AO Smith Water Heater 300A User Guide

CYCLONE Xi® Model BTH 300A, 400A, 500A  
COMMERCIAL GAS WATER HEATER  
GAS-FIRED POWER BURNER  
FOR DOMESTIC HOT WATER  
• INSTALLATION • OPERATION • SERVICE • MAINTENANCE • LIMITED WARRANTY  
WARNING: If the information in these  
instructions is not followed exactly, a fire  
or explosion may result causing property  
damage, personal injury or death.  
– Do not store or use gasoline or other  
flammable vapors and liquids in the  
vicinity of this or any other appliance.  
– WHAT TO DO IF YOU SMELL GAS:  
• Do not try to light any appliance.  
• Do not touch any electrical switch;  
do not use any phone in your  
building.  
• Immediately call your gas supplier  
from a neighbor's phone. Follow the  
gas supplier's instructions.  
• If you cannot reach your gas supplier,  
call the fire department.  
– Installation and service must be  
performed by a qualified installer,  
service agency or the gas supplier.  
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 PRINTED OR OUTLINED IN RED CONTAINS  
INFORMATION RELATIVE TO YOUR SAFETY. PLEASE  
READ THOROUGHLY BEFORE INSTALLINGAND USING  
THIS APPLIANCE.  
PLACE THESE INSTRUCTIONS ADJACENT TO HEATER AND NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.  
PRINTED 0307  
ꢀ97373-003  
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ROUGH-IN-DIMENSIONS  
GAS VALVE PIPING  
BTH-300 1 1/4" NPT  
BTH-400 1 1/4" NPT  
BTH-500 1 1/2" NPT  
TABLE 1 RECOVERY CAPACITIES.  
U.S. Gallons/Hr and Litres/Hr at TEMPERATURE RISE INDICATED  
TYPE OF  
GAS  
INPUT  
BTUH  
Approx.  
F°  
20F°  
11C°  
1746  
6610  
1746  
6610  
2328  
8813  
2328  
8813  
2878  
30F° 40F° 50F° 60F° 70F° 80F° 90F° 100F° 110° 120F° 130F° 140F°  
MODEL  
KW  
88  
Capacity  
C°  
17C° 22C° 28C° 33C° 39C° 44C° 50C° 56C° 61C° 67C° 72C°  
1164 873 699 582 499 436 388 349 318 291 269  
4406 3304 2644 2203 1888 1652 1469 1322 1201 1102 1017  
1164 873 699 582 499 436 388 349 318 291 269  
4406 3304 2644 2203 1888 1652 1469 1322 1201 1102 1017  
1552 1164 931 776 665 582 517 466 423 388 359  
78C°  
250  
945  
250  
945  
332  
300,000  
300,000  
399,900  
399,900  
499,900  
499,900  
130 US Gals. GPH  
492 Litres LPH  
130 US Gals. GPH  
492 Litres LPH  
130 US Gals. GPH  
492 Litres LPH  
130 US Gals. GPH  
492 Litres LPH  
130 US Gals. GPH  
492 Litres  
130 US Gals. GPH  
492 Litres LPH 10894 7263 5447 4358 3631 3113 2724 2421 2179 1981 1816 1676 1556  
BTH-300 NATURAL  
BTH-300 PROPANE  
88  
NATURAL  
BTH-400  
117  
117  
146  
146  
5875 4406 3525 2938 2518 2203 1958 1763 1602 1469 1356 1259  
1552 1164 931 776 665 582 517 466 423 388 359 332  
5875 4406 3525 2938 2518 2203 1958 1763 1602 1469 1356 1259  
1919 1439 1151 959 822 720 640 576 523 480 443 411  
BTH-400 PROPANE  
BTH-500 NATURAL  
LPH 10894 7263 5447 4358 3631 3113 2724 2421 2179 1981 1816 1676 1556  
2878 1919 1439 1151 959 822 720 640 576 523 480 443 411  
BTH-500 PROPANE  
Recovery capacities are based on heater performance at 96% thermal efficiency for BTH 300A, 400A, and 95% thermal efficiency for BTH 500A.  
FOREWORD  
These designs comply with the current edition of the American  
National Standard for Gas Water Heaters, Volume III,  
ANSI Z21.10.3 / CSA 4.3 as an automatic circulating tank water  
heater, and automatic storage water heaters.  
In addition to these instructions, the equipment shall be installed in  
accordance with those installation regulations in force in the local  
area where the installation is to be made. These shall be carefully  
followed in all cases. Authorities having jurisdiction should be  
consulted before installations are made.  
Detailed installation diagrams are found in this manual. These  
diagrams will serve to provide the installer with a reference for the  
materials and methods of piping necessary. It is highly essential  
that all water, gas piping and wiring be installed as shown on the  
diagrams.  
In the absence of local codes, the installation must comply  
with the current editions of the National Fuel Gas Code,  
ANSI Z223.1/NFPA 54 and the National Electrical Code,  
NFPA 70 or CAN/CSA-B149.1, the Natural Gas and Propane  
Installation Code and CSA C22.1, the Canadian Electrical Code. All  
documents are available from the Canadian StandardsAssociation,  
8501 East Pleasant Valley Road, Cleveland, OH 44131. NFPA  
documents are also available from the National Fire Protection  
Association, 1 Batterymarch Park, Quincy, MA 02269.  
Particular attention should be given to the installation of thermometers  
at the locations indicated on the diagrams as these are necessary  
for checking the proper functioning of the heater.  
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TABLE OF CONTENTS  
Water (Potable) Heating & Space Heating..........................................7  
ROUGH-IN DIMENSIONS.........................................................................ꢁ  
FOREWORD .............................................................................................ꢁ  
FEATURES................................................................................................3  
Water Temperature Control................................................................3-5  
Water Temperature Setpoint Adjustment Procedure.............................5  
High Limit Switch (E.C.O.) ....................................................................5  
Dishwashing Machine Requirement......................................................5  
Circulating Pump...................................................................................6  
INSTALLATION INSTRUCTIONS .............................................................6  
Required Ability .....................................................................................6  
Insulation Blankets................................................................................6  
Locating The Heater..............................................................................6  
Clearances............................................................................................7  
Hard Water............................................................................................7  
Air Requirements ..................................................................................7  
Mechanical Exhausting of Room Air .....................................................7  
Unconfined Space.................................................................................7  
Confined Space.....................................................................................7  
Chemical Vapor Corrosion ....................................................................7  
Installation Requirements for the  
Commonwealth of Massachusetts ........................................................8  
VENTING..............................................................................................8-ꢀꢀ  
Vent Pipe Termination ......................................................................... ꢀꢀ  
Direct Venting...................................................................................... ꢀꢀ  
Direct Vent Terminal Installation.....................................................ꢀ-ꢀꢁ  
Installation Sequence..........................................................................ꢁ  
Vertical Vent Terminal Installation .......................................................ꢁ  
Installation Sequence.....................................................................ꢀꢁ-ꢀ3  
Installation of Vent System..................................................................3  
Vent Pipe Preparation .........................................................................14  
CONTROLS AND SWITCHES ................................................................14  
Blower Prover Switch..........................................................................14  
Blocked Outlet Prover Switch..............................................................14  
Blocked Inlet Prover Switch ................................................................14  
Low Gas Pressure Switch...................................................................14  
On/Off Switch.................................................................................14-15  
Hot Surface Igniter ..............................................................................5  
GAS PIPING............................................................................................5  
Connection of Gas Pipe .................................................................15-16  
Purging................................................................................................16  
Gas Meter Size - City Gases Only ......................................................16  
Gas Valves..........................................................................................16  
SYSTEM CONNECTIONS ......................................................................16  
Thermometers.....................................................................................16  
Relief Valve .........................................................................................16  
Water Line Connections......................................................................16  
Closed System...............................................................................16-17  
Heater Wiring .................................................................................ꢀ7-ꢀ9  
OPERATION............................................................................................0  
Sequence of Operation .......................................................................0  
ELECTRONIC CONTROL.......................................................................0  
Overview .............................................................................................0  
Operating States ............................................................................ꢁ0-ꢁꢀ  
Adjusting the Operating Set Point.......................................................ꢀ  
Changing the Display Units.................................................................ꢁ  
Fault and Warning Conditions........................................................ꢁꢁ-ꢁ3  
Access to the Current Fault or Warning..............................................3  
Viewing the Fault History ....................................................................24  
Viewing Information About the Heater.................................................24  
PRIOR TO START-UP REQUIRED ABILITY...........................................5  
OPERATING INSTRUCTIONS................................................................5  
Adjustment Procedure (Initial Start-Up) .........................................25-26  
Lighting Instructions ............................................................................26  
Cathodic Protection.............................................................................7  
Precautions .........................................................................................7  
GENERAL INFORMATION......................................................................7  
Power Burner ......................................................................................7  
High Limit ............................................................................................7  
High Altitude Installations....................................................................7  
MAINTENANCE ......................................................................................7  
General ...............................................................................................7  
Maintenance Schedule........................................................................7  
Flushing...............................................................................................8  
Draining...............................................................................................8  
Sediment Removal..............................................................................8  
Lime Scale Removal ......................................................................ꢁ8-ꢁ9  
Powered Anode System......................................................................9  
Drain Valve and Access Panels ..........................................................9  
Relief Valve .........................................................................................9  
Vent System........................................................................................9  
INSTALLATION DIAGRAMS ..............................................................30-34  
Multiple Unit Installations ....................................................................35  
CHECKLIST AND SERVICE INFORMATION .........................................36  
Burner Operational Problems..............................................................36  
Not Enough or No Hot Water ..............................................................36  
Water Is Too Hot..................................................................................36  
Water Heater Makes Sounds..............................................................36  
Water Leakage is Suspected...................................................................36  
TROUBLESHOOTING .......................................................................36-38  
REPLACEMENT PARTS.........................................................................38  
LIMITED WARRANTY.............................................................................39  
FEATURES  
DANGER  
THIS WATER HEATER IS EQUIPPED WITH AN ADJUSTABLE  
THERMOSTAT TO CONTROL WATER TEMPERATURE. HOT  
WATER TEMPERATURES REQUIRED FOR AUTOMATIC  
DISHWASHER AND LAUNDRY USE CAN CAUSE SCALD  
BURNS RESULTING IN SERIOUS PERSONAL INJURY AND/OR  
DEATH. THE TEMPERATURE AT WHICH INJURY OCCURS  
VARIES WITH THE PERSON’S AGE AND TIME OF EXPOSURE.  
THE SLOWER RESPONSE TIME OF CHILDREN, AGED OR  
DISABLED PERSONS INCREASES THE HAZARDS TO THEM.  
NEVER ALLOW SMALL CHILDREN TO USE A HOT WATER TAP,  
OR TO DRAW THEIR OWN BATH WATER. NEVER LEAVE A  
CHILD OR DISABLED PERSON UNATTENDED IN A BATHTUB  
OR SHOWER.  
IMPORTANT  
IT IS REQUIRED THAT A QUALIFIED SERVICE TECHNICIAN  
PERFORM THE INITIAL FIRING OF THE HEATER. AT THIS TIME  
THE USER SHOULD NOT HESITATE TO ASK THE TECHNICIAN  
ANY QUESTIONS WHICH HE MAY HAVE IN REGARD TO THE  
OPERATION AND MAINTENANCE OF THE UNIT.  
ACHECKLISTAND SERVICE INFORMATION section are included  
at the rear 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.  
WATER TEMPERATURE CONTROL  
THE WATER HEATER SHOULD BE LOCATED IN AN AREA  
WHERE THE GENERAL PUBLIC DOES NOT HAVE ACCESS TO  
SET TEMPERATURES.  
The water temperature is controlled using the Temperature Control  
Up/Dn Button on the Display at the front of the unit (See Figure 1).  
This control utilizes two temperature probes to determine the tank  
temperature. The primary temperature probe is located at the top  
of the tank and the other is near the water inlet.  
3
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“AT A GLANCE” BTH 300/400/500  
QUICK INSTALLATION TIPS  
Horizontal Sidewall Venting  
Vertical Rooftop Venting  
4
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The temperature may be adjusted from 80°F/27°C to 180°F/82°C. Valves for reducing point-of-use temperature by mixing cold  
The temperature was adjusted to 120°F/49°C before the heater and hot water are available (see Figure 2). Also available are  
was shipped from the factory. It is recommended that lower water inexpensive devices that attach to faucets to limit hot water  
temperatures be used to avoid the risk of scalding. It is further temperatures. Contact a licensed plumber or the local plumbing  
recommended, in all cases, that the water temperature be set for the authority.  
lowest temperature which satisfies your hot water needs. This will  
also provide the most energy efficient operation of the water heater  
and minimize scale formation.  
WATER TEMPERATURE SETPOINT ADJUSTMENT  
PROCEDURE  
CAUTION  
THE TEMPERATURE OF THE WATER AT THE TANK OUTLET  
MAY NOT CORRESPOND TO THE TEMPERATURE SETPOINT  
PROGRAMMED IN THE CONTROLLER. THE USER CAN EASILY  
CHANGETHETEMPERATURESETPOINTATANYTIMEBYUSING  
THE FOLLOWING PROCEDURE. INALL CASES, INPUT POWER  
MUST BE APPLIED TO THE CONTROLLER TO PERFORM ANY  
PROGRAMMING OPERATIONS.  
TheOperating Set Point of this water heater determines the regulated  
temperature for the water in the tank. This parameter is adjusted in the  
Temperature menu. Items in this menu allow you to monitor different  
temperature readings in the tank along with adjusting the Operating  
Set Point and Differential. To change the current programmed  
temperature setpoint value, see OPERATION section for details.  
FIGURE 2.  
Figure 1 shows the approximate time-to-burn relationship for normal  
adult skin. Short repeated heating cycles caused by small hot water  
uses can cause temperatures at the point of use to exceed the  
HIGH LIMIT SWITCH (E.C.O.)  
thermostat setting by up to 20°F (11C°). If you experience this type  
of use, you should consider using lower temperature settings to  
reduce scald hazards.  
