AO Smith Water Heater BT 80 User Manual

MODELS BT- 80 AND 100 300/301 SERIES  
COMMERCIAL GAS WATER HEATER  
Glass-Lined Tank-Type Water Heater  
• INSTALLATION • OPERATION • SERVICE • MAINTENANCE • LIMITED WARRANTY  
Thank you for buying this energy efficient water heater from  
A.O. Smith Water Products Company. We appreciate your  
confidence in our products.  
CAUTION  
TEXT IN BLACK BOLD TYPE OR UNDERLINED  
CONTAINS INFORMATION RELATIVE TO YOUR  
SAFETY. PLEASE READ THOROUGHLY BEFORE  
INSTALLING AND USING THIS APPLIANCE.  
McBEE, SOUTH CAROLINA, USA  
www.aosmithwaterheaters.com  
PLACE THESE INSTRUCTIONS ADJACENT TO HEATER  
AND NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.  
PRINTED 0107  
197569-000  
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TABLE OF CONTENTS  
Page  
2
2
Page  
ROUGH-IN DIMENSIONS ...................................................................  
FOREWORD ........................................................................................  
OPERATION ........................................................................................ 9-13  
To Operate The Water Heater .........................................................  
Purging ............................................................................................  
9
9
GENERAL SAFETY INFORMATION ................................................... 3-4  
Precautions .......................................................................................  
Chemical Vapor Corrosion ...............................................................  
Improper Combustion .......................................................................  
3
3
3
Lighting Instructions ........................................................................10-11  
Temperature Regulation .................................................................. 12  
Check Venting ................................................................................. 12-13  
High Temperature Limit Switch ....................................................... 13  
SERVICE INFORMATION ...................................................................13-14  
Pilot and Main Burner ...................................................................... 13  
Checking Gas Input .........................................................................13-14  
Vent System .................................................................................... 14  
Relief Valve ...................................................................................... 14  
Hot Water Odor ............................................................................... 14  
Anode Rod Inspection ..................................................................... 14  
Winter Protection ............................................................................. 14  
Replacement Parts .......................................................................... 14  
PREVENTIVE MAINTENANCE ..........................................................15-16  
Recommended Procedure For Periodic Removal Of Lime  
Liquid Petroleum Models .................................................................. 3-4  
Extended Non-use Periods ..............................................................  
Insulation Blankets ...........................................................................  
Circulating Pump ..............................................................................  
INSTALLATION INSTRUCTIONS ........................................................ 4-9  
Required Ability.................................................................................  
Locating The Heater ......................................................................... 4-5  
High Altitude Installations .................................................................  
Clearances .......................................................................................  
Hard Water .......................................................................................  
Air Requirements.............................................................................. 5-6  
Water (Potable) Heating and Space Heating ...................................  
Venting .............................................................................................. 6-7  
4
4
4
4
5
5
5
6
Deposits From Tank Type Commercial Water Heaters .................. 15  
Deliming Solvents ............................................................................ 15  
Tank Cleanout Procedure ................................................................15-16  
CHECKLIST.........................................................................................16-17  
LIMITED WARRANTY .......................................................................... 18  
Thermometers (Not Supplied) ..........................................................  
Relief Valve .......................................................................................  
Gas Piping ........................................................................................ 8-9  
7
7
Gas Pressure Regulator ...................................................................  
9
IMPROPER COMBUSTION  
GENERAL SAFETY  
INFORMATION  
WARNING  
ATTICAND/OR EXHAUST FANS OPERATING ON THE PREMISES  
WITHAWATER HEATER CAN RESULT IN CARBON MONOXIDE  
POISONING AND DEATH.  
PRECAUTIONS  
DO NOT USE THISAPPLIANCE IFANY 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.  
OPERATION OF THESE FANS CAN PRODUCE A NEGATIVE  
DRAFT IN THE AREA OF THE WATER HEATER PREVENTING  
THE PRODUCTS OF COMBUSTION FROM EXHAUSTING  
THROUGH THE CHIMNEY OR VENT PIPE.  
IF THE UNIT IS EXPOSED TO THE FOLLOWING, DO NOT  
OPERATE HEATER UNTILALLCORRECTIVE STEPS HAVE BEEN  
MADE BY A QUALIFIED SERVICEMAN.  
The venting of the water heater should be inspected by a qualified  
service technician at the time of installation and periodically thereafter  
to ensure a down-draft condition does not exist.  
1. EXTERNAL FIRE.  
2. DAMAGE.  
DO NOT OBSTRUCT THE FLOW OF COMBUSTION AND  
VENTILATING AIR. ADEQUATE AIR FOR COMBUSTION AND  
VENTILATION MUST BE PROVIDED FOR SAFE OPERATION.  
3. FIRING WITHOUT WATER.  
4. SOOTING  
LIQUID PETROLEUM MODELS  
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.  
CHEMICAL VAPOR CORROSION  
WARNING  
CORROSION OF THE FLUEWAYS AND VENT SYSTEM MAY  
OCCUR IF AIR FOR COMBUSTION CONTAINS CERTAIN LP gas must be used with great caution. It is highly explosive  
CHEMICAL VAPORS. SUCH CORROSION MAY RESULT IN  
FAILURE AND RISK OF ASPHYXIATION.  
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.  
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.  
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  
If necessary, uncontaminated air should be obtained from remote gives LP gas its distinctive smell. Another cause can be your  
or outside sources. The limited warranty is voided when failure of physical condition, such as having a cold or diminishing sense  
of smell with age. For these reasons, the use of a propane gas  
detector is recommended.  
water heater is due to a corrosive atmosphere. (Refer to the limited  
warranty for complete terms and conditions.)  
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IF YOU EXPERIENCEAN OUT-OF-GAS SITUATION, DO NOT TRY  
TO RELIGHTAPPLIANCESYOURSELF, 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 INSTRUCTIONS  
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 WORK ARE REQUIRED.  
EXTENDED NON-USE PERIODS  
WARNING  
HYDROGEN GAS CAN BE PRODUCED IN A HOT WATER  
SYSTEM SERVED BYTHIS 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 these conditions, it is recommended  
that the hot 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 SMOKING OR OPEN FLAME NEAR  
THE FAUCET AT THE TIME IT IS OPEN.  
GENERAL  
The heater is designed to operate on natural or propane gases.  
HOWEVER, MAKE SURE the gas on which the heater will operate  
is the same as that specified on the heater model and rating plate.  
LOCATING THE HEATER  
When installing the heater, consideration must be given to proper  
location. Location selected should be as close to the stack or  
chimney as practicable, with adequate air supply and as centralized  
with the piping system as possible.  
INSULATION BLANKETS  
Insulation blankets available to the general public for external use  
on gas water heaters are not approved for use on your A.O. Smith  
water heater. 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  
ASHRAE/IES 90.1b-1999 standards with respect to insulation and  
standby loss requirement making an insulation blanket unnecessary.  
WARNING  
THERE ISARISK IN USING FUEL BURNINGAPPLIANCES SUCH  
AS GAS WATER HEATERS IN ROOMS, GARAGES OR OTHER  
AREAS WHERE GASOLINE, OTHER FLAMMABLE LIQUIDS OR  
ENGINE DRIVEN EQUIPMENT OR VEHICLES ARE STORED,  
OPERATED OR REPAIRED. FLAMMABLE VAPORSARE HEAVY  
AND TRAVELALONG THE FLOORAND MAY BE IGNITED BY THE  
HEATER’S PILOT OR MAIN BURNER FLAMES CAUSING FIRE  
OR EXPLOSION. SOME LOCAL CODES PERMIT OPERATION  
OF GAS APPLIANCES IF INSTALLED 18" (46CM) OR MORE  
ABOVE THE FLOOR. THIS MAY REDUCE THE RISK IF LOCATION  
IN SUCH AN AREA CANNOT BE AVOIDED.  
WARNING  
Should you choose to apply an insulation blanket to this heater,  
you should follow these instructions. Failure to follow these  
instructions can result in fire, asphyxiation , serious personal  
injury or death.  
DO NOT INSTALL THIS WATER HEATER DIRECTLY ON A  
CARPETED FLOOR. A FIRE HAZARD MAY RESULT. Insteadthe  
water heater must be placed on a metal or wood panel extending  
beyond the full width and depth by at least 3" (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 the drain  
requirements.  
Do not apply insulation to the top of the water heater, as  
this will interfere with safe operation of the draft hood.  
