
MOVEMENT COMPLETE
OFJOINT SET
90°F (32°C) TO150°F (66°C) 3/4 hr. 8 hrs.
50°F (10°C) TO 90°F (32°C) 1 hr. 15 hrs.
9°F (-12°C) TO 50°F (10°C) 1-1/3 hr. 18 hrs.
VENT PIPE SEPARATION
The inlet and outlet vent pipes must be separated by a minimum
distance of 6-1/2" (16.5 cm) up to 24" (61cm) maximum.
FIGURE18.
CUTTING OPENINGS THROUGH AN OUTSIDE WALL AND
COLLAR INSTALLATION
After reading the manual and you have determined the location
of the opening in the wall, (using the drawing below), cut one
3-1/2" (89 cm) diameter hole for the inlet vent piping and one
3-1/2" (89cm) diameter hole for the outlet vent piping through an
exterior wall.
NOTE: When determining locations of the openings in the
outside wall allow for the 1/8" (3.2 mm) rise per 5' (1.52 m) that
has taken place in the horizontal run.
FIGURE19.
The 3" PVC,ABS or CPVC Schedule 40 vent pipe can be run from
the water heater through the wall or from the wall to the water
heater, whichever is most convenient. The vent pipe must extend
a minimum of 1-1/2" (38 mm) through the exterior wall. Extending
the vent cap as far as possible from the surface of the exterior

10
wall will help minimize discoloration of the wall. Note that the
inside flue mounting adaptors must be slipped over the vent
piping before locating the pipe through the wall. Before securing
the inside and outside collars to the wall, use a silicone sealer
between pipe and opening to insure a water and air tight seal.
INSTALLATION SHOWING USE OF PVC, ABS OR CPVC PIPE
FOR INLET AND OUTLET VENT PIPE.
FIGURE20.
CONNECTING VENT TO BLOWER
1. If making an immediate horizontal run of vent off the blower,
one 3" PVC inlet and one 3" PVC (ABS for 50 Gal. (189.3 L)
and 75 Gal.(283.9 L) Models) outlet Schedule40 streetelbows
are required. Place the elbow in the required direction on the
blower and using three sheet metal screws, attach the elbow.
FIGURE21.
2. If there is to be a vertical run from the blower, the 3" PVC inlet
and the 3" PVC (ABS for 50 Gal. (189.3 L) and 75 Gal.(283.9
L) Models) outlet Schedule 40 pipe must be attached to the
blower and venting hood, using six sheet metal screws.
FIGURE22.
VENTINGTHROUGH A ROOF
Two 3" inlet and outlet PVC Schedule 40-45° vent caps are supplied.
A 5' (1.52 m) section of 3" ABS Schedule 40 outlet vent pipe
(50 Gal. (189.3 L) Hi BTU input & all 75 Gal. (283.9 L) Models
only) is supplied on certain models only. (More may be required
and must be supplied locally).
1. The water heater requires its own (separate) venting system.
2. Only 3" ABS Schedule 40 piping and fittings are acceptable
materials on the first 5' (1.52 m) of the outlet vent system for
some 50 Gal. (189.3 L) and 75 Gal. (283.9 L) models.
3. 3" PVC, ABS, or CPVC Schedule 40 piping and fittings are
acceptablematerials for the inlet vent system and for the outlet
vent system (after the first 5' (1.52 m) for 50 Gal. (189.3 L) Hi
BTU input and 75 Gal. (283.9 L) Models only).
4. It cannot be connected to existing vent piping or chimney.
5. It must terminate vertically to the outdoors.
6. The total vertical and horizontal runs cannot exceed the
maximum length with a maximum number of 90° elbows as
specified in the table below. If more elbows are required, the
venting distancemust bereduced 5' (1.52 m) for every90° elbow.
3"DIA.VENTS NUMBER OF90°DEG.
MAX.LENGTH(FT.) ELBOWS*
45 (13.72 m) 1
40 (12.2 m) 2
35 (10.7 m) 3
*NOTE: Two 45° elbows are equivalent to one 90° elbow. One
90° elbow equals 5' (1.52 m) of equivalent vent length.
FIGURE23.
WIRING
DANGER
DO NOT USE AN EXTENSION CORD. IF THERE IS NOT A
SUITABLE RECEPTACLE AND/OR LOCAL CODES PROHIBIT
USEOFAPOWERCORD,FIELDWIRINGMUSTBEPROVIDED.
THEAPPLIANCE,WHENINSTALLED, MUSTBEELECTRICALLY

11
GROUNDED IN ACCORDANCE WITH LOCAL CODES OR IN
THE ABSENCE OF LOCAL CODES, WITH THE NATIONAL
ELECTRICALCODE,ANSI/NFPA70.
