A.O. Smith 402, 401, 404, 403, 405 User Manual

COPPER BOILERS FOR

HYDRONIC HEATING AND

HOT WATER SUPPLY

• Installation

• Operation

• Maintenance

• Limited Warranty

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
vicinity of this or any other appliance.

WHAT TO DO IF YOU SMELL GAS:

• Extinguish any open flame.

• 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.

Instruction Manual

GB/GW MODELS:

1000, 1300, 1500, 1850, 2100, 2500

SERIES: 400, 401, 402, 403, 404, 405

CAUTION

TEXT PRINTED OR OUTLINED IN RED CONTAINS
INFORMATION RELATIVE TO YOUR SAFETY.
PLEASE READ THOROUGHLY BEFORE INSTALLING
AND USING THIS APPLIANCE.

for buying this cost

Thank You

You should thoroughly read and understand this
manual before installation and/or operation of this
boiler. Please pay particular attention to the
important safety and operating instructions as well
as the WARNINGS and CAUTIONS.

CONTENTS P AG E

DIMENSIONS/CAPACITIES DA T A .......................... 2 - 3

FOREWORD......................................................... 4 - 5

FEATURES/CONTROLS..................................... 5 - 7

INSTALLA TION INSTRUCTIONS ....................... 7 - 9

VENTING ........................................................... 9 - 11

SYSTEM INSTALLATION ................................ 11 - 16

HYDRONIC INSTALLA TION ............................ 16 - 18

HOT WATER SUPPLY INSTALLATION ........... 18 - 31

GAS CONNECTIONS...................................... 18 - 23

OPERATION.................................................... 31 - 34

LIGHTING AND OPERATING .......................... 32 - 33

CONTROL SYSTEM ....................................... 34 - 44

PREVENTATIVE MAINTENANCE.................. 44 - 46

TROUBLE SHOOTING .................................... 42 - 44

WIRING DIAGRAM/SCHEMATIC ................... 24 - 27

LIMITED WARRANTY ............................................. 47

efficient, high recovery unit from

A. O. Smith Water Products Co.

PLACE THESE INSTRUCTIONS ADJACENT TO BOILER AND

NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.

PRINTED IN U.S.A. 0906

MC BEE, SC., RENTON, WA.,

STRATFORD-ONTARIO, VELDHOVEN-THE NETHERLANDS,

NANJING, CHINA

ww w.hotwater.com / email:[e-mail]

1

212511-000

DIMENSIONS/CAP ACITIES DAT A

TOP VIEW

FRONT VIEW

IMPORT ANT!

Refer to "Installation Clearances" section of manual
(page 7) for recommended service clearances prior
to boiler placement.

LEFT SIDE

REAR VIEW

TABLE 1: GAS AND ELECTRICAL REQUIREMENT

Manifold Pressure Electrical Characteristics

MODEL Type of Gas Inches W.C. kPa Volts/Hz Amperes

GW/GB-1000

thru 2500 NATURAL 3.5 0.87 120/60 30

GW/GB-1000

thru 2500 PROPANE 10 2.49 120/60 30

All Models - Maximum Supply Pressure: 14.0 In. W.C. (3.49 kPa)
Minimum Supply Pressure Natural Gas: 6.0 In. W.C. (1.22 kPa)
Minimum Supply Pressure Propane Gas: 1 1.0 In. W.C. (2.74 kPa)
Minimum Pressures must be maintained during operating conditions.

Figure 1.

T ABLE 2. DIMENSIONAL DA T A

ABCD EF

Model Inches c m Inches c m Inches cm Inches c m Inches cm Inches cm

GW/GB-1000 14.1 35.8 12.2 31.0 40.3 102.4 31.6 80.3 26.0 66.0 46.8 118.9
GW/GB-1300 24.8 63.0 12.2 31.0 40.3 102.4 31.6 80.3 39.3 99.8 57.3 145.5
GW/GB-1500 30.2 76.7 12.2 31.0 40.3 102.4 31.6 80.3 44.6 113.3 64.3 163.3
GW/GB-1850 27.7 70.4 11.2 28.4 43.0 109.2 32.3 82.0 44.0 111.8 78.3 198.9
GW/GB-2100 31.0 78.7 11.2 28.4 43.0 109.2 32.3 82.0 49.5 125.7 85.3 216.7
GW/GB-2500 38.1 96.8 10.5 26.7 43.0 109.2 32.3 82.0 56.5 143.5 99.3 252.2

Input Rating Exhaust Air Intake

Model Natural Gas Natural Gas Propane Gas Propane Gas Inches cm Inches c m Size

GW/GB-1000 990,000 289.95 990,000 289.95 10 25.4 8 20.3 2 1/2 NPT 2 NPT
GW/GB-1300 1,300,000 380.74 1,300,000 380.74 12 30.5 10 25.4 2 1/2 NPT 2 NPT
GW/GB-1500 1,500,000 439.31 1,500,000 439.31 12 30.5 10 25.4 2 1/2 NPT 2 NPT
GW/GB-1850 1,850,000 541.82 1,850,000 541.82 14 35.6 10 25.4 2 1/2 NPT 2 1/2 NPT
GW/GB-2100 2,100,000 615.04 2,100,000 615.04 14 35.6 12 30.5 2 1/2 NPT 2 1/2 NPT
GW/GB-2500 2,490,000 729.26 2,490,000 729.26 16 40.7 12 30.5 2 1/2 NPT 2 1/2 NPT

BTU/Hr. KW BTU/Hr. KW Vent Diameter Diameter Water Conn. Gas Inlet

2

DIMENSIONS DA TA FOR OUTDOOR CONFIGURATION

REAR VIEW

FRONT VIEW

LEFT SIDE

TOP VIEW

Figure 2.

T ABLE 3. DIMENSIONAL DA TA

AB C D E F G HJ

Model Inches cm Inches cm Inches cm Inches cm Inches cm Inches cm Inches cm Inches cm Inches cm

GBO/GWO-1000 14 35.5 31.6 80.3 71.8 182.4 15.5 39.4 39.75 101 58.25 148 15.9 40.83 16 40.64 46.8 118.9
GBO/GWO-1300 24.75 62.9 31.6 80.3 82 208.3 15.5 39.4 39.75 101 58.25 148 15.9 40.83 16 40.64 57.3 145.5
GBO/GWO-1500 30 76.2 31.6 80.3 89 226 15.5 39.4 39.75 101 58.25 148 15.9 40.83 16 40.64 64.3 163.3
GBO/GWO-1850 27.5 69.9 32.3 82 103 261.6 18.9 48 43 109.2 61.5 156.2 23.9 60.7 20 50.8 78.3 198.9
GBO/GWO-2100 31 78.7 32.3 82 110 279.4 18.9 48 43 109.2 61.5 156.2 23.9 60.7 20 50.8 85.3 216.7
GBO/GWO-2500 38 96.5 32.3 82 124 315 18.9 48 43 109.2 61.5 156.2 23.9 60.7 20 50.8 99.3 252.2

3

TABLE 4: RECOVERY CAPACITIES

TEMPERATURE RISE - DEGREES °F (°C)

Input Rating Water 40°F 50°F 60°F 70°F 80°F 90°F 100°F 110°F 120°F 130°F

MODEL BTU/Hr. (kW) Flow (22.2°) (27.7°) (33.3°) (38.8°) (44.4°) (50°) (55.5°) (61.1°) (66.7°) (72.2°)

GW - 1000 990,000 (290.1) GPH 2520 2016 1680 1440 1260 1120 1008 916 840 775

LPH 9526 7620 6350 5443 4763 4234 3810 3462 3175 2930

GW - 1300 1,300,000 (380.9) GPH 3309 2647 2206 1891 1655 1471 1324 1203 1103 1018

LPH 12508 10006 8339 7148 6256 5560 5005 4547 4169 3848

GW - 1500 1,500,000 (439.5) GPH 3818 3055 2545 2182 1909 1697 1527 1388 1273 1175

LPH 14432 11548 9620 8248 7216 6415 5772 5247 4812 4442

GW - 1850 1,850,000 (542.0) GPH 4709 3767 3139 2691 2355 2093 1884 1712 1570 1449

LPH 17800 14239 11865 10172 8902 7912 7122 6471 5935 5477

GW - 2100 2,100,000 (615.3) GPH 5345 4276 3564 3055 2673 2376 2138 1944 1782 1645

LPH 20204 16163 13472 11548 10104 8981 8082 7348 6736 6218

GW - 2500 2,490,000 (729.6) GPH 6338 5071 4225 3622 3169 2817 2535 2305 2113 1950

LPH 23958 19168 15971 13691 11979 10648 9582 8713 7987 7371

TABLE 5: PUMPING PERFORMANCE GUIDE

GB MODELS-FLOW, HEAD LOSS AND TEMPERA TURE RISE

20 Deg. F Rise 30 Deg. F Rise 40 Deg. F Rise Maximum Flow Rate Minimum Flow Rate
GPM PD-FT G PM PD-FT G PM PD-FT GPM PD-FT Deg. F GPM PD-FT Deg. F

MODEL Head Head Head Head Rise Head Rise
GB - 1000 83 5.1 55 2.7 41.6 1.5 1 5 4 12.2 11 42 1.5 40
GB - 1300 109 7.2 72.8 4.2 54.6 3.2 154 14.5 1 4 55 3.2 40
GB - 1500 126 10.1 84 6.3 6 3 4.3 154 16.3 17 64 4.3 40
GB - 1850 154 18.5 103.6 10.1 77.7 6.4 15 4 18.5 20 78 6.4 40
GB - 2100 n/a n/a 117.6 14.5 88 8.3 154 21.3 2 3 89 8.3 40
GB - 2500 n/a n/a 139.4 18.5 104.6 11.6 154 23.2 28 105 11.6 40

Note: GW models (GB optional) are equipped with pumps capable of handling 50 equivalent feet

(15.2 m) of normal pipe fittings.

FOREWORD

Detailed installation diagrams are in this manual. These diagrams
will provide the installer with a reference of materials needed and a
suggested method of piping. IT IS NECESSARY THAT ALL W ATER
AND GAS PIPING , AND THE ELECTRICAL WIRING BE INST ALLED
AND CONNECTED AS SHOWN IN THE DIAGRAMS.

CHECK DIAGRAMS THOROUGHLY BEFORE STARTING
INSTALLATION TO AVOID POSSIBLE ERRORS AND MINIMIZE
TIME AND MA TERIALS COST. SEE FIGURES 1 THROUGH 5 AND
TABLES 1, 2, AND 3.

This design complies with the current edition of ANSI Z21.13-CSA

4.9 for Gas-Fired Low-Pressure Steam and Hot Water Boilers.

MAKE SURE THE GAS ON WHICH THE BOILER WILL OPERATE
IS THE SAME AS THAT SPECIFIED ON THE BOILER RATING
PLATE.

The boiler installation must conform to these instructions and the
local code authority having jurisdiction. In the absence of local
codes, the installation must comply with the latest editions of
the National Fuel Gas Code, ANSI Z223.1/NFPA 54 and the
National Electrical Code, NFPA 70 or CAN/CSA B149.1, and CSA
2 C22.1. The former is available from the Canadian Standards
Association, 8501 East Pleasant Valley Road, Cleveland, OH
44131, and both documents are available from the National Fire
Protection Association, 1 Batterymarch Park, Quincy, MA 02269.

4

GROUNDING INSTRUCTIONS

This boiler must be grounded in accordance with the National
Electrical Code, NFPA 70 or the Canadian Electrical Code CSA 2
C22.1

and/or local codes. The 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.

WARNING

YOUR BOILER IS NOT DESIGNED TO OPERA TE WITH A BOILER
INLET WATER TEMPERATURE OF LESS THAN 120°F (49°C).
COLDER INLET WATER TEMPERATURE 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 PREMA TURE DAMAGE, WHICH COULD
RESULT IN SERIOUS PERSONAL INJUR Y OR DEATH.

FOR SYSTEMS THAT USE LARGE VOLUMES OF COLD WATER
OR SYSTEMS UTILIZING HEA VY WA TER DRAWS, CONDENSA TION
CAN BE PREVENTED BY USING A BYP ASS LOOP.

CORRECT GAS

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. IF YOU EXPERIENCE AN OUT OF GAS
SITUATION, DO NOT TRY TO RELIGHT APPLIANCES YOURSELF .
Call your local service agent. Only trained LP professionals should
conduct the required safety checks in accordance with industry
standards.

HIGH AL TITUDE INST ALLATION

WARNING

INSTALLATIONS ABOVE 4,500 FEET REQUIRE REPLACEMENT
OF THE BURNER ORIFICES. FAILURE TO REPLACE THE
ORIFICES WILL RESULT IN IMPROPER AND INEFFICIENT
OPERATION OF THE APPLIANCE, PRODUCING CARBON
MONOXIDE GAS IN EXCESS OF SAFE LIMITS, WHICH COULD
RESULT IN SERIOUS PERSONAL INJURY OR DEATH.

GENESIS BOILERS ARE EQUIPPED WITH SELF-REGULATING
PREJET ORIFICES WHICH AUT OMATICALL Y COMPENSATE FOR
HIGHER ELEVATIONS AND ADJUST THE APPLIANCE'S INPUT
RA TE ACCORDINGL Y, MAKING IT UNNECESSARY TO REPLACE
ORIFICES FOR HIGH ALTITUDE (UP TO 4,500 FEET). CONSUL T
THE FACTOR Y FOR HIGHER ALTITUDES.

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 of gas, consult your gas supplier.

PRECAUTIONS

IF THE UNIT IS EXPOSED TO THE FOLLOWING, DO NOT
OPERA TE UNTIL ALL CORRECTIVE STEPS HA VE BEEN MADE BY
A QUALIFIED SERVICEMAN:

1. EXPOSURE TO FIRE.

2. IF DAMAGED.

3. FIRING WITHOUT WA TER.

4. SOOTING .

IF THE BOILER HAS BEEN EXPOSED TO FLOODING, IT MUST BE
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.

Some utility companies derate their gas for altitude. You should
contact your gas supplier for any specific changes which may be
required in your area. Call the local gas utility to verify BTU content
of the gas supplied.

Input rating specified on the rating plate applies to elevations up to
4,500 feet (1350 m). For elevations above 4,500 feet (1350 m),
ratings must be reduced, consult the factory.

FEATURES/CONTROLS

MUL TI-ST AGE FIRING AND CONTROL SYSTEM

ALL MODELS - The control system consists of four basic
components: 1) Central Control Board 2) Flame Control Board 3)
User Interface Module 4) Power Distribution Board; see Figures
17, 18, 19 and 21. The Central Control Board, Flame Control
Boards and the Power Distribution Board are located in the
control box and can be accessed through panels on the left side
and top of the unit. The User Interface Module is attached to the
front jacket panel. The control system is a multi-stage control
capable of managing three or four firing stages. Models 1000,
1300, and 1500 operates with 3-stage fire. Models 1850, 2100
and 2500 operates with 4-stage fire. Every system will have one
Central Control Board (CCB), one Power Distribution Board
(PDB), one User Interface Module (UIM) and either two or three
Flame Control Boards (FCB) depending on the model.

The Control Boards Figure 17 and 18, contain dipswitches which
allow the user to control several system options. See Control System
Section.

5

DIFFERENTIAL PRESSURE SWITCH

COMBUSTION AIR BLOWER

The differential pressure switch ensures that a sufficient differential
exists between the air pressure in the pre-mix chamber and the inlet
of the burner for safe, combustion and proper low NOx emission. The
switch has two pressure taps marked "+" (positive) and "-" (negative).
Silicone tubing is run from the positive pressure tap of the switch to a
tap on the control panel to measure the air pressure in the pre-mix
chamber. The negative pressure tap measures the pressure taken at
the burner's auxiliary tube. Connections can be seen by removing the
lower front jacket panel. It is important that this panel remain sealed
at all times while the boiler is operating.

The differential pressure switch is normally open and closes when
the combustion blower starts.

BLOCKED FLUE PRESSURE SWITCH

The blocked flue pressure switch ensures that the vent system is
clear. This pressure switch is normally closed and only opens on
fault conditions.

FLAME SENSOR

The flame sensor detects the flame presence on burner's ports. If
no flame is sensed, the gas valve(s) will close automatically. If no
flame is sensed on three ignition trials the boiler will lock out. In the
event of a lockout, depress the SELECT button on the UIM to restart
the boiler.

WA TER FLOW SWITCH

Provides air for combustion process. The blower settings are
adjustable through the use of the air shutter, however, blowers are
set at the factory and might require slight adjustment depending
on site installation.

T ANK PROBE

FOR HOT WA TER SUPPLY SYSTEMS (GW models), a tank probe

is supplied with each hot water supply boiler.
Note: The tank probe must be designated as the controlling probe

using dip switch "4" on Central Control Board (Figure 17) before it
can be used for (GW) hot water supply applications.

"Pigtails" of field-supplied wires should be spliced to "pigtails" of
tank probe and connected to terminal block in the 24VAC junction
box. See Figure 12 for the tank probe installation. Follow the
instructions in the "TANK PROBE INSTALLATION PROCEDURE".
See page 18.

FOR HOT WA TER HEA TING SYSTEMS (GB models), a t ank probe
is not supplied with the GB models due to the many various
types of systems and operating conditions. A tank probe can
be used as an option to control loop temperature and unit
staging. Additionally, the inlet temperature probe can be used
as the loop thermostat in some heating applications. The tank
probe connects to designated wires in the junction box at the
rear of the boiler. Do not operate this boiler using the internal

high limits only, use a tank probe or operating thermostat to
control system temperatures.