Do not cover the outer door, thermostat or temperature &  
pressure relief valve.  
Do not allow insulation to come within 2" (5cm) of the floor  
to prevent blockage of combustion air flow to the burner.  
THIS HEATER SHALL BE LOCATED OR PROTECTED SO IT IS  
NOT SUBJECT TO PHYSICAL DAMAGE BY A MOVING VEHICLE.  
Do not cover the instruction manual. Keep it on the side of  
the water heater or nearby for future reference.  
WARNING  
FLAMMABLE ITEMS, PRESSURIZED CONTAINERS OR ANY  
OTHER POTENTIAL FIRE HAZARDOUS ARTICLES MUST  
NEVER BE PLACED ON OR ADJACENT TO THE HEATER. OPEN  
CONTAINERS OF FLAMMABLE MATERIAL SHOULD NOT BE  
STORED OR USED IN THE SAME ROOM WITH THE HEATER.  
Do obtain new warning and instruction labels fromA.O. Smith  
for placement on the blanket directly over the existing labels.  
Do inspect the insulation blanket frequently to make certain  
it does not sag, thereby obstructing combustion air flow.  
THE HEATER MUST NOT BE LOCATED IN AN AREA WHERE IT  
WILL BE SUBJECT TO FREEZING.  
CIRCULATING PUMP  
THE HEATER SHOULD BE LOCATED IN AN AREA WHERE  
LEAKAGE FROM THE HEATER OR CONNECTIONS WILL NOT  
RESULT IN DAMAGE TO THE ADJACENT AREA OR TO LOWER  
FLOORS OF THE STRUCTURE.  
A circulating pump is used when a system requires a circulating  
loop or there is a storage tank used in conjunction with the heater.  
Install the system in accordance with the current edition of the  
National Electrical Code ANSI/NFPA No. 70 or the Canadian  
Electrical Code CSA C22.1.  
WHEN SUCH LOCATIONS CANNOT BE AVOIDED, A SUITABLE  
DRAIN PAN SHOULD BE INSTALLED UNDER THE HEATER.  
Such pans should be fabricated with sides at least 2" (5cm) deep,  
Only all bronze circulators are used with commercial water heaters.  
Although circulators are oiled and operated by the manufacturer with length and width at least 2" (5cm) greater than the diameter of  
some circulators must be oiled again before operating. Please refer the heater and must be piped to an adequate drain. The pan must  
to manufacturer’s instructions.  
not restrict combustion air flow.  
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specified on the heater rating plate is not permitted.  
Drain pans suitable for these heaters are available from your  
distributor or A. O. Smith Water Products Company, 500 Tennessee  
Waltz Parkway, Ashland City, TN 37015.  
The input reduction is primarily achieved by reducing the size of  
the main burner orifices. To do this, the main burner orifices require  
replacement with orifices sized for the particular installation  
elevation. Correct orifice sizing and parts may be obtained from  
A.O. Smith Water Products Company. When ordering, be sure to  
state the model number and the altitude of the location where the  
water heater is being installed.  
Water heater life depends upon water quality, water pressure and the  
environment in which the water heater is installed. Water heaters are  
sometimes installed in locations where leakage may result in property  
damage, even with the use of a drain pan piped to a drain. However,  
unanticipated damage can be reduced or prevented by a leak detector  
or water shutoff device used in conjunction with a piped drain pan.  
These devices are available from some plumbing supply wholesalers  
and retailers, and detect and react to leakage in various ways:  
Upon completion of derating of the heater, adjustment to the gas  
pressure regulator may be required. See CHECKING THE INPUT  
section in this manual for inlet and manifold pressure requirements.  
Sensors mounted in the drain pan that trigger an alarm or turn off  
the incoming water to the water heater when leakage is detected.  
Sensors mounted in the drain pan that turn off the water supply  
to the entire home when water is detected in the drain pan.  
Water supply shutoff devices that activate based on the water  
pressure differential between the cold water and hot water pipes  
connected to the water heater.  
Also due to the input rating reduction required at high altitudes, the  
recovery rating of the appliance is also reduced and should be  
compensated for in the sizing of the equipment for application.  
CLEARANCES  
Devices that will turn off the gas supply to a gas water heater These heaters are approved for installation on combustible flooring  
while at the same time shutting off its water supply.  
in a closet having a ceiling 12" (30.5cm) above top cover and with  
clearances to combustible construction of 6" (15.2cm) from flue or  
For appliance installation locations with elevations above 2000' vent connector, 0" (0cm) at the sides and rear and 4" (10.1cm) to  
(610m), refer to HIGH ALTITUDE INSTALLATIONS section of this front to prevent a possible fire hazard condition. A minimum of 4"  
manual for input reduction procedure.  
(10.1cm) shall be allowed for installation of serviceable parts.  
HARD WATER  
HIGH ALTITUDE INSTALLATIONS  
Where hard water conditions exist, water softening or the threshold type  
of water treatment is recommended. This will protect the dishwashers,  
coffee urns, water heaters, water piping and other equipment.  
WARNING  
INSTALLATIONSABOVE 2000' (610m) REQUIRE REPLACEMENT  
OF THE BURNER ORIFICE IN ACCORDANCE WITH SECTION  
8.1.2 OF THE NATIONAL FUEL GAS CODE (ANSI Z223.1). FOR  
CANADIAN INSTALLATIONS CONSULT THE NATURAL GASAND  
PROPANE INSTALLATION CODE CAN/CSA-B149.1. FAILURE TO  
REPLACE THE ORIFICE WILL RESULT IN IMPROPER AND  
INEFFICIENT OPERATION OF THE APPLIANCE RESULTING IN  
THE PRODUCTION OF INCREASED LEVELS OF CARBON  
MONOXIDE GAS IN EXCESS OF SAFE LIMITS WHICH COULD  
RESULT IN SERIOUS PERSONAL INJURY OR DEATH.  
See PREVENTIVE MAINTENANCE section for details of tank  
cleanout procedure.  
AIR REQUIREMENTS  
REFER TO THE CURRENT EDITION OF THE NATIONAL FUEL  
GAS CODE ANSI Z223.1/NFPA 54.  
You should contact your gas supplier for any specific changes which  
may be required in your area.  
KEEP APPLIANCEAREA CLEARAND FREE OF COMBUSTIBLE  
MATERIALS, GASOLINEAND OTHER FLAMMABLES, VAPORS  
AND LIQUIDS.  
As elevation above sea level is increased, there is less oxygen per  
cubic foot of air. Therefore, the heater input rate should be reduced  
at high altitudes for satisfactory operation with the reduced oxygen  
supply. Failure to make this reduction would result in an overfiring  
of the heater causing sooting, poor combustion and/or unsatisfactory  
heater performance.  
DO NOT OBSTRUCT THE FLOW OF COMBUSTION OR  
VENTILATING AIR.  
WARNING  
FOR SAFE OPERATION PROVIDE ADEQUATE AIR FOR  
COMBUSTIONAND VENTILATION. AN INSUFFICIENT SUPPLYOF  
AIR WILLCAUSE RECIRCULATION OF COMBUSTION PRODUCTS  
RESULTING INAIR CONTAMINATION THAT MAY BE HAZARDOUS  
TO LIFE. SUCHACONDITION OFTEN WILL RESULT INAYELLOW,  
LUMINOUSBURNERFLAME, CAUSINGCARBONINGORSOOTING  
OF THE COMBUSTION CHAMBER, BURNERS AND FLUE TUBES  
AND CREATES A RISK OF ASPHYXIATION.  
U.S. REQUIREMENTS  
Ratings specified by manufacturers for most appliances apply for  
elevations up to 2000 feet (610m). For elevations above 2000 feet  
(610m), ratings must be reduced at the rate of 4% for each 1000 feet  
(305m) above sea level. For example, if a heater is rated at 75,100  
Btu/Hr (22.0 kW) at sea level, to rate the heater at 4000 feet (1219m),  
you subtract 4 (once for each thousand feet) x 0.04 (4% input  
reduction) x 75,100 Btu/Hr (original rating) from the original rating.  
Therefore, to calculate the input rating at 4000 feet (1219m): 4 x 0.04  
x 75,100 Btu/Hr = 12,016 Btu/Hr (3.5 kW); 75,100 Btu/Hr (22.0 kW) -  
12,016 Btu/Hr (3.5 kW) = 63,084 Btu/Hr (18.5 kW). At 6000 feet  
(1829m) the correct input rating should be 57,076 Btu/Hr (16.7 kW).  