If local codes do not permit use of a flexible power supply cord.
OPTIONAL Field Installed Wiring
1. Remove screws to remove wiring junction cover.
2. A standard 1/2" conduit opening has been made in the water
heater junction box for the conduit connection.
3. Use wire nuts and connect the power supply wiring to the
wires inside the water heater's junction box.
4. Be certain that neutral and line connections are not reversed
when making these connections.
5. Replace front plate and secure with screws.
FIGURE24.
SCHEMATIC DIAGRAMS
FIGURE25.
WARNING
DISCONNECT FROM ELECTRICAL SUPPLY BEFORE
SERVICING UNIT. REPLACE ALL DOORS AND PANELS
BEFOREOPERATINGHEATER.
IF ANY OF THE ORIGINAL WIRES SUPPLIED WITH THE
APPLIANCE MUST BE REPLACED, IT MUST BE REPLACED
WITH APPLIANCE WIRE MATERIAL WITH MINIMUM
TEMPERATURE RATING OF 105°C ANDA MINIMUM SIZE OF
NO.18 AWG.
FIGURE26.
T & P VALVEAND PIPE INSULATION
(ONSELECTED MODELS)
Remove insulation for T & P valve and pipe connections from
carton.
Fit pipe insulation over the incoming cold water line and the hot
water line. Make sure that the insulation is against the top cover
of the heater.
Fit T & P valve insulation
over valve. Make sure that
the insulation does not
interfere with the level of
the T& P valve.
Secure all insulation
using tape.
FIGURE27.

12
FORYOUR SAFETYREADBEFOREOPERATING
WARNING: If you do not follow these instructions exactly, a fire or
explosion may result causing property damage, personal injury or loss
of life.
A. This appliance does not have a pilot. It is equipped
with an ignition device which automatically lights
theburner. Do NOT try to light the pilot by hand.
B. BEFORE OPERATING smell all around the appliance
area for gas. Be sure to smell next to the floor
because some gas is heavier than air and will settle
on the floor.
WHATTODO IFYOUSMELLGAS:
• Do not try to light any appliance.
• Do not touch any electric switch;
do not use any phone in your building.
• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire
department.
C. Useonlyyour hand to push in the gascontrol buttons.
Never use tools. If the control buttons will not push
in, don’t try to repair them, call a qualified service
technician. Force or attempted repair may result in
a fire or explosion.
D. Do not use this appliance if any part has been under
water. Immediately call a qualified service
technician to inspect the appliance and to replace
any part of the control system and any gas control
which has been under water.
OPERATINGINSTRUCTIONS
1. Set thermostat to the lowest setting by first
pressing the COOLER and HOTTER
buttons together and holding for 1 second. Then
press the COOLER button until the WARM
indicator light appears.
BEFORE OPERATING: ENTIRE SYSTEM MUST BE FILLED WITH WATER ANDAIR PURGED FROMALL LINES.
1. STOP! Read the safety information above,
on this label.
2. Set the ON/OFF switch on the control box to the
“ON” position.
3. Set the thermostat to the lowest setting by first
pressing the COOLER and HOTTER
buttons together and holding for 1 second. Then
press the COOLER button until the WARM
indicator light appears.
4. Set the ON/OFF switch on the control box to the
“OFF” position.
5. This appliance is equipped with a device which
automatically lights the burner.
DONOTTRYTOLIGHTTHEBURNERBYHAND.
6. Waitfive (5)minutes to clear outany gas.
If you then smell gas, STOP! Follow “B”
in the safety information above on this label. If
you don’t smell gas, go to the next step.
7. Turn on all electrical power to the appliance.
8. Set the ON/OFF switch on the control box to the
“ON” position.
9. Set the thermostat to desired setting by first
pressing the COOLER and HOTTER
buttons together and holding for 1 second.
Then press the HOTTER button .
10. WATER TEMPERATURE ADJUSTMENT is
approximately 120°F (49°C).
CAUTION: Hotter water increases the risk
of scald injury. Consult the instruction
manual before changing temperature.
11. If the appliance will not operate, follow the
instructions “TO TURN OFF GAS TO
APPLIANCE” and call your technician or gas
supplier.
WARNING: TURNOFFALLELECTRIC
POWERBEFORESERVICING
TOTURNOFFGASTOAPPLIANCE
2. Set the ON/OFF switch on the control box to the
“OFF” position.
3. Turn off all electric power to the appliance if service
is to be performed.