The water flow switch is installed at the boiler outlet to prevent burner
operation in the event of inadequate water flow through the boiler. It
is a normally open switch that will close its contacts when increasing
water flow rate is detected. The water flow switch is factory-set, but
may require field adjustment. The contacts will open when the flow
rate drops below the adjusted setting causing the gas valve(s) to
close which will turn off the gas to the burners.

LIMIT CONTROLS

CAUTION

LIMIT CONTROLS ARE SAFETY DEVICES AND ARE NOT TO BE
USED AS AN OPERATING CONTROL (THERMOSTA T).

The "G(B/W)" models incorporate an outlet water probe consisting
of two limit controls:

1. An adjustable automatic reset limit control, that can be set
as high as either 210°F (99°C) or 235°F (113°C) depending on
the application.

2. A fixed manual reset limit (ECO) factory set at 244°F
(118°C). If the manual reset should open due to high
temperature, the gas valves will close and the unit will go into
lockout. If lockout occurs, push the SELECTION button on the
UIM to restart the boiler.

ON/OFF SWITCH

The ON/OFF switch is a single-pole, single-throw rocker switch.
The switch provides 120VAC from the line source to the boiler.

Note: The tank probe or additional 24V AC devices must be identified
using Dipswitches on Central Control Board before they are
recognized as a part of the heating system; see Table 5. Refer to
"Control System" section for more information about dipswitch
settings.

CIRCULA TING PUMP

The pump flow rate should not exceed the maximum
recommended flow rate; see Table 5.

FOR HOT WA TER SUPPLY SYSTEMS (GW models), ordered with
the circulator as an integral part of the boiler; the pump has been
lubricated at the factory, and future lubrication should be in
accordance with the motor manufacturer's instructions provided
as supplement to this manual.

FOR HOT WA TER HEA TING SYSTEMS (GB models or GW models
ordered without circulator), the circulator is NOT provided and

must be field-installed.

LOW WA TER CUT OFF (Not Supplied)

If low water level 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
"HYDRONIC INSTALLATION" section; see page 16. 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.

6

DRAIN V ALVE (Not Supplied)

Additional drain valves must be obtained and installed on each boiler
and tank for draining purposes.

SAFETY RELIEF V AL VES

side of the tank on a center line within the upper six (6) inches
(15 cm) of the top of the tank. 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.

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 T ANK EXPLOSION,
SYSTEM OR BOILER DAMAGE.

TO AVOID W A TER DAMAGE A DRAIN LINE MUST BE CONNECTED
TO A SAFETY RELIEF V AL VE FOR DIRECT DISCHARGE TO A SAFE
LOCATION. A DRAIN LINE MUST NOT BE REDUCED FROM THE
SIZE OF THE V ALVE OUTLET AND IT MUST NOT CONT AIN ANY
VALVES BETWEEN THE BOILER AND THE RELIEF VALVE OR
THE RELIEF VAL VE 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 . RESTRICTING OR BLOCKING A DRAIN LINE
WILL DEFEAT THE PURPOSE OF THE RELIEF VALVE AND MA Y
CREATE AN UNSAFE CONDITION. INST ALL 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 set
pressure NOT exceeding the working pressure of any component
in the system.

The storage tank temperature and pressure relief valve must
comply with the applicable construction provisions of the Standard
for Relief V alves for Hot W ater Supply Systems, ANSI Z21.22-CSA-

4.4 (current edition). The valve must be of the automatic reset type
and not embody a single-use type fusible plug, cartridge or linkage.

FOR HOT WATER HEATING SYSTEMS, the boilers are shipped
with a 50 psi pressure relief valve. This relief valve is factory
installed on the water outlet header of the boiler.

FOR HOT WATER SUPPLY SYSTEMS, the boilers are shipped
with a 125 psi pressure relief valve. This relief valve is factory
installed on the water outlet header of the boiler. This ASME-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 every water
storage tank in the hot water supply system; see
Figures 11 and 13.

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

INST ALLATION INSTRUCTIONS

REQUIRED ABILITY

INST ALLATION OR SER VICE OF THIS BOILER REQUIRES ABILITY
EQUIV ALENT TO THA T OF A LICENSED TRADESMAN IN THE FIELD
INVOLVED. PLUMBING, AIR SUPPL Y , VENTING, GAS SUPPLY AND
ELECTRICAL WORK ARE REQUIRED.

LOCA TION

When installing the boiler, consideration must be given to proper
location. The 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. The 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 INST ALLED ON CARPETING.

• THE BOILER SHOULD NOT BE LOCATED IN AN AREA WHERE
IT WILL BE SUBJECT TO FREEZING.

• THE BOILER SHOULD BE LOCATED 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 T O LOWER
FLOORS OF THE STRUCTURE.

WHEN SUCH LOCATIONS CANNOT BE AVOIDED, A SUITABLE
DRAIN PAN SHOULD BE INST ALLED UNDER THE BOILER. Such
pans should be fabricated with sides at least 2-1/2" (6.5 cm) deep,
with length and width at least 2" (5.1 cm) 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, OPERA TED OR REP AIRED. FLAMMABLE VAPORS ARE
HEAVY AND TRAVEL ALONG THE FLOOR AND MAY BE IGNITED
BY THE IGNITER OR MAIN BURNER FLAMES CAUSING FIRE OR
EXPLOSION. SOME LOCAL CODES PERMIT OPERA TION OF GAS
APPLIANCES IF INSTALLED 18 INCHES (46.0 CM) OR MORE
ABOVE THE FLOOR. THIS MA Y REDUCE THE RISK IF LOCA TION
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.

A hot water boiler installed above radiation level or as required by

7

the authority having jurisdiction, must be provided with a low water
cutoff device either as a part of the boiler or at the time of boiler
installation.

WARNING

UNDER NO CIRCUMST ANCES SHOULD THE EQUIPMENT ROOM
WHERE THE BOILER IS INSTALLED EVER BE UNDER NEGA TIVE
PRESSURE. PARTICULAR CARE MUST BE TAKEN WHEN
EXHAUST FANS, COMPRESSORS, AIR HANDLING EQUIPMENT,
ETC., MAY INTERFERE WITH THE COMBUSTION AND
VENTILA TION AIR SUPPLIES OF THIS BOILER.

CHEMICAL V APOR 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 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.

INST ALLATION CLEARANCES

Sufficient area should be provided at the front and sides of the
unit for proper servicing. For ease of service, minimum
clearances of 24" (61.0 cm) in the front and 18" (46.0 cm) on
the sides are recommended. It is important that the minimum
clearances be observed to allow service to the control box and
other controls. Observing proper clearances will allow service to

be performed without movement or removal of the boiler from its
installed location. Failure to observe minimum clearances may
require removal of the boiler in order to service such items as the
heat exchanger and burners. 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.

Two inch (5.1 cm) clearance is allowable from combustible
construction to hot water pipes. Sufficient clearance should be
provided at one end of the boiler to permit access to heat exchanger
tubes for cleaning.

Access to control box items such as the Central Control Board,
Flame Control Boards, Power Distribution Board and wiring
harnesses is provided through a panel on the left side of the unit.
A minimum service clearance of 18" (46.0 cm) is required.

MODEL COMBUSTIBLE BASE KIT NUMBER

G(B,W) - 1000 211093
G(B,W) - 1300 211093-1
G(B,W) - 1500 211093-2
G(B,W) - 1850 211093-3
G(B,W) - 2100 211093-4
G(B,W) - 2500 211093-5

Figure 3. Boiler on Combustible Floor Base and Kit Numbers.

LEVELLING

Each unit must be checked after installation to be ce rtain that it is level.

AIR REQUIREMENTS

WARNING

FOR SAFE OPERATION, AN AMPLE SUPPLY OF AIR MUST BE
PROVIDED FOR PROPER COMBUSTION AND VENTILATION IN
ACCORDANCE WITH THE NATIONAL FUEL GAS CODE, ANSI
Z223.1 OR CAN/CSA-B149.1 CURRENT EDITION 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, OR CREATE A RISK OF
ASPHYXIATION. DO NOT OBSTRUCT THE FLOW OF
COMBUSTION AND VENTILATION AIR.

UNCONFINED SP ACE

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, must be obtained from outdoors 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.

These boilers are approved for installation on noncombustible
flooring in an alcove with minimum clearance to combustibles of:
3 inches (7.6 cm) Right Side, and Back; 6 inches (15.2 cm) Top;
Front, Alcove; 12 inches (30.5 cm) Left Side; and 6 inches
(15.2 cm) surrounding the Vent.

For installation on combustible flooring use the Combustible Floor
Kit. The combustible floor kit base adds 4" (10.1 cm) to the overall
height of the boiler. See Figure 3.

CONFINED SP ACE

(a) U. S. INST ALLATIONS

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
WITHIN 12 INCHES OF THE ENCLOSURE TOP AND ONE WITHIN
12 INCHES OF THE ENCLOSURE BOTTOM. Each opening shall
have a free area of at least one square inch per 1000 Btu/hr
(22 cm2/k W) of the total input of all appliances in the enclosure.

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 above manner,
shall be provided. Each opening shall have a free area of not less
than one square inch per 4000 Btuh (5.5 cm

2

/kW) of the total input
of all appliances in the enclosure. If horizontal ducts are used, each
opening shall have a free area of not less than one square inch per
2000 Btuh (11 cm

2

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

enclosure.

(b) CANADIAN INSTALLA TIONS

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
(64.5 cm

2

).

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 (3.2 cm

2

/kW) up to and including 1,000,000
BTUH plus 1 square inch per 14,000 BTU (1.6 cm2/kW) in excess of
1,000,000 BTUH. This opening(s) shall be located at, or ducted to,
a point neither more than 18" (46.0 cm) nor less than 6 inches (15.2
cm) 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 DRA WN INTO
THE ROOM THROUGH THE CHIMNEY, CAUSING POOR
COMBUSTION. SOOTING MAY RESULT WITH AN INCREASED
RISK OF ASPHYXIA TION.

SEE FIGURE 6). AT LEAST TYPE B VENTING MUST BE USED
WITH THE STANDARD VENTING OPTION (thru-the-roof) USING
THE NA TIONAL FUEL GAS CODE VENT TABLES. TYPE B VENT

CANNOT BE USED IF THE BOILER IS VENTED

PIPE
HORIZONTALLY OR AS A DIRECT VENT (SEE PAGES 12
THROUGH 15). ALL LOCAL UTILITY, STATE/ PROVINCIAL,
REGULATIONS ON VENTING MUST BE FOLLOWED.

VENT SIZING, VENT CONNECTORS, INSTALLATION AND
TERMINATION SHALL BE IN ACCORDANCE WITH THE CURRENT
EDITION OF

NATIONAL FUEL GAS CODE, ANSI Z223.1 OR CAN/
CSA-B149.1 or applicable provisions of the local building codes.
Size and install proper size vent pipe; refer to Table 6.

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 (2 cm/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.

TABLE 6: VENT CONNECTION

MODEL NUMBER VENT CONNECTOR

G(B,W) 1000 10" (25.4 cm)
G(B,W) 1300 12" (30.5 cm)
G(B,W) 1500 12" (30.5 cm)
G(B,W) 1850 14" (35.6 cm)
G(B,W) 2100 14" (35.6 cm)
G(B,W) 2500 16" (40.6 cm)

For vent arrangements other than Table 10 and for proper boiler
operation, a barometric damper is required to maintain draft
between -0.02" W.C.. and -0.04" W.C. at 2 feet (0.6 m) above the
boiler vent collar.

VENTING

CAUTION

WHEN VENTING THE GENESIS BOILER THROUGH AN
OVERSIZED CHIMNEY (INCLUDING MASONRY CHIMNEYS),
ADDITIONAL CARE MUST BE EXERCISED T O ASSURE PROPER
DRAFT . FOR PROPER OPERA TION, A MINIMUM DRAFT OF -0.02"

W.C. AND A MAXIMUM DRAFT OF -0.04" W .C. MUST BE MAINTAINED.
IN INSTANCES OF EXCESSIVE DRAFT, A BAROMETRIC DAMPER
MA Y BE REQUIRED T O ASSIST IN MAINTAINING THE PROPER
DRAFT. DRAFT SHOULD BE MEASURED 2 FEET (0.6 M) ABOVE

THE BOILER VENT COLLAR.

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 ASPHYXIA TION.

This boiler is approved to be vented as a Category I, Category III
(horizontal venting), or a Direct V ent appliance. The Horizont al and
Direct Venting options require a special vent kit.

STANDARD (VERTICAL) VENTING , CA TEGOR Y I

THIS BOILER MAY BE VENTED ACCORDING TO T ABLE 10 (ALSO

STANDARD (HORIZONT AL) VENTING , CA TEGORY III

Vent sizing, installation and termination shall be in accordance
with the

NATIONAL FUEL GAS CODE, ANSI Z223.1 OR
CAN/CSA-B149.1 (Current Editions). If applicable, all local, utility,
state/provincial regulations on venting must be followed. See Table
1 1, Figure 7 for venting specifications. The exhaust vent pipe must
be of a type listed for use with Category III gas burning heaters such
as "Saf-T-Vent" manufactured by Heat-Fab Inc.

For Category III installations, it is important that the Installed vent
be airtight. Please insure that all joints are sealed properly during
installation. For Horizontal Vent Kit part numbers, see Table 7.

T ABLE 7: HORIZONTAL VENT KITS.

HORIZONT AL VENT KIT MODEL

211426 G(B,W) 1000
211426-1 G(B,W) 1300
211426-1 G(B,W) 1500
211426-2 G(B,W) 1850
211426-2 G(B,W) 2100
211426-3 G(B,W) 2500

DIRECT VENT VERTICAL AND HORIZONT AL VENTING

For direct vent applications, this boiler may be vented according to
T ables 12 and 13; see Figures 8 and 9. For category III applications,

9

the exhaust vent pipe must be listed for use with category III gas
burning heaters such as "Saf-T-Vent" manufactured by Heat-Fab
Inc. This vent system must be 100% sealed with a condensate
trap located as close to the boiler as possible. When sizing exhaust
piping and intake air piping, 90-degree elbows are equivalent to 10
feet (3.1 m) of straight pipe and 45-degree elbows are equal to 5
feet (1.5 m) of straight pipe.

The intake air piping can be PVC, CPVC, ABS, Galvanized steel or
any suit able intake air piping that can be sealed. See Table 8 for
Direct Vent Kit number s.

T ABLE 8: DIRECT VENT KITS.

HORIZONT AL DIRECT VENT KIT NO. MODEL

211090 G(B,W) 1000
211090-1 G(B,W) 1300
211090-1 G(B,W) 1500
211090-4 G(B,W) 1850
211090-2 G(B,W) 2100
211090-3 G(B,W) 2500

VERTICAL DIRECT VENT KIT NO. MODEL

211089 G(B,W) 1000
211089-1 G(B,W) 1300
211089-1 G(B,W) 1500
211089-4 G(B,W) 1850
211089-2 G(B,W) 2100
211089-3 G(B,W) 2500

AIR INTAKE TERMINAL MODEL

191965-2 G(B/W) 1000

211336 G(B/W) 1300,1 500,1850
211336-1 G(B/W) 2100, 2500

HORIZONTAL VENT INST ALLATION

This boiler can be vented through the rear of the cabinet with the
use of the fluebox and vent adaptor. Any of the previous venting
configurations can be installed with rear connections.

To change the unit to rear exhaust:

1. The vent collar and cover plates must be removed from the top
and rear of the unit.

POWER VENT (OPTIONAL)

The length of vent used in horizontally vented installations can be
extended beyond the lengths shown in Tables 11 and 13 by
implementing the kits listed below:

TABLE 9: POWER VENT KITS.

POWER VENT KIT NO. MODEL MAX. LENGTH

211499 G(B,W) 1000 110' (33.5 m)
211499-1 G(B,W) 1300 100' (30.5 m)
211499-1 G(B,W) 1500 100' (30.5 m)
211499-2 G(B,W) 1850 100' (30.5 m)
211499-3 G(B,W) 2100 100' (30.5 m)
211499-4 G(B,W) 2500 100' (30.5 m)

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 double wall type B-1 gas vents, through 16" 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 followed 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.

1. Seal any unused opening in the common venting system.

2. Visually inspect the venting system for proper size and horizontal
pitch and determine there is no blockage or restriction, leakage,
corrosion or other unsafe condition.

2. Trim the insulation from around the rear flue hole in the jacket
and the fluebox. Support insulation from inside the fluebox to
facilitate cutting. Use safety precautions such as gloves. Place
the gasket and vent adaptor in the horizontal position. Place
the gasket and flue plate in the vertical position as shown in
Figure 4.

Figure 4. Switching from Vertical to Horizontal Venting.

3. Insofar as is practical, close all building doors, windows and
all doors between the space in which the appliances remaining
connected to the common venting system are located and other
spaces of the building. Turn on clothes dryers and any
appliance not connected to the common venting system. Turn
on any exhaust fans, such as range hoods and bathroom
exhausts, so they will operate at maximum speed. Do not
operate a summer exhaust fan. Close fireplace dampers.

4. Test fire the appliance(s) being inspected, making sure to follow
the manufacturers lighting and operating instructions.
Appliance(s) operating controls should be adjusted to provide
continuous service.

5. Check vent pressure of the appliance 24 inches (61.0 cm) above
boiler vent collar. Vent pressure should be maintained between

-0.02" W. C. and -0.04" W.C. to assure proper operation. For
appliances with a draft hood, check for spillage with mirror,
smoke or other device five minutes after placing appliance in
operation.

6. 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,

10

fireplace dampers and other gas burning appliances to their
previous conditions of use.

All boiler venting systems shall be installed in accordance with
the National Fuel Gas Code, ANSI Z223.1 or CAN/CSA-B149.1
(current edition), or applicable provisions of the local building
codes.

7. Avoid areas where condensate drainage may cause
problems such as above planters, patios, or adjacent to
windows where the steam from the flue gases may cause
fogging.