The top immersion well of the dual bulb controller also contains the  
high limit (energy cutoff) sensor. The high limit switch interrupts  
the main burner gas flow should the water temperature reach  
approximately 202°F/94°C. Should the high limit switch activate,  
the water temperature must drop below 140°F/60°C before the  
controller can be reset. The following is a possible reason for high  
limit switch operation.  
A malfunction in the thermostatic controls would allow the gas  
valve to remain open causing water temperature to exceed the  
thermostat setting. The water temperature would continue to rise  
until high limit switch operation.  
Contact your dealer or servicer if continued high limit switch  
operation occurs.  
DISHWASHING MACHINE REQUIREMENT  
All dishwashing machines meeting the National Sanitation  
Foundation requirements are designed to operate with water flow  
pressures between 15 and 25 pounds per square inch (103 Kpa  
and 173 Kpa). Flow pressures above 25 pounds per square inch  
(173 Kpa), or below 15 pounds per square inch (103 Kpa), will result  
in improperly sanitized dishes. Where pressures are high, a water  
pressure reducing or flow regulating control valve should be used  
in the 180°F (82°C) line to the dishwashing machine, and should be  
adjusted to deliver water between these limits.  
Temperature  
Setting  
Time to Produce 2nd & 3rd  
Degree Burns on Adult Skin  
Nearly instantaneous  
Nearly instantaneous  
About 1/2 second  
180°F/82°C  
170°F/77°C  
160°F/71°C  
150°F/66°C  
140°F/60°C  
130°F/54°C  
120°F/49°C  
The National Sanitation Foundation also recommends circulation of  
180°F (82°C) water. Where this is done, the circulation should be  
very gentle so that it does not cause any unnecessary turbulence  
inside the water heater. The circulation should be just enough to  
provide 180°F (82°C) water at the point of take-off to the dishwashing  
machine. Adjust flow by means of the plug cock in the circulating  
line. (See installation diagrams.)  
About 1-1/2 seconds  
Less than 5 seconds  
About 30 seconds  
More than 5 minutes  
FIGURE 1.  
5
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THE HEATER SHALLBE LOCATED OR PROTECTED SO ITIS NOT  
SUBJECT TO PHYSICAL DAMAGE BY A MOVING VEHICLE.  
CIRCULATING PUMP  
Acirculating pump is used when a system requires a circulating loop or  
there is a storage tank used in conjunction with the heater. Refer to the  
piping diagrams at rear of manual for electrical hookup information and  
install in accordance with the current edition of the National Electrical  
Code, NFPA 70 or the Canadian Electrical Code, CSA C22.1.  
DO NOT LOCATE THE HEATER WHERE NOISE FROM THE  
EXHAUST OR INTAKE WILL BE OBJECTIONABLE. THIS  
INCLUDES LOCATIONS CLOSE TO OR ACROSS FROM  
WINDOWS AND DOORS. AVOID ANCHORING THE VENT AND  
INTAKE PIPES DIRECTLY TO FRAMED WALLS, FLOORS OF  
CEILINGS UNLESS RUBBER ISOLATION PIPE HANGERS  
ARE USED. THIS PREVENTS ANY VIBRATIONS FROM BEING  
TRANSMITTED INTO THE LIVING SPACES.  
All bronze circulators are recommended for used with commercial  
water heaters.  
Although circulators are oiled and operated by the manufacturer  
some circulators must be oiled again before operated. Please refer  
to manufacturer's instructions.  
WARNING  
FLAMMABLE ITEMS, PRESSURIZED CONTAINERS OR ANY  
OTHER POTENTIAL FIRE HAZARDOUS ARTICLES MUST  
NEVER BE PLACED ON ORADJACENT TO THE HEATER. OPEN  
CONTAINERS OF FLAMMABLE MATERIAL SHOULD NOT BE  
STORED OR USED IN THE SAME ROOM WITH THE HEATER.  
INSTALLATION INSTRUCTIONS  
REQUIRED ABILITY  
When installing the heater, consideration must be given to  
proper location. Location selected should be as close to the  
intake and exhaust termination points as practicable, with  
adequate air supply and as centralized with the piping system  
as possible.  
INSTALLATION OR SERVICE OF THIS WATER HEATER  
REQUIRES ABILITY EQUIVALENT TO THAT OF A LICENSED  
TRADESMAN IN THE FIELD INVOLVED. PLUMBING, AIR  
SUPPLY, VENTING, GAS SUPPLY AND ELECTRICAL WORK  
ARE REQUIRED.  
THE HEATER MUST NOT BE LOCATED IN AN AREA WHERE IT  
WILL BE SUBJECT TO FREEZING.  
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  
90.1-1999 standards with respect to insulation and standby loss  
requirements, making an insulation blanket unnecessary.  
LOCATE IT NEAR A FLOOR DRAIN. 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.  
When such locations cannot be avoided, it is recommended that  
a suitable drain pan, adequately drained, be installed under the  
appliance.  
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.  
WARNING  
THIS WATER HEATER ISACONDENSING UNITAND REQUIRES  
A DRAIN TO BE LOCATED IN CLOSE PROXIMITY TO ALLOW  
THE CONDENSATE TO DRAIN SAFELY. THE CONDENSATE  
DRAINS FROM THE UNIT AT THE EXHAUST ELBOW LOCATED  
AT THE BOTTOM OF THE UNIT. NOTE: IT IS IMPORTANT THAT  
THE CONDENSATE HOSE NOT BE ELEVATED ABOVE THE  
EXHAUST ELBOW (SEE FIGURE 3). THE CONDENSATE BUILD-  
UP WILL BLOCK THE EXHAUST OUTLET, WHICH WILL CAUSE  
IMPROPER OPERATION.  
Do not apply insulation to the top, or the upper 15" (38 cm) of the  
water heater, as this will interfere with safe operation.  
Do not cover the temperature & pressure relief valve.  
Do not cover the instruction manual. Keep it on the side of the  
water heater or nearby for future reference.  
Do obtain new labels fromA.O. Smith for placement on the blanket  
directly over the existing labels.  
LOCATING THE HEATER  
WARNING  
THERE IS A RISK IN USING FUEL BURNING APPLIANCES  
SUCH AS GAS WATER HEATERS IN ROOMS, GARAGES OR  
OTHER AREAS WHERE GASOLINE, OTHER FLAMMABLE  
LIQUIDS OR ENGINE DRIVEN EQUIPMENT OR VEHICLESARE  
STORED, OPERATED OR REPAIRED. FLAMMABLE VAPORS  
ARE HEAVY AND TRAVEL ALONG THE FLOOR AND MAY BE  
IGNITED BY THE HEATER’S IGNITER OR MAIN BURNER  
FLAMES CAUSING FIRE OR EXPLOSION. SOME LOCALCODES  
PERMIT OPERATION OF GAS APPLIANCES IF INSTALLED  
18 INCHES (46 cm) OR MORE ABOVE THE FLOOR. THIS  
MAY REDUCE THE RISK IF LOCATION IN SUCH AN AREA  
CANNOT BE AVOIDED.  
FIGURE 3.  
WARNING  
DO NOT USE THIS APPLIANCE IF ANY PART HAS BEEN  
UNDER WATER. IMMEDIATELY CALL A QUALIFIED SERVICE  
TECHNICIAN TO INSPECT THE APPLIANCE AND TO REPLACE  
ANY PART OF THE CONTROLSYSTEMANDANY GAS CONTROL  
WHICH HAS BEEN UNDER WATER.  
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CLEARANCES  
MECHANICAL EXHAUSTING OF ROOM AIR  
Where an exhaust fan is installed in the same room with a heater,  
sufficientopeningsforairmustbeprovidedinthewalls. UNDERSIZED  
OPENINGS WILL CAUSE AIR TO BE DRAWN INTO THE ROOM  
THROUGH THE HEATER’S VENTING SYSTEM, CAUSING POOR  
COMBUSTION. SOOTING MAY RESULT IN SERIOUS DAMAGE  
TO THE HEATER AND RISK OF FIRE OR EXPLOSION. IT CAN  
ALSO CREATE A RISK OF ASPHYXIATION.  
These heaters are approved for installation on combustible flooring  
in an alcove when the minimum clearances from any combustion  
construction are followed as indicated in Figure 4.  
In all installations the minimum combustible clearances from any  
vent piping shall be 0". Vent piping passing through a combustible  
wall or ceiling must be a continuous run (no joints).  
UNCONFINED SPACE  
A service clearance of 24" (61 cm) should be maintained from  
serviceable parts such as relief valves, thermostats, cleanout  
openings, drain valves and venting connections.  
In buildings of conventional frame, brick or stone construction,  
unconfined spaces may provide adequate air for combustion and  
ventilation.  
Always disconnect electrical power before servicing the unit.  
If the unconfined space is within a building of tight construction  
(buildings using the following construction: weather stripping,  
heavy insulation, caulking, vapor barrier, etc.), air for combustion  
and ventilation must be obtained from outdoors. The installation  
instructions for confined spaces in tightly constructed buildings must  
be followed to ensure adequate air supply.  
CONFINED SPACE  
When drawing combustion 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 INCHES (31 cm) OF THE ENCLOSURE TOP AND ONE IN OR  
WITHIN 12 INCHES (31 cm) OFTHE ENCLOSURE BOTTOM. Each  
opening shall have a free area of at least one square inch per 1000  
Btuh (2,203mm/kW) appliances in the enclosure, but not less than  
100 square inches (645 cm²).  
*ILLUSTRATION OF MINIMUM COMBUSTIBLE CLEARANCES  
IN AN ALCOVE.  
FIGURE 4.  
If the confined space is within a building of tight construction, air  
for combustion and ventilation must be obtained from outdoors.  
When directly 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 Btuh (551mm/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 Btuh (1,102mm/kW) of the total input of all  
appliances in the enclosure.  
HARD WATER  
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.  
See MAINTENANCE section for details of tank cleanout procedure.  
AIR REQUIREMENTS  
CHEMICAL VAPOR CORROSION  
KEEP APPLIANCE AREA CLEAR AND FREE OF COMBUSTIBLE  
MATERIALS, GASOLINE AND OTHER FLAMMABLE VAPORS  
AND LIQUIDS.  
WARNING  
CORROSION OF THE FLUE WAYS AND VENT SYSTEM MAY  
OCCUR IF AIR FOR COMBUSTION CONTAINS CERTAIN  
CHEMICAL VAPORS. SUCH CORROSION MAY RESULT IN  
FAILURE AND RISK OF ASPHYXIATION.  
DO NOT OBSTRUCT THE FLOW OF COMBUSTION AND  
VENTILATING AIR.  
Spray can propellants, cleaning solvents, refrigerator and air  
conditioning refrigerants, swimming pool chemicals, calcium  
and sodium chloride, waxes, and process chemicals are typical  
compounds which are potentially corrosive.  
WARNING  
FOR SAFE OPERATION PROVIDE ADEQUATE AIR FOR  
COMBUSTION AND VENTILATION. AN INSUFFICIENT SUPPLY  
OF AIR WILL CAUSE RECIRCULATION OF COMBUSTION  
PRODUCTS RESULTING IN CONTAMINATION THAT MAY BE  
HAZARDOUS TO LIFE. SUCH A CONDITION OFTEN WILL  
RESULT IN A YELLOW, LUMINOUS BURNER FLAME, CAUSING  
CARBONING OR SOOTING OF THE COMBUSTION CHAMBER,  
BURNERS AND FLUE TUBES AND CREATES A RISK OF  
ASPHYXIATION.  
PRODUCTS OF THIS SORT SHOULD NOT BE STORED NEAR  
THE HEATER. ALSO, AIR WHICH IS BROUGHT IN CONTACT  
WITH THE HEATER SHOULD NOT CONTAIN ANY OF THESE  
CHEMICALS. IF NECESSARY, UNCONTAMINATEDAIR SHOULD  
BE OBTAINED FROM REMOTE OR OUTSIDE SOURCES.  
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EXEMPTIONS  
INSTALLATION REQUIREMENTS FOR THE  
COMMONWEALTH OF MASSACHUSETTS  
The following equipment is exempt from 248 CMR 5.08(2)(a)1  
through 4:  
For all side wall terminated, horizontally vented power vent, direct  
vent, and power direct vent gas fueled water heaters installed in every  
dwelling, building or structure used in whole or in part for residential  
purposes, including those owned or operated by the Commonwealth  
and where the side wall exhaust vent termination is less than seven  
(7) feet above finished grade in the area of the venting, including  
but not limited to decks and porches, the following requirements  
shall be satisfied:  
1. The equipment listed in Chapter 10 entitled “Equipment Not  
Required To Be Vented” in the most current edition of NFPA 54  
as adopted by the Board; and  
2. Product Approved side wall horizontally vented gas fueled  
equipment installed in a room or structure separate from the  
dwelling, building, or structure used in whole or in part for  
residential purposes.  
INSTALLATION OF CARBON MONOXIDE DETECTORS  
MANUFACTURER REQUIREMENTS - GAS EQUIPMENT  
VENTING SYSTEM PROVIDED  
At the time of installation of the side wall horizontal vented gas  
fueled equipment, the installing plumber or gasfitter shall observe  
that a hard wired carbon monoxide detector with an alarm and  
battery back-up is installed on the floor level where the gas  
equipment is to be installed. In addition, the installing plumber or  
gasfitter shall observe that a battery operated or hard wired carbon  
monoxide detector with an alarm is installed on each additional  
level of the dwelling, building or structure served by the sidewall  
horizontal vented gas fueled equipment. It shall be the responsibility  
of the property owner to secure the services of qualified licensed  
professionals for the installation of hard wired carbon monoxide  
detectors.  
When the manufacturer of Product Approved side wall horizontally  
vented gas equipment provides a venting system design or venting  
system components with the equipment, the instructions provided  
by the manufacturer for installation of the equipment and the venting  
system shall include:  
1. Detailed instructions for the installation of the venting system  
design or the venting system components; and  
2. A complete parts list for the venting system design or venting  
system.  