Where an exhaust fan is supplied in the same room with a heater,  
sufficient openings for air must be provided in the walls.  
UNDERSIZED OPENINGS WILL CAUSEAIR TO BE DRAWN INTO  
THE ROOM THROUGH THE CHIMNEY, CAUSING POOR  
COMBUSTION. SOOTING MAY RESULT IN SERIOUS DAMAGE  
TO THE HEATER AND RISK OF FIRE OR EXPLOSION.  
CANADIAN REQUIREMENTS  
Appliances with inputs up to and including 400,000 BTU (117.1 kwh)  
must be factory equipped with orifices for operation at specific  
elevations. Standard (sea level) orifices permit operation up to 2000'  
(610m) elevation. For operation between 2000' (610m) and 4500'  
(1370m) specify "HIGHALTITUDE OPERATION" when ordering the  
heater(s). For operation above 4500' (1370m) consult factory before  
ordering. Field conversion for operation at altitudes other than that  
UNCONFINED SPACE  
In buildings of conventional frame, brick, or stone construction,  
unconfined spaces may provide adequate air for combustion,  
ventilation and draft hood dilution.  
If the unconfined space is within a building of tight construction  
(buildings using the following construction: weather stripping, heavy  
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insulation, caulking, vapor barrier, etc.), air for combustion, ventilation  
and draft hood dilution must be obtained from outdoors. The  
installation instructions for confined spaces in tightly constructed  
buildings must be followed to ensure adequate air supply.  
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.  
CONFINED SPACE  
When drawing combustion and dilution air from inside a  
conventionally constructed building to a confined space, such a  
space shall be provided with two permanent openings, ONE IN OR  
WITHIN 12 " (305mm) OF THE ENCLOSURE TOP AND ONE IN  
OR WITHIN 12" (305mm) OF THE ENCLOSURE BOTTOM. Each  
opening shall have a free area of at least one square inch per 1000  
This water heater must be vented in compliance with all local codes,  
the current edition of the National Fuel Gas Code ANSI-Z223.1 or  
the Natural Gas and Propane Installation Code CAN/CSA-B149.1.  
If any part of the vent system is exposed to ambient temperatures  
Btu/Hr (2203mm2/kW) of the total input of all appliances in the below 35° F (2° C) it must be insulated to prevent condensation.  
enclosure, but not less than 100 square inches (645cm2).  
Do not connect the heater to a common vent or chimney with any  
oil-fired or solid fuel burning equipment. This practice is prohibited  
by many local building codes as is the practice of venting gas  
If the confined space is within a building of tight construction, air  
for combustion, ventilation, and draft hood dilution must be obtained  
from outdoors. When directly communicating with the outdoors or  
communicating with the outdoors through vertical ducts, two  
permanent openings, located in the above manner, shall be  
provided. Each opening shall have a free area of not less than  
one square inch per 4000 Btu/Hr (551mm2/kW) of the total input of  
all appliances in the enclosure. If horizontal ducts are used, each  
opening shall have a free area of not less than one square inch  
per 2000 Btu/Hr (1102mm2/kW) of the total input of all appliances  
in the enclosure.  
fired equipment to the duct work of ventilation systems.  
WATER (POTABLE) HEATING AND SPACE  
HEATING  
FIGURE 2.  
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, see Figure 4.  
DRAFT HOOD  
The draft hood furnished with this heater must be installed without  
alteration. Provision must be made if it is installed in confined space  
or a small room to accommodate draft hood spillage and avoid risks  
described in previous steps. The upper air opening called for in the  
AIR REQUIREMENTS section of this manual is for this purpose.  
Locate the 3 brackets and 6 screws in the installation instruction bag.  
Secure each bracket to the draft hood leg with the screws furnished.  
Place the draft hood on the water heater so that legs of the draft hood  
fit into the slots on the jacket top, see Figure 3. Once the draft hood  
(with brackets attached) is in place, drill a small pilot hole through  
bracket hole into the jacket top. WARNING, DO NOT PENETRATE  
THE JACKET TOP BY MORE THAN 1/4". Secure the brackets to  
the jacket top with the screws furnished, see Figure 3.  
CAUTION  
A closed system will exist if a check valve (without bypass),  
pressure reducing valve (without bypass), or a water meter  
(without bypass) is installed in the cold water line between the  
water heater and street main (or well).  
Excessive pressure may develop in such closed systems,  
causing premature tank failure or intermittent relief valve  
operation. This is not a warranty failure. An expansion tank or  
a similar device is required in the inlet supply line between the  
appliance and the meter or valve to compensate for the thermal  
expansion of the water.  
SYSTEM CONNECTIONS  
The system installation must conform to these instructions and to  
the local code authority having jurisdiction. Good practice requires  
that all heavy piping be supported.  
VENTING  
WARNING  
THE INSTRUCTIONS IN THIS SECTION ON VENTING MUST  
BE FOLLOWED TO AVOID CHOKED COMBUSTION OR  
RECIRCULATION OF FLUE GASES. SUCH CONDITIONS CAUSE  
SOOTING OR RISKS OF FIRE AND ASPHYXIATION.  
FIGURE 3.  
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VENT CONNECTION  
installed with a properly sized, rated and approved combination  
temperature (ANSI) and pressure (ASME) relief valve(s).  
Vent connections must be made to an adequate stack or chimney.  
Size and install proper size vent pipe. Do not reduce pipe size to  
less than that of the draft hood outlet.  
WARNING  
THE PURPOSE OF RELIEF VALVE IS TO AVOID EXCESSIVE  
PRESSURE OR TEMPERATURE INTO THE STEAM RANGE,  
WHICH MAY CAUSE SCALDING AT FIXTURES, TANK  
EXPLOSION, SYSTEM OR HEATER DAMAGE. NO VALVE IS TO  
BE PLACED BETWEEN THE RELIEF VALVE AND TANK.  
Horizontal runs of vent pipe must have a minimum upward slope  
toward the chimney of 1/4 inch per foot. Dampers or other  
obstructions must not be installed in between the heater and the  
draft hood. Be sure that the vent pipe does not extend beyond the  
inside wall of the chimney.  
Your local code authority may have other specific relief valve  
requirements.  
Where a continuous or intermittent back draft is found to exist, the  
cause must be determined and corrected. A special vent cap may  
be required. If the back draft cannot be corrected by the normal  
methods or if a suitable draft cannot be obtained, a blower type flue  
gas exhauster must be employed to assure proper venting and  
correct combustion.  
A DRAIN LINE MUST BE CONNECTED TO THE RELIEF VALVE  
TO DIRECT DISCHARGE TO A SAFE LOCATION TO AVOID  
SCALDING OR WATER DAMAGE. THIS LINE MUST NOT BE  
REDUCED FROM THE SIZE OF THE VALVE OUTLET AND MUST  
NOT CONTAIN VALVES, RESTRICTIONS NOR SHOULD IT BE  
LOCATED IN FREEZINGAREAS. DO NOT THREAD OR CAP THE  
END OF THIS LINE. RESTRICTED OR BLOCKED DISCHARGE  
WILL DEFEAT THE PURPOSE OF THE VALVE AND IS UNSAFE.  
DISCHARGE LINE SHALLBE INSTALLED TOALLOW COMPLETE  
DRAINAGE OF BOTH THE VALVE AND LINE.  
THERMOMETERS (Not Supplied)  
Thermometers should be obtained and field installed as shown,  
see Figure 4.  
Thermometers are installed in the system as a means of detecting  
the temperature of the outlet water supply.  
See SERVICE INFORMATION section for procedure and  
precautions.  
RELIEF VALVE  
The type, size and location of the relief valves must be in accordance  
with local codes. The locations of the relief valves shown in the  
installation diagrams are typical. The heater has a factory installed  
high temperature limit switch.  
This water heater is equipped with a combination temperature-  
pressure relief valve that complies with the standard for relief valves  
for hot water supply system, ANSI Z21.22/CSA 4.4. FOR SAFE  
OPERATION OF THE WATER HEATER, THE RELIEF VALVE(S)  
MUST NOT BE REMOVED OR PLUGGED.  
For circulating heaters, the separate storage vessel must have a  
temperature and pressure relief valve installed. This valve shall  
comply with the standard for relief valves and automatic gas shutoff  
devices for hot water supply systems.  
ASME ratings cover pressure relief capacities. ANSI ratings cover  
release rate with temperature actuation.  