8. Select the point of wall penetration where the minimum
1/4" per foot (2 cm/m) of slope up can be maintained.

INT AKE/EXHAUST INST ALLA TION REQUIREMENTS

1. The termination must be 12 inches (30.5 cm) above snow
or grade level whichever is higher.

2. Due to normal formation of water vapor in the combustion
process, horizontal terminations must not be located over
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.

3. The exhaust terminal of the venting system must maintain
a minimum clearance of 4 feet (1.22 m) horizontally from,
and in no case above or below, unless a 4-foot horizontal
distance is maintained, from electric meters, gas meters,
regulators and relief equipment.

4. The minimum distance from inside corner formed by two
exterior walls is 6 feet (1.8 m) but 10 feet (3.1 m) is
recommended where possible.

5. Maintain a minimum distance of 4 feet (1.2 m) from any
soffit or eve vent to the exhaust terminal.

6. Maintain a minimum distance of 10 feet (3.1 m) from
any forced air inlet. Fresh air or make up air inlet such
as a dryer or furnace area is considered to be a forced
air inlet.

9. The through the wall termination kit is suitable for zero
clearance to combustible materials.

10. The mid point of the termination elbow must be a minimum
of 12 inches (30.5 cm) from the exterior wall.

SYSTEM INST ALLA TION

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 down draft 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 piping, etc., be properly supported.
The boilers described in this manual may be used for space (hydronic)

heating or for the heating of potable water . If the heater is to be used for
hydronic space heating, follow the instructions on pages 16-17 given for
equipment required for installation as in Figure 10. However, if units
are to be used for heating potable water, the information describing
specific systems is found on pages 18-20; see Figures 11 and 13.
Installations must comply with all local codes.

INST ALLA TION AS BOILER REPLACEMENT

Installation as boiler replacement on an old system with large water

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 , PREMA TURE
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.

Note: Venting system of other than
direct-vent appliance shall terminate at
least 4 ft. (1.2 m) below, 4 ft. (1.2 m)
horizontally from, or 1 ft. (30.0 cm)
above any door window or gravity air
inlet.

CAUTION

Figure 5. Vent Termination Installation Clearances

STANDARD VENTING DIRECT VENT APPLICA TIONS

11

STANDARD VENT - VERTICAL (CATEGORY I)

IMPORT ANT!

VENT PRESSURE MUST BE MAINT AINED

BETWEEN -0.02" W.C. AND -0.04" W.C. AT 24"

(61.0 cm) ABOVE BOILER COLLAR.

Figure 6.

T ABLE 10. STANDARD VERTICAL VENTING (CA TEGOR Y I)

APPLIANCE CERTIFIED EXHAUST MAXIMUM LENGTH

MODEL CA TEGOR Y VENTING VENT SIZE WITHOUT BAROMETRIC DAMPER

MATERIAL INCHES (cm) FEET (m)

I000
1300 TYPE B OR 35 Feet (10.7 m) without damper

1500 EQUIVALENT 12" (30.5 cm) *70 Feet (21.3 m) max. with damper
1850 TYPE B OR 14"(35.6 cm) 35 Feet (10.7 m) without damper

2100 EQUIVALENT *70 Feet (21.3 m) max. with damper

2500

* Extending venting over 70 feet (21.3 m) may require special considerations.

• Connection for the appliance exhaust vent to the stack must be as direct as possible. Maximum and minimum venting length
for Category I appliances shall be determined per the latest edition of the National Fuel Code (U.S.) and CAN/CSA-B149.1
Installation Code (Canada).

• The horizontal breaching of a vent must have an upward slope of not less than 1/4 inch per linear foot (2 cm/m) from the boiler
to the vent terminal. The horizontal portion of the vent shall be supported to maintain clearances and to prevent physical damage
or separation of joints.

I

I

I

I

TYPE B OR 10”(25.4 cm) 35 Feet (10.7 m) without damper

EQUIV ALENT *70 Feet (21.3 m) max. with damper

TYPE B OR 16" (40.6 cm) 35 Feet (10.7 m) without damper

EQUIV ALENT *70 Feet (21.3 m) max. with damper

12

ST ANDARD VENT - HORIZONTAL (CA TEGOR Y III)

Figure 7.

T ABLE 11. ST ANDARD HORIZONT AL VENTING (CA TEGOR Y III)

APPLIANCE CERTIFIED EXHAUST MAXIMUM

MODEL CATEGORY VENTING VENT SIZE VENT LENGTH

MA TERIAL INCHES (cm) FEET (m)

I000

1300 STAINLESS
1500 STEEL

1850 STAINLESS
2100 STEEL

2500

WARNING: No substitutions of flue pipe or vent cap material are allowed. Such substitutions would jeopardize the
safety and health of inhabitants.

• A maximum of two elbows can be used on inlet and outlet vent piping respectively. Each elbow is equal to 10 feet (3 m) of
straight pipe.

III

III

III

III

STAINLESS

STEEL

STAINLESS

STEEL

10”(25.4 cm)

12" (30.5 cm)

14"(35.6 cm)

16" (40.6 cm)

70' (21.3 m)

70' (21.3 m)

35' (10.7 m)

35' (10.7 m)

• Use only special gas vent pipes listed for use with Category III gas burning heaters, such as stainless steel Saf-T-Vent
by Heat Fab, Inc., available from A.O. Smith, 500 T ennessee W altz Parkway , Ashland City , TN 37015 Phone: [phone]
or Fax: [phone]. Pipe joints must be positively sealed.

13

DIRECT VENT - VERTICAL (CATEGORY I)

Figure 8.

T ABLE 12. DIRECT VENT (VERTICAL EXHAUST CONFIGURA TIONS)

APPLIANCE CERTIFIED EXHAUST VENT MAXIMUM AIR INTAKE AIR INT AKE MAXIMUM

MODEL CATEGORY EXHAUST VENT SIZE EXHAUST VENT MATERIAL SIZE AIR INTAKE

MATERIAL INCHES (cm) LENGTH FT (m) INCHES (cm) LENGTH FT (m)

GAL. STEEL

CPVC

GAL.STEEL

CPVC

GAL. STEEL

CPVC

GAL. STEEL

CPVC

GAL. STEEL

CPVC

8"

(20.3 cm)

10"

(25.4 cm)

10"

(25.4 cm)

12"

(30.5 cm)

12"

(30.5 cm)

(10.7 m)

(10.7 m)

I000

1300
1500

1850

2100

2500

I PVC, ABS OR

I PVC, ABS CR

I PVC, ABS OR

I PVC, ABS OR

I PVC, ABS OR

TYPE B OR

EQUIVALENT

TYPE B OR

EQUIV ALENT

TYPE B OR

EQUIV ALENT

TYPE B OR

EQUIVALENT

TYPE B OR

EQUIV ALENT

10"

(25.4 cm)

12"

(30.5 cm)

14"

(35.6 cm)

14"

(35.6 cm)

16"

(40.6 cm)

35'

(10.7 m)

35'

(10.7 m)

20'

(6.1 m)

20'

(6.1 m)

20'

(6.1 m)

35'

35'

20'

(6.1 m)

20'

(6.1 m)

20'

(6.1 m)

• Connection for the appliance exhaust vent to the stack must be as direct as possible. Maximum and minimum venting length
for Category I appliances shall be determined per the latest edition of the National Fuel Code (U.S.) and CAN/CSA-B149.1
Installation Code (Canada).

• The vent should be installed so as to prevent the accumulation of condensate and, where necessary , have means provided for
drainage of condensate. The horizontal breaching of a vent must have an upward slope of not less than 1/4 inch per linear foot
(2 cm/m) from the boiler to the vent terminal. The horizontal portion of the vent shall be supported to maintain clearances and to
prevent physical damage or separation of joints.

14

DIRECT VENT - HORIZONT AL (CATEGORY III)

Figure 9.

T ABLE 13. DIRECT VENT (HORIZONT AL EXHAUST CONFIGURA TIONS)

APPLIANCE CERTIFIED EXHAUST MAXIMUM AIR INTAKE AIR INT AKE MAXIMUM

MODEL CATEGOR Y EXHAUST VENT VENT SIZE EXHAUST VENT MA TERIAL SIZE AIR INTAKE

MATERIAL INCHES (cm) LENGTH FT (m) INCHES (m) LENGTH FT (m)

GAL. STEEL

CPVC

GAL.STEEL

CPVC

GAL. STEEL

CPVC

GAL. STEEL

CPVC

GAL. STEEL

CPVC

8"

(20.3 cm)

10"

(25.4 cm)

10"

(25.4 cm)

12"

(30.5 cm)

12"

(30.5 cm)

I000

1300
1500

1850

2100

2500

III PVC, ABS OR

III PVC, ABS CR

III PVC, ABS OR

III PVC, ABS OR

III PVC, ABS OR

STAINLESS

(SEALED)

STAINLESS

(SEALED)

STAINLESS

(SEALED)

STAINLESS

(SEALED)

STAINLESS

(SEALED)

10"

(25.4 cm)

12"

(30.5 cm)

14"

(35.6 cm)

14"

(35.6 cm)

16"

(40.6 cm)

35'

(10.7 m)

35'

(10.7 m)

20'

(6.1 m)

20'

(6.1 m)

20'

(6.1 m)

35'

(10.7 m)

35'

(10.7 m)

20'

(6.1 m)

20'

(6.1 m)

20'

(6.1 m)

WARNING: No substitutions of flue pipe or vent cap material are allowed. Such substitutions would jeopardize the
safety and health of inhabitants.

• A maximum of two elbows can be used on inlet and outlet vent piping respectively. Each elbow is equal to 10 feet (3 m) of
straight pipe.

• Use only special gas vent pipes listed for use with Category III gas burning heaters, such as stainless steel Saf-T -Vent by Heat
Fab, Inc. Inc., available from A.O. Smith, 500 Tennessee Waltz Parkway, Ashland City, TN 37015 Phone: [phone] or
Fax: [phone]. Pipe joints must be positively sealed.

15

volume may result in condensation within the boiler on cold starts.
This condensing of water vapor in the combustion area can be
prevented if a portion of the system water flow is diverted past the
boiler to cause an increase in boiler temperature.

BYP ASS BALANCING

HYDRONIC INST ALLA TION

The following is a brief description of the equipment required for
installations noted in Figure 10. All installations must comply with
local codes.

With systems where water temperature can be expected to drop
appreciably due to long standby periods, or heavy draw down, a
bypass pipe of at least 1" size with a balancing cock should be
installed between the boiler inlet and outlet. See Figure 10. When
the system first starts, the valve should be slowly opened until the
condensing ceases. This adjustment remains at a permanent
setting to establish required temperature rise across the boiler.

AIR SEPARA T OR

An air separator as shown in the piping diagram is recommended
especially for modern commercial hydronic systems.

VENT V AL VES

It is recommended that automatic, loose key or screwdriver type
vent valves be installed at each convector or radiator.

SYSTEM HEADERS

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 minimum pressure drop for several circuits,
manifolds should be larger than system loops.

The circuits should be spaced on the header at a minimum of
3" (7.6 cm) center to center. Install a balancing c ock in each return line.

T ABLE 14: INSTALLA TION ITEMS

NO. SUGGESTED ITEMS FOR INSTALLA TION

1. PAIR OF SHOR T PIPE NIPPLES, P AIR OF BOILER
LOOP TEES AND BALL V AL VE BETWEEN SYSTEM
SUPPL Y AND RETURN - ONE SET PER EACH BOILER

2. BOILER PIPE LOOP (See Table 5.)

3. BOILER CIRCULATING PUMP (See Table 5.)

4. THERMOMETER

5. PRESSURE GAUGE

6. LOW WATER CUTOFF (If Required By Local Code.)

7. FLOW SWITCH (Factory-Installed)

8. PRESSURE RELIEF VALVE (Factory-Installed)

9. BOILER INLET - OUTLET

10. SYSTEM SUPPLY TEMPERA TURE THERMOMETER

11. DRAIN or BLOW-DOWN V AL VE

WA TER SUPPL Y LINE

These boilers can be used ONLY in a forced circulation hot water
heating system. The pump must be interlocked with the boiler to
prevent boiler operation without water circulation. See maximum
and minimum flow rate information. Since most forced circulation
systems will be of the closed type, install the water supply line as
shown on piping diagram. See Figure 10. Severe damage will

occur if the boiler is operated without proper water flow
circulation.

Manifold headers are recommended for split systems with or
without zone valves 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.

COOLING PIPING

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 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 heating coils
exposed to refrigerated air, the boiler piping system must be
equipped with flow control 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 much more than heating flow rates. In this
way each system (heating or cooling) is circulated independently.

EXP ANSION TANK

Install an expansion tank as shown in Figures 10, 11, and 13. The
sizing of the expansion tank is very important and is directly related
to the total water volume of the system. Refer to ASME or other
reliable specifications for sizing.

Fast filling of large pipe, old radiator installations (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. For details,
refer to OPERATION section of this manual. 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.
OF 15 PSI (100 kPa) MUST BE MAINT AINED ON THE BOILER AT
ALL TIMES to avoid potential damage to the boiler that may not be
covered by the warranty.

A MINIMUM PRESSURE

CONVENTIONAL SP ACE HEATING INST ALLA TION

Modern copper-finned tube type boilers are exceptionally fast heating
units. The low water volumes in relation to firing rates require special
attention to water flow rates for smooth, efficient operation. These
considerations for the A. O. Smith copper heat exchanger boilers
are covered below.

Refer to Table 5 showing flow rate vs. pressure drop and
temperature rise.

Figure 10 shows a typical installation of the boiler.
A system with several flow controlled zones, or with a 3-way mixing

valve system could present a flow rate to the boiler of less than
required for a maximum of 50°F (28°C) temperature rise. Design
system with compensating bypasses to the boiler.

A system bypass should be installed as shown in Figure 10 to
prevent boiler circulation starvation when the system zones call for
reduced flow.

16

This bypass may also be used with multiple boilers manifolded for
reverse-return flow. The system byp ass would be installed from boiler
outlet to suction side of pump.

Large systems with multiple boilers should include main water
temperature controls (with or without outdoor reset) to sequence the
boiler on and off, in relation to the load on the system.

The boiler piping system of a hot water heating boiler connected to
heating coils located in air handling units where they may be
exposed to circulating refrigerated air, must be equipped with flow
control valves or other automatic means to prevent gravity circulation
of the boiler water during the cooling cycle. It is highly recommended
that the piping be insulated.

SP ACE HEA TING APPLICA TIONS

Controlling of these systems is decided mainly by the type of
building system controlling that is desired. A single boiler installation
might be controlled directly from space temperature thermostat(s).
Multiple boiler installations are more effective when the boilers are
sequenced in and out of operation by some form of main water
temperature controller. With one or two boilers, individual control
settings at progressive temperature may be used. For more than
two boilers, electronic sequencing controlling is recommended.

Individual controls, or the separate stages of a step controller, should
start the boiler loop circulator and fire the boiler. Some large
installations may require the firing of more than one boiler per stage.

The system or primary circulator may or may not be controlled
by the boiler sequencer. When this pump is operated through
the first switch of any type of step controller, care should be
taken to determine if a motor starter is needed due to
insufficient switch capacity.

Multiple boiler installations are especially adapted to the use of
outdoor reset for main water temperatures. This feature is not
mandatory but offers smooth, efficient operation of a modern
system.

24 VAC System Controller (Optional)

GB models require a field supplied 24VAC operating control to be
installed in the system such as: loop thermostat, indoor/outdoor reset
control, sequencing panel, or energy management system. The
connection for such devices is located in the 24 VAC junction box at
the rear of the unit. A 24 V AC thermostat/aquastat can only be used as
an "On/Off" switch for the unit. The actual controlling of the staging will
be through either the inlet or tank probe.

INTERNAL CONT AMINANTS

The system must be internally cleaned and flushed after a new or
replacement unit has been installed to remove contaminants that
may have accumulated during installation. This is doubly important
when a replacement unit is installed into an existing system where
Stop Leak or other boiler additives have been used.

All 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 clean and flush the system can cause solids to form on
the inside of the heat exchanger, can produce acid concentrations
that become corrosive, can allow excessive amounts of air or other
gases to form which could block circulation, foul system
accessories and damage circulator seals and impellers.

Normal use of flow control valves is required to prevent cross
circulation of zones as with any multiple pump system.

It is recommended that after installation, the boiler and system
when filled should include the proper percentage of cleaning solution

Figure 10. Single or Multiple Boiler Installation Diagram

17

related to approximate water volume of the system. The system
should be turned on to circulate water mix for about one hour and
then flush clean with fresh water.

Before operating the boiler, the entire system must be filled with
water, purged of air and checked for leaks. Do not use Stop Leak or
other boiler compounds.

THE WA TER HEA TER SHOULD BE LOCA TED IN AN AREA WHERE
THE GENERAL PUBLIC DOES NOT HAVE ACCESS TO BOILER
CONTROLS.

limit the maximum tank probe temperature for GW applications.
Failure to do this will void the warranty. If the tank probe is not
designated as the controlling probe, the staging of the unit will be
controlled by the inlet probe and will not use the desired tank
temperature as its base.

Refer to "Connection Diagram" in order to connect the tank probe
to the boiler. See Figures 12 and 15.

See section titled "Temperature Setpoints" for instructions on how
to set the temperature.

HOT WATER SUPPLY

BOILER INST ALLATION

WATER LINE CONNECTIONS

Where excessive heat exchanger condensation exists due to
continued low inlet water temperatures below 120°F (49°C), a
bypass balance loop must be installed. See Figures 10 and 12.

