A.O. Smith GVRL300, GCVT300, GCV301, GCVH301, GVR301 Service Handbook

Service Handbook

Residential FVIR
Gas Water Heaters

MODELS:

GCV, GCVH, GVR, GCVL, GVRL, GCVT - SERIES 300/301

XCV, XVR, XCVL, XGV, XVRL, XCVT - SERIES 300/301

THIS SERVICE HANDBOOK IS FOR USE BY QUALIFIED SERVICE PROFESSIONALS ONLY.

LOW LEAD

CONTENT

327726-001

May 2014

TABLE OF CONTENTS

General Safety .................................................................................................................................................... 4

Completed Installation (typical) ......................................................................................................................... 6

System Basics ..................................................................................................................................................... 7

Honeywell® Gas Control Valve/Thermostat ............................................................................................................................ 7

Gas Pressures ............................................................................................................................................................ 7

BASICS

BASICS

Combustion Chamber with TCO Switch .................................................................................................................................. 8

Lighting the Pilot / Diagnostic Flash Codes ......................................................................................................... 9

Lighting the Pilot: ................................................................................................................................................................... 9

If the Status Light Does Not Blink: ........................................................................................................................................... 9

If the Pilot Does Not Light: ...................................................................................................................................................... 9

If the Pilot Lights but the Status Light Does Not Blink: ............................................................................................................ 9

Diagnostic Flash Codes .......................................................................................................................................................... 10

Temperature Settings ................................................................................................................................................ 7

0 Flashes (LED not lit) ............................................................................................................................................ 10

Status Light On (solid) ........................................................................................................................................... 10

1 Flash ..................................................................................................................... .............................................. 10

2 Flashes ................................................................................................................................................................ 10

4 Flashes ................................................................................................................................................................ 10

5 Flashes ................................................................................................................................................................ 10

7 Flashes ................................................................................................................................................................ 10

8 Flashes ................................................................................................................................................................ 10

System Checks .................................................................................................................................................. 11

Draft Test .............................................................................................................................................................................. 11

Connections Check ................................................................................................................................................................ 11

Gas Pressure Checks .............................................................................................................................................................. 11

Thermopile Check (Open Circuit) .......................................................................................................................................... 12

Thermopile Check (Closed Circuit) ........................................................................................................................................ 12

Common Issues ................................................................................................................................................ 13

No Hot Water ........................................................................................................................................................................ 13

Not Enough Hot Water .......................................................................................................................................................... 13

Lower Seasonal Water Temperatures ....................................................................................................... 13

Faulty Shower Control Valve/Faucet Valve ............................................................................................... 14

Thermostat Set Too Low ........................................................................................................................... 14

An Increase in Hot Water Usage ............................................................................................................... 14

Undersized Water Heater ......................................................................................................................... 14

Reversed Water Connections ................................................................................................................... 14

Leak in the Plumbing System ................................................................................................................. 14

Sediment Buildup in the Tank ................................................................................................................... 14

2 • Residential Standard Gas Water Heater Service Handbook

2 • Residential Standard Gas Water Heater Service Handbook

2 • Residential Standard Gas Water Heater Service Handbook

Tank Leak ............................................................................................................................................................................... 15

Condensation .......................................................................................................................................................... 15

Leaking Plumbing Connections ............................................................................................................................... 15

Drips from the T&P Relief Valve Discharge Pipe ..................................................................................................... 15

Temperature Too High ........................................................................................................................................................... 16

Low Water Pressure .............................................................................................................................................................. 16

Water Odor ........................................................................................................................................................................... 16

Service Procedures ........................................................................................................................................... 17

Removing the Manifold/Burner Assembly ............................................................................................................................ 17

Removing the Burner from the Manifold/Burner Assembly ................................................................................................. 17

Replacing the Pilot/Thermopile Assembly ............................................................................................................................ 17

External Inspection and Cleaning of the Base-Ring Filter ..................................................................................................... 18

Cleaning the Combustion Chamber and Flame Arrestor....................................................................................................... 18

Replacing the Manifold/Burner Assembly ............................................................................................................................ 19

Testing the Igniter System ..................................................................................................................................................... 19

Removing and Replacing the Gas Control Valve/Thermostat ................................................................................................ 20

Removing the Gas Control Valve/Thermostat: ........................................................................................................ 20

Replacing the Gas Control Valve/Thermostat: ........................................................................................................ 20

Draining and Flushing ............................................................................................................................................................ 20

BASICS

BASICS

Supplements..................................................................................................................................................... 21

Evaluating Combustion and Ventilation Air Supply ............................................................................................................... 21

Attic Installations .................................................................................................................................................................. 23

Overview ................................................................................................................................................................. 23

Pilot Outage .................................................................................................................. .......................................... 23

Elevated Air Temperature: ........................................................................................................................ 24

Insufficient Makeup Air ............................................................................................................................ 24

Blocked Air Screen or Flame Arrestor ....................................................................................................... 24

Improper Venting of the Water Heater .................................................................................................... 24

Decompression ........................................................................................................................................ 25

Wind ........................................................................................................................................................ 25

Water Damage .................................................................................................................. ...................................... 25

Elevated Water Temperature .................................................................................................................................. 25

Field Installation of Draft Hoods ........................................................................................................................................... 26

Tools and Materials ................................................................................................................................................. 26

Types of Draft Hoods Covered in this Section ......................................................................................................... 26

Types of Vent Pipe Covered in this Section ............................................................................................................. 27

Installation Procedure ........................................................................................................ ..................................... 27

Coupling .................................................................................................................................................................. 27

Type B Draft Hood Connectors ................................................................................................................................ 28

Residential Standard Gas Water Heater Service Handbook • 3

Residential Standard Gas Water Heater Service Handbook • 3

Residential Standard Gas Water Heater Service Handbook • 3

GENERAL SAFETY

Your safety and the safety of others is extremely important in the servicing of this water heater. Many safety-related messages and
instructions have been provided in this handbook and on your water heater to warn you and others of a potential hazard. Read
and obey all safety messages and instructions throughout this handbook as well as those found in the Installation Instructions/
Use & Care Guide.

It is very important that the meaning of each safety message is understood by you and others who service this water heater.
The information contained in this handbook is designed to answer commonly faced situations encountered in the operation of
the standard Residential Gas product line and is not meant to be all-inclusive. If you are experiencing a problem not covered in

BASICS

BASICS

this handbook, please contact the Technical Information Center listed on the back cover of this handbook for further assistance.
Additional information is also available on the web site listed on the back cover of this handbook.

This handbook is intended for use by licensed plumbing professionals and reference should be made to the Installation Instructions
and Use & Care Guide accompanying the product. This handbook contains supplemental information to the Installation Instructions
and Use & Care Guide.

When servicing residential water heaters, it is essential that you return the unit to a safe condition before you leave the site. All
original components must be re-installed and all safety measures must be implemented. In addition, the recommended water
temperature setting is 120° F.

IMPORTANT: It is recommended that on every service call, an inspection & cleaning of the base ring filter and flame arrestor be
performed. See page 18.

Tools Required (for servicing gas models):

• Phillips head screw driver

• 3/8, 7/16, & 3/4 inch open end wrenches

• 3/16 inch Allen wrench

• 1-1/16 inch – 6 point – socket – for anode removal

• Electrical multimeter (with alligator leads)

• Digital or analog manometer

• Gas pressure gauge

• Water pressure gauge

• Thermometer

• Hose – to drain tank

• Container – to measure gallons per minute flow

Digital Manometer

4 • Residential Standard Gas Water Heater Service Handbook

4 • Residential Standard Gas Water Heater Service Handbook

Fire or Explosion Harzard

Do not store or use gasoline or other flammable vapors and
liquids in the vicinity of this or any other appliance.

Avoid all ignition sources if you smell Natural or LP gas.
Do not expose water heater control to excessive gas
pressure.

Use only gas shown on rating plate.
Maintain required clearances to combustibles.
Keep ignition sources away from faucets after extended

period of non-use.

BASICS

BASICS

Read instruction manual before

installing, using or servicing

water heater.

Fire or Explosion Harzard

Hydrogen gas can be produced in a hot water system after
a period of non-use (generally two or more weeks).

Hydrogen gas is extremely flammable and can ignite.

To return hot water system to service, open a hot water
faucet in kitchen for several minutes before using electrical
appliances.

Do not smoke or have open flame near faucet while it is open.
Leave hot water faucet open until the sound of escaping
air stops.

After extended period of non-use,

purge gases from hot water system.

Residential Standard Gas Water Heater Service Handbook • 5

Residential Standard Gas Water Heater Service Handbook • 5

COMPLETED INSTALLATION ΈTYPICALΉ

Exhaust Vent to

Ouside of Building

Union

Gas Supply

BASICS

BASICS

See Labels and
Installation Instructions
and Use & Care Guide
for clearances.

Union

To Fixtures - Hot

Tempered Water

Untempered
Hot Water

To Fixtures

Cold

Water

Inlet

Water

Water

Shut-Off

Valve

Temperature-Pressure Relief Valve

with discharge piped to an

adequate drain. Do not cap or plug.

Supply- Cold*

*Massachusett: Install
a vacuum relief in cold
water line per section
19 MGL 142.

Expansion Tank

Pressurized to Equal

Supply Water Pressure*

(Relieve water pressure

on the expansion tank

before adjusting air

pressure.)

Hot
Water
Outlet

Mixing Valve

(Set to 120°F)

Follow the Mixing

Valve Manufacturer’s

Instructions

Union

Sediment Trap

3” Minimum.

Base Ring Filter:

Air is drawn in for combustion. Keep area clean

and free from flammables and flammable vapors.

Manual Gas

Shut-off Valve

Gas Control Valve/Thermostat

Recommended setting of 120°F.

Do not cap or plug.

6” Maximum Air Gap

NOTE: Local codes

may vary.

