Legend LB 500 Owner's manual

1
PLACE THESE INSTRUCTIONS ADJACENT TO BOILER AND
NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE
PART NO. 212107-000 REV. 00
WARNING: If the information in this
manual is not followed exactly, 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
vicinityofthisoranyotherappliance.
— 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.
PRINTEDINU.S.A.1004
GAS-FIRED POWER BURNER COPPER BOILERS
FOR HYDRONIC HEATING AND HOT WATER SUPPLY
• INSTALLATION • OPERATION • MAINTENANCE • LIMITED WARRANTY
ADIVISIONOFA.O.SMITHCORPORATION
McBEE,SC RENTON,WA STRATFORD,ONTARIO
VELDHOVEN,THENETHERLANDS
www.aosmithwaterheaters.com
CAUTION
TEXTINBLACKBOLDTYPEORUNDERLINEDCONTAINS
INFORMATION RELATIVE TOYOUR SAFETY. PLEASE
READTHOROUGHLYBEFOREINSTALLINGANDUSING
THISAPPLIANCE.
H
MODELS:
LB/LW-500, 750 AND 1000
SERIES 400/401

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ROUGH-IN DIMENSIONS
Minimum clearances to combustibles:
• 4” (102 mm) rear
• 0” (0 mm) top & sides
• 6” (152 mm) vent
TABLE 1, GASAND ELECTRICAL CHARACTERISTICS
Manifold Pressure Maximum Supply Pressure Electrical Characteristics
Model Type of Gas Inches W.C. kPa Inches W.C. kPa Volts/Hz Amperes
LB/LW-500, 750, 1000 NATURAL 3.5 0.87 13.8 3.44 120/60 30
LB/LW-500, 750, 1000 PROPANE 10 2.49 13.8 3.44 120/60 30
Minimum Supply Pressure, Natural Gas: 7.0 inches W.C. (1.74 kPa)
Minimum Supply Pressure, Propane Gas: 11.0 inches W.C. (2.74 kPa)
Minimum Pressures must be maintained under both load and no load (static and dynamic) conditions.
TABLE 2, ROUGH-IN DIMENSIONS
Models LB/LW-500 LB/LW-500 LB/LW-750 LB/LW-750 LB/LW-1000 LB/LW-1000
Gas Type Natural Gas Propane Gas Natural Gas Propane Gas Natural Gas Propane Gas
Dimensions inches m m inches m m inches m m inches m m inches m m inches m m
Exhaust Vent Diam. 6 152 6 152 6 152 6 152 7 178 7 178
Blower Inlet Diam. 4 102 4 102 4 102 4 102 6 152 6 152
A 53 1346 53 1346 53 1346 53 1346 60 1/2 1537 60 1/2 1537
B 23 584 23 584 23 584 23 584 27 1/8 689 27 1/8 689
C 32 813 32 813 32 813 32 813 38 3/16 970 38 3/16 970
D 13 1/2 343 13 1/2 343 13 1/2 343 13 1/2 343 13 3/4 349 13 3/4 349
E 4 3/8 111 4 3/8 111 4 3/8 111 - - 15 1/2 394 - -
F 3 1/4 83 3 1/4 83 3 1/4 83 - - 3 1/4 83 - -
G 6 3/8 162 6 3/8 162 6 3/8 162 6 3/8 162 8 1/8 206 8 1/8 206
H 7 1/2 191 7 1/2 191 7 1/2 191 7 1/2 191 8 1/4 210 8 1/4 210
J 3 1/2 89 3 1/2 89 3 1/2 89 3 1/2 89 3 1/2 89 3 1/2 89
K 19 483 19 483 19 483 19 483 36 914 36 914
L 14 1/2 359 14 1/2 359 11 1/4 286 11 1/4 286 12 318 12 318
M 5 127 5 127 5 127 5 127 6 3/4 171 6 3/4 171
N 5 1/4 133 5 1/4 133 5 1/4 133 5 1/4 133 4 1/8 105 4 1/8 105
P 11 1/2 292 11 1/2 292 11 1/2 292 11 1/2 292 13 3/8 340 13 3/8 340
Q 2 51 2 51 2 51 2 51 2 1/4 57 2 1/4 57
R 1 NPT 1 NPT 1 NPT - - 1 1/4 NPT - -
S ------113/4298--117/8302
T ------61/2165--75/8194
U ------1NPT--11/4NPT
Approx. Shipping 425 lbs 193 Kg. 425 lbs 193 Kg. 528 lbs 240 Kg. 528 lbs 240 Kg. 934 lbs 424 Kg. 934 lbs 424 Kg.
Weight

3
TABLE 4, HEAD LOSS at FLOW RATES/MINUTE and TEMPERATURE RISE SHOWN
INPUT F° 18F° 20F° HEADLOSS Boiler
MODEL BTUH KW C° 10C° 11.1C° Feet Metres Inlet & Outlet
LB/LW-500 500,000 GPM 50 45 10 2”NPT
Natural 146 LPM 189 172 3.0
LB/LW-500 450,000 GPM 45 41 8.4 2”NPT
Propane 132 LPM 170 155 2.6
LB/LW-750 750,000 GPM 75 68 10.1 2”NPT
Natural 220 LPM 284 258 3.1
LB/LW-750 675,000 GPM 67 61 8.7 2”NPT
Propane 198 LPM 255 232 2.7
LB/LW-1000 1,000,000 GPM 100 91 8.9 2”NPT
Natural 293 LPM 378 344 2.7
LB/LW-1000 860,000 GPM 86 78 6.7 2”NPT
Propane 252 LPM 325 296 2.0
The ideal flow rate through the Legend models is considered to be the flow rate that results in
a 20 F° temperature rise across the unit. Table 4, shows head loss through units at
flow rate resulting in 20 F° rise. For head loss at other flow rates see sheet E202.2 in
A.O. Smith Architect’s & Engineer’s Manual.
ROUGH-IN DIMENSIONS (Continued)
TABLE 3, RECOVERY CAPACITIES
U.S. Gallons/Hr and Litres/Hr at TEMPERATURE RISE INDICATED
GAS INPUT F° 18F° 20F° 30F° 36F° 40F° 50F° 54F° 60F° 70F° 72F°
MODEL TYPE BTUH KW C° 10C° 11C° 17C° 20C° 22C° 28C° 30C° 33C° 39C° 40C°
LB/LW-500 Natural 500,000 GPH 3030 2727 1818 1515 1364 1091 1010 909 779 758
146 LPH 11471 10324 6882 5735 5162 4129 3824 3441 2950 2868
LB/LW-500 Propane 450,000 GPH 2727 2455 1636 1364 1227 982 909 818 701 682
132 LPH 10324 9291 6194 5162 4646 3716 3441 3097 2655 2581
LB/LW-750 Natural 750,000 GPH 4545 4091 2727 2273 2045 1636 1515 1364 1169 1136
220 LPH 17206 15485 10324 8603 7743 6194 5735 5162 4424 4301
LB/LW-750 Propane 675,000 GPH 4091 3682 2455 2045 1841 1473 1364 1227 1052 1023
198 LPH 15485 13937 9291 7743 6968 5575 5162 4646 3982 3871
LB/LW-1000 Natural 1,000,000 GPH 6061 5455 3636 3030 2727 2182 2020 1818 1558 1515
293 LPH 22941 20647 13765 11471 10324 8259 7647 6882 5899 5735
LB/LW-1000 Propane 860,000 GPH 5212 4691 3127 2606 2345 1876 1737 1564 1340 1303
252 LPH 19729 17757 11838 9865 8878 7103 6576 5919 5073 4932
U.S. Gallons/Hr and Litres/Hr at TEMPERATURE RISE INDICATED
GAS INPUT F° 80F° 90F° 100F° 108F° 110F° 120F° 126F° 130F° 140F°
MODEL TYPE BTUH KW C° 44C° 50C° 56C° 60C° 61C° 67C° 70C° 72C° 78C°
LB/LW-500 Natural 500,000 GPH 682 606 545 505 496 455 433 420 390
146 LPH 2581 2294 2065 1912 1877 1721 1639 1588 1475
LB/LW-500 Propane 450,000 GPH 614 545 491 455 446 409 390 378 351
132 LPH 2323 2065 1858 1721 1689 1549 1475 1429 1327
LB/LW-750 Natural 750,000 GPH 1023 909 818 758 744 682 649 629 584
220 LPH 3871 3441 3097 2868 2816 2581 2458 2382 2212
LB/LW-750 Propane 675,000 GPH 920 818 736 682 669 614 584 566 526
198 LPH 3484 3097 2787 2581 2534 2323 2212 2144 1991
LB/LW-1000 Natural 1,000,000 GPH 1364 1212 1091 1010 992 909 866 839 779
293 LPH 5162 4588 4129 3824 3754 3441 3277 3176 2950
LB/LW-1000 Propane 860,000 GPH 1173 1042 938 869 853 782 745 722 670
252 LPH 4439 3946 3551 3288 3228 2959 2818 2732 2537

