A.O. Smith DB/DW-720-1810 User manual

1
WITH ELECTRONIC INTERMITTENT PILOT IGNITION AND
INSTALLATIONS
WARNING: If the information in this manual
isnotfollowedexactly, a fire or explosion may
result causing property damage, personal
injury or loss of life.
— Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
— WHAT TO DO IF YOU SMELL GAS
·Do not try to light any appliance.
·Do not touch any electrical switch;
do not use any phone in your
building.
·Immediately call your gas supplier
from a neighbor’s phone. Follow
the gas supplier’s instructions.
·If you cannot reach your gas
supplier, call the fire department.
— Installation and service must be
performed by a qualified installer,
service agency or the gas supplier.
PRINTED IN U.S.A. 2221 0302
CAUTION
TEXT PRINTED OR OUTLINED IN RED CONTAINS
INFORMATION RELATIVE TO YOUR SAFETY. PLEASE
READ THOROUGHLY BEFORE INSTALLING AND
USING THIS APPLIANCE.
PART NO. 211680-000 REV. 00
SUPERSEDES PART NO. 200311-000 REV. 4 & 210265-000 REV. 0
Built tough with maximum efficiency
TM
A DIVISION OF A.O.SMITH CORPORATION
EL PASO, TX McBEE, SC RENTON, WA
STRATFORD, ONTARIO
VELDHOVEN, THE NETHERLANDS
www.hotwater.com
PLACE THESE INSTRUCTIONS ADJACENT TO BOILER AND
NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.
MODELS DB/DW-720-1810
NATURAL GAS-FIRED COMMERCIAL CROSS FLOW COPPER BOILERS
FOR HYDRONIC HEATING AND HOT WATER SUPPLY
•INSTALLATION •OPERATION •MAINTENANCE •LIMITED WARRANTY

2
FOREWORD
CAUTION
TEXT PRINTED OR OUTLINED IN RED CONTAINS
INFORMATION RELATIVE TO YOUR SAFETY. PLEASE READ
THOROUGHLY BEFORE USING APPLIANCE.
Detailed installation diagrams are in this manual. These diagrams
will serve to provide the installer with a reference for the materials
and method of piping suggested. IT IS NECESSARY THAT ALL
WATER AND GAS PIPING AND THE ELECTRICAL WIRING BE
INSTALLED AND CONNECTED AS SHOWN IN THE DIAGRAMS.
CHECK THE DIAGRAMS THOROUGHLY BEFORE STARTING
INSTALLATION TO AVOID POSSIBLE ERRORS AND TO
MINIMIZE TIME AND MATERIALS COST.
This design complies with the latest edition of the ANSI Z21.13
CSA 4.9 low-pressure boiler.
Particular attention should be given to the installation of
thermometers at the locations indicated in the diagrams as these
are necessary for checking the operation of the boiler.
MAKE SURE THE GAS ON WHICH THE BOILER WILL OPERATE
ISTHESAMEASTHATSPECIFIEDONTHEUNITRATING PLATE.
The boiler installation must conform to these instructions and the
requirements of the local authority having jurisdiction.
Where required by the authority having jurisdiction, the installation
must conform to the Standard for Controls and Safety Devices for
Automatically Fired Boilers, ANSI/ASME CSD-1.
In the absence of local code requirements, the boiler installation
must conform to the most current National Fuel Gas Code, ANSI
Z223.1 and/or CAN/CSA-B149.1-00 installation codes.
These manuals can be purchased from the CSA International,
8501 East Pleasant Valley Road, Cleveland, OH 44131 or 178
Rexdale Boulevard, Toronto, Ontario Canada, M9W 1R3.
REPLACEMENT PARTS
Replacement parts may be ordered through A. O. Smith dealers,
authorized servicers or distributors. Refer to the Yellow Pages for
where to call or contact (in United States) the A.O. Smith Water
Products Company, 5621 West 115th Street, Alsip, IL 60803,
1-800-433-2545 or (in Canada) A.O. Smith Enterprises Ltd., 768
Erie Street, Stratford, Ontario, Canada N5A 6T3, 800-265-8520.
When ordering parts be sure to state the quantity, part number and
description of the item including the complete model and serial
number as it appears on the product. Refer to the parts lists for
more information.
For Technical Assistance call A.O. Smith Technical Information
Center at 1-800-527-1953.
WARNING
THE INLET/OUTLET WATER MANIFOLD ON YOUR A. O. SMITH
UNIT INCORPORATES AN “O RING" WATER SEAL ASSEMBLY.
THE MANIFOLD IS NOT DESIGNED TOSUPPORT THE WEIGHT
OF THE WATER PIPING SYSTEM. AS ON ALL BOILER
INSTALLATIONS,SPECIALCAREMUSTBETAKEN TO ENSURE
PROPER SUPPORT.
WARNING
UNDER NO CIRCUMSTANCES SHOULD THE EQUIPMENT
ROOM WHERE THE BOILER IS INSTALLED EVER BE UNDER
NEGATIVE PRESSURE. PARTICULAR CARE MUST BE TAKEN
WHEN EXHAUST FANS, COMPRESSORS, AIR HANDLING
EQUIPMENT, ETC., MAY INTERFERE WITH THE COMBUSTION
AND VENTILATION AIR SUPPLIES OF THIS BOILER.