Drain

Metal Drain Pan piped to an adequate drain.
NOTE: Drain pan diameter must be at least
2 inches wider than the diameter of the
water heater.

The water heater must be installed according to all local and state codes or in the absence of local
and state codes, the “National Fuel Gas Code” ANSI Z223.1(NFPA 54)- current edition.

* NOTE: If on a well system, the expansion tank should be set to the maximum pressure of the pump tank.

6 • Residential Standard Gas Water Heater Service Handbook

6 • Residential Standard Gas Water Heater Service Handbook

Figure 1.

SYSTEM BASICS

Honeywell® Gas Control
Valve/Thermostat

Water heaters covered by this handbook
are equipped with Honeywell gas
control valve/thermostats.

• The Honeywell valve uses a
thermopile instead of a thermocouple
as did previous designs.

• Heat on the thermopile generates
750 to 900 millivolts (open circuit).

• When heated by the pilot and
connected to the Honeywell control,
the thermopile generates at least
350 millivolts (closed circuit). This
voltage opens the power head
in the control, allowing gas to
flow. It also powers the onboard
diagnostics (status light). See
Figure 2.

• The Honeywell valve uses a standard
push-button piezo igniter. See “Spark
Igniter” in Figure 2B.

• Status codes are printed on the face
of the control for easy reference
(Figure 2B.)

• The LED status light shows the
current status of the control as well
as possible error codes for easy
diagnosis. For more information on

error codes, see “Lighting the Pilot /
Diagnostic Flash Codes” on page 9.

WŝůŽƚŇĂŵĞŚĞĂƚƐƚŚĞƌŵŽƉŝůĞ
ĞŶĂďůŝŶŐŐĂƐĐŽŶƚƌŽůǀĂůǀĞ
ƚŚĞƌŵŽƐƚĂƚŽƉĞƌĂƟŽŶ

Pilot

Thermopile

Figure 2.

Gas Pressures

Ensure that the following pressures are
observed and maintained:

Table 1. GAS PRESSURES

GAS MAXIMUM

SUPPLY

PRESSURE

NAT 14 InWC 5.0 InWC

LP 14 InWC 10.0 InWC

Min. Supply Pressure: See Rating Plate.

MANIFOLD

GAS

PRESSURE

(± 0.4 InWC)

(± 0.5 InWC)

The gas control valve\thermostat also
includes a temperature limiting ECO
(Energy Cut Off) system. This system
will shut off the water heater if the
water temperature becomes excessive.
Should the water temperature get
too high, the main burner and pilot
will shut off automatically. Once the
pilot is relit, the status light will flash
a code (4 flashes), indicating an over­temperature condition. See “Lighting
the Pilot / Diagnostic Flash Codes” on
page 9 for more information.

NOTE: Honeywell is a registered trademark
of Honeywell International, Inc.

Temperature Seƫ ngs

The water temperature setting can be
adjusted from 55°F to 155°F. Simply
turn the gas control/temperature Knob
to the desired setting/temperature.
See Figure 3.

NOTE: The temperatures indicated are
approximates. The actual temperature
of the heated water may vary.

BASICS

Figure 2B

Temperature Control Knob

Temperature control ranges:

ͻϱϱΣ&ͲϭϱϱΣ&ǁŝƚŚsƐĞƫŶŐ
ͻϵϭΣ&ͲϭϱϱΣ&ǁŝƚŚŽƵƚsƐĞƫŶŐ

* Some models do not

ŝŶĐůƵĚĞĂs;ǀĂĐĂƟŽŶͿƐĞƫŶŐ

Residential Standard Gas Water Heater Service Handbook • 7

*

Scalding Risk

A water heater
can make water
hot enough to

cause severe burns
instantly, resulting in severe injury or
death. Higher temperatures increase

BASICS

the risk of scalding, but even at 120°F,
hot water can scald. See Table 2.
Thermostatic mixing valves at each
point of use reduce the risk of scalding.

HONEYWELL® GAS CONTROL VALVE/THERMOSTAT

GAS CONTROL/TEMPERATURE KNOB

VAC

IGNITER

TEMPERATURES SHOWN ARE APPROXIMATES AND MAY VARY.
SOME MODELS ARE CERTIFIED FOR 180°F. SEE RATING PLATE.

Figure 3.

Table 2.

Water
Temperature

120°F (49°C) More than 5 minutes

125°F (52°C) 1½ to 2 minutes

130°F (54°C) About 30 seconds

135°F (57°C) About 10 seconds

140°F (60°C) Less than 5 seconds

145°F (63°C) Less than 3 seconds

150°F (66°C) About 1½ seconds

155°F (68°C) About 1 second

IMPORTANT: Water temperature
in the tank can be higher than the
thermostat setting. Some of the
reasons are:

• Incoming water temperature is

higher than the set point (e.g.,
solar-heated water).

§140°F

§130°F

120°F
MARK

STATUS
LIGHT

§55°F

Time to Produce
a Serious Burn

§150°F

§155°F

• The water heater and/or pipes
are located in an area with high
ambient temperatures (e.g., an
attic). See also “Attic Installations”
on page 23.

• Certain usage patterns, such as
short hot water draws or no hot
water use for long periods of
time, can cause the tank water
temperature to rise higher than the
thermostat setting. Modern water
heaters are very well insulated
and retain heat so efficiently that,
under certain circumstances,
the tank water temperature can
increase over time, particularly
when hot water is not being used.
This “heating” effect can be caused
by the pilot flame itself.

CombusƟ on Chamber
with TCO Switch

Combustion air is drawn through the
base-ring filter and flame arrestor and
into the combustion chamber. (See
Figure 5.) Sufficient combustion air is
critical to the operation of the water
heater.

IMPORTANT: The flame arrestor
and filter should be inspected and
cleaned during each service call. See
page 18 for instructions.

Also, each water heater covered by
this handbook is equipped with a
resettable TCO switch (thermal switch),
designed to shut off the gas supply in
the event that the water heater has
been exposed to high combustion
chamber temperatures caused by one
of the following events:

• Flammable vapors (e.g., spilled

gasoline)

• Poor combustion caused by a

blocked vent

• Insufficient combustion air.

A resettable thermal switch is
illustra

ted in Figure 4. Its reset button

is located in the center of the switch,
directly between the terminals.

IMPORTANT: If the thermal switch has
been tripped, determine the cause
and correct it before returning the

water heater to service. Ensure that

there are no flammable vapors
present. However, a tripped thermal

switch is most likely caused by poor
combustion (e.g., blocked vent or dirty
filter/arrestor).

THERMAL SWITCH (TCO) LOCATION

THERMAL

SWITCH

(TCO)

Figure 4.

FLAME ARRESTOR

BASE-RING
FILTER

COMBUSTION CHAMBER

Figure 5.

8 • Residential Standard Gas Water Heater Service Handbook

LIGHTING THE PILOT / DIAGNOSTIC FLASH CODES

LighƟ ng the Pilot:

1. Read and follow the lighting
instructions on the water heater’s
label.

2. Turn the control knob to “Pilot.”
Press the knob in fully and hold it in.
(The knob will travel in about 1/4­inch if it is set to Pilot correctly.)

3. While holding the control knob in,
click the igniter button continuously
for up to 90 seconds or until the
Status Light begins to blink.

If the status light does not begin
to blink after 90 seconds, STOP.
Release the control knob. Wait
10 minutes before attempting to
relight the Pilot. Repeat these steps
2-3 times, if necessary.

The circuitry in this gas valve
requires that you wait 10 minutes
between lighting attempts.

If the Status Light blinks, release
the gas control/temperature knob
and turn it to the desired setting.
(“Hot” is approximately 120°F).

'ĂƐŽŶƚƌŽůdĞŵƉĞƌĂƚƵƌĞ<ŶŽď

/ŐŶŝƚĞƌƵƩŽŶ

Figure 6.

If the Status Light Does
Not Blink:

1. Wait 10 minutes before another
lighting attempt.

2. If the status light did not blink, repeat
the lighting procedure by following
the lighting instructions on the water
heater’s label. Remove the outer

door. The control knob must be set
to Pilot and held in continuously
while clicking the igniter button
(about once per second for up to
90 seconds). To observe the Pilot,
remove the outer door and look
through the view port (sight glass).
See Figure 7.

3. Continue clicking the Igniter button
(for up to 90 seconds) until pilot
lights.

4. Once the pilot is lit, continue to hold
the control knob in until the Status
Light begins to blink.

5. Release control Knob and set Knob to
desired temperature setting. (“Hot”
is approximately 120°F.)

6. Replace the outer door.

If the Pilot Does Not
Light:

1. Wait 10 minutes before another
lighting attempt. If the pilot does not
light, the Igniter may not be sparking
or the unit may not be getting gas (or
for a new installation, there may still
be air in the gas line). Each time you
click the igniter button, you should
be able to see the spark by looking
through the view port. See Figure 7.
(You may have to darken the room
lights to see the spark.) You do not
have to push the Control Knob in
to check the Igniter button. Simply
look through the sight glass while
clicking the Igniter button and look
for a spark. If you can’t see a spark
when the Igniter button is clicked,
check the wiring connections from
the Igniter button and make sure
that they are tight.

2. If you see the igniter spark, try
relighting the pilot by following the
instructions on the water heater’s
label. Ensure that the gas supply is
turned on. There may be air in the
gas line, and several lighting attempts

may be needed to completely fill the
line with gas and successfully light
the pilot.

'^KEdZK>V>sd,ZDK^TAT

'^KEdZK>
dDWZdhZ<EK

W/K/'E/dZhddKE

V/tWKZd

KhdZKKZ
EKd^,KtE

VAC

Figure 7.

d,ZDKW/>

t/ZKEEd/KE^

THERMAL

SWITCH

ΈdKΉ

If the Pilot Lights but the
Status Light Does Not
Blink:

1. If the pilot lights, continue to hold the
control knob in until the status light
blinks. If the pilot is lit and remains
lit for 90 seconds and the Status Light
still does not blink, the thermopile
connections may be loose, the
thermal switch may need to be reset,
or the thermopile may be defective.

