A.O. Smith PXHT User manual

1
Instruction Manual
PRINTEDINTHEU.S.A 0805 PART NO. 184639-001
KEEPTHISMANUALINTHEPOCKETONHEATERFORFUTUREREFERENCE
WHENEVERMAINTENANCEADJUSTMENTORSERVICEISREQUIRED.
ALLTECHNICALAND WARRANTY QUESTIONS: SHOULDBEDIRECTEDTOTHELOCALDEALERFROMWHOMTHEWATERHEATERWAS
PURCHASED.IFYOUAREUNSUCCESSFUL,PLEASEWRITETOTHECOMPANYLISTEDONTHERATINGPLATEONTHEWATERHEATER.
RESIDENTIAL ELECTRIC
WATER HEATERS
FOR POTABLE WATER
HEATING ONLY
NOT SUITABLE FOR
SPACE HEATING
GAMA certification applies to all
residential electric water heaters
with capacities of 20 to 120 gallons.
Input rating of 12 Kw or less.
LISTED

2
SAFE INSTALLATION, USE AND SERVICE
Your safety and the safety of others is extremely important in the installation, use and servicing of this water heater.
Many safety-related messages and instructions have been provided in this manual and on your own water heater to warn you and
others of a potential injury hazard. Read and obey all safety messages and instructions throughout this manual. It is very
important that the meaning of each safety message is understood by you and others who install, use or service this water heater.
This is the safety alert symbol. It is used to alert you
to potential personal injury hazards. Obey all safety
messages that follow this symbol to avoid possible
injury or death.
All safety messages will generally tell you about the type of hazard, what can happen if you do not follow the safety message and
how to avoid the risk of injury.
IMPORTANTDEFINITIONS
•QualifiedInstaller: A qualifiedinstallermust haveabilityequivalent toalicensed tradesmaninthe fieldsofplumbing, andelectricalinstallation
of these appliances. This would include a thorough understanding of the requirements of the National Electrical Code and applicable local
electrical and plumbing codes (and tools necessary to confirm proper installation and operation of the water heater) as they relate to
the installation of electric water heaters. The qualified installer must have a thorough understanding of the water heater
InstructionManual.
•ServiceAgency: A serviceagency alsomusthaveabilityequivalent toa licensedtradesmanin thefields ofplumbing,andelectricalinstallation
of these appliances. This would include a thorough understanding of the requirements of the National Electrical Code and applicable local
electrical and plumbing codes (and tools necessary to confirm proper installation and operation of the water heater) as they relate to
the installation of electric water heaters. The service agency must have a thorough understanding of the water heater
InstructionManual.
DANGER
WARNING
CAUTION
DANGER indicates an imminently
hazardous situation which, if not avoided,
could result in death or injury.
WARNINGindicates a potentiallyhazardous
situation which, if not avoided, could result
in death or injury.
CAUTION indicatesa potentially hazardous
situation which, if not avoided, may result
in minor or moderate injury.
CAUTION used without the safety alert
symbol indicates a potentially hazardous
situation which, if not avoided, could result
in property damage.
CAUTION

3
GENERAL SAFETY
SAFEINSTALLATION,USEANDSERVICE ..............................2
GENERALSAFETY ..................................................................3
TABLEOFCONTENTS..............................................................3
INTRODUCTION ........................................................................4
Preparing for the New Installation ...................................4
NOTES ......................................................................................4
TYPICALINSTALLATION ..........................................................5
WIRINGDIAGRAMS ..................................................................6
MIXINGVALVEUSAGE ............................................................7
LOCATINGTHENEWWATERHEATER .....................................8
Facts to Consider About Location ...................................8
InsulationBlankets ...........................................................8
INSTALLINGTHENEWWATERHEATER ..................................8
WaterPiping ................................................................. 8-9
Temperature-Pressure Relief Valve........................... 9-10
Filling the Water Heater..................................................10
T&PValve and Pipe Insulation (Selected Models) .........10
TEMPERATUREREGULATION ................................................ 11
TemperatureAdjustment ................................................ 11
FORYOURINFORMATION ..................................................... 12
ThermalExpansion ......................................................... 12
Strange Sounds ............................................................. 12
OperationalConditions................................................... 12
SmellyWater ..................................................................12
“Air” in Hot Water Faucets.............................................12
High WaterTemperature Shut Off System ....................12
PERIODICMAINTENANCE .......................................................12
Anode Rod Inspection.............................................. 12-13
Temperature-Pressure Relief Valve Operation..............13
Draining ..........................................................................13
Drain Valve Washer Replacement .................................13
Service ...........................................................................13
LEAKAGECHECKPOINTS ......................................................14
REPAIRPARTSLIST ...............................................................15
TROUBLESHOOTING ..............................................................16
WARRANTY ..................................................................... 17-18
TABLE OF CONTENTS