Page
FOREWORD................................................................................ 2
REPLACEMENTPARTS .............................................................. 2-3
ROUGH-INDIMENSIONS/CAPACITIES ...................................... 3-4
InstallationClearances.............................................................. 3
Levelling ................................................................................... 3
FEATURES................................................................................... 5
SafetyReliefValves.................................................................. 5
ElectronicIntermittent PIlotIgnitionControl .............................. 5
ManualReset HighTemperature SafetyLimitControl ............... 5
AutomaticReset HighTemperature Control .............................. 6
ThermalBalancer ..................................................................... 6
SafetyFlowSwitch ................................................................... 6
INSTALLATIONINSTRUCTIONS ................................................. 7
RequiredAbility ........................................................................ 7
Location ................................................................................... 7
AirRequirements ..................................................................... 7-8
Ventingthe Boiler ..................................................................... 8-9
GasConnections...................................................................... 9
Purging .................................................................................... 10-11
HighAltitude Installations ......................................................... 11
WiringConnections .................................................................. 11-12
ServicingWiringAnd/Or Control .............................................. 12
SYSTEMEQUIPMENT INSTALLATION ....................................... 12
Water Supply Line.................................................................... 12
ExpansionTank ........................................................................ 12
VentValves .............................................................................. 12
SystemHeaders ...................................................................... 12
CoolingPiping .......................................................................... 12
SafetyFlowSwitch ................................................................... 12-13
CirculatingPump...................................................................... 13-14
LowWater Cutoff ..................................................................... 14
TankTemperatureControl ........................................................ 14
SYSTEMINSTALLATION ............................................................. 14
ConventionalSpaceHeatingInstallation ................................... 14-15
Installation AsBoiler Replacement ............................................ 15-17
Linear-Temp Space HeatingApplications .................................. 17
Linear-TempSpaceHeatingInstallations .................................. 17-20
WiringandSchematic Diagrams .............................................. 21-26
HOTWATERSUPPLYAPPLICATIONS ....................................... 27-32
Water LineConnections ........................................................... 27
Hard WaterConditions ............................................................. 27
START-UP ANDOPERATINGINSTRUCTIONS .......................... 32
LIGHTINGAND OPERATINGINSTRUCTIONS ........................... 33
InternalContaminants .............................................................. 34
Precautions .............................................................................. 34
CheckingandAdjusting theInput............................................. 34
PilotBurner .............................................................................. 34
MainBurner ............................................................................. 34-35
PRE-TROUBLESHOOTING ......................................................... 35
TROUBLESHOOTING.................................................................. 35-38
GENERALMAINTENANCE.......................................................... 39
ReliefValve .............................................................................. 39
VentingMaintenance ................................................................ 39
HeatExchanger PreventiveMaintenance.................................. 39
Deliming ................................................................................... 39-40
DelimingSolvents..................................................................... 40
RemovingLight DepositsofScale ............................................ 40
Removalof anExistingBoiler FromA CommonVenting
System ................................................................................ 40
LIMITEDWARRANTY .................................................................. 41
CONTENTS Page

3
WARNING
AN AMPLE SUPPLY OF AIR MUST BE PROVIDED
FOR PROPER COMBUSTION AND VENTILATION.
Minimum Clearances To Combustibles
Water Blank
Top Side Side Rear Vent Front
AllModels 12" (305mm) 18"(457mm) 6" (155mm) 6"(155mm) 6"(155mm) Alcove
CAUTION
Labelallwirespriortodisconnection when servicing controls. Wiring
errors can cause improper and dangerous operation.
"Verify proper operation after servicing."
ROUGH-IN DIMENSIONS/
CAPACITIES
INSTALLATION CLEARANCES
These boilers are approved for installation on combustible flooring
in an alcove with minimum clearance to combustibles See chart
below.
Two inch clearance is allowable from combustible construction for
hot water pipes.
Sufficient clearance should be provided at one end of the boiler to
permit access to heat exchanger tubes for cleaning. Maximum
operating water supply pressure 160 psi. Gas supply pressure:
13.8" w.c. max., 5.5" w.c. min.
Sufficient area should be provided at the front and sides of the unit
for proper servicing. Clearances of 48" in front and 24" on sides is
recommended. In a utility room installation, the door shall be wide
enough to allow the boiler to enter or to permit the replacement of
another appliance.
LEVELLING
Each unit should be checked after installation to be certain that it is
level.
TABLE 1, ROUGH-IN DIMENSIONS
Models
Dimensions inches mm inches mm inches mm inches mm inches mm inches mm inches mm inches mm inches mm
A46 1/2 1181 52 1/5 1326 57 3/4 1467 52 7/8 1343 58 1/2 1486 64 1/2 1638 69 1/2 1765 75 1905 82 1/2 2096
B29 5/8 752 29 5/8 752 29 5/8 752 32 3/4 832 32 3/4 832 32 3/4 832 34 864 34 864 34 864
C54 3/4 1391 54 3/4 1391 54 3/4 1391 58 1473 58 1473 58 1473 60 1/2 1537 60 1/2 1537 60 1/2 1537
D1 1/4 NPT 1 1/4 NPT 1 1/4 NPT 1 1/4 NPT 1 1/2 NPT 1 1/2 NPT 1 1/2 NPT 2 NPT 2 NPT
E7 3/4 197 7 3/4 197 7 3/4 197 7 1/2 191 7 1/2 191 7 1/2 191 7 1/2 191 7 1/2 191 7 1/2 191
F15 1/2 394 15 1/2 394 15 1/2 394 18 1/2 470 18 1/2 470 18 1/2 470 18 1/2 470 18 1/2 470 18 1/2 470
G17 1/4 438 17 1/4 438 17 1/4 438 18 9/16 471 18 9/16 471 18 9/16 471 19 1/8 486 19 1/8 486 19 1/8 486
H4 1/4 108 4 1/4 108 4 1/4 108 4 102 4 102 4 102 4 1/2 114 4 1/2 114 4 1/2 114
J2 NPT 2 NPT 2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT
K2 NPT 2 NPT 2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT 2 1/2 NPT
L1 NPT 1 NPT 1 NPT 1 1/4 NPT 1 1/4 NPT 1 1/4 NPT 1 1/4 NPT 1 1/4 NPT 1 1/4 NPT
M12 305 14 356 14 356 16 406 16 406 18 457 18 457 18 457 20 508
N15 1/2 394 16 1/2 419 16 1/2 419 17 1/4 438 17 1/4 438 17 1/4 438 13 3/4 349 13 3/4 349 13 3/4 349
W32 1/8 816 31 1/8 791 32 1/8 816 30 15/16 786 30 15/16 786 30 15/16 786 31 787 31 787 31 787
Approx.