2. Remove the outer door.

3. Press the reset button on the thermal
switch (TCO switch). See Figure 7.

4. If the switch clicks, it may have
tripped. Do not light the pilot if
flammable vapors are present.
Check flame arrestor for signs
of discoloration (which could be
caused by flammable vapors). If the
flame arrestor is discolored, do not
attempt to relight the Pilot. Have the
water heater inspected by a qualified
service technician.

5. Check the wiring connections
from the thermopile and thermal
switch (TCO) to the gas control
valve/thermostat. Ensure that
all wiring connections are tight.
See Figure 7.

6. Replace the outer door.

PILOT/FLASH CODES

Residential Standard Gas Water Heater Service Handbook • 9

7. Wait 10 minutes and try to light the
Pilot according to the instructions
on the water heater’s label.

8. While clicking the igniter button
continuously, the control knob must
be set to Pilot and held in until the
Status Light blinks. Once the status
light blinks, release the control knob
and set the knob to the desired
temperature setting. (“Hot” is
approximately 120°F.)

DiagnosƟ c Flash Codes

NOTE: In each case, the flash code will

occur, followed by a 3 second pause,
and then will repeat.

PILOT/FLASH CODES

0 Flashes (LED not lit)

Indication/Condition:

Control Off/Pilot Out.

Check/Repair:

1. Follow the lighting instructions on the

front of the water heater and attempt
to relight the pilot. Confirm that
the pilot is lit by looking through the
viewport (Figure 16, p. 17).

2. If pilot will light but does not

hold, check for a tripped thermal
switch. (Measure continuity by
placing a meter lead on each of
the two terminals. Continuity
means that it was not tripped.) If
thermal switch is tripped, check for
flammable vapors in the area and
ensure that the unit has adequate
combustion air and proper draft
before relighting. (You can reset
the thermal switch by pressing the
reset button in its center.) Also,
ensure that the filter and flame
arrestor are clean (p. 18).

3. If the pilot will light and does hold,

record any status codes and follow
the procedures relating to that code.

4. If pilot will not light at all, verify the

piezo igniter is producing a spark
and the unit is getting the correct
supply gas pressure. See “Testing

the Igniter System” (p. 19);
“Gas Pressure Checks” (p. 11).
Also, check the thermopile wiring
connections (Figure 16, p. 17).

Status Light On (solid)

Indication/Condition:

Pilot light was recently extinguished
and the thermopile is cooling down.

Check/Repair:

1. Turn the gas control valve/
thermostat knob to OFF.

2. Wait 10 minutes for the thermopile
to cool, then attempt to relight
the pilot by following the lighting
instructions on the water heater’s
label. NOTE: This gas control valve/
thermostat has built-in circuitry
that requires waiting 10 minutes
between lighting attempts.

Until the Thermopile reaches its
normal operating temperature,
the status light will not blink, even
if the pilot is lit. It may take up to
90 seconds of continuous pilot
operation before the thermopile
reaches normal operating
temperature and the Status Light
starts to blink.

1 Flash

Indication/Condition:

Normal Operation (bright/dim
heartbeat)

Check/Repair: No corrective action
necessary.

2 Flashes

Indication/Condition:

Thermopile voltage low.

Check/Repair:

1. Check all wiring connections for loose
or damaged wires. Correct if needed.

2. Check the millivolt output on the
thermopile. If output is less than 350
millivolts DC, replace the thermopile.

See also “Condensation” on page 15.

4 Flashes

Indication/Condition:

Temperature exceeded (ECO activated).

Check/Repair:

1. Turn gas control valve/thermostat
knob to OFF.

2. Turn the main gas supply OFF.

3. Replace the gas control valve/
thermostat.

5 Flashes

Indication/Condition: Sensor failure.

Check/Repair:

1. Turn gas control valve/thermostat
knob to OFF.

2. Turn the main gas supply OFF.

3. Replace the gas control valve/
thermostat.

7 Flashes

Indication/Condition:

Internal control failure.

Check/Repair:

1. Turn gas control valve/thermostat
knob to OFF.

2. Turn the main gas supply OFF.

3. Replace the gas control valve/
thermostat.

8 Flashes

Indication/Condition: Power off failure.

Check/Repair:

1. If the pilot flame is present when
the control knob is set to the OFF
position, replace the gas control
valve/thermostat.

2. If the pilot flame is not present when
the control knob is set to the OFF
position, wait 10 minutes for the
thermopile to cool, then relight the
unit. If this condition returns, replace
the gas control valve/thermostat.

10 • Residential Standard Gas Water Heater Service Handbook

SYSTEM CHECKS

Explosion Risk

WARNING! Before performing any

test, check the area around the water
heater for any source of a flammable
vapor (i.e gasoline, paint thinners,
etc.). If any sources are found, do not

proceed until they are removed.

DraŌ Test

WARNING! Burn Hazard. Do not
touch the vent. Doing so can cause
burns.

After successfully lighting the water
heater, allow the main burner to

operate for five minutes. Close all
windows and doors and turn on all
gas appliances and air-moving devices
(range hoods, bathroom exhaust fans,
ceiling fans, etc.) in the home. Also,
close any fi replace dampers.

After five minutes, pass a newly
exƟ nguished match about one inch (1”)
from the draŌ hood’s relief opening.
Smoke from the match should be steadily
drawn into the opening, indicaƟ ng proper
draŌ and a funcƟ oning vent system.

DRAFT HOOD

RELIEF

MATCH

OPENING

ConnecƟ ons Check

Some issues can be caused by faulty
connections. Refer to the following list
of connections when troubleshooting
the system:

• Igniter wire (Figure 9). See also
“Testing the Igniter System” on
page 19.

• Thermopile/thermal switch wires
at the gas control valve/thermostat
(Figure 9).

• Wire connections at the thermal
switch (TCO). A disconnected
thermal switch wire can cause the
pilot to become inoperable. See
Figure 4, page 8.

See also “Diagnostic Flash Codes” on
page 10.

From Thermopile (White)

From Thermal Switch (Red)

• Supply gas pressure checks are
measured before the gas control
valve/thermostat and as close
to the water heater as possible.

NOTE: The dynamic gas pressure
(burner on) should be measured
with all appliances operating that
use the common gas supply.

• Manifold (main burner) gas
pressure is measured at the
pressure tap on the bottom of
the gas control valve/thermostat.
See Figure 9 and Figure 11. Use a
3/16” Allen wrench to remove the
pressure tap plug, then attach the
gas gauge.

NOTE: Gas outlet pressures will be listed
on the gas control valve/thermostat’s
pressure label. See Figure 10. Also,
gas supply pressure requirements are
shown on the water heater labeling.

GAS PRESSURE LABEL (OUTLET PRESSURE)

GAS

PRESSURE

GAUGE

VAC

MANIFOLD GAS PRESSURE TEST

CONNECTED AT

PRESSURE TAP

Figure 10.

SYSTEM CHECKS

Figure 8.

If the main burner has been operaƟ ng
for fi ve minutes, but the match smoke
driŌ s around or is blown away from
the opening, turn the gas control knob
OFF. Do not operate the water heater
until proper adjustments or repairs are
made to the vent pipe system and/or air
supply (p. 21). Always check the filter
and flame arrestor first and clean them,
if necessary (p. 18).

Igniter Wire

Manifold Flex Tube Nut:

ͻWƌŽƉĂŶĞ>ĞŌͲŚĂŶĚƚŚƌĞĂĚƐ
ͻEĂƚƵƌĂůZŝŐŚƚͲŚĂŶĚƚŚƌĞĂĚƐ

Manifold

Pressure Tap

(1/8” NPT-RH)

Figure 9.

Gas Pressure Checks

Gas pressure checks are made with
flowing gas. Use a gas pressure gauge
capable of reading pressure in inches
of water column.

Residential Standard Gas Water Heater Service Handbook • 11

CONNECTED AT PRESSURE TAP

Figure 11.

Table 3.

Gas Pressures

IF . . .

...the supply gas
pressure is lower
than required...

. . . THEN

• increase the
supply gas
pressure regulator
setting

and/or

• increase supply
gas piping size.

2. Insert multimeter leads into the
connectors. The multimeter must
be set to read millivolts DC (on a
scale that can read 750 millivolts).
Reference Figure 12.

Thermopile Check
(Closed Circuit)

Follow the lighting instructions to light
the pilot. Once the pilot is lit, you can
check the output of the thermopile
with one of the following tests. A
reading above 350 mV DC indicates
that the thermopile is working
properly.

INSERT MULTIMETER LEADS INTO
THERMOPILE PLUGS AT CONTROL.
PILOT MUST BE LIT.

SYSTEM CHECKS

...the supply
gas pressure
is higher than
required...

...the manifold
gas pressure
is not within
+/- 10% of the
value shown
on the gas
pressure label...

NOTE: The gas
pressure label
lists the gas
valve outlet
pressure. This
is the same as
the manifold
pressure. See
Figure 10.

• add a gas pressure
regulator.

• reduce the setting
on the existing
regulator.

• ensure that there
is adequate supply
gas pressure

• ensure that the
main burner
orifice is the
correct size for
the model being
tested.

• if the above
tests have been
performed and
the results were
correct, replace
the gas control
valve (p. 20).

Thermopile Check
(Open Circuit)

The following test will check the DC
voltage generated by the thermopile
when the pilot light is lit.

1. Remove the connectors from the
gas control valve/thermostat (red
and white wires). Use needle-nose
pliers.

USE A MULTIMETER TO CHECK THE OUTPUT OF
THE THERMOPILE (MEASURED IN MILLIVOLTS).