Cold water inlet lines to heater should be installed as shown in  
order to minimize gravity circulation of hot water to building cold  
water lines.  
In addition to the appliance relief valve, each remote storage tank  
which may be used in conjunction with this appliance shall also be  
MIXING VALVE APPLICATION  
FOR TWO TEMPERATURE WATER  
SINGLE TEMPERATURE  
INSERT B - VACUUM  
RELIEF VALVE  
*INSTALL PER  
LOCAL CODES  
INSTALL THERMAL EXPANSION  
TANK OR DEVICE IF CHECK VALVE  
OR PRESSURE REDUCING  
CIRCULATING RETURN LINE CONNECTIONS  
TEMPERED WATER LOOP, IF USED, CONNECT TO POINT  
"A". STORED TEMPERATURE WATER LOOP, IF USED,  
CONNECT TO COLD WATER INLET.  
VALVE IS USED IN SUPPLY  
WARNING  
TURE SETTING SHOULD NOT EXCEED SAFE  
MPERATURE AT  
FIXTURES,  
SEE  
CAUTION: IF BUILDING COLD WATER SUPPLYHASABACK-  
FLOW PREVENTER, CHECK VALVE OR WATER METER  
WITH CHECK VALVE, PROVISIONS FOR THERMAL  
EXPANSION OF WATER IN THE HOT WATER SYSTEM MUST  
BE PROVIDED.  
TURE REGULATION ON PAGE 12. IF HIGHER  
TEMPERATURES ARE NECESSARY TO  
DEQUATE BOOSTER OUTPUT, ADD ANANTI-  
ALVE FOR HOT WATER SUPPLIED TO  
FIXTURES.  
FIGURE 4  
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IT IS IMPORTANT TO GUARD AGAINST GAS VALVE FOULING  
FROM CONTAMINANTS IN THE GAS WAYS. SUCH FOULING  
MAY CAUSE IMPROPER OPERATION, FIRE OR EXPLOSION.  
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.  
IF COPPER SUPPLY LINES ARE USED THEY MUST BE  
INTERNALLY TINNED AND CERTIFIED FOR GAS SERVICE.  
BEFORE ATTACHING THE GAS LINE, BE SURE THAT ALL GAS  
PIPE IS CLEAN ON THE INSIDE.  
Size the main gas line in accordance with Table 1. The figures 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 current editions of the National Fuel Gas  
Code or Natural Gas and Propane Installation Code.  
TO TRAPANY DIRT OR FOREIGN MATERIAL IN THE GAS SUPPLY  
LINE,ADIRT LEG (SOMETIMES CALLED SEDIMENT TRAPOR DRIP  
LEG) MUST BE INCORPORATED IN THE PIPING (SEE FIG. 5). THE  
DIRT LEG MUST BE READILY ACCESSIBLE AND NOT SUBJECT  
TO FREEZING CONDITIONS. INSTALL IN ACCORDANCE WITH  
RECOMMENDATIONS OF SERVING GAS SUPPLIERS. REFER TO  
THE CURRENT EDITION OFTHENATIONALFUEL GAS CODE OR  
NATURAL GAS AND PROPANE INSTALLATION CODE.  
WARNING  
THE HEATER IS NOT INTENDED FOR OPERATION AT HIGHER  
THAN 14.0" W.C.(3.48 kPa) - NATURAL GAS OR 14.0" W.C. (3.48  
kPa) PROPANE GAS SUPPLY PRESSURE. EXPOSURE TO  
HIGHER SUPPLYPRESSURE MAY CAUSE DAMAGE TO THE GAS  
VALVE WHICH COULD RESULT IN FIRE 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 REGULATORSAND THE  
SAFETY VENT VALVESARE PROTECTEDAGAINST BLOCKAGE.  
THESE ARE PARTS OF THE GAS SUPPLY SYSTEM, NOT THE  
HEATER. VENT BLOCKAGE MAY OCCUR DURING ICE STORMS.  
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 first two  
threads. Use compounds resistant to the action of liquefied  
petroleum gases.  
BEFORE PLACING THE HEATER IN OPERATION, CHECK FOR  
GAS LEAKAGE. Use soap and water solution or other material  
acceptable for the purpose in locating the leaks. DO NOT USE  
MATCHES, CANDLES, FLAME OR OTHER SOURCES OF  
IGNITION FOR THIS PURPOSE.  
TABLE 1 - GAS SUPPLY LINE SIZES (IN INCHES)*  
MAXIMUM CAPACITY OF PIPE IN  
CUBIC FEET PER HOUR  
DISCONNECT THE HEATER AND ITS MANUAL GAS SHUTOFF  
VALVE FROM THE GAS SUPPLY PIPING SYSTEM DURING ANY  
SUPPLY PRESSURE TESTING EXCEEDING 1/2 PSIG (3.45 kPa).  
GAS SUPPLY LINE MUST BE CAPPED WHEN DISCONNECTED  
FROM THE HEATER FOR TEST PRESSURES OF 1/2 PSIG (3.45  
kPa) OR LESS. THEAPPLIANCE NEED NOT BE DISCONNECTED,  
BUT MUST BE ISOLATED FROM THE SUPPLY PRESSURE TEST  
BY CLOSING THE MANUAL GAS SHUTOFF VALVE.  
LENGTH  
IN  
NOMINAL IRON PIPE SIZES (INCHES)  
INPUT IN THOUSANDS (BTU/HR)  
3"  
175 360 680 1400 2100 3960 6300 11000 23000  
120 250 465 950 1460 2750 4360 7700 15800  
FEET 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2"  
10  
20  
30  
40  
50  
60  
70  
80  
4"  
97 200 375 770  
82 170 320 660  
73 151 285 580  
66 138 260 530  
61 125 240 490  
57 118 220 460  
53 110 205 430  
50 103 195 400  
44 93 175 360  
40 84 160 325  
37 77 145 300  
35 72 135 280  
1180 2200 3520 6250 12800  
990 1900 3000 5300 10900  
900 1680 2650 4750 9700  
810 1520 2400 4300 8800  
750 1400 2250 3900 8100  
690 1300 2050 3700 7500  
650 1220 1950 3450 7200  
620 1150 1850 3250 6700  
550 1020 1650 2950 6000  
500 950 1500 2650 5500  
460 850 1370 2450 5000  
430 800 1280 2280 4600  
90  
100  
125  
150  
175  
200  
LENGTH  
IN  
NOMINAL IRON PIPE SIZES (INCHES)  
INPUT IN KW  
METERS 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2"  
3"  
4"  
3
6
9
51 105 199 410  
35 73 142 278  
28 59 110 225  
24 50 94 193  
21 44 83 170  
19 40 76 155  
18 37 70 143  
17 35 64 135  
16 32 60 126  
15 30 57 117  
13 27 51 105  
615 1160 1845 3221 6735  
428 805 1277 2255 4626  
346 644 1031 1830 3748  
12  
15  
18  
21  
24  
27  
31  
38  
46  
53  
61  
290 556  
264 492  
237 445  
220 410  
202 381  
190 357  
182 337  
161 299  
146 278  
135 249  
126 234  
878 1552 3192  
776 1391 2840  
703 1259 2577  
FIGURE 5 - GAS PIPING AND DIRT LEG INSTALLATION  
GAS METER SIZE  
659  
1142 2372  
600 1083 2196  
571 1010 2108  
542  
483  
439  
401  
375  
952 1962  
864 1757  
776 1610  
717 1464  
688 1347  
Be sure the gas meter has sufficient capacity to supply the full  
rated gas input of the water heater as well as the requirements of  
all other gas fired equipment supplied by the meter. If gas meter  
is too small, ask the gas company to install a larger meter having  
adequate capacity.  
12 25 47  
11 23 42  
10 21 40  
95  
88  
82  
8
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individual any questions which he may have in regard to the  
operation and maintenance of the unit.  
WARNING  
DO NOT ATTEMPT TO OPERATE WATER HEATER WITH COLD  
WATER INLET VALVE CLOSED.  
NEVER OPERATE THE HEATER WITHOUT FIRST BEING  
CERTAIN IT IS FILLED WITH WATERANDATEMPERATUREAND  
PRESSURE RELIEF VALVE IS INSTALLED IN THE RELIEF VALVE  
OPENING OF THE HEATER. DO NOT ATTEMPT TO OPERATE  
HEATER WITH COLD WATER INLET VALVE CLOSED.  
TO OPERATE THE WATER HEATER  
1. Close the heater drain valve by turning handle clockwise  
.
2. Open a nearby hot water faucet to permit the air in the system  
to escape.  
3. Fully open the cold water inlet pipe valve allowing the heater  
and piping to be filled.  
FIGURE 6-THERMOSTAT FOR NATURAL AND  
PROPANE GASES  
4. Close the hot water faucet as water starts to flow.  
5. The heater is ready to be operated.  
GAS PRESSURE REGULATOR  
The gas pressure regulator is built into the gas valve and is equipped  
to operate on the gas specified on model and rating plate. The  
regulator is factory adjusted to deliver gas to burner at correct water  
column pressure allowing for a nominal pressure drop through the  
controls.  
A checklist is included in the SERVICE INFORMATION section of  
this manual. By using this checklist the user may be able to make  
minor operational adjustments and save himself unnecessary  
service calls. However, the user should not attempt repairs which  
are not listed in this section.  
The minimum gas supply pressure for input adjustment must not be  
less than 5.0" W.C. (1.24 kPa) for natural gas and 11.0" W.C. (2.74  
kPa) for propane gas.  
PURGING  
Do not subject the combination gas valve to inlet gas  
pressures of more than 14.0" w.c. (3.48 kPa). A service regulator is  
necessary if higher gas pressures are encountered.  
Gas line purging is required with new piping or systems in which air  
has entered.  
Gas pressure specified in Table 2, refer to flow pressure taken at  
pressure tap of automatic gas valve while heater is operating.  
CAUTION  
PURGING SHOULD BE PERFORMED BY PERSONS  
EXPERIENCED IN THIS TYPE GAS SERVICE. TO AVOID RISK  
OF FIRE OR EXPLOSION, PURGE DISCHARGE MUST NOT  
ENTER CONFINEDAREAS OR SPACES WHERE IGNITION CAN  
OCCUR. THE AREA MUST BE WELL VENTILATED AND ALL  
SOURCES OF IGNITION MUST BE INACTIVATED OR REMOVED.  
OPERATION  
It is recommended that a qualified person perform the initial firing of  
the heater. At this time the user should not hesitate to ask the  
TABLE 2.  
MANIFOLD PRESSURE SETTING  
Model  
Number  
BT-80  
Type of  
Gas  
Manifold  
Pressure  
Input  
Natural  
75,100 Btu/Hr  
75,100 Btu/Hr  
75,100 Btu/Hr  
75,100 Btu/Hr  
22 kW  
22 kW  
22 kW  
22 kW  
4.0 in. W.C.  
1.0 kPa  
2.5 kPa  
1.0 kPa  
2.5 kPa  
BT-80  
BT-100  
BT-100  
Propane  
Natural  
10.0 in. W.C.  
4.0 in. W.C.  
10.0 in. W.C.  
Propane  
9
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FOR YOUR SAFETY READ BEFORE LIGHTING  
WARNING: If you do not follow these instructions exactly, a fire or  
explosion may result causing property damage, personal injury or loss of life.  
BEFORE LIGHTING: ENTIRE SYSTEM MUST BE FILLED WITH WATER AND AIR PURGED AT FAUCETS.  
A. This appliance has a pilot which must be lighted by  
hand. When lighting the pilot, follow these  
instructions exactly.  
If you cannot reach your gas supplier, call the  
fire department.  
B. BEFORE LIGHTING: 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.  
WHAT TO DO IF YOU SMELL GAS  
C. Use only your hand to push down or turn the gas  
control knob. Never use tools. If the knob will not  
push down or turn by hand, don’t try to repair it, call  
a qualified service technician. Force or attempted  
repair may result in a fire or explosion.  
Do not try to light any appliance.  
Do not touch any electric switch; do not use any  
phone in your building.  
D. Do not use this appliance if any part has been under  
water. Immediately contact a qualified installer or  
service agency to replace a flooded water heater.  
Do not attempt to repair the unit! It must be replaced!  
Immediately call your gas supplier from a  
neighbor’s phone. Follow the gas supplier’s  
instructions.  
LIGHTING INSTRUCTIONS  
GAS CONTROL  
TOP VIEW  
FIGURE “D”  
1.  
STOP! Read the safety information above on  
this label.  
down. Immediately light the pilot with a match.  
Continue to hold the gas control knob down for about  
one (1) minute after the pilot is lit. Release the gas  
control knob and it will pop back up. Pilot should  
remain lit. If it goes out, repeat Steps 3 through 8. It  
may take several minutes for air to clear the lines,  
before the pilot will light.  
2. Set the thermostat to the lowest setting by turning  
thermostat dial fully clockwise until it stops.  
3. Push the gas control knob down slightly and turn  
clockwise to "OFF". (Figure A).  
NOTE: Gas control knob CANNOT be turned from  
"PILOT" to "OFF" unless it is pushed down slightly.  
Do not force.  
If knob does not pop up when released, stop  
and immediately call your service technician  
or gas supplier.  
4. Remove the inner and outer burner doors located  
below and behind the gas control unit.  
5. Wait five (5) minutes to clear out any gas. If you then  
If the pilot will not stay lit after several tries, turn  
the gas control knob to "OFF" (Figure A) and call  
your service technician or gas supplier.  
smell gas  
information  
STOP! Follow "B" in the safety  
above on this label. If you do not  
9. Replace inner and outer burner doors.  
10. At arm's length away, turn gas control knob  
smell gas, go to the next step.  
counterclockwise  
to on. (Figure C).  
6. Find Pilot: Follow metal tube from the bottom , right  
of the gas control to the pilot burner. (Figure D).  
11. Set thermostat to desired setting (See Figure).  
7. Turn gas control knob counterclockwise  
"PILOT". (Figure B).  
8. Push gas control knob down all the way and hold it  
to  
CAUTION: Hotter water increases the risk  
of scald injury. Consult the instruction  
manual before changing temperature.  
TO TURN OFF GAS TO APPLIANCE  
1. Set the thermostat to lowest setting.  
2. Push the gas control knob down slightly and turn  
clockwise to "OFF". (Figure A). Do not force.  
11  
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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 dial 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  
adjusting dial was factory set at the lowest temperature; all the way  
clockwise to the mechanical stop. Turning the dial counterclockwise  
TEMPERATURE REGULATION  
increases temperature and clockwise  
reduces temperature.  
SETTING THE WATER HEATER TEMPERATUREAT 120°F (49°C)  
(APPROX. " " MARK ON FACE OFTHERMOSTAT) WILL REDUCE  
THE RISK OF SCALDS. Some states require settings at specific  
lower temperatures.  
DANGER  
Figure 7 shows the approximate water temperatures produced at  
various 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 20°F (11°C). If you  
experience this type of use you should consider using lower  
temperature settings to reduce scald hazards.  
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 SERIOUSAND 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. NEVERALLOW  
SMALL CHILDREN TO USE A HOT WATER TAP, OR TO DRAW  
THEIR OWN BATH WATER. NEVER LEAVEACHILD OR DISABLED  
PERSON UNATTENDED IN A BATHTUB OR SHOWER.  
Valves for reducing point of use temperature by mixing cold and hot  
water are available. Also available are inexpensive devices that  
attach to faucets to limit hot water temperatures. Contact a licensed  
plumber or the local plumbing authority.  
CHECK VENTING  
THE WATER HEATER SHOULD BE LOCATED IN AN AREA  
WHERE THE GENERAL PUBLIC DOES NOT HAVE ACCESS. IF  
A SUITABLE AREA IS NOT AVAILABLE, A COVER SHOULD BE  
INSTALLED OVER THE THERMOSTAT TO PREVENT  
TAMPERING. Suitable covers are available through A.O. Smith  
Water Products Company.  
The following steps shall be followed with each appliance  
connected to the venting system placed in operation, while any  
other appliances connected to the venting system are not in  
operation.  
1. Seal any unused openings in the venting system.  
2. Inspect the venting system for proper size and horizontal pitch,  
as required in the National Fuel Gas Code, ANSI Z223.1 or the  
Natural Gas and Propane Installation Code CAN/CSA-B149.1  
and these instructions. Determine that there is no blockage or  
restriction, leakage, corrosion and other deficiencies which could  
cause an unsafe condition.  