In the event that the side wall horizontally vented gas fueled  
equipment is installed in a crawl space or an attic, the hard wired  
carbon monoxide detector with alarm and battery back-up may be  
installed on the next adjacent floor level.  
MANUFACTURER REQUIREMENTS - GAS EQUIPMENT  
VENTING SYSTEM NOT PROVIDED  
When the manufacturer of a ProductApproved side wall horizontally  
vented gas fueled equipment does not provide the parts for venting  
the flue gases, but identifies “special venting systems,” the following  
requirements shall be satisfied by the manufacturer:  
In the event that the requirements of this subdivision can not be  
met at the time of completion of installation, the owner shall have  
a period of thirty (30) days to comply with the above requirements  
provided that during said thirty (30) day period, a battery operated  
carbon monoxide detector with an alarm shall be installed.  
1. The referenced “special venting system” instructions shall  
be included with the appliance or equipment installation  
instructions; and  
APPROVED CARBON MONOXIDE DETECTORS  
Each carbon monoxide detector as required in accordance with the  
above provisions shall comply with NFPA720 and beANSI/UL 2034  
listed and CSA certified.  
2. The “special venting systems” shall be ProductApproved by the  
Board, and the instructions for that system shall include a parts  
list and detailed installation instructions.  
SIGNAGE  
A copy of all installation instructions for all Product Approved  
side wall horizontally vented gas fueled equipment, all venting  
instructions, all parts lists for venting instructions, and/or all  
venting design instructions shall remain with the appliance or  
equipment at the completion of the installation.  
A metal or plastic identification plate shall be permanently mounted  
to the exterior of the building at a minimum height of eight (8) feet  
above grade directly in line with the exhaust vent terminal for the  
horizontally vented gas fueled heating appliance or equipment.  
The sign shall read, in print size no less than one-half (1/2) inch  
in size, “GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL  
OBSTRUCTIONS.”  
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.  
INSPECTION  
The state or local gas inspector of the side wall horizontally vented  
gas fueled equipment shall not approve the installation unless, upon  
inspection, the inspector observes carbon monoxide detectors and  
signage installed in accordance with the provisions of 248 CMR  
5.08(2)(a) 1 through 4.  
Heater must be protected from freezing downdrafts during  
shutdown periods.  
8
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US DIRECT VENT  
CAUTION  
TO PREVENT EXHAUSTING PRODUCTS FROM CIRCULATING TO THE  
AIR INTAKE IN WINDY/COLD AREAS, THE MAXIMUM PRACTICAL  
DISTANCE BETWEEN THESE TWO TERMINALS IS RECOMMENDED.  
CANADIAN DIRECT VENT  
FIGURE 5.  
9
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US HORIZONTAL VENT  
CAUTION  
TO PREVENT EXHAUSTING PRODUCTS FROM CIRCULATING TO THE  
AIR INTAKE IN WINDY/COLD AREAS, THE MAXIMUM PRACTICAL  
DISTANCE BETWEEN THESE TWO TERMINALS IS RECOMMENDED.  
CANADIAN HORIZONTAL VENT  
FIGURE 6.  
ꢀ0  
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WARNING  
WARNING  
NEVER OPERATE THE HEATER UNLESS IT IS VENTED TO THE  
OUTDOORSANDHASADEQUATEAIRSUPPLYTOAVOIDRISKSOF  
IMPROPER OPERATION, FIRE, EXPLOSION OR ASPHYXIATION.  
WHEN THE UNIT IS TO BE SETUP AS A DIRECT VENT,  
THE INTAKE GUARD AND THE BALANCE PLATE MUST BE  
REMOVED. THE INLET VENT PIPE MAY THEN BE GLUED TO  
THE AIR INTAKE (see Figure 8) PROVIDED ON THE UNIT.  
VENT PIPE TERMINATION  
NOTE: Before installing venting, determine place of vent pipe  
termination. See Figure 5 and 6 before proceeding.  
CAUTION  
DO NOT TERMINATE THE VENTING WHERE NOISE FROM  
THE EXHAUST OR INTAKE WILL BE OBJECTIONABLE. THIS  
INCLUDES LOCATIONS CLOSE TO OR ACROSS FROM  
WINDOWS AND DOORS. AVOID ANCHORING THE VENT AND  
INTAKE PIPES DIRECTLY TO FRAMED WALLS, FLOORS OR  
CEILINGS UNLESS RUBBER ISOLATION PIPE HANGERS  
ARE USED. THIS PREVENTS ANY VIBRATIONS FROM BEING  
TRANSMITTED INTO THE LIVING SPACES.  
IMPORTANT  
The vent system must terminate so that proper clearances are  
maintained as cited in local codes or the current editions of the  
National Fuel Gas Code, ANSI Z223.1/NFPA 54 or the Natural Gas  
and Propane Installation Code, CAN/CSA-B149.1.  
Do not terminate the exhaust vent terminal over public area where  
condensate or vapor can cause nuisance or hazard.  
Plan the vent system layout so that proper clearances are maintained  
from plumbing and wiring.  
Vent pipes serving power vented appliances are classified by building  
codes as "vent connectors". Required clearances from combustible  
materials must be provided in accordance with information in this  
manual under LOCATION OF HEATER and CLEARANCES, and  
with National Fuel Gas Code and local Codes.  
FIGURE 8.  
DIRECT VENT TERMINAL INSTALLATION  
IMPORTANT  
IMPORTANT  
4" VENT AND INTAKE TERMINALS ARE PROVIDED FOR  
NEW INSTALLATIONS. FOR REPLACEMENT OF PREVIOUS  
BTH 300 AND 400 WITH 3" TERMINALS, THE 4" TERMINALS  
ARE RECOMMENDED, BUT THE EXISTING 3" VENT/INTAKE  
TERMINALS ARE PERMITTED.  
Plan the layout of the vent system backwards from the vent  
termination to the appliance.  
WARNING  
USE ONLY THE VENT TERMINALS SUPPLIED WITH THIS UNIT.  
TERMINATIONOFAVENTSYSTEMWITHADEVICEOTHERTHAN  
THE SUPPLIED VENT TERMINATIONS WILL AFFECT SYSTEM  
PERFORMANCE AND RESULT IN A SAFETY HAZARD.  
NOTE: TO PREVENT EXHAUSTING PRODUCTS FROM  
CIRCULATING TO THE AIR INTAKE IN WINDY/COLD AREAS,  
THE MAXIMUM PRACTICALDISTANCE BETWEEN THESE TWO  
TERMINALS IS RECOMMENDED.  
DIRECT VENTING  
IMPORTANT  
The air intake provided on the unit contains an intake guard, see  
Figure 7.  
WHEN LOCATING THE TERMINALS ON A SIDEWALL, THE  
FOLLOWING SPECIFICATIONS PERTAINING TO TERMINAL  
LOCATION MUST BE FOLLOWED.  
3"x 4" PVC REDUCER WITH INTAKE SCREEN  
1. The intake vent terminal and the exhaust vent terminal must  
terminate on the same exterior wall and must be located at  
a minimum of 24" (61cm) from the vertical centerline of the  
exhaust vent terminal (see Figure 9). In colder climates  
increasing the 24" (61cm) minimum to 48" (122cm) will  
reduce possibility of frost over from side winds blowing  
exhaust vapors to the air intake of the direct the vent and is  
recommended for Canada.  
FIGURE 7.  
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ꢀꢀ  
Slide the pipe through the wall and insert into coupling on the  
other side of the wall, making sure that the vent terminal ends  
up pointed in the correct position. See Figure 10.  
2. The horizontal centerline of the intake vent terminal may not be  
located lower than the horizontal centerline of the exhaust vent  
terminal (see Figure 9).  
EXHAUST VENT TERMINAL  
FIGURE 9.  
INSTALLATION SEQUENCE  
For installations in the City of Los Angeles, California Category IV  
PVC Pipe such as that manufactured by Brownline Pipe Company,  
must be used as vent pipe material.  
CAUTION  
Vent terminals supplied with the heater must be used.  
NOTE: BEFORE BEGINNING INSTALLATION OF ANY VENT  
PIPE READ THE VENT PIPE MANUFACTURER'S INSTALLATION  
INSTRUCTIONS.  
INTAKE VENT TERMINAL  
FIGURE 10.  
1. After the points of termination have been determined, use the  
cover plates as templates to mark the holes for the vent pipes  
to be inserted through the wall. BEWARE OF CONCEALED  
WIRING AND PIPING INSIDE OF WALL.  
VERTICAL VENT TERMINAL INSTALLATION  
IMPORTANT  
2. If the vent terminals are being installed on the outside of a finished  
wall, it may be easier to mark both the inside and outside wall.  
Align the holes by drilling a hole through the center of the template  
from the inside through to the outside. The template can now be  
positioned on the outside wall using the drilled holes as a centering  
point for the template.  
WHEN TERMINATING THROUGH A ROOF, THE FOLLOWING  
SPECIFICATIONS PERTAINING TO TERMINALLOCATION MUST  
BE FOLLOWED.  
1. Proper support must be provided for all pipe protruding through  
the roof.  
3. A) MASONRY SIDE WALLS  
Chisel an opening approximately 1/2" (1.3 cm) larger than the  
marked circle.  
2. The vertical roof terminations should be sealed with a plumbing  
roof boot or equivalent flashing.  
B) WOODEN SIDE WALLS  
3. The intake vent termination and the exhaust vent termination  
must penetrate the same side of roof.  
Drill a pilot hole approximately one quarter inch outside of the  
marked circle. This pilot hole is used as a starting point for a  
saws-all or sabre saw blade. Cut around the marked circle staying  
approximately one quarter inch outside of the line. (This will allow  
the vent pipe to easily slide through the opening. The resulting  
gap will be covered by the vent terminal cover plates.) Repeat  
this step on the inside wall if necessary.  
4. The center line of the intake vent termination and the center  
line of the exhaust vent termination must be no closer than  
24" (61cm).  
5. The intake vent terminal and the exhaust vent terminal must be  
oriented facing downward and the same direction.  
4. Cut a length of PVC pipe about 3.5" (8.9 cm) longer than the wall  
thickness at the opening.  
The specifications are displayed in Figure 11.  
5. Glue the intake vent terminal to the section of the pipe.  
NOTE: Exhaust vent terminal is installed using the same procedure.  
6. Slide the wall plate over the pipe to stop against intake vent terminal.  
INSTALLATION SEQUENCE  
7. Place a bead of caulking (not supplied) around the gap between  
the pipe and the wall. Place some of the caulking on the back of  
the plate to hold it against the wall after installation.  
NOTE: BEFORE BEGINNING INSTALLATION OF ANY VENT  
PIPE, READ “VENT PIPE PREPARATION” SECTION.  
8. If the vent pipe is installed up to the wall, with a coupling on the  
end against the wall opening, the pipe with the vent terminal  
can be prepared for gluing before inserting through the wall.  
1. After the points of termination have been determined, use the  
cover plates as templates to mark the holes for the vent pipes to  
be inserted through the roof.  
ꢀꢁ  
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2. Drill a pilot hole approximately 1/4" (6 mm) outside of the marked 3. The unit is certified to a minimum amount of 4-inch pipe for  
circle. This pilot hole is used as a starting point for a saws-  
all or sabre saw blade. Cut around the marked circle staying  
approximately one quarter inch outside the line. (This will allow  
the vent pipe to easily slide through the opening). The resulting  
gap will be covered by the roof boot/flashing.  
the exhaust venting arrangement of 15-equivalent feet. This is  
the minimum amount of pipe required for the exhaust venting  
arrangement. The intake venting arrangement is certified to use  
a minimum of 0-equivalent feet of 4-inch PVC pipe.  
IMPORTANT  
3. Suspend the pipe through center of hole using proper support.  
When multiple units are direct vented through a wall (4-inch venting),  
all intake vent terminals should be no lower than the highest exhaust  
vent terminal.  
4. Slide roof boot or equivalent flashing over pipe and secure roof  
boot equivalent flashing to roof.  
5. Seal around flashing.  
NOTE: This unit can be vented using only PVC (Class 160, ASTM  
D-2241 Schedule 40, ASTM D-1785 ; or Cellular Core Schedule  
40 DWV, ASTM F-891) , Schedule 40 CPVC (ASTM F-411), or ABS  
(ASTM D-2661) pipe. The fittings, other than the TERMINATIONS  
should be equivalent to PVC-DWV fittings meeting ASTM D-2665  
(Use CPVC fittings, ASTM F-438 for CPVC pipe and ABS fittings,  
ASTM D-2661/3311 for ABS pipe. If CPVC or ABS pipe and fittings  
are used, then the proper cement must be used for all joints, including  
joining the pipe to the Termination (PVC Material). PVC Materials  
should use ASTM D-2564 Grade Cement; CPVC Materials should  
use ASTM F-493 Grade Cement and ; ABS Materials should use  
ASTM D-2235 Grade Cement.  
6. Terminate intake terminal and exhaust vent terminal facing down.  
See Figure ꢀꢀ.  
NOTE: for Water Heaters in locations with high ambient  
temperatures (above 100°F or 38°C) and/or insufficient dilution air,  
it is recommended that CPVC or ABS pipe and fittings (MUST USE  
SUPPLIED VENT TERMINAL) be used.  
FIGURE 11.  
INSTALLATION OF VENT SYSTEM  
5. It is important that condensate not be allowed to buildup in the  
exhaust vent pipe. To prevent this from happening the pipe should  
be installed with a slight, 1/8 inch (3mm) per 5 feet (152 cm) of  
pipe maximum downward slope.  
WARNING  
THE OPTIONAL INTAKE VENTING ARRANGEMENT AND THE  
EXHAUST VENTING ARRANGEMENT MUST BE INSTALLED TO  
RUN DIRECTLY TO THE OUTDOORS AND NOT IN ANY WAY BE  
CONNECTED TOANOTHER VENTING SYSTEM (I.E. FURNACE,  
DRYERS OR SPACE HEATERS). IT IS CRUCIAL THAT THE  
VENTING ARRANGEMENT BE KEPT SEPARATE FROM OTHER  
VENTING SYSTEMS. IF THIS WARNING IS IGNORED, AND THE  
SYSTEM IS VENTED INCORRECTLY, IT MAY CAUSE IMPROPER  
OPERATION, FIRE, EXPLOSION, OR ASPHYXIATION.  
6. Theventsystemshouldbesupportedevery5feet(152cm)ofvertical  
run and every 3 feet (91cm) of horizontal run of vent pipe length.  
NOTE: Stress levels in the pipe and fittings can be significantly  
increased by improper installation. If rigid pipe clamps are used to  
hold the pipe in place, or if the pipe cannot move freely through a  
wall penetration, the pipe may be directly stressed, or high thermal  
stresses may be formed when the pipe heats up and expands. Install  
accordingly to minimize such stresses.  
1. Plan the route of the vent system from the vent termination to the  
planned location of the appliance. Layout the total vent system  
to use the minimum of vent pipe and elbows possible.  
2. This unit is certified for the use of 4-inch PVC pipe for venting.  
The maximum length of 70-equivalent feet of 4-inch PVC pipe  
may be used for the intake venting arrangement and a maximum  
length of 70-equivalent feet of 4-inch PVC pipe may be used on  
the exhaust venting arrangement. If the supply gas pressure  
(dynamic) is set between 7" wc - 9" wc, the maximum allowed  
length is 80 equivalent feet for both air intake and exhaust venting.  
The maximum number of 90 degree elbows for the 4-inch venting  
is six (6) in the intake and six (6) on the exhaust. A 90 degree  
elbow is equal to five (5) equivalent feet of 4-inch pipe. One 90  
degree elbow is equaled to two 45 degree elbows.  
INLET VIEW  
Table 2. VENT LENGTH TABLE  
Number  
of 90°  
Elbows  
4" PVC  
Maximum  
Feet. of Pipe  
Maximum  
Meters of Pipe  
ONE (1)  
TWO (2)  
THREE (3)  
FOUR (4)  
FIVE (5)  
SIX (6)  
65'  
60'  
55'  
50'  
45'  
40'  
19.7 m  
18.2 m  
16.7 m  
15.2 m  
13.6 m  
12.1 m  
OUTLET VIEW  
FIGURE 12.  
ꢀ3  
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contacts are normally open. When the fan increases the pressure  
in the burner, the pressure switch will allow the electrical contacts  
to close. The pressure switch is connected to the burner tap by a  
piece of tygon tubing. This tubing must be connected in order for  
the switch to change the electrical contacts. The controller requires  
that the electrical contacts on this air flow switch be open before it  
will allow the blower to come on. See Figure 13.  
VENT PIPE PREPARATION  
ꢀ. INITIAL PREPARATION  
A. Make sure the solvent cement you are planning to use is  
designed for the specific application you are attempting.  
B. Know the physical and chemical characteristics and limitations  
of the PVC, PVC cellular core,ABS or CPVC piping materials  
that you are about to use.  
BLOCKED OUTLET PROVER SWITCH  
The Blocked Outlet Prover Switch is set up to shut the unit off when  
a build-up of positive pressure in the exhaust vent pipe occurs.  
This switch is a positive pressure switch that requires an increase  
in pressure to change the electrical contacts from normally closed  
to open. When this switch prevents the unit from igniting, most  
likely the exhaust is blocked by some means. Check to see if the  
condensate is allowed to flow freely from the exhaust elbow and  
for obstructions in the exhaust venting and exhaust vent terminal.  
See Figure ꢀ3.  
C. Know the reputation of your pipe and cement manufacturer  
and their products.  
D. Know your own qualifications or those of your contractor. The  
solvent welding technique of joining PVC, PVC cellular core,  
ABS or CPVC pipe is a specialized skill just as any other pipe  
fitting technique.  
E. Closely supervise the installation and inspect the finished  
job before start-up.  
BLOCKED INLET PROVER SWITCH  
F. Contact the manufacturer, supplier, or competent consulting  
agency if you have any questions about the application or  
installation of PVC, PVC cellular core, ABS or CPVC pipe.  
The Blocked Inlet Prover Switch is set up to shut the unit off when  
a build-up of negative pressure in the intake vent pipe occurs. This  
switch is a negative pressure switch that requires an increase in  
negative pressure to change the electrical contacts from normally  
closed to open. The switch is connected to the pressure tap on  
the flange connected to the inlet of the blower. When this switch  
prevents the unit from igniting, most likely the intake is blocked by  
some means. Check to see if there is no more than seventy (70)  
equivalent feet (24.8m) of four inch PVC vent pipe on the intake.Also  
verify that the intake and intake vent terminal is free of obstructions  
that may prevent air from entering the unit. See Figure 13.  
G. Take the time and effort to do a professional job. Shortcuts will  
only cause you problems and delays in start-up. The majority  
of failures in these systems are the result of shortcuts and/or  
improper joining techniques.  
2.  
SELECTION OF MATERIALS  
PRIMER  
It is recommended that Tetrahydrofuran (THF) be used to prepare the  
surfaces of pipe and fittings for solvent welding. Do not use water, rags,  
gasoline or any other substitutes for cleaning PVC cellular core, ABS or  
CPVC surfaces. A chemical cleaner such as MEK may be used.  
LOW GAS PRESSURE SWITCH  
The Low Gas Switch (LGS) is a single-pole, normally open pressure  
switch that will close its contacts when a rising pressure of 4.6 in.  
W.C. (1.25 Kpa) is encountered. The contacts will open when the  
pressure falls below the fixed set point of 4.6 in. W.C. (1.25 Kpa)  
The LGS monitors the gas supply pressure to the heater. If the  
gas supply falls below 4.6 in. W.C. (1.25 Kpa), the main burner is  
extinguished (if heater is running) or the heater will not start up.  
NOTE: LOW GAS SWITCH IS LOCATED ON INLET SIDE OF GAS  
VALVE. See Figure ꢀ3.  
CEMENT  
The cement should be a bodied cement of approximately 500 to  
1600 centipoise viscosity containing 10-20% (by weight) virgin PVC  
material solvated with tetrahydrofuran (THF). Small quantities of  
dimethyl formamide (DMF) may be included to act as a retarding  
agent to extend curing time. Select the proper cement; Schedule 40  
cement should be used for Schedule 40 pipe. Never use all purpose  
cements, commercial glues and adhesives or ABS cement to join  
PVC or CPVC pipe and fittings.  
SAFETY PRECAUTION: PRIMERS AND CEMENTS ARE  
EXTREMELY FLAMMABLE AND MUST NOT BE STORED OR  
USED NEAR HEAT OR OPEN FLAME. ALSO, USE ONLY IN A  
WELL-VENTILATED AREA.  
CONTROLS AND SWITCHES  
The BTH-300, 400 & 500 are equipped with four pressure switches.  
These switches are essential to the safe and proper operation of the  
unit. All switches are wired in series. The controller is set up to shut  
the unit down whenever there is a failure of any of the switches. It  
is important to understand the purpose of each switch.  
FIGURE 13.  
BLOWER PROVER SWITCH  
ON/OFF SWITCH  
The Blower Prover Switch is provided on the heater to verify that The ON/OFF Switch is a single-pole, single-throw rocker switch. This  
the fan is operating. It is a positive pressure switch whose electrical switch provides 120VAC from the line source to the heater.  
14  
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CAUTION  
WARNING  
THE WATER HEATER IS POLARITY SENSITIVE. BEFORE  
APPLYING ELECTRICITY TO THIS HEATER BE CERTAIN THAT  
SUPPLY NEUTRALWIRE TO GROUND CHECK INDICATES ZERO  
VOLTAGE.  
THE HEATER IS NOT INTENDED FOR OPERATION AT HIGHER  
THAN 11.0" WATER COLUMN (2.74 Kpa) FOR NATURALGASAND  
14.0" W.C. (3.49kPa) FOR PROPANE GAS SUPPLY PRESSURE.  
HIGHER GAS SUPPLY PRESSURES REQUIRE SUPPLEMENTAL  
REDUCING SERVICE REGULATION. EXPOSURE TO HIGHER  
GAS SUPPLY PRESSURE MAY CAUSE DAMAGE TO THE GAS  
CONTROLS 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. VENTBLOCKAGE MAYOCCUR DURING ICE STORMS.  
IT IS IMPORTANT TO GUARD AGAINST GAS VALVE FOULING  
FROM CONTAMINANTS IN THE GAS WAYS. SUCH FOULING  
MAY CAUSE IMPROPER OPERATION, FIRE OR EXPLOSION.  
HOT SURFACE IGNITER  
The Hot Surface Igniter is a device that ignites the main burner by  
high temperature (>1800°F or >982°C). When 120VAC is applied  
to the igniter, sufficient heat is generated to ignite the main burner.  
Although improvements have been made to strengthen the igniter,  
it is fragile and care must be taken when handling the igniter to  
prevent breakage.  
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.  
Size the main gas line in accordance with Table 3. The figures  
shown are for straight lengths of pipe at 0.5 in. W.C. (125Pa)  
pressure drop, which is considered normal for low pressure  
systems Note that fittings such as elbows and tees will add to the  
pipe pressure drop.  
BEFORE ATTACHING THE GAS LINE BE SURE THAT ALL GAS  
PIPE IS CLEAN ON THE INSIDE.  
TO TRAP ANY DIRT OR FOREIGN MATERIAL IN THE GAS  
SUPPLY LINE, A DIRT LEG (SOMETIMES CALLED A SEDIMENT  
TRAP OR DRIP LEG) MUST BE INCORPORATED IN THE PIPING  
(SEE FIG. 14). 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 NATIONAL FUEL GAS CODE NFPA  
54 OR THE NATURAL GAS AND PROPANE INSTALLATION  
CODE CAN/CSA-B149.1.  
CAUTION  
DO NOT USE FLEXIBLE GAS PIPING.  
TABLE 3. MAXIMUM CAPACITY OF PIPE IN CUBIC FEET OF GAS  
PER HOUR (Based upon a Pressure Drop of 0.5 inch Water Column  
and 0.6 Specific Gravity Gas and max. gas pressure of 0.5 psig).  
LENGTH  
IN  
NORMAL IRON PIPE SIZES (INCHES)  
INPUT IN THOUSANDS BTU/HR  
FEET  
10  
20  
30  
40  
50  
60  
70  
80  
1 1/4"  
1400  
950  
770  
660  
580  
530  
490  
460  
430  
400  
360  
325  
300  
1 1/2"  
2100  
1460  
1180  
990  
900  
810  
750  
690  
650  
620  
550  
500  
460  
430  
2"  
2 1/2"  
6300  
4360  
3520  
3000  
2650  
2400  
2250  
2050  
1950  
1850  
1650  
1500  
1370  
1280  
3"  
4"  
3960  
2750  
2200  
1900  
1680  
1520  
1400  
1300  
1220  
1150  
1020  
950  
11000  
7700  
6250  
5300  
4750  
4300  
3900  
3700  
3450  
3250  
2950  
2650  
2450  
2280  
23000  
15800  
12800  
10900  
9700  
8800  
8100  
7500  
7200  
6700  
6000  
5500  
5000  
4600  
90  
FIGURE 14.  
100  
125  
150  
175  
200  
CONNECTION OF GAS PIPE  
850  
800  
1. When connecting gas pipe to unit, apply wrench to flange only.  
Note: Do not use wrench on gas valve or gas bracket.  
LENGTH  
IN  
NORMAL IRON PIPE SIZES (INCHES)  
INPUT IN KW  
2. PERFORM THE GAS LEAK TEST ANY TIME WORK IS DONE  
ON A GAS SYSTEM TO AVOID THE POSSIBILITY OF FIRE OR  
EXPLOSION WITH PROPERTY DAMAGE, PERSONALINJURY  
OR LOSS OF LIFE.  
METERS 1 1/4"  
1 1/2"  
615  
428  
346  
290  
264  
237  
220  
202  
190  
182  
161  
146  
135  
126  
2"  
1160  
805  
644  
556  
492  
445  
410  
381  
357  
337  
299  
278  
249  
234  
2 1/2"  
1845  
1277  
1031  
878  
776  
703  
659  
600  
571  
542  
483  
439  
401  
375  
3"  
4"  
3.0  
6.1  
9.1  
410  
278  
225  
193  
170  
155  
143  
135  
126  
117  
105  
95  
3221  
2255  
1830  
1552  
1391  
1259  
1142  
1083  
1010  
952  
6735  
4626  
3748  
3192  
2840  
2577  
2372  
2196  
2108  
1962  
1757  
1610  
1464  
1347  
12.2  
15.2  
18.3  
21.3  
24.4  
27.4  
30.5  
38.1  
45.7  
53.3  
61.0  
The Gas Leak Test is performed as follows: Paint pipe connections  
upstream of gas control with a rich soap and water solution to test  
for leaks before operating main burner. Bubbles indicate gas leak.  
To stop leak, tighten pipe connections. After piping connections are  
checked, turn on main burner. With main burner in operation, paint  
pipe joints (including flanges), pilot gas tubing connections and  
control inlet and outlet with rich soap and water solution. Bubbles  
indicate gas leak. To stop leak, tighten flange screws, joints and pipe  
connections. Replace part if leak can’t be stopped.  
864  
776  
717  
688  
88  
ꢀ5  
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To prevent damage, care must be taken not to apply too much torque  
when attaching gas supply pipe to gas valve inlet.  
RELIEF VALVE  
This heater is equipped with an approved temperature and pressure  
relief valve. ASME ratings cover pressure relief. CSA ratings cover  
release rate with temperature actuation.  
Apply joint compounds (pipe dope) sparingly and only to the  
male threads of pipe joints. Do not apply compound to the first  
two threads. Use compounds resistant to the action of liquefied  
petroleum gases.  
FOR SAFE OPERATION OF THE WATER HEATER, THE RELIEF  
VALVE(S) MUST NOT BE REMOVED OR PLUGGED.  