SHOWN ABOVE - MULTIMETER PROBES ARE
INSERTED INTO THE THERMOPILE PLUGS. THESE
PLUGS WERE REMOVED FROM THE RECEPTACLE AT
THE BOTTOM, RIGHT-HAND CORNER OF THE GAS
CONTROL VALVE/ THERMOSTAT.

Figure 12.

3. Follow the lighting instructions to
light the pilot. Once the pilot is lit,
continue to hold the gas control
knob in until this test is complete.
You may need assistance from
another person to do this. The
voltage reading should rise
gradually as the thermopile heats
up. After a few minutes, you should
have a reading of at least 350 mV
DC. A reading above 350 mV DC
indicates that the thermopile is
working properly.

4. When you are finished, plug the
connectors back into the gas
control valve/thermostat. If the
connectors are separate (not a
double connector), ensure that the
red wire connector is to the left and
the white wire connector is to the
right. See Figure 2B, page 7. If
the status light does not blink once
every three seconds, replace the
gas control valve/thermostat.

MULTIMETER SET TO READ mV.

MINIMUM ACCEPTABLE
MEASUREMENT: 350 mV DC.

Figure 13.

INSERT ONE MULTIMETER LEAD INTO
THE NEGATIVE PLUG ON THE CONTROL
(WHITE WIRE).

TOUCH THE OTHER LEAD TO A

TERMINAL ON THE THERMAL
SWITCH (TCO).

MULTIMETER SET TO READ mV.

PILOT MUST BE LIT.

MINIMUM ACCEPTABLE
MEASUREMENT: 350 mV DC.

Figure 14.

12 • Residential Standard Gas Water Service Handbook

COMMON ISSUES

Fire and Explosion Hazard

WARNING! Do not

attempt to light the water
heater if flammable vapors or liquids
are present. Do not store or use
gasoline or other flammable vapors
and liquids in the vicinity of this or any
other gas appliance. Storage of or use
of gasoline or other flammable vapors
or liquids in the vicinity of this or any
other appliance can result in serious
injury or death.

No Hot Water

If water is not being heated, check the
following:

1. Look at the gas control valve/

thermostat. Is it flashing? If so,
solutions for restoring hot water are
listed below. See also “Diagnostic
Flash Codes” on page 10.

1 Flash
Normal Operation

(This code may occur after you
relight the pilot.)
Once the water heater has
completed a heating cycle, it should
provide an adequate amount of
hot water. If it does not, see “Not
Enough Hot Water.” If the pilot
lights for a while, then goes out, see
“0 Flashes (LED not lit)” on page 10.

2 Flashes
Thermopile voltage is low

Possible causes/solutions:

• Thermopile is getting weak.

• Check wiring and connections.

• If necessary, replace the
thermopile. See “Replacing
the Pilot/Thermopile
Assembly” on page 17.

4, 5, or 7 Flashes

If you observe one of these
flash codes, refer to “Diagnostic
Flash Codes” on page 10.

8 Flashes
Power Off Failure

Often, this error can be cleared
by turning the pilot off, letting
it cool down for ten minutes,
then relighting it according to
the lighting instructions. See
“8 Flashes” on page 10.

2. If the status light is not lit, see
“0 Flashes (LED not lit),” page 10.
That section will help you investigate
causes related to the thermal switch
(TCO), spark ignition, gas pressures,
and thermopile connections.

NOTE: The pilot must be lit for

the status light (LED) to flash.
Heat from the pilot causes the
thermopile to generate voltage.
Without this voltage, the gas control
valve/thermostat cannot operate.
Remember: it may take up to 90
seconds to heat the thermopile
enough to power the status light.

3. If you completed step 2 and
the pilot will not light, check for
air in the gas line. (This is fairly
common with recent work/new

installations.) If there is air in
the gas line, bleed the line as
necessary. Make sure to hold the
gas control knob in fully and hold it
in. In most cases, energy efficient
pilot orifices are so small that it
may be difficult to clear the air by
holding the knob in.

When you are finished, try to light

the pilot. (Follow the lighting
instructions on the water heater.)
Remember to hold the control
knob in for at least 90 seconds so
the pilot can heat up.

Did the pilot light? If it did, check

the following:

A. If the pilot did not light, replace

the pilot. (The entire pilot/
thermopile assembly must be

replaced). The most likely cause
is contamination in the pilot
tube.

A. If the pilot is lit and the status

light is flashing, refer to
“Diagnostic Flash Codes” on
page 10.

B. If the pilot is lit, but the status

light did not start flashing, check
the thermopile (p. 12). If its
output is 350 mV or less, it must
be replaced. If its output is
greater than 350 mV, replace the
gas control valve/thermostat.

Not Enough Hot Water

Check the following if the water is not
hot enough or if the hot water runs out
too quickly:

Possible causes

• Lower seasonal water temperatures

• Faulty shower control or faucet
valve

• Thermostat is set too low

• Increased hot water usage

• Water heater is too small to meet
demand

• Reversed plumbing connections

• Plumbing system leak

• Sediment buildup in the tank

Verify the water temperature at
the temperature/pressure relief
valve. Check the mixing valve/
shower control settings. Also
check for leaks, heavy usage, and
extremely cold incoming water.
In all cases, clean the filter and
flame arrestor (p. 18), then
conduct a draft test (p. 11).

A description of each cause and its
solution(s) is listed below.

Lower Seasonal Water Temperatures

In some areas, water coming into the
tank is much colder during winter

COMMON ISSUES

Residential Standard Gas Water Heater Service Handbook • 13

and early spring months. Even when
the water heater is working properly,
it may take longer to fully heat the
water. As a result, hot water may not
be available as quickly as it is during
warmer months.

Faulty Shower Control Valve/Faucet
Valve

Check the hot water at all faucets in
the home. Some may have built-in
thermostat or pressure-balance mixing
valves that may need adjustment or
replacement. If you get hot water from
some outlets but not others, adjust/
replace each fixture as necessary.

NOTE: A mixing valve issue is not a
water heater defect and is not covered
by the water heater warranty.

Thermostat Set Too Low

Scalding Risk
A water heater can
make water hot

enough to cause
severe burns instantly, resulting
in severe injury or death. Higher
temperatures increase the risk of
scalding, but even at 120°F, hot water
can scald. See Table 2 on page 8
before proceeding. Thermostatic
mixing valves at each point of

COMMON ISSUES

use reduce the risk of scalding.

If you’ve checked all of the faucets
and shower controls and the water
temperature is still too cool, the water
heater’s thermostat may be set too
low. See “Temperature Settings” on
page 7 for instructions on how

to adjust the thermostat. If there
still isn’t enough hot water, set the
thermostat to a higher setting and
install a thermostatic mixing valve at
each point of use.

An Increase in Hot Water Usage

If hot water is running out during
holidays, weekends, or family
gatherings, the demand for hot
water may be exceeding the water
heater’s capacity. Hot water usage
can be reduced by washing clothes in
cold water, installing flow restrictors
on shower heads, and taking other
conservation steps.

Undersized Water Heater

If water is frequently too cool, the
water heater may be too small. If
the water heater is old, the best
solution may be to replace it with a
larger model. If the water heater is
in good condition, you may set the
thermostat to a temperature above
120°F and install thermostatic mixing
valves at each point of use. Set each
thermostatic mixing valve’s delivery
temperature to 120°F to reduce the
risk of scalding. (See “Temperature
Settings” on page 7.)

This method can increase the effective
size of the water heater by about 30%.

Reversed Water Connec ons

If the hot and cold water connections
are reversed, it may appear as if the
water heater isn’t producing much
hot water. This problem is usually
identified at the time of installation.

Confirm that the home’s hot water
pipe is connected to the water heater’s
hot water outlet, not the cold water
inlet. If the connections are reversed,
switch them to the correct position.

NOTE: The water heater’s hot water
outlet will be marked with an “H” or
“HOT,” or will be color coded red.

Leak in the Plumbing System

A leak in the home’s plumbing system
can overload the water heater’s ability
to heat water. In that case, the water
heater can be working, but there will
be little or no hot water. Check the
plumbing system for leaks and repair
as necessary.

Sediment Buildup in the Tank

If the water heater is several years old
and/or is installed in an area known for
hard water, there may be a buildup of
sediment at the bottom of the tank.
Sediment buildup may reduce the
efficiency of the water heater and may
reduce the amount of available hot
water.

Drain and flush the tank (page 20).
You may also treat the tank with a
lime/scale removal solution that is
approved for potable water heaters.

14 • Residential Standard Gas Water Service Handbook

Tank Leak

CondensaƟ on

If you see small puddles of water in
the drain pan or hear sizzling sounds
as water drips on the burner, the
water heater may be producing
condensation. Condensation may drip
onto the burner or other hot surfaces
to produce a sizzling sound. On some
models, this may actually cause the
pilot to go out.

Condensation usually occurs when the
water heater tank is full of cold water.
Condensation will most likely occur:

• During holidays, weekends, or
family gatherings when there is an
increase in your home’s hot water
usage.

• During the winter and early spring
months when incoming water
temperatures are at their lowest.

• If the water heater is a new
installation.

• If a large amount of hot water is
used in a short period of time.

• If the water heater is too small for
the home’s hot water demands.

In most cases, condensation
should disappear once the water
heater reaches normal operating
temperature, or when the home’s hot
water demands return to normal.

If the water heater is too small for the
home’s typical hot water demands,
the water heater may produce

condensation regularly. In that case, a
larger water heater is recommended.

NOTE: Condensation may cause a “2
Flashes” error code, indicating low
thermopile voltage. This condition
may clear up as the tank begins to
warm. See “2 Flashes” on page 10

Leaking Plumbing ConnecƟ ons

If there’s water on the floor around
the bottom of the water heater, check
the plumbing connections on top of
the tank. Use a dry paper towel to
wipe around the hot and cold pipe
connections on top of the water
heater. If the paper towel is wet after
wiping a connection, repair the leak(s).