HARD WA TER CONDITIONS

Where hard water conditions exist, water softening or the threshold
type of water treatment is recommended. This will protect the
dishwashers, coffee urns, water heaters, water piping and other
equipment. When water softening or water treatment is not practical,
a comparatively easy method of periodic lime removal from the unit
must be employed.

WARNING

LIME ACCUMULATION CAN REDUCE THE LIFE OF THE
EQUIPMENT , REDUCE EFFICIENCY AND WASTE FUEL. BOILER
FAILURE DUE TO LIME OR SCALE BUILDUP VOIDS THE
WARRANTY.

Tank Probe (Optional)

In addition to the Inlet and Outlet/ECO Probes, units can be
optionally equipped with a tank probe. The connection for the tank
probe is located in the 24VAC junction box at the rear of the unit.
The tank probe can be configured to control the staging of the unit.
See "Tank Probe Installation Procedure" section below for
additional information.

T ANK PROBE INSTALLA TION PROCEDURE

A tank probe is supplied with each hot water supply boiler (GW). To
connect the tank probe to the boiler, remove the cover from the
24VAC junction box at the rear of the unit. Connect the probe wires
across terminals 1 & 2. (The wires leading to the terminals will be
yellow.) Check the field connection diagram located on this cover of
the junction box to assure proper wiring.

Once the tank probe has been connected to the boiler, it must be
designated as the controlling probe for the system. This is
accomplished by changing two Dip Switch settings on the Central
Control Board. First, Dip Switch “SW1-4” must be set to the “ON”
position to designate the tank probe as the controlling probe.
Second, Dip Switch “SW1-1” must be set to the “OFF” position to

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 SUPPL Y SYSTEM, THE GAS VAL VES MUST BE
CHECKED FOR SAFE OPERA TION. MAKE SURE THAT THE OUTSIDE
VENTS ON THE SUPPL Y REGULATORS AND THE SAFETY VENT V ALVES
ARE PROTECTED AGAINST BLOCKAGE. THESE ARE P AR TS OF
THE GAS SUPPLY SYSTEM, NOT THE BOILER. VENT BLOCKAGE
MA Y OCCUR DURING ICE BUILD-UP OR SNOW STORMS.

WHEN LOCAL CODES REQUIRE A MAIN MANUAL SHUT-OFF
VALVE OUTSIDE THE BOILER JACKET, A SUITABLE MAIN
MANUAL SHUT -OFF V ALVE MUST BE INSTALLED IN A LOCA TION
COMPL YING WITH THOSE CODES.

IT IS IMPORT ANT TO GUARD AGAINST GAS VAL VE FOULING
FROM CONTAMINANTS IN THE GAS WAYS. SUCH FOULING
MA Y CAUSE IMPROPER OPERA TION, FIRE OR EXPLOSION. IF
COPPER SUPPLY LINES ARE USED THEY MUST BE
APPROVED FOR GAS SERVICE.

BEFORE AT TACHING 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)
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 SER VING GAS SUPPLIERS. REFER TO
NATIONAL FUEL GAS CODE, ANSI Z223.1 OR CAN/CSA -B149.1
(current edition).

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 SYSTEM AT TEST PRESSURES EQUAL TO
OR LESS THAN 1/2 PSI (3.5KPA).

18

ONE GENESIS (MODEL GW) HOT WATER SUPPLY BOILER WITH HORIZONTAL TANK

INSTALL THERMAL EXPANSION
TANK ON COLD WATER
SUPPLY LINE, IF CHECK VALVE
OR PRESSURE REDUCING
VALVE IS USED IN SUPPLY.

DANGER

TEMPERATURE SETTING SHOULD NOT EXCEED
SAFE USE TEMPERATURE AT FIXTURES.
SEE WATER TEMPERATURE CONTROL
WARNING ON P AGE 26. IF HIGHER PREHEA T
TEMPERA TURES ARE NECESSARY TO OBTAIN
ADEQUATE BOOSTER OUTPUT, ADD AN
ANTI-SCALD VALVE FOR HOT WATER
SUPPLIED TO FIXTURES.

PRESSURE RELIEF VALVE RATING SHOULD
NOT EXCEED PRESSURE CAPACITY OF ANY
COMPONENT IN THE SYSTEM.

PIPING SHOULD CONFORM TO LOCAL CODES.
BALL VALVES ARE SHOWN FOR SERVICING

BOILER. HOWEVER, LOCAL CODES SHALL
GOVERN THEIR USAGE.

IMPORTAN T

WATER FLOW SWITCH PROTECTS THE
BOILER IN CASE OF WATER SERVICE
INTERRUPTION OR CIRCULATOR FAILURE.

• PIPE TO OPEN DRAIN
X FACTORY-INSTALLED ON UNIT

== SUPPLIED WITH UNIT
= FIELD-INSTALLED

THE WA TER MANIFOLD IS NOT DESIGNED T O

WARNING

SUPPORT THE WEIGHT OF THE WA TER PIPING
SYSTEM. SPECIAL CARE MUST BE TAKEN T O
ENSURE PROPER SUPPORT .

TWO TEMPERA TURE WA TER
MIXING VALVE APPLICATION

CIRCULATING RETURN

LINE CONNECTIONS

• TEMPERED WATER LOOP, IF USED,
CONNECT TO POINT R.

• STORED TEMPERA TURE WATER LOOP ,
IF USED, CONNECT TO ANY OPENING
NEAR BOTTOM OF T ANK.

MINIMUM

MODELS

MODELS INCHES

GW-1000

THRU 2 1/2"

2500 NPT

FACTOR Y PUMP SIZING

BASED ON 50 EQUIVALENT

FEET (15.2 m) OF PIPE.

PIPE SIZE

Figure 11. Single boiler with horizontal tank.

Encase field-supplied wires
between tank probe and junction
box with 1/2" field supplied
conduit. "Pigtails" of field­supplied wires should be spliced
to "pigtails" of tank probe and
connected to 24 VAC junction box.
See figure 15. This conduit and
wiring should be separate from
any other conduit/wiring to guard
against EMI (electromagnetic
interference).

Figure 12. Tank probe installation.

19

ONE GENESIS (MODEL GW) HOT WATER SUPPLY BOILER WITH VERTICAL TANK

PRESSURE RELIEF VALVE RATING SHOULD NOT EXCEED PRESSURE CAPACITY OF ANY COMPONENT IN THE SYSTEM.
PIPING SHOULD CONFORM TO LOCAL CODES.
BALL VALVES ARE SHOWN FOR SERVICING BOILER. HOWEVER, LOCAL CODES SHALL GOVERN THEIR USAGE.

IMPORTANT

WATER FLOW SWITCH PROTECTS THE BOILER IN CASE OF WATER SERVICE INTERRUPTION OR CIRCULATOR FAILURE.

• PIPE TO OPEN DRAIN
X FACTORY INSTALLED ON UNIT

== SUPPLIED WITH UNIT
= FIELD-INSTALLED

INSTALL THERMAL EXPANSION
TANK ON COLD WATER SUPPLY
LINE, IF CHECK VALVE OR
PRESSURE REDUCING VALVE
IS USED IN SUPPLY.

Figure 13. Single boiler with vertical tank.

MINIMUM

MODELS

PIPE SIZE

MODELS INCHES

GW-1000

THRU 2 1/2"

2500 NPT

FACTORY PUMP SIZING BASED

ON 50 EQUIVALENT FEET

(15.2 m) OF PIPE.

20

DANGER

TEMPERATURE SETTING SHOULD NOT EXCEED SAFE USE
TEMPERATURE A T FIXTURES. SEE W A TER TEMPERA TURE
CONTROL WARNING ON P AGE 26. IF HIGHER PREHEA T TEM­PERATURES ARE NECESSARY TO OBTAIN ADEQUATE
BOOSTER OUTPUT, ADD AN ANTI-SCALD V AL VE FOR HOT
WA TER SUPPLIED TO FIXTURES.

TWO TEMPERATURE WATER
MIXING VALVE APPLICATION

CIRCULATING RETURN

LINE CONNECTIONS

• TEMPERED WATER LOOP, IF USED,
CONNECT TO POINT R.

• STORED TEMPERATURE W ATER LOOP ,
IF USED, CONNECT TO ANY OPENING
NEAR BOTTOM OF T ANK.

4" BTU/hr 35,880,000 24,648,000 19,968,000 17,004,000 15,132,000 13,728,000 12,636,000 11,700,000 11,232,000 10,452,000 9,360,000 8,580,000 7,800,000 7,176,000

kW 10,508 7,219 5,848 4,980 4,432 4,021 3,701 3,427 3,290 3,061 2,741 2,513 2,284 2,102

3" BTU/hr 17,160,000 12,012,000 9,750,000 8,268,000 7,410,000 6,708,000 6,084,000 5,772,000 5,382,000 5,070,000 4,602,000 4,134,000 3,822,000 3,556,800

kW 5,026 3,518 2,856 2,421 2,170 1,965 1,782 1,690 1,576 1,485 1,348 1,211 1,1 1 9 1,042

kW 2,878 1,987 1,608 1,371 1,211 1,097 1,028 937 891 845 754 685 626 585

2 1/2" BTU/hr 9,828,000 6,786,000 5,491,200 4,680,000 4,134,000 3,744,000 3,510,000 3,198,000 3,042,000 2,886,000 2,574,000 2,340,000 2,137,200 1,999,800

kW 1,805 1,256 1,005 868 768 694 640 594 557 525 466 43 4 388 366

1 1/2" BTU/hr 3,276,000 2,277,600 1,840,800 1,544,400 1,404,000 1,263,600 1,170,000 1,076,400 1,014,000 - - - - - - - - - - - - - - -

2" BTU/hr 6,162,000 4,290,000 3,432,000 2,964,000 2,620,800 2,371,200 2,184,000 2,028,000 1,903,200 1,794,000 1,591,200 1,482,000 1,326,000 1,248,000

kW 959 667 539 452 411 370 343 315 297 - - - - - - - - - - - - - - -

kW 640 434 352 302 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

kW 410 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

1 1/4" BTU/hr 1,400,000 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

(Inches) (3.05) (6.10) (9.14) (12.19) (15.24) (18.29) (21.34) (24.38) (27.43) (30.48) (38.10) (45.72) (53.34) (60.96)

Size Cap. 10 Ft. 20 Ft. 30 Ft. 40 Ft. 50 Ft. 60 Ft. 70 Ft. 80 Ft. 90 Ft. 100 Ft. 125 Ft. 150 Ft. 175 Ft. 200 Ft.

Iron Pipe

Nominal

T ABLE 15. Suggested Pipe Size For Multiple Gas Appliances (Natural)

(Inches) (3.05) (6.10) (9.14) (12.19) (15.24) (18.29) (21.34) (24.38) (27.43) (30.48) (38.10) (45.72) (53.34) (60.96)

Iron Pipe

1 1/4" BTU/hr 2,184,000 1,482,000 1,201,200 1,029,600 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

1" BTU/hr 1,060,800 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Size Cap . 1 0 Ft. 20 Ft. 30 F t. 40 Ft . 50 F t. 60 Ft. 70 F t. 80 Ft . 90 Ft. 100 Ft. 125 Ft. 150 Ft. 175 Ft. 200 Ft.

Nominal

kW 311 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

TABLE 16. Suggested Pipe Size For Multiple Gas Appliances (Propane Gas)

4" BTU/hr 23,000,000 15,800,000 12,800,000 10,900,000 9,700,000 8,800,000 8,100,000 7,500,000 7,200,000 6,700,000 6,000,000 5,500,000 5,000,000 4,600,000

kW 6,736 4,627 3,749 3,192 2,841 2,577 2,372 2,197 2,109 1,962 1,757 1,61 1 1,464 1,347

kW 3,222 2,255 1,830 1,552 1,391 1,259 1,142 1,084 1,010 952 864 776 718 668

3" BTU/hr 11,000,000 7,700,000 6,250,000 5,300,000 4,750,000 4,300,000 3,900,000 3,700,000 3,450,000 3,250,000 2,950,000 2,650,000 2,450,000 2,280,000

kW 1,845 1,274 1,031 879 776 703 659 600 571 542 483 439 401 375

2 1/2" BTU/hr 6,300,000 4,350,000 3,520,000 3,000,000 2,650,000 2,400,000 2,250,000 2,050,000 1,950,000 1,850,000 1,650,000 1,500,000 1,370,000 1,280,000

kW 1,157 805 644 556 492 445 410 381 357 337 299 - - - - - - - - -

1 1/2" BTU/hr 2,100,000 1,460,000 1,180,000 990,000 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

2" BTU/hr 3,950,000 2,750,000 2,200,000 1,900,000 1,680,000 1,520,000 1,400,000 1,300,000 1,220,000 1,150,000 1,020,000 - - - - - - - - -

kW 615 428 346 290 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Maximum Capacity of Pipe in BTU/hr and kW for Gas Pressures of 14 in. W .C. (0.5 p si) or Less and a Pressure Drop of 0.5 in. W .C.

(based on 1.53 Specific Gravity Gas w/Heating V alue of 2,500 BTU’s/Ft

Length of Pipe in Feet (Metres)

Maximum Capacity of Pipe in BTU/hr and kW for Gas Pressures of 14 in. W .C. (0.5 p si) or Less and a Pressure Drop of 0.5 in. W .C.

(based on 0.60 Specific Gravity Gas w/Heating Value of 1,000 BTU’ s/Ft

Length of Pipe in Feet (Metres)

3

)

3

)

21

Gas Pipe sizing may be larger than heater connections 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 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.

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.

Gas control trains are unique for each Genesis II unit. Stages one,
two and three run sequentially left to right on the smaller units (GB/
GW 1000 -1500) while stage one is located in different positions on
the larger units. Gas manifold diagrams are depicted in Figure 14.

1. CORRECT GAS - Make sure gas on which the boiler will operate
is the same as that specified on the rating plate. Do not install
the boiler if equipped with a different type of gas. Consult your
gas supplier.

2A. SIZING GAS SUPPLY LINE (For single boiler installations). See

Table 17.

2B.SIZING GAS SUPPLY LINE (For multiple installations of two

or more boilers). See Tables 15 (Natural Gas) and 16
(Propane Gas).

TABLE 17. SINGLE UNIT INSTALLATION, SUGGESTED
PIPE SIZE

DIST ANCE FROM METER

BTU INPUT 0-50' 51-100' 101-200' 201-300' 301-500'

990,000 2" 2" 2 1/2" 2 1/2" 2 1/2"
1,300,000 2" 2 1/2" 2 1/2" 3" 3 "
1,500,000 2" 2 1/2" 3 " 3" 3 1/2"
1,850,000 2 1/2" 2 1/2" 3" 3 " 3 1/2"
2,100,000 2 1/2" 3" 3 " 3 1/2" 4"
2,500,000 2 1/2" 3" 4 " 4 " 4 1/2"

Use Tables 15 or 16, which are taken from ANSI booklet Z223.1,
NATIONAL FUEL GAS CODE, or CAN/CSA-B149.1 (current edition)
to size iron pipe or equivalent gas supply line.

WIRING CONNECTIONS

ALL ELECTRICAL WORK MUST BE INSTALLED IN
ACCORDANCE WITH THE NATIONAL ELECTRICAL CODE,
ANSI/NFPA 70 OR CSA-C22.1 CURRENT EDITION AND MUST
CONFORM TO LOCAL REGULATIONS.

AN ELECTRICAL GROUND IS REQUIRED T O REDUCE RISK OF
ELECTRIC SHOCK OR POSSIBLE ELECTROCUTION.

ground connection to the wire provided in the electrical supply
junction box on the boiler.

Grounding and all wiring connected to this boiler must conform to
the local code authority having jurisdiction or, in the absence of such
requirements, with the
CSA-C22.1 current edition.

The Central Control Board and Flame Control Boards that make
up the control system are micro-processor based which make
them vulnerable to voltage and amperage fluctuations in the
power supply. Refer to Connection and Schematic Diagrams.
See Figures 15 and 16.

IF ANY OF THE ORIGINAL WIRE, AS SUPPLIED WITH THE
APPLIANCE, MUST BE REPLACED, IT MUST BE REPLACED WITH
TYPE 105°C WIRE OR ITS EQUIVALENT.

The Genesis Hot Water Supply Boiler must be connected to a single
phase dedicated and isolated line source: 120 v olts, 60Hz, and 30 Amps.

National Electrical Code, ANSI/NFPA 70 or

Make the

TABLE 18. Orifice Size for Natural and Propane (LP) Gases (U.S. and Canada Installations, for high altitude up to
4,500 ft. (1,372 m).

Drill Size

Input Rating Number of

Model BTU/HR Burners Natural (4 Holes) Propane (3 Holes)

G(B,W) 1000 990,000 10 0.111" 0.075"
G(B,W) 1300 1,300,000 13 0.111" 0.075"
G(B,W) 1500 1,500,000 15 0.111" 0.075"
G(B,W) 1850 1,850,000 19 0.111" 0.075"
G(B,W) 2100 2,100,000 21 0.111" 0.075"
G(B,W) 2500 2,490,000 25 0.111" 0.075"

22

GAS MANIFOLD ASSEMBLY

GB/GW 1000 - 1500

GB/GW 1850

GB/GW 2100

GB/GW 2500

Figure 14. GB/GW 1000 - 2500 Gas Manifold Assembly Diagrams.

23

FIGURE 15.

GENESIS GB/GW 1000-2500 SERIES 400 WIRING DIAGRAM

24

25

FIGURE 16.