13
OPERATION
NEVER OPERATE THE HEATER WITHOUT FIRST BEING
CERTAIN IT IS FILLED WITH WATER AND A TEMPERATURE
ANDPRESSURERELIEF VALVEIS INSTALLED INTHERELIEF
VALVE OPENING OF THE HEATER. DO NOT ATTEMPT TO
OPERATEHEATER WITHCOLDWATERINLETVALVECLOSED.
FILLING
1. Close the heater drain valve by turning handle clockwise,
Figure 1.
2. Openanearby hot waterfaucetto permit theairin the system
to escape.
3. Fully open the cold water inlet pipe valve allowing the heater
and piping to be filled, see Figure 1.
4. Close the hot water faucet as water starts to flow.
5. The heater is ready to be operated.
TEMPERATURE REGULATION
DANGER
THIS WATER HEATER IS EQUIPPED WITH AN ADJUSTABLE
THERMOSTAT TO CONTROL WATER TEMPERATURE. HOT
WATER TEMPERATURES REQUIRED FOR AUTOMATIC
DISHWASHER AND LAUNDRY USE CAN CAUSE PAINFUL
SCALDING WITH POSSIBLE SERIOUS AND PERMANENT
INJURY. THE TEMPERATURE AT WHICH INJURY OCCURS
VARIES WITH THE PERSON’S AGE AND THE TIME OF THE
EXPOSURE. THE SLOWER RESPONSE TIME OF CHILDREN,
AGED OR DISABLED PERSONS INCREASES THE HAZARDS
TO THEM. NEVER ALLOW SMALL CHILDREN TO USE A HOT
WATER TAP, ORTODRAWTHEIR OWN BATH WATER.NEVER
LEAVE A CHILD OR DISABLED PERSON UNATTENDED IN A
BATHTUB ORSHOWER.
THE WATER HEATER SHOULD BE LOCATED IN AN AREA
WHERETHE GENERALPUBLIC DOESNOTHAVEACCESS.IF
ASUITABLEAREA IS NOTAVAILABLE,ACOVER SHOULD BE
INSTALLED OVER THE THERMOSTAT TO PREVENT
TAMPERING.
It is recommended that lower water temperatures be used to
avoid the risk of scalding. It is further recommended, in all cases,
that the water temperature be set for the lowest temperature
which satisfies your hot water needs. This will also provide the
most energy efficient operation of the water heater. The water
temperature setting was factory set at the lowest temperature;
Pressing the "COOLER" button decreases temperature and
pressing the "HOTTER" button increases the temperature.
SETTINGTHEWATERHEATERTEMPERATUREAT120°F(49°C)
(APPROX. “ ” MARK ON TEMPERATURE SETTING OF GAS
VALVE) WILL REDUCE THE RISK OF SCALDS. Some states
require settings at specific lower temperatures.
Figure 28 shows the approximate water temperatures produced
atvarious thermostat dial settings. Short repeated heating cycles
caused by small hot water uses can cause temperatures at
the point of use to exceed the thermostat setting by up to 30°F
(-1°C). If you experience this type of use you should consider
using lower temperature settings to reduce scald hazards.
Valves for reducing the point of use temperature by mixing cold
and hot water are available, see Figure 2. Also available are
inexpensive devices that attach to faucets to limit hot water
temperatures. Contact a licensed plumber or the local plumbing
authority.
To avoid any unintentional changes in water temperature
settings, the control has a tamper resistant feature for changing
the temperature setting. To change the temperature setting follow
these instructions:
1. "Wake Up" the temperature indicators by holding down both
"COOLER" and "HOTTER" temperature adjustment buttons
at the same time for one second, see Figure 28. One or two
of the temperature indicators will light up. These indicators
will only remain on for 30 seconds if no further buttons are
pressed. After 30 seconds the control will go back to "Sleep"
mode.
2. Release both of the temperature adjustment buttons.
A. To decrease the temperature press and release the
"COOLER" button until the desired setting is reached.
B. To increase the temperature press and release the
"HOTTER" button until the desired setting is reached.
NOTE: Holding down the button will not continue to lower or
raise the temperature setting. The button must be pressed and
released for each temperature change desired.
SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAIL
TOSHUT OFF,TURN OFFTHE MAIN MANUALGAS SHUTOFF
VALVE TOTHEAPPLIANCE, SEE FIGURE1(G).
Time to Produce
Display 2nd & 3rd Degree
Temperature Setting A B C Burns on Adult Skin
C=Flashing=approx. 160°F(71oC) About 1/2 seconds
C = Approx. 150°F(66oC) About 1 1/2 seconds
B = Approx. 140°F(60oC) Less than 5 seconds
A = Approx. 130°F(54oC) About 30 seconds
=Approx. 120°F(49oC) More than 5 minutes
WARM = Approx. 80°F(27oC) - - - - - - - - - - - - - -
FIGURE28.

14
WATER HEATING IGNITION SEQUENCE
(Make sure gas and electric power are connected properly)
1. The ignition control module is powered and monitors the
system, waiting for a call for heat from the thermostat.
2. The thermostat calls for heat by reading a resistance value
withina given rangedirectly proportional towater temperature.
3. The control Module:
a. Checks the pressure switch for an open circuit.
b. Energizes the blower.
c. Checks the pressure switch for a closed circuit to prove
draft.
d. Sends line voltage to the hot surface igniter with a
20 second warm up period.
e. Opens the gas valve and checks the sensing rod for
flame.
4. The burner heats the water to the desired thermostat setting.
a. The resistance in the thermostat rises to the value
selected by the temperature setting.
b. The control module closes the gas valve and 5 seconds
later, removes power from the blower.
5. Cycle is completed.
FIGURE29.
CONTROLSEQUENCE-HOTSURFACEDIRECTIGNITION
Pre-purge 5 seconds.
HSI Warm-up 20 seconds.
Ignition Activation Period 4 seconds.
Flame Recognition Period 1 second.
Ignition Trial 4 seconds.
Interpurge 5 seconds.
Post-purge 5 seconds.
Retries 2
Reset from Lockout 1 hr.
Flame Sensing (Nominal)
HSI Off/Run Mode 4.0µ DC
HIGH ALTITUDE INSTALLATION
WARNING
INSTALLATIONS ABOVE 2000 (610 m) FEET REQUIRE
REPLACEMENTOF THE BURNER ORIFICE INACCORDANCE
WITHTHE NATIONALFUELGASCODE (ANSIZ223.1/NFPA54).
FAILURETOREPLACETHEORIFICEWILLRESULTINIMPROPER
ANDINEFFICIENTOPERATIONOFTHEAPPLIANCE,PRODUCING
CARBON MONOXIDE GAS IN EXCESS OF SAFE LIMITS, WHICH
COULD RESULT IN EXCESS OF SAFE LIMITS, WHICH COULD
RESULT IN SERIOUS PERSONALINJURYORDEATH.
A.O. Smith builds models specifically for high altitude service.
Please check the rating plate before making changes.
VENTING MANUAL RESET SWITCH
There is a venting manual reset switch located on the venting
hood. If the switch is activated, it will not reset itself. Before
resetting this reset switch, check for flue blockage and propriety
of the venting systems. To reset, press the red button.
FIGURE30.
MAINTENANCE
WARNING
DISCONNECT FROM ELECTRICAL SUPPLY BEFORE
SERVICINGUNIT.
FOR YOUR SAFETY, WATER HEATER SERVICE SHOULD BE
PERFORMED ONLY BYAQUALIFIED SERVICE TECHNICIAN.
READTHEGENERALSAFETYINFORMATION SECTION FIRST.

15
USERS OF THISAPPLIANCE SHOULD BE AWARE THAT GAS
COMPONENTS WEAR OUT OVER A PERIOD OF TIME. THE
GASCARRYING COMPONENTSOFTHISAPPLIANCESHOULD
BEINSPECTEDFORPROPEROPERATIONPERIODICALLYBY
AQUALIFIEDSERVICE TECHNICIAN.
MAIN BURNER
Check main burner every 12 months for proper flame
characteristics. This is done by removing door(s) on heater,
see Figure 1. The main burner should provide complete
combustionof gas; ignite rapidly; give reasonably quiet operation;
cause no excessive flame lifting from burner ports. Make sure
that the flow of combustion and ventilation air is not blocked.
If proper flame characteristics are not evident, check for
accumulation of lint or other foreign material that restricts or
blocks the air openings in the heater or burner. Also check
AIRREQUIREMENTS.
WARNING
SOOT BUILD-UP INDICATES A PROBLEM THAT REQUIRES
CORRECTION BEFORE FURTHER USE. CONSULT WITH A
QUALIFIEDSERVICE TECHNICIAN.
Should the main burner or burner air openings require cleaning,
turn the blower switch to “OFF” position and allow the burner to
cool. Remove the burner and clean with a soft brush. Clean
main burner orifice with a suitable soft material.
HIGH TEMPERATURE LIMIT SWITCH
(Single-Use Type Energy Cut Off)
The thermostat has a built-in limit switch which will actuate in
case of excessive water temperatures. The heater cannot be
relit until the gas control valve is replaced. It is important that a
serviceman be called to determine the reason for limit operation
and thus avoid repeated thermostat replacement. Lower the
temperature adjustment setting on new control.
VENTING SYSTEM
HAVEVENTINGSYSTEM CHECKED EVERYSIX MONTHSFOR
OBSTRUCTIONSAND/OR DETERIORATION IN VENT PIPING.
POWER VENTER MAINTENANCE
The “POWER” venter must be inspected yearly.
1. MOTOR - Motor must rotate freely.
For safety and satisfactory operation it is recommended that the
heater be checked once a year by a competent service person.
T & P VALVE
At least once a year, the temperature and pressure relief valve
must be checked to ensure that it is in operating condition. Lift
the lever at the top of the valve several times until the valve seats
properly and operates freely.
DANGER
THE WATER PASSING OUT OF THE VALVE DURING THIS
CHECKING OPERATION MAY BE EXTREMELY HOT. AVOID
CONTACT AND DISCHARGE SAFELY TO PREVENT WATER
DAMAGE.
DRAINING
If the heater is to be shut off and exposed to freezing
temperatures, it must be drained. Water, if left in the tank and
allowed to freeze, will damage the heater.
• Turn off the gas and cold water inlet valve to the heater.
• Opena nearby hot water faucet and the heater drain valve.
• BE CAREFUL TO GRASP THE DRAIN VALVE HANDLE
SOTHATTHE HAND ISNOTEXPOSEDTOHOTWATER.
IF DESIRED, A HOSE MAY BE CONNECTED TO THE
DRAINVALVETOCARRYTHEWATERAWAY.
DANGER: Thewater CAN BE HOT.
• The drain valve must be left open during the shutdown
period.
• To restart heater, refer to the FILLING instructions under
OPERATION.
Periodically open the drain valve and allow the water to run until
it flows clean. This will help prevent sediment build-up in the
tank.
It is normal for lime and scale deposits to form within the tank.
Such deposits will not be removed by periodic draining. It is
necessary to chemically delime the affected parts in water areas
where such deposits are encountered.
CONDENSATION
Water vapor can condense on the cooler surfaces of the tank
forming droplets, these drip into the fire or run out on the floor.
This is common at the time of startup after installation, during
periods of time when incoming water is very cold, or the heater
may be undersized for the requirements.
Droplets from the bottom of the flue may be due to corrosive
combustion products or improper vent. Check with your dealer
for more information.
CATHODIC PROTECTION - ANODE
The anode rod is used to protect the tank from corrosion. Most
hot water tanks are equipped with an anode rod. The sub-
merged rod sacrifices itself to protect the tank. Instead of
corroding the tank, water ions attack and eat away the anode
rod. This does not affect the water’s taste or color. The rod must
be maintained to keep the tank in operating condition.
Anode deterioration depends on water conductivity, not
necessarily water condition. A corroded or pitted anode rod
indicates high water conductivity and should be checked and/or
replaced more often than an anode rod that appears to be intact.
Replacement of a depleted anode rod can extend the life of your
water heater. Inspection should be conducted by a qualified
technician, and at a minimum should be checked annually after
the warranty period.

16
TROUBLE SHOOTING HELP
THERMOSTAT AND GAS SUPPLY CHECK
A hydrogen sulfide (rotten egg) odor may result if water contains
high sulfate and/or minerals. Chlorinating the water supply
should minimize the problem, see EXTENDED NON-USE
PERIODS.
NOTE: Anode rod must remain installed (except for inspection)
to avoid shortening tank life. See LIMITED WARRANTY. Replace
as necessary.
SERVICE AND REPAIR
The A.O. Smith water heater requires no special care other than
the normal maintenance as noted above. If you are having a
problem with your water heater, before calling for service please
refer to the following TROUBLESHOOTING sections. If service
becomes necessary, contact your dealer, installer or an
authorizedserviceagent. Do notattempt to repairthe water heater
yourself. Any work performed by unauthorized personnel may
void the warranty.
If you are having a problem with your A.O. Smith water heater
and are not pleased with the service you received:
• First,please contactyour dealer ortheA.O.Smith authorized
service agent in your area and explain to them why you are
not satisfied. This will usually correct the problem.
• Ifafter workingwith yourdealer orservice agentthe problem
has not been resolved to your satisfaction, please let us
know by either writing to us at:
A.O. Smith Water Products Company
Service Department
106 Adkisson St.
Ashland City, TN 37015
or, going to our website at: www.aosmithwaterheaters.com
Please click on: "Mail"
then click on: "Service"
and leave us a message.
Please be sure to provide the following information when writing
or e-mailing:
• Model Number
• Serial Number
• Date of Original Purchase
• Date Problem Originated
• Explanation of Problem
Also, please be sure to include a daytime telephone number.
No
Turn "ON" gas supply.
Is gas being supplied to the thermostat? Yes
Isthermostatcallingforheat?Run(hot)waterfromheater
and set adjustment button higher. Check using a
manometerat thermostat pressure tap.
Isthereaminimumgas pressure4"(1kPa) W.C.
fornatural gasor10"(2.5 kPa)W.C.for propane
(L.P.) gas?
Call gas company to
increasegaspressure.
GOTOTROUBLESHOOTING
SECTION,PAGE 17.
Yes
Yes
Yes
No

17
TROUBLE SHOOTING
Please check guidelines below. For your safety, water heater service should be performed only by a qualified service technician.
Read the GENERAL SAFETY INFORMATION section first.
PROBLEM SOLUTION
An open earth groundcircuit to the 1. Check that the earth ground connection is
ignition system. properlyconnected.
2. Check that the ground conductor on the
waterheateris properly connected.
Wiring error or a high resistance to 1. Checkforproper connection of line
earthground. neutral and hotwires.
2. Check that the water heater is securely
connectedtoearthground.
Pressureswitch remainedclosed longer 1. Pressure switch wiring is incorrect.
than 5 seconds after the call for 2. Replacepressure switch.
heatbegan.
Pressureswitchremainedopenlonger 1. Pressure switch wiring is incorrect.
than 5 seconds after the combustion 2. Pressure switch tubing not connected
blowerwas energized. correctly.
3. Air intake or exhaust obstructed.
Error in the hot surface igniter circuit. 1. Check that all wiring is correct and secure.
2. Replacehot surface igniter.
System in lockout. 1. Gas supply is off or too low to operate.
2. Hotsurface igniter notpositioned
correctly.
3. Lowvoltagetothewaterheater.
4. Electric polarity to unit is incorrect - test
andcorrect.
Probleminthegasvalvedriver circuit. 1. Turnpower to the water heaterofffor
10 seconds and the back on.
2. Replacegas controlvalve.
Problem with the internal circuit. 1. Turnpower to the water heater off for
10 seconds and then back on.
2. Replacegas controlvalve.
Problem with the internal circuit. 1. Turnpower to the water heater off for
10 seconds and then back on.
2. Replacegas controlvalve.
Flame signal sensed out of 1. Replacegascontrolvalve.
propersequence.
ECOactivated. 1. Replacegas control valve.
One ofthe temperature adjust 1. Press and release each of the buttons
buttons stuck closed. once.
2. Replacegas controlvalve.
Water temperaturesensor is 1. Check that all wiring is correct and secure.
eitheropen or shortcircuited. 2. Replace gas control valve.
A B C
A B C
A B C
A B C
A B C
A B C
A B C
A B C
A B C
A B C
A B C
A B C
A B C
LEDSTATUS
WATERHEATERCONTROL
WARNING: DONOT BY-PASSANYCONTROLSTO MAKEHEATEROPERATE.
OPERATEONLYASWIREDFROMFACTORY.

18
TROUBLE SHOOTING (Continued)
PROBLEM CAUSE SOLUTION
1) Blower will not run.
A) “ON/OFF” control switch turned off. Turn switch to the “ON” position.
B) Blower unplugged. Plug blower back into 115 Vac. outlet.
C) No power at outlet. Repair service to outlet.
D) Thermostat defective. Replace thermostat.
E) Control harness defective. Replace control harness.
F) High limit control circuit open. Replace ECO.
NOTENOUGH G) Blower motor defective. Replace Blower Assembly.
HOTWATER Thermostat problems.
A) Thermostat set too low. Set temperature control higher.
B) Thermostat or ECO defective. Replace thermostat or ECO as required.
Others
A) Heater undersized. Reduce hot water use.
B) Low gas pressure. Contact dealer.
C) Incoming water is unusually cold. Allow more time for heater to reheat.
D) Leaking hot water pipes or fixtures. Have plumber check and repair leaks.
A) Defective air flow restrictor. Take unit out of service immediately, call an
A.O. Smith service representative.
B) Not enough dilution air to mix with Proper dilution air must be provided for
flue gases in inlet tee. combustion and dilution of flue temp.
VENTPIPE TOO HOT Refer to “INSTALLATION” section.
(ABOVE170°F) C) Dilution air too hot for mixing with Supply air is too hot. Check for heat sources
flue gases. around intake terminal and blockage of
dilution air leg.