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FOREWORD
This design complies with the latest edition of the ANSI Z21.13 -
CSA 4.9 low-pressure boiler standard.
Compliance under this standard implies that when the boiler
underwent test, the gas manifold and control assembly provided
on the boiler met safe lighting and other performance criteria.
Detailed installation diagrams are found in this manual. These
diagrams will serve to provide the installer a reference for the
materials and methods of piping necessary. It is essential that
all water, gas piping and wiring be installed as shown on the
diagrams. You should thoroughly read and understand this
manual before installation and/or operation of this boiler.
The factory warranty will be void if the boiler(s) have been
improperly installed or operated.
CONTENTS
Page
HotWaterHeating(Hydronic)Equipment................................. 16
InternalContaminants ............................................................. 17
HotWaterSupplySystemGeneralWaterLineConnections .... 17
HardWaterConditions ............................................................ 19
ThermalExpansion (ClosedSystem). ...................................... 19
TankProbeInstallationProcedure............................................ 19
TankProbeSet-PointAdjustment ............................................ 19
GASCONNECTIONS .................................................................... 19
GasSupply LineSizing ........................................................... 20
WIRING ........................................................................................ 20
SUGGESTEDPIPESIZINGTABLES ............................................... 21
WIRINGCONNECTIONDIAGRAM .................................................. 22
SCHEMATICDIAGRAM ................................................................. 23
OPERATION ................................................................................. 24
General .................................................................................. 24
FillingandPurgingforHeatingBoilerInstallation ...................... 24
FillingforHot WaterSupply BoilerInstallation .......................... 24
PurgingGasLine .................................................................... 24
LIGHTING&OPERATINGINSTRUCTIONS ................................. 25-26
InletGasPressure .................................................................. 27
ManifoldPressureConnections .............................................. 27
GasPressure Regulators ....................................................... 27
SafetyChecks........................................................................ 27
WaterTemperatureRegulation ................................................ 28
Sequenceof Operation........................................................... 28
MAINTENANCE
VentingMaintenance .............................................................. 29
BurnerandFlamePattern ....................................................... 29
BurnerMaintenance ............................................................... 30
CondensateRemovalSystem ................................................. 30
DIA-SCANIISELF-DIAGNOSTICSYSTEM..................................... 30
LinePolarityIndicator .............................................................. 31
FuseProtection ...................................................................... 31
Dia-ScanIIDisplayBoard
OperatingProcedures ............................................................ 31
TemperatureSet-PointAdjustmentProcedure ......................... 32
SwitchingDifferential AdjustmentProcedure .......................... 32
CirculatingPumpAdjustmentProcedure .................................. 32
DisplayCurrentMode ............................................................. 33
DisplayTotalCycleCount........................................................ 33
TankProbeTemp.Set-PointAdjustmentProcedure.................. 33
DisplayBoardLEDIndicators .................................................. 34
TROUBLESHOOTING
ShortCycling .......................................................................... 34
HardStarts ............................................................................. 34
TroubleshootingErrorCodes .................................................. 34
LIMITEDWARRANTY ................................................................... 36
In addition to these instructions, the boiler(s) 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 latest editions, as follows:
In the United States:
The National Fuel Gas Code, ANSI Z223.1/NFPA 54and the
National Electric Code, NFPA 70.
In Canada:
The installation Code CAN/CSA B149.1-00 and the Canadian
Electric Code, CSA C22.2.
Page
ROUGH-INDIMENSIONS .............................................................. 2-3
FOREWORD .................................................................................. 4
GroundingInstructions ............................................................. 5
InletWaterConsiderations ........................................................ 5
CorrectGas ............................................................................. 5
Precautions .............................................................................. 5
LiquidPetroleumModels............................................................ 5
HIGHALTITUDEINSTALLATIONS .................................................... 5
FieldInstalledComponents ........................................................ 6
PanelsandCovers ................................................................... 6
FEATURES/CONTROLS
ElectronicIgnitionControl .......................................................... 6
HotSurface Ignitor.................................................................... 6
BlockedFlue Switch ................................................................. 6
Blower Prover Switch .............................................................. 7
Low Gas Switch ...................................................................... 7
Water Flow Switch................................................................... 7
AirShutter................................................................................ 7
BlowerSpeedControl............................................................... 7
CombinationGasControl........................................................... 7
ManualResetLimit(E.C.O.) ....................................................... 7
AutomaticResetLimit ............................................................... 7
On / Off Switch ........................................................................ 7
CirculatingPump ....................................................................... 8
TankTemperatureControl ......................................................... 8
LowWaterCutoff(notsupplied) .............................................. 8
DrainValve............................................................................... 8
ReliefValves ............................................................................ 8
INSTALLATIONINSTRUCTIONS
RequiredAbility ........................................................................ 9
Location ................................................................................... 9
ChemicalVapor Corrosion ........................................................ 9
InstallationClearances .............................................................. 9
Leveling.................................................................................... 9
AirRequirements ...................................................................... 9
VENTING ..................................................................................... 10
SpecialInstallationConsiderations . ........................................ 11
VentingSystem UsingAL29-4C®........................................... 11
GeneralInstallationRequirements ........................................... 11
GeneralExhaustVentInstallationProcedure ........................... 11
ConnectingVentto Boiler................................................... 11-13
VentingSupports.................................................................... 13
Vertical InstallationRequirements ............................................ 13
HorizontalInstallationRequirements ................................... 13-16
DirectVentInstallationRequirements ...................................... 16
SYSTEMINSTALLATION
General .................................................................................. 16
®AL29-4C isa registered trademarkofAlleghenyLudlumCorporation.

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These are available from the Canadian Standards Association,
8501 East Pleasant Valley Road, Cleveland, OH 44131, USA, or,
Canadian Gas Association Laboratories, 55 Scarsdale Road,
Don Mills, Ontario M3B 2R3, Canada.
GROUNDING INSTRUCTIONS
This boiler must be grounded in accordance with the National
Electrical Code and/or local codes. Boiler is polarity sensitive,
correct wiring is imperative for proper operation.
This boiler must be connected to a grounded metal, permanent
wiring system, or an equipment grounding conductor must be
run with the circuit conductors and connected to the equipment
grounding terminal or lead on the boiler.
INLET WATER CONSIDERATIONS
To minimize the amount of condensate, a minimum inlet water
temperature to the heat exchanger of 140°F (60°C) shall be
maintained. Thistemperature can be acquiredby returning 140°F
(60°C) water from the remote storage tank to the boiler or by
incorporating a by-pass loop between the boiler’s inlet and outlet
connections.
Circulating water through the boiler and to the remote storage
tank (if applicable) is accomplished by a built-in pump on LW
models only. For hot water heating systems using the LB model,
the circulating pump is NOT provided and must be field installed.
CORRECT GAS
MAKESURETHE GAS ON WHICHTHEBOILERWILLOPERATE
IS THE SAME AS THAT SPECIFIED ON THE BOILER RATING
PLATE. DO NOT INSTALL THE BOILER IF EQUIPPED FOR A
DIFFERENTTYPE OF GAS — CONSULT YOUR SUPPLIER.
PRECAUTIONS
IFTHEUNITISEXPOSEDTOTHEFOLLOWING,DONOTOPERATE
UNTIL ALL CORRECTIVE STEPS HAVE BEEN MADE BY A
QUALIFIEDSERVICEMAN:
1. EXPOSURETOFIRE.
2. IFDAMAGED.
3. FIRING WITHOUTWATER.
4. SOOTING.
IFTHEBOILERHASBEENEXPOSED TOFLOODING,ITMUSTBE
REPLACED.
LIQUID PETROLEUM MODELS
Boilers for propane or liquefied petroleum gas (LPG) are different
from natural gas models. A natural gas boiler will not function
safely on LP gas and no attempt should be made to convert a
boiler from natural gas to LP gas.
LP gas must be used with great caution. It is highly explosive
and heavier than air. It collects first in the low areas making its
odor difficult to detect at nose level. If LP gas is present or even
suspected, do not attempt to find the cause yourself. Leave the
building, leaving doors open to ventilate, then call your gas
supplier or service agent. Keep area clear until a service call has
been made.
At times you may not be able to smell an LP gas leak. One cause
is odor fade, which is a loss of the chemical odorant that gives LP
gas its distinctive smell. Another cause can be your physical
condition, such as having a cold or diminishing sense of smell
with age. For these reasons, the use of a propane gas detector
is recommended.
IFYOUEXPERIENCEANOUTOF GAS SITUATION,DONOTTRY
TO RELIGHTAPPLIANCES YOURSELF. Call your local service
agent. Only trained LP professionals should conduct the required
safety checks in accordance with industry standards.
HIGHALTITUDE INSTALLATIONS
WARNING
INSTALLATIONS ABOVE 2000 FEET (600 M) REQUIRE
REPLACEMENT OF THE BURNER ORIFICE IN ACCORDANCE
WITHSECTION 8.2.1OFTHE NATIONALFUELGAS CODE(ANSI
Z223.1). FAILURE TO REPLACE THE ORIFICE WILLRESULT IN
IMPROPERAND INEFFICIENTOPERATION OFTHEAPPLIANCE
RESULTING IN THE PRODUCTIONOF INCREASED LEVELS OF
CARBONMONOXIDE GAS IN EXCESS OF SAFE LIMITS WHICH
COULDRESULTINSERIOUSPERSONALINJURYORDEATH.
Ratings specified by manufacturers for most appliances apply
for elevations up to 2000 feet (600 m). For elevations above 2000
feet (600 m), ratings must be reduced at the rate of 4% for each
1000 feet (300 m) above sea level. For example, if a boiler is
rated at 500,000 Btu/hr. at sea level, to rate the boiler at 4000 feet
(1200 m), the original rating is reduced by 16 percent (4 x 4%) to
a rating of 420,000 Btu/hr.
The input reduction is primarily achieved by reducing the size of
the main burner orifice. To do this, the main burner orifices require
replacement with an orifice sized for the particular installation
elevation. Part number for gas orifices for altitudes up to 4000
feet (1220 m) are given in Table 5. Orifices for higher altitudes
are special order and may be obtained from A. O. Smith Water
Products Company. When ordering, be sure to state the model
number and the altitude of the location where the boiler is installed.
TABLE 5. LEGEND 2000 ORIFICE TABLE
Natural Gas Propane Size Elevation
Model Part No. Part No. (In.) (Ft.)
LB/LW-500 *191884-0 — 0.391 0-2000
LB/LW-500 191884-1 — 0.384 2001-3000
LB/LW-500 191884-2 — 0.374 3001-4000
LB/LW-500 — 192741-0 0.229 0-2000
LB/LW-500 -- 192741-1 0.226 2001-3000
LB/LW-500 -- 192741-2 0.223 3001-4000
LB/LW-750(USA) *191884-3 -- 0.484 0-2000
LB/LW-750(USA) 191884-5 -- 0.469 2001-3000
LB/LW-750 USA 191884-7 -- 0.461 3001-4000
LB/LW-750 CAN *191884-11 -- 0.464 0-2000
LB/LW-750 CAN 191884-12 -- 0.450 2001-3000
LB/LW-750 CAN 191884-13 -- 0.443 3001-4000
LB/LW-750 -- 192741-3 0.286 0-2000
LB/LW-750 -- 192741-4 0.282 2001-3000
LB/LW-750 -- 192741-6 0.278 3001-4000
LB/LW-1000 *192222-0 -- 0.555 0-2000
LB/LW-1000 192222-1 -- 0.537 2001-3000
LB/LW-1000 192222-2 -- 0.533 3001-4000
LB/LW-1000 -- *192739-0 0.333 0-2000
LB/LW-1000 -- 192739-1 0.329 2001-3000
LB/LW-1000 -- 192739-2 0.325 3001-4000
*Factory installed orifice.
Upon completion of derating of the boiler, adjustment to the gas
pressure regulator may be required. See GAS PRESSURE
REGULATORS in this manual for inlet and manifold pressure
requirements.
Also, due to the input rating reduction required 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.