3. So far as is practical, close all building doors and windows and  
all doors between the space in which the water heater(s)  
connected to the venting system are located and other spaces  
of the building. Turn on all appliances not connected to the  
venting system. Turn on all exhaust fans, such as range hoods  
and bathroom exhausts, so they shall operate at maximum  
speed. Close fireplace dampers.  
4. Follow the lighting instruction. Place the water heater being  
inspected in operation. Adjust thermostat so appliance shall  
operate continuously.  
Time to Produce 2nd & 3rd  
Degree Burns on Adult Skin  
Temperature Setting  
VERY HOT = APPROX.180°F (82°C)  
D = APPROX.160°F (71°C)  
C = APPROX.150°F (65°C)  
B = APPROX.140°F (60°C)  
A = APPROX.130°F (54°C)  
= APPROX.120°F (49°C)  
Nearly instantaneous  
About 1/2 second  
About 1-1/2 seconds  
Less than 5 seconds  
About 30 seconds  
More than 5 minutes  
- - - - - - - -  
5. Test for draft hood spillage at the relief opening after 5 minutes  
of main burner operation.  
6. After it has been determined that each appliance connected  
to the venting system properly vents when tested as outlined  
above, return doors, windows, exhaust fans, fireplace dampers  
and any other gas burning appliance to their previous  
conditions of use.  
LOW = APPROX.100°F (37.8°C)  
7. If improper venting is observed during any of the above tests,  
the venting system must be corrected.  
FIGURE 7  
12  
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WARNING  
ignite rapidly; give reasonably quiet operation; cause no  
excessive flame lifting from the burner ports. Make sure that the  
flow of combustion and ventilation air is not blocked.  
FAILURE TO CORRECT BACK DRAFTS MAY CAUSE AIR  
CONTAMINATION AND UNSAFE CONDITIONS.  
If the back draft cannot be corrected by the normal method or if  
a suitable draft cannot be obtained, a blower type flue gas  
exhauster must be employed to assure proper venting and  
correct combustion.  
HIGH TEMPERATURE LIMIT SWITCH  
(Auto Reset Type Energy Cut Off)  
TO RESET AUTOMATIC GAS SHUTOFF  
PROPANE  
This water heater is equipped with a automatic reset type high limit  
(Energy Cutoff) sensor. The high limit switch interrupts the pilot and  
main burner gas flow should the water temperature reach  
205°F(96°C). The high limit will automatically reset when the  
water temperature drops below 140°F (60°C).  
WARNING  
THE GAS VALVE MUST HAVE BEEN IN THE OFF POSITION FOR  
AT LEAST 5 MINUTES. This waiting period is an important safety  
step. Its purpose is to permit gas that may have accumulated  
in the combustion chamber to clear. IF YOU DETECT GAS  
ODOR AT THE END OF THIS PERIOD DO NOT PROCEED WITH  
LIGHTING. RECOGNIZE THAT GAS ODOR, EVEN IF IT SEEMS  
WEAK, MAY INDICATE PRESENCE OF ACCUMULATED GAS  
SOMEPLACE IN THEAREAWITH RISK OF FIRE OR EXPLOSION.  
SEE THE FRONT PAGE FOR STEPS TO BE TAKEN.  
NATURAL  
FIGURE 8  
Before lighting the pilot and operating the heater, the following  
conditions must exist:  
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.  
Entire system filled with water.  
Air purged from all lines and no leaks (gas and water).  
All gas and water lines open.  
WARNING  
SOOT BUILD-UP INDICATES A PROBLEM THAT REQUIRES  
CORRECTION BEFORE FURTHER USE. CONSULT WITH A  
QUALIFIED SERVICE TECHNICIAN.  
SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAIL  
TO SHUT OFF, TURN OFF THE MANUAL GAS CONTROL VALVE  
TO THE APPLIANCE.  
Should the main burner or burner air openings require cleaning,  
turn off the gas to the water heater. Follow "to turn off gas to  
appliance" on pages 10 and 11 and allow the burner to cool. Remove  
the burner and clean with a soft brush. Clean main burner orifice  
with a suitable soft material. Follow lighting instructions on pages  
10 and 11 to put the water heater back in operation.  
SERVICE INFORMATION  
The installer may be able to observe and correct certain problems  
which may arise when the unit is put into operation. HOWEVER, it  
is recommended that only qualified servicemen, using appropriate  
test equipment, be allowed to service the heater.  
CHECK FOR GOOD FLOW OF COMBUSTIONAND VENTILATING  
AIR TO THE UNIT. MAINTAIN A CLEAR OPEN AREA AROUND  
THE HEATER AT ALL TIMES. DO NOT STORE COMBUSTIBLES  
OR FLAMMABLE LIQUIDS NEAR ORAROUND AN APPLIANCE.  
FOR YOUR SAFETY AND SATISFACTORY OPERATION, IT IS  
RECOMMENDED THAT THIS HEATER BE CHECKED ONCE A  
YEAR BY A COMPETENT SERVICE PERSON.  
CHECKING GAS INPUT  
USERS OF THIS APPLIANCE SHOULD BE AWARE THAT GAS  
COMPONENTS WEAR OUT OVER A PERIOD OF TIME. THE  
GAS CARRYING COMPONENTS OF THISAPPLIANCE SHOULD  
BE INSPECTED FOR PROPER OPERATION PERIODICALLY BY  
A QUALIFIED SERVICE TECHNICIAN.  
For appliance installation locations with elevation above 2000  
ft.(610m) refer to HIGH ALTITUDE INSTALLATIONS section of this  
manual for input reduction procedure.  
With this heater in operation, determine whether it is receiving the  
full rated input of gas. This may be done by timing the gas meter  
and measuring gas pressure with a gauge or manometer. When  
the heater is operating at full capacity (full gas input) it should  
consume approximately 1 cubic foot of gas in the time shown in  
table 3.  
PILOT AND MAIN BURNER  
Check pilot and main burner (figure 8) every 12 months for proper  
flame characteristics. This is done by removing door(s) on heater.  
The main burner should provide complete combustion of gas;  
13  
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TABLE 3  
WARNING  
SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAIL  
INPUT CHECK TIME REQUIRED TO  
CONSUME 1 CU. FT. OF GAS  
TO SHUT OFF, TURN OFF THE MANUAL GAS CONTROL VALVE  
TO THE APPLIANCE.  
Type of  
Gas  
BTU Per Approx. Time Required To  
Model  
Cu. Ft.  
1050  
2500  
1050  
2500  
Consume 1 Cu. Ft. of Gas  
50.3 sec.  
HOT WATER ODOR  
BT-80  
Natural  
Propane  
Natural  
Propane  
On occasion, hot water may develop a strong odor. If this occurs drain  
the heater completely, flush thoroughly, and refill. If the problem persists,  
chlorination of the heater and replacement of the factory installed  
magnesium anodes with aluminum anodes may correct the condition.  
119.8 sec.  
BT-100  
50.3 sec.  
119.8 sec.  
Use this formula to “clock” the meter. Be sure that other gas  
consuming appliances are not operating during this interval.  
Occasionally water softener companies recommend removal of  
heater anodes for odor reasons.  
3,600 X H = Btu/Hr  
T
CAUTION  
Unauthorized removal of heater anode(s) will void the warranty.  
Replace the anode as necessary to maintain corrosion  
protection. For further information contact your dealer.  
T = Time in seconds needed to burn one cubic foot of gas.  
H = Heating value of gas in Btu’s per cubic foot of gas.  
Btu/Hr = Actual heater input rate.  
Example: (Using BT-80 heater)  
ANODE ROD INSPECTION  
The heater tank is equipped with anode rods to provide corrosion  
control. At least once a year the anode rods should be checked to  
determine if replacement is necessary. Initially the anode rods are  
approximately 7/8" (22mm) in diameter with a 1/8" (3mm) diameter  
steel core wire running down the center of the anode material. THE  
ANODES SHOULD BE REPLACED when the 1/8" (3mm) diameter  
core wire is visible as this means that the anode material has been  
expended in the control of corrosion.  
T = 50.3 seconds/ft3  
H = 1,050 Btu/ft3 (natural gas)  
Btu/Hr = ?  
3,600 X 1,050 = 75,100 Btu/Hr (22.0 kW)  
50.3  
NOTE: Anode rod inspection may need to be made more  
frequently in areas subject to acid rain that obtains their water  
supply from surface water as the low pH will accelerate anode  
activity.  
Compare the actual input rate to that given on the heater’s rating  
plate. In the example, the BT-80’s full input rate should be 75,100  
Btu/Hr for natural gas.  