Shipping
Weight. 780 lbs 354 Kg. 950 lbs 431 Kg 950 lbs 431 Kg 1000 lbs 454 Kg 1075 lbs 488 Kg. 1100 lbs 499 Kg 1125 lbs 510 Kg 1150 lbs 522 Kg 1250 lbs 567 Kg
DW-1810DW-1210 DW-1350 DW-1480 DW-1610DW-720 DW-840 DW-960 DW-1080

4
WARNING
Your Dura-Max boiler is not designed to operate with a boiler inlet water temperature of less than
100°F (38°C). Colder inlet water temperatures will result in significant condensation developing on
the heat exchanger. This situation can cause a corrosive environment for the heat exchanger,
burners and venting resulting in premature damage, which could result in serious personal injury or
death.
For systems that use large volumes of cold water or system utilizing heavy water draws (Cer-Temp),
condensation can be prevented by using a by-pass loop. See page 16.
TABLE 3, RECOVERY CAPACITIES U.S. Gallons/Hr and Litres/Hr at TEMPERATURE RISE INDICATED
F 20F 30F 36F 40F 50F 54F 60F 70F 72F 80F 90F 100F 108F 110F 120F 126F 130F 140F
MODEL BTUH KW C 11.1C 16.6C 20C 22.2C 27.7C 30C 33.3C 38.8C 40C 44.4C 50C 55.5C 60C 61.1C 66.6C 70C 72.2C 77.7C
720,000 GPH 3,535 2,356 1,964 1,767 1,414 1,309 1,178 1,010 982 884 785 707 655 643 589 561 544 505
211 LPH 13,379 8,920 7,433 6,690 5,352 4,955 4,460 3,823 3,716 3,345 2,973 2,676 2,478 2,433 2,230 2,124 2,058 1,911
840,000 GPH 4,124 2,749 2,291 2,062 1,649 1,527 1,375 1,178 1,145 1,031 916 825 764 750 687 655 634 589
246 LPH 15,609 10,406 8,672 7,805 6,244 5,781 5,203 4,460 4,336 3,902 3,469 3,122 2,891 2,838 2,602 2,478 2,401 2,230
960,000 GPH 4,713 3,142 2,618 2,356 1,885 1,745 1,571 1,346 1,309 1,178 1,047 943 873 857 785 748 725 673
281 LPH 17,839 11,893 9,911 8,920 7,136 6,607 5,946 5,097 4,955 4,460 3,964 3,568 3,304 3,243 2,973 2,832 2,744 2,548
1,080,000 GPH 5,367 3,578 2,982 2,684 2,147 1,988 1,789 1,534 1,491 1,342 1,193 1,073 994 976 895 852 826 767
316 LPH 20,317 13,545 11,287 10,158 8,127 7,525 6,772 5,805 5,644 5,079 4,515 4,063 3,762 3,694 3,386 3,225 3,126 2,902
1,210,000 GPH 6,013 4,009 3,341 3,007 2,405 2,227 2,004 1,718 1,670 1,503 1,336 1,203 1,114 1,093 1,002 954 925 859
354 LPH 22,762 15,175 12,646 11,381 9,105 8,430 7,587 6,504 6,323 5,691 5,058 4,552 4,215 4,139 3,794 3,613 3,502 3,252
1,350,000 GPH 6,709 4,473 3,727 3,355 2,684 2,485 2,236 1,917 1,864 1,677 1,491 1,342 1,242 1,220 1,118 1,065 1,032 958
395 LPH 25,396 16,931 14,109 12,698 10,158 9,406 8,465 7,256 7,054 6,349 5,644 5,079 4,703 4,617 4,233 4,031 3,907 3,628
1,480,000 GPH 7,176 4,784 3,987 3,588 2,870 2,658 2,392 2,050 1,993 1,794 1,595 1,435 1,329 1,305 1,196 1,139 1,104 1,025
433 LPH 27,162 18,108 15,090 13,581 10,865 10,060 9,054 7,761 7,545 6,791 6,036 5,432 5,030 4,939 4,527 4,311 4,179 3,880
1,610,000 GPH 7,806 5,204 4,337 3,903 3,122 2,891 2,602 2,230 2,168 1,952 1,735 1,561 1,446 1,419 1,301 1,239 1,201 1,115
472 LPH 29,548 19,699 16,416 14,774 11,819 10,944 9,849 8,442 8,208 7,387 6,566 5,910 5,472 5,372 4,925 4,690 4,546 4,221
1,810,000 GPH 8,776 5,851 4,875 4,388 3,510 3,250 2,925 2,507 2,438 2,194 1,950 1,755 1,625 1,596 1,463 1,393 1,350 1,254
530 LPH 33,219 22,146 18,455 16,609 13,288 12,303 11,073 9,491 9,227 8,305 7,382 6,644 6,152 6,040 5,536 5,273 5,111 4,746
DB/DW-840
DB/DW-1610
DB/DW-1810
DB/DW-1350
DB/DW-1480
INPUT
DB/DW-720
DB/DW-1210
DB/DW-960
DB/DW-1080
TABLE 2, PRESSURE DROP
FC
GPM LPM ft M
20 11.1 59 223 3.5 1.1
30 16.7 39 149 1.7 0.5
40 22.2 29 111 1.0 0.3
20 11.1 69 260 4.8 1.5
30 16.7 46 173 2.1 0.6
40 22.2 34 130 1.5 0.5
20 11.1 79 297 6.8 2.1
30 16.7 52 198 3.3 1.0
40 22.2 39 149 1.9 0.6
20 11.1 89 339 4.5 1.4
30 16.7 60 226 2.1 0.6
40 22.2 45 169 1.4 0.4
20 11.1 100 379 5.3 1.6
30 16.7 67 253 2.7 0.8
40 22.2 50 190 1.6 0.5
20 11.1 112 423 6.8 2.1
30 16.7 75 282 3.2 1.0
40 22.2 56 212 1.8 0.5
20 11.1 120 453 7.9 2.4
30 16.7 80 302 3.9 1.2
40 22.2 60 226 2.1 0.6
20 11.1 130 492 9.5 2.9
30 16.7 87 328 5.0 1.5
40 22.2 65 246 3.0 0.9
20 11.1 146 554 12.0 3.7
30 16.7 98 369 6.2 1.9
40 22.2 73 277 3.9 1.2
DW-720
DW-1210
Model Temp Rise
DW-1810
DW-1610
HdLoss*
DW-1480
DW-1080
DW-960
DW-840
Flow Rate
DW-1350

5
FEATURES
IMPORTANT
Only qualified personnel shall perform the initial firing of the heater.
At this time the user should not hesitate to ask the individual any
questions regarding the operation and maintenance of the unit.
Lighting and Operating instructions are included at the rear of this
manual. By using this checklist the user may be able to make
minor operational adjustments and save unnecessary service calls.
However, the user should not attempt repairs which are not listed
under the USER column.
SAFETY RELIEF VALVES
Your local code authority may have other specific relief valve
requirements not covered below.
WARNING
THE PURPOSE OF A SAFETY RELIEF VALVE IS TO AVOID
EXCESSIVE PRESSURE WHICH MAY CAUSE TANK
EXPLOSION, SYSTEM OR BOILER DAMAGE.
TO AVOID WATER DAMAGE A DRAIN LINE MUST BE
CONNECTED TO A SAFETY RELIEF VALVE TO DIRECT
DISCHARGE TO A SAFE LOCATION. A DRAIN LINE MUST NOT
BE REDUCED FROM THE SIZE OF THE VALVE OUTLET AND IT
MUSTNOTCONTAIN ANY VALVESBETWEENTHEBOILERAND
THE RELIEF VALVE OR THE RELIEF VALVE AND THE DRAIN
EXIT. IN ADDITION, THERE SHOULD NOT BE ANY
RESTRICTIONS IN A DRAIN LINE NOR SHOULD IT BE ROUTED
THROUGH AREAS WHERE FREEZING CONDITIONS MIGHT
OCCUR. DO NOT THREAD OR CAP THE DRAIN LINE EXIT.
RESTRICTINGOR BLOCKING A DRAIN LINE WILL DEFEAT THE
PURPOSE OF THE RELIEF VALVE AND MAY CREATE AN
UNSAFE CONDITION. INSTALL A DRAIN LINE WITH A
DOWNWARD SLOPE SUCH THAT IT NATURALLY DRAINS
ITSELF.
If any safety relief valve is replaced, the replacement valve must
comply with the latest version of the ASME Boiler and Pressure
Vessel Code, Section IV (“HEATING BOILERS”). Select a relief
valve with a discharge rating NOT less than the boiler input, and a
setpressureNOTexceeding the working pressureofanycomponent
in the system.
An ASME rated temperature and pressure relief valve must be
installed on each and every water storage tank in a hot water supply
system.
Thestoragetanktemperatureandpressurereliefvalvemustcomply
withtheapplicableconstructionprovisionsoftheStandard for Relief
Valves and Automatic Gas Shutoff Devices for Hot Water Supply
Systems, ANSI Z21 or CAN/CSA-B149.1 (latest edition). The valve
must be of the automatic reset type and not embody a single-use
type fusible plug, cartridge or linkage.
ELECTRONIC INTERMITTENT PILOT
IGNITION CONTROL
ALL MODELS - The solid state ignition control, fig. 2, ignites the
pilot burner gas by creating a spark at the pilot assembly. Pilot gas
is ignited and burns during each running cycle. The main burner
and pilot gases are cut off during the “OFF”cycle. Pilot gas ignition
is proven by the pilot sensor. Main burner ignition will not occur if
the pilot sensor does not first sense pilot ignition.
FIGURE 2
On natural gas models the igniter control continues to operate
(creating a spark) until the pilot burner is ignited or the ignition
system shuts down. Shut down occurs automatically if the pilot
burner does not ignite within 15 seconds. The unit then waits for
(5) minutes and retries ignition (standard models).
Theelectronicintermittentpilotignitioncontrolandthe100%lockout
control are non-adjustable devices.
(See troubleshooting steps on page 40). If pilot is not lit and sensed
within the flame establishing timing for each module, the appliance
will shut down.
MANUAL RESET HIGH TEMPERATURE
SAFETY LIMIT CONTROL
This device senses water temperature in the boiler. When water
temperature exceeds dial setting, power to main gas valve is
interrupted and the boiler is shut down.
HOTWATER SUPPLY-Manualreset-factorysetat210°F(100°C).
Water temperature must drop at least 20°F (11°C) before reset is
possible.
HYDRONICHEATING-Manualreset- factory set at 250°F(121°C).
Water temperature must drop at least 20°F (11°C) before reset is
possible.
Singlestageandmodulatingunitsuseacombinedcontrolasshown
in fig. 4.
Dual stage models are equipped with a limit like one shown in
figure 3.

6
AUTOMATIC RESET
HIGH TEMPERATURE LIMIT CONTROL
CAUTION
LIMIT CONTROLS ARE NOT TO BE USED AS THERMOSTATS.
ALL MODELS - This limit is a safety device wired in series with the
ignition system. Set the limit control dial to a minimum of 10°F
(6°C) above the maximum designed system temperature. If the
boiler outlet water temperature should exceed the high limit setting,
the main gas valves will close but the circulator will continue to
operate. Maximum adjustable setting is 240°F (116°C) for boilers
and 200°F (93°C) for hot water supply heaters. The differential is
adjustable from 5°F (3°C) to 45°F.
SINGLESTAGEAND MODULATINGMODELS-Are equipped with
the limit like the one shown in fig. 4.
Gas valves either close or open to full gas input, depending upon
heat requirement.