GENESIS GB/GW 1000-2500 SERIES 400 SCHEMATIC DIAGRAM

26

27

Figure 17. CCB CENTRAL CONTROL BOARD

28

Figure 18. FCB FLAME CONTROL BOARD Diagram

29

Figure 19. PDB POWER DISTRIBUTION BOARD Diagram

30

Fuse Protection

(B.) Hot Water Supply Installation:

The 24VAC circuitry is protected with a 3 amp fuse on the Flame
Control Boards (FCB) and a 7.5 amp fuse on the Central Control
Board. If the fuse opens, a red LED located near the fuse will light.
See Figures 17 and 18. If the red LED is illuminated, replace the
fuse. Repeated failure of the fuse is an indication of possible
damage to the ignition control. The 120VAC circuit s of each Flame
Control Board is protected with a 10 amp (15 amp for the CCB)
fuse located on the Power Distribution Board (PDB). The 20 amp
pump fuse is also on the PDB.

Recommended Replacement fuses:
Littlefuse automotive fuse p/n 29707.5 for the 7.5 amp
CCB fuse, and Littlefuse p/n 297003 for the 3 amp FCB fuses.

OPERATION

IMPORTANT

Only qualified personnel shall perform the initial firing of the heater.
If you have questions, please contact the factory or your local A.O.
Smith representative.

Operation and troubleshooting instructions are included with this
manual. By using these instructions, the user may be able to
make minor operational adjustments. The user should not attempt
repairs, but should contact a service technician or gas supplier
for service.

GENERAL

Never operate the boiler without first making sure the boiler and
system are filled with water, in addition:

For hot water supply Boiler installations:

• Make sure a temperature and pressure relief valve is installed
on the storage tank if used. Also check for leaks.

For heating boiler installations:

• Make sure that the boiler and system have been purged of air

and checked for leaks.

FILLING AND PURGING W A TER SYSTEM

(A.) Hydronic Heating Installation:

1. Fill system through bypass until pressure approaches
desired system pressure. Close bypass valve and
permit pressure to be established by the pressure
reducing valve.

2. Vent all high points in system to purge system of air.

Provisions should be made to permit manual venting of radiators or
convectors.

1. Close the systems drain valve.

2. Open a nearby hot water faucet to permit the air in the system
to escape.

3. Fully open the cold water inlet pipe valve allowing the heater
and piping to be filled.

4. Close the hot water faucet as water starts to flow.

5. The heater is ready to be operated.

PURGING OF GAS LINE

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

CAUTION

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

BEFORE PLACING THE BOILER IN OPERATION, CHECK FOR
GAS LEAKAGE. USE A SOAP AND WA TER SOLUTION OR OTHER
MATERIAL ACCEPT ABLE FOR THE PURPOSE OF LOCATING GAS
LEAKS. DO NOT USE MA TCHES, CANDLES, FLAME OR OTHER
SOURCES OF IGNITION FOR THIS PURPOSE.

WARNING

THE GAS VAL VE MUST HAVE BEEN IN THE OFF POSITION FOR A T
LEAST 5 MINUTES. This waiting period is an important safety
step. Its purpose is to permit gas that may have accumulated in
the combustion chamber to clear. IF YOU DETECT GAS ODOR AT
THE END OF THIS PERIOD DO NOT PROCEED WITH LIGHTING .
RECOGNIZE THA T GAS EVEN IF IT SEEMS WEAK, MA Y INDICA TE
PRESENCE OF ACCUMULA TED GAS SOMEPLACE IN THE AREA
WITH RISK OF FIRE OR EXPLOSION. SEE THE FRONT PAGE
FOR STEPS TO BE T AKEN.

INLET GAS PRESSURE

The inlet gas pressure is measured by removing the low gas
pressure switch located on the main gas manifold which is
upstream of the unit's combination gas valves. See Figure 14. The
maximum value specified in the table must not be exceeded. The
minimum values, shown in Table 19, must be maintained under
both load and no load conditions (static and firing conditions). The
combination gas valves supplied with the boiler are for low pressure
service. If upstream pressure exceeds 14.0" W.C., an

intermediate gas pressure regulator of the lockup type must be
installed.

T ABLE 19. INLET GAS PRESSURES.

INLET GAS PRESSURE NAT. GAS PROP . GAS

MAX. INLET PRESSURE (IN. W.C.) 14.0 14.0

MIN. INLET PRESSURE (IN. W.C.) 6.0 11.0

31

Lighting Instructions for the G(B/W) 1000 through 2500 models

FOR YOUR SAFETY READ BEFORE OPERA TING

WARNING: IF YOU DO NOT FOLLOW THESE INSTRUCTIONS EXACTLY , A FIRE OR
EXPLOSION MA Y RESUL T CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR
LOSS OF LIFE.

A. THIS APPLIANCE DOES NOT HAVE A PILOT. IT IS

EQUIPPED WITH AN IGNITION DEVICE WHICH
AUTOMA TICALL Y LIGHTS THE BURNER. DO NOT TR Y TO
LIGHT THE BURNER BY HAND.

B. BEFORE OPERA TING: SMELL ALL AROUND THE APPLI-

ANCE AREA FOR GAS. BE SURE TO SMELL NEXT TO THE
FLOOR BECAUSE SOME GAS IS HEA VIER THAN AIR AND
WILL SETTLE ON THE FLOOR.
WHAT T O DO IF YOU SMELL GAS

• DO NOT TRY TO LIGHT ANY APPLIANCE.

• DO NOT TOUCH ANY ELECTRIC 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 DEP ARTMENT.

C. USE ONLY YOUR HAND TO PUSH IN OR TURN THE GAS

CONTROL KNOB. NEVER USE TOOLS. IF THE KNOB WILL
NOT PUSH IN OR TURN BY HAND, DON’T TRY TO REPAIR
IT . CALL A QUALIFIED SERVICE TECHNICIAN. FORCE OR
ATTEMPTED REPAIR MAY RESULT IN A FIRE OR
EXPLOSION.

D. DO NOT USE THIS APPLIANCE IF ANY P ART HAS BEEN

UNDER WATER. IMMEDIATELY CALL A QUALIFIED
SERVICE TECHNICIAN TO INSPECT THE APPLIANCE AND
TO REPLACE ANY PART OF THE CONTROL SYSTEM AND
ANY GAS CONTROL WHICH HAS BEEN UNDER WA TER.

E . DO NOT OPERA TE APPLIANCE UNLESS UNIT IS FILLED

WITH WA TER AND WA TER LINES ARE FULL Y OPEN.

Note: Knob cannot be turned to "OFF" unless
knob is pushed in slightly. Do NOT force.

OPERA TING INSTRUCTIONS

1. STOP! READ THE SAFETY INFORMATION THE
NEXT STEP ABOVE ON THIS LABEL.

2. SET THE SYSTEM CONTROLLER TO THE LOWEST

SETTING.

3. TURN OFF ALL ELECTRIC POWER TO APPLIANCE.

4. THIS APPLIANCE IS EQUIPPED WITH AN IGNITION

DEVICE WHICH AUTOMATICALLY LIGHTS THE
BURNER. DO NOT TRY TO LIGHT THE BURNER BY
HAND.

5. REMOVE CONTROL ACCESS P ANEL.

6. REFER TO DIAGRAMS ABOVE. TURN TOP KNOB OF

GAS CONTROL CLOCKWISE TO “OFF” POSITION,
(FIGURE A).

7. WAIT FIVE (5) MINUTES TO CLEAR OUT ANY GAS. THEN

SMELL FOR GAS, INCLUDING NEAR THE FLOOR.

TO TURN OFF GAS TO APPLIANCE

1. SET THE SYSTEM CONTROLLER TO THE LOWEST
SETTING .

2. TURN POWER SWITCH ON APPLIANCE TO “OFF”
POSITION.

3. REMOVE ACCESS PANEL T O EXPOSE GAS CONTROL.

IF YOU SMELL GAS,
STOP ! FOLLOW “B” IN THE SAFETY INFORMA

TION ABOVE ON THIS LABEL. IF YOU DON’T

SMELL GAS, GO TO THE NEXT STEP.

8. TURN TOP KNOB OF GAS CONTROL COUNTER
CLOCKWISE

9. REPLACE CONTROL ACCESS P ANEL.

10. TURN POWER SWITCH TO “ON” POSITION.

11. SET THE SYSTEM CONTROLLER TO DESIRED
SETTING .

12. IF THE APPLIANCE WILL NOT OPERA TE, FOLLOW THE
INSTRUCTIONS “TO TURN OFF GAS TO THE
APPLIANCE” AND CALL YOUR SERVICE TECHNICIAN
OR GAS SUPPLIER.

4. REFER TO DIAGRAMS ABOVE. TURN TOP KNOB OF
G A S CONTROL CLOCKWISE (TO “OFF” POSITION,
(FIGURE A).

5. REPLACE CONTROL ACCESS PANEL.

TO “ON” POSITION, (FIG . B).

32

Lighting Instructions for the G(B/W) 1000 through 2500 models

FOR YOUR SAFETY READ BEFORE OPERATING

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

A. THIS APPLIANCE DOES NOT HAVE A PILOT. IT IS

EQUIPPED WITH AN IGNITION DEVICE WHICH
AUTOMA TICALLY LIGHTS THE BURNER. DO NOT TRY TO
LIGHT THE BURNER BY HAND.

B. BEFORE OPERATING: SMELL ALL AROUND THE

APPLIANCE AREA FOR GAS. BE SURE TO SMELL NEXT
TO THE FLOOR BECAUSE SOME GAS IS HEA VIER THAN
AIR AND WILL SETTLE ON THE FLOOR.

WHAT T O DO IF YOU SMELL GAS

• DO NOT TRY TO LIGHT ANY APPLIANCE.

• DO NOT TOUCH ANY ELECTRIC 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 DEP ARTMENT .

C. USE ONLY YOUR HAND TO TURN THE MAIN MANUAL GAS

VAL VE HANDLE. NEVER USE TOOLS. IF THE HANDLE WILL
NOT TURN BY HAND, DON’T TRY TO REP AIR IT . CALL A
QUALIFIED SERVICE TECHNICIAN. FORCE OR A TTEMPTED
REPAIR MA Y RESULT IN A FIRE OR EXPLOSION.

D. DO NOT USE THIS APPLIANCE IF ANY P ART HAS BEEN

UNDER WATER. IMMEDIATELY CALL A QUALIFIED
SERVICE TECHNICIAN TO INSPECT THE APPLIANCE AND
TO REPLACE ANY PART OF THE CONTROL SYSTEM AND
ANY GAS CONTROL WHICH HAS BEEN UNDER WA TER.

E . DO NOT OPERATE APPLIANCE UNLESS UNIT IS FILLED

WITH WA TER AND W ATER LINES ARE FULLY OPEN.

OPERA TING INSTRUCTIONS

1. STOP! READ THE SAFETY INFORMA TION ABOVE

ON THIS LABEL.

2. SET THE SYSTEM CONTROLLER TO THE LOWEST
SETTING.

3. TURN POWER SWITCH ON APPLIANCE TO “OFF”
POSITION.

4. TURN MAIN MANUAL GAS V AL VE TO “OFF” POSITION,
(FIGURE “B”). THE V ALVE IS “OFF” WHEN THE HANDLE IS
PERPENDICULAR TO THE GAS FLOW DIRECTION.

5. THIS APPLIANCE IS EQUIPPED WITH AN IGNITION
DEVICE WHICH AUTOMA TICALL Y LIGHTS THE BURNER,
DO NOT TRY TO LIGHT THE BURNER BY HAND.

6. WAIT FIVE (5) MINUTES T O CLEAR OUT ANY GAS. THEN

TO TURN OFF GAS TO APPLIANCE

1. SET THE SYSTEM CONTROLLER TO THE LOWEST

SETTING .

2. TURN POWER SWITCH ON APPLIANCE TO “OFF”

POSITION.

SMELL FOR GAS, INCLUDING NEAR THE FLOOR. IF YOU

SMELL GAS,
STOP! FOLLOW “B” IN THE SAFETY INFORMA­ TION ABOVE ON THIS LABEL. IF YOU DON’T SMELL

GAS, GO TO THE NEXT STEP .

7. TURN MAIN MANUAL GAS V AL VE TO “ON” POSITION,
(FIGURE “A”), THE V ALVE IS “ON” WHEN THE HANDLE
IS P ARALLEL TO THE GAS FLOW DIRECTION.

8. TURN POWER SWITCH TO “ON” POSITION.

9. SET THE SYSTEM CONTROLLER TO DESIRED SETTING .

10. IF THE APPLIANCE WILL NOT OPERA TE, FOLLOW THE
INSTRUCTIONS “TO TURN OFF GAS TO THE APPLI­ANCE” AND CALL YOUR SERVICE TECHNICIAN OR GAS
SUPPLIER.

3. TURN MAIN MANUAL GAS V ALVE T O “OFF” POSITION,
(FIGURE “B”). THE VA LVEIS “OFF” WHEN THE HANDLE
IS PERPENDICULAR TO THE GAS FLOW DIRECTION.

33

MANIFOLD PRESSURE

The manifold gas pressure is measured at the pressure tap on the
downstream side of the combination gas valve(s). For natural gas
the Manifold Pressure should measure 3.5" W.C. For propane (LP)
gas, the pressure should read 10" W.C.

IMPORTANT

UNDER NO CIRCUMSTANCES SHALL THE GAS PRESSURE
MEASURED A T THE BURNER MANIFOLD EXCEED THA T ST A TED
ON THE BOILER RA TING PLA TE. OVERFIRING WILL RESULT IN
DAMAGE TO THE BOILER, AS WELL AS INCREASED RISK OF
FIRE, SOOTING AND ASPHYXIA TION.

ADJUSTMENTS

T ABLE 20. RISK OF SCALDS.

TEMPERA TURE TIME TO PRODUCE 2nd & 3rd

SETTING DEGREE BURNS ON ADULT SKIN

OVER 170°F (77°C) NEARLY INSTANTANEOUS

160°F (71°C) ABOUT 1/2 SECOND
150°F (66°C) ABOUT 1-1/2 SECONDS
140°F (60°C) LESS THAN 5 SECONDS
130°F (54°C) ABOUT 30 SECONDS

120°F (49°C) OR LESS MORE THAN 5 MINUTES

USE ANTI-SCALD VALVE(S) in the hot water system to reduce the
risks of scalding at points of use such as lavatories, sinks and
bathing facilities.

ON INITIAL ST ARTUP SOME ADJUSTMENTS ARE NECESSARY .

1. CHECK MANIFOLD AND INLET GAS PRESSURES.

2. CHECK THE INPUT. SEE NATIONAL FUEL GAS CODE, ANSI
Z223.1 OR CAN/CSA - B149.1 (CURRENT EDITION) FOR
PROCEDURES.

DANGER

HOT WATER TEMPERATURES REQUIRED FOR AUTOMATIC
DISHWASHER AND LAUNDRY USE CAN CAUSE SCALD
BURNS RESULTING IN SERIOUS PERSONAL INJURY AND/OR
DEA TH. THE TEMPERA TURE A T WHICH INJURY OCCURS V ARIES
WITH THE PERSON'S AGE AND TIME OF EXPOSURE. THE
SLOWER RESPONSE TIME OF CHILDREN, AGED OR DISABLED
PERSONS INCREASES THE HAZARDS TO THEM. NEVER ALLOW
SMALL CHILDREN TO USE A HOT WATER TAP, OR TO DRAW
THEIR OWN BA TH WA TER. NEVER LEA VE A CHILD OR DISABLED
PERSON UNATTENDED IN A BA THTUB OR SHOWER.

THE WA TER HEA TER SHOULD BE LOCA TED IN AN AREA WHERE
THE GENERAL PUBLIC DOES NOT HAVE ACCESS TO SET
TEMPERA TURES.

CONTROL SYSTEM

The EMC 5000 control system is a fully integrated, state of the art
electronic control system. It consists of sensors, output devices, a
power switch, a 24vac transformer, wiring and the following printed
circuit boards:

• Central Control Board (CCB), see Figure 17.

• Flame Control Board (FCB), see Figure 18.

• Power Distribution Board (PDB), see Figure19.

• User Interface Module (UIM), see Figure 21.

The CCB contains circuitry for both master control and flame control
for the first stage. The FCB's contains circuitry for control on up to
three additional stages. Dipswitches on the CCB and FCB are used
to configure the system. The User Interface Module (UIM)
communicates with the user through a set of touch pads and a 4­line, 20-character LCD display . The PDB provides connection points
for input power, the water pump, and the transformer. It also
distributes power to the system and contains the system fuses.

Multiple-stage control is accomplished by means of an internal
communications network between the CCB and the FCB's. One
FCB is required for each stage beyond the initial first stage. The
CCB also contains an external communications system to allow
for connection to a PC, a modem, an EMS system, or something
similar. Through this connection multiple boilers can also be linked
together. CAUTION: The internal communications cables should

never be connected to the external communications connectors
and vice-versa.

IT IS RECOMMENDED IN DOMESTIC HOT WA TER APPLICA TIONS
THAT LOWER WA TER TEMPERATURES BE USED TO AVOID THE
RISK OF SCALDING. IT IS FURTHER RECOMMENDED, IN ALL
CASES, THAT THE WATER TEMPERATURE BE SET FOR THE
LOWEST TEMPERATURE WHICH SATISFIES THE USER'S HOT
WA TER NEEDS. THIS WILL ALSO PROVIDE THE MOST ENERGY
EFFICIENT OPERA TION OF THE BOILER AND MINIMIZE SCALE
FORMATION IN THE HEAT EXCHANGER, THUS PROLONGING
THE LIFE OF THE BOILER.

SETTING THE WA TER HEATER TEMPERATURE A T 120°F (49°C)
WILL REDUCE THE RISK OF SCALDS. SOME ST A TES REQUIRE
SETTINGS AT SPECIFIC LOWER TEMPERATURES. TABLE 20
ABOVE SHOWS THE APPROXIMATE TIME-TO-BURN
RELATIONSHIP FOR NORMAL ADULT SKIN.