D) Wrong burner orifice. Install correct orifice.
A) Dirt in burner ports Turn off heater and gas, clean burner head.
B) Combustion air path restricted. Check intake venting arrangements for
YELLOWFLAME obstructions.
C) Not enough dilution air for proper Check Intake venting arrangement for
combustion. obstructions.
A) Water on the floor under heater. See “CONDENSATION” section.
CONDENSATION B) Water dripping from pan. Provide drip “TEE” to catch condensation,
see Figure 1.
Improperly sealed, hot or cold supply
connections, relief valve, drain valve Tighten threaded connections.
WATERLEAKS or thermostat threads.
Leakage from other appliances or water Inspect other appliances near water heater.
lines.
Condensation of flue products. Refer to “CONDENSATION” section.
Thermal expansion in closed water Install thermal expansion tank (DO NOT plug
LEAKINGT&P system. T&Pvalve).
Improperly seated valve. Check relief valve for proper operation
(DO NOT plug T&P valve).
HOTWATERODORS High sulfate or mineral content in Drain and flush heater thoroughly then refill.
(Referto CATHODIC water supply.
PROTECTION) Bacteria in water supply. Chlorinate water supply.
WATERTOOHOT Thermostat set too high. Refer toTEMPERATURE REGULATION.
WATERHEATERSOUNDS Condensation dripping on burner. Refer to CONDENSATION above.
SIZZLING-RUMBLING Sediment at bottom of heater tank. Clean sediment from tank. Refer to DRAINING
instruction in Maintenance section of manual.
SOOTING Improper combustion. Referto COMBUSTIONAIRAND EXHAUST on
page 6.
HEATERLIGHTSBUTGOES Outlet polarity is reversed. Test polarity and correct.
OUT IN 4-5 SECONDS

19
THISWARRANTYISAPPLICABLETOTHEORIGINALOWNER ONLY. If
the glass lined tank in this water heater shall prove upon examination by
A. O. Smith Corporation (the warrantor) to have leaked during the
warranty period in normal residential use, due to natural corrosion from
potable water therein, the warrantor will furnish the ORIGINAL OWNER
a replacement A. O. Smith water heater of equivalent size and current
model, or a replacement thermostat or thermocouple which fails in normal
use, in accordance with the warranty terms and conditions specified
below. THE A. O. SMITH REPLACEMENT MODEL OR PART WILL BE
WARRANTEDFORONLYTHEUNEXPIREDPORTIONOFTHEORIGINAL
WARRANTY. The warranty period will be determined by the original
installationdate of thewaterheater. PROOF-OF-PURCHASEANDPROOF-
OF-INSTALLATIONARENECESSARYTOVALIDATETHIS WARRANTY.
This warranty is not transferable and applies to models listed in Table 1.
TABLE1
WARRANTYPERIOD
MODELS TANK1PARTS2
GPDH/GPDT/GPDX 6 YEARS 6 YEARS
When the water heater has been used for other than single family
residential application: 1. The tank warranty shall be reduced to 3 years
for 10 year models, and 1 year for 6 year models. 2. The parts warranty
shall be reduced to one year for all models. Returned parts which meet
any of the following conditions are not covered by this warranty: 1)
Improper installation or removal, 2) damaged by other than normal wear,
3) replaced for cosmetic purposes, or 4) returned with defaced date
codes.
CONDITIONSAND EXCEPTIONS
This warranty shall apply only when the water heater is installed and
operated in accordance with 1) all local fire codes and plumbing codes,
ordinances and regulations, 2) the printed instructions provided with it,
3) good industry practices, and 4) proper safety practices such as but
not limited to a properly sized drain pan if installed in an area where
leakage from connections of the tank would result in damage to the area
adjacent to the heater. In addition, a new temperature and pressure
relief valve, certified by the American Gas Association must have been
properly installed and piped to the nearest drain.
This warranty shall apply only when the heater is:
• owned by the original purchaser;
• used at temperatures not exceeding the maximum calibrated setting
of its thermostat;
• not subjected to excessive water pressure fluctuations and not
subject to an operating pressure greater than 150 P.S.I.;
• filled with potable water, free to circulate at all times and with the tank
free of damaging water sediment or scale deposits;
• used in a non-corrosive and non-contaminated atmosphere;
• used with factory approved anode(s) installed;
• in its original installation location;
• in the United States, its territories or possessions, and Canada;
• sized in accordance with proper sizing techniques for residential
water heaters;
• bearing a rating plate which has not been altered, defaced or removed
except as required by the warrantor;
• not used in a closed system without a properly sized and installed
thermal expansion tank;
• fired at the factory rated input using the fuel stated on the face of the
rating plate;
• operated with the inner and outer combustion chamber doors in place;
• maintained in accordance with the instructions printed in the manual
included with the heater.