Drips from the T&P Relief Valve
Discharge Pipe

A small amount of water dripping from
the temperature and pressure (T&P)
relief valve usually means the home’s
water pressure is too high or you
need a properly sized and pressurized
thermal expansion tank. A large
amount of hot water coming from the
T&P discharge pipe may be due to the
tank overheating.

WARNING! Do not cap or plug the

T&P relief valve or discharge pipe,
and do not operate the water heater
without a functioning T&P relief Valve.
This could cause an explosion.

Refer to Figure 1 on page 6 while
reviewing this section.

• Water pressure too high. High water

pressure can cause the T&P relief
valve to drip. Install a pressure
reducing valve (PRV) on the main
cold water supply line. Adjust the
PRV to between 50 and 60 psi.

• Thermal Expansion Tank. Install

a Thermal Expansion Tank. If a
Thermal Expansion Tank is already
installed and the T&P Relief Valve
discharge pipe drips, the Thermal
Expansion Tank may be pressurized
to the wrong pressure or the internal
bladder may be defective. Refer to
the instructions that came with the
Thermal Expansion Tank for more
information.

• Debris. In rare cases, debris can

stick inside the T&P relief valve
preventing the valve from seating
fully. In that case, the T&P relief
valve discharge pipe will drip. You
may be able to clear debris from
the T&P Relief Valve by manually
operating the valve, allowing small
quantities of water to flush out the
debris. See the label on the T&P
relief valve for instructions.

If the water pressure is between 50
and 60 psi, a thermal expansion tank is
installed and properly pressurized, and
the valve has been cleared of any debris,
and it still drips, the valve may be broken.
Install a new T&P relief valve.

COMMON ISSUES

Residential Standard Gas Water Heater Service Handbook • 15

Temperature Too High

Scalding Risk

A water heater can
make water hot

enough to cause
severe burns instantly, resulting
in severe injury or death. Higher
temperatures increase the risk of
scalding, but even at 120°F, hot water
can scald. See Table 2 on page 8
before proceeding. Thermostatic
mixing valves at each point of
use reduce the risk of scalding.

If the water temperature is too hot:

• Install or adjust the thermostatic

mixing valves for each point-of-use
(see manufacturer’s instructions), or

• Adjust the temperature setting on

the water heater. See “Temperature
Settings” on page 7.

Low Water Pressure

Check both the cold and hot water at a
sink to determine if the lower pressure
is only on the hot water side. If the low
pressure is on the hot water side only,
the primary causes of this are:

• Melted heat traps or dip tube.
Soldering copper pipes while they are
connected to the water heater can
melt the heat traps inside the hot and
cold water connections or the dip tube
(cold water side). Melted heat traps or
a melted dip tube can restrict the flow
of hot water. If that’s the case, replace
the heat traps or dip tube.

• Partially closed supply valve. Open
the water heater’s supply valve fully.

Water Odor

Harmless bacteria normally present
in tap water can multiply in water
heaters and give off a “rotten egg”
smell. Although eliminating the
bacteria that causes “smelly water”
with a Chlorination system is the only
sure treatment, in some cases, the
standard anode rod that came with the
water heater can be replaced with a
special zinc anode rod which may help
reduce or eliminate the odor. Contact
Technical Assistance for availability.

NOTE: To protect the tank, an anode rod
must be installed in the water heater at
all times or the warranty is void.

In cases where the “rotten egg” smell
is pronounced, you can raise the tank
temperature to 140°F in order to
reduce bacteria growth in the tank.

WARNING! Higher temperatures

increase the risk of scalding. If
you set the temperature setting
higher than 120°F, thermostatic
mixing valves at each point-of-use

are particularly important. See
“Temperature Settings” on page 7.

COMMON ISSUES

16 • Residential Standard Gas Water Service Handbook

SERVICE PROCEDURES

Removing the Manifold/
Burner Assembly

1. Turn the gas control/temperature
knob to the “OFF” position (Figure
6 on page 9).

2. Before performing any
maintenance, it is important to
turn off the gas supply to the water
heater at the manual gas shut­off valve (Figure 1, p. 6). This
valve is typically located beside the
water heater. Note the position of
the shut-off valve in the open/on
position, then proceed to turn it
off.

3. With the unit shut-off, allow
sufficient time for the water heater
to cool before performing any
maintenance.

'^KEdZK>
dDWZdhZ<EK

VAC

IGNITER

hddKE

IGNITER

>

WIRE

IGNITER
WIRE

W/>Kd
TUBE

Figure 15.

4. Remove the outer door.

5. Disconnect the following from the
gas control valve/thermostat: pilot
tube (7/16” wrench), igniter wire
(from the igniter lead wire), and
manifold tube (3/4” wrench). See
Figure 15.

6. Disconnect the white and red
wires from the gas control valve/
thermostat (Figure 15). Use
needle nose pliers to grip the
connector(s). IMPORTANT: Grip
the connector carefully to prevent
damage. Do not grip or pull the
wires themselves.

7. Grasp the manifold tube and push
down slightly to free the manifold
tube and pilot tube.

WHITE

WIRE

ΈZ/',d

^/Ή

RED WIRE

Έ>&d^/Ή

DE/&K>dh

8. Remove the screws (1/4” nut
driver) securing the manifold/
burner assembly to the combustion
chamber. (Figure 16.)

9. Carefully remove the manifold/
burner assembly from the
combustion chamber. BE SURE NOT
TO DAMAGE ANY INTERNAL PARTS.

'^KEdZK>V>sd,ZDK^TAT

'^KEdZK>
dDWZdhZ<EK

W/K/'E/dZhddKE

V/tWKZd

KhdZKKZ
EKd^,KtE

DE/&K>^Zt^ΈϮΉ

VAC

d,ZDKW/>

t/ZKEEd/KE^

THERMAL

SWITCH

ΈdKΉ

Figure 16.

Removing the Burner
from the Manifold/
Burner Assembly

Natural Gas (Low Nox) & L.P. Gas
Burner

1. Take off the burner by removing the
two (2) screws located underneath
the burner (Figure 17.).

2. Check the burner to see if it is dirty
or clogged. The burner may be
cleaned with soap and hot water.
IMPORTANT: DO NOT remove the
orifice.

BURNER SCOOP

(SOME MODELS)

SCREWS (2)

PILOT ASSEMBLY
(BOTTOM VIEW)

MANIFOLD

TUBE

BURNER

(BOTTOM VIEW)

Figure 17.

Replacing the Pilot/
Thermopile Assembly

A. Removing the Old Pilot/

Thermopile Assembly from
the Manifold Assembly

1. Remove the manifold door
assembly as described in
“Removing the Manifold/Burner
Assembly” section.

2. Remove the burner to access
the pilot/thermopile assembly.
Remove and keep the screws
securing the burner to the manifold
(Figure 17.) IMPORTANT: DO NOT
remove the orifice.

3. Remove the screw securing the
pilot/thermopile assembly to the
pilot bracket and keep for reuse
later (Figure 18.)

4. Lift the retainer clip straight up
from the back of the manifold
component block (using a flat­blade screwdriver), then remove
the manifold component block
from the manifold door. See Figure

18. IMPORTANT: Be careful not
to bend or alter the position of
the pilot tube. It will be used as a
bending template for the new pilot
assembly. Note the placement/
order of the wires in the manifold
component block.

5. Lift the pilot/thermopile assembly
(including the igniter wire) from
the manifold assembly.

PILOT / THERMOPILE
ASSEMBLY SCREW

BURNER AND OTHER
FITTINGS NOT SHOW
FOR CLARITY.

RED WIRES TO

d,ZD>^t/d,ΈϮΉ

IGNITER
WIRE

MANIFOLD
COMPONENT
BLOCK

CONNECTORS

RETAINER
CLIP

PILOT TUBE
MANIFOLD DOOR

Figure 18.

SERVICE PROCEDURES

Residential Standard Gas Water Heater Service Handbook • 17

B. Installing the New Pilot/

Thermopile Assembly

1. Read this step carefully before
proceeding. Using the old pilot/
pilot tube assembly as a guide,
bend the new pilot tube to match
the old one. Make only the bends
closest to the pilot before going to
the next step.

2. Route the new pilot tube and
wires through the opening in the
manifold door. See Figure 18 on
page 17.

PILOT/THERMOPILE ASSEMBLY

IGNITER
CONNECTOR

PILOT

PILOT/THERMOPILE

KEEdKZΈ^Ή
ΈKEEdd

GAS CONTROL VALVE/

d,ZDK^ddΉ

ASSEMBLY

FOR CLARITY, PILOT
TUBE NOT SHOWN .

Figure 19.

ORIFICE

ΈKDWKEEd^Ή

THERMOPILE

THESE TWO PARTS MAY BE

PILOT

PILOT BRACKET

EXPLODED VIEW OF PILOT/THERMOPILE ASSEMBLY.
FOR INFORMATIONAL PURPOSES ONLY. THE PILOT/THERMOPILE
ASSEMBLY SHOULD BE INSTALLED/SERVICED AS A SINGLE UNIT.
DO NOT DISASSEMBLE.

COMBINED ON SOME MODELS.

PILOT ASSEMBLY FOR CAST
BURNER NOT SHOWN.

Figure 20.

SERVICE PROCEDURES

3. Using the pilot screw removed
earlier, attach the new pilot/
thermopile assembly. Reattach
the burner to the manifold using
the screws removed earlier. NOTE:
If your burner includes a burner
scoop, make sure that it is oriented
to the pilot side of the manifold
tube. See Figure 17 on page 17.

THERMOPILE

THERMAL
SWITCH
CONNECTORS

ΈZt/Z^Ή

PILOT TUBE

4. Reinstall the manifold component
block in the manifold door. Ensure
that the pilot tube and wires are
positioned as shown in Figure 21.

5. Carefully bend the new pilot tube
to match the bend of the manifold
tube. NOTE: When bending, DO
NOT crimp or crease the pilot tube.

6. Before you proceed to the next
step, install the new brass ferrule
nut in the gas control valve/
thermostat’s pilot tube opening,
HAND TIGHT ONLY.

7. Install the manifold/burner
assembly.

ZΈнΉd,ZD>^t/d,t/Z

CONNECTS TO THE GAS CONTROL
VALVE\THERMOSTAT.

t,/dΈͳΉd,ZDKW/>

WIRE CONNECTS TO THE GAS

CONTROL VALVE\

THERMOSTAT.

RED THERMAL SWITCH WIRE

MANIFOLD

KDWKEEd

BLOCK

/'E/dZt/ZW^^^

THROUGH CENTER OF

DE/&K>KDWKEEd
>K<Έ^D>>^d,K>Ή

W/>KddhW^^^d,ZKh',KddKD,K>
K&DE/&K>KDWKEEd>K<Έ>Z'^d,K>Ή

CONNECTIONS AT
MANIFOLD DOOR

d,ZDKW/>t/Z^W^^
d,ZKh',dKW,K>K&
DE/&K>KDWKEEd

BLOCK

Figure 21.

External InspecƟ on and
Cleaning of the Base­Ring Filter

1. At least annually, check the base­ring filter for any dust or debris that
may have accumulated on the filter
screen. See Figure 22. NOTE: If the
water heater is located in an area
that is subjected to lint and dirt,
it may be necessary to check the
base-ring filter more frequently.

2. Follow the Lighting Instructions to
turn off the water heater and allow
it to cool for 10 minutes before
attempting to clean the base-ring
filter.

3. Use a vacuum cleaner with a hose
attachment to remove any dust or
debris that may have accumulated
on the filter. NOTE: If you are
unable to inspect or clean the base­ring filter, follow the “Cleaning the
Combustion Chamber and Flame
Arrestor” instructions.

4. After the base-ring filter has
been cleaned, follow the Lighting
Instructions to return the water
heater to service.

COMBUSTION CHAMBER

DOOR GASKET

BASE-RING
FILTER

FLAME ARRESTOR

Figure 22.

Cleaning the
CombusƟ on Chamber
and Flame Arrestor

1. Follow procedure outlined in
“Removing the Manifold/Burner
Assembly.”

2. Use a vacuum cleaner/shop vac
to remove all loose debris in
the combustion chamber. See
Figure 22. Use compressed air to
clear any dust or debris that may
have accumulated in the flame­arrestor. (To clean the flame
arrestor, you may use a soft plastic
brush under water heater. Vacuum
lint from brush. Repeat until brush
is clean.)

18 • Residential Standard Gas Water Heater Service Handbook

3. Reassemble following the
procedure under “Replacing the
Manifold/Burner Assembly.”

Replacing the Manifold/
Burner Assembly

Explosion Risk

WARNING!

• Tighten both manifold door screws
securely.

• Remove any fiberglass between
gasket and combustion chamber.

• Replace viewport if glass is missing
or damaged.

• Replace manifold component block
if it is missing or has been removed.

• Replace door gasket if it is
damaged.

• Failure to follow these instructions
can result in death, explosion, or
fire.

1. Check the door gasket for damage
or imbedded debris prior to
installation. See Figure 22.

2. Inspect the viewport for
damage and replace as required
(Figure 16, page 17).

3. Insert the new manifold/
burner assembly into the burner
compartment, making sure that
the tab of the manifold tube
engages the slot of the bracket
inside the combustion chamber.
See Figure 23.

CLOSE-UP INSIDE VIEW OF
THE COMBUSTION CHAMBER.

SLOT

TIP

MANIFOLD TUBE

Figure 23.

BRACKET

4. Inspect the door gasket and make
sure there is no fiberglass insulation
between the gasket and the
combustion chamber. (Figure 22.)

5. Tighten the two screws that secure
the manifold/burner assembly to
the combustion chamber. (Use a
1/4” nut driver.) There should be no
space between the gasket part of
the manifold door and combustion
chamber

IMPORTANT: Do not operate the

water heater if the door gasket
does not create a seal between the
manifold door and the combustion
chamber.

6. Reconnect the manifold tube (3/4”
wrench) and pilot tube (7/16” wrench)
to the gas control valve/thermostat.
See Figure 15 on page 17. Do not
cross-thread or apply any thread
sealant to the fittings.

IMPORTANT: If you were supplied
with a new ferrule nut in a parts kit,
follow these steps to connect the
pilot tube:

A.) Install the ferrule nut into the gas

valve at the pilot tube location,
hand tight only.

B.) Insert the pilot tube into the

ferrule nut until the tube
bottoms out, then tighten the
nut with a 7/16” wrench until
the crimp connection seals to
the pilot tube.

C.) Continue to tighten until the nut

is tight in the gas valve.

7. Connect the white and red wires to
the gas control valve/thermostat
as shown in Figure 15, page 17.
Also, ensure that the red thermal
switch wires are connected to the
thermal switch (TCO switch) on the
manifold door. See Figure 21 on
page 18.

8. Reconnect the igniter wire. (Figure
15, page 17).

9. Turn on the gas supply to the water
heater at the manual gas shut-off
valve. (Figure 1, page 6).

10. Follow the lighting instructions
on the front of the water heater.
With the main burner lit, check
for leaks at the manifold and
pilot connections by brushing on
an approved noncorrosive leak
detection solution. If such a solution
is not available, use a mixture of
hand dish washing soap and water
(one part soap to 15 parts water)
or childrens’ soap bubble solution.
Bubbles forming indicate a leak.
Correct any leak found.

11. Verify proper operation, then
replace the outer door.

TesƟ ng the Igniter
System

The piezoelectric igniter system consists
of an igniter button, an electrode, and
wire. The pilot is ignited by an electric
spark generated when the igniter
button is pressed. See Figure 24.

THERMOPILE

PILOT

PILOT/
THERMOPILE

VAC

ELECTRODE

WIRE TO ELECTRODE

IGNITER BUTTON

Figure 24.

To test the igniter system, follow these
steps:

1. Turn off the gas to the water heater
at the manual gas shut-off valve.
(See Figure 1, page 6.)

2. Watch the electrode tip while
activating the igniter. (If the room
is dim enough, try looking through
the view port [Figure 16].)

A. A visible spark should jump from

the electrode. To avoid shock, do
not touch the burner or any metal

BRACKET

SERVICE PROCEDURES

Residential Standard Gas Water Heater Service Handbook • 19

part on the pilot or pilot assembly.
If no spark is visible, check the
wire connections and make sure
that the electrode is not broken.
See also “Connections Check” (p.

11).

B. Replace the igniter if defective

(i.e., gas control valve/
thermostat and/or pilot/
thermopile assembly). Dirt and
rust on the pilot or electrode tip
can prevent the igniter spark.
Wipe clean with a damp cloth
and dry completely. Rust can
be removed from the electrode
tip and metal surfaces by lightly
sanding with an emery cloth or
fine grit sandpaper.

Removing and Replacing
the Gas Control Valve/
Thermostat

IMPORTANT: This water heater has a

resettable thermal switch installed. Do
not attempt to disable or modify this
feature in any way. Use only factory
authorized replacement parts.

Removing the Gas Control
Valve/Thermostat:

1. Turn the gas control/temperature
knob to the “OFF” position.
(Figure 6, page 9.)

2. Turn off the gas at the manual shut­off valve on the gas supply pipe.
(Figure 1, page 6.)

3. Drain the water heater. Refer to
the “Draining and Flushing” section

SERVICE PROCEDURES

and follow the procedure.

4. Disconnect the igniter wire from
the igniter lead wire. Use needle
nose pliers to disconnect the
red (+) and white (-) thermopile
wires. Disconnect the pilot tube
(7/16” wrench) and manifold
tube (3/4” wrench) at the gas
control valve/thermostat. See
Figure 15 on page 17.

5. Disconnect the ground joint
union in the gas piping. See

Figure 1, page 6. Disconnect
the remaining pipe from the gas
control valve/thermostat.

6. To remove the gas control valve/
thermostat, thread a 4” section of
gas pipe into the inlet and use it to
turn the gas control valve/thermostat
(counterclockwise.) Do not use a
pipe wrench or equivalent to grip
body. Damage may result, causing
leaks. Do not insert any sharp objects
into the inlet or outlet connections.
Damage to the gas control valve/
thermostat may result.

Replacing the Gas Control Valve/
Thermostat:

To replace the gas control valve/
thermostat, reassemble in reverse
order. When replacing the gas control
valve/thermostat, thread a 4” section
of gas pipe into the inlet and use it to
turn the gas control valve/thermostat
(clockwise). DO NOT OVER TIGHTEN;
damage may result.

• Be sure to use approved Teflon®
tape or pipe joint compound on the
gas piping connections and fitting
on the back of the gas control valve
that screws into the tank.

• Be sure to remove the pilot ferrule
nut from the new gas control valve/
thermostat.

• Turn the main gas supply on and
check the gas supply connections
for leaks. Correct any leak found.
Next, light the pilot and main
burner, then check the manifold
tube and pilot tube connections
for leaks. Correct any leak found.
Use an approved noncorrosive
leak detection solution. If such
a solution is not available, use
a mixture of hand dish washing
soap and water (one part soap to
15 parts water) or childrens’ soap
bubble solution. Bubbles forming
indicate a leak.

• Be sure tank is completely filled
with water before lighting and
activating the water heater. Follow

the “Lighting Instructions” on the
front of the water heater.

TEFLON® is a registered trademark of
E.I. Du Pont De Nemours and Company

Draining and Flushing

WARNING! Hot Water Discharge

Hazard:

• Keep clear of temperature/
pressure relief valve discharge.

• Temperature limiting valves are
available.

• Read instruction manual for
information on a safe temperature
setting.

It is recommended that the tank be
drained and flushed every 6 months
to remove sediment which may build
up during operation. The water heater
should be drained if being shut down
during freezing temperatures. To drain
the tank, perform the following steps:

1. Turn off the gas to the water heater
at the manual gas shut-off valve.

2. Open a nearby hot water faucet
until the water is no longer hot.

3. Close the cold water inlet valve.

4. Connect a hose to the drain valve
and terminate it to an adequate
drain or external to the building.

5. Open the water heater drain valve
and allow all of the water to drain
from the tank. Flush the tank with
water as needed to remove sediment.

6. Close the drain valve, refill the tank,
and restart the water heater as
directed in the lighting instructions.
(The lighting instructions are
posted on the front of the water

heater.) Ensure that the water

heater is full of water before you
light the pilot.

If the water heater is going to be
shut down for an extended period,
the drain valve should be left

open. IMPORTANT: Condensation
may occur when refilling the tank and
should not be confused with a tank
leak.

20 • Residential Standard Gas Water Heater Service Handbook

SUPPLEMENTS

EVALUATING
COMBUSTION AND
VENTILATION AIR
SUPPLY

WARNING! Gas water heaters
require an adequate source of clean air
for combustion and ventilation.
Without sufficient air, a water heater
will have frequent pilot outages and
may emit excessive and abnormal
amounts of carbon monoxide.

Before beginning:

Calculate total BTU/HR rating of all
appliances

To calculate the combusƟ on air and
venƟ laƟ on required, add up the total
BTU/HR raƟ ngs of all gas burning
appliances (e.g., water heaters, furnaces,
clothes dryers) in the same area.

A water heater’s BTU/HR rating is on its
data plate, located next to the gas control
valve/thermostat. The BTU/HR ratings
should be on the other appliances’ data
plates. If you have trouble determining
the BTU/HR ratings, contact the
manufacturer. NOTICE: If you are
replacing an old water heater with one
that has a higher BTU/HR rating, the
amount of ventilation required may be
greater.

Example:

Gas Burning Appliance BTU/HR Rating

Gas Water Heater 40,000

Furnace 75,000

Dryer 20,000

Total 135,000

Household Appliances:

Gas Burning Appliance BTU/HR Rating

Gas Water Heater

To ta l

Table 2 provides examples of minimum
square footage (area) required for
various BTU/HR totals. Areas used for
storage or which contain large objects
containing less air than is assumed for
the room sizes in Table 4. See Option A
for more specific calculations.

Table 4.

BTU/HR Minimum

Square
Feet with
8’ Ceiling

30,000 188 9 x 21

45,000 281 14 x 20

60,000 375 15 x 25

75,000 469 15 x 31

90,000 563 20 x 28

105,000 657 20 x 33

120,000 750 25 x 30

135,000 844 28 x 30

Typical

Room with

8’ Ceiling

Option A: Installation without
outside ventilation (not
recommended)

Ventilation with outside air is
recommended for all installations. Even
if the water heater is installed in a large,
open room inside the house, outdoor
air is usually needed because modern
homes are very tightly sealed and
often do not supply enough air to the
water heater. However, when installed
in a large indoor space, it may be
possible to provide enough air without
outside ventilation. If you are unsure
if the installation location has enough

ventilation, contact your local gas utility
company or code officials for a safety
inspection.

The following instructions will help
determine if it may be possible to install
without outside ventilation. Even if
this may be possible, you will need to
conduct the vent draft test on page 11
when installation is finished. If there is
not enough ventilation, you will need to
ventilate with outside air.

Check for Chemicals:

Installations where corrosive chemicals
may be present require outside air.
Air for combustion and ventilation
must be clean and free of corrosive or
acid-forming chemicals such as sulfur,
fluorine, and chlorine. Ventilation with
outside air will reduce these chemicals,
but it may not completely eliminate
them. Failure due to corrosive chemicals
is not covered by the warranty. Examples
of locations that require outside air due
to chemicals include:

• Beauty salons

• Photo processing labs

• Indoor pools

• Laundry, hobby, or craft rooms

• Chemical storage areas

Products such as aerosol sprays,
detergents, bleaches, cleaning solvents,
gasoline, air fresheners, paint and
varnish removers, and refrigerants
should not be stored or used near the
water heater.

A1: Calculate the air volume of
the room

Air requirements depend on the size of
the room.

Floor Area (Square feet) X Ceiling Height
(feet) = Room Volume (cubic feet)

If there are large objects in the room
(e.g., refrigerator, furnace, car), subtract
their volume from the volume of the

SUPPLEMENTS

Residential Standard Gas Water Heater Service Handbook • 21

room to get a better estimate of the air
available.

Room Volume – Object Volume = Air
Volume

A2: Calculate required air volume

A water heater installed in an unconfined
attic or garage requires that the space
be at least 50 cubic feet per 1,000 BTU/
HR of the total input for all gas burning
appliances in the same area.

[Total BTU/HR/1000] x 50 = Cubic feet
of air required.

Example:

(135,000 / 1000) x 50 = 6,750

If the air volume of the room is less
than the required air volume, you must
provide two permanent outside air
openings that draw in sufficient air. Use
Option B.

If the air volume of the room is greater
than the required air volume, it may
be possible to install the water heater
without outside ventilation.

A3: Check that combustion
ventilation is adequate

Because modern homes are often
well-sealed to prevent drafts, even a
large room may not provide enough
combustion air without ventilation.
To confirm that your installation has
enough combustion air, conduct the
vent draft test on page 11 when
installation is finished.

Option B: Install with outside
ventilation

Ventilation with outside air is
recommended, and, for most
installations, is needed. There may be
existing ventilation that is adequate, or
you may need to add more ventilation.

Supplying outside air to typically

SUPPLEMENTS

requires two openings. One opening

must be within 12 inches from the floor
and the second opening must be within
12 inches from the ceiling. Although a
single opening is not preferred, you may
use a single opening to outside air if the
minimum free area is sized according
to Table 5. Two openings must be used
when ventilating with air from another
room.

The outside air can be taken from a crawl
space or attic open to the outdoors and
adequately ventilated. You may use
vertical or horizontal ducts.

B2: Determine type of
ventilation

There are several types of ventilation
that can be used :

1. Direct to outdoors

2. Vertical ducts

3. Horizontal ducts

4. Single opening (not recommended;
must be at least 100 square inches.
Not appropriate for confined
spaces smaller than 50 cubic feet
per 1,000 BTU/HR as calculated in
section A or when getting air from
another room.)

5. From a larger room inside the
house (not recommended – refer
to section A above to determine
if the combined volume of
the rooms may be adequate).

B3: Determine minimum free
area required for each vent
opening

The size of the vent openings depends
on the total BTU/HR rating of all
appliances in the space (use your
calculation from “Before beginning”)
and the type of vent used. Table 5
provides the minimum free area for
each vent opening depending on the
type of ventilation.

B4: Calculate minimum size of
vent openings and ducts

The vent cross-sectional area needed
to provide the free area depends on the
covering on the vent openings. Typical
vents use louvers or grilles to protect
the opening. The louver or grill itself
blocks some of the free area, so the
opening may need to be larger to meet
the minimum free area requirements.

Use the following formula to calculate
the required cross-sectional area:

Cross-sectional area = minimum free
area required ÷ percent free area of
covering (in decimals – e.g., 60% = .6)

For example, an installation area that
requires openings with 100 square
inches of free area would need 134
square inch openings if using metal
louvers rated at 75% free area (100 sq.
in. ÷ .75 = 134 sq. in.).

If you do not know the % free area for a
louver or grill, use the following values:

• For wood louvers or grilles: 20%

• For metal louvers or grilles: 60%

Follow these rules to ensure that vents
and ducts provide adequate air flow:

• Each vent opening must be no
smaller than 100 square inches .

• Ducts must have the same cross­sectional area as free area of the
opening.

• Rectangular ducts must have a
minimum dimension of no less
than three inches .

• All screens must have mesh ¼” or
larger.

• Moveable louvers must be locked
open or interconnected with the
equipment so that they open
automatically during operation.

• Keep louvers and grills clean and
free of debris or other obstructions.

22 • Residential Standard Gas Water Heater Service Handbook

Table 5.

Minimum Free Area of Permanent
Openings for VenƟ laƟ on and
CombusƟ on Air Supply – All Air from
Outdoors Only.

Based on the total BTU/HR input
raƟ ng for all gas burning appliances
within a confi ned space.

Opening Source Minimum Free Area

Per Opening (sq. in.)

*Direct to outdoors 1 sq. in. per

4,000 BTU/HR
(see Figure 25)

Vertical ducts 1 sq. in. per

4,000 BTU/HR
(see Figure 26)

Horizontal ducts 1 sq. in. per

2,000 BTU/HR
(see Figure 27)

Single Opening 1 sq. in. per

3,000 BTU/HR
(see Figure 28)

*These openings connect directly
with the outdoors through a
ventilated attic, a ventilated crawl
space, or through an outside wall.

B5: Check that air source is clean
and free of chemicals

CombusƟ on Air Supply OpƟ ons

Direct to outdoors openings

Figure 25.

Vertical duct openings

Figure 26.

ATTIC INSTALLATIONS

WARNING!

• In all cases, a water heater must be
installed according to its installation
manual.

• Consult the local codes of your
area for specific ventilation and
combustion air requirements. In the
absence of local codes, follow the
National Fuel Gas Code (ANSI Z223.1­current edition).

• Failure to follow these warnings
can lead to death, serious injury, or
property damage.

Overview

Attic installations are common in
some parts of the country. In most
cases, such installations are trouble
free. However, problems may arise
from poor ventilation, high ambient
temperatures, water leaks, and other
potential hazards. Such issues include
pilot outage, water damage to the
living spaces below, and elevated
water temperatures. Even so, these
problems can be addressed. Some of
the potential solutions are listed below.

1

Air for combustion and ventilation
must be clean and free of corrosive or
flammable chemicals. A failure due to
corrosive chemicals in the air is not
covered by the warranty. Combustion air
must be free of acid-forming chemicals
such as sulfur, fluorine, and chlorine. Be
sure that air at the vent inlets is free of
such chemicals.

B6: Check that combustion
ventilation is adequate

To confirm that your installation has
enough combustion air, conduct the
vent draft test on page 11 when
installation is finished.

Horizontal duct openings

Figure 27.

Single opening

Figure 28.

Pilot Outage

Pilot outage is more common in attic
spaces and hot environments than
in other installations. The following
factors can contribute to pilot outage,
either individually or in combination:

• Elevated air temperature

• Insufficient makeup air (air needed
for the proper ventilation of
combustion gases)

• Blocked air screen or flame arrestor

• Improper venting of the water heater

• Decompression

• Wind

1 Originally published as “Issues
Related to Gas Water Heaters Installed in Attics
(Atmospheric Vent)”
(324841-000).

SUPPLEMENTS

Residential Standard Gas Water Heater Service Handbook • 23

Elevated Air Temperature:

In some areas, attics can reach in excess
of 160°F. Such high temperatures can
cause atmospherically-vented water
heaters to stall and shut down.

Why? The flame arrestors, filters,
and sealed combustion chambers
that make modern water heaters
flammable vapor ignition resistant
also make them more sensitive to
high ambient temperatures. This is
because high temperatures cause
the air to expand, affecting draft and
depleting the oxygen available to the
pilot. In other words, when the pilot
flame consumes the oxygen in the
sealed combustion chamber and that
oxygen isn’t replaced by a proper draft,
the flame will go out. This, in turn, will
shut down the water heater.

This issue may be resolved by
increasing attic ventilation. Contact
a licensed contractor or a roofing
professional for guidance. See also
“Insufficient Makeup Air”

Insuffi cient Makeup Air

Adequate make-up air is essential for
combustion. A water heater takes its
combustion air from the surrounding
area, and that air must be replaced
as quickly as the oxygen is consumed.
Two factors determine the availability
of makeup air: the attic’s volume
and the total combined area of the
openings that provide outdoor air.

At a minimum, the attic should have
50 cubic feet of volume per 1,000 Btu/
hr of the total input. For example, if
your water heater has an input of
30,000 Btu/hr, the attic should have
a minimum volume of 1,500 cubic
feet under normal circumstances.
This was calculated as follows:
(30,000 ÷ 1,000) 50 = 1,500.

SUPPLEMENTS

Volume Requirement Formula:

(Inputs in Btu/hr ÷ 1,000) 50 =
minimum volume in cubic feet for
all gas appliances in the attic

Once you know the volume
requirement, you should compare it to
the actual volume of the attic. Use
this formula to calculate the volume of
the attic:

Attic Volume:
Length x Width x Height =
Attic volume in cubic feet

For example, if the attic space is 40’ x 50’
x 8’, its volume would be 16,000 cubic
feet. To provide ample combustion air,
the attic volume should be greater than
the volume requirement. If it is not,
and pilot outages have been an issue,
try increasing the attic’s ventilation.

Ventilation is always critical. Oxygen
must be replaced as quickly as it is
used. Otherwise, a pilot outage may
occur, causing the water heater to shut
down. Under normal circumstances,
a well-ventilated attic of the proper
size should provide plenty of makeup
air. However, you may need to
increase ventilation if the attic is
unusually “tight,” reaches extremely
high temperatures, or contains more
than one gas-fired appliance. Before
doing so, though, check the vents to
see if they are blocked. If they are,
unblocking them may help to improve
ventilation and lower the ambient
temperature.

If you need more makeup air, consider
an additional opening to the outdoors
as described in the National Fuel Gas
Code (ANSI Z223.1-current edition).
The opening should:

• communicate directly with the
outdoors,

• commence within 12 inches from
the top of the attic enclosure, and

• be sized at a minimum of one
square inch for every 3,000 Btu/

hrs of total input for all gas-fired
appliances in the attic. Also, the
size of the opening must not be less
than the sum of the areas of all vent
connectors in the space.

• be protected by a louver or grille as
described in the current edition of
the National Fuel Gas Code.

Alternatively, you may be able to
increase the amount of makeup air
by increasing vent capacity. Note,
however, that your venting must
be configured to provide proper air
flow. Also, the combined area of
the vent openings should be no less
than one square inch for every 3,000
Btu/hrs of total input for all gas-fired
appliances in the attic. (Note: The
net free area will be listed in the
vent’s product specifications, making
verification easy.)

Contact a licensed contractor or a
roofing professional for guidance.

Blocked Air Screen or Flame Arrestor

Most gas water heaters today have
Flammable Vapor Ignition Resistant
(FVIR) designs. These designs include
some type of screen/flame arrestor
that reduces the likelihood that
flammable vapors in the room will
be ignited by the water heater’s pilot
flame or burner flame. Of course, the
screens, filters and arrestors used in
these designs must be kept clean so
that combustion air can flow freely
into the water heater. Dust and other
airborne contaminants can block or
reduce incoming air and cause the
water heater to shut down. Screens
and filters must be kept in place and
cleaned regularly. (See p. 18.) This
is especially important in areas that are
not cleaned regularly, such as attics.

Improper Ven ng of the Water Heater

Proper venting of the water heater
is crucial for trouble-free operation.
Verify the following:

24 • Residential Standard Gas Water Heater Service Handbook

• The venting system must be installed
according to the water heater’s
installation instructions and local
codes. In the absence of local codes,
follow the National Fuel Gas Code
(ANSI Z223.1-current edition).

• The draft hood must be installed
properly and must not be modified
in any way.

• The water heater must not be
common vented with any power
vented appliance.

• Horizontal runs of vent should be
sloped upward from the water heater
by at least ¼-inch per foot. Ensure
that there are no dips or sags in the
vent run.

• The vent run should include as
few bends as possible. Each bend
increases resistance to the flow of
flue gasses. Refer to the applicable
installation code and the installation
instructions for the water heater.

• Venting must be free of obstructions
and corrosion.

• There must be no separation of joints.
Each joint must be fastened by sheet
metal screws or other approved
means. Also, vent must be supported
properly to prevent sags and joint
separation. Use of support straps or
other approved means is acceptable.

Decompression

Decompression can cause or contribute
to pilot outage. Decompression occurs
when the air near the water heater is
at slightly less pressure than the air
outside the building. Inside the home,
a classic decompression condition can
be caused by a large kitchen exhaust
fan. The negative pressure can cause
air to flow backwards through the
water heater vent, stall the air in the
flue, and cause the pilot to go out. The
same is true for a water heater in an
attic, but for different reasons.

For example, an attic may be cooled by
an attic fan, designed to pull hot air out
of the attic and move it to the outdoors.
This is a good solution for cooling an
attic, but it could cause problems for
an atmospheric gas water heater. If the
attic doesn’t have adequate free-air
openings, the attic fan could cause air
to flow backwards through the water
heater vent, causing the pilot to go out.
This, in turn, will force the water heater
to shut down. Increasing the number
or size of free air openings in the attic
may help to prevent this problem. See
“Insufficient Makeup Air” on p. 24.

Wind

Wind is only more critical for attic
installations when it occurs in
combination with one of the above
factors. The pressure needed to stop a
flue draft is less than 1/500th of an inch
of water column. If the draft through
the flue stops, the water heater will
shut down.

Water Damage

A water heater must be installed in
such a manner that if the tank or
connections leak, the flow will not
damage the living spaces below. A
suitable metal drain pan should be
installed under the water heater. Metal
drain pans are available at your local
hardware store. The pan must have a
minimum length and width of at least
2” (5.1 cm) greater that the water
heater dimensions and must be piped
to an adequate drain. Drain pan depth
must provide clearance for servicing
the igniter and burner. However, even
with the use of a drain pan piped to a
drain, water damage can still occur.

This risk can be reduced further by
installing a leak detector or water shut­off device. You can buy such devices
from plumbing supply wholesalers or
retailers. Examples are listed below:

• Sensors mounted in the metal drain
pan that trigger an alarm or turn
off the incoming water to the water
heater when leakage is detected.

• Sensors mounted in the metal drain
pan that turn off the water supply
to the entire home when water is
detected in the drain pan.

• Water supply shut-off devices that
activate based on the water pressure
differential between the cold water
and hot water pipes connected to
the water heater.

• Devices that will turn off the gas
supply to a water heater while at
the same time shutting off its water
supply.

Elevated Water Temperature

DANGER!

• Water temperature over 120°F can
cause severe burns instantly or death
from scalds.

• Children, disabled and elderly are at
highest risk of being scalded.

• Thermostatic mixing valves at each
point of use reduce the risk of
scalding.

If the ambient temperature in the attic
is extremely high, it may gradually affect
the temperature of the water inside the
water heater. For example, assume that
a water heater is set to 120°F, but the
attic maintains a temperature of 130°F
or more during the summer months.
Over time, the water temperature in
the water heater may increase beyond
the desired 120°F. As a result, the
water temperature at the outlet may
be higher than expected.

A remedy would be to decrease the
ambient temperature in the attic. This
may be accomplished by improving
ventilation. However, in doing so,
be sure that you do not create a
decompression situation (e.g., using
an attic fan without adequate free

SUPPLEMENTS

Residential Standard Gas Water Heater Service Handbook • 25

air openings). See “Pilot Outage:
Insufficient Makeup Air” and “Pilot
Outage: Decompression” for more
information (pp. 24 & 25,
respectively). In the short term,
however, open a hot water faucet and
allow the water to flow until it reaches
a safe temperature.

SUPPLEMENTS

FIELD
INSTALLATION OF
DRAFT HOODS

The purpose of this section is to show
how to properly connect draft hoods
to single- and double-wall (Type B)
vent pipe. These instructions cover
3-inch, 4-inch, and combination draft
hood sizes.

A draft hood is critical to the operation
of a gas water heater. (It is attached
between the heater’s flue outlet
and the vent pipe.) When properