A.O. Smith BTH 400A User Manual

CYCLONE XHE®

Series 976, 977

Series 976, 977

Model BTH 300A AND 400A

COMME RCIAL GAS W ATER HEATER

GAS-FIRED POWER BURNER

FOR DOMESTIC HOT W ATER

• INST ALLATION • OPERATION • SER VICE • MAINTENANCE • LIMITED WARRANTY

W ARNING: 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 T O 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
INFORMA TION RELATIVE TO YOUR SAFETY. PLEASE
READ THOROUGHLY BEFORE INST ALLING AND USING
THIS APPLIANCE.

PLACE THESE INSTRUCTIONS ADJACENT TO HEATER AND NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.

PRINTED IN U.S.A. 0706 PART NO. 197373-001

1

www.hotwater.com

ROUGH-IN-DIMENSIONS

GAS V AL VE PIPING

BTH-300 1 1/4" NPT
BTH-400 1 1/4" NPT

T ABLE 1 RECOVER Y CAPACITIES.

U.S. Gallons/Hr and Litres/Hr at TEMPERATURE RISE INDICATED

MODEL GAS BTUH KW Capacity C° 11C° 17C° 22C° 28C° 33C° 39C° 44C° 50C° 56C° 61C° 67C° 72C° 78C°

BTH-300

BTH-300

BTH-400

BTH-400 PROPANE

Recovery capacities are based on heater performance at 96% thermal efficiency.

TYPE OF INPUT Approx. F° 20F° 30F° 40F° 50F° 60F° 70F° 80F° 90F° 100F° 110° 120F° 130F° 140F°

NATURAL

PROPANE

NATURAL

300,000 130 US Gals. GPH 1746 1164 873 699 582 499 436 388 349 318 291 269 250

88 492 Litres LPH 6610 4406 3304 2644 2203 1888 1652 1469 1322 1201 1 102 1017 945

300,000 130 US Gals. GPH 1746 1164 873 699 582 499 436 388 349 318 291 269 250

88 492 Litres LPH 6610 4406 3304 2644 2203 1888 1652 1469 1322 1201 1 102 1017 945

399,900 130 US Gals. GPH 2328 1552 1164 931 776 665 582 517 466 423 388 359 332

11 7 492 Litres LPH 8813 5875 4406 3525 2938 2518 2203 1958 1763 1602 1469 1356 1259

399,900 130 US Gals. GPH 2328 1552 1164 931 776 665 582 517 466 423 388 359 332

11 7 492 Litres LPH 8813 5875 4406 3525 2938 2518 2203 1958 1763 1602 1469 1356 1259

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.

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.

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.

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.

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 S tandards Association,
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.

2

TABLE OF CONTENTS

PAGE

ROUGH-IN DIMENSIONS ............................................................... 2

FOREWORD .................................................................................... 2

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

VENTING.......................................................................................... 7-10

Vent Pipe Termination .................................................................. 10

Direct Venting............................................................................... 10

Direct Vent Terminal Installation .................................................. 10-11

Installation Sequence ................................................................... 11

Vertical Vent Terminal Installation ................................................ 11

Installation Sequence ................................................................... 11-12

Installation of Vent System .......................................................... 12

Vent Pipe Preparation .................................................................. 13

CONTROLS AND SWITCHES ......................................................... 13

Blower Prover Switch ................................................................... 13

Blocked Outlet Prover Switch ...................................................... 13

Blocked Inlet Prover Switch ......................................................... 13

Low Gas Pressure Switch ............................................................ 13

On/Off Switch ............................................................................... 13

Hot Surface Igniter ....................................................................... 14

GAS PIPING..................................................................................... 14

Connection of Gas Pipe ............................................................... 14-15

Purging ......................................................................................... 15

Gas Meter Size - City Gases Only............................................... 15

Gas Valves ................................................................................... 15

SYSTEM CONNECTIONS ............................................................... 15

Thermometers.............................................................................. 15

Relief Valve .................................................................................. 15

Water Line Connections............................................................... 15

Closed System ................................................................................ 15

PAGE

Water (Potable) Heating & Space Heating ..................................... 15-16

Heater Wiring .................................................................................. 16-17

OPERATION........................................................................................ 18

Sequence of Operation ................................................................... 18

Self Diagnostic Controller ............................................................... 18

Gas Value LEDs Flashing ............................................................... 18

Error Codes ..................................................................................... 19

Fault Conditions .............................................................................. 19

No Incoming Line Voltage............................................................... 19

No Low Voltage ............................................................................... 19

Temperature Probe Fault ................................................................19-20

E.C.O. Switch Open........................................................................ 20

Control Bad ..................................................................................... 20

Combustion Air Blockage ................................................................ 20

PRIOR TO START-UP REQUIRED ABILITY ...................................... 21

OPERATING INSTRUCTIONS ........................................................... 21

Adjustment Procedure (Initial Start-Up) .......................................... 21-22

Lighting Instructions ........................................................................ 22

Cathodic Protection......................................................................... 23

Precautions ..................................................................................... 23

GENERAL INFORMATION ................................................................. 23

Power Burner .................................................................................. 23

High Limit ........................................................................................ 23

High Altitude Installations ................................................................ 23

MAINTENANCE .................................................................................. 23

General............................................................................................ 23

Maintenance Schedule ................................................................... 24

Flushing........................................................................................... 24

Draining ........................................................................................... 24

Sediment Removal.......................................................................... 24

Lime Scale Removal .......................................................................24-25

Powered Anode System .................................................................. 25

Powered Anode Operation .............................................................. 25

Drain Valve and Access Panels ...................................................... 25

Relief Valve ..................................................................................... 25

Vent System.................................................................................... 25

INSTALLATION DIAGRAMS ...............................................................26-30

Manifold Kits.................................................................................... 31

CHECKLIST AND SERVICE INFORMA TION..................................... 32

TROUBLESHOOTING ........................................................................32-34

REPLACEMENT PARTS ..................................................................... 34

LIMITED WARRANTY ......................................................................... 35

FEATURES

IMPORTANT

IT IS REQUIRED THAT A QUALIFIED SERVICE TECHNICIAN
PERFORM THE INITIAL FIRING OF THE HEA TER. A T 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.

A CHECKLIST AND SER VICE 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.

WA TER TEMPERATURE CONTROL

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 INJUR Y AND/OR DEA TH.
THE TEMPERATURE A T WHICH INJURY OCCURS V ARIES 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 WA TER TAP , OR TO
DRAW THEIR OWN BATH WATER. NEVER LEAVE A CHILD OR
DISABLED PERSON UNATTENDED IN A BATHTUB OR
SHOWER.

THE WATER HEATER SHOULD BE LOCATED IN AN AREA
WHERE THE GENERAL PUBLIC DOES NOT HAVE ACCESS TO
SET TEMPERA TURES.

The water temperature is controlled using the Temperature Control
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

“AT A GLANCE” BTH 300/400

QUICK INSTALLATION TIPS

Horizontal Sidewall Venting Vertical Rooftop Venting

4

The temperature may be adjusted from 80°F/27°C to 180°F/82°C.
The thermostat was adjusted to 120°F/49°C before the heater was
shipped from the factory. It is recommended that lower water
temperatures be used to avoid the risk of scalding. It is further
recommended, in all cases, that the water temperature be set for
the lowest temperature which satisfies your hot water needs. This
will also provide the most energy efficient operation of the water
heater and minimize scale formation.

WA TER TEMPERA TURE SETPOINT ADJUSTMENT

PROCEDURE

CAUTION

THE TEMPERATURE OF THE WA TER AT THE TANK OUTLET MAY
NOT CORRESPOND TO THE TEMPERATURE SETPOINT
PROGRAMMED IN THE CONTROLLER. THE USER CAN EASIL Y
CHANGE THE TEMPERATURE SETPOINT AT ANY TIME BY
USING THE FOLLOWING PROCEDURE. IN ALL CASES, INPUT
POWER MUST BE APPLIED TO THE CONTROLLER TO
PERFORM ANY PROGRAMMING OPERATIONS.

Valves for reducing point-of-use temperature by mixing cold and
hot water are available (see Figure 2). Also available are
inexpensive devices that attach to faucets to limit hot water
temperatures. Contact a licensed plumber or the local plumbing
authority.

To change or view the current programmed temperature setpoint
value, utilize the pushbutton on the Display Board. Momentarily
pressing the button will briefly illustrate the existing setpoint value.
If the button is held down for more than one second, the
programming mode is automatically entered and the setpoint value
will begin incrementing or decrementing by one degree per second.
The control will alternate between the incrementing or
decrementing mode each time the button is pressed. When the
desired setpoint value is reached, simply release the button and
the controller will automatically retain this value in temporary
memory. After one complete heat cycle, the new setpoint is
transferred to permanent memory.

Note: If power is interrupted prior to completing one heat cycle, the
new setpoint will not be transferred to permanent memory. Therefore,
it is a good practice to recheck the setpoint value at the end of a
heat cycle after a new value has been entered.

If the button is held down long enough, the setpoint will reach 70°F
(the minimum value) and stop. At this point, if the desired setpoint
has not been obtained, release the button and depress it again.
The setpoint value will now restart at 70°F and once again increase
in value for as long as the button is pressed.

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 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.

Temperature Time to Produce 2nd & 3rd

Setting Degree Burns on Adult Skin
180°F / 82°C Nearly instantaneous
170°F / 77°C Nearly instantaneous
160°F / 71°C About 1/2 second
150°F / 66°C About 1-1/2 seconds
140°F / 60°C Less than 5 seconds
130°F / 54°C About 30 seconds
120°F / 49°C More than 5 minutes

FIGURE 1.

FIGURE 2.

HIGH LIMIT SWITCH (E.C.O.)

The top immersion well of the dual bulb controller also contains the
high limit (energy cutoff) sensor. The high limit switch interrupt s the
main burner gas flow should the water temperature reach
approximately 202°F/94°C.

Should the high limit switch activate, it must be manually reset by
depressing the T emperature Adjustment Button/Reset Button on the
display board. The water temperature must drop below 160°F/71°C
before the controller can be reset.

Continued manual resetting of high limit control, preceded by higher
than usual water temperature is evidence of high limit switch
operation. 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.

DISHW ASHING 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.

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.)

5

CIRCULA TING PUMP

A circulating pump is used when a system requires a circulating loop
or there is a storage t ank used in conjunction with the heater. Refer to
the piping diagrams a t 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.

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.

INSTALLATION INSTRUCTIONS

REQUIRED ABILITY

INSTALLATION OR SERVICE OF THIS WATER HEATER
REQUIRES ABILITY EQUIVALENT TO THAT OF A LICENSED
TRADESMAN IN THE FIELD INVOL VED. PLUMBING , AIR SUPPL Y,
VENTING, GAS SUPPLY AND ELECTRICAL WORK ARE
REQUIRED.

THE HEATER SHALL BE LOCATED OR PROTECTED SO IT IS
NOT SUBJECT TO PHYSICAL DAMAGE BY A MOVING VEHICLE.

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.

WARNING

FLAMMABLE ITEMS, PRESSURIZED CONTAINERS OR ANY
OTHER POTENTIAL FIRE HAZARDOUS ARTICLES MUST
NEVER BE PLACED ON OR ADJACENT TO THE HEA TER. OPEN
CONTAINERS OF FLAMMABLE MATERIAL SHOULD NOT BE
STORED OR USED IN THE SAME ROOM WITH THE HEATER.

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.

INSULA TION 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.

WARNING

Should you choose to apply an insulation blanket to this heater,
you should follow these instructions. Failure to follow these
instructions can result in fire, asphyxiation, serious personal injury
or death.

• Do not 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 from A.O. Smith for placement on the blanket
directly over the existing labels.

THE HEATER MUST NOT BE LOCATED IN AN AREA WHERE IT
WILL BE SUBJECT TO FREEZING.

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

THIS WA TER HEA TER IS A CONDENSING UNIT AND 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 BUILD­UP WILL BLOCK THE EXHAUST OUTLET, WHICH WILL CAUSE
IMPROPER OPERATION.

LOCA TING THE HEA TER

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 VEHICLES ARE STORED,
OPERATED OR REPAIRED. FLAMMABLE VAPORS ARE HEA VY
AND TRA VEL ALONG THE FLOOR AND MA Y BE IGNITED BY THE
HEA TER’S IGNITER OR MAIN BURNER FLAMES CAUSING FIRE
OR EXPLOSION. SOME LOCAL CODES PERMIT OPERA TION OF
GAS APPLIANCES IF INST ALLED 18 INCHES (46 cm) OR MORE
ABOVE THE FLOOR. THIS MAY REDUCE THE RISK IF
LOCATION IN SUCH AN AREA CANNOT BE AVOIDED.

FIG URE 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 PAR T OF THE CONTROL SYSTEM AND ANY GAS CONTROL
WHICH HAS BEEN UNDER WATER.

6

CLEARANCES

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.

SERIOUS DAMAGE TO THE HEATER AND RISK OF FIRE OR
EXPLOSION. IT CAN ALSO CREA TE A RISK OF ASPHYXIATION.

UNCONFINED SP ACE

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).

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.

Always disconnect electrical power before servicing the unit

*ILLUSTRATION OF MINIMUM COMBUSTIBLE CLEARANCES IN AN ALCOVE.

FIGURE 4.

HARD W A TER

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.

In buildings of conventional frame, brick or stone construction,
unconfined spaces may provide adequate air for combustion and
ventilation.

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 SP ACE

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) OF THE ENCLOSURE BOTTOM. Each
opening shall have a free area of at least one square inch per 1000
Btuh (2,203mm
100 square inches (645 cm²).

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
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
enclosure.

2

/kW) appliances in the enclosure, but not less than

2

/kW) of the total input of all appliances in the

2

/kW) of the total input of all appliances in the

AIR REQUIREMENTS

KEEP APPLIANCE AREA CLEAR AND FREE OF COMBUSTIBLE
MA TERIALS, GASOLINE AND OTHER FLAMMABLE V APORS AND
LIQUIDS.

DO NOT OBSTRUCT THE FLOW OF COMBUSTION AND
VENTILATING AIR.

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 CREA TES A RISK OF ASPHYXIATION.

MECHANICAL EXHAUSTING OF ROOM AIR

Where an exhaust fan is installed in the same room with a heater,
sufficient openings for air must be provided in the walls.

UNDERSIZED OPENINGS WILL CAUSE AIR TO BE DRA WN INTO
THE ROOM THROUGH THE HEATER’S VENTING SYSTEM,
CAUSING POOR COMBUSTION. SOOTING MAY RESULT IN

CHEMICAL V APOR CORROSION

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.

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.

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 , UNCONT AMINA TED AIR SHOULD
BE OBTAINED FROM REMOTE OR OUTSIDE SOURCES.

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.

7

US DIRECT VENT

TO PREVENT EXHAUSTING PRODUCTS FROM CIRCULATING T O THE
AIR INTAKE IN WINDY/COLD AREAS, THE MAXIMUM PRACTICAL
DISTANCE BETWEEN THESE TWO TERMINALS IS RECOMMENDED.

CANADIAN DIRECT VENT

CAUTION

FIGURE 5.

8

US HORIZONTAL VENT

TO PREVENT EXHAUSTING PRODUCTS FROM CIRCULATING T O THE
AIR INTAKE IN WINDY/COLD AREAS, THE MAXIMUM PRACTICAL
DISTANCE BETWEEN THESE TWO TERMINALS IS RECOMMENDED.

CANADIAN HORIZONTAL VENT

CAUTION

FIGURE 6.

9

Heater must be protected from freezing downdrafts during
shutdown periods.

WARNING

NEVER OPERATE THE HEATER UNLESS IT IS VENTED TO
THE OUTDOORS AND HAS ADEQUATE AIR SUPPL Y TO A VOID
RISKS OF IMPROPER OPERATION, FIRE, EXPLOSION OR
ASPHYXIATION.

VENT PIPE TERMINA TION

3"x 4" PVC REDUCER WITH INTAKE GUARD

FIGURE 7.

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 INT AKE 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 ISOLA TION PIPE HANGERS ARE USED. THIS PREVENTS
ANY VIBRA TIONS 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
Canadian Electrical Code, CSA C22.1.

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.

W ARNING

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.

FIGURE 8.

DIRECT VENT TERMINAL INST ALLATION

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.

IMPORTANT

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.
TERMINA TION OF A VENT SYSTEM WITH A DEVICE OTHER THAN
THE SUPPLIED VENT TERMINATIONS WILL AFFECT SYSTEM
PERFORMANCE AND RESULT IN A SAFETY HAZARD.

DIRECT VENTING

The air intake provided on the unit contains an intake guard,
see Figure 7.

IMPORTANT

4" VENT AND INTAKE TERMINALS ARE PROVIDED FOR NEW
INST ALLA TIONS. 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.

NOTE: TO PREVENT EXHAUSTING PRODUCTS FROM
CIRCULATING T O THE AIR INTAKE IN WINDY/COLD AREAS, THE
MAXIMUM PRACTICAL DISTANCE BETWEEN THESE TWO
TERMINALS IS RECOMMENDED.

IMPORTANT

WHEN LOCATING THE TERMINALS ON A SIDEWALL, THE
FOLLOWING SPECIFICATIONS PERTAINING TO TERMINAL
LOCA TION MUST BE FOLLOWED.

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.

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).

FIGURE 9.

INST ALLA TION 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.

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.

EXHAUST VENT TERMINAL

NOTE: BEFORE BEGINNING INSTALLA TION OF ANY VENT PIPE
READ THE VENT PIPE MANUFACTURER'S INSTALLATION
INSTRUCTIONS.

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.

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.

3. A) MASONRY SIDE WALLS
Chisel an opening approximately 1/2" (1.3 cm) larger than the
marked circle.

B) WOODEN SIDE WALLS
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. Cut a length of PVC pipe about 3.5" (8.9 cm) longer than the wall
thickness at the opening.

5. Glue the intake vent terminal to the section of the pipe.

6. Slide the wall plate over the pipe to stop against intake vent terminal.

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.

8. If the vent pipe is inst alled 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.

INTAKE VENT TERMINAL

FIGURE 10.

VERTICAL VENT TERMINAL INST ALLA TION

IMPORTANT

WHEN TERMINATING THROUGH A ROOF, THE FOLLOWING
SPECIFICATIONS PERT AINING TO TERMINAL LOCA TION MUST
BE FOLLOWED.

1. Proper support must be provided for all pipe protruding through
the roof.

2. The vertical roof terminations should be sealed with a plumbing
roof boot or equivalent flashing.

3. The intake vent termination and the exhaust vent termination
must penetrate the same side of roof.

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.

The specifications are displayed in Figure 11.
NOTE: Exhaust vent terminal is installed using the same procedure.

INST ALLA TION SEQUENCE

NOTE: BEFORE BEGINNING INSTALLATION OF ANY VENT
PIPE, READ “VENT PIPE PREP ARA TION” SECTION ON PAGE 12.

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.

11

2. Drill a pilot hole approximately 1/4" (6 mm) 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 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.

3. Suspend the pipe through center of hole using proper support.

4. Slide roof boot or equivalent flashing over pipe and secure roof
boot equivalent flashing to roof.

5. Seal around flashing.

6. T erminate intake terminal and exhaust vent terminal facing down.
See Figure 11.

FIGURE 11.

INST ALLATION OF VENT SYSTEM

WARNING

THE OPTIONAL INTAKE VENTING ARRANGEMENT AND THE
EXHAUST VENTING ARRANGEMENT MUST BE INSTALLED TO
RUN DIRECTLY T O THE OUTDOORS AND NOT IN ANY WAY BE
CONNECTED TO ANOTHER 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 INCORRECTL Y , IT MAY CAUSE IMPROPER
OPERATION, FIRE, EXPLOSION, OR ASPHYXIATION.

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.

3. The unit is certified to a minimum amount of 4-inch pipe for 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

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.

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.

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.

5. It is important that condensate not be allowed to buildup in the

exhaust vent pipe. T o 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.

6. The vent system should be supported every 5 feet (152 cm) of vertical

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.

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 80­equivalent feet of 4-inch PVC pipe may be used on the exhaust venting
arrangement. The maximum number of 90 degree elbows for the 4­inch 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.

T able 2. VENT LENGTH TABLE

Number 4" PVC

of 90° Maximum Maximum

Elbows Feet. of Pipe Meters of Pipe

ONE (1) 65' 19.7 m
TWO (2) 60' 18.2 m

THREE (3) 55' 16.7 m

FOUR (4) 50' 15.2 m

FIVE (5) 45' 13.6 m

SIX (6) 40' 12.1 m

INLET VIEW

OUTLET VIEW

FIGURE 12.

12

VENT PIPE PREP ARA TION

1. INITIAL PREPARATION
A. Make sure the solvent cement you are planning to use is

designed for the specific application you are attempting.

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.

BLOCKED OUTLET PROVER SWITCH

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.

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.

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.

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.

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.

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 13.

BLOCKED INLET PROVER SWITCH

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 eighty (80) 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.

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 LOCA TED ON INLET SIDE OF GAS
VALVE. See Figure 13.

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-VENTILA TED AREA.

CONTROLS AND SWITCHES

The BTH-300 & 400 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.

BLOWER PROVER SWITCH

The Blower Prover Switch is provided on the heater to verify that
the fan is operating. It is a positive pressure switch whose electrical
contacts are normally open. When the fan increases the pressure
in the burner, the pressure switch will allow the electrical contacts

FIGURE 13.

ON/OFF SWITCH

The ON/OFF Switch is a single-pole, single-throw rocker switch.
This switch provides 120V from the line source to the heater.

CAUTION

THE WATER HEATER IS POLARITY SENSITIVE. BEFORE
APPLYING ELECTRICITY TO THIS HEATER BE CERTAIN THAT
SUPPLY NEUTRAL WIRE TO GROUND CHECK INDICA TES ZERO
VOL TAGE.

13

HOT SURF ACE 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.

FIRE OR EXPLOSION. IF OVERPRESSURE HAS OCCURRED
SUCH AS THROUGH IMPROPER TESTING OF GAS LINES OR
EMERGENCY MALFUNCTION OF THE SUPPLY SYSTEM THE
GAS VAL VE MUST BE CHECKED FOR SAFE OPERA TION. MAKE
SURE THAT THE OUTSIDE VENTS ON THE SUPPLY
REGULATORS AND THE SAFETY VENT VALVES ARE
PROTECTED AGAINST BLOCKAGE. THESE ARE PARTS OF
THE GAS SUPPLY SYSTEM, NOT THE HEATER. VENT
BLOCKAGE MAY OCCUR DURING ICE STORMS. IT IS
IMPORTANT TO GUARD AGAINST GAS VALVE FOULING
FROM CONT AMINANTS IN THE GAS W A YS. SUCH FOULING
MAY CAUSE IMPROPER OPERATION, FIRE OR EXPLOSION.

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.

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 NORMAL IRON PIPE SIZES (INCHES)

IN INPUT IN THOUSANDS BTU/HR

FEET 1 1/4" 1 1/2" 2" 2 1/2" 3" 4"

10 1400 2100 3960 6300 11000 23000
20 950 1460 2750 4360 7700 15800
30 770 1180 2200 3520 6250 12800
40 660 990 1900 3000 5300 10900
50 580 900 1680 2650 4750 9700
60 530 810 1520 2400 4300 8800
70 490 750 1400 2250 3900 8100
80 460 690 1300 2050 3700 7500

90 430 650 1220 1950 3450 7200
100 400 620 1150 1850 3250 6700
125 360 550 1020 1650 2950 6000
150 325 500 950 1500 2650 5500
175 300 460 850 1370 2450 5000
200 430 800 1280 2280 4600

LENGTH NORMAL IRON PIPE SIZES (INCHES)

IN INPUT IN KW

METERS 1 1/4" 1 1/2" 2" 2 1/2" 3" 4"

3.0 410 615 1160 1845 3221 6735

6.1 278 428 805 1277 2255 4626

9.1 225 346 644 1031 1830 3748

12.2 193 290 556 878 1552 3192

15.2 170 264 492 776 1391 2840

18.3 155 237 445 703 1259 2577

21.3 143 220 410 659 1142 2372

24.4 135 202 381 600 1083 2196

27.4 126 190 357 571 1010 2108

30.5 117 182 337 542 952 1962

38.1 105 161 299 483 864 1757

45.7 95 146 278 439 776 1610

53.3 88 135 249 401 717 1464

61.0 126 234 375 688 1347

BEFORE ATTACHING THE GAS LINE BE SURE THAT ALL GAS
PIPE IS CLEAN ON THE INSIDE.

TO TRAP ANY DIRT OR FOREIGN MA TERIAL IN THE GAS SUPPL Y
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. INST ALL IN ACCORDANCE
WITH RECOMMENDATIONS OF SERVING GAS SUPPLIERS.
REFER TO THE

NATIONAL FUEL GAS CODE OR THE NATURAL

GAS AND PROPANE INSTALLATION CODE CSA B149.1.

FIGURE 14.

CONNECTION OF GAS PIPE

1. When connecting gas pipe to unit, apply wrench to flange only.
Note: Do not use wrench on gas valve or gas bracket.

2. PERFORM THE GAS LEAK TEST ANY TIME WORK IS DONE
ON A GAS SYSTEM TO A VOID THE POSSIBILITY OF FIRE OR
EXPLOSION WITH PROPERTY DAMAGE, PERSONAL INJUR Y
OR LOSS OF LIFE.

The Gas Leak T est 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.

T o prevent damage, care must be taken not to apply too much torque
when attaching gas supply pipe to gas valve inlet.

WARNING

THE HEA TER IS NOT INTENDED FOR OPERATION AT HIGHER
THAN 11.0" WATER COLUMN (2.74 Kpa) FOR NATURAL GAS
AND 14.0" W.C. (3.49kPa) FOR PROPANE GAS SUPPLY
PRESSURE. HIGHER GAS SUPPLY PRESSURES REQUIRE
SUPPLEMENTAL REDUCING SERVICE REGULATION.
EXPOSURE TO HIGHER GAS SUPPL Y PRESSURE MA Y CAUSE
DAMAGE TO THE GAS CONTROLS WHICH COULD RESULT IN

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.

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

14

LESS, THE APPLIANCE NEED NOT BE DISCONNECTED, BUT MUST
BE ISOLA TED FROM THE SUPPL Y PRESSURE TEST BY CLOSING
THE MANUAL GAS SHUTOFF VAL VE.

BEFORE PLACING THE HEATER IN OPERATION, CHECK FOR
GAS LEAKAGE. USE SOAP AND W ATER SOLUTION OR OTHER
MATERIAL ACCEPTABLE FOR THE PURPOSE OF LOCATING
GAS LEAKS. DO NOT USE MATCHES, CANDLES, FLAME OR
OTHER SOURCES OF IGNITION FOR THIS PURPOSE.

PURGING

Gas line purging is required with new piping or systems in which air
has entered.

CAUTION

PURGING SHOULD BE PERFORMED BY PERSONS
EXPERIENCED IN THIS TYPE OF GAS SERVICE. TO A VOID RISK
OF FIRE OR EXPLOSION, PURGE DISCHARGE MUST NOT
ENTER CONFINED AREAS OR SPACES WHERE IGNITION CAN
OCCUR. THE AREA MUST BE WELL VENTILATED AND ALL
SOURCES OF IGNITION MUST BE INACTIV A TED OR REMOVED.

GAS METER SIZE - CITY GASES ONLY

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.

GAS V ALVES

WARNING

SHOULD OVERHEA TING OCCUR OR THE GAS SUPPLY F AIL T O
SHUT OFF, TURN OFF THE MANUAL GAS CONTROL VALVE TO
THE APPLIANCE.

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.

W ARNING

THE PURPOSE OF A RELIEF VALVE IS TO AVOID EXCESSIVE
PRESSURE OR TEMPERATURE INTO THE STEAM RANGE,
WHICH MAY CAUSE SCALDING AT FIXTURES, TANK
EXPLOSION, SYSTEM OR HEATER DAMAGE. NO VALVE IS TO
BE PLACED BETWEEN THE RELIEF VALVE AND THE TANK.

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 V AL VE OUTLET AND MUST
NOT CONTAIN VALVES OR RESTRICTIONS, NOR SHOULD IT
BE LOCATED IN FREEZING AREAS. DO NOT THREAD OR CAP
THE END OF THIS LINE. RESTRICTED OR BLOCKED
DISCHARGE WILL DEFEA T THE PURPOSE OF THE VALVE AND
IS UNSAFE. THE DISCHARGE LINE SHALL BE INSTALLED TO
ALLOW COMPLETE DRAINAGE OF BOTH THE VALVE AND LINE.

WATER LINE CONNECTIONS

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.

CLOSED SYSTEM

SYSTEM CONNECTIONS

The system installation must conform to these instructions and to
the local code authority having jurisdiction. Good practice requires
that all heavy piping be supported.

THERMOMETERS (Not Supplied)

Thermometers should be obtained and field installed as shown in
the installation diagrams.

Thermometers are installed in the system as a means of detecting
the temperature of the outlet water supply.

RELIEF V AL VE

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.

FOR SAFE OPERATION OF THE WATER HEATER, THE RELIEF
V ALVE(S) MUST NOT BE REMOVED OR PLUGGED.

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

A closed system will exist if a check valve (without bypass), pressure

CAUTION

reducing valve (without bypass), or a water meter (without bypass)
is installed in the cold water line between the water heater and
street main (or well).

Excessive pressure may develop 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
be required in the inlet supply line between the appliance and the
meter or valve to compensate for the thermal expansion of water
under supply pressure.

If a water heater is installed in a closed water system, check local
codes or contact the water supplier or local plumbing inspector on
how to control this situation.

WATER (POTABLE) HEA TING AND SP ACE HEATING

1. All piping components connected to this unit for space heating
applications shall be suitable for use with potable water.

2. Toxic chemicals, such as those used for boiler treatment, shall
NEVER be introduced into this system.

3. This unit may never be connected to any existing heating system
or component(s) previously used with non-potable water heating
appliance.

15

4. When the system requires water for space heating at
temperatures higher than required for domestic water purposes,
a tempering valve must be installed. Please refer to installation
diagrams on pages 23 through 28 in back of manual for
suggested piping arrangements.

HEA TER WIRING

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.

THE COMPUTER CONTROL REQUIRES A SOURCE OF
STABLE 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.

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.

All electrical work must be installed in accordance with the
Electrical Code, NFPA 70 or the Canadian Electrical Code, CSA
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.

DO NOT ENERGIZE THE BRANCH CIRCUIT BEFORE THE
HEATER TANK IS FILLED WITH WATER.

NOTE: This controller is Polarity Sensitive. If the Hot and Neutral
Supply Voltage is reversed, the controller will not sense flame. V erify
polarity before connecting the unit.

National

FIGURE 15.

16

FIGURE 16.

17

OPERATION

SELF DIAGNOSTIC CONTROLLER

SEQUENCE OF OPERA TION

Typical Control/Appliance Operating Sequence

1. When the control is powered, it should first display “0”, then
the input line voltage (“120”), the calibration setting (12), then
the actual water temperature in the tank.

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 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.

8. After an additional 2 seconds, the control will monitor the flame
sense probe to confirm a flame is present. If a flame is not
verified within this time period, the gas valve will immediately
be closed, and the blower will continue to run for approximately
10 seconds. The control will then return to step 2.

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. During
this idle state, if the control detects an improper operating state
for external devices such as the ECO switch, vent switch,
pressure switch, etc., the appropriate LED(s) on the Display
Board will be illuminated indicating the nature of the fault.

This controller is designed for ignition lockout after three consecutive
failed attempts to light. If lockout occurs, the display lights will match
Figure 17. Along with this, a numeric message will appear in the
display. The following list of ERROR CODES illustrates possible
numeric failures.

FIGURE 17.

GAS V ALVE LED FLASHING

This condition results from a failure to establish burner ignition af ter
three successive trials. In such cases:

1. Investigate the possible cause and remedy any observations.

2. Momentarily depress the button on the display panel to reset the
lockout condition.

3. Confirm proper appliance operation.

Possible Cause Remedy

1. Burner ground wire broken 1. Check wire and connection
or corroded at burner

2. Connectors unplugged 2. Check connections

3. Igniter broken 3. Replace igniter

4. Flame probe faulty 4. Replace flame probe

5. Gas shut off 5. Turn on gas supply

6. Clogged gas valve 6. Replace gas valve

7. Faulty gas valve 7. Replace gas valve

8. Defective control 8. Replace control

9. Burner improperly adjusted 9. Adjust burner

10.Dirty burner 10.Clean burner

18

ERROR CODES

The following Error Codes are external to the controller.

01 Pressure Switch Fail On, should be Off
11 Pressure Switch Fail Off, should be On
02 Ignition Fail after 3 attempts
04 ECO Open
05 Temperature Probe Open
15 Temperature Out of Bounds < 30 degrees
25 Temperature Out of Bounds > 220 degrees

The following Error Codes are internal to the controller.

113 Flame On Should be Off Fail
22 Ignition Relay Fail is On, should be Off
112 Ignition Relay Fail is Off, should be On
101 K2 Fail in K1
102 Main Loop Fail in K2
103 K1 Fail in Main Loop

Gas Valve Power Supply. (*WDPS Watch Dog Power Supply).

106 WDPS Fail to be Off
107 WDPS Fail to be Off
108 WDPS Fail to be On
116 Gas Valve Relay Fail is off, should be On
117 Gas Valve Relay Fail is On, should be Off

Checks The ROM (Read Only Memory).

200 CRC Check Sum Error

Checks The CPU (Central Processing Unit).

201 CPU Instruction Test Error
202 CPU Instruction Test Error
203 CPU Instruction Test Error

Checks the RAM (Random Access Memory).

205 RAM Test Fail

SW Check to see what the Last State it was in.
ie., Fails if it can from the wrong place

125 State Error
126 State Error
128 State Error
127 State Error
129 State Error
131 State Error
132 State Error

These State Numbers are not used.

230 Executed State 3 (Not Implemented) h.s.
240 Executed State 4 (Not Implemented) h.s
210 Executed State 10 (Not Implemented) h.s.
213 Executed State 13 (Not Implemented) h.s.
214 Executed State 14 (Not Implemented) h.s.
216 Executed State 16 (Not Implemented) h.s.

FAU L T CONDITIONS

The controller is set up to provide additional status indicators under
Fault Conditions. The following figures are possible Fault Conditions.

NO INCOMING LINE VOLTAGE. See Figure 18.

Line LED Off

Possible Cause Remedy

1. No Input Power 1. Apply Power

2. Wiring Disconnected 2. Check all wiring

3. One or more wiring receptacles 3. Reconnect plugs on control,
disconnected from control confirm all are fully seated

4. LED burned out 4. Ignore or replace control

NO LOW VOL TAGE. See Figure 19.

24V AC LED Off

NO LOW VOLTAGE, 24V AC LED Off

FIGURE 19.

NOTE: The transformer is of Class II variety and has an internal non-

replaceable fuse. If blown, a problem may exist with the control which is
affecting the transformer . In such cases, the control should be replaced
as well.

Possible Cause Remedy

1. Transformer wiring problem 1. Repair Wiring

2. Defective Transformer 2. Replace Transformer

3. LED burned out 3. Ignore or replace control

TEMPERA TURE PROBE FAUL T. See Figure 20.

Water Temp LED Flashing

NO INCOMING LINE VOLTAGE, Line LED Off

FIGURE 18.

TEMPERATURE PROBE FAULT, Water Temp LED Flashing

FIGURE 20.

This condition accommodates multiple failure modes. T o more accurately
determine the cause of failure, press the push-button on the display board.

19

Display Flashes “05” when button is pressed:

Possible Cause Remedy

1. Temperature Probe wiring 1. Repair Wiring
open

2. Defective probe 2. Replace probe

Display Flashes “15” when button is pressed:

Possible Cause Remedy

1. No water in tank and tank 1. The symptom does not

in freezing conditions reflect a control problem

2. Water in tank above freezing 2. Temperature probe out of

tolerance, replace temp.
probe

Display Flashes “25” when button is pressed:

Possible Cause Remedy

1. Water in tank is low, probe 1. Fill tank
immersed in steam

2. Probe wiring shorted 2. Repair wiring

3. Defective probe 3. Replace probe

ECO SWITCH OPEN. See Figure 21.

ECO LED Flashing:

CONTROL BAD, All LEDs Flashing

FIGURE 22.

Possible Cause Remedy

1. Temp. Probe unplugged 1. Check connectors

2. Temp. probe wiring damaged 2. Repair wiring

3. Water in tank too hot 3. Normal condition when
water temperature
exceeds safety limit.
Allow water to cool or
admit water into tank and
manually reset the control.
Determine cause for
overtemp condition.

COMBUSTION AIR BLOCKAGE. See Figure 23.

Pressure Switch LED Flashing:

ECO SWITCH OPEN, ECO LED Flashing

FIGURE 21.

Possible Cause Remedy

1. This indicates the control has 1. Press button on the
failed on of its internal display board to reset
diagnostic self-tests. control. If this error

occurs repeatedly,
replace control.

CONTROL BAD. See Figure 22.

All LEDs Flashing:

COMBUSTION AIR BLOCKAGE, Pressure Switch LED Flashing

FIGURE 23.

Possible Cause Remedy

1. Combustion air blocked 1. Check exhaust piping and

2. Blower not operating: 2. a. Repair wiring
a. Check blower wiring b. Replace blower motor
b. Check blower motor

3. Defective air switch 3. Replace air switch

4. Pressure switch jumped out 4. This controller must sense

20

flue for obstructions

an open contact on the
blower proving airflow
switch before the blower
comes on. Check to see if
blower proving airflow
switch is still connected to
the unit.

PRIOR TO START UP - REQUIRED ABILITY

INSTALLATION OR SERVICE OF THIS WATER HEATER
REQUIRES ABILITY EQUIVALENT TO THAT OF A LICENSED
TRADESMAN IN THE FIELD INVOLVED. PLUMBING, AIR SUPPLY,
VENTING, GAS SUPPL Y AND ELECTRICAL WORK ARE REQUIRED.

Before attempting start-up, thoroughly study and familiarize yourself
with the exact sequence of operation and all other details on the
specific heater being used.

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.

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.

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.

• You are now ready to begin the burner start-up procedure.

OPERATING INSTRUCTIONS

IMPORTANT

IT IS RECOMMENDED THA T A QUALIFIED SER VICE TECHNICIAN
PERFORM THE INITIAL FIRING OF THE HEA TER. A T THIS TIME
THE USER SHOULD ASK THE TECHNICIAN ANY QUESTIONS IN
REGARD TO THE OPERATION AND MAINTENANCE OF THE
UNIT.

CAUTION

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.

NEVER OPERATE THE HEATER WITHOUT FIRST BEING
CERT AIN IT IS FILLED WITH WA TER AND A TEMPERA TURE AND
A PRESSURE RELIEF VALVE IS INSTALLED IN THE RELIEF
VALVE OPENING OF THE HEATER. DO NOT ATTEMPT TO
OPERATE HEA TER WITH COLD W A TER INLET V ALVE CLOSED.

FILLING:

1. Close the heater drain valve.

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.

THE MAIN MANUAL GAS SHUTOFF VALVE MUST HAVE BEEN
CLOSED FOR AT LEAST FIVE (5) MINUTES. THIS WAITING
PERIOD IS AN IMPOR T ANT SAFETY STEP. ITS PURPOSE IS TO
PERMIT GAS THAT MIGHT HAVE ACCUMULATED IN THE
COMBUSTION CHAMBER TO CLEAR. IF YOU DETECT GAS AT
THE END OF THIS PERIOD, DO NOT PROCEED WITH LIGHTING.
RECOGNIZE THA T GAS ODOR, EVEN IF IT SEEMS WEAK, MAY
INDICATE THE PRESENCE OF ACCUMULATED GAS
SOMEPLACE IN THE AREA WITH A RISK OF FIRE OR
EXPLOSION. SEE THE FRONT P AGE FOR STEPS TO BE T AKEN.

DO NOT USE THIS HEATER IF ANY PART HAS BEEN UNDER
WATER. IMMEDIATELY CALL A QUALIFIED SERVICE
TECHNICIAN TO INSPECT THE HEA TER AND TO REPLACE ANY
PART OF THE CONTROL SYSTEM AND ANY GAS CONTROL
WHICH HAS BEEN UNDER WATER.

LIGHT THE UNIT IN ACCORDANCE WITH THE OPERATING
INSTRUCTIONS LABEL A TT ACHED T O THE HEATER.

THESE INSTRUCTIONS ARE REPEA TED IN THE LIGHTING AND
OPERATING LABEL ILLUSTRATION ON PAGE 20 IN THIS
MANUAL.

ADJUSTMENT PROCEDURE - INITIAL ST ART -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.

1. Check gas line pressure with a manometer.

2. Check manifold pressure (see T able 4, page 23) using a pressure
gauge (manometer) connected to the manifold pressure tap on
the gas control valve, (Figure 15).

If full rate adjustment is required, remove cover screw from top of
the gas control valve, (Figure 15).

Using a small screwdriver, turn adjusting screw clockwise
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.

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:

For appliance installation locations with elevations above 2000 feet
(610 m) refer to HIGH ALTITUDE INSTALLATIONS section of this
manual.

a. Attach a pressure gauge (manometer) to the manifold

pressure tap (Figure 16) and refer to Table 4, page 20 for
correct pressure.

b. Use this formula to “clock” the meter. Be sure other gas

consuming appliances are not operating during this interval.
3600

X H = Btuh

T

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
H = 1050 Btu/ft.
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:

3

3600

X 1050 = 300,000 Btuh (87.9 kW)

12.6

to

21

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.

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

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 press ure
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.

WARNING

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.

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”

• 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

IF YOU DO NOT FOLLOW THESE INSTRUCTIONS EXACTLY A FIRE OR EXPLOSION
MAY RESULT CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR LOSS OF LIFE.

OPERA TING INSTRUCTIONS

1. STOP! Read the safety information above on this
label.

2. Set thermostat to lowest setting.

3. Turn off all electric power to the appliance.

4. This appliance is equipped with an ignition device which
automatically lights the burner. Do not try to light the
burner by hand.

telephone. Follow the gas supplier’s instructions.

• If you cannot reach your gas supplier, call the fire
department.

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.

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.

9. Set thermostat to desired setting.

10. If the appliance will not operate, follow the instructions
“To Turn Off Gas To Appliance” and call your service
technician or gas supplier.

5. Push in gas control knob slightly and turn clockwise
to “OFF”.

6. Wait five (5) minutes to clear out any gas. If y ou then
smell gas, STOP! Follow “B” in the safety information
above on 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. Set the thermostat to lowest setting.

2. Turn off all electric power to appliance if service is to be performed.

3. Push in gas control knob slightly and turn clockwise to “OFF”. Do not force.

22

WARNING

UNDER NO CIRCUMSTANCES SHOULD THE INPUT EXCEED
THE RATE SHOWN ON THE HEATER RATING PLATE.
OVERFIRING COULD RESUL T IN DAMAGE OR SOOTING OF THE
HEATER.

CA THODIC PROTECTION

CAUTION

HYDROGEN GAS CAN BE PRODUCED IN A HOT W ATER SYSTEM
SERVED BY THIS HEATER THAT HAS NOT BEEN USED FOR A
LONG PERIOD OF TIME (GENERALLY TWO WEEKS OR MORE).
HYDROGEN GAS IS EXTREMELY FLAMMABLE. To reduce the

risk of injury under 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.

PRECAUTIONS

IF THE UNIT IS EXPOSED TO OR EXHIBITS THE FOLLOWING,
DO NOT OPERATE HEATER UNTIL ALL CORRECTIVE STEPS
HA VE BEEN MADE BY A QUALIFIED SER VICEMAN.

1. FLOODING TO OR ABOVE THE LEVEL OF THE BURNER OR
CONTROLS

2. EXTERNAL DAMAGE

3. FIRING WITHOUT WATER

4. SOOTING

NEVER OPERATE THE HEATER WITHOUT FIRST BEING
CERT AIN IT IS FILLED WITH WA TER AND A TEMPERA TURE AND
PRESSURE RELIEF VAL VE IS INST ALLED IN THE RELIEF VA LVE
OPENING OF THE HEATER.

SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAIL
TO SHUT OFF, TURN OFF THE MANUAL GAS CONTROL VALVE
TO THE APPLIANCE.

GENERAL INFORMATION

HIGH AL TITUDE INST ALLATIONS

W ARNING

BTH HEATERS ARE CERTIFIED FOR USE WITHOUT
MODIFICATION FOR ALTITUDES UP TO 2000 FEET.
INSTALLATIONS ABOVE 2000 FEET MAY REQUIRE
REPLACEMENT OF THE BURNER ORIFICE. CALL THE
TECHNICAL INFORMATION CENTER AT [phone] FOR
REQUIREMENTS.

HIGH AL TITUDE ADJUSTMENTS

FOR BTH 300 AND 400

NA TURAL GAS

ELEV ATION (ft./m) MANIFOLD SETTING (in W.C./Kpa)

Up to 2,000 ft./610 m. 4.0/1.25 - NO ADJUSTMENT

2,001 - 3,000 ft./914 m. 3.8/0.946
3,001 - 4,000 ft./1,219 m. 3.7/0.921
4,001 - 5,000 ft./1,524 m. 3.7/0.921
5,001 - 6,000 ft./1,829 m. 3.6/0.896
6,001 - 7,000 ft./2,134 m. 3.6/0.896
7,001 - 8,000 ft./2,438 m. 3.5/0.871

PROPANE GAS

ELEV ATION (ft./m) MANIFOLD SETTING (in W.C./Kpa)

Up to 2,000 ft./610 m. 10.0/2.49 - NO ADJUSTMENT

2,001 - 3,000 ft./914 m. 9.9/2.46
3,001 - 4,000 ft./1,219 m. 9.8/2.44
4,001 - 5,000 ft./1,524 m. 9.7/2.41
5,001 - 6,000 ft./1,829 m. 8.4/2.09
6,001 - 7,000 ft./2,134 m. 7.2/1.79
7,001 - 8,000 ft./2,438 m. 6.1/1.52

POWER BURNER

The initial start-up procedure of the unit is provided on page 19.
The sequence of operation of the unit is provided on page 16.
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.

HIGH LIMIT

The high limit (not adjustable) is factory set to cutout at
202°F (94°C). The controller must be manually reset by depressing
the reset button on front of the control when water temperature drops
to below 160°F (71°C).

T ABLE 4.

GAS SUPPL Y SPECIFICATIONS Nat. Gas LP Gas

Max. Gas Supply Pressure W.C. 11.00 14.00
Max. Gas Supply Pressure kPa 2.74 3.49
Nominal Gas Supply Pressure W.C. 7.00 11.00
Nominal Gas Supply Pressure kPa 1.74 2.74
Minimum Gas Supply Pressure W.C.* 5.20 11.0
Minimum Gas Supply Pressure kPa* 1.54 2.74
Manifold Gas Supply Pressure W.C. 4.00 10.0
Manifold Gas Supply Pressure kPa 1.25 2.49

* Minimum pressure for purposes of rate adjustment

Some gas utility companies derate their gas for altitude, making it
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

GENERAL

KEEP APPLIANCE AREA CLEAR AND FREE FROM
COMBUSTIBLE MATERIALS, GASOLINE AND OTHER
FLAMMABLE VAPORS AND LIQUIDS. (SEE WARNING ON
PAGE 5, LOCATING THE HEATER).

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.

23

MAINTENANCE SCHEDULE

Following are the instructions for performing some of the
recommended maintenance. Unit inspection and adjustment should
be performed by a competent technician.

COMPONENT OPERATION INTERVAL REQUIRED

Tank Sediment Monthly Flushing

Tank Lime Scale Semi UN-LIME

Powered Anode Inspect Semi

System Annually

Relief Valve Inspect Semi

Removal

®

Removal Annually Delimer

Annually

direct proportion to water temperature and usage. The higher the
water temperature or water usage, the more lime deposits are
dropped out of the water. This is the lime scale which forms in pipes,
heaters and on cooking utensils.

Lime accumulation not only reduces the life of the equipment but
also reduces efficiency of the heater and increases fuel consumption.

The usage of water softening equipment greatly reduces the
hardness of the water. However, this equipment does not always
remove all of the hardness (lime). For this reason it is recommended
that a regular schedule for deliming be maintained.

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
reached the bottom of the cleanout opening or about 1" (2.5cm) of
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.

Blower Screen and As Required Soft Brush

Clean Inlet

Blower Wheel

Vent System Inspect Every 3 Joints should

Months be sealed

(1) If furnished with oiling provision.

NOTE: UN•LIME is not available in Canada. Please call Customer

Service at 1-800-265-8520 for approved alternatives.

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.

Example 1:

Initial inspection shows 1/2" (1.3cm) of lime accumulation.
Therefore, the heater can be delimed once a year.

Example 2 :

Initial inspection shows 2" (5cm) of lime accumulation. Therefore,
the heater should be delimed every 3 months.

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.

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.

• 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.

For convenience, sediment removal and lime scale removal should
be performed at the same time.

LIME SCALE REMOV AL

The amount of calcium carbonate (lime) released from water is in

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.

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.

A.O. Smith Form No. 4800 Rev. 8, entitled “Why, When and How”,
describes tank cleaning methods and materials. UN•LIME and the
booklet may be obtained through your A.O. Smith dealer or distributor .

The cleanout opening is shown in Figure 24. T o clean heater through
cleanout opening, proceed as follow:

1. Turn off water inlet valve, the heater electrical disconnect switch
and open drain valve.

24

2. Remove outer cover plate from lower side of heater jacket.

No light means no line voltage or a defective power supply.

3. Remove cover from cleanout opening.

4. Remove lime, scale or sediment using care not to damage the
glass-lining.

5. Inspect cleanout plate gasket: If new gasket is required, replace
with A. O. Smith part no. 99038.

6. Install cleanout plate. Be sure to draw plate up tight by tightening
screws securely.

7. Close drain valve, open water inlet line and turn on the power
burner electrical disconnect switch.

8. Check for water leakage.

9. Replace outer jacket cover plate.

POWERED ANODE SYSTEM

The BTH-300 & 400 are factory equipped with a powered anode
system. The anodes are of a permanent design and do not need
replacing unless damaged.

POWERED ANODE OPERA TION

To insure a long, trouble-free operating life, the BTH-300 & 400 are
equipped with a powered anode system consisting of:

1. A power supply with a built-in diagnostic LED.

2. Two titanium anodes.

3. Wiring harness with ground lead.

Replacement parts for this system may be ordered from A.O. Smith
Product Service Division; see BTH-300 & 400 parts list for specific
details.

Flashing red light can mean (1) the heater has no water or
(2) a broken or loose connection has occurred.

DRAIN V AL VE AND ACCESS P ANELS

The heaters are equipped with a 3/4" drain valve.
An access panel covers the cleanout opening in the tank which is

sealed by a gasket and cover, see Figure 24.

RELIEF V AL VE

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.

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.

CAUTION

BEFORE MANUALLY OPERATING THE VAL VE, MAKE SURE THA T
A DRAIN LINE HAS BEEN A TT ACHED T O THE V AL VE TO DIRECT
THE DISCHARGE TO AN OPEN DRAIN. F AILURE TO T AKE THIS
PRECAUTION COULD MEAN CONT ACT WITH EXTREMEL Y HOT
WATER PASSING OUT THE VALVE DURING THIS CHECKING
OPERA TION.

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.

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.

FIGURE 25.

POWER SUPPLY LED MEANINGS:

The power supply diagnostic LED is located in the bottom right­hand corner of the BTH-300 & 400 control board.

Steady green light means powered anode system is functioning
normally.

Contact your water supplier or local plumbing inspector on how to
control this situation.

Two common corrections are listed in the Checklist and Service
Information which appears later in this manual.

ABOVE ALL, DO NOT PLUG THE TEMPERATURE AND
PRESSURE RELIEF VAL VE. THIS IS NOT A SOLUTION AND CAN
CREATE A HAZARDOUS SITUATION.

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.

3. Check all vent system connections for leakage and reseal as
required using Hi Temp Silicone sealer or equivalent.

25

INST ALLA TION DIAGRAMS

ONE TEMPERA TURE - ONE HEATER VERTICAL STORAGE T ANK FORCED CIRCULATION

WITH OR WITHOUT BUILDING RECIRCULA TION

CAUTION: IF BUILDING COLD

WATER SUPPLY HAS A BACK­FLOW PREVENTER, CHECK
VALVE OR WATER METER
WITH CHECK VALVE
PROVISIONS FOR THERMAL
EXP ANSION OF WA TER IN THE
HOT WATER SYSTEM MUST
BE PROVIDED

NOTE: CONNECT RETURN
LINE FROM HOT WATER
CIRCULA TING LOOP (IF USED)
TO COLD WATER INLET LINE.

* PIPE TO OPEN DRAIN

INSTALL IN ACCORDANCE
WITH LOCAL CODES

ONE TEMPERA TURE - ONE HEATER HORIZONTAL STORAGE TANK

FORCED CIRCULA TION 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

26

TWO TEMPERATURE - ONE HEATER HIGH TEMPERATURE

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.

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.

PIPE RELIEF VALVE TO OPEN DRAIN.

*

NOTE: IF TEMPERED WATER IS
RECIRCULA TED, RETURN LINE SHOULD BE
CONNECTED AT POINT “A”.

INSTALL IN ACCORDANCE WITH LOCAL
CODES.

27

TWO TEMPERA TURE - TWO HEATERS HIGH TEMPERATURE

WITH OR WITHOUT BUILDING RECIRCULATION

TWO TEMPERA TURE - THREE HEATERS (TWO PRE-HEATERS/ONE BOOSTER HEATER)

WITH OR WITHOUT BUILDING RECIRCULATION

MUST BE IDENTICAL HEA TERS

FOR MULTIPLE HEATER INSTALLATION SEE MANIFOLD KIT
SPECIFICA TIONS, PAGE 30.

CAUTION: IF BUILDING COLD WATER SUPPLY HAS A BACK­FLOW PREVENTER, CHECK VALVE OR WATER METER WITH
CHECK VALVE PROVISIONS FOR THERMAL EXPANSION OF
WATER IN THE HOT WATER SYSTEM MUST BE PROVIDED.

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.

28

TWO TEMPERA TURE - TWO HEATERS (ONE PRE-HEATER/ONE BOOSTER HEATER)

WITH OR WITHOUT BUILDING RECIRCULATION

DANGER

TEMPERATURE SETTING SHOULD NOT EXCEED SAFE TEMPERA TURE
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 RELIEF VALVE TO OPEN DRAIN
** 140°F (60°C)TO 150°F (66°C) SHOULD BE MAXIMUM WATER

TEMPERATURE MAINTAINED IN THE PRE-HEATERS.
120°F (49°C) SHOULD BE THE MINIMUM TEMPERA TURE OF

WATER IN THE PRE-HEATERS.
CONNECT CIRCULATING LINE FROM FIXTURES, IF USED,

TO COLD WATER SUPPLY LINE OF PRE-HEATER.
CONNECT CIRCULA TING LINE OF 180°F (82°C) OR BOOSTED

WATER, IF USED, TO INLET WATER LINE TO BOOSTER.
INSTALL IN ACCORDANCE WITH LOCAL CODES.

29

TWO TEMPERATURE - ONE HEATER HIGH TEMPERATURE

WITH RECIRCULA TION OF SANITIZING LOOP

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 BACK­FLOW PREVENTER, CHECK VALVE OR WATER METER WITH
CHECK VALVE PROVISIONS FOR THERMAL EXPANSION OF
WATER IN THE HOT WATER SYSTEM MUST BE PROVIDED.

*PIPE RELIEF VALVE TO OPEN DRAIN
INSTALL IN ACCORDANCE WITH LOCAL CODES

NOTE 1: TOGGLE SWITCH CONTROLS 180°F (82°C) WATER
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.