6
NOTE:Some gas utility companies derate their gas for altitude,
making it unnecessary to install high altitude orifices. Call the
local gas utility company to verify BTU content.
FIELD INSTALLED COMPONENTS
When installing the boiler, the following components MUST be
used, if applicable:
1) Circulating Pump (Hydronic)
2) Tank Temperature Control (Hot Water Supply)
3) Loop Temperature Control (Hydronic)
4) Low Water Cutoff Device
5) Relief Valve
6) Pressure Gauge
7) Manual Gas Shutoff Valve (Supply)
Check the FEATURES AND CONTROLS section for further
information.
FIGURE1.
PANELS AND COVERS
All panels and covers (e.g. control and junction box covers; front,
side and rear panels of boiler) MUST be in place after service
and/or before operation of the boiler. This will ensure that all gas
ignition components will be protected from water.
NOTE: Remove the two (2) sheet metal screws from the rear of
the top cover and discard them, see fig 1. This will allow removal
of the top cover without the use of tools. Also, remove the sheet
metal screw from the bottom of the front panel.
FEATURES/CONTROLS
The Legend 2000®is a low-pressure boiler (Category IV) to be
used as either hot water supply (domestic/commercial water
heating) or hot water heating (hydronic) application. Category IV
boilers operate with a positive vent pressure and with a vent gas
temperatureless than 140°F(60°C) above its dew point. Category
IV appliances are often termed “High Efficiency” appliances.
This high efficiency is obtained from a unique heat exchanger
design consisting of multiple integral high-finned copper tubes
brazed in parallel into two brass manifolds. The condensate
from the heat exchanger flows downward into the vent collector
housing then into the plastic condensate drain and through the
attached flexible hose which must terminate at a suitable floor
drain.
ELECTRONIC IGNITION CONTROL
The Legend 2000®is controlled by the WHC 1502 ignition system,
fig. 2. The WHC 1502 is a solid-state ignition control that ignites
the main burner by energizing the Hot Surface Ignitor, fig. 3. The
ignition control system continuously monitors the current of the
ignitor and will not allow gas to enter the main burner until current
flow reaches the preset ignition temperature threshold. Once
the ignition threshold has been reached, the control system will
open the gas valve(s). After the main burner ignites, the control
system monitors the burner flame through the principle of flame
rectification. If a flame is not verified, the gas valve is immediately
closed.
FIGURE 2. FIGURE 3.
The control board provides a pre-purge period of twenty (20)
seconds and a post-purge period of twenty-five (25) seconds.
The flame establishing period is four (4) seconds.
This control is non-adjustable. Any attempts to modify the
performance, other than those listed in this manual, voids the
control warranty.
The 24 VAC circuitry of the ignition control system is protected
with a 3-amp fuse. If the fuse opens, a red LED located near the
fuse will light.
HOT SURFACE IGNITOR
The Hot Surface Igniter, fig. 3, is a device that ignites the main
burner by high temperature (>1800°F) [982°C]. The igniter is
made of recrystallized silicon carbide, and when 120 VAC 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 still fragile and care must be taken in
handling the igniter to prevent breakage.
FIGURE4.
BLOCKED FLUE SWITCH
The Blocked Flue Switch (BFS) fig. 4, is a single-pole, normally
closed pressure switch that will open its contacts when a rising
positive pressure of 1.0 in. w.c. (0.25 kPa) is encountered. The
contacts will close when the pressure falls below the fixed set
point of 1.0 in. w.c. (0.25 kPa) The BFS monitors the pressure
inside the venting system. If the venting system is blocked in
such a way that the build up in pressure exceeds the setting of

7
the BFS, the main burner is extinguished (if boiler is running) or
the boiler will not start up.
BLOWER PROVER SWITCH
The Blower Prover Switch (BPS) fig. 4, is similar in construction
to the BFS. It is a single-pole, normally open pressure switch
that will close its contacts when a rising positive pressure of
1.0 in. w.c. (0.25 kPa) is encountered. The contacts will open
when the pressure falls below the fixed set point of 1.0 in. w.c.
(0.25 kPa) The BPS monitors the pressure inside the blower
elbow. Ifthe blower is not operatingat a sufficientblowing capacity,
the main burner is extinguished (if boiler is running) or the boiler
will not start up.
LOW GAS SWITCH
The Low Gas Switch (LGS) fig. 5, is a single-pole, normally open
pressure switch that will close its contacts when a rising pressure
of 5.0 in. w.c. (1.24 kPa) is encountered. The contacts will open
when the pressure falls below the fixed set point of 5.0 in. w.c.
(1.24 kPa) The LGS monitors the gas supply pressure to the
boiler. If the gas supply falls below 5.0 in. w.c. (1.24 kPa), the
main burner is extinguished (if boiler is running) or the boiler will
not start up.
FIGURE 5. LOW GAS SWITCH (LGS)
WATER FLOW SWITCH
The Water Flow Switch (WFS) fig. 6, is installed at the boiler water
outlet to prevent main burner operation in the event of inadequate
water flow through the boiler. The WFS is a single-pole, normally
open switch that will close its contacts when an increasing water
flow rate of approximately 25 GPM (1.61 lps) is encountered. The
contacts will open when the flow rate drops below this setting,
extinguishing the main burner flames (if boiler is running) or the
boiler will not start up.
FIGURE6. WATER FLOW SWITCH (WFS)
AIR SHUTTER
The blower is equipped with an air shutter assembly for fine
adjustment of the air to gas ratio The assembly consists of a
shutter flange and the air shutter. The shutter may require
adjustment to achieve ideal start-up characteristics when fine tuning
the boiler for correct combustion specifications. Refer to the
Start-Up Procedures, part number 192077 Rev. 1, for the proper
combustion specifications and limits. If necessary, the shutter
may be adjusted by loosening the two nuts used to hold the shutter
and blower adapter assembly in place on the inlet of the blower.
Once the unit is set to the specifications called for in the Start-Up
Procedures, tighten the nuts to lock the shutter in place.
BLOWER SPEED CONTROL
The Blower Speed Control (BSC) permits variation of speed of
the blower during boiler (LB/LW-500 only) start-up. When the
1502 Control Board energizes the igniter, the BSC will lower the
speed (RPM) of the blower to a preset level. This lower speed
will be maintained until the igniter is de-energized by the Control
Board. Then, the blower will return to its normal operating speed.
COMBINATION GAS CONTROL
The Combination Gas Control (CGC) is a gas valve or valves that
controls the supply of gas to the main burner during operation of
the boiler. The CGC includes a manual main shutoff valve, two
(2) automatic valves and a pressure regulator, see figure 15.
The two-position gas control knob has “ON” and “OFF” positions
that allows or prevents the flow of gas to the main burner,
respectively. The first automatic valve is solenoid operated and
opens and closes when the main valve terminal on the Control
Board is energized or de-energized, respectively. The second
automatic valve is diaphragm operated and opens under control
of the pressure regulator and closes if gas or power supply is
interrupted. The pressure regulator is adjustable and maintains
an almost constant gas outlet pressure under wide fluctuations
in gas supply pressure.
MANUAL RESET LIMIT (E.C.O)
Thisdevice prevents the watertemperature from exceeding 250°F
(121°C). It is located in the outlet waterway within the outlet
temperature sensing device and is monitored by the Control
Board. Commonly referred to as the “emergency cut out”, it is a
manually resettable control. The “ADJUST”, “SELECT” or
“ENTER/RESET” button on the display board must be depressed
to reset the unit if the water temperature reaches this limit. See
figure 20.
CAUTION
LIMITCONTROLSARE NOTTOBEUSEDASATHERMOSTATOR
OPERATINGCONTROL.
AUTOMATIC RESET LIMIT
This limit is a safety device in series with the ignition system. Set
the limit control to a minimum of 30°F (16°C) above the maximum
designed system temperature. If the boiler outlet water
temperature should exceed the automatic reset limit setting, the
main gas valves will close. The automatic reset limit control is
factory set at 180°F (82°C) and has an adjustable range from
110 to 240°F (43° to 116°C). The operating differential is also
adjustable from 5 to 50°F (3° to 28°C).
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 boiler.

8
CIRCULATING PUMP
HOT WATER SUPPLY SYSTEMS, the circulating pump is integral
to the LW models. This pump has been lubricated at the factory,
and future lubrication should be in accordance with the motor
manufacturer’s instructions provided as a supplement to this
manual.
FORHOTWATERHEATINGSYSTEMS-LBMODELS,thecirculating
pump is NOT provided and must be obtained and installed in the
field.
NOTE: If a system pump is to be installed on a Legend LB
model, the maximum rating of the pump motor must
not exceed 1 hp.
TANK TEMPERATURE CONTROL
A tank probe is provided with LW models to be used for tank
temperature regulations. The temperature setting for the tank is
set through the display.
Refer to figs. 7, 13, 14 and 16 for connecting the tank probe to the
boiler.
See TEMPERATURE SET POINT ADJUSTMENT PROCEDURE
for further instructions.
FOR HOT WATER SUPPLY SYSTEMS, the boiler is supplied with
a Tank Probe to be field installed in the storage tank. Alternate
methods of temperature control, if desired, must be supplied by
the installer.
A change in water temperature in the storage tank lower than the
Tank Temperature Control setting will cause the sensor to close
its contacts and consequently, energize the boiler.
If the Tank Probe or Temperature Control is out of calibration,
replace it with a new one; do not attempt to fix this control.
NOTE: Ifyou are using an LWmodel in a hydronic (space heating)
application, do not use the tank probe as a loop temperature
regulation device. The tank probe’s maximum setting is
190°F (88°C). Therefore, 24 VAC connections (red/green wires)
are provided in the rear junction box for an alternate device. The
J33 board jumper must be removed to use a 24 VAC temperature
regulation device (See figures 21 and 22).
LOW WATER CUTOFF (Not Supplied)
If low water protection is required by the authorities having
jurisdiction, a low water cutoff switch should be installed next to
the boiler in the outlet water line as shown in figure 12. The
switch should receive periodic (every six months) inspection to
assure proper operation. A Low Water Cutoff device of the float
type should be flushed every six months.
DRAINVALVE
A drain valve is factory installed in the heat exchanger manifold.
This will help to drain the heat exchanger.
Additional drain valves must be obtained and installed on each
boiler and tank for draining purposes, see figures 12, 13 and 14.
SAFETY RELIEF VALVE
Your local code authority may have other specific safety relief
valve requirements not covered below.
WARNING
THE PURPOSE OF A SAFETY RELIEF VALVE IS TO AVOID
EXCESSIVEPRESSUREORTEMPERATURE INTO THE STEAM
RANGE WHICH MAY CAUSE SCALDING AT FIXTURES, TANK
EXPLOSION,SYSTEMORBOILERDAMAGE.
TOAVOIDSCALDINGORWATERDAMAGE,ADRAINLINE MUST
BE CONNECTED TO A SAFETY RELIEF VALVE TO DIRECT
DISCHARGETOASAFELOCATION. ADRAINLINEMUSTNOTBE
REDUCEDFROMTHESIZEOFTHEVALVEOUTLETANDITMUST
NOT CONTAINANY VALVES BETWEEN THE BOILER AND THE
RELIEFVALVE ORTHERELIEF VALVEANDTHE DRAINEXIT. IN
ADDITION, THERE SHOULD NOT BE ANY RESTRICTIONS IN A
DRAIN LINE NOR SHOULD IT BE ROUTED THROUGH AREAS
WHEREFREEZINGCONDITIONSMIGHTOCCUR. DONOTTHREAD
ORCAPTHE DRAIN LINEEXIT. RESTRICTINGOR BLOCKINGA
DRAINLINEWILLDEFEATTHEPURPOSEOFTHESAFETYRELIEF
VALVEANDMAY CREATEANUNSAFE CONDITION. INSTALLA
DRAIN LINE WITHADOWNWARD SLOPE SUCH THAT IT WILL
NATURALLYDRAINITSELF.
If any pressure 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 set pressure NOT EXCEEDING the working
pressure of any component in the system.
FOR HOT WATER SUPPLY SYSTEMS, the boilers are shipped
witha 125 psi(860 kPa) pressure relief valvethat must be installed
in the water outlet as near to the boiler as possible.
ThisASME-rated valve has a discharge capacity that exceeds the
maximum boiler input rating and a pressure rating that does not
exceed the maximum working pressure shown on the boiler rating
plate.
In addition, a CSA design-certified and ASME-rated temperature
and pressure (T & P) relief valve must be installed on each and
every water storage tank in the hot water supply system.
FIGURE 7. TANK PROBE INSTALLATION
Encase field-supplied wires
between tank probe and junction
box with 1/2" field supplied
conduit. "Pigtails" of field-
supplied wires should be spliced
to "pigtails" of tank probe and
connected to 24VAC junction box.
This conduit and wiring should be
separate from any other conduit/
wiring to guard against EMI
(electromagnetic interference).

9
If the boiler is installed above radiation level, a Low Water Cutoff
Device must be installed in the boiler outlet at the time of
installation.
CHEMICAL VAPOR CORROSION
Water boiler 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 (water softener salt), waxes, and process
chemicals are typical compounds which are potentially 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. Failure
to observe this requirement will void the warranty.
INSTALLATION CLEARANCES
This boiler is approved for installation on combustible flooring in
an alcove with minimum clearances to combustibles of:
4" (102 mm) Rear; 0" (0 mm) Top and Sides; 6" (152 mm) Vent.
Two inch (51 mm) clearance is allowable from combustible
construction for hot water pipes.
Sufficient area should be provided at the front and rear of the unit
for proper servicing. Service clearances of 24" (610 mm) in front,
rear, top and left side are recommended. In a utility room
installation, the door opening shall be wide enough to allow the
boiler to enter or to permit the replacement of another appliance
such as a water heater.
LEVELING
Each unit should be checked after installation to be certain that it
is level.
If the unit is not level, obtain and insert shims under the nylon
protective feet at the frame base to correct this condition.
AIR REQUIREMENTS
WARNING
FOR SAFE OPERATION,ANAMPLE SUPPLY OFAIR MUST BE
PROVIDEDFORPROPERCOMBUSTIONAND VENTILATION IN
ACCORDANCEWITHSECTION 8.3,AIR FORCOMBUSTION AND
VENTILATION,OFTHE NATIONALFUELGAS CODE,ANSIZ223.1
OR SECTION 7.4 OF CSA-B149.1-00 OR APPLICABLE
PROVISIONSOFTHELOCALBUILDINGCODES. ANINSUFFICIENT
SUPPLYOFAIRWILLRESULTINAYELLOW,LUMINOUSBURNER
FLAME,CAUSINGCARBONINGORSOOTINGOFTHEFINNEDHEAT
EXCHANGERANDCREATINGARISKOFASPHYXIATION. DONOT
OBSTRUCTTHEFLOWOFCOMBUSTIONANDVENTILATIONAIR.
UNCONFINEDSPACE
In buildings of conventional frame, brick or stone construction,
unconfined spaces may provide adequate air for combustion.
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,
ventilation and draft hood dilution must be obtained from outdoors
TheT & Prelief valve must comply withthe applicable construction
provisions of the Standard for Relief Valves and Automatic Gas
ShutoffDevicesfor Hot Water Supply Systems,ANSIZ21.22-1999
or CAN/CSA-B149.1-00, or most recent edition. The T & P relief
valvemust be ofthe automatic resettype and notembody a single-
use type fusible plug, cartridge or linkage.
The T & P relief valve should have a temperature rating of 210°F
(99°C), a pressure rating NOT exceeding the lowest rated working
pressure of any system component, and a discharge capacity
exceeding the total input of the water boilers supplying water to
the storage tank.
Locate the T & P relief valve (a) in the top of the tank, or (b) in the
side of the tank on a centerline within the upper 6 inches (152
mm) of the top of the tank. See figures 13 and 14. The tapping
shall be threaded in accordance with the latest edition of the
Standard for Pipe Threads, General Purpose (inch), ANSI/ASME
B1.20.1. The location of, or intended location for, the T & P relief
valve shall be readily accessible for servicing or replacement.
FOR HOT WATER HEATING SYSTEMS, the boilers are shipped
with a 50 psi (345 kPa) pressure relief valve. This relief valve
must be installed in the water outlet as near to the boiler as
possible.
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 SUPPLYAND ELECTRICALWORKARE REQUIRED.
LOCATION
When installing the boiler, consideration must be given to proper
location. The location selected should provide adequate air
supply and be as centralized with the piping system as possible.
THEBOILERMUSTNOTBEINSTALLEDONCARPETING.
THEBOILERSHOULDNOTBELOCATED INANAREAWHEREIT
WILLBESUBJECTTOFREEZING.
LOCATE IT NEARAFLOOR DRAIN. THE BOILER SHOULD BE
LOCATEDINANAREAWHERELEAKAGEFROMTHEBOILEROR
CONNECTIONS WILL NOT RESULT IN DAMAGE TO THE
ADJACENTAREAORTOLOWERFLOORSOFTHESTRUCTURE.
WARNING
THEREIS ARISK INUSING FUELBURNINGAPPLIANCES SUCH
ASBOILERSINROOMS ORAREAS WHEREGASOLINE, OTHER
FLAMMABLE LIQUIDS OR ENGINE DRIVEN EQUIPMENT OR
VEHICLES ARE STORED, OPERATED OR REPAIRED.
FLAMMABLE VAPORSARE HEAVYAND TRAVELALONG THE
FLOORAND MAY BE IGNITED BY SPARKS CAUSING FIRE OR
EXPLOSION. SOMELOCALCODESPERMITOPERATIONOFGAS
APPLIANCES IF INSTALLED 18 INCHES (457 MM) OR MORE
ABOVETHEFLOOR. THISMAYREDUCETHERISKIF LOCATION
INSUCHANAREACANNOTBEAVOIDED.
WARNING
FLAMMABLE ITEMS, PRESSURIZED CONTAINERS OR ANY
OTHERPOTENTIALFIREHAZARDOUS ARTICLESMUSTNEVER
BE PLACED ON OR ADJACENT TO THE BOILER. OPEN
CONTAINERS OR FLAMMABLE MATERIAL SHOULD NOT BE
STOREDOR USEDIN THESAME ROOMWITHTHE BOILER.

10
or spaces freely communicating with the outdoors. The
installation instructions for confined spaces in tightly constructed
buildings must be followed to ensure adequate air supply.
CONFINEDSPACE
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 (305 MM) OF THE ENCLOSURE TOP
AND ONE IN OR WITHIN 12 INCHES (305 MM) OF THE
ENCLOSURE BOTTOM. Each opening shall have a free area of
at least one square inch per 1000 Btu/hr (2,225 mm2per kw) of
the total input of all appliances in the enclosure, but not less than
100 square inches (645 cm2).
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 totalinput of all appliances in the enclosure. Ifhorizontal
ducts are used, each opening shall have a free area of not less
than one square inch per 2000 Btu/hr (1,101 mm2per kw) of the
total input of all appliances in the enclosure.
B. CANADIANINSTALLATIONS
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
inchper 7,000 BTUH (315 mm2/KW) up toand 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” (457 mm) nor less
than 6 inches (152 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 INSUFFICIENTAIR
FORCOMBUSTION.
Where an exhaust fan is installed in the same room with the
boiler, sufficient openings for air must be provided in the walls.
UNDERSIZEDOPENINGS WILLCAUSEAIRTOBEDRAWNINTO
THE ROOM THROUGH THE CHIMNEY OR OTHER OPENINGS,
CAUSINGPOORCOMBUSTION. SOOTINGMAYRESULT WITH
ANINCREASEDRISKOFASPHYXIATION.
VENTING
WARNING
THEINSTRUCTIONSINTHISSECTIONONVENTINGTHEBOILER
MUST BE FOLLOWED TOAVOID CHOKED COMBUSTION OR
RECIRCULATIONOF FLUEGASES.SUCH CONDITIONSCAUSE
SOOTINGORRISKSOFFIREANDASPHYXIATION.
VENTSIZING,INSTALLATIONANDTERMINATIONSHALLBE IN
ACCORDANCEWITHTHIS INSTALLATION MANUAL.
ALL ELECTRICAL POWER AND GAS MUST BE TURNED OFF
PRIORTOANYINSTALLATIONOFTHE VENTINGSYSTEM.
SPECIALINSTALLATIONCONSIDERATIONS
The Legend 2000®is listed as a Category IV appliance and utilizes
a mechanical forced draft system. The vent system shall be
designed to prevent leakage of flue gases and condensate. The
condensate must be allowed to flow to a suitable drain. Since
the condensate is known to be detrimental to conventional vent
materials (galvanized steel, some stainless steels), the vent
material for the boiler’s exhaust shall be approved and certified
for the venting of low temperature condensing flue gasses. AL
29-4C®is one such material.
The exhaust gases of this boiler are generally only 15°-20°F (8°C
to 11°C) higher than the boiler’s operating temperature, much
lower than a standard boiler. In cold climates any water vapor
remaining in the flue gases will condense into a cloud of vapor at
the point where the vent system exits the building. Special
FIGURE 8. SIDEWALL EXHAUST VENTING

11
consideration is recommended, before locating the vent
termination near walkways, windows and building entrances.
Direct venting into dead spaces such as; alleys, atriums and
inside corners can cause recirculation of flue gases. Recirculation
of flue gases will cause sooting, premature failure of the heat
exchanger and icing of the combustion air intake during severe
cold weather. To prevent the recirculation of flue gases, maintain
as much distance as possible between the combustion air intake
andthe exhaust vent terminal. Due tolarge volumes of flue gases,
multiple boiler applications also require additional distance
between the intake and exhaust terminals.
VENTING SYSTEM USING AL 29-4C®
The LEGEND 2000®may be installed in four separate orientations
depending on the requirements of the building and the appliance.
The installer must decide which method is most appropriate for
each installation. These orientations are:
1. Vertical Termination — vertical vent termination through un-
enclosed or enclosed areas with roof penetration, see fig. 9.
2. Through-the-Wall Termination (TWT) — horizontal vent
termination directly through an outside wall, see figure 9A.
3. Direct Vent — using TWT to exhaust flue products and PVC
piping to bring combustion air to the boiler from the outside,
see figures 11 and 11C.
4. Vertical Direct Vent — using a vertical vent termination to
exhaust flue products and PVC piping to bring combustion air
to the boiler from outside, see figures 11A and 11B.
GENERALINSTALLATIONREQUIREMENTS
COMMOMVENTINGLEGENDBOILERS.
Common venting of multiple Legend boilers are not allowed
except with either a U.L. or CSA approved power venter.
• All the vent pipe(s) and power venter must be sized by and
installed as per the recommendations of the power venter
manufacturer. Please see boiler’s wiring label for electrical
hook-up of power venter to the ignition control.
• When multiple Legend boilers are connected using a com-
mon power venter and common power venter and common
vent pipe; the power venter and vent piping should be sized to
maintain a -0.0 IWC to -0.04 IWC draft in the common vent
downstream of the boilers, when any one of or all boilers are
firing. A positive pressure of +.02 IWC to =.05 IWC should be
seen 12" above the boot tee of each unit when the unit is firing.
• All Venting material must be AL29-4C venting material.
• A factory start-up of the engineered power venting system must
be preformed by an authorized factory start-up agent of the
power venter system manufacturer.
• To assure proper boiler and power venter operation, both the
power venter start-up andA.O. SmithAuthorized boiler start-up
must be performed simultaneously.
1. Failure to conform with any of these requirements may violate
local, state/provincial or federal codes as well as create
conditions which may cause catastrophic property damage or
personal injury. The vent system must terminate so that proper
clearances are maintained as cited in local codes or the latest
edition of the National Fuel Gas Code, ANSI Z223.1 or
CSA-B149.1-00 and latest addenda. The vent system must
not have external runs greater than that allowed by local codes
or the National Fuel Gas Code.
2. AL 29-4C®sections and fittings MUST be used for the entire
length of the exhaust system; alternatives such as galvanized
pipe, PVC, CPVC or Type B Vent sections must not be used.
3. Install a AL 29-4C®drain fitting as close as possible to the
boiler vent connector outlet. See “CONNECTING VENT TO
BOILER” on the installation of this drain fitting.
4. Horizontal runs of vent pipe shall be securely supported by
adequately placed (approximately every 6 feet [2 m])
non-combustible hangers and/or slip joints suitable for the
weight and design of the material employed to prevent sagging
and to maintain a minimum upward slope of 1/4" per foot (21
mm) from the boiler to the vent terminal (see “VENTING
SUPPORTS” and figures 9A and 11).
The upward slope allows any build up of condensate to flow
back towards the boiler and drain fitting preventing the
accumulation of condensate. See “CONNECTING VENT TO
BOILER.”
EXCEPTION: The vent connector on the boiler is sloped
downward to direct condensate towards the “field-installed”
drain fitting.
5. All joints in the venting system MUST be sealed with RTV 106
or equivalent sealant.
6. NO other appliances may be interconnected to any part of this
venting system, including vent connectors which serve
appliances vented by NATURAL DRAFT.
7. The venting system must be planned so as to avoid possible
contact with concealed plumbing or electrical wiring inside
walls.
8. The venting system must be planned to maintain an airspace
clearance from combustibles of at least 6 inches (152 mm)
for any conduit and fittings of single wall AL 29-4C®vent and at
least 4 inches (102 mm) for any conduit and fittings of double
wall AL 29-4C®vent. Double wall AL 29-4C®vent must be
used when penetrating any floors, walls or ceilings and any
penetration must be properly fire stopped. All insulation
material must be removed from any wall, floor or ceiling cavity
for at least 4 inches (102 mm) from the conduit.
9. The venting system in a multi-family structure must be planned
to be enclosed when passing through occupied or unoccupied
spaces above the connected boiler. This enclosure is to be of
materials no less fire resistant than surrounding floors and
walls. It is recommended that the system be enclosed
whenever passing through occupied spaces.
GENERALEXHAUST VENTINSTALLATIONPROCEDURE
Prior to beginning the installation of the vent system, determine
and obtain all parts required for the installation. Refer to the
DIRECT VENT KIT PARTS LIST (part no. 192109), for a list of the
vent sections and fittings.
Proper operation of the boiler and venting system is dependent
upon use of all specified parts and installation techniques; both
safety and proper performance of the system may suffer if
instructions are not followed.
CONNECTINGVENT TOBOILER
At the outlet of the boiler vent, see figure 10, the AL 29-4C®Vent
Boot-Teeand Boot-Tee Drain Cover must beused as the transition
from the horizontal to vertical run. This is where the bottom most
support bracket should be located.

12
NOTES: If the exhaust vent terminal is
within 10’ (3.0 m) of a wall or parapet, it
must extend a minimum of 2’ (610 mm)
above the wall or parapet.
Joints are not joined to show vent pipe
orientation.
FIGURE 9. VERTICAL TERMINATION
FIGURE 9A. THROUGH THE WALL TERMINATION (TWT)
NOTES: Joints are not joined
to show vent pipe orientation.

13
The Boot-Tee Drain Cover is required in order to dispose of
the condensate from the venting system. The plastic tube
(3/8 [9 mm] ID, 10 feet [3 m] long) needed to route the condensate
to a suitable drain is provided with the boiler.
1. Attach the Boot Tee Drain Cover to the appropriate leg of the
Boot-Tee, see figure 10.
2. Atrap loop mustbe formed into the draintube simply by looping
the tube to a minimum 3 inch (76 mm) diameter and secure
the loop with a cable tie, see figure 10.
3. Prior to final assembly the trap loop must be “primed” by
pouring a small quantity of water into the drain hose.
4. Connect the Boot-Tee and Drain Tee assembly to the boiler
vent connector, see figure 10.
5. Attachthe hose to the drain fittingand run the hose toa sanitary
sewer drain maintaining the proper trap loop and following all
local, state and federal codes and regulations for draining of
acidic effluent (condensate).
FIGURE10.
VENTING SUPPORTS
Care must be taken in the installation of the venting system that
adequate support is maintained throughout the installation
process. When extending more than 10 feet (3.0 m) vertically,
vertical support kits are required once every 10 feet (3.0 m) of
vertical run. Vertical support is also required immediately after
any transition (elbow, tee, etc.) to vertical of over 10 feet (3.0 m) of
run and after any offset in the vertical run.
The support bracket (supplied in the Vertical Support Kit) is to be
securely fastened to a solid vertical member of the building using
the appropriate fasteners; i.e., wood screws for wood framing,
machine or tapping screws for structural steel or masonry anchors
for solid masonry. The bracket should be located so that it will
not interfere with any joints of the venting system. The bottom
most support bracket should be located directly above the first
transitionfromhorizontal to vertical,see Figure 10. Refer tofigures
11, 11A, 11B and 11C.
If a means of support for the bracket is not available and horizontal
vent sections are present, install hanger straps (made from
non-combustible material) as close to the points of transition as
possible. Ifthehorizontalportions of the vent and/orventconnector
are longer than 6 feet (2.0 m), then install hanger straps every
6 feet (2.0 m) to support the connector.
DO NOT rivet or screw the straps to the conduit or otherwise
puncture the conduit wall. Instead, wrap an extra loop of strap
around the conduit to hold it in position, or attach the strap to
the center screw of the double wall AL 29-4C® vent coupling, if
applicable.
VERTICAL INSTALLATION REQUIREMENTS
1. The vent system must terminate at least three (3) feet [1.0 m]
and no more than six (6) feet [2.0 m] above the roof line and no
closer than ten (10 ) feet [3.0 m] from any wall or vertical
structure. If the exhaust vent terminal is within 10’ (3.0 m) of a
wall or parapet, it must extend a minimum of 2’ (610 mm)
above the wall or parapet. See figures 9 and 11A.
2. Fordirect vent installations, thetotal distance ofthevent system
from the boiler vent connector to the vertical vent termination
shall not exceed ninety (90) equivalent feet [27.4 m]. A
maximum of three (3) 90° elbows can be used. Minimum
vertical vent is nine (9) equivalent feet [2.7 m] for direct vent
installations. For standard installations where no air intake
piping is included, the total distance can be extended to
180 equivalent feet [54.9 m] with a maximum of five (5)
90° degree elbows. Standard minimum vertical vent length is
five (5) feet [1.5 m]. See figures 9, 11A, 11B, and 11C for
differences between standard and direct vent installations.
3. An AL 29-4C®Vent Vertical Vent Terminal must be used at the
termination.
4. Maintain a minimum of six (6) feet [2.0 m] separation between
the air intake and the exhaust terminals.
HORIZONTAL INSTALLATION REQUIREMENTS
1. The vent system must terminate with a AL 29-4C®Vent
Through-the-Wall Termination (TWT). Plan the terminal
location based on the dimensions given in figure 8. Do not
locate the terminal within eight (8) feet (2.5 m) of an inside
corner of a building or adjacent to outside walls, shrubs or
other such objects that may cause adverse wind conditions in
the immediate area.
2. The TWT shall be located not less than 12 inches (305 mm)
above grade or, in geographical areas where snow
accumulates, no less than 12 inches (305 mm) above the
anticipated snow line. Ensure that the TWT is protected
against blockage which may occur during ice buildup or
snowstorms.
The TWT shall terminate at least three (3) feet [1.0 m] above
any forced air inlet within ten (10) feet [3.0 m], except when the
forced air inlet is the combustion air intake of a direct vent
appliance. The TWT shall terminate at least four (4) feet
[1.2 m] below, four (4) feet [1.2 m] horizontally from or one (1)
foot [305 mm] above any door, window or gravity air inlet into
any building as provided in the latest edition of the NATIONAL
FUEL GAS CODE ANSI Z223.1, see figure 8. For Canadian
installations consult CSA B149.1-00 (and latest addenda).
In addition, a minimum clearance of four (4) feet (1.2 m)
horizontallyfrom,and in NO CASEABOVEORBELOW, unless
the four (4) feet [1.2 m] of horizontal distance is maintained
from electric meters, gas meters, regulators and relief
equipment.
3. For direct vent installations, the total horizontal distance of the
vent system from the boiler vent connector to the outside of the

14
FIGURE 11. DIRECT VENT HORIZONTAL
FIGURE 11A. DIRECT VENT VERTICAL
CAUTION
Direct venting into dead air spaces such
as; alleys, atriums and inside corners can
cause recirculation of flue gases.
Recirculation of flue gases will cause
sooting, premature failure of the heat
exchanger and icing of the combustion
air intake during severe cold weather. To
prevent the recirculation of flue gases,
maintain as much distance as possible
between the combustion air intake and
the exhaust vent terminal.
NOTES: If the exhaust vent terminal is
within 10’ (3.0 M) of a wall or parapet, it
must extend a minimum of 2’ (610 MM)
above the wall or parapet.
Joints are not joined to show vent pipe
orientation.
NOTE: Joints are not joined to
show vent pipe orientation.

15
FIGURE 11B. DIRECT VENT, VERTICAL VENT TERMINATION WITH HORIZONTAL INTAKE
FIGURE 11C. DIRECT VENT USING TWT WITH VERTICAL INTAKE
CAUTION
Direct venting into dead air spaces such as; alleys,
atriums and inside corners can cause recirculation of
flue gases. Recirculation of flue gases will cause
sooting, premature failure of the heat exchanger and
icing of the combustion air intake during severe cold
weather. To prevent the recirculation of flue gases,
maintain as much distance as possible between the
combustion air intake and the exhaust vent terminal.
Option B (Figures 11B & 11C)
assures no recirculation of flue gases.
90 EQUIVALENT FEET (27.4M)
OF VENTING (MAX.) AL 29-4C
HORIZONTALAIR INTAKE
PVC PIPE 90
EQUIVALENT FEET(27.4M)
AIRINTAKETERMINAL
NOTES:
• IF THE EXHAUST VENT TERMINAL IS WITHIN 10’ (3.0M)
OF AWALLOR APARAPET, IT MIUST EXTEND AMINIMUM
OF 2’(0.6M)ABOVE THE WALL OR PARAPET.
• ON SIDEWALL VENT INSTALLATION, REFER
TO FIGURE 7 FOR SPACING SPECIFICATIONS
• FOR EXHAUSTANDAIR INTAKE PIPE INSTALLATIONS
(CLEARANCES, SUPPORT, ETC.) REFER TO FIGURES
11AND 11A.
VERTICALAIR INTAKE MUST BE
12”(305mm)ABOVEANTICIPATED
SNOW LEVEL.
PVC PIPE 90 EQUIVALENT FEET (27.4M)
90 EQUIVALENT FEET (27.4M)
OF VENTING (MAX.) AL 29-4C
NOTES:
• IF THE EXHAUST VENT TERMINAL IS WITHIN 10’ (3.0M)
OF AWALLOR APARAPET, IT MIUST EXTEND AMINIMUM
OF 2’(0.6M)ABOVE THE WALL OR PARAPET.
• ON SIDEWALL VENT INSTALLATION, REFER
TO FIGURE 8 FOR SPACING SPECIFICATIONS
• FOR EXHAUSTANDAIR INTAKE PIPE INSTALLATIONS
(CLEARANCES, SUPPORT, ETC.) REFER TO FIGURES
11AND 11A.