DUAL STAGE MODELS ONLY - HIGH/LOW OPERATOR
Theseboilersarefactoryequippedwith a (combination) temperature
controller to provide high and low firing rates for smooth operation.
(fig. 5).
The temperature dials should be adjusted to have the HI dial set as
a limit to be 10°F (6°C) above desired boiler temperature. These
boilers are shipped with the HI dial set to 200°F (93°C) with a 15°F
(8°C) differential, the LO dial set to 160°F (71°C) with a 10°F (6°C)
differential.
The heater operation with above set points will be as follows:
1) When heater temperature rises to LO thermostat setting the
main gas valve will close its second stage operator to drop
input to approximately 50% of total input.
2) System conditions will determine if temperature rise at LO
thermostat sensor location will continue to rise until shut-off
by high limit or drop causing heater to go back to full input.
Other system design temperatures will require resetting of the dial.
Total span of temperatures (HI dial cut-off point to LO dial cut-on
point) should not be less than temperature drop of the system.
MODULATING MODELS ONLY
These boilers are factory equipped with a modulating gas valve
that automatically controls the outlet water temperature by
modulating or proportioning the rate of gas thus maintaining a
desired constant outlet water temperature regardless of varying
flow rates.
Set temperature controller for desired outlet water temperature.
(fig. 6).
Adjust the set point for the desired operating temperature by turning
thesetpointadjustingscrewonthefrontofthecaseuntilthedesired
value is reached on the set point indicating dial. The set point is
calibrated to be at the center of the proportioning range, (see the
manufacturers instructions for complete information on testing and
calibrating this control.)
THERMAL BALANCER
This device serves as a pump shutdown delay switch to balance
theboilerwatertemperaturetosystemtemperature before the pump
stops. Overshooting of boiler temperature is prevented and stack
loss after shutdown is minimized.
SAFETY FLOW SWITCH
The safety flow switch is a safety device which must be installed at
the water outlet of the unit to prevent main burner operation in the
event of inadequate water flow through the boiler.
This switch may be mounted in a horizontal pipe line or a vertical
pipe line with upward water flow. Do not install the switch where
the water flow is downward.

7
INSTALLATION INSTRUCTIONS
REQUIRED ABILITY
INSTALLATION OR SERVICE OF THIS BOILER REQUIRES
ABILITY EQUIVALENT TO THAT OF A LICENSED TRADESMAN
IN THE FIELD INVOLVED. PLUMBING, AIR SUPPLY, VENTING,
GAS SUPPLY AND ELECTRICAL WORK ARE REQUIRED.
WARNING
THE INLET/OUTLET WATER MANIFOLD ON YOUR A. O. SMITH
UNIT INCORPORATES AN "O RING" WATER SEAL ASSEMBLY.
THE MANIFOLD IS NOT DESIGNED TOSUPPORT THE WEIGHT
OF THE WATER PIPING SYSTEM. AS ON ALL BOILER
INSTALLATIONS,SPECIALCAREMUSTBETAKEN TO ENSURE
PROPER SUPPORT.
LOCATION
When installing the boiler, consideration must be given to proper
location. Location selected should be as close to the stack or
chimney as practical with adequate air supply and as centralized
with the piping system as possible. This location should also be
such that the gas ignition system components are protected from
water (dripping, spraying, etc.) during appliance operation and
service [circulator replacement, control replacement, etc.].
THE BOILER MUST NOT BE INSTALLED ON CARPETING.
THE BOILER SHOULD NOT BE LOCATED IN AN AREA WHERE
IT WILL BE SUBJECT TO FREEZING.
LOCATE IT NEAR A FLOOR DRAIN. THE BOILER SHOULD BE
LOCATED IN AN AREA WHERE LEAKAGE FROM THE BOILER
OR CONNECTIONS WILL NOT RESULT IN DAMAGE TO THE
ADJACENT AREA OR TO LOWER FLOORS OF THE
STRUCTURE.
WHEN SUCH LOCATIONS CANNOT BE AVOIDED, A SUITABLE
DRAINPANSHOULD BE INSTALLEDUNDERTHEBOILER. Such
pans should be fabricated with sides at least 2-1/2" (64 mm) deep,
with length and width at least 2" (51 mm) greater than the
dimensions of the boiler and must be piped to an adequate drain.
The pan must not restrict combustion air flow.
WARNING
THERE IS A RISK IN USING FUEL BURNING APPLIANCES IN
ROOMS OR AREAS WHERE GASOLINE, OTHER FLAMMABLE
LIQUIDS OR ENGINE DRIVEN EQUIPMENT OR VEHICLES ARE
STORED, OPERATED OR REPAIRED. FLAMMABLE VAPORS
ARE HEAVY AND TRAVEL ALONG THE FLOOR AND MAY BE
IGNITED BY THE IGNITER OR MAIN BURNER FLAMES
CAUSINGFIREOREXPLOSION.SOMELOCALCODES PERMIT
OPERATION OF GAS APPLIANCES IF INSTALLED 18 INCHES
OR MORE ABOVE THE FLOOR. THIS MAY REDUCE THE RISK
IF LOCATION IN SUCH AN AREA CANNOT BE AVOIDED.
FLAMMABLE ITEMS, PRESSURIZED CONTAINERS OR ANY
OTHER POTENTIAL FIRE HAZARDOUS ARTICLES MUST
NEVER BE PLACED ON OR ADJACENT TO THE BOILER.
OPEN CONTAINERS OF FLAMMABLE MATERIAL SHOULD NOT
BE STORED OR USED IN THE SAME ROOM WITH THE BOILER.
If the boiler is installed above the level of heating system terminal
units, a low water cutoff device must be installed in the boiler outlet
at the time of installation.
For installation locations with elevations above 2,000 feet (610 M),
refer to the HIGH ALTITUDE INSTALLATIONS section of this
manual for input reduction procedure.
CHEMICAL VAPOR CORROSION
Heat exchanger corrosion and component failure can be caused
by the heating and breakdown of airborne chemical vapors. 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 corrosive. These materials are corrosive at very low
concentration levels with little or no odor to reveal their presence.
Products of this sort should not be stored near the boiler. Also, air
which is brought in contact with the water boiler should not contain
any of these chemicals. If necessary, uncontaminated air should
be obtained from remote or outside sources.
AIR REQUIREMENTS
WARNING
FOR SAFE OPERATION, AN AMPLE SUPPLY OF AIR MUST BE
PROVIDED FOR PROPER COMBUSTION AND VENTILATION
IN ACCORDANCE WITH SECTION 5.3, AIR FOR COMBUSTION
AND VENTILATION, OF THE NATIONAL FUEL GAS CODE, ANSI
Z223.1 OR 7.2, 7.3 OR 7.4 OF CAN/CSA B149.1-00,
INSTALLATION CODES, OR APPLICABLE PROVISIONS OF THE
LOCAL BUILDING CODES. AN INSUFFICIENT SUPPLY OF AIR
MAY RESULT IN A YELLOW, LUMINOUS BURNER FLAME,
CARBONING OR SOOTING OF THE FINNED HEAT
EXCHANGER,ORCREATE A RISK OF ASPHYXIATION. DONOT
OBSTRUCT THE FLOW OF COMBUSTION AND VENTILATION
AIR.
UNCONFINED SPACE
In buildings of conventional frame, brick or stone construction,
unconfined spaces may provide adequate air for combustion, and
draft hood dilution.
If the unconfined space is within a building of tight construction
(buildingsusingthe following construction; weather stripping, heavy
insulation, caulking, vapor barrier, etc.), air for combustion,
ventilation, and draft hood dilution must be obtained from outdoors
or spaces freely communicating with the outdoors. The installation
instructionsforconfinedspacesintightlyconstructedbuildingsmust
be followed to ensure adequate air supply.
CONFINED SPACE
(a) U. S. INSTALLATIONS
When drawing combustion and dilution air from inside a
conventionally constructed building to a confined space, such a
space shall be provided with two permanent openings, ONE IN OR
WITHIN 12 INCHES (30 CM) OF THE ENCLOSURE TOP AND
ONE IN OR WITHIN 12 INCHES (30 CM) OF THE ENCLOSURE
BOTTOM. Each opening shall have a free area of at least one
square inch per 1000 Btuh (2,208 mm2of per kw) of the total input
of all appliances in the enclosure, but not less than 100 square
inches (645 cm2).

8
If the confined space is within a building of tight construction, air for
combustion, ventilation, and draft hood dilution must be obtained
from outdoors. When directly communicating with the outdoors or
communicating with the outdoors through vertical ducts, two
permanent openings, located in the aforementioned manner, shall
be provided. Each opening shall have a free area of not less than
one square inch per 4000 Btu/hr (551 mm2per kw) of the total
input of all appliances in the enclosure. If horizontal ducts are
used, each opening shall have a free area of not less than one
square inch per 2000 Btu/hr (1101 mm2per kw)of the total input of
all appliances in the enclosure.
(B) CANADIAN INSTALLATIONS
Ventilation of the space occupied by the boiler(s) shall be provided
by an opening for ventilation air at the highest practical point
communicating with outdoors. The total cross- sectional area shall
be at least 10% of the area of the combustion air opening but in no
case shall the cross-sectional area be less than 10 square inches
(6500 mm²).
In addition to the above, there shall be permanent air supply
opening(s) having a cross-sectional area of not less than 1 square
inch per 7,000 BTUH (315 mm²/kw) up to and including 1,000,000
BTUH plus 1 square inch per 14,000 BTU (158 mm2/kw) in excess
of 1,000,000 BTUH. This opening(s) shall be located at, or ducted
to, a point neither more than 18" (450 mm) nor less than 6 inches
(150 mm) above the floor level.
Where power vented equipment is used in the same room as the
boiler, sufficient air openings must be supplied.
UNDERSIZED OPENINGS MAY RESULT IN INSUFFICIENT AIR
FOR COMBUSTION.
Where an exhaust fan is installed in the same room with a boiler,
sufficient openings for air must be provided in the walls.
UNDERSIZED OPENINGS WILL CAUSE AIR TO BE DRAWN
INTO THE ROOM THROUGH THE CHIMNEY, CAUSING POOR
COMBUSTION. SOOTING MAY RESULT WITH AN INCREASED
RISK OF ASPHYXIATION.
VENTING THE BOILER
WARNING
THE INSTRUCTIONS IN THIS SECTION ON VENTING THE
BOILER MUST BE FOLLOWED TO AVOID CHOKED
COMBUSTION OR RECIRCULATION OF FLUE GASES. SUCH
CONDITIONS CAUSE SOOTING OR RISKS OF FIRE AND
ASPHYXIATION.
SINGLE WALL OR TYPE B VENTING MAY BE USED WITH
THESE BOILERS. ALL LOCAL UTILITY, STATE/ PROVINCIAL,
REGULATIONS ON VENTING MUST BE FOLLOWED.
VENT SIZING, INSTALLATION AND TERMINATION SHALL BE
IN ACCORDANCE WITH PART 7, VENTING OF EQUIPMENT,
OFTHENATIONAL FUEL GAS CODE, ANSIZ223.1,ORSECTION
7, VENTING SYSTEMS AND AIR SUPPLY FOR APPLIANCES,
OF THE CAN/CSA B149, INSTALLATION CODES, OR
APPLICABLE PROVISIONS OF THE LOCAL BUILDING CODES.
1. DRAFT HOOD
The integral draft hood, louvers or cabinetry must not be altered.
Provision must be made if the boiler is installed in confined space
or a small boiler room to accommodate draft hood spillage and
avoid risks described above. The upper air opening called for in
theAIRREQUIREMENTSsection of this manual is for this purpose.