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Thank You for purchasing this water heater. Properly installed and
maintained,itshould give you years of trouble free service.
AbbreviationsFoundInThisInstructionManual:
• ANSI-AmericanNationalStandardsInstitute
• ASME-AmericanSocietyofMechanical Engineers
• GAMA-GasApplianceManufacturer’sAssociation
• NEC-NationalElectricCode
• NFPA- NationalFire ProtectionAssociation
• UL-UnderwritersLaboratory
PREPARING FOR THE INSTALLATION
1. Read the “General Safety” sectionofthismanualfirst and then the
entire manual carefully. If you don’t follow the safety rules, the
water heater will not operate properly. It could cause DEATH,
SERIOUSBODILYINJURYAND/ORPROPERTYDAMAGE.
Thismanual containsinstructions fortheinstallation, operation,and
maintenanceof the electric waterheater. It alsocontainswarnings
throughout the manual that you must read and be aware of. All
warningsand allinstructions areessentialto theproper operationof
thewater heater and your safety. Sincewe cannot put everything
on the first few pages, READ THE ENTIRE MANUAL BEFORE
ATTEMPTINGTOINSTALLOROPERATETHEWATERHEATER.
2. Theinstallation must conformwiththeseinstructionsand the local
codeauthorityhavingjurisdictionandtherequirementsofthepower
company. In the absence of code requirements follow NFPA-70
(latestedition).TheNationalElectricCodewhichmay be ordered
from: National Fire Protection Association, 1 Batterymarch Park,
Quincy,MA02269.
3. If after reading this manual you have any questions or do not
understandany portionofthe instructions, callthe local utilityorthe
manufacturerwhose name appears on theratingplate.
4. Carefullyplantheplace whereyouaregoingtoputthewaterheater.
INSTALLATIONORSERVICEOFTHISWATERHEATERREQUIRES
ABILITYEQUIVALENTTOTHATOFALICENSEDTRADESMANIN
THEFIELDINVOLVED.PLUMBINGANDELECTRICALWORKARE
REQUIRED.
Examinethelocation to ensure the water heater complies withthe
“FactstoConsiderAbouttheLocation” section in thismanual.
5. ForCaliforniainstallationthiswaterheatermustbebraced,anchored,
or strapped to avoid falling or moving during an earthquake. See
instructionsfor correctinstallationprocedures. Instructions maybe
obtained from California Office of the StateArchitect, 400P Street,
Sacramento,CA95814.
6. Massachusetts Code requires this water heater to be installed in
accordancewithMassachusetts248-CMR2.00:StatePlumbingCode
and248-CMR5.00.
INTRODUCTION
NOTES

5
TYPICAL INSTALLATION
FIGURE1.
UPRIGHTS COMPACTS
TABLE TOPS
INSTALL VACUUM RELIEF IN COLD WATER
INLET LINE AS REQUIRED BY LOCAL CODES.
INSTALL SUITABLEDRAINPANS UNDERHEATERS
TOPREVENTDAMAGEDUE TO LEAKAGE.REFER
TO WATER HEATER LOCATION ON PAGE 8.
INSTALL THERMALEXPANSION TANK ORDEVICE
IF WATER HEATER IS INSTALLED IN A CLOSED
WATERSYSTEM.
LOWBOYS

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WIRING DIAGRAMS
TURN OFF THE HEATER ELECTRICALSUPPLY BEFORE SERVICINGANY ELECTRICAL COMPONENTS.
FIGURE2.
A-9
240VOLT“OFFPEAK”NON-SIMULTANEOUS
OPERATION BOTTOMELEMENTONSEPARATE
TIMECLOCKOR “OFFPEAK”METER
C-2
TWOWIRECIRCUITFORSINGLE
ELEMENTHEATERSEQUIPPED
WITHHIGH LIMITCONTROL
A-6
TWOWIRE CIRCUITFOR
NON-SIMULTANEOUSOPERATION,
HASSINGLEHIGH LIMITCONTROL
S-1
THREEWIRECIRCUITFOR
ELECTRICCO.CO-OP
PROGRAMS

7
MIXING VALVE USAGE
FIGURE3.
Water (Potable) Heating: All models are considered suitable for
water(potable)heatingonly. HOTTERWATERCANSCALD:
Water heaters are intended to produce hot water. Water heated to a
temperature which will satisfy space heating, clothes washing, dish
washing,and other sanitizingneedscanscald and permanentlyinjure
you upon contact. Some people are more likely to be permanently
injuredbyhotwaterthanothers. Theseincludetheelderly,children,the
infirm,orphysically/mentallyhandicapped. If anyoneusing hotwater in
yourhomefitsinto oneof thesegroups orif thereisalocalcodeorstate
lawrequiring acertaintemperature wateratthe hotwatertap, thenyou
musttake special precautions. Inadditionto using thelowestpossible
temperaturesetting that satisfies yourhotwaterneeds, a means such
as a *mixing valve, shall be used at the hot water taps used by these
peopleoratthewaterheater. Mixingvalvesareavailablelocalplumbing
contractor. Consult a Qualified Installer or Service Agency. Follow
mixingvalvemanufacturer’sinstructionsforinstallationofthe valves.
Before changing the factory setting on the thermostat, read the
“TemperatureRegulation”section inthis manual.

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FACTSTO CONSIDERABOUT THE LOCATION
Carefullychoose anindoorlocation forthe newwaterheater,because
the placement is a very important consideration for the safety of the
occupants in the building and for the most economical use of the
appliance.
Whetherreplacing an oldwaterheater or putting thewaterheater in a
newlocation,thefollowing critical points must be observed:
1. Select a location indoors as close as practical or centralized
to the water piping system as possible. The water heater
should be located in an area not subject to freezing
temperatures.
2. Selectedlocationmustprovideadequateclearances(4”)forservicing
partssuchasthethermostats,drainvalveandreliefvalve.Adequate
clearancefor servicingthisappliance shouldbeconsidered before
installation,such as changing theanodes,etc.
Installationofthe waterheatermustbeaccomplished insuchamanner
thatifthe tank or any connections should leak,theflowwillnot cause
damagetothe structure. Forthisreason,itisnotadvisable toinstallthe
waterheater inanattic or upperfloor. Whensuchlocations cannot be
avoided,asuitabledrainpanshouldbeinstalledunderthewaterheater.
Drainpansareavailable from your localplumbingcontractor. Sucha
drainpanmusthavea minimum length and width of at least 2 inches
(51mm)greater thatthewaterheaterdimensionsandmust bepipedto
anadequate drain.
LOCATING THE NEW WATER HEATER
Water heater life dependsuponwater quality,waterpressure and the
environmentinwhich the water heater is installed.Waterheatersare
sometimesinstalled inlocationswhere leakage mayresultin property
damage,evenwith the use of a drain panpiped to a drain. However,
unanticipateddamage canbe reducedor preventedbya leakdetector
or water shut-off device used in conjunction with a piped drain pan.
Thesedevices are availablefromsomeplumbing supply wholesalers
andretailers,anddetectandreacttoleakageinvariousways:
• Sensorsmountedinthedrainpan that trigger an alarm or turn off
theincomingwaterto the water heater when leakage is detected.
• Sensorsmountedin the drain pan that turn off the water supplyto
theentirehomewhenwaterisdetectedin the drain pan.
• Water supply shut-off devices that activate based on the water
pressure differential between the cold water and hot water pipes
connectedtothewaterheater.
• Devicesthat will turnoffthe gas supplytoa gaswaterheater while
atthesametimeshuttingoff itswater supply.
INSULATION BLANKETS
Insulationblankets are availabletothe general public forexternaluse
onelectric water heatersbutare not necessarywiththis product. The
purpose of an insulation blanket is to reduce the standby heat loss
encountered with storage tank heaters. Your water heater meets or
exceedstheNationalApplianceEnergyConversationActstandards
withrespecttoinsulationandstandbylossrequirements,makingan
insulationblanket unnecessary.
Should you choose to apply an insulation blanket to this heater, you
should follow these instructions below. Failure to follow these
instructionscanresultin fire, serious personal injury, or death.
•Donotcoverthe temperatureandpressure relief(T& P)valvewith
aninsulationblanket.
•Do not cover the instruction manual. Keep it on the side of the
water heater or nearby for future reference.
•Doobtainnew warning and instructionlabelsforplacement on the
blanketdirectly over theexistinglabels.
INSTALLING THE NEW WATER HEATER
WATER PIPING
HOTTER WATER CAN SCALD:
Water heaters are intended to produce hot water. Waterheated to a
temperature which will satisfy space heating, clothes washing, dish
washing,cleaningandothersanitizingneedscanscaldandpermanently
injureyouuponcontact. Somepeoplearemorelikelytobepermanently
injuredbyhotwaterthanothers. Theseincludetheelderly, children,
the infirm, or physically/mentally handicapped. If anyone using hot
water in your home fits into one of these groups or if there is a local
code or state law requiring a certain temperature water at the hot
watertap, thenyou musttakespecial precautions. Inadditionto using
the lowest possible temperature setting that satisfies your hot water
needs,ameanssuch asa *mixingvalve, shallbeusedatthehotwater
tapsused bythesepeople or at thewaterheater. Valvesfor reducing
pointofusetemperaturebymixingcoldandhotwaterarealsoavailable.
ConsultaQualifiedInstalleror ServiceAgency. Follow manufacturer’s
instructionsfor installation of the valves. Before changingthefactory
settingonthethermostat,readthe“TemperatureRegulation”section in
thismanual.

9
This water heater shall not be connected to any heating systems or
component(s)used with a non-potable water heatingappliance.
Toxicchemicals, such as those used for boiler treatment shall notbe
introducedinto this system.
Water supply systems may, because of such events as high line
pressure, frequent cut-offs, the effects of water hammer among
others,haveinstalled devicessuchaspressurereducingvalves,check
valves,backflow preventers, etc. to control these types of problems.
Whenthesedevicesare notequipped withaninternalby-pass,and no
othermeasuresaretaken, the devices cause the water system to be
closed. Aswaterisheated, itexpands(thermalexpansion)and closed
systems do not allow for the expansion of heated water.
The water within the water heater tank expands as it is heated and
increases the pressure of the water system. If the relieving point of
the water heater’s temperature-pressure relief valve is reached, the
valve will relieve the excess pressure. The temperature-pressure
relief valve is not intended for the constant relief of thermal
expansion. Thisis anunacceptable conditionandmustbecorrected.
It is recommended that any devices installed which could create a
closedsystemhave a by-pass and/or the system have an expansion
tankor devicetorelieve thepressurebuilt by thermalexpansion in the
water system. Expansion tanks are available for ordering through a
local plumbing contractor. Contact the local water supplier and/or a
serviceagencyforassistancein controlling these situations.
NOTE: To protect against untimely corrosion of hot and cold
water fittings, it is strongly recommended that di-electric
unions or couplings be installed on this water heater when
connected to copper pipe.
FIGURE4.
Figure4 shows the typicalattachmentof the water pipingtothe water
heater. The water heater is equipped with 3/4 inch NPT water
connections.
NOTE: If using copper tubing, solder tubing to an adapter
before attaching the adapter to the cold water inlet connection.
Do not solder the cold water supply line directly to the cold
water inlet, it will harm the dip tube and damage the tank.
TEMPERATURE-PRESSURERELIEFVALVE
This heater is provided with a properly certified combination
temperature-pressure relief valve by the manufacturer.
Thevalve iscertifiedby a nationallyrecognizedtesting laboratorythat
maintains periodic inspection of production of listed equipment of
materialsasmeetingtherequirementsforRelief ValvesandAutomatic
Gas Shut-off Devices for Hot Water Supply Systems,ANSI Z21.22 •
CSA4.4,andthe coderequirementsofASME.
Ifreplaced,thevalvemust meet the requirements of local codes, but
not less than a combination temperature and pressure relief valve
certifiedas indicated in the aboveparagraph.
Thevalvemustbemarkedwithamaximumsetpressurenottoexceed
the marked hydrostatic working pressure of the water heater
(150psi= 1,035kPa) anda dischargecapacitynotlessthanthewater
heaterinput rate as shown on themodelratingplate.
For safe operation of the water heater, the relief valve must not be
removedfrom itsdesignatedopening norplugged.
Thetemperature-pressure relief valve must be installed directly into
thefitting ofthewater heaterdesigned fortherelief valve. Positionthe
valve downward and provide tubing so that any discharge will exit
only within 6 inches (153 mm) above, or at any distance below the
structuralfloor. Becertainthatnocontactismadewithanyliveelectrical
part. Thedischargeopening must not be blocked or reduced in size
underany circumstances. Excessive length,over30 feet (9.14m),or
use of more than four elbows can cause restriction and reduce the
dischargecapacityofthe valve.
Novalveorotherobstructionistobeplacedbetweenthe relief valve
andthe tank. Do notconnecttubing directlytodischarge drain unless
a6inchair gap is provided. Topreventbodilyinjury,hazardtolife,or
propertydamage, the relief valve mustbeallowed to discharge water
inquantitiesshould circumstancesdemand. Ifthedischargepipe isnot
connected to a drain or other suitable means, the water flow may
causeproperty damage.