DISCONNECT THE APPLIANCE AND ITS MANUAL GAS  
SHUTOFF VALVE FROM THE GAS SUPPLY PIPING SYSTEM  
DURING ANY SUPPLY PRESSURE TESTING EXCEEDING 1/2  
PSIG (3.45Kpa). GAS SUPPLY LINE MUST BE CAPPED WHEN  
DISCONNECTED FROM THE HEATER. FOR TEST PRESSURES  
OF 1/2 PSIG (3.45Kpa) OR LESS, THE APPLIANCE NEED NOT  
BE DISCONNECTED, BUT MUST BE ISOLATED FROM THE  
SUPPLY PRESSURE TEST BY CLOSING THE MANUAL GAS  
SHUTOFF VALVE.  
In addition to the appliance relief valve, each remote storage tank  
which may be used in conjunction with this appliance shall also be  
installed with a properly sized, rated and approved temperature  
(ANSI) and pressure (ASME) relief valve(s). This relief valve shall  
comply with the standard for relief valves and automatic gas shutoff  
devices for hot water supply systems. ANSI Z21.22-CSA 4.4.  
Your local code authority may have other specific relief valve  
requirements.  
BEFORE PLACING THE HEATER IN OPERATION, CHECK FOR  
GAS LEAKAGE. USE SOAPAND WATER SOLUTION OR OTHER  
WARNING  
MATERIAL ACCEPTABLE FOR THE PURPOSE OF LOCATING THE PURPOSE OF A RELIEF VALVE IS TO AVOID EXCESSIVE  
GAS LEAKS. DO NOT USE MATCHES, CANDLES, FLAME OR PRESSURE OR TEMPERATURE INTO THE STEAM RANGE,  
OTHER SOURCES OF IGNITION FOR THIS PURPOSE.  
WHICHMAYCAUSESCALDINGATFIXTURES,TANKEXPLOSION,  
SYSTEM OR HEATER DAMAGE. NO VALVE IS TO BE PLACED  
BETWEEN THE RELIEF VALVE AND THE TANK.  
PURGING  
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 OUTLETAND MUST  
NOT CONTAIN VALVES OR 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.  
THE DISCHARGE LINE SHALL BE INSTALLED TO ALLOW  
COMPLETE DRAINAGE OF BOTH THE VALVE AND LINE.  
Gas line purging is required with new piping or systems in which  
air has entered.  
CAUTION  
PURGINGSHOULDBEPERFORMEDBYPERSONSEXPERIENCED  
IN THIS TYPE OF GAS SERVICE. TO AVOID RISK OF FIRE OR  
EXPLOSION, PURGE DISCHARGE MUSTNOTENTER CONFINED  
AREAS OR SPACES WHERE IGNITION CAN OCCUR. THE AREA  
MUST BE WELL VENTILATED AND ALL SOURCES OF IGNITION  
MUST BE INACTIVATED OR REMOVED.  
GAS METER SIZE - CITY GASES ONLY  
WATER LINE CONNECTIONS  
Be sure that 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 the gas meter  
is too small, ask the gas company to install a larger meter having  
adequate capacity.  
This manual provides detailed installation diagrams (see back  
section of this manual) for typical methods of application for the  
water heaters.  
The water heater may be installed by itself, or with a separate storage  
tank. When used with a separate storage tank, the circulation may be  
either by gravity or by means of circulating pump. When a circulating  
pump is used, it is important to note that the flow rate should be slow  
so that there will be a minimum of turbulence inside the heater.  
GAS VALVES  
WARNING  
SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAIL  
TO SHUT OFF, TURN OFF THE MANUAL GAS CONTROL VALVE  
TO THE APPLIANCE.  
CLOSED SYSTEM  
CAUTION  
SYSTEM CONNECTIONS  
Aclosed 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).  
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.  
Excessive pressure may develop causing premature tank failure or  
intermittent relief valve operation. This type of failure is not covered  
by the limited warranty. An expansion tank or a similar device may  
THERMOMETERS (Not Supplied)  
Thermometers should be obtained and field installed as shown in be required in the inlet supply line between the appliance and the  
the installation diagrams.  
meter or valve to compensate for the thermal expansion of water  
under supply pressure.  
Thermometers are installed in the system as a means of detecting  
the temperature of the outlet water supply.  
If a water heater is installed in a closed water system, check local  
16  
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codes or contact the water supplier or local plumbing inspector on  
how to control this situation.  
CLEAN ELECTRICITY FOR PROPER OPERATION. INSTALLING  
THE HEATER ON A BRANCH CIRCUIT THAT HAS ELECTRONIC  
NOISE, IS SUBJECT TO FLUCTUATIONS IN VOLTAGE LEVEL  
OR HAS AN APPLIANCE WHICH GENERATES EMF OF  
RFI INTERFERENCE CAN CAUSE THE CONTROLLER TO  
MALFUNCTION. A HIGH QUALITY POWER CONDITIONER  
MUST BE INSTALLED IF THE ABOVE CONDITIONS EXIST.  
MALFUNCTIONS CAUSED BY A POOR ELECTRICAL SUPPLY  
ARE NOT COVERED UNDER YOUR WARRANTY.  
WATER (POTABLE) HEATING AND SPACE HEATING  
1. All piping components connected to this unit for space heating  
applications shall be suitable for use with potable water.  
2. Toxic chemicals, such as those used for boiler treatment, shall  
NEVER be introduced into this system.  
The controller is wired to the heater as shown in figures 15 & 16. The  
model and rating plate provides the electrical information needed to  
size the complete heater branch supply.  
3. This unit may never be connected to any existing heating system  
or component(s) previously used with non-potable water heating  
appliance.  
All electrical work must be installed in accordance with the National  
4. Whenthesystemrequireswaterforspaceheatingattemperatures Electrical Code, NFPA 70 or the Canadian Electrical Code, CSA  
higher than required for domestic water purposes, a tempering  
valve must be installed. Please refer to installation diagrams  
on pages 30 through 35 in back of manual for suggested piping  
arrangements.  
C22.1 and local requirements.  
When installed, the appliance must be electrically grounded in  
accordance with local codes or, in the absence of local codes,  
with the National Electrical Code, ANSI/NFPA 70 or the Canadian  
Electrical Code, CSA C22.1.  
HEATER WIRING  
DO NOT ENERGIZE THE BRANCH CIRCUIT BEFORE THE  
HEATER TANK IS FILLED WITH WATER.  
IF ANY OF THE ORIGINAL WIRE AS SUPPLIED WITH THE  
APPLIANCE MUST BE REPLACED, IT MUST BE REPLACED  
WITH 105°C OR ITS EQUIVALENT, EXCEPT IN THE BURNER  
HOUSING. IN THIS CASE USE 200°C WIRE.  
NOTE: This controller is Polarity Sensitive. If the Hot and Neutral  
Supply Voltage is reversed, the controller will not sense flame. Verify  
polarity before connecting the unit.  
THE COMPUTER CONTROL REQUIRES A SOURCE OF STABLE  
ꢀ7  
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BTH 300 WIRING DIAGRAM  
FIGURE 15.  
ꢀ8  
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BTH 400 AND 500 WIRING DIAGRAM  
FIGURE 16.  
ꢀ9  
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inside the tank. The second temperature on this screen is the  
Operating Set Point. The Operating Set Point is the temperature  
at which the water heater will maintain the water inside the tank.  
The third line on the screen is a text description of the Operational  
State of the water heater (please see Operating States for more  
details).  
OPERATION  
SEQUENCE OF OPERATION  
Typical Control/Appliance Operating Sequence  
1. When the control is powered, it should display the unit model,  
water temperature, setting temperature and heater status.  
2. If the control determines that the actual water temperature inside  
the tank is below the programmed temperature setpoint less the  
differential, a call for heat is activated.  
3. The control then performs selected system diagnostic checks.  
This includes confirming the proper state of the air/gas switches  
and ECO limit device.  
4. If all checks are successfully passed, the combustion blower is  
energized for the pre-purge cycle.  
5. When the pre-purge cycle is complete, power is applied to the  
ignitor element for the ignitor warm-up period.  
6. At the conclusion of the igniter warm-up period, the gas valve  
will open, allowing gas to enter the burner chamber.  
7. The igniter will remain on for a short predetermined time period,  
then will be turned off.  
The row of status icons describe graphically operational details  
of the heater. Following is a legend of all the status icons:  
8. The control will monitor the flame sense probe to confirm a  
flame is present. If a flame is not verified within predetermined  
time period, the gas valve will immediately be closed, and  
the blower will continue to run for approximately 30 seconds  
interpurge. The control will try for ignition two more times  
before lockout.  
9. If a flame is confirmed, the control will enter the heating mode  
where it will continue heating the tank water until the setpoint  
temperature plus differential is reached. At this point, the gas  
valve is closed and the control enters the post-purge cycle.  
10. The combustion blower will run for the duration of the post purge  
cycle to purge the system of all combustion gases. When the  
post purge cycle is complete, the blower is de-energized and  
will coast to a stop.  
11. The control will now enter the idle state while continuing to  
monitor the internal tank water temperature and the state of other  
system devices. If the temperature drops below the setpoint  
value less differential, the control will automatically return to  
step 2 and repeat the entire operating cycle.  
ELECTRONIC CONTROL  
ꢀ. Overview  
Interaction with the water heater controller is done through an up,  
a down and three operation buttons. These buttons are shown  
in the following illustration. Operation of the three lower buttons  
is defined immediately above them on the screen. The UP and  
DN buttons are used to navigate through the menus and make  
adjustments to the water heater.  
While the water heater is operating, the user interface will display ꢁ. Operating States  
the desktop screen (if there are no active faults or warnings). An  
example of this screen is shown in the following illustration. The  
first temperature on this screen is the temperature of the water  
In the main desktop screen, there are some specific Operating  
States that are indicated on the status line. These are summerized  
in the following table:  
ꢁ0  
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3. Adjusting the Operating Set Point  
The Operating Set Point of this water heater determines the regulated temperature for the water in the tank. This parameter is adjusted  
in the Temperature menu. Items in this menu allow you to monitor different temperature readings in the tank along with adjusting the  
Operating Set Point and Differential.  
ꢁꢀ  
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4. Changing the Display Units  
The display interface to the heater has the option of selecting between degrees and Fahrenheit and degrees Celsius for temperature  
displays. This can be found in the "Display Settings" menu. Also in this menu, you may adjust how the backlight operates and the  
contrast of the LCD screen.  
5. Fault and Warning Conditions  
This water heater is equipped with electronic controls that have the ability to monitor almost all aspects of the water heater operation. In  
the case that there is an undesirable or unsafe condition that occurs, the water heater controls will detect this condition and determine  
the appropriate action. Part of this is displaying the information on the LCD in plain text that accurately describes the condition and  
diagnostics information that can be used to correct the issue.  
There are two types of conditions that can occur during operation. These are: Warnings and Faults:  
Warnings: This is a non-safety related condition that the control has detected that may cause the water heater to operate in a less  
than optimal condition, but does not pose a safety concern.  
NOTE: When these conditions occur, continued heating cycles will continue and the heater will attempt to regulate the water in the  
tank to the Operating Set Point.  
Example of a Warning:  
ꢁꢁ  
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Faults: This is a safety related condition that has been detected by the heater.  
NOTE: When these conditions occur, the water heater will not continue any further heating cycles and the water will no longer be  
heated until the condition is corrected and, in most cases, power has been cycled.  
Example of a Fault:  
Advanced Diagnostics Information  
When a fault or warning has been declared, advanced information can be found in the control. By pressing the Advanced button,  
detailed information can be found regarding diagnosing and resolving the problem.  
WARNING: Usage of the Advanced information requires ability equivalent to that of a license tradesmen in the  
field involved.  
6. Access to the Current Fault or Warning  
When a fault or warning has been detected by the control, it will automatically be displayed on the screen and the back light will  
blink. If you choose to leave the current fault or warning by pressing the Back key, you can always return to the fault screen through  
the menu.  
ꢁ3  
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7. Viewing the Fault History  
The controller for this water heater will store a history of ten of the last Fault and Warning conditions that occurred. This is stored in the  
Fault History. Along with all the information about the fault, including a estimate time of when the fault occurred, information regarding  
the advanced diagnostics for that fault can be accessed at any time.  
8. Viewing Information About the Heater  
The electronic control for this water heater monitors many different aspects of the water to ensure safe and optimal operation. Much  
of the information monitored is available to view in two areas of the control. The first is the "Heater Status" and; the second is "Heater  
Information". These items can be selected through the main menu in the same fashion as described above. In these menus, detailed  
information about the water heater and the current status of specific conditions can be found.  
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DO NOT USE THIS HEATER IF ANY PART HAS BEEN UNDER  
WATER.IMMEDIATELYCALLAQUALIFIEDSERVICETECHNICIAN  
TO INSPECT THE HEATER AND TO REPLACE ANY PART OF THE  
CONTROL SYSTEM AND ANY GAS CONTROL WHICH HAS BEEN  
UNDER WATER.  
PRIOR TO START UP - REQUIRED ABILITY  
INSTALLATIONORSERVICEOFTHISWATERHEATERREQUIRES  
ABILITY EQUIVALENTTO THAT OFALICENSED TRADESMAN IN  
THE FIELD INVOLVED. PLUMBING,AIR SUPPLY, VENTING, GAS  
SUPPLY AND ELECTRICAL WORK ARE REQUIRED.  
LIGHT THE UNIT IN ACCORDANCE WITH THE OPERATING  
Before attempting start-up, thoroughly study and familiarize yourself INSTRUCTIONS LABEL ATTACHED TO THE HEATER.  
with the exact sequence of operation and all other details on the  
specific heater being used.  
THESE INSTRUCTIONSARE REPEATED IN THE LIGHTINGAND  
OPERATING LABEL ILLUSTRATION IN THIS MANUAL.  
The power burner is equipped with an ignition system which  
automatically sequences prepurge and ignition, senses and  
ignites main burner flame and sequences burner operation.  
Heater is equipped with an ignition control which locks out after  
three unsuccessful ignition attempts. Familiarize yourself with the  
sequence of operation of this unit prior to start-up.  