2. VENT CONNECTION
The minimum distance from adjacent public walkways, adjacent
buildings, openable windows and building openings shall not be
less than those values specified in the National Fuel Gas Code,
ANSI Z223.1 and/or CAN/CSA B149.1-00, Installation Codes:
Stack or chimney must be a minimum height of 12" (305 mm)
above the annual snow fall to prevent blockage.
Building materials must not come in contact with combustion
products from stack or chimney, due to the degrading properties of
flue products.
Materials may be protected from flue products by use of metal or
copper sheeting.
Flue products must have a minimum clearance of 4 feet (1.22 m)
horizontally from, and in no case above or below, unless a 4-foot
(1.22 m) horizontal distance is maintained, from electric meters,
gas meters, regulators and relief equipment.
The Canadian B149.1-00, Installation Code specifies a 6 foot
horizontal vent terminal clearance to gas and electric meters and
relief devices (this clearance is specified as 4 feet in the U.S. under
the National Fuel Gas Code, ANSI/Z223.1). Therefore instruction
provision 1.34.1-b19(d), which specifies compliance with the 4 foot
clearance,asappliesintheU.S.only,andtheB149.1-00Installation
Code applies in Canada.
Vent connections must be made to an adequate stack or chimney
and shall be in accordance with Part 7, Venting of Equipment, of
the National Fuel Gas Code, ANSI Z223.1, or Section 7, Venting
Systems and Air Supply for Appliances, of the CAN/CSA-B149.1-
00, Installation Codes, or applicable provisions of the local building
codes. Size and install proper size vent pipe. Do not reduce pipe
size to less than that of the draft hood outlet unless permitted by
local code.
Horizontal runs of vent pipe shall be securely supported by
adequately placed (approximately every 4 feet [1.2 m]),
noncombustible hangers suitable for the weight and design of the
materials employed to prevent sagging and to maintain a minimum
upward slope of 1/4" per foot (21mm/m) from the boiler to the vent
terminals. Dampers or other obstructions must not be installed in
the vent. Be sure that the vent connector does not extend beyond
the inside wall of the chimney.
Where a continuous or intermittent back draft is found to exist the
cause must be determined and corrected. A special vent cap may
be required. If the back draft cannot be corrected by the normal
methods or if a suitable draft cannot be obtained, a blower type
flue gas exhauster may be employed to ensure proper venting and
correct combustion (where permitted by local code). Contact your
A. O. Smith dealer for power vent instructions.

9
WARNING
FAILURE TO CORRECT BACK DRAFTS MAY CAUSE AIR
CONTAMINATION AND UNSAFE CONDITIONS.
Vent connectors serving appliances vented by natural draft shall
not be connected into any portion of mechanical draft systems
operating under positive pressure.
3. CONNECTING BOILER TO A COMMON VENT
Do not connect the boiler to a common vent or chimney with solid
fuel burning equipment. This practice is prohibited by most local
building codes as is the practice of venting gas fired equipment to
the duct work of ventilation systems.
Where a separate vent connection is not available and the vent
pipe from the boiler must be connected to a common vent with an
oil burning furnace, the vent pipe should enter the common vent or
chimney at a point ABOVE the flue pipe from the oil furnace.
UL/ULC listed doublewall type B-1 gas vents, through 24" (610
mm) diameter, can be installed in heated and unheated areas and
can pass through floors, ceilings, partitions, walls and roofs,
provided the required clearance is observed.
At the time of removal of an existing boiler, the following steps
shall be performed with each appliance remaining connected to
the common venting system. Perform these steps while the other
appliances remaining connected to the common venting system
are not in operation.
—Seal any unused openings in the common venting system.
—Visually inspect the venting system for proper size and
horizontal pitch and determine there is not blockage or
restriction, leakage, corrosion and other deficiencies which
could cause an unsafe condition.
—Insofar as is practical, close all building doors and windows
and all doors between the space in which the appliances
remaining connected to the common venting system are
locatedandotherspacesofthebuilding. Turnonclothesdryers
and any appliance not connected to the common venting
system. Turn on any exhaust fans, such as range hoods and
bathroomexhaustfans,sotheywilloperate at maximum speed.
Close fireplace dampers.
—Place in operation the appliance being inspected. Follow the
lighting instructions. Adjust thermostat so appliance will
operate continuously.
—Test for spillage at the draft hood relief opening after five
minutes of main burner operation. Use the flame of a match
or candle, or smoke from a cigarette, cigar or pipe.
—After it has been determined that each appliance remaining
connected to the common venting system properly vents when
tested as outlined above, return doors, windows, exhaust fans,
fireplace dampers and any other gas burning appliance to their
previous conditions of use.
GAS CONNECTIONS
WARNING
THIS BOILER IS NOT INTENDED TO OPERATE AT GAS SUPPLY
PRESSURE OTHER THAN SHOWN ON THE RATING PLATE.
EXPOSURE TO HIGHER GAS SUPPLY PRESSURE MAY CAUSE
DAMAGE TO GAS VALVES WHICH CAN RESULT IN FIRE OR
EXPLOSION. IF OVERPRESSURE HAS OCCURRED SUCH AS
THROUGH IMPROPER TESTING OF GAS LINES OR
EMERGENCY MALFUNCTION OF THE SUPPLY SYSTEM, THE
GAS VALVES MUST BE CHECKED FOR SAFE OPERATION.
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 BOILER. VENT
BLOCKAGE MAY OCCUR DURING ICE BUILD-UP OR SNOW
STORMS.
WHEN LOCAL CODES REQUIRE A MAIN MANUAL SHUTOFF
VALVE OUTSIDE THE BOILER JACKET, A SUITABLE MAIN
MANUAL SHUTOFF VALVE MUST BE INSTALLED IN A
LOCATION COMPLYING WITH THOSE CODES.
IT IS IMPORTANT TO GUARD AGAINST GAS VALVE FOULING
FROM CONTAMINANTS IN THE GAS WAYS. SUCH FOULING
MAY CAUSE IMPROPER OPERATION, FIRE OR EXPLOSION.