There are several microcontrollers used on the boards. These
micros control the temperature and ignition control functions for
the boiler. Inherent in the design are the normal operating
sequences and safety features associated with a gas ignition
control system. The system continuously performs various
diagnostic tests to verify proper appliance and control operation.
Should an unsafe condition occur, the control will shut down the
burner and display a red fault light as well as indicate the cause of
the fault on the display. The operating programs for the system are
stored in permanent memory inside the micros. User-selectable
operating parameters and a history of detected faults are stored in
re-writable memory in the micros. A loss of power does not affect
either of the memories.

Inputs to CCB and FCB
Temperature Sensors:

• Temperature probes (CCB - outlet and either inlet or tank are

34

required): The CCB accepts analog temperature inputs from up
to three sensors (inlet, outlet and tank).

• ECO input (CCB - required):
The ECO (energy cut off) is a hi-limit switch, which is located
inside the outlet probe. It is a normally closed switch that opens
if the probe is exposed to a temperature higher than the trip
point. Once tripped, control system needs manual reset.

• Thermostat input (CCB - optional):
This input is set up to work with an externally connected
thermostat that provides a contact closure. If this input is closed
and everything else is in the proper state, a "call for heat"
condition will be initiated. These leads should be shorted
together, when a thermostat is not being used. If it is desired
that the thermostat control the temperature of the boiler, the
operating setpoint of the system should be set higher than the
temperature that the thermostat is controlling to. This will allow
the thermostat to control the boiler. When the thermostat closes,
a call for heat will be generated until the thermostat determines
that the required temperature has been reached.

Air Pressure Sensors (open condition indicates fault):

• Blocked Flue (CCB - required):
Normally closed switch that opens if the flue becomes blocked
during operation.

• Powered Vent (CCB - optional):
Normally open switch that closes when the powered vent is
operating properly. This input is enabled/disabled by a dip switch
on the CCB.

• Blower Prover (CCB/FCB - required on Stages with Blowers).
Normally open switch that closes when the air pressure
produced by the blower is above the set point.

Gas Pressure Sensors (open condition indicates fault):

• Low Gas (CCB - required):
Normally open switch that closes when the gas pressure rises
above the trip level. This input is enabled/disabled by a dipswitch
on the CCB.

• Hi Gas (FCB - optional):
Normally closed switch that opens if the gas pressure exceeds
a set value. This input is enabled/disabled by a dipswitch on the
CCB and FCB's.

Water Level Sensor (open condition indicates fault):

• Low Water Cut Off (CCB - optional):
Normally open switch that closes when water reaches preset
level. This input is enabled-disabled by a dipswitch on the CCB.

Water Flow Sensor:

• Flow (CCB - required):
Normally open switch that closes when flow exceeds a set value.

the burner. If the flame rod is missing or shorted, the flame will
not be detected. This input is enabled/disabled by a dipswitch
on the FCB.

Outputs from CCB and FCB's:

Relay Contact Output:

• IRI Gas Valve (CCB - 120 vac - optional):
Provides electrical power to operate an IRI Gas V alve Device.

• Alarm (CCB - 24vac - optional):
Provides electrical power to operate an external alarm. This
can be an audio device (i.e. Sonalert), a visual device (lamp),
or any other device that will operate with the voltage and current
level provided.

• Pump (CCB - 120vac - required on systems that do not have
an external pump):
Provides electrical power to directly operate a pump or the coil
of an externally connected contactor.

• Powered Vent (CCB - 24 vac - optional):
Provides electrical power to operate a powered vent.

• Blower (CCB / FCB - 120vac - required).
Single speed blowers utilize the high blower output only. Dip
switches on the FCB's enable/disable the use of blowers on
stages 2, 3 and 4.

• Igniter (FCB - 120vac - required).
Provides power to operate the HSI igniters. Dip switches on
the FCB's enables/disables the use of HSI igniters on stages
2, 3 and 4.

• Gas Valve (FCB - 24vac - required):
Provides power to activate the gas valve. The gas valve cannot
be activated when the ECO contacts are open.

• Low Water Cut Off (CCB - 24vac - optional)
Directly connected to the 24 vac line to provide power to operate
an external LWCO device.

CCB/FCB Indicator Lamps & Fuses

A green LED is mounted on the PDB to indicate when line voltage
is applied. (The PDB also contain a yellow and red LED, and a
test/run jumper, that are used during installation to verify proper
power connections.) A red LED on the CCB is used to indicate
when the 24vac input fuse has blown. The FCB's also have fuses
on their 24vac power line.

Yellow LED's are located near the micros on the CCB and
FCB's. These LED's are "heartbeat indicators" and blink
approximately twice per second to indicate that the micros are
running.

IRI Gas Valve Sensor:

• IRI Gas Valve (CCB - optional):
Normally open switch that closes when the IRI Gas Valve is
operating correctly . This input is enabled/disabled by a dipswitch
on the CCB.

• Flame Sensor:

Flame (CCB - required).
Returns a signal to the microprocessor if flame is detected on

CCB/FCB Jumpers:

The CCB has two jumpers and the FCB has one. JP1 on the
CCB is used to terminate the external communications line. It
is normally left off and installed when the external cable is very
long. JP2 on the CCB and JP1 on the FCB, are for factory use
only.

Igniters

The EMC 5000 system operates with Silicon Carbide Igniters.

35

CCB - Ten Position Dipswitch (Central Control Section) SW1:

Dipswitch configurations are
personnel! Once set the boiler will operate according to the chosen options. If a switch is changed, power must be cycled before the
change will take effect. The status of all dipswitches can be observed on the system status screen on the UIM.

CCB/FCB Dipswitches:

READ ONLY ON POWER UP. These switches are only to be set at the factory or by authorized trained

Dipswitches Function
Switch 1: Selection of the type of boiler application: On = GB/LB Off = GW/LW

Switch 2: Trials for ignition: On = 3 Off = 1
Switch 3: IRI Gas V alve Option: On = IRI Off = No IRI
Switch 4: Controlling Probe: On = Tank (Remote) Off = Inlet
Switch 5: Powered Venter: On = Yes Off = No
Switch 6: Low Water Cut Off: (L WCO) On = Yes Off = No
Switch 7: Low Gas Pressure On = Yes Off = No
Switch 8: Spare:
Switch 9 & 10. Number stages (FCB's): 9 10 #stages

NOTE: If the unit powers up with the number of stages selected by dip switches exceeding the number of FCBs, the CCB will detect
this condition and go into a hard lockout. After changing the dipswitches to the correct number of stages, the power must be

cycled on and off to accept the change.

Example of Dipswitch configuration:
GW model, 1 ignition trial, IRI, Tank Probe used, No Power Vent, No LWCO,
No Low Gas, 3 stages.

Boilers Water Heaters

Off Off = 1
Off On = 2
On Off = 3
On On = 4

Switch Position

CCB - Three position Dipswitch (Flame Control Section) SW2:
This dipswitch is similar to the FCB dipswitches described below, but with only three switches being used: the number of blower

speeds (switch #3), Hi Gas option (switch #2) and a spare (switch #1). Only the blower speed and Hi Gas options are the required
selection, within the CCB . The FCB1 always has a blower , igniter , flame checking, and the address is always st age 1, see Figure 16.

Dipswitch Function: Dipswitch Position
Switch 1: Spare:
Switch 2: Hi Gas pressure switch: On = Yes Off = N o
Switch 3: Number of Blower Speeds: On = 1 speed, Off = 2 speed

CCB-SW2

Example of Dipswitch configuration:
No High Gas, 1 blower speed.

36

FCB: Eight-Position Dipswitch

The first three switches are similar to the switch setup of SW2 on the CCB. The remaining five switches are required for the function
of igniter, blower, flame detection, and to address the firing stage. NOTE: When switch 5 is set to OFF (no blower), switch 3 (blower
speed) is ignored.

Dipswitch Function: Dipswitch Position
Switch 1: Spare:
Switch 2: Hi Gas pressure switch: On = Yes Off = No
Switch 3: Number of Blower Speeds: On = 1 speed, Off = 2 speed
Switch 4: Igniter used: On = Yes, Off = No
Switch 5: Blower used: On = Yes, Off = No
Switch 6: Flame Checked: On = Yes, Off = No
Switch 7 & 8. Stage selection: 7 8 Stage #

Off Off Not allowed
On Off 2
Off On 3
On On 4

*When switch 5 is in off (no blower) position, switch 3 (blower speeds) is ignored.

Example of Dipswitch configuration:
No High Gas, 1 blower speed, no igniter, no blower,
flame not checked, stage 4.

Operating Sequence

NOTE: The following sequence is based on a three-stage system.

1. The EMC 5000 controller has four modes of operation: Initialization,
Standby, Running, and Service. The internal CCB and FCB micros
control these modes through a sequence of steps (or States) which
are further described in the "UIM Operating Procedures" section.

2. When power is applied to the system, it enters the initialization
mode and the following automatic functions are performed:

• A. O. Smith opening screen is displayed.

• The system goes through a calibration indicated by the green

running LED blinking and then staying on; next the r e d s e r vice
LED and yellow standby LEDs come on, next the st age 1 service
and runnings LEDs blink ON and OFF followed by stage 2, stage
3, stage 4 and then back to stage 1, 2, 3, 4 LEDs.

• Stored values are recalled from memory.

• Configuration dipswitches are read.

• Pending faults are recalled

• Micros on all boards start running (indicated by a flashing

Yellow LED near each micro)

• Input sensors are read

• FCB's are configurated with the number of ignition trials to run.

3. After initialization is complete (approximately 10 seconds) the
system turns the green LED off and goes to the standby mode

(yellow "Standby" LED on), unless a previously stored fault has
been recalled, which will send the system into the service model
(red "Service" LED on). In standby mode the display shows
the temperature screen and in fault mode the current error
screen is displayed.

4. The system then compares the temperature read from the
controlling probe (inlet or tank) to the setpoint temperature. If
the temperature is less than the operating setpoint minus the
differential temperature and the thermostat input is closed then
a call for heat is established and the system shifts to the run
mode (green "Running" LED turns on).

5. The heating sequence begins by applying power to the pump
and, if selected, the powered vent and the IRI gas valve.

6. After a few seconds the blowers are turned on for 30-second
pre-purge period of combustion chamber.

7. The stage one igniter is turned on.

8. After the igniter has reached a minimum of 2.8 amps, the gas
valve is energized to allow gas flow to burners.

9. After an additional one second, the system checks the status of
the flame through the flame rod (sensor). If the flame is not
verified within 4 seconds, the gas valve is immediately shut off

37

followed by 15-second inter-purge period, then the system
returns to step 7, if the "Trial for Ignition" dipswitch is set for
three (3) tries. If the dipswitch is set for one (1) trial, the system
will declare an error and boiler will require resetting the control.

10. If a flame is detected, stage two will be activated and start its
blower. Once the blower air has been proven, igniter two will
begin trial for ignition cycle as above, (this is not the case for
model 1000, which has only one igniter).

11. Stage three will activate upon flame detection on stage two.
The gas valve will open five seconds following call for heat
and gas flow will continue if flame signal is detected. (On 4­stage firing system, the blower associated with stage three
will start and once the blower air has been proven, the ignition
cycle will take place as above. If flame is not proven, a 15­second inter-purge period will be activated followed by another
trial for ignition).

12. All stages will remain running until the set point for a given stage
is satisfied. The last stage will drop out first followed by inter­stages then stage one will drop out last. Note: Once a stage is
satisfied, the blower associated with that stage will continue for
15-second post purge period.

Example 2. Temperature begins at 90 and rises to 150, see Figure
20B. At 100 both stages are on. (This is the case when a boiler is
first started and the controlling temperature is below the operating
setpoint minus all of the differential setpoints. At that time both stages
are turned on, in sequence from 1 to 2. At 130 st age 2 turns off. At
140 both stages are off.

Stages 1 and 2 will turn on in sequence from 1 to 2.

FIGURE 20 A. FIGURE 20 B.

UIM OPERATING PROCEDURES

13. Once all the stages have been satisfied, the boiler pump will
continue to run for the programmed post-circulate cycle.

14. The control now enters the idle state as displayed by the
"Standby" LED. The control will continue to monitor heat
demand and state of other system devices. Upon a drop of
water temperature below the set parameters, the control will
return to step 5 and repeat the entire operating cycle. Note:
Any fault detection, during standby or running modes, will halt
the heating sequence and shift the system to the service mode
where the detected fault will be displayed.

NOTE: In standby and running modes the system constantly
monitors the signals and the internal operation for faults. Any
detected fault will halt the heating sequence and shift the system
to the service mode, where the detected fault will be displayed.

Temperature Setpoints (System Control Algorithm)

The boiler has a hysteresis type control, which means that it will
begin heating the water when the temperature sensed by the control
probe (inlet or tank) falls below the operating setpoint minus the
differential setpoint for stage 1. It will stop heating the water when
the temperature rises to the operating setpoint. If the system has
multiple stages then the differential setpoint for each stage is also
subtracted from the operating setpoint. The following examples
will further explain this operation.

Setup: 2 stage system, operating setpoint - 140, stage 1 to 2
differential setpoints = 10.

Example 1. Temperature begins at 150 and drops to 90, see Figure
20A. At 140 the system remains in idle mode. As the temp drop s to
130 (140-10) stage 1 turns on and stage 2 remains off. At 120 stage
2 also turns on.

FIGURE 21. UIM, USER INTERFACE MODULE

The UIM receives commands from the user and displays operational
information to the user via an LCD (liquid crystal display) up to
eleven LED's, and five touch switches. The LCD provides
information to the user by the use of 10 menu-activated screens.
Within each of the screens, helpful information can be displayed
by pressing the "Help" button. The LED's visually inform the user
about the mode the system is in. The touch switches allow the
user to control the operation of the system. The operation of these
parts is described in the following section:

UIM Screens:

On all screens a double vertical bar appears on the right side of the
display each time a key is touched to indicate that a key has been
activated. On several screens an indicator ">" appears on the left
side of the display to indicate the active line. The "Up/Down" keys are
used to move the indicator to the desired line and the "Select" key is
pressed to select the line. Also, on most of the screens, up/down
arrows appear on the right side of the screen to indicate that there is
additional lines either above or below the displayed four lines.

38

The following status information is displayed from the

Status Displayed *(T rue Condition) Input Output

ECO Outlet temperature too high open - - - ­LW/CO Water Level low open - - - ­Blk Flue Flue blocked open - - - ­Flow Water flowing closed - - - ­Low Gas Gas pressure low open - - - ­Tstat Thermostat requesting heat closed - - - ­Hi Limit Outlet temp exceeds High Limit setpoint - - - - - - - ­Pump Pump output activated - - - - On
IRI Gas Pwr IRI output relay activated - - - - On
IRI Gas IRI Gas Valve on closed - - - ­Pwr Vent Power Vent running closed - - - ­Alarm Alarm output activated - - - - On
Pwr V ent Pwr Power Vent output relay activated - - - - On

- - - - ST AGES 1 to 2 - - - ­BlwHi Prv Blower pressure sufficient closed - - - ­Blw Hi Blower High output activated - - - - On
BlwLo Prv Blower pressure sufficient (not used at this time) closed - - - ­Blw Lo Blower low output activated (not used at this time) - - - - On
Ignt Cur Igniter current sufficient for ignition - - - - - - - ­Ignit Igniter output is activated - - - - On
Gas Relay Gas output relay activated - - - - On
Hi Gas Gas pressure too high open - - - ­Flame Flame detected - - - - - - - -

System Status Screen:

• Menu Screen:
Displayed when the user presses the "Menu" key . This screen is
the selection point for the other 9 screens.

• Temperature Screen:
Displays the sensed temperatures of the Outlet, Inlet, and Tank
probes. Also displayed is the calculated Delta T (Outlet minus
Inlet) for the system. Shorted ("Short") and disconnected ("----")
probes are also displayed.

• System Status Screen:
This screen is used to view the status of switch inputs and output
states. An asterisk (*) is displayed next to the label when the
status is "True" (the description is fulfilled). For example, if water
is flowing, or detected by the flow sensor, then an "*" will appear
in front of the Flow label (i.e. *Flow). Another example would be
the ECO switch. If the outlet temperature is too high the display
will show: *ECO.

NOTE: The LWCO, IRI Gas Valve, Powered Vent, High Gas, and
Low Gas inputs are optional inputs. Flame sensing, Igniters, and
Blowers are optional on Stages 2, 3 and 4. (Except on a 4-stage
system, stage 2 always has an Igniter, Blower, and Flame Sensor.
Those dipswitches on stage 2 are not relevant.) One or two speed
blowers can be used on any stage.

The System monitors the inputs at these times:

• ECO, LWCO, Blocked Flue, Low Gas, Hi Limit, and Hi Gas - at all
times for a fault condition.

• Tstat - at all times for open/closed conditions.

• IRI Gas and Powered Vent - for an on condition when their outputs
(Pump, IRI Gas Pwr, Powered Vent Power) are turned on and an
off condition at all other times.

• Flow-for an on condition when the pump is on (no check for off state)

• Blower Prover - when the Blower is on.

• Igniter Current - for an on condition approximately 18 seconds

after the Igniter is turned on until the igniter is turned off and an
off condition at all other times.

• Flame - for an on condition approximately 5 seconds after the
gas valve is turned on until the valve is turned off and at all other
times for an off condition.

Control Status Screen:

Displays the status that the CCB and FCB micros are in. The CCB
has 5 possible states and the FCB's have 9. The normal CCB states
sequence is to move from Idle, to Pre-Circulate, then to Heating
Stage 1-2-3-4 when a call for heat is initiated. Once heat has been
satisfied or the Thermostat is opened, the sequence moves to Post­Circulate and then back to Idle. If a fault occurs at any time, the
process jumps out of sequence and goes directly to the appropriate
Hard or Soft Fault state.