16
TWT shall not be greater than ninety (90) equivalent feet
[27.4 m] of vent pipe nor less than nine (9) feet [3 m] (excluding
fittings) unless the vent is through a non-combustible wall. A
maximum of three (3) 90° degree elbows may be used. For
standard installations where no air intake piping is included,
the total distance can be extended to 180 equivalent feet
[54.9 m] with a maximum of five (5) 90° degree elbows.
Standard minimum horizontal vent length is three (3) feet
[1.0m]. See figures 9Aand11 for differencesbetween standard
and direct vent installations.
4. This horizontal exhaust vent system must pitch upward toward
the termination at 1/4 inch per foot (21 mm per meter).
5. The TWT is designed such that the building is protected from
degradation by flue gas and condensate. However, if
additional protection is desired, install against the wall a
non-corrosive metal sheet under the TWT.
6. Due to the normal formation of water vapor in the combustion
process,horizontal terminations mustnot be locatedover areas
of pedestrian or vehicular traffic, (i.e., public walkways or over
areas where condensate could create a nuisance or hazard).
This is especially true in colder climates where ice buildup is
likely to occur. A.O. Smith Corporation will not be held liable
for any personal injury or property damage due to any
dislodging of ice.
DIRECT VENT INSTALLATION REQUIREMENTS
Follow the guidelines in the “HORIZONTAL INSTALLATION
REQUIREMENTS” section for the exhausting of flue products.
IMPORTANT
The labels in the Direct Vent Kit must be affixed to the boiler in
locations specified by the instruction sheet provided in the kit.
The following are requirements for the Air-Intake Terminal (AIT):
1. The Air-Intake System (AIS) must terminate with the venting
equipment provided with the boiler, see “DIRECT VENT KIT
PARTS LIST”, part no. 192109.
2. The AIT shall not be located less than three (3) feet [1.0 m]
below any exhaust vent within ten (10) feet [3.0 m], also see
“HORIZONTALINSTALLATION REQUIREMENTS” section.
3. The total horizontal distance of the AIS from the boiler’s Blower
Adapter to the outside of the “AIT” shall not be greater than
ninety (90) “equivalent” feet [27.4 m] of vent pipe nor less than
three (3) feet [1.0 m] (excluding elbows). A maximum of three
(3) elbows, equivalent to ten (10) feet (3.0 m) of pipe each may
be used.
SYSTEM INSTALLATION
GENERAL
If the system is to be filled with water for testing or other purposes
during cold weather and before actual operation, care must be
taken to prevent a downdraft entering the boiler or freezing air
from contacting the system. Failure to do so may cause the water
in the system to freeze with resulting damage to the system.
Damage due to freezing is not covered by the warranty.
Good practice requires that all heavy piping, etc., be supported.
Figure 12 shows a typical primary, secondary piping method.
This is the preferred piping method for most copper fin tube
boilers. Otherpiping methods, however, mayprovide good system
operation. A prime concern when designing heating systems is
the maintenance of proper flow through the unit during boiler
operation. The secondary pump should be sized per the
recommended flow rate of the boiler. (See recommended flow
charts on pages 2 and 3 of this manual.)
A system bypass should be installed as shown in fig. 12 to prevent
boiler circulation starvation when the system zones call for
reduced flow.
This bypass may also be used with multiple boilers manifolded
for reverse-return flow. This system bypass would be installed
from boiler outlet to suction side of pump.
HOT WATER HEATING (HYDRONIC) EQUIPMENT
The following is a brief description of the equipment required for
the installations noted in this manual. All installations must
comply with local code.
1. WATER SUPPLYLINE
These boilers can be used ONLY in a forced circulation hot
water heating system. Since most forced circulation systems
will be of the closed type, install the water supply line as shown
on piping diagram, figure 12.
Fast filling of large pipe, old radiator installations and pressure
purging of series loop systems (where high pressures are
not available) requires bypassing of the pressure reducing
valve.
Generally, pressure purging is not possible with a well pump
system. High point air venting is essential.
If the system is of the open type, a pressure reducing valve will
not be required as the water supply to the system will be
controlled by a manually operated valve. An overhead surge
tank is required. A minimum pressure of 15 psi (100 kPa)
must be maintained on the boiler at all times to ensure
avoidance of potential damage to the boiler which may not be
covered by the warranty.
2. EXPANSIONTANK
If the system is of the closed type, install an expansion tank as
shown in figure 12. The sizing of the expansion tank for a
closed system is very important and is directly related to the
total water volume of the system. Refer to “Systems and
Equipment” volume of the ASHRAE handbook.
An air separator as shown in the piping diagrams is
recommended especially for modern commercial hydronic
systems.
3. VENTVALVES
It is recommended that automatic, loose key or screw-driver
type vent valves be installed at each convector or radiator.
4. SYSTEMHEADERS
Split systems with individual supply and return lines from the
boiler room should normally have this piping connected to
supply and return manifold headers near the boiler. To achieve
good water distribution with maximum pressure drop for
several circuits, manifolds should be larger than system
mains.
The circuits should be spaced on the heater at a minimum of
3” (76 mm) center to center. Install a balancing cock in each
return line.

17
Manifold headers are recommended for split systems with or
without zone values and also those installations with zone
circulators. If the system is to be split at remote points, good
practice requires special attention be given to main pipe sizing
to allow balancing of water flow.
5. COOLINGPIPING
When the boiler is used in conjunction with a refrigeration
system it must be installed so that the chilled medium is piped
in parallel with the boiler. Appropriate flow control valves,
manual or motorized, must be provided to prevent the chilled
medium from entering the boiler.
Water temperature in the heating system must be reduced to
less than 100°F (38°C) before cooling system is started, or
damage to the chiller unit may occur.
If the boiler is connected to chilled water piping or its heating
coils are exposed to refrigerated air, the boiler piping system
must be equipped with flow valves or other automatic means
to prevent gravity circulation through the boiler during the
cooling cycle.
Primary/secondary pumping of both the chiller(s) and the
boiler(s) is an excellent winter-summer change-over method,
because cooling flow rates are so much more than heating
flow rates. In this way each system (heating or cooling) is
circulated independently.
6. CIRCULATING PUMP
FOR HOT WATER HEATING SYSTEMS - LB MODELS, the
circulating pump is NOT provided and must be field-installed.
NOTE: If a system pump is to be installed on a Legend LB
model, the maximum rating of the pump motor must not
exceed 1 hp.
INTERNAL CONTAMINANTS
The hydronic system must be internally cleaned and flushed after
a new or replacement boiler has been installed, to remove
contaminants that may have accumulated during installation. This
is doubly important when a replacement boiler is installed into
an existing system where Stop Leak or other boiler additives
have been used.
Failure to clean and flush the system can produce acid
concentrations that become corrosive, cause gases to form that
block water circulation or lead to formation of deposits on the
boiler surfaces, any of which could result in damage to the system
and circulator.
All hot water heating systems should be completely flushed with
a grease removing solution to assure trouble-free operation. Pipe
joint compounds, soldering paste, grease on tubing and pipe all
tend to contaminate a system
Failure to flush contaminants from a system can cause solids to
form on the inside of boiler exchangers, create excessive amounts
of air and other gases to block circulation, foul various system
accessories and even deteriorate circulation seals and impellers.
HOT WATER SUPPLY BOILER SYSTEM-
GENERAL WATER LINE CONNECTIONS
This section provides detailed installation diagrams for a typical
method of application for the unit.
Piping diagrams will serve to provide the installer with a reference
for the materials and methods of piping necessary for installation.
It is essential that all water piping be installed and connected as
shown on the diagrams. Check the diagrams to be used
thoroughly before starting installation to avoid possible errors
and to minimize time and material cost.
It is essential that all water piping be installed and connected as
shown on the diagrams. Check the diagrams to be used
thoroughly before starting installation to avoid possible errors
and to minimize the time and material cost.
FIGURE 12. TYPICAL PRIMARY, SECONDARY PIPING
• INSTALL IN ACCORDANCE WITH ALL LOCAL CODES.
• WHEN BLOW DOWN VALVE IS REQUIRED, INSTALL
IN PLACE OF THE DRAIN VALVE SHOWN.
DANGER
TEMPERATURESETTINGSHOULDNOTEXCEED
SAFE USE TEMPERATURE AT FIXTURES. SEE
WATERTEMPERATURECONTROLWARNING ON
PAGE28. IFHIGHERPREHEAT TEMPERATURES
ARE NECESSARY TO OBTAIN ADEQUATE
BOOSTEROUTPUT,ADDANANTI-SCALD VALVE
FORHOT WATER SUPPLIED TOFIXTURES.

18
DANGER
TEMPERATURESETTINGSHOULD NOTEXCEEDSAFEUSE
TEMPERATUREATFIXTURES. SEE WATERTEMPERATURE
CONTROL WARNING ON PAGE 28. IF HIGHER PREHEAT
TEMPERATURESARENECESSARYTOOBTAINADEQUATE
BOOSTEROUTPUT,ADDANANTI-SCALD VALVE FOR HOT
WATER SUPPLIEDTOFIXTURES.
ONE LEGEND (MODEL LW) HOT WATER SUPPLY BOILER WITH VERTICAL TANK
FIGURE13.
INSTALL THERMAL EXPANSION
TANK ON COLD WATER SUPPLY
LINE, IF CHECK VALVE OR
PRESSURE REDUCING VALVE IS
USED IN SUPPLY.
ONE LEGEND (MODEL LW) HOT WATER SUPPLY BOILER WITH HORIZONTAL TANK
DANGER
TEMPERATURESETTINGSHOULDNOT
EXCEED SAFE USE TEMPERATURE AT
FIXTURES. SEEWATER TEMPERATURE
CONTROL WARNING ON PAGE 28. IF
HIGHERPREHEATTEMP-ERATURESARE
NECESSARY TO OBTAIN ADEQUATE
BOOSTER OUTPUT, ADD AN ANTI-
SCALD VALVE FOR HOT WATER
SUPPLIEDTO FIXTURES.
INSTALLTHERMAL
EXPANSION TANK ON
COLD WATER SUPPLY
LINE, IF CHECK VALVE
OR PRESSURE
REDUCING VALVE IS
USED IN SUPPLY.
INSTALLINACCORDANCEWITHALLLOCALCODES.
PRESSURERELIEFVALVERATINGSHOULDNOTEXCEEDPRESSURE
CAPACITYOFANYCOMPONENTINTHESYSTEM.
INSTALLTEMPERATURE,PRESSUREGAUGEANDPRESSURERELIEFAS
CLOSETOBOILEROUTLETASPOSSIBLE.
SHUTOFFVALVES SHOULDBE INSTALLED FOR SERVICING BOILER,
LOCALCODESSHALLGOVERNTHEIRUSAGE.
SAFETY RELIEF VALVE SETTING SHOULD NOT EXCEED PRESSURE
RATINGOFANYCOMPONENTINTHESYSTEM.
STOPVALVESARESHOWNFORSERVICINGBOILER. HOWEVER,LOCAL
CODESSHALLGOVERNTHEIRUSAGE.
CAUTION: IF BUILDING COLD WATER SUPPLY HAS A BACKFLOW
PREVENTERCHECK VALVE OR WATER METER WITH CHECK VALVE,
PROVISIONSFORTHERMALEXPANSIONOFWATERINTHEHOTWATER
SYSTEMMUSTBEPROVIDED.
FIGURE14.