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TheDischargePipe:
• Shallnotbe smaller in size than the outlet pipesizeofthe valve, or
haveanyreducing couplings or other restrictions.
• Shallnot beplugged orblocked.
• Shallbe of material listed for hotwaterdistribution.
• Shall be installed so as to allow complete drainage of both the
temperature-pressurerelief valve, and the dischargepipe.
• Shallterminateatanadequatedrain.
• Shallnothaveanyvalve between the relief valve and tank.
FIGURE5.
Thetemperature-pressurerelief valve must be manually operated at
leastonce ayear. Cautionshouldbe takento ensurethat (1)noone is
infront of oraroundthe outlet ofthe temperature-pressure reliefvalve
dischargeline,and (2) the water manually discharged will not cause
any bodily injury or property damage because the water may be
extremelyhot.
If after manually operating the valve, it fails to completely reset and
continues to release water, immediately close the cold water inlet to
the water heater, follow the draining instructions, and replace the
temperature-pressurerelief valve with a new one.
FILLINGTHE WATERHEATER
Never use this water heater unless it is completely full of water. To
preventdamage to the tank, the tankmust befilledwith water. Water
must flow from the hot water faucet before turning “ON” electrical
supplytothe water heater.
To fill the water heater with water:
1. Closethewaterheaterdrainvalveby turningthe handletothe right
(clockwise). The drain valve is on the lower front of the water
heater.
2. Open the cold water supply valve to the water heater.
NOTE: The cold water supply valve must be left open when
the water heater is in use.
3. To insurecomplete fillingofthe tank,allowairtoexitby openingthe
nearest hot water faucet. Allow water to run until a constant flow
isobtained. Thiswillletairout of the water heater and the piping.
4. Checkallwaterpipingandconnectionsforleaks. Repairasneeded.
FIGURE6.
T&P VALVE and PIPE INSULATION (On Selected Models)
Removeinsulation for T&PValveandpipeconnections from carton.
Fitpipe insulation over the incomingcoldwaterline and the hot water
line.Makesurethattheinsulationisagainstthetopcoveroftheheater.
FitT&PValveinsulationover valve.Makesure thatthe insulationdoes
notinterferewiththeleveroroutletoftheT&Pvalve.
Secureall insulationusingtape.
PIPE INSULATION