Description of CCB control states:

• Idle:

The yellow "Standby" LED is turned on and the system wait s for
a heat request (determined by the Thermostat or controlling probe
inputs). All outputs are off in this state except that if the Post-Circulate
time is set to continuous, the pump will be on. When the heat request
is received, the system moves to the Pre-Circulate state.

• Pre-Circulate:

The yellow LED is turned off and the green "Running" LED is
turned on. The green LED will remain on for all other states
except the fault states. If enabled the powered vent and the IRI
gas valve are turned on. A command is sent to all active stages
to cold purge the system. Cold purging clears out any
combustion gas that may be in the combustion chamber. When
purging is complete the system moves to the Heat State.

• Heat Stages 1-2-3-4:

The system will command the FCB micros to start their heat
sequence starting with stage 1. Stage 2, 3, 4 will be activated in
order based on an algorithm that determines how much heat is
needed. The system will remain in this state until the heat request
is satisfied, the Tstat is opened, or a fault occurs.

39

• Soft Fault State: (See "Fault Description" section for list of soft
and Auto Reset faults.)

The CCB turns off the Powered V ent and the IRI Gas. The pump
remains on for the selected post-circulate time to cycle the hot
water out of the boiler. The FCB's are commanded to shut down
and the Alarm output is turned on. The green LED turns off and
the red "Service" turns on. The CCB remains in this state until
one of the following occurs:

• One hour passes (automatic restart after one hour)

• If Communications error system will automatically
restart if communications re-establishes.

• If user presses Select key while current error screen is

displayed (Hard reset).

• If high-limit error - the outlet temperature drops below the high

limit trip point minus the high limit differential. (outlet water
temperature drops to safe level). The fault is logged in the
error history when the fault state is exited.

• Hard Fault State: (See "Fault Description" section for list of

soft and Auto Reset faults.) The CCB turns off the Powered
Vent and the IRI Gas. The pump remains on for the selected
post-circulate time to cycle the hot water out of the boiler. The
FCB's are commanded to shut down and the Alarm output is
turned on. The green LED turns off and the red "Service"
turns on and off (flashes). The only way to exit this state is for
the user to press the Select key while the current error screen
is displayed. The fault is logged in the error history when the
fault state is exited.

While the CCB is in the Heating mode the activated FCB stage
moves from Idle, to Pre-Purge, to Heat Igniter, to Check for Flame,
and then to Heating. The process waits in this state until the call for
heat is satisfied, the thermostat input is opened, or a fault occurs.
When heat is satisfied, the sequence continues to Post-Purge and
then back to Idle. If three tries for ignition has been selected on the
CCB dipswitch and flame is not detected at the appropriate time,
then the sequence moves to the Inter-Purge state for 15 seconds
and the FCB heat sequence is repeated. If flame is still not detected
after the third try the process declares a fault, jumps out of sequence
and goes to the error state. Other types of faults detected at any
time will also cause a jump to the error state.

Description of FCB control states:

• Idle State:
When any error is declared during idle state-The system will
remain in this state until the CCB request a heating cycle, or a
cold purge.

• Pre-Purge State:
If the stage does not have a blower, this st ate is skipped and the
system advances to the Heat Igniter St ate. Otherwise the Blower
is turned on. After 10 to 34 seconds (34 seconds for cold
purging) the system switches to the Heat Igniter State.

• Heat Igniter State:
The sequence of operation is as follows: "The igniter relay is
energized and the heat up period begins. After 18-20 seconds,
if the igniter has reached a minimum of 2.8 amps, the gas valve
safety circuit is then activated. If in this amount of time, the igniter
fails to reach a minimum amp draw of 2.8 amps, the unit will re­cycle up to 3 times before locking out on igniter hardware failure.
If the igniter does reach the minimum required amp draw of 2.8
amps, the gas valve circuit is energized, and the system
advances to Flame Check status.

• Check for Flame State:
The gas valve is turned on. Af ter 1.5 seconds, the system checks

that the gas valve relay is on. If it is not, the ignition trial is
considered to have failed and the system advances to the Inter­Purge state, if any ignition trials remain, otherwise an error is
declared.

The flame sensor is checked. If flame is detected, the igniter is
turned off. The state machine then advances to the Heating
State. If after 5 seconds, the flame is still not sensed then the
ignition trial is considered to have failed. The state machine
advances to Inter-Purge if any ignition trials remain, otherwise
an error is declared.

• Heating State:
The system remains in this state until the call for heat is cancelled
or a fault occurs. The system returns to the Idle state if the call
for heat is cancelled, or satisfied and to the appropriate fault
state if a fault occur.

• Inter-Purge State:
The gas valve and the igniter are turned off. The blower is on.
After approximately 15 seconds the system goes back to the
Heating Igniter State.

• Post-Purge State
The gas valve and the igniter are turned off. If this stage does
not have a blower the system returns to the idle state. If it does
have a blower then the blower is left on. After approximately 25
seconds, the system returns to the Idle state.

• Error State
The gas valve and the igniter are turned off. The FCB micro tells
the CCB micro which error has occurred. The system waits in
this state until the CCB sends a command to clear the error , and
the system returns to the idle state.

• Cold Purge State
Cold purge occurs when the CCB micro commands all blowers
to go on before lighting the first stage to clear the unit of residual
gases. This state normally lasts approximately 32 seconds but
on a special situation can last up to 5 minutes. If on the first call
for heat after power up, blower prover switch is open, this state
will take up to 5 minutes before declaring an error. This special
mode is used by service technicians to adjust the blower shutter.

The CCB will wait the normal cold purge time (normally 32
seconds) before checking for activation of all active blower prover.
If blower prover is active at this time the CCB cancels the cold
purge request. After the first cold purge has been done a flag is
set to prevent further activation of the shutter adjust 5 min. delay .
Any further requests for cold purge will last the normal cold
purge time. The FCB will go into fault mode if the blower prover
does not activate after 15 seconds. This time allows the blower
relay to activate, the blower to come up to speed, and the
response from the blower prover to be filtered.

• User Settings Screen:
Each setpoint or user setting has either a limited selection of
values, or a limited range of values. The Up/Down keys are
used to change values. Af ter changing an item, the Select key is
pressed to accept the change, or the Menu key is pressed to
reject the change and restore the item to its original value. The
following setpoints can be changed:

• Operating Setpoint:
This setpoint sets the base temperature for the control algorithm.
See Figures 20A & 20B.

40

OPERA TING SETPOINT ADJUSTMENT PROCEDURE

The system has a standard programmable Operating Setpoint range
of 70 Degrees F to 190 Degrees F for a GW and of 70 Degrees F to
220 Degrees F for a GB for either tank or inlet probe depending on
selection. The user can easily change the Operating Setpoint at any
time by using the following procedure. When any configuration or
setpoint is changed (and the Select key touched), the new value is
IMMEDIATELY saved to non-volatile memory. The factory default
setting is 120 Degrees F.

1. Touch the MENU key .

2. Scroll the ">" with the DOWN key next to the USER SETTING
SCREEN.

3. Touch the SELECT key.

4. Scroll the ">" with the DOWN key until it is pointing to OPERATING
SETPOINT.

5. Touch the SELECT key.

6. Use the UP or DOWN key to select the value you wish to enter.

7. Touch the SELECT key to accept and store the new value.

• High Limit:
The outlet temperature probe contains both an ECO switch and
a thermistor for temperature measurement. The sensed outlet
temperature is used for the automatically resettable High Limit
setpoint. If the sensed outlet temperature exceeds the High
Limit setpoint, a "soft lockout" condition will occur and the burner
will be shut off. This fault condition is automatically cleared
when the temperature drops below the high limit setpoint minus
the high limit differential.

AUTO HIGH LIMIT SETPOINT ADJUSTMENT PROCEDURE/
OUTLET TEMP . PROBE

The High Limit setpoint has a range of 90 Degrees F to 210
Degrees F for a GW and a range of 90 Degrees to 235 Degrees F
for a GB. Use the following procedure to change the automatically
resettable High Limit Setpoint:

1. Touch the MENU key .

2. Scroll the ">" with the DOWN key next to USER SETTING
SCREEN.

3. Touch the SELECT key.

4. Scroll the ">" with the DOWN key until it is pointing to HIGH LIMIT
SETPOINT.

5. Touch the SELECT KEY.

6. Use the UP and DOWN key to select the value you wish to enter .

7. Touch the SELECT key to accept and store the new value.

• High Limit Differential:
The outlet temperature must be below the automatic High Limit
setpoint minus the High Limit Differential setpoint before a call
for heat can be generated.

HIGH LIMIT DIFFERENTIAL SETPOINT

ADJUSTMENT PROCEDURE

The High Limit Differential Setpoint has a range of 1 Degree F to 50
Degrees F for all models. Use the following procedure to change
the High Limit Differential Setpoint:

1. Touch the MENU key .

2. Scroll the ">" with the down key next to USER SETTING SCREEN.

3. Touch the SELECT key.

4. Scroll the ">" with the DOWN key until it is pointing to HIGH LIMIT
DIFFERENTIAL SETPOINT.

5. Touch the SELECT key.

6. Use the UP or DOWN key to select the value you wish to enter.

7. Touch the SELECT key to accept and store the new value.

• Operating Differential Setpoints:
Each of the two stages has an independent Operating
Differential setpoint.

OPERA TING DIFFERENTIAL SETPOINT

ADJUSTMENT PROCEDURE

Each of the two stages has an independent Operating Differential
Setpoint. The range of these setpoints is from 1 Degree F to 50
Degrees F for all models. Use the following procedure to change
this setpoint:

1. Touch the MENU key .

2. Scroll the ">" with the DOWN key next to USER SETTING
SCREEN.

3. Touch the SELECT key.

4. Scroll the ">" with the DOWN key until it is pointing to OPERATING
DIFFERENTIAL SETPOINT .

5. Touch the SELECT key.

6. Scroll the ">" with the DOWN key until it is pointing to the ST AGE
you want.

7. Touch the SELECT KEY.

8. Use the UP and DOWN key to select the value you wish to enter .

9. Touch the SELECT key to accept and store the new value.

• T emperature Unit s:
Temperature can be displayed in either °F or °C units.

• Post Circulate Delay Time:
The time circulation pump will stay on after the burner is turned
off. The time in seconds is adjustable with the following values:
45, 90, 180 or continuous. If the continuous value is selected
the pump will remain on at all times and the post circulate state
time will be set at 45 seconds.

• Network Address:
This is a unique number assigned to this boiler to differentiate
it from other boilers or water heater on the same A. O. Smith
proprietary network. A valid Network Address can be any number
from 1 to 31. It is set by default to zero, which is an invalid address.
The boiler will not communicate until it is changed to a valid and
unique number. This prevents two units from trying to respond to
the same request from the PC or supervisory network device.

• Configuration Settings Screen:
Displays the status of the dipswitches installed on all boards
as described earlier.

• Log & System Info Screen:
Displays the following information:
Elapsed hours of operation (Total time system has been
powered up)
Number of running minutes (Number of minutes system has
been in the run mode)
Number of cycles for each stage (Number of times stage has
been in heat mode).
kBtu rating of the boiler (0 to 5750kBtu in 10kBtu increments)
The software revision level of the CCB, and FCB
microcontrollers.

Current Error Screen:

• Displays the last error that the system has detected plus a time
stamp of when the error occurred. (The time stamp is based on
the elapsed hours value at the time the error occurred. It is
displayed in hours and minutes. This error remain displayed
as long as it is still valid. When cleared it is moved to the Error
History Screen. The system will automatically jump to this screen

41

when an error is detected. It will also go to this screen upon
power-up if an error was still valid when power was turned off.

NOTE: Errors are cleared from this screen by pressing the
"select" key.

• Error History Screen:

This screen displays a list of the last 9 errors (with time stamps)
that have occurred. The last error to occur is displayed first. If a
new error occurs this screen is presented to display the error.

• Reload Defaults Screen:

From this screen the user can restore the factory default values
for screen adjustable configurations by pressing the Select key.
The values restored are as follows:

GW Models
Oper Setpnt (Operating Setpoint) - 145° F (63° C)
Stage1 Diff (Operating Setpoint Differential) = 3° F (2° C)
Stage2 Diff (Operating Setpoint Differential) = 6° F (3° C)
Hi Limit (High LImit Setpoint) = 210° F (99° C)
Hi Limit Dif (High Limit Differential) = 20° F (11° C)

• Up and Down Keys:
These keys are used to move upwards and downwards in
screens to reach a desired item and to change setpoints and
user settings. They have an auto increment/decrement feature
for some of the configurations and values. When you first press
one of the keys and value changes by 1 count, then wait 1/2
second and changes slowly until the key is released or if held
for 3 or more seconds it will change the value quickly.

• Help Key:
Pressing the Help key from any screen displays helpful
information about that screen. From the menu screen, general
help information is displayed as to how to use the user interface.
To return to the previous screen press the Help or Select keys,
or press Menu key to go to the menu screen. If a small down
arrow appears in the lower right hand corner then there is off
screen content below what is displayed. Press the down arrow
to scroll down to this information. After scrolling down an up
arrow will appear in the upper right hand corner to indicate off
screen content above what is displayed.

GB Models
Oper Setpnt (Operating Setpoint) = 190° F (88° C)
Stage1 Diff (Operating Setpoint Differential) = 3° F (2° C)
Stage2 Diff (Operating Setpoint Differential) = 6° F (3° C)
Hi LImit (High LImit Setpoint) = 230° F (110° C)
Hi Limit Dif (High Limit Differential) = 20° F (11° C)

Both Models
Tempert Units (Temperature Units) = F
Post Cir Secs (Post Circulation pump delay = 45 seconds
Network Address (Network Address) = (none)

UIM Touch Switches

Below the LCD display are five touch switches or keys, that the
operator uses to operate the system.

• Menu Key:
Pressing this key activates the menu screen where the other
screens can be accessed.

• Select Key:
This key performs several functions. Screens can be selected
from the menu screen by pressing this key when the">" appears
next to the screen desired.

On the User Settings screen items that appear next to a ">"
symbol can be selected with this key . If a setpoint configuration
item is selected, the ">" will then flash slowly to indicate that the
item has been selected. The Up and Down keys are then used
to change its value.

From the Current Error Screen this key is used to reset the
system from an error:

UIM LED's

The three LED's to the right of the LCD indicate the status of the
overall system. The red LED indicates that a fault has been detected
and the system has stopped running. It is on continuously for soft
faults and flashes for hard faults. The Yellow LED indicates that
the boiler is in a ready mode waiting for a call for heat command.
When on continuously the Green LED indicates that the system is
in the heating mode. If it is flashing it indicates that the UIM is in the
initialization mode and the touch switches are being calibrated.

On these boilers there are also eight LED's on the lower right that
indicate the state of the individual FCB's. The red LED's are only on
when the main red LED is on and indicate which FCB has the error.
The green LED indicates when flame is proved on that particular
stage, unless the dipswitch for sensing flame is turned off. Then
the LED indicates that the gas valve has turned on.

Fault Messages and Troubleshooting Guide

The EMC5000 system does excessive self-diagnostics and
displays detected faults on the UIM display in an easy to read
manner. There are approximately 80 different faults that can be
detected. Some of the faults are caused by internal problems and
some by external causes. The faults create different types of system
lockouts (shut down). Hard lockouts are serious problems that
require the user to manually restart system. Soft lockouts can be
reset by the user or after 60 minutes the system will automatically
clear the error and restart. Auto Reset lockouts will monitor the
cause of the fault and if the fault clears itself the system reset itself.
The fault is recorded and the system immediately resets itself.
The following table shows the fault messages and some possible
troubleshooting hints:

TROUBLESHOOTING IGNITION SYSTEM

Fault Messages and Lockout Status (* = stage number: 1, 2, 3, or 4)

FAUL T DISPLA YED DESCRIPTION RED LED LOCKOUT
“Display Fail” Communications with UIM interrupted Continuous Auto Reset

Check communication cable to UIM. Try moving to other Internal Communications connector on CCB.
Also check the connectors where the cable is plugged in for best connecting wires.

“Comm. Fail Stg.*” Communications with FCB interrupted Continuous Auto Reset

Same as above. Also try swapping FCB and UIM communications cables.

“Low AC Voltage” Line voltage less than 90 vac Continuous Auto Reset

Check incoming power line for loss of voltage. May also be caused by a power line brown-out (momentary
loss of voltage)

42

“Low 24VAC” Voltage from transformer less than 18 vac Continuous Auto Reset

Check transformer output. Should be over 24vac. May be caused by
excessive current drain or a faulty transformer

“Brown Out Reset” Indicates a brown out reset occurred - - - - None

Caused by a momentary dip in voltage on the CCB +5vdc power bus. Contact factory. (Not considered a
serious problem if it only occurs on very rare occasions.)

“Timeout Reset” Indicates a watchdog reset occurred - - - - None

Caused when the micro executes the software in an improper way. Contact factory. (Not considered a
serious problem if it only occurs on very rare occasions.)

“FCB Comm Timeout” FCB did not receive command from CCB Continuous SOFT

Caused when communications between the CCB and the FCB are interrupted. May occur when a surge of
power on a nearby device (i.e. arc welder) creates an EMI burst. Not a serious problem if it occurs rarely.

“No Flow” Water is not flowing Continuous SOFT

Caused by the flow switch being open when it should be closed. Check water lines, pump, flow switch
contacts, wiring.

“Blower Prov Stg* Blower pressure is too low it they should have been closed. Continuous SOFT

Check blower, switch contact, wiring, and for air leaks.

“Blocked Flue” Flue is Blocked Continuous SOFT

Caused by the blocked flue switch contacts being open when they should have been closed. Check for flue
blockage, switch contacts, wiring.