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).

NOTE 3: ADJUST PLUG COCK SO THE SANITIZING LOOP FLOW
RATE DOES NOT CAUSE UNNECESSARY TURBULENCE IN THE
TANK.

NOTE 4: IF TEMPERED WATER IS RECIRCULATED, RETURN
LINE SHOULD BE CONNECTED AT POINT A .

30

MANIFOLD KITS

Precision cut type “L” all copper A.O. Smith manifold kit s assure 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. Unions shown
in piping diagrams are not included in the manifold kits.

Dimensions shown are for minimum space occupied by the water heaters assemblies.
Space for the venting system and unit servicing must be added.

31

CHECKLIST AND SERVICE INFORMATION

IMPORTANT

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 re­fired after a prolonged shutdown. HOWEVER, it is recommended
that only qualified servicemen, using appropriate test equipment,
be allowed to service the heater.

10. Condensate hose may be blocked where it connects to the
exhaust elbow.

• Verify the condensate drains from the unit without restriction.

WATER IS TOO HOT

1. Refer to WATER TEMPERATURE CONTROL.

BE SURE TO TURN OFF THE ELECTRICITY WHENEVER
POSSIBLE OR APPROPRIATE WHILE CHECKING EQUIPMENT.

WARNING

FAILURE TO FOLLOW THESE INSTRUCTIONS CAN RESULT IN
SERIOUS PERSONAL INJURY OR DEATH.

CAUTION:

LABEL ALL WIRES PRIOR TO DISCONNECTION WHEN
SERVICING CONTROLS. WIRING ERRORS CAN CAUSE
IMPROPER AND DANGEROUS OPERATION.

VERIFY PROPER OPERA TION AFTER SERVICING.

BURNER OPERA TIONAL PROBLEMS

1. Refer to TROUBLESHOOTING.

NOT ENOUGH OR NO HOT WATER

1. Be certain the electrical disconnect switch serving the water
heater is in the ON position.

2. Check the fuses.

• The electrical disconnect switch usually contains fuses.

W A TER HEA TER MAKES SOUNDS

1. Sediment or lime scale accumulations cause rumbling and
pounding noises when the heater is operating.

• The sounds are normal, however, the tank bottom should be

cleaned. Refer to MAINTENANCE for details.

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.

WATER LEAKAGE IS SUSPECTED

1. Check to see if the water heater drain valve is tightly closed.
Also check the cleanout opening for leakage.

2. The apparent leakage may be condensation which forms on
cool surfaces of the heater and piping.

3. If the outlet of the relief valve is leaking it may represent:

• Excessive water pressure.

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.

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.

5. Look for hot water wastage and leaking or open hot water
faucets.

6. Sediment or lime scale may be affecting water heater operation.
Refer to MAINTENANCE for details.

7. The heater’s temperature high limit sensor has activated. Press
the reset button on the thermostat.

8. Burner may not be firing at proper rate.

• Check gas pressure. Adjust to obtain required manifold

pressure.

9. Burner fan wheel may be dirty.

• Excessive water temperature.

• Faulty relief valve.

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.

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.

TROUBLESHOOTING

1. Verify that the allowable vent length has not been exceeded and
that the blower inlet screen has been removed if direct venting.

2. Verify the gas supply volume and pressure per table 3 and 4.

3. Verify that the condensation, which WILL be present in the
heater and exhaust vent, will drain.

4. Check supply wire polarity - hot to hot and neutral to neutral
and no "stray" current in neutral.

• Clean fan wheel with a stiff brush.

5. Heater is properly grounded.

32

Checking these four (4) items first will often result in a timely solution
to the service call.

WARNING

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 METER AND A MICROMETER, DO NOT A TTEMPT TO
TROUBLESHOOT OR REP AIR A.O. SMITH EQUIPMENT.

AL TERING 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 T O IGNITION TEMPERATURE.

NOTE: ANY BYP ASS OR AL TERA TION 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 located on page 16 before continuing.

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 this tubing is damaged it must be replaced. If these
steps do not eliminate the problem, replace the pressure switches.

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.

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.

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 selection, page 19, for the
manifold pressure adjustment procedure.

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

THE WATER HEATER IS POLARITY SENSITIVE. BEFORE
APPLYING ELECTRICITY TO THIS HEATER BE CERTAIN THAT
SUPPLY NEUTRAL WIRE TO GROUND CHECK INDICA TES ZERO
VOL TAGE.

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.

2. For BTH 400, a VFD (Variable Frequency Drive) is used. "rdy"
(stands for ready) will be shown on display in standby heating
mode. "152" (152 output Hz) shall be shown on VFD display
during heater running. Any other display (other than "rdy" or "152")
indicates the VFD fault. Check 120V AC to the VFD power input
L1 and N terminals. Check the open contact of the relay (mounted
on VFD) wired to VFD terminal +15V and LI1. When calling for
heat, the relay should be energized, the relay contact will change
from "open" to "close", and VFD display will change from "rdy" to
"152", and blower starts to run. If there's no display change (from
"rdy" to "152") on VFD during the call for heat, check the wire
from the controller blower connector to the relay A1 and A2
terminal or replace the relay coil.

MOTOR RUNS, PREPURGE TIME ELAPSES BUT

MAIN FLAME NOT EST ABLISHED

1. Check to see if main manual gas valve is open.

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.

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
(see page 20). 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.

Note that a positive manifold pressure reading of approximately

1.5" (.38 kPa) W.C. is normal during the prepurge portion of the
ignition cycle due to the location of the gas orifice.

MOTOR RUNS, BURNER LIGHTS MOMENTARILY,

THEN LOCKS OUT

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 T able 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
OPERA TING INSTRUCTIONS section, page 19, for the manifold
pressure adjustment procedure.

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.

33

NOTE: Always turn off and disconnect main supply wiring before
servicing the unit.

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.

8. Confirm that the air inlet screen (see Figures 7 & 8) is free of
obstructions.

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.

NOISY BURNER OPERA TION

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 CO
pressure if required to bring the flue gas CO
natural gas, 10.75–11.25% for LP. This noise may be objectionable

reading, adjust gas valve manifold

2

to 9–9.5% level for

2

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.

GAS FAILS T O SHUT OFF

Check for defective gas valve or thermostat. If operation is
incorrect, replace.

REPLACEMENT P ARTS

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.

34

Model BTH Limited Warranty

A. O. Smith Corporation, the warrantor, extends the following LIMITED WARRANTY to the owner of this water heater.

1. THE TANK
If the glass-lined tank in this water heater shall prove upon examination by the warrantor to have leaked due to natural corrosion from potable water
therein, during the first THREE years after initial installation, the warrantor will supply a replacement t ank 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.

2. ALL OTHER PARTS

If within ONE year after initial installation of this water heater, any part or portion shall prove upon examination by the warrantor to be defective in
material or workmanship, the warrantor will repair or replace such part or portion at its option.

3. CONDITIONS AND EXCEPTIONS

This warranty shall apply only when the water heater is installed in accordance with local plumbing and building codes, ordinances and regulations,
the printed instructions provided with it and good industry practices. In addition, a temperature and pressure relief valve, certified by 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 boiler, 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.

4. SERVICE AND REP AIR EXPENSES

5. LIMITATIONS ON IMPLIED WARRANTIES

6. CLAIM PROCEDURE

7. DISCLAIMERS

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____________________

The relief valve installed on the heater is not an acceptable method.

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.
Implied warranties, including the warranty of merchantability imposed on the sale of this heater under state law are limited to one (1) year duration

forthe 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.

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 A. O. Smith Enterprises Ltd.
500 Tennessee Waltz Parkway P. O. Box, 310 - 768 Erie Street
Ashland City, TN 37015 Stratford (Ontario) N5A 6T3
Telephone: [phone] Telephone: [phone]

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.

NO OTHER EXPRESS WARRANTY HAS BEEN OR WILL BE MADE IN BEHALF OF THE WARRANTOR WITH RESPECT TO THE
MERCHANTABILITY OF THE HEA TER OR THE INSTALLA TION, OPERA TION, REPAIR OR REPLACEMENT OF THE WA TER 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 WARRANTY AND KEEP FOR FUTURE REFERENCE.

35

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