ADJUSTMENT PROCEDURE - INITIAL START-UP  
A minimum dynamic gas supply pressure of 5.2" W.C. (1.29 kPa)  
for Natural Gas and 11" W.C. (2.74 kPa) for LP Gas is required  
before making any adjustment to the gas control pressure regulator  
Attempts to adjust the regulator during periods of low gas supply  
pressure could result in overfiring of the heater when the gas supply  
pressure returns to normal.  
Be certain that the water heater is full of water, that air is purged  
from all lines, there are no leaks (gas and water), and all inlet water  
lines are open.  
1. Check gas line pressure with a manometer, adjust the gas supply  
line pressure per table 4.  
2. Check manifold pressure (see Table 4) using a pressure gauge  
(manometer) connected to the manifold pressure tap on the gas  
control valve, (Figure 15).  
The following test equipment should be on hand (all test  
equipment must be acclimated to ambient temperature before  
calibration and use.)  
– Two U-tube manometers or calibration 0-10" W.C. (0-2.5Kpa) and  
0-35" W.C. (0-8.7Kpa) pressure gauges.  
Attach a gas pressure gauge or manometer to the upstream side  
of main gas cock and a gas pressure gauge or manometer to the  
manifold pressure tap.  
If full rate adjustment is required, remove cover screw from top of  
the gas control valve, (Figure 15).  
You are now ready to begin the burner start-up procedure.  
Using a small screwdriver, turn adjusting screw clockwise  
to  
increase or counterclockwise to decrease gas pressure to  
obtain 4.0" W.C. (0.996 kPa) for Natural Gas and 10" W.C. (2.49  
kPa) for LP gas.  
OPERATING INSTRUCTIONS  
IMPORTANT  
IT IS RECOMMENDED THAT A QUALIFIED SERVICE TECHNICIAN  
PERFORMTHEINITIALFIRINGOFTHEHEATER.ATTHISTIMETHE  
USERSHOULDASKTHETECHNICIANANYQUESTIONSINREGARD  
TO THE OPERATION AND MAINTENANCE OF THE UNIT.  
3. Cycle the burner on and off several times to check its operation.  
4. Check the operation of the limit and operating controls.  
5. Check the vent system seams and joints and ensure that there  
is no discharge of flue products into the room.  
6. Check the input rate:  
CAUTION  
For appliance installation locations with elevations above 10,000  
feet (3,048 m) refer to HIGH ALTITUDE INSTALLATIONS section  
of this manual.  
BEFORE PROCEEDING WITH THE OPERATION OF THE UNIT,  
MAKE SURE HEATER AND SYSTEM ARE FILLED WITH WATER  
AND ALL AIR IS EXPELLED FROM HEATER AND PIPING.  
a. Attach a pressure gauge (manometer) to the manifold pressure  
tap (Figure 16) and refer to Table 4 for correct pressure.  
NEVER OPERATE THE HEATER WITHOUT FIRST BEING  
CERTAIN IT IS FILLED WITH WATERANDATEMPERATUREAND  
APRESSURERELIEFVALVEISINSTALLEDINTHERELIEFVALVE  
OPENING OF THE HEATER. DO NOT ATTEMPT TO OPERATE  
HEATER WITH COLD WATER INLET VALVE CLOSED.  
b. Use this formula to “clock” the meter. Be sure other gas  
consuming appliances are not operating during this interval.  
3600  
T
3600 X  
12.6  
FILLING:  
1. Close the heater drain valve.  
X H = Btuh  
1050 = 300,000 Btuh (87.9 kW)  
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.  
4. Close the hot water faucet as water starts to flow.  
5. The heater is ready to be operated.  
T = Time in seconds to burn 1 cubic foot of gas. (With a stopwatch  
read the gas meter and measure the amount of time required for  
the heater to consume 1 cubic foot of gas.)  
H = Heating value of gas (in Btu’s per cubic foot of gas).  
Btuh = Actual heater input rate, in Btuh.  
EXAMPLE: (Using BTH-300 heater)  
T = 12.6 seconds  
THEMAINMANUALGASSHUTOFFVALVEMUSTHAVEBEENCLOSED  
FOR AT LEAST FIVE (5) MINUTES. THIS WAITING PERIOD IS AN  
IMPORTANTSAFETYSTEP. ITS PURPOSE ISTO PERMITGASTHAT  
MIGHT HAVE ACCUMULATED IN THE COMBUSTION CHAMBER TO  
CLEAR.IFYOUDETECTGASATTHEENDOFTHISPERIOD,DONOT  
PROCEEDWITHLIGHTING. RECOGNIZETHATGASODOR, EVENIF  
ITSEEMSWEAK,MAYINDICATETHEPRESENCEOFACCUMULATED  
GASSOMEPLACEINTHEAREAWITHARISKOFFIREOREXPLOSION.  
SEETHE FRONTPAGE FOR STEPSTO BETAKEN.  
H = ꢀ050 Btu/ft.3  
BTUH = ?  
For high altitude installations, compare result to the derated input  
required for the elevation at the installation location.  
Should it be necessary to adjust the gas pressure to the burner,  
to obtain the full input rate, the steps below should be followed:  
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c. Remove the pressure regulator cover screw (Figure 16) and  
adjust the pressure by turning the adjusting screw with a small  
screwdriver. In this example, with heater running on natural  
gas, do not exceed 4.0" (0.996 kPa) Water Column.  
e. Repeat steps (c) and (d) until the specified input rate is  
achieved.  
f. Turn the manual gas valve to “OFF”. Replace the pressure  
regulator cover screw. Remove the pressure gauge or  
manometer from the manifold pressure tap. Replace the  
set screw in the manifold pressure tap. If the gas pressure  
regulator cannot be adjusted to give the full input rating with  
sufficient gas pressure at the valve, check to ensure the  
unit is equipped with the correct orifice.  
Clockwise to increase gas pressure and input rate.  
Counterclockwise to decrease gas pressure and input rate.  
d. “Clock” the meter as in step (b) above.  
LIGHTING AND OPERATION INSTRUCTIONS  
FOR YOUR SAFETY READ BEFORE OPERATING  
IF YOU DO NOT FOLLOW THESE INSTRUCTIONS EXACTLY A FIRE OR EXPLOSION  
MAY RESULT CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR LOSS OF LIFE.  
WARNING  
telephone. Follow the gas supplier’s instructions.  
If you cannot reach your gas supplier, call the fire  
department.  
A.  
This appliance does not have a pilot. It is equipped with  
an ignition device which automatically lights the burner.  
Do not try to light the burner by hand.  
C.  
Use only your hand to push in or turn the gas control  
knob. Never use tools. If the knob will not push in or  
turn by hand, don’t try to repair it, call a qualified service  
technician. Force or attempted repair may result in fire  
or explosion.  
B.  
BEFORE OPERATING smell all around the appliance area  
for gas. Be sure to smell next to the floor because some  
gas is heavier than air and will settle on the floor.  
“WHAT TO DO IF YOU SMELL GAS”  
D.  
Do not use this appliance if any part has been under water.  
Immediately call a qualified service technician to inspect  
the appliance and to replace any part of the control system  
and any gas control which has been under water.  
Do not try to light any appliance.  
Do not touch any electric switch; do not use any telephone  
in your building.  
Immediately call your gas supplier from a neighbor’s  
OPERATING INSTRUCTIONS  
9.  
Set thermostat to desired setting.  
1.  
STOP! Read the safety information above on this  
label.  
10. If the appliance will not operate, follow the instructions  
“To Turn Off Gas To Appliance” and call your service  
technician or gas supplier.  
2.  
3.  
4.  
Set thermostat to lowest setting.  
Turn off all electric power to the appliance.  
This appliance is equipped with an ignition device which  
automatically lights the burner. Do not try to light the  
burner by hand.  
5.  
6.  
Push in gas control knob slightly and turn clockwise  
to “OFF”.  
Wait five (5) minutes to clear out any gas. If you then  
smell gas,  
above on  
STOP! Follow “B” in the safety information  
this label. If you don’t smell gas, go on to  
the next step.  
7.  
Turn gas control knob counterclockwise  
to “ON”.  
8.  
Turn on all electric power to the appliance.  
FOR YOUR SAFETY READ BEFORE OPERATING  
1.  
2.  
3.  
Set the thermostat to lowest setting.  
Turn off all electric power to appliance if service is to be performed.  
Push in gas control knob slightly and turn clockwise to “OFF”. Do not force.  
26  
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HIGH ALTITUDE INSTALLATIONS  
WARNING  
UNDER NO CIRCUMSTANCES SHOULD THE INPUT EXCEED  
THE RATE SHOWN ON THE HEATER RATING PLATE.  
OVERFIRING COULD RESULT IN DAMAGE OR SOOTING OF  
THE HEATER.  
WARNING  
BTH HEATERS ARE CERTIFIED FOR USE WITHOUT  
MODIFICATION FOR ALTITUDES UP TO 10,000 FEET.  
INSTALLATIONS ABOVE 10,000 FEET MAY REQUIRE  
REPLACEMENT OF THE BURNER ORIFICE. CALL THE  
TECHNICAL INFORMATION CENTER AT (800) 527-1953 FOR  
REQUIREMENTS.  
CATHODIC PROTECTION  
CAUTION  
HYDROGEN GAS CAN BE PRODUCED IN A HOT WATER  
SYSTEM SERVED BY THIS HEATER THAT HAS NOT BEEN Some gas utility companies derate their gas for altitude, making it  
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 a hot water faucet be opened for several  
minutes 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.  
unnecessary to install high altitude orifices. Call the local gas or  
utility company to verify BTU content.  
Due to the input rating reduction at high altitudes, the output rating  
of the appliance is also reduced and should be compensated for in  
the sizing of the equipment for applications.  
MAINTENANCE  
PRECAUTIONS  
GENERAL  
IF THE UNIT IS EXPOSED TO OR EXHIBITS THE FOLLOWING,  
DO NOT OPERATE HEATER UNTIL ALL CORRECTIVE STEPS  
HAVE BEEN MADE BY A QUALIFIED SERVICEMAN.  
KEEP APPLIANCE AREA CLEAR AND FREE FROM  
COMBUSTIBLE MATERIALS, GASOLINE AND OTHER  
FLAMMABLE VAPORSAND LIQUIDS. (SEE WARNING ON PAGE  
6, LOCATING THE HEATER).  
ꢀ. FLOODING TO OR ABOVE THE LEVEL OF THE BURNER OR  
CONTROLS  
ꢁ. EXTERNAL DAMAGE  
3. FIRING WITHOUT WATER  
4. SOOTING  
Water heater maintenance includes periodic tank flushing  
and cleaning, and removal of lime scale. The unit should be  
inspected and adjusted to maintain proper combustion. Refer to  
the following table. A periodic inspection of the venting system  
should be made. Where used, the water circulating pump should  
be oiled.  
NEVER OPERATE THE HEATER WITHOUT FIRST BEING  
CERTAIN IT IS FILLED WITH WATER AND A TEMPERATURE  
AND PRESSURE RELIEF VALVE IS INSTALLED IN THE RELIEF  
VALVE OPENING OF THE HEATER.  
MAINTENANCE SCHEDULE  
SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAILTO  
SHUT OFF, TURN OFF THE MANUAL GAS CONTROL VALVE TO  
THE APPLIANCE.  
Following are the instructions for performing some of the  
recommended maintenance. Unit inspection and adjustment should  
be performed by a competent technician.  
GENERAL INFORMATION  
COMPONENT  
OPERATION  
INTERVAL  
REQUIRED  
POWER BURNER  
Tank  
Sediment  
Removal  
Monthly  
Flushing  
The initial start-up procedure of the unit is provided on page 25.  
The sequence of operation of the unit is provided on page 20.  
Tank  
Lime Scale  
Removal  
Semi  
UN-LIME®  
Delimer  
Annually  
It is important to note that the controller has a reset button on the  
control box, Figure 1. The reset button is a safety device and would  
not normally be used.  
Powered Anode  
System  
Inspect  
Inspect  
Semi  
Annually  
HIGH LIMIT  
The high limit (not adjustable) is factory set to cutout at  
202°F (94°C). The controller will not be reset until water temperature  
drops to below 140°F (61°C).  
Relief Valve  
Semi  
Annually  
Clean Inlet  
Screen and  
Blower Wheel  
TABLE 4.  
Blower  
As Required  
Soft Brush  
GAS SUPPLY SPECIFICATIONS Nat. Gas LP Gas  
Max. Gas Supply Pressure W.C.  
Max. Gas Supply Pressure kPa  
11.00  
2.74  
7.00  
1.74  
5.20  
1.54  
4.00  
1.25  
14.00  
3.49  
11.00  
2.74  
11.0  
2.74  
10.0  
2.49  
Vent System  
Inspect  
Every 3  
Months  
Joints should  
be sealed  
Nominal Gas Supply Pressure W.C.  
Nominal Gas Supply Pressure kPa  
Minimum Gas Supply Pressure W.C.*  
Minimum Gas Supply Pressure kPa*  
Manifold Gas Supply Pressure W.C.  
Manifold Gas Supply Pressure kPa  
(1) If furnished with oiling provision.  
NOTE: UN•LIME is not available in Canada. Please call Customer  
* Minimum pressure for purposes of rate adjustment  
Service at 1-800-265-8520 for approved alternatives.  
ꢁ7  
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Sediment and lime scale removal may be accomplished through  
the cleanout opening furnished on the heater, see Figure 24. The  
heater must be drained, see DRAINING, before removing cleanout  
cover on tank.  
FLUSHING  
1. Turn off the heater electrical disconnect switch.  
2. Open the drain valve and allow water to flow until it runs clean.  
3. Close the drain valve when finished flushing.  
4. Turn on the heater electrical disconnect switch.  
DRAINING  
The heater must be drained if it is to be shut down and exposed to  
freezing temperatures. Maintenance and service procedures may  
also require draining the heater.  
1. Turn off the heater electrical disconnect switch.  
2. Close the cold water inlet valve to heater.  
3. Open a nearby hot water faucet to vent the system.  
4. Open the heater drain valve.  
5. If the heater is being drained for an extended shutdown, it is  
suggested the drain valve be left open during this period.  