VENT SYSTEM  
CAUTION: Close cold water inlet valve serving heater and open  
nearby hot water faucet to relieve the pressure in the heater  
before attempting to remove anode(s) for inspection.  
Examine the venting system every 6 months for obstructions and/  
or deterioration of vent piping.  
WINTER PROTECTION  
RELIEF VALVE  
In regions where freezing weather is encountered, all water must  
be drained from unit and piping when out of service (water shut off).  
Drain valve must be left open until unit is returned to service.  
At least once a year the temperature and pressure relief valve should  
be checked to ensure that it is in operating condition. (During manual  
operation of this valve, avoid any contact with hot water and take  
preventive steps for water damage). Lift the lever at the top of the  
valve several times until the valve seats properly and operates freely.  
REPLACEMENT PARTS  
Replacement parts may be ordered through A. O. Smith dealers,  
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). For  
Canada call or contact A.O. Smith Water Products Company, 768  
Erie Street Stratford, ON N5A 6T3 (519-271-5800 x 401, or visit our  
sure to state the quantity, part number and description of the item  
including the complete model and serial number as it appears on  
the product. Refer to the parts list for more information.  
WARNING  
THE WATER PASSING OUT OF THE VALVE DURING THIS  
CHECKING OPERATION MAY BE EXTREMELY HOT. AVOID  
CONTACT AND DISCHARGE SAFELY TO PREVENT WATER  
DAMAGE.  
If the temperature and pressure relief valve on the heater discharges  
periodically or continuously, a problem exists. This may be due to  
unusually high water temperatures or pressures in the system, or to  
a faulty relief valve. Contact your dealer or a qualified service  
technician to find the cause of the problem and to correct it. This  
may also be due to thermal expansion in a closed water supply  
system. Contact the water supplier or local plumbing inspector  
on how to correct this situation. DO NOT PLUG THE  
TEMPERATURE AND PRESSURE RELIEF VALVE.  
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TANK CLEANOUT PROCEDURE  
PREVENTIVE MAINTENANCE  
The following practices will ensure longer life and enable the unit to  
operate at its designed efficiency:  
RECOMMENDED PROCEDURE FOR PERIODIC  
REMOVAL OF LIME DEPOSITS FROM TANK TYPE  
COMMERCIAL WATER HEATERS  
1. Once a month the heater should be flushed. Open the drain  
valve and allow two gallons of water to drain from the heater.  
Inlet water valve should remain open to maintain pressure in  
tank.  
The amount of calcium carbonate (lime) released from water is in  
direct proportion to water temperature and usage, see chart. The  
higher the water temperature or water usage, the more lime deposits  
are dropped out of the water. This is the lime scale which forms in  
pipes, heaters and on cooking utensils.  
2. A cleanout opening is provided for periodic cleaning of the tank.  
Gas must be shut off and heater drained before opening  
cleanout.  
Lime accumulation not only reduces the life of the equipment but  
also reduces efficiency of the heater and increases fuel  
consumption.  
To clean heater through cleanout opening, proceed as follows:  
1. Drain heater.  
The usage of water softening equipment greatly reduces the  
hardness of the water. However, this equipment does not always  
remove all of the hardness (lime). For this reason it is recommended  
that a regular schedule for deliming be maintained.  
2. Remove outer cover plate from lower side of heater jacket.  
3. Remove six (6) hex head screws securing tank cleanout plate  
and remove plate.  
4. Remove lime, scale, or sediment using care not to damage the  
glass lining.  
5. Inspect cleanout plate gasket, if new gasket is required, see  
replacement parts list for item number.  
6. Install cleanout plate. Be sure to draw plate up tight by tightening  
screws securely.  
7. Replace outer jacket cover plate.  
The time between cleaning will vary from weeks to months  
depending upon water conditions and usage.  
Refer to A. O. Smith booklet, Form No. 4800, entitled “Why? When  
and How” for detailed description on tank inspection and cleanout.  
UN•LIME® and the booklet may be obtained through your  
A. O. Smith dealer or distributor.  
DELIMING SOLVENTS  
A. O. Smith recommends the use of UN•LIME for deliming. UN•LIME  
is a patented food grade acid which is safe to handle and does not  
create the harmful fumes which are associated with other products.  
UN•LIME may be obtained from your dealer, distributor or the  
A. O. Smith Product Service Division. Order part no. 4763 (1 gal),  
packed 4 gallons per case or part no. 4813 (5 gallon container).  
FIGURE 9  
Hydrochloric base acids are not recommended for use on glass-  
lined tanks.  
In some water areas the sediment might not be removed by this  
method and may result in the water heater making rumbling or  
boiling noises. To dissolve and remove these more stubborn  
mineral deposits, A. O. Smith UN•LIME Professional Delimer should  
be used.  
CAUTION  
Observe handling instructions on label of product being used.  
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Note: To check UN•LIME for continued use, place some scale or  
white chalk in a glass with a small amount of UN•LIME. If the material  
is vigorously dissolved by the UN•LIME, it can be reused; if not, the  
UN•LIME should be replaced.  
DELIMING USING FLO-JUG METHOD  
UN•LIME in the 5 gallon size is recommended for deliming of the  
BT-80 and 100 models. UN•LIME with the necessary hoses and  
fittings to delime your heater is also available as a kit: Up-N-Down  
Transfer Kit. Contact your local A.O. Smith dealer, distributor or,  
A.O. Smith Water Products Company, Telephone: (800) 433-2545,  
CHECKLIST  
Before contacting your dealer, check the water heater to see if the  
apparent malfunction is caused by some external fault. Consulting  
this checklist may eliminate the need for a repair call and restore  
hot water service.  
Prepare the Water Heater  
To delime the water heater using the Flo-Jug method, first prepare  
the heater for deliming as described in the "Why? When? and How?"  
booklet, Form No. 4800. Then install the long plastic male adapter  
fitting into the drain valve opening of the water heater. Use teflon  
tape and hand tighten only. Do not overtighten.  
NOT ENOUGH OR NO HOT WATER  
1. Check to see if the pilot flame is lit.  
To relight the pilot, follow the instructions on the heater or in  
this manual.  
Prepare the Up-N-Down Transfer Kit  
The next step is the preparation on the Up-N-Down Transfer Kit, if  
you have not already done so:  
Check to see if the main gas shutoff valve in the gas supply  
pipe is partially closed or the water temperature dial is set  
too low.  
1. With the 5 gallon Up-N-Down container in the vertical position,  
unscrew the plastic vent cap in the handle and pierce the plastic  
membrane over the vent boss under the cap to allow the  
container to vent.  
2. Look for leaking or open hot water faucets. Check for excessive  
usage.  
3. Your gas company can check the gas input to the heater to see  
that it is correct. An underfired heater will not produce hot water  
at its normal recovery rate.  
Note: If your container does not have the vent cap and vent  
boss, drill a 3/16" (4.76mm) hole in the handle. When you have  
finished deliming you will be able to plug this drilled vent with  
the stainless steel screw that is supplied with the kit.  
4. If the heater was installed when incoming water temperatures  
were warm, colder incoming temperatures will create the effect  
of less hot water.  
2. Remove the container's cap and cut the plastic membrane  
located in the 3/4" IPT opening in the cap. Take care to not  
damage the threads.  
5. The thermostat water temperature adjusting dial may be set too  
low.  
3. Find the 3/4" male adapter, apply teflon tape to the threaded  
end and screw it into the 3/4" IPT opening in the cap.  
6. If you cannot determine the cause of the problems, contact your  
dealer.  
4. Put cap with male adapter back on the container and slide 3/4"  
hose over end of male adapter and fasten in place using hose  
clamp provided.  
WATER TEMPERATURE IS TOO HOT  
1. The thermostat water temperature adjusting dial may be set too  
high.  
Delime using Flo-Jug Method  
2. If lowering control setting does not reduce the water temperature  
contact your dealer.  
5. Slide the hose clamp over end of hose and slide hose over the  
male adapter in the water heater drain opening and secure in  
place using hose clamp.  
GAS SMELL AT THE HEATER  
6. Lift container to the "Pour" Position, see Figure 9, being careful  
to keep the vent in the handle above the liquid level and pour  
the UN•LIME into the heater.  
1. Close the main shutoff valve in the gas supply pipe near the  
heater, see fig. 4 on page 7. The thermostat includes a gas  
control (top knob) which can also be closed.  