Any accident to the water heater or any part thereof (including freezing,
fire, floods, or lightning), any misuse, abuse or alteration of it, any
operation of it in a modified form, or any attempt to repair tank leaks or
parts, will void this warranty.
SERVICEAND LABOR RESPONSIBILITY
UNDERTHIS LIMITED WARRANTY,THEWARRANTORWILLPROVIDE
ONLY AREPLACEMENT WATER HEATER OR PARTTHEREOF. THE
OWNER IS RESPONSIBLE FORALL OTHER COSTS. Such costs may
include but are not limited to:
LIMITEDRESIDENTIALGAS WARRANTY
a. Labor charges for service, removal, or reinstallation of the water
heater or part thereof.
b. Shipping and delivery charges for forwarding the new water heater
or replacement part from the nearest distributor and returning the
claimed defective heater or part to such distributor except in the
state of California where such charges are the manufacturer’s
responsibility.
c. All cost necessary or incidental for handling and administrative
charges,and for anymaterials and/or permits required for installation
of the replacement heater or part.
LIMITATION ON IMPLIED WARRANTIES
Implied warranties, including any warranty of merchantability imposed on
the sale of this heater under state law are limited to one year duration for the
heater or any of its parts. Some states do not allow limitations onhow long an
implied warranty lasts, so the above limitations may not apply to you.
CLAIMPROCEDURE
Any claim under this warranty should be initiated with the dealer who
sold the heater, or with any other dealer handling the warrantor’s
products. If this is not practical, the owner should contact: A. O. Smith
Water Products Company, 125 Southeast Parkway, Franklin, TN, 37068
[phone]. Canadian customers should contact A. O. Smith
Enterprises, Ltd., P.O. Box 310-768 Erie Street, Stratford, Ontario N5A
6T3 [phone].
The warrantor will only honor replacement with identical or similar water
heater or parts thereof which are manufactured or distributed by the warrantor.
Dealer replacements are made subject to in-warranty validation by warrantor.
PROOF-OF-PURCHASEAND PROOF-OF-INSTALLATION DATESARE
REQUIRED TO SUPPORT WARRANTY FOR CLAIM FROM ORIGINAL
OWNER. THISFORMDOESNOTCONSTITUTEPROOF-OF-PURCHASE
ORPROOF-OF-INSTALLATION.
DISCLAIMERS
NOEXPRESSWARRANTYHASBEENORWILLBEMADEINBEHALFOF
THEWARRANTORWITHRESPECTTOTHEMERCHANTABILITYOFTHE
HEATERORTHEINSTALLATION,OPERATION,REPAIRORREPLACEMENT
OF THE HEATER OR PARTS. THE WARRANTOR SHALL NOT BE
RESPONSIBLE FOR WATER DAMAGE, LOSS OF USE OF THE UNIT,
INCONVENIENCE,LOSSOR DAMAGETOPERSONALPROPERTY, OR
OTHERCONSEQUENTIALDAMAGE. THEWARRANTORSHALLNOTBE
LIABLEBYVIRTUEOFTHISWARRANTYOROTHERWISEFORDAMAGE
TOANYPERSONS ORPROPERTY, WHETHERDIRECTOR INDIRECT,
ANDWHETHERARISINGIN CONTRACTORINTORT.
Some states do not allow the limitation or exclusion of incidental or
consequential damages, so the above limitation or exclusion may not
apply to you.
This warranty gives you specific legal rights, and you may also have
otherrightswhich varyfromstate to state.Should governmental regulations
or industry standards prohibit the Manufacturer from furnishing a
comparable model replacement under this warranty, the Owner will be
furnished with the closest comparable water heater meeting the then
currentgovernmental regulations andindustry standards.Asupplementary
fee may be assessed to cover the additional cost associated with the
changes made to meet applicable regulations and standards.
IMPORTANT INFORMATION
Model Number____________________________________________
SerialNumber_____________________________________________
Installation Information______________________________________
Date Installed_____________________________________________
Company’sName__________________________________________
Street or P.O. Box _________________________________________
City, State, and Zip Code____________________________________
Phone Number ___________________________________________
Plumber’s Name__________________________________________

20
125 SOUTHEAST PARKWAY • FRANKLIN, TN 37068
Phone: [phone] • Fax: [phone]
www.aosmithwaterheaters.com / email: parts @hotwater.com