FIGURE 24.  
To dissolve and remove the more stubborn mineral deposits,  
A.O. Smith UN•LIME® Professional Delimer should be used. NOTE:  
UN•LIME is not available in Canada. Please call Customer Service  
at 1-800-265-8520 for approved alternatives.  
• Follow FILLING instructions when restoring hot water service.  
SEDIMENT REMOVAL  
Waterborne impurities consist of the particles of soil and sand which  
settle out and form a layer of sediment on the bottom of the tank.  
A.O. Smith UN•LIME® Professional Delimer is an easy to handle  
patented food grade acid formulated specifically for lime scale  
removal from all types of water using equipment. Available in 1  
gallon (3.8L) (part no. 4763) and 5 gallon (19L) (part no. 4813)  
sizes. Hydrochloric base acids are not recommended for use on  
glass-lined tanks.  
For convenience, sediment removal and lime scale removal should  
be performed at the same time.  
LIME SCALE REMOVAL  
A.O. Smith Form No. 4800 Rev. 8, entitled “Why, When and How”,  
describes tank cleaning methods and materials. UN•LIME and  
The amount of calcium carbonate (lime) released from water is the booklet may be obtained through your A.O. Smith dealer or  
in direct proportion to water temperature and usage. The higher distributor.  
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, The cleanout opening is shown in Figure 24. To clean heater through  
heaters and on cooking utensils.  
cleanout opening, proceed as follow:  
Lime accumulation not only reduces the life of the equipment but also 1. Turn off water inlet valve, the heater electrical disconnect switch  
reduces efficiency of the heater and increases fuel consumption. and open drain valve.  
The usage of water softening equipment greatly reduces the 2. Remove outer cover plate from lower side of heater jacket.  
hardness of the water. However, this equipment does not always  
remove all of the hardness (lime). For this reason it is recommended 3. Remove cover from cleanout opening.  
that a regular schedule for deliming be maintained.  
4. Remove lime, scale or sediment using care not to damage the  
The depth of lime buildup should be measured periodically. Heaters  
will have about 3" (7.6cm) of lime buildup when the level of lime has  
glass-lining.  
reached the bottom of the cleanout opening or about 1" (2.5cm) of 5. Inspect cleanout plate gasket: If new gasket is required, replace  
lime buildup if it has reached the drain valve opening. A schedule  
for deliming should be set up, based on the amount of time it would  
take for a 1" (2.5cm) buildup of lime.  
with A. O. Smith part no. 99038.  
6. Install cleanout plate. Be sure to draw plate up tight by tightening  
screws securely.  
Example 1:  
Initial inspection shows 1/2" (1.3cm) of lime accumulation. 7. Close drain valve, open water inlet line and turn on the power  
Therefore, the heater can be delimed once a year.  
burner electrical disconnect switch.  
Example 2 :  
8. Check for water leakage.  
Initial inspection shows 2" (5cm) of lime accumulation. Therefore,  
the heater should be delimed every 3 months.  
9. Replace outer jacket cover plate.  
ꢁ8  
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If the temperature and pressure relief valve on the heater discharges  
periodically or continuously, it may be due to thermal expansion of  
water in a closed water supply system, or, it may be due to a faulty  
relief valve.  
POWERED ANODE SYSTEM  
To insure a long, trouble-free operating life, BTH 300, 400 and 500  
are factory equipped with a powered anode system. The anodes  
are of a permanent design and do not need replacing unless  
damaged.  
Thermal expansion is the normal response of water when it is heated.  
In a closed system, thermal expansion will cause the system pressure  
to build until the relief valve actuation pressure is equaled. Then,  
the relief valve will open, allowing some water to escape, slightly  
lowering the pressure.  
DRAIN VALVE AND ACCESS PANELS  
The heaters are equipped with a 3/4" drain valve.  
Contact your water supplier or local plumbing inspector on how to  
control this situation.  
An access panel covers the cleanout opening in the tank which is  
sealed by a gasket and cover, see Figure 24.  
Two common corrections are listed in the Checklist and Service  
Information which appears later in this manual.  
RELIEF VALVE  
At least twice a year, the temperature and pressure relief valve should  
be checked to ensure that it is in operating condition. To check the  
relief valve, lift the lever at the end of the valve several times. The  
valve should seat properly and operate freely.  
ABOVEALL,DONOTPLUGTHETEMPERATUREANDPRESSURE  
RELIEF VALVE. THIS IS NOT A SOLUTION AND CAN CREATE A  
HAZARDOUS SITUATION.  
If water does not flow, remove and inspect for obstructions or  
corrosion. Replace with a new valve of the recommended size as  
necessary. Inspection of the valve should be performed at least every  
three years. Do not attempt to repair the valve, as this could result  
in improper operation and a tank explosion. In areas with poor water  
conditions, it may be necessary to inspect the T&P valve more often  
than every three years.  
VENT SYSTEM  
Examine the vent system every 3 months. Points of inspection are  
as follows:  
1. Check for obstructions and/or deterioration of vent piping and  
vent hood. Replace immediately where needed.  
2. Vent pipe and vent hood screen should be cleaned of foreign  
material and soot. The screen is located inside the vent hood  
outlet and is accessible from the outside of the hood. Do not  
reach inside the vent hood when the heater is in operation.  
CAUTION  
BEFORE MANUALLY OPERATING THE VALVE, MAKE SURE  
THAT A DRAIN LINE HAS BEEN ATTACHED TO THE VALVE  
TO DIRECT THE DISCHARGE TO AN OPEN DRAIN. FAILURE  
TO TAKE THIS PRECAUTION COULD MEAN CONTACT WITH  
EXTREMELY HOT WATER PASSING OUT THE VALVE DURING  
THIS CHECKING OPERATION.  
3. Check all vent system connections for leakage and reseal as  
required using Hi Temp Silicone sealer or equivalent.  
ꢁ9  
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INSTALLATION DIAGRAMS  
ONE TEMPERATURE - ONE HEATER VERTICAL STORAGE TANK FORCED CIRCULATION  
WITH OR WITHOUT BUILDING RECIRCULATION  
CAUTION: IF BUILDING  
COLD WATER SUPPLY HAS  
A BACK-FLOW PREVENTER,  
CHECK VALVE OR WATER  
METER WITH CHECK VALVE  
PROVISIONS FOR THERMAL  
EXPANSION OF WATER IN THE  
HOT WATER SYSTEM MUST  
BE PROVIDED  
NOTE: CONNECT RETURN  
LINE FROM HOT WATER  
CIRCULATING LOOP (IF USED)  
TO COLD WATER INLET LINE.  
* PIPE TO OPEN DRAIN  
INSTALL IN ACCORDANCE  
WITH LOCAL CODES  
ONE TEMPERATURE - ONE HEATER HORIZONTAL STORAGE TANK  
FORCED CIRCULATION WITH OR WITHOUT BUILDING RECIRCULATION  
DANGER  
TEMPERATURE SETTING SHOULD NOT EXCEED  
SAFE TEMPERATURE AT FIXTURES. SEE WATER  
TEMPERATURE CONTROL WARNING ON PAGE  
3. IF HIGHER PREHEAT TEMPERATURES ARE  
NECESSARY TO OBTAIN ADEQUATE BOOSTER  
OUTPUT, ADD AN ANTI-SCALD VALVE FOR HOT  
WATER SUPPLIED TO FIXTURES.  
*PIPE TO OPEN DRAIN  
INSTALL IN ACCORDANCE  
WITH LOCAL CODES  
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TWO TEMPERATURE - ONE HEATER HIGH TEMPERATURE  
WITH OR WITHOUT BUILDING RECIRCULATION  
*PIPE RELIEF VALVE TO OPEN DRAIN.  
DANGER  
N O T E : I F T E M P E R E D WAT E R I S  
RECIRCULATED, RETURN LINE SHOULD  
BE CONNECTED AT POINT “A”.  
TEMPERATURE SETTING SHOULD NOT EXCEED  
SAFE TEMPERATURE AT FIXTURES. SEE WATER  
TEMPERATURE CONTROL WARNING ON PAGE 3. IF  
HIGHER PREHEAT TEMPERATURES ARE NECESSARY  
TO OBTAIN ADEQUATE BOOSTER OUTPUT, ADD AN  
ANTI-SCALD VALVE FOR HOT WATER SUPPLIED TO  
FIXTURES.  
INSTALL IN ACCORDANCE WITH LOCAL  
CODES.  
CAUTION: IF BUILDING COLD WATER SUPPLY HAS A  
BACK-FLOW PREVENTER, CHECK VALVE OR WATER  
METER WITH CHECK VALVE PROVISIONS FOR  
THERMAL EXPANSION OF WATER IN THE HOT WATER  
SYSTEM MUST BE PROVIDED.  
3ꢀ  
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TWO TEMPERATURE - TWO HEATERS HIGH TEMPERATURE  
WITH OR WITHOUT BUILDING RECIRCULATION  
MUST BE IDENTICAL HEATERS  
FOR MULTIPLE HEATER INSTALLATION SEE MANIFOLD KIT  
SPECIFICATIONS, PAGE 35.  
DANGER  
TEMPERATURE SETTING SHOULD NOT EXCEED SAFE  
TEMPERATURE AT FIXTURES. SEE WATER TEMPERATURE  
CONTROL WARNING ON PAGE 3. IF HIGHER PREHEAT  
TEMPERATURES ARE NECESSARY TO OBTAIN ADEQUATE  
BOOSTER OUTPUT, ADD AN ANTI-SCALD VALVE FOR HOT  
WATER SUPPLIED TO FIXTURES.  
CAUTION: IF BUILDING COLD WATER SUPPLY HAS A BACK-  
FLOW PREVENTER, CHECK VALVE OR WATER METER WITH  
CHECK VALVE PROVISIONS FOR THERMAL EXPANSION OF  
WATER IN THE HOT WATER SYSTEM MUST BE PROVIDED.  
3ꢁ  
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TWO TEMPERATURE - TWO HEATERS (ONE PRE-HEATER/ONE BOOSTER HEATER)  
WITH OR WITHOUT BUILDING RECIRCULATION  
* PIPE RELIEF VALVE TO OPEN DRAIN  
DANGER  
TEMPERATURE SETTING SHOULD NOT EXCEED SAFE TEMPERATURE  
** 140°F (60°C)TO 150°F (66°C) SHOULD BE MAXIMUM WATER  
TEMPERATURE MAINTAINED IN THE PRE-HEATERS.  
AT FIXTURES. SEE WATER TEMPERATURE CONTROL WARNING ON  
PAGE 3. IF HIGHER PREHEAT TEMPERATURES ARE NECESSARY TO  
OBTAIN ADEQUATE BOOSTER OUTPUT, ADD AN ANTI-SCALD VALVE  
FOR HOT WATER SUPPLIED TO FIXTURES  
120°F (49°C) SHOULD BE THE MINIMUM TEMPERATURE OF  
WATER IN THE PRE-HEATERS.  
CONNECT CIRCULATING LINE FROM FIXTURES, IF USED,  
TO COLD WATER SUPPLY LINE OF PRE-HEATER.  
CONNECT CIRCULATING LINE OF 180°F (82°C) OR BOOSTED  
WATER, IF USED, TO INLET WATER LINE TO BOOSTER.  
INSTALL IN ACCORDANCE WITH LOCAL CODES.  
33  
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TWO TEMPERATURE - ONE HEATER HIGH TEMPERATURE  
WITH RECIRCULATION OF SANITIZING LOOP  
NOTE 1: TOGGLE SWITCH CONTROLS 180°F (82°C) WATER  
DANGER  
CIRCULATION. INSTALL ON OR CLOSE TO DISHWASHER.  
TOGGLE SWITCH MUST BE CLOSED (ON) DURING THE RINSE  
OPERATION AND OPEN (OFF) WHEN DISHWASHER IS NOT  
OPERATING OR WHEN ON LONG STANDBY.  
TEMPERATURE SETTING SHOULD NOT EXCEED SAFE  
TEMPERATURE AT FIXTURES. SEE WATER TEMPERATURE  
CONTROL WARNING ON PAGE 3. IF HIGHER PREHEAT  
TEMPERATURES ARE NECESSARY TO OBTAIN ADEQUATE  
BOOSTER OUTPUT, ADD AN ANTI-SCALD VALVE FOR HOT  
WATER SUPPLIED TO FIXTURES.  
NOTE 2: INSTALL LINE TEMPERATURE CONTROL IN AN  
UNINSULATED TEE BEYOND THE DISHWASHER TAKEOFF  
IN THE SANITIZING LOOP. CONTROL SHOULD BE SET AT  
185°F (85°C).  
CAUTION: IF BUILDING COLD WATER SUPPLY HAS A BACK-  
FLOW PREVENTER, CHECK VALVE OR WATER METER WITH  
CHECK VALVE PROVISIONS FOR THERMAL EXPANSION OF  
WATER IN THE HOT WATER SYSTEM MUST BE PROVIDED.  
NOTE 3: ADJUST PLUG COCK SO THE SANITIZING LOOP  
FLOW RATE DOES NOT CAUSE UNNECESSARY TURBULENCE  
IN THE TANK.  
*PIPE RELIEF VALVE TO OPEN DRAIN  
NOTE 4: IF TEMPERED WATER IS RECIRCULATED, RETURN  
LINE SHOULD BE CONNECTED AT POINT A.  
INSTALL IN ACCORDANCE WITH LOCAL CODES  
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MULTIPLE UNIT INSTALLATIONS  
Proper installation of multiple water heaters assures water flow balance of all units. Without this balance, the full water heating and storage  
potential of the system cannot be achieved. Plus, the units with the higher water flow may have a shortened life.  
Dimensions shown are for minimum space occupied by the water heaters assemblies.  
Space for the venting system and unit servicing must be added.  
Manifold Kits for multiple unit installations are not available from the manufacturer.  
35  
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10. Condensate hose may be blocked where it connects to the  
exhaust elbow.  