“High Limit” Outlet temp. exceeded high limit setpoint Continuous Auto Reset

Caused when the temperature of the outlet probe exceeds the high limit setpoint. This is an internal
“software” limit switch and not an actual device. Check that the over temperature is not being caused by
improper setup or operation of the boiler.

“ECO fault” Outlet temp is too high Flashing HARD

Caused when the ECO (a thermostat) contacts in the Outlet probe are open when they should be closed.
Fault may be due to high outlet temperature, bad switch contacts in the ECO, or disconnected wiring. Note:
The ECO can be checked by disconnecting the outlet probe from the CCB and reading the resistance
across the two active pins on the connector at the end of the probe cable. The value should be approximately
0 ohms when the temperature of the probe is less than 220°F.

“Low Water” Water level is too low Flashing HARD

Caused by the Low Water Cut Out device not closing its feedback switch contacts when it should. Check
water line, switch contacts, wiring, LWCO.

“Low Gas” Gas pressure is too low Flashing HARD

Caused by the Low Gas switch being open when it should be closed. Check gas line, switch contacts,
wiring.

“IRI Gas” IRI Gas V alve did not turn on Flashing HARD

Caused by the IRI Gas Valve not closing its feedback switch contacts when it should. Could also be caused
by a problem with the relay output on the CCB. Check output to IRI Gas Valve, switch contacts, wiring.

“Powered Vent” Power vent not running Flashing HARD

Caused by the Powered Vent device not closing its feedback switch contacts when it should. Could also be
caused by a problem with the relay output on the CCB. Check output to powered vent, switch contacts, wiring.

“High Gas Stg*” Gas pressure too high Flashing HARD

Caused by the High Gas switch being open when it should be closed. Check gas line, switch contacts, wiring.

“Inlet Probe” Inlet probe shorted or open Flashing HARD

Caused when the thermistor in the probe or the wiring to the probe is shorted or disconnected. Check the
probe. Note: The thermistor and wiring can be checked by disconnecting the probe from the CCB and
reading the resistance across the two active pins on the connector at the end of the probe cable. The value
should be approximately 10K ohms (value will change slightly with changes in temperature).

“Outlet Probe:” Outlet probe shorted or open Flashing HARD

Caused when the thermistor in the probe or the wiring is shorted or disconnected. Check the probe. Note:
the thermistor and wiring can be checked by disconnecting the probe from the CCB and reading the
resistance across the two active pins on the connector at the end of the probe cable. The value should be
approximately 10K ohms (value will change slightly with changes in temperature).

43

“Tank Probe” Tank (Remote) probe shorted or open Flashing HARD

Caused when the thermistor in the probe or the wiring is shorted or disconnected. Check the probe. Note:
the thermistor and wiring can be checked by disconnecting the probe from the CCB and reading the
resistance across the two active pins on the connector at the end of the probe cable. The value should be
approximately 10K ohms (value will change slightly with changes in temperature).

“Igniter Stg*” Igniter current is too low Flashing HARD

Caused by a low current draw problem with the igniter. This may occur if the igniter is old, damaged, or
disconnected and no longer draws the proper level of current. This condition will affect the ability of the
igniter to get hot enough to fire the gas properly. Check the igniter and its associated wiring.

“Igniter Pwr Stg*” Improper power applied to the igniter circuit Flashing HARD

Caused by improper line power being applied to the igniter circuitry. Check line connections.
Paying particular attention to the earth ground connection. Also check that line voltage does not exceed 132
vac rms.

“Igniter Hdwr Stg*” Hardware problems with igniter circuit Flashing HARD

PREVENT ATIVE MAINTENANCE

This is an induced burner and the flame is not supposed to be directly
on the burner. The flame should be just above the burner deck
approximately 1/8” and blue in color. See Figure 22.

Visually check flame characteristics through the view port located
under the left-hand header on the boiler. Figure 22 shows the
normal flame condition. Also, refer to the flame label on the unit
(adjacent to the view port).

These boilers are designed to give many years of efficient and
satisfactory service when properly operated and maintained.
To assure continued good performance, the following
recommendations are made.

The area around the unit should be kept clean and free from lint
and debris. Sweeping the floor around the boiler should be done
carefully. This will reduce the dust and dirt which may enter the burner
and heat exchanger, causing improper combustion and sooting.

MAIN BURNERS

Check main burners every three months for proper flame
characteristics. The main burner should display the following
characteristics:

• Provide complete combustion of gas.

3. Check that burner venturi and ports are free of foreign matter.

4. Clean burners with bristle brush and/or vacuum cleaner. DO NOT
distort burner ports.

5. Reinstall burners in unit. Ensure that all the screws on the
burner flange are tightened securely so that the gasket will
provide a good seal. Also, ensure that each orifice is
centered with the venturi opening of every burner. The

washer of the orifice must be inserted a minimum of 1/4"
into the burner tube. This is critical for proper operation.
See Figure 23.

6. Also check for good flow of combustion and ventilating air to
the unit.

Figure 22. Normal Flame Characteristics

• Cause rapid ignition and carry over of flame across entire burner.

• Give reasonably quiet operation during initial ignition, operation

and extinction.

• Cause no excessive lifting of flame from burner ports. See Figure 22.

If the preceding burner characteristics are not evident, check for
accumulation of lint or other foreign material that restricts or blocks
the air openings to the burner or boiler. To check burners:

1. Shut off all gas and electricity to unit. Allow unit to cool.

2. Remove main burners from unit.

Figure 23. Orifice Insertion

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After placing the boiler in operation, check the ignition system safety
shut-off devices for proper operation. To accomplish this with the
main burners operating, close the valve on the manifold. Within
four seconds the main burners should extinguish. If this does not
occur immediately, discontinue gas supply by closing main manual
shut-off and call a qualified serviceman to correct the situation. If
the burners extinguish, then light boiler in accordance with lighting
and operating instructions.

For installations above 4,500 feet (1350 m), refer to HIGH ALTITUDE
INSTALLATIONS in the installation section. See page 5.

any dirt and lint that may have accumulated in the compartment or
on the blower and motor. Buildups of dirt and lint on the blower
and motor can create excessive loads on the motor resulting in
higher that normal operating temperatures and possible shortened
service life.

VENTING MAINTENANCE

It is recommended that the intake and exhaust piping of the
appliance be checked every 6 months for dust, condensate leakage,
deterioration and carbon deposits.

THE FLOW OF COMBUSTION AIR TO THE BOILER MUST NOT BE
OBSTRUCTED.

THE BOILER AREA MUST BE KEPT CLEAR AND FREE FROM
COMBUSTIBLE MATERIALS, GASOLINE AND OTHER FLAMMABLE
VAPORS AND LIQUIDS.

Any safety devices including low water cutoffs used in conjunction
with this boiler 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. Periodic checks, at least
twice a year, should be made for water and/or gas leaks.

More frequent inspections may be necessary depending on water
conditions.

The boiler-mounted gas and electrical controls have been designed
to give both dependable service and long life. However, malfunction
can occur, as with any piece of equipment. It is therefore
recommended that all components be checked periodically by a
qualified serviceman for proper operation.

RELIEF VAL VE

The safety relief valve should be opened at least twice a year to
check its working condition. This will aid in assuring proper
pressure relief protection. Lift the lever at the top of the valve several
times until the valve seats properly and operates freely.

DANGER

THE WATER PASSING OUT OF THE V ALVE DURING CHECKING
OPERATION MAY BE EXTREMELY HOT. BEFORE OPERATING
RELIEF V ALVE, MAKE SURE DRAIN LINE IS INST ALLED TO DIRECT
DISCHARGE TO A SAFE LOCATION SUCH AS AN OPEN DRAIN,
TO A VOID SCALDING OR W A TER DAMAGE.

WARNING

SHOULD OVERHEA TING OCCUR OR THE GAS SUPPL Y F AIL T O
SHUT OFF, TURN OFF THE MANUAL GAS CONTROL V ALVE TO
THE APPLIANCE.

COMBUSTION AIR FILTER

WARNING

DO NOT USE A NYLON BRUSH OR OTHER ST ATIC CREATING
MA TERIAL TO CLEAN DUST AND CARBON DEPOSITS FROM
HEATING SURFACES AND VENT. SUCH DEPOSITS ARE
FLAMMABLE AND MAY BE IGNITED BY STATIC ELECTRICITY.
USE A METAL BRUSH TO MINIMIZE THE DANGER OF
EXPLOSION.

Qualified serviceman should follow this procedure when the boiler's
intake and exhaust piping need cleaning:

1. Turn off the electrical power, and manual gas shut-off.

• Allow boiler parts to cool before disassembly.

2. Remove the vent pipe.

• Check parts and chimney for obstructions and clean as
necessary.

3. Remove burners from boiler and other metal parts as required
to clean as necessary.

• Refer to parts list for disassembly aid.

4. Clean and reinstall the parts removed in steps 2 and 3.

• Be sure the vent pipe has a minimum upward pitch of 1/4"

per foot (2 cm/m) of length and is sealed as necessary.

5. Restore electrical power and gas supply to boiler.

• Check for gas leaks and proper boiler and vent operation.

HEA T EXCHANGER PREVENTIVE MAINTENANCE

In most water supply systems solids exist. As the water is
heated, these tend to drop out depositing as scale or lime.
This scale must be removed before the heat exchanger tubes
become blocked.

CAUTION

LIME ACCUMULATION CAN REDUCE THE LIFE OF THE
EQUIPMENT , REDUCE EFFICIENCY AND W ASTE FUEL. BOILER
FAILURE DUE TO LIME OR SCALE BUILDUP VOIDS THE
WARRANTY.

If the combustion air supply to the boiler contains dust, dirt, drywall
dust etc. a filter must be installed. An air filter is not supplied with the
boiler as shipped from the factory . The installer must provide a filtering
system in the air inlet to the boiler if dust, dirt or construction dirt can
be pulled into the boiler through the inlet air piping. Periodically clean
air filter per the manufacturer's instructions.

BLOWER COMP ARTMENT

The blower compartment should be cleaned annually to remove

DELIMING

The amount of calcium carbonate (lime) released from water is in
direct proportion to water temperature and usage. The higher the
water temperature or water usage, the more lime deposits are
dropped out of the water. This is the lime scale which forms in
pipes, boilers and on cooking utensils.

The usage of water softening equipment greatly reduces the
hardness of water. However , this equipment does not always remove

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all of the hardness (lime). For this reason it is recommended that a
regular schedule for deliming be maintained.

The time between cleaning will vary from two to six months
depending upon water conditions and usage. A change of
approximately 5
the boiler is usually an indication that scale should be removed.
For long life, copper or brass is recommended for all valves, pipe
and fittings.

Establish a regular inspection schedule, the frequency depends
on the local water conditions and severity of service. Do not let
the tubes clog up solidly. Clean out deposits over 1/16" (1.6
mm) thickness.

To service heat exchanger tubes, remove return header casting
on the side opposite the water connections. Use a U.S. standard
5/8" deep socket ratchet to remove the nuts, exposing the tube
ends. Inspect to ensure tubes are free of scale and deposits.
If scaled, remove deposits with a stiff wire brush or mechanical
tube cleaner to bare metal. Reinstall return header casting.
Flush system.

Note: Removal of the heat exchanger is not required.

o

F (3°C) in the normal temperature rise through

TUBE CLEANING PROCEDURE

MECHANICAL REMOV AL OF DEPOSITS

CAUTION

IF HEAT EXCHANGER MAINTENANCE REQUIRES TUBING
REPLACEMENT, SPECIAL PROVISIONS SHALL BE TAKEN TO
ENSURE THA T THE DAMAGED TUBES ARE CAREFULLY REMOVED.

REPLACEMENT TUBES MUST BE PROPERLY INSTALLED AND
EXP ANDED INTO THE ROLLED TUBE TUB.

OVER-ROLLING, MISALIGNMENT OF TUBES OR IMPROPER
TIGHTENING OF THE ASSEMBLY MAY RESULT IN LEAKS OR
DAMAGE TO THE HEAT EXCHANGER. CONTACT YOUR
A. O. SMITH DEALER FOR DETAILED INSTRUCTIONS.

REPLACEMENT P ARTS

Replacement parts may be ordered through A. O. Smith dealers,
authorized servicers or distributors. Refer to the Yellow Pages
for where to call or contact (in United States) the A. O. Smith

Water Products Company, 500 Tennessee Waltz Parkway,
Ashland City, TN 37015, 1-800-433-2545 or (in Canada)
A. O. Smith Enterprises Ltd., 768 Erie Street, Stratford,
Ontario, Canada N5A 6T3, 519-271-5800. 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 (P/N 212513-000) for more information.

For T echnical Assist ance call A. O. Smith T echnical Information
Center at 1-8 00 -527-195 3.

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NEW BOILER LIMITED W ARRANTY

A. O. Smith Corporation, the warrantor, extends the following LIMITED WARRANTY to the owner of this hydronic boiler:

1. If within TEN years after initial installation of the boiler, the heat exchanger shall prove upon examination by the warrantor to be defective in material
or workmanship, the warrantor, at his option, will exchange or repair such part or portion. This term is reduced to FIVE years if this boiler is used for
volume hot water supply purposes other than hydronic space heating.
a. This warranty is extended to the owner for all other parts or portion during the FIRST year following initial installation of this boiler.
b. The warranty on the repair or replacement of the part or portion will be limited to the unexpired term of the original warranty.

2. CONDITIONS AND EXCEPTIONS
This warranty shall apply only when the boiler is installed in accordance with local plumbing and building codes, ordinances and regulations, the
printed instructions provided with it and good industry practices. In addition, an appropriately sized safety relief valve certified to the ASME Boiler and
Pressure Vessel Code must have been installed and fresh water used for filling and makeup purposes;
a. This warranty shall apply only when the boiler is used:

(1 ) at temperatures not exceeding the maximum setting of its operative and/or high limit control;
(2 ) at water pressure not exceeding the working pressure shown on the boiler;
(3 ) when filled with boiler water, free to circulate at all times and with the heat exchanger free of damaging scale deposits;
(4 ) in a noncorrosive and non-contaminated atmosphere;
(5 ) in the United States, its territories or possessions, and Canada;
(6) at a water velocity flow rate, not exceeding or below the Boiler's designed flow rates;
(7) in properly sized piping system in accordance with A.O. Smith WPC sizing guidelines.

b. Any accident to the boiler, any misuse, abuse (including freezing) or alteration of it, any operation of it in a modified form will void this warranty.

3. SERVICE AND REPAIR EXPENSE
Under this limited warranty the warrantor will provide only a replacement part. The owner is responsible for all other costs. Such costs may include
but are not limited to:
a. Labor charges for service removal, repair or reinstallation of the component part;
b. Shipping, delivery, handling, and administrative charges for forwarding the replacement part from the nearest distributor and returning the

claimed defective part to such distributor;

c. All cost necessary or incidental for any material and/or permits required for installation of the replacement.

4. LIMITATIONS ON IMPLIED W ARRANTIES
Implied warranties, including any warranty of merchantability imposed on the sale of this boiler under state law are limited to one (1) year duration
for the boiler or any of its parts. Some states or provinces do not allow limitations on how long an implied warranty lasts, so the above limitation may
not apply to you.

5. CLAIM PROCEDURE
Any claim under the warranty should be initiated with the dealer who sold the boiler, or with any other dealer handling the warrantor’s products.
If this is not practical, the owner should contact:

A. O. Smith Water Products Company A. O. Smith Enterprises Ltd.

a. The warrantor will only honor replacement with identical or similar parts thereof which are manufactured or distributed by the warrantor.
b. Dealer replacements are made subject to in-warranty validation by warrantor.

6. DISCLAIMERS
NO OTHER EXPRESS WARRANTY HAS BEEN OR WILL BE MADE ON BEHALF OF THE WARRANTOR WITH RESPECT TO THE MERCHANT ABILITY OF
THE BOILER OR THE INST ALLATION, OPERA TION, REP AIR OR REPLACEMENT OF THE BOILER. THE WARRANTOR SHALL NOT BE RESPONSIBLE
FOR WA TER DAMAGE, LOSS OF USE OF THE UNIT , INCONVENIENCE, LOSS OR DAMAGE T O PERSONAL PROPERTY OR OTHER CONSEQUENTIAL
DAMAGE. THE WARRANTOR SHALL NOT BE LIABLE BY VIRTUE OF THIS W ARRANTY OR OTHERWISE FOR DAMAGE TO ANY PERSONS OR
PROPERTY , WHETHER DIRECT OR INDIRECT , AND WHETHER ARISING IN CONTRACT OR TORT .
a. Some states or provinces do not allow the exclusion or limitation of the incidental or consequential damage, so the above limitations or exclusions

may not apply to you.

b. This warranty gives you specific legal rights, and you may also have other rights which vary from state to state or province to province.

Fill in the following for your own reference. Keep it. Registration is not a condition of warranty. The model and serial number are found on the boiler’s
rating plate.

Owner_____________________________________________________________________________________________________________________

U.S. Customers Canadian Customers

500 Tennessee Waltz Parkway P. O. Box, 310 - 768 Erie Street

Ashland City, TN 37015 Stratford, Ontario N5A 6T3

Telephone: [phone] Telephone: [phone]

Installation Address___________________________________________________________________________________________________________
City and State or Province____________________________________________________Postal/Zip Code____________________________________
Date Installed__________________________Model No.______________________________Serial No.________________________________________
Dealer’s Name_______________________________________________________________________________________________________________
Dealer’s Address________________________________________________________________Phone No. ____________________________________

FILL IN W ARRANTY AND KEEP FOR FUTURE REFERENCE

47

500 Tennessee Waltz Parkway, Ashland City, TN 37015

Phone: [phone]

ww w.hotwater.com E-Mail: [e-mail]

48