7. Lower container, you may have to place the container on its  
empty carton to prevent the UN•LIME from flowing back into the  
container.  
2. Call your gas company.  
WATER LEAKAGE IS SUSPECTED  
8. Let UN•LIME remain in the heater for 5 minutes and then lower  
the container to the "Drain" Position, see Figure 9.  
1. Check to see if the heater drain valve is tightly closed.  
2. The apparent leakage might be condensation. In warm or humid  
locations, condensation can accumulate and run from within  
the heater or its piping.  
9. Deliming activity is indicated by foaming on the surface of the  
UN•LIME. If there is deliming activity, repeat steps 6 thru 8.  
When a water heater is first installed and filled, the bottom  
of the tank might condense water. The water accumulation,  
Normally, lime removal will be completed within one hour. Severe  
build-up of lime may take longer than an hour to complete descaling.  
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if excessive, can drip into the floor shield. Also, during normal  
operation there may be occasions when large quantities of  
water are drawn, chilling the tank bottom. This too can result  
in condensation.  
Close the main shutoff valve in the gas supply pipe at the  
heater. See fig. 4, page 7.  
Close the valve which feeds water to the cold water inlet at  
the top of the heater.  
Condensation, appearing in the vent pipe (water dripping  
from draft diverter) during heater operation is evidence of  
poor vent action. Possible causes are too long a vent pipe  
or improper chimney operation.  
Contact your dealer.  
WATER HEATER MAKES SOUNDS  
1. Occasional excessive condensation, as explained under WATER  
LEAKAGE IS SUSPECTED, can cause a sizzling sound as the  
moisture is vaporized by the gas flame. This is a normal sound  
and may be disregarded.  
3. If the leakage is from the temperature and pressure relief valve  
or its discharge pipe, it may represent a normal condition.  
However, see RELIEF VALVE section on page 14. DO NOT  
PLUG THE TEMPERATUREAND PRESSURE RELIEF VALVE.  
Also, the leakage could be due to unusually high water pressures  
or temperatures in the system, or to a faulty relief valve. Your  
dealer or a qualified service technician should be called to  
determine the cause of the problem and to correct it.  
2. Sediment and water scale accumulations may cause rumbling  
noises. See PREVENTIVE MAINTENANCE or contact your  
dealer for details of flushing the heater.  
3. If you cannot identify or remedy the condition, contact your  
dealer.  
4. If you cannot identify or correct the source of water leakage:  
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Model BT Limited Warranty  
A. O. Smith Corporation, the warrantor, extends the following LIMITED WARRANTY to the owner of this water heater.  
1. THE TANK  
If the glass-lined tank in this water heater shall prove upon examination by the warrantor to have leaked due to natural corrosion from potable water  
therein, during the first THREE years after initial installation, the warrantor will supply a complete new A. O. Smith water heater of equivalent size and  
current model. Some government agencies are requiring energy efficient standards for water heaters. In the event regulations prohibit sale of a  
model of equivalent size and construction, A. O. Smith will provide a model which complies with the regulations of your area, in which case the  
consumer will be charged the difference in price between the like replacement and the energy efficient model required. The warranty on the  
replacement water heater will be limited to the unexpired term of the original warranty.  
2. ALL OTHER PARTS  
If within ONE year after initial installation of this water heater, any part or portion shall prove upon examination by the warrantor to be defective in  
material or workmanship, the warrantor will repair or replace such part or portion at its option.  
3. CONDITIONS AND EXCEPTIONS  
This warranty shall apply only when the water heater is installed in accordance with local plumbing and building codes, ordinances and regulations,  
the printed instructions provided with it and good industry practices. In addition, a temperature and pressure relief valve, certified by and officially  
sanctioned and recognized independent testing agency and approved by the American Society of Mechanical Engineers, must have been installed.  
a.  
This warranty shall apply only when the heater is:  
(1) used at temperatures not exceeding the maximum calibrated setting of its thermostat;  
(2) used at water pressure not exceeding the working pressure shown on the heater;  
(3) filled with potable water, free to circulate at all times and with the tank free of damaging water sediment or scale deposits;  
(4) used in a non-corrosive and non-contaminated atmosphere;  
(5) used with factory approved anode(s) installed;  
(6) in its original installation location;  
(7) in the United States, its territories or possessions;  
(8) sized in accordance with proper sizing techniques for commercial and/or residential water heaters;  
(9) bearing a rating plate which has not been altered, defaced or removed, except as required by the warrantor;  
(10) used in an open system or in a closed system with properly sized and installed thermal expansion tank;  
(11) operated with properly installed dirt leg;  
(12) fired with the fuel for which it was factory built;  
(13) fired at the factory rated input;  
(14) operated with the inner and outer combustion chamber doors in place.  
b. Any accident to the water heater, any misuse, abuse (including freezing or thermal expansion damage) or alteration of, any operation in a  
modified form, or any attempt to repair tank leaks will void this warranty.  
c. This warranty is void if a device acting as a backflow prevention device (check valves etc.) is installed in the cold water supply the heater is  
connected to, unless an effective method of controlling thermal expansion is also installed at the heater(s) and operational at all times. The relief  
valve installed on the heater is not an acceptable method.  
4. SERVICE AND REPAIR EXPENSES  
Under the limited warranty the warrantor will provide only a replacement water heater or part thereof. The owner is responsible for all other costs.  
Such costs may include but are not limited to:  
a. Labor charges for service removal, repair or reinstallation of the water heater or any component part;  
b. Shipping, delivery, handling, and administrative charges for forwarding the new heater or replacement part from the nearest distributor and  
returning the claimed defective heater or part to such distributor.  
c. All cost necessary or incidental for any material and/or permits required for installation of the replacement heater or part.  
5. LIMITATIONS ON IMPLIED WARRANTIES  
Implied warranties, including the warranty of merchantability imposed on the sale of this heater under state law are limited to one (1) year duration  
for the heater or any of its parts. Some states do not allow limitation on how long an implied warranty lasts, so the above limitation may not apply  
to you.  
6. CLAIM PROCEDURE  
Any claim under the 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 practicable, the owner should contact:  
U.S. Customers  
Canadian Customers  
A. O. Smith Enterprises Ltd.  
768 Erie Street  
Stratford (Ontario) N5A 6T3  
Telephone:(800) 265-8520  
A. O. Smith Water Products Company  
500 Tennessee Waltz Parkway  
Ashland City, TN 37015  
Telephone: (800) 527-1953  
a.  
The warrantor will only honor replacement with identical or similar water heater or parts thereof which are manufactured or distributed by the  
warrantor.  
b. Dealer replacements are made subject to in-warranty validation by warrantor.  
7. DISCLAIMERS  
NO OTHER EXPRESS WARRANTY HAS BEEN OR WILL BE MADE IN BEHALF OF THE WARRANTOR WITH RESPECT TO THE MERCHANTABIL-  
ITY OF THE HEATER OR THE INSTALLATION, OPERATION, REPAIR OR REPLACEMENT OF THE HEATER. THE WARRANTOR SHALL NOT BE  
RESPONSIBLE FOR WATER DAMAGE, LOSS OF USE OF THE UNIT, INCONVENIENCE, LOSS OR DAMAGE TO PERSONAL PROPERTY OR  
OTHER CONSEQUENTIAL DAMAGE. THE WARRANTOR SHALL NOT BE LIABLE BY VIRTUE OF THIS WARRANTY OR OTHERWISE FOR  
DAMAGE TO ANY PERSONS OR PROPERTY, WHETHER DIRECT OR INDIRECT, AND WHETHER ARISING IN CONTRACT OR IN TORT.  
a. Some states do not allow the exclusion or limitation of the incidental or consequential damage, so the above limitations or exclusions may not  
apply to you.  
b. This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.  
Fill in the following for your own reference. Keep it. Registration is not a condition of warranty. The model and serial number are found on the heater’s  
rating plate.  
Model No. ____________________Serial No. _____________________________________________Date Installed___________________________  
Dealer’sName____________________________________________________________________________________________________________  
Dealer’s Address ________________________________________________________________________ Phone No.________________________  
City and State __________________________________________________________________________ Zip ______________________________  
KEEP THIS WARRANTY POSTED ADJACENT TO THE HEATER FOR FUTURE REFERENCE.  
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A.O. SMITH WATER PRODUCTS COMPANY  
500 Tennessee Waltz Parkway • Ashland City, TN 37015  
PHONE: 1-800-527-1953  
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