IF COPPER SUPPLY LINES ARE USED THEY MUST BE
APPROVED FOR GAS SERVICE.
BEFORE ATTACHING THE GAS LINE BE SURE THAT ALL GAS
PIPE IS CLEAN ON THE INSIDE.
TO TRAP ANY DIRT OR FOREIGN MATERIAL IN THE GAS
SUPPLY LINE, A DIRT LEG (SOMETIMES CALLED DRIP LEG
OR SEDIMENT TRAP) UPSTREAM OF THE GAS CONTROLS,
MUST BE INCORPORATED IN THE PIPING. The dirt leg must be
readily accessible and not subject to freezing conditions. INSTALL
IN ACCORDANCE WITH RECOMMENDATIONS OF SERVING
GAS SUPPLIERS. REFER TO NATIONALFUEL GAS CODE, ANSI
Z223.1 AND/OR CAN/CSA-B149.1-00.
To prevent damage, care must be taken not to apply too much
torque when attaching gas supply pipe to gas valve gas inlet.
Fittings and unions in the gas line must be metal to metal type.
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.
The boiler and its individual shutoff valve must be disconnected
from the gas supply piping system during any pressure testing of
that system at test pressures in excess of 1/2 psi (3.5 kPa).
The boiler must be isolated from the gas supply piping system by
closing its individual manual shutoff valve during any pressure
testing of the gas supply piping systems at test pressures equal to
or less than 1/2 psi (3.5 kPa).
Theboileranditsgasconnection must be leak tested before placing
the boiler in operation.
Provisions for vent, bleed and gas relief lines (when applicable).

10
TABLE 5
Multipliers To Be Used With Table 1 When Applying The
Gravity Factor To Other Than .60 Specific Gravity
Specific Specific
Gravity Multiplier Gravity Multiplier
.35 1.31 1.00 .78
.40 1.23 1.10 .74
.45 1.16 1.20 .71
.50 1.10 1.30 .68
.55 1.04 1.40 .66
*.60 (Nat.) 1.00 *1.50 (Prop.) .63
.65 .96 1.60 .61
.70 .93 1.70 .59
.75 .90 1.80 .58
.80 .87 1.90 .56
.85 .84 *2.00(Butane) .55
.90 .82 2.10 .54
*Usethese correctionfactors ifexact specificgravity ofthe gasis notknown.
PURGING
Gas line purging is required with new piping or systems in which
air has entered.
CAUTION
PURGING SHOULD BE PERFORMED BY PERSONS
EXPERIENCEDINTHISTYPEOFGASSERVICETOAVOIDRISK
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
SOURCESOFIGNITIONMUSTBE INACTIVATEDORREMOVED.
BEFORE PLACING THE BOILER IN OPERATION, CHECK FOR
GAS LEAKAGE. Use soap and water solution or other material
acceptable for the purpose in locating gas leaks. DO NOT USE
MATCHES, CANDLES, FLAME OR OTHER SOURCES OF
IGNITION FOR THIS PURPOSE.
1. CORRECT GAS
Make sure the gas on which the boiler will operate is the same as
that specified on the boiler rating plate. Do not install the boiler if
equipped for a different type gas, consult your gas supplier. These
boilers are designed to operate on natural gas only.
2A. SIZING GAS SUPPLY LINE (For single boiler installations
and for installations of multiples of two or three of same size
boilers).
Use table 1, which is taken from ANSI booklet Z223.1, NATIONAL
FUEL GAS CODE, and/or CAN/CSA-B149.1-00 to size iron pipe
or equivalent gas supply line. Table 4 is based on a pressure drop
of 0.3 inches of water and a specific gravity of 0.60 which is
approximately for natural gas. (LP gas has an S.G. of about 1.53).
If the service pressure is five inches water column or less, use one
pipesizelargerthan specified in table1inordertominimize pressure
drop in the line.
2B. SIZINGGASSUPPLY LINE (For multiples ofoverthreeboilers
of same size or for multiple installations of two or more mixed
sizes).
Capacities in cubic feet per hour of 0.60 specific gravity gas for
different sizes and lengths are shown in table 4. No additional
allowance is necessary for an ordinary number of fittings.
Where it is necessary to use more than the average number of
pipe fittings i.e. elbows, tees, and valves in gas supply line, use a
pipe larger than specified to compensate for increased pressure
drop.
TABLE 4
MAXIMUM CAPACITY OF PIPE IN CUBIC FEET OF GAS PER HOUR (BASED UPON A PRESSURE DROP OF
0.3 INCH WATER COLUMN AND 0.6 SPECIFIC GRAVITY GAS)
Length in Feet (Meters) Nominal Iron Pipe Size, Inches (NPT)
From Gas Meter 1/2 3/4 1 1 1/4 1 1/2 2 2 1/2 3 4
10 (3) 132 278 520 1,050 1,600 3,050 4,800 8,500 17,500
20 (6) 92 190 350 730 1,100 2,100 3,300 5,900 12,000
30 (9) 73 152 285 590 890 1,650 2,700 4,700 9,700
40(12) 63 130 245 500 760 1,450 2,300 4,100 8,300
50(15) 56 115 215 440 670 1,270 2,000 3,600 7,400
60(18) 50 105 195 400 610 1,150 1,850 3,250 6,800
70(21) 46 96 180 370 560 1,050 1,700 3,000 6,200
80(24) 43 90 170 350 530 990 1,600 2,800 5,800
90(27) 40 84 160 320 490 930 1,500 2,600 5,400
100(30) 38 79 150 305 460 870 1,400 2,500 5,100
125(38) 34 72 130 275 410 780 1,250 2,200 4,500
150(46) 31 64 120 250 380 710 1,130 2,000 4,100
175(53) 28 59 110 225 350 650 1,050 1,850 3,800
200(61) 26 55 100 210 320 610 980 1,700 3,500
*Theheating valueofnatural gasis approximately 1050Btu/ft³.
Propane (L.P.)gashas aheating valueof approximately 2500Btu/ft³.