CHECKLIST AND SERVICE INFORMATION  
IMPORTANT  
Verify the condensate drains from the unit without restriction.  
The installer may be able to observe and correct certain problems  
which might arise when the unit is put into operation or when it is  
re-fired after a prolonged shutdown. HOWEVER, it is recommended  
that only qualified servicemen, using appropriate test equipment, be  
allowed to service the heater.  
WATER IS TOO HOT  
1. Refer to WATER TEMPERATURE CONTROL.  
BE SURE TO TURN OFF THE ELECTRICITY WHENEVER  
POSSIBLE OR APPROPRIATE WHILE CHECKING EQUIPMENT.  
WATER HEATER MAKES SOUNDS  
1. Sediment or lime scale accumulations cause rumbling and  
pounding noises when the heater is operating.  
WARNING  
FAILURE TO FOLLOW THESE INSTRUCTIONS CAN RESULT IN  
SERIOUS PERSONAL INJURY OR DEATH.  
The sounds are normal, however, the tank bottom should be  
cleaned. Refer to MAINTENANCE for details.  
CAUTION:  
LABEL ALL WIRES PRIOR TO DISCONNECTION WHEN  
SERVICING CONTROLS. WIRING ERRORS CAN CAUSE  
IMPROPER AND DANGEROUS OPERATION.  
2. Some of the electrical components of the water heater make  
sounds which are normal.  
Contacts click or snap as the heater starts and stops.  
Transformers often hum.  
VERIFY PROPER OPERATION AFTER SERVICING.  
BURNER OPERATIONAL PROBLEMS  
WATER LEAKAGE IS SUSPECTED  
ꢀ. Refer to TROUBLESHOOTING.  
1. Check to see if the water heater drain valve is tightly closed.  
Also check the cleanout opening for leakage.  
NOT ENOUGH OR NO HOT WATER  
2. The apparent leakage may be condensation which forms on cool  
surfaces of the heater and piping.  
1. Be certain the electrical disconnect switch serving the water  
heater is in the ON position.  
3. If the outlet of the relief valve is leaking it may represent:  
2. Check the fuses.  
Excessive water pressure.  
Excessive water temperature.  
Faulty relief valve.  
The electrical disconnect switch usually contains fuses.  
3. The capacity of the heater may have been exceeded by a large  
demand for hot water.  
Large demands require a recovery period to restore water  
temperature.  
Excessive water pressure is the most common cause of relief valve  
leakage. It is often caused by a “closed system”. If a check valve is  
in the inlet system it will not permit the expanded hot water volume  
to equalize pressure with the main. The relief valve must release this  
water or the water heater or plumbing system will be damaged. Refer  
to MAINTENANCE-RELIEF VALVE section in this manual.  
4. Colder incoming water temperature will lengthen the time  
required to heat water to the desired temperature.  
If the heater was installed when incoming water  
temperature was warm, colder water creates the effect  
of less hot water.  
When such a condition is encountered, local codes or inspection  
agency should be consulted to determine which system is acceptable  
in your area. See CLOSED SYSTEM section in this manual.  
5. Look for hot water wastage and leaking or open hot water  
faucets.  
TROUBLESHOOTING  
6. Sediment or lime scale may be affecting water heater operation.  
Refer to MAINTENANCE for details.  
1. Verify that the allowable vent length has not been exceeded and  
that the blower inlet screen has been removed if direct venting.  
7. The heater’s temperature high limit sensor has activated. Press  
the reset button on the thermostat.  
2. Verify the gas supply volume and pressure per table 3 and 4.  
8. Burner may not be firing at proper rate.  
3. Verify that the condensation, which WILLbe present in the heater  
and exhaust vent, will drain.  
Check gas pressure. Adjust to obtain required manifold  
pressure.  
4. Check supply wire polarity - hot to hot and neutral to neutral and  
no "stray" current in neutral.  
9. Burner fan wheel may be dirty.  
Clean fan wheel with a stiff brush.  
5. Heater is properly grounded.  
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this tubing is damaged it must be replaced. If these steps do not  
eliminate the problem, replace the pressure switches.  
Checking these four (4) items first will often result in a timely solution  
to the service call.  
WARNING  
5. Check to see if there is resistance across the igniter terminal  
with an OHM meter. If there is no continuity, the igniter is  
broken and should be replaced.  
JUMPING OUT COMPONENTS AND/OR CIRCUITS DURING  
TROUBLESHOOTING CAN CAUSE SERIOUS PROBLEMS WITH  
THE UNIT’S OPERATING SEQUENCE AND IGNITION SAFETY.  
IF YOU DO NOT HAVE THE PROPER TEST EQUIPMENT, I.E. A  
VOLT-OHM METERANDAMICROMETER, DO NOTATTEMPTTO  
TROUBLESHOOT OR REPAIR A.O. SMITH EQUIPMENT.  
If the igniter appears to function properly, then verify that the  
inlet pressure is 11.0" Natural Gas (2.74 kPa). The gas valve  
supplied on this appliance is not designed to open against a  
higher pressure. At this time also check that the inlet pressure  
is not lower than the minimal gas supply pressure, as shown  
in Table 4: that is, for Natural Gas, 5.2" (1.29 kPa) W.C. If  
the inlet pressure is not within these limits then adjust the  
supply pressure accordingly.  
ALTERING THE CONTROLLER AND/OR CONTROLLER WIRING  
IN ANY WAY COULD RESULT IN INTERNAL DAMAGE TO THE  
MODULE CIRCUITS, POSSIBLY ALTERING THE IGNITION  
SEQUENCE ALLOWING GAS VALVES TO OPEN BEFORE THE  
HOT SURFACE IGNITER IS UP TO IGNITION TEMPERATURE.  
If the inlet pressure falls within the allowable limits, then verify  
that the manifold pressure, when the gas is fully open, with  
the heater running, is as called out in Table 4: that is, for  
Natural Gas, 4.0" (0.996 kPa) W.C. If the manifold pressure  
is not correct then adjust accordingly. See ADJUSTMENT  
PROCEDURE in OPERATING INSTRUCTIONS for the  
manifold pressure adjustment procedure.  
NOTE:ANY BYPASS ORALTERATION OF THE UNITS SAFETIES  
WILL RESULT IN VOIDING THE APPLIANCE WARRANTY.  
Before performing any troubleshooting familiarize yourself with the  
particular appliance.  
Refer to the SEQUENCE OF OPERATION and the connection  
diagram before continuing.  
6. If the inlet and manifold pressures are within the limits  
specified in step 5, then reset the appliance. Verify 24V AC  
at the gas valve during the three (3) second ignition trial, after  
the igniter reaches operating temperature. If 24V AC at the  
gas valve is not seen during this period, the controller must  
be replaced.  
Make sure the appliance is connected to a 120V AC power supply,  
manual gas valve is in the ON position, and all electrical connections  
are secure before continuing to troubleshoot this appliance.  
CAUTION  
THEWATERHEATERISPOLARITYSENSITIVE. BEFOREAPPLYING  
ELECTRICITYTOTHISHEATERBECERTAINTHATSUPPLYNEUTRAL  
WIRE TO GROUND CHECK INDICATES ZERO VOLTAGE.  
If there is 24V AC at the gas valve during the four second  
ignition trial and the manifold pressure does not increase  
above 0" W.C. then verify that the manual gas control valve  
is in the “ON” position. If the valve is in the “ON” position and  
the previous voltage and gas pressure conditions are met,  
then the gas valve is defective and must be replaced.  
MOTOR WILL NOT RUN  
1. Confirm 120V AC. Also, to verify correct polarity, check for 120 V  
AC between hot supply and ground. If there is no voltage, check  
for a loose connection.  
MOTOR RUNS, BURNER LIGHTS MOMENTARILY,  
THEN LOCKS OUT  
2. For BTH 400 and 500 a VFD (Variable Frequency Drive) is  
used. "rdy" (stands for ready) will be shown on display in  
standby heating mode. "155" (155 output Hz) shall be shown  
on VFD display during heater running for BTH 400. "196" will be  
displayed on VFD during BTH 500 running. Any other display  
on the VFD indicates a faulty VFD or wrong speed reference,  
call A.O. Smith Tech Center for assistance.  
1. Reset the appliance two more times to ensure that all of the  
air has been purged from the gas line.  
2. If the burner lights momentarily but does not sustain  
ignition, verify that the inlet pressure is not greater than  
11.0" (2.74 kPa) W.C. or lower than the minimal gas  
supply pressure, as shown in Table 4: that is, for Natural  
Gas, 5.2" (1.29 kPa) W.C. pressure. Also, the manifold  
pressure should rise during the three (3) second trial for  
ignition to the manifold pressure value for the individual  
unit listed in Table 4: that is, for Natural Gas, 4.0" (0.996  
kPa) W.C. If the manifold pressure is not correct then  
adjust accordingly. See ADJUSTMENT PROCEDURE in  
OPERATING INSTRUCTIONS section for the manifold  
pressure adjustment procedure.  
MOTOR RUNS, PREPURGE TIME ELAPSES BUT  
MAIN FLAME NOT ESTABLISHED  
1. Check to see if main manual gas valve is open.  
2. Check for a loose connection at the transformer, or a defective  
transformer.  
3. Check for a loose connection at the gas valve.  
3. Check for the reversed polarity in the supply wiring. This  
controller is polarity sensitive. If the hot and neutral supply  
wires are reversed, the controller will not sense flame. Reverse  
the supply wires and try to fire the unit.  
4. Check for open pressure switches or open reset button. Check for  
blockage in the intake and exhaust venting or at the vent hoods.  
If no blockage is found, check vinyl tubing for cuts or crimps. If  
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NOTE: Always turn off and disconnect main supply wiring before  
servicing the unit.  
NOISY BURNER OPERATION  
The exhaust of this unit produces some noise during ignition period.  
When combustion is too lean or too rich, start up noise will get worse.  
Check for flue gas COreading, adjust gas valve manifold pressure  
if required to bring the flue gas COto 9–9.5% level for natural gas,  
10.75–11.25% for LP. This noise may be objectionable if the exhaust  
terminal is located too close to the opening of an occupied space.  
The noise may also be objectionable if the exhaust is located in the  
confined space between two buildings such as an alley or walkway.  
Since everyone's perception and tolerance for background noise  
varies, there is no standard recommendation. The best option  
when the noise is a concern is to fine-tune the air/gas ratio of the  
combustion system or locate the exhaust as far away from any  
occupied spaces as practical.  
4. Check connecting wire to the flame sensor. Verify that the flame  
sensor has not been damaged in any way.  
5. Verify that the air supply is adequate. The air inlet screen or blower  
wheel may be restricted. Also, check the installation for proper  
ventilation. See AIR REQUIREMENTS.  
6. Check the venting system for the correct sizing, excess or  
insufficient. See VENTING.  
7. Check for a maximum inlet pressure of 11" Natural Gas  
(2.74 kPa) W.C. and the manifold pressure as listed in Table 4:  
that is, for Natural Gas, 4.0" (0.996 kPa) W.C. Please note that  
the manifold pressure listed is the maximum value for the manifold  
pressure. Do not set the manifold pressure higher than the value  
shown for your heater in Table 4. Overfiring the heater will result  
in rough ignition and/or noisy operation.  
GAS FAILS TO SHUT OFF  
Check for defective gas valve or thermostat. If operation is  
incorrect, replace.  
REPLACEMENT PARTS  
8. Confirm that the air inlet screen (see Figures 7 & 8) is free of  
obstructions.  
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.  
When ordering parts be sure to state the quantity, part number  
and description of the items including the complete model and  
serial number as it appears on the product. Refer to the parts list  
for more information.  
CAUTION  
Do not reach into the burner housing or combustion chamber if the  
heater is still hot. Allow the heater to cool and always use gloves as  
the combustion chamber and the burner sleeve and housing can  
become very hot after operation. Overfiring is a dangerous condition  
that must be corrected immediately.  
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Model BTH Limited Warranty  
A. O. Smith Corporation, the warrantor, extends the following LIMITED WARRANTY to the owner of this water heater.  
ꢀ. 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 replacement tank less burner and controls or a complete new  
A.O. Smith water heater of equivalent size and current model at the warrantor's option. 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.  
ꢁ. 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 A.G.A. and approved  
by the American Society of Mechanical Engineers, must have been installed.  
a. This warranty shall apply only when the heater is:  
(1) owned by the original purchaser;  
(2) used at temperatures not exceeding the maximum setting of its thermostat;  
(3) used at water pressure not exceeding the working pressure shown on the heater;  
(4) used when operated free of the damaging effects of uncontrolled water hammer;  
(5) used when filled with potable water, free to circulate at all times;  
(6) used in a non-corrosive and non-contaminated atmosphere;  
(7) used with factory approved anode(s) installed;  
(8) in its original installation location;  
(9) in the United States, its territories or possessions, and Canada;  
(10) sized in accordance with proper sizing techniques for commercial water heaters;  
(11) bearing a rating plate which has not been altered, defaced or removed except as required by the warrantor;  
(12) fired at the factory rated input using the fuel stated on the rating plate;  
(13) maintained in accordance with the instructions printed in the manual included with the heater.  
b. Any accident to the water heater, any misuse, abuse (including freezing) or alteration of it, any operation of it 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.  
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 limitations 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 water 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 Corporation  
500 Tennessee Waltz Parkway  
Ashland City, TN 37015  
Telephone: 1-(800)-323-2636  
A. O. Smith Enterprises Ltd.  
P. O. Box, 310 - 768 Erie Street  
Stratford (Ontario) N5A 6T3  
Telephone: 1-(800) 265-8520  
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 MERCHANTABILITY  
OF THE HEATER OR THE INSTALLATION, OPERATION, REPAIR OR REPLACEMENT OF THE WATER 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 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.  
Date Installed________________________Model No.____________________________________________Serial No._________________________________________  
Dealer’s Name _____________________________________________________________________Phone No.________________________________________________  
Dealer’s Address__________________________________________________City and State________________________________________Zip Code________________  
FILL IN WARRANTY AND KEEP FOR FUTURE REFERENCE.  
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