19
HARD WATER CONDITIONS
Wherehard water conditions exist,water softening orthe threshold
type of water treatment is recommended. This will protect the
dishwashers, coffee urns, water heaters, water piping and other
equipment. When water softening or water treatment is not
practical, a comparatively easy method of periodic lime removal
from the unit may be employed.
PRESSURE RELIEF VALVE RATING SHOULD NOT EXCEED
PRESSURECAPACITYOFANYCOMPONENTINTHE SYSTEM.
INSTALLTEMPERATURE,PRESSURE GAUGEANDPRESSURE
RELIEFAS CLOSETO BOILEROUTLET AS POSSIBLE.
SHUTOFF VALVES SHOULD BE INSTALLED FOR SERVICING
BOILER, HOWEVER, LOCAL CODES SHALL GOVERN THEIR
USAGE.
THERMAL EXPANSION (CLOSED SYSTEM)
Thermal expansion occurs in any hot water system when system
water is heated or “recovered” during periods of non-use.
If the system is operated in an “open” condition such as being
connected directly to the city main, the volume of expanded water
generated during the recovery periods can be dissipated back
through the “open” connection to the city main so pressure cannot
build up.
However, once a back flow preventer is installed to isolate system
water from the public supply; or a pressure reducing valve is
installed to protect a water meter; or any device preventing flow
back into the cold water supply, the “open” condition becomes
“closed”. During periods of temperature recovery and no usage,
expanded water has no place to go, so the pressure builds up
until a relief valve opens releasing hot water.
A relief valve opening on pressure will flow small amounts of
water, whereas relieving on temperature releases large amounts
of water.
If your system is closed, some provision must be made for
THERMAL EXPANSION to protect the system from excessive
pressure. Installan expansion tank thatis properly andadequately
sized for the expanding volume of water in the system.
Service problems or parts failure due to excessive pressure are
NOT covered under warranty.
TANK PROBE INSTALLATION PROCEDURE
A tank probe system temperature sensor is supplied with each
hot water supply boiler (LW models). When installed on a tank,
the inlet water temperature on the Dia-Scan II will default to the
tank temperature. See figure 21 and 22 for position of tank
probe jumper. As stated earlier, if one wishes to use an
alternative method of temperature control, this jumper must
be removed.
The tank probe sensor wires are run from the plug on the control
board to the junction box at the rear of the unit. Field wiring (in
conduit) is required from the plug wires to the tank probe sensor wires.
See figure 7.
TANK PROBE SET-POINT ADJUSTMENT
When the temperature sensor is installed in a water tank, and
the sensor is used with the WHC1502 system, the controller will
monitor and control the temperature of the water at the sensor
location. Setting the temperature is accomplished through the
Dia-ScanII control display. Theprogrammable temperature range
is 110°F to 190°F (43°C to 88°C). The switching differential is
fixed at 5°F (3°C).
GAS CONNECTIONS
CAUTION
MAKESURETHEGASONWHICHTHEBOILERISTOOPERATEIS
THESAMEASTHATSPECIFIEDONTHERATINGPLATE. DONOT
INSTALLTHEBOILERIFEQUIPPEDFORADIFFERENTTYPEOF
GAS.CONSULTYOURGASSUPPLIER.
THISBOILER IS NOT INTENDED TOOPERATEAT GAS SUPPLY
PRESSURE OTHER THAN SHOWN ON THE RATING PLATE. A
LOCK-UPORPOSITIVESHUT-OFF TYPEREGULATORMUSTBE
INSTALLEDIN THE GASSUPPLYLINE. EXPOSURE TOHIGHER
GASSUPPLYPRESSUREMAYCAUSEDAMAGETOGASVALVES
WHICHCANRESULTINFIREOREXPLOSION. IFOVERPRESSURE
HASOCCURRED SUCH ASTHROUGHIMPROPER TESTING OF
GAS LINES OR EMERGENCY MALFUNCTION OF THE SUPPLY
SYSTEM, THE GAS VALVES MUST BE CHECKED FOR SAFE
OPERATION. MAKE SURETHATTHE OUTSIDE VENTS ON THE
SUPPLY REGULATORSAND THE SAFETY VENT VALVES ARE
PROTECTEDAGAINSTBLOCKAGE. THESEAREPARTSOFTHE
GASSUPPLYSYSTEM,NOTTHEBOILER.VENTBLOCKAGEMAY
OCCURDURINGICE BUILD-UPOR SNOWSTORMS.
THE BOILER MUST BE ISOLATED FROM THE GAS SUPPLY
PIPING SYSTEM BY CLOSING ITS MAIN MANUAL GAS
SHUT-OFFVALVEDURINGANYPRESSURETESTINGOFTHEGAS
SUPPLYPIPING SYSTEMAT TEST PRESSURES EQUALTO OR
LESSTHAN 1/2 PSIG.
DISCONNECTTHE BOILERAND ITS MAIN MANUALGASSHUT-
OFF VALVE FROM THE GAS SUPPLY PIPING DURING ANY
PRESSURE TESTING OF THE GAS SUPPLY SYSTEM OVER
1/2PSIG. THEGASSUPPLYLINEMUSTBECAPPEDWHENNOT
CONNECTEDTOTHEBOILER.
IT IS IMPORTANT TO GUARDAGAINST GAS VALVE FOULING
FROMCONTAMINANTSINTHEGASWAYS. SUCHFOULING MAY
CAUSEIMPROPEROPERATION,FIREOREXPLOSION. IFCOPPER
SUPPLYLINESAREUSEDTHEYMUSTBEAPPROVEDFORGAS
SERVICE.
WHEN LOCAL CODES REQUIRE A MAIN MANUAL SHUT-OFF
VALVE OUTSIDE THE BOILER JACKET, A SUITABLE MAIN
MANUALSHUT-OFFVALVEMUSTBEINSTALLEDINALOCATION
COMPLYING WITHTHOSECODES.
BEFOREATTACHING THE GAS LINE BE SURE THATALL 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)
MUST BE INCORPORATED IN THE PIPING. THE DIRT LEG
MUST BE READILY ACCESSIBLE AND NOT SUBJECT TO
FREEZING CONDITIONS. INSTALL IN ACCORDANCE WITH
RECOMMENDATIONSOF SERVINGGASSUPPLIER.REFERTO
NATIONALFUELGAS CODE,ANSIZ223.1OR CAN/CSA–B149.1-
00(AND LATESTADDENDA).

20
Size of gas supply piping may be larger than heater connection
on installations where a significant run of piping is required.
To prevent damage, care must be taken not to apply too much
torque when attaching gas supply pipe to boiler gas inlet.
Fittings and unions in the gas line must be of the 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.
GASSUPPLYLINESIZING
The gas piping installation must be capable of supplying the
maximum probable gas demand without excessive pressure
loss. Depending on local practices, theALLOWABLE PRESSURE
LOSS between the gas meter, or service regulator and each
appliance is generally 0.3 or 0.5 inches of water column
( 0.075 or 0.124 kPa).
For single boiler installation, refer to table 6 to size iron pipe or
equivalent gas supply line size to be used with single unit.
For multiple boiler installation or installations of a single boiler
with other gas appliances please refer to tables 7 and 8 to size
iron pipe or equivalent gas supply line. These tables are taken
from ANSI Z223.1 NATIONAL FUEL GAS CODE, or
CAN/CSA – B149.1 - 00 (and latest addenda):
•Table 7 is based on a pressure drop of 0.5 inches water
column (0.124 kPa), and a gas with a specific gravity of 0.60
and a heating value of 1,000 BTU/ft3, approximately that of
Natural Gas.
•Table 8 is based on a pressure drop of 0.5 inches water
column (0.124 kPa), and a gas with a specific gravity of 1.53
and a heating value of 2,500 BTU/ft3, approximately that of
Propane Gas.
No additional allowance is necessary for an ordinary number of
fittings. Where it is necessary to use more than the average
number of fittings (i.e., elbows, tees and valves in gas supply
line) use a pipe larger than specified to compensate for increased
pressure drop.
TABLE 6.
SINGLE UNIT INSTALLATION, SUGGESTED GAS PIPE SIZING.
MAXIMUM EQUIVALENT PIPE LENGTH (IN FEET).
Btu 1-1/4" 1-1/2" 2" 2-1/2"
Input Nat. Prop. Nat. Prop. Nat. Prop. Nat. Prop.
500,000 40 90 80 200 — — — —
750,000 10 40 40 90 125 — — —
1,000,000 —- 20 20 50 70 175 175 —
Natural gas 1000 Btu/ft^3, 0.60 specific gravity @ 0.3 in. w.c. pressure drop
Propane gas 2500 Btu/ft^3, 1.50 specific gravity @ 0.3 in. w.c. pressure drop.
Table 6 shows the maximum equivalent gas pipe length for a
single unit installation. It does not take into account other
appliances that may be connected to the gas line. For installation
of multiple units, or instances where several appliances are
connected to the same line, use tables 7 and 8 for proper sizing.
WIRING
CAUTION
LABEL ALL WIRES PRIOR TO DISCONNECTION WHEN
SERVICING CONTROLS. WIRING ERRORS CAN CAUSE
IMPROPERANDDANGEROUSOPERATION.FIGURE 15. GAS MANIFOLDS
LB/LW - 1000 NATURAL GAS
LB/LW-500 NATURAL & PROPANE GAS
LB/LW - 750 & 1000 PROPANE GAS
LB/LW-750 NATURAL GAS
FIELD INSTALLED
MAIN MANUAL GAS SHUT-OFF VALVE, DRIP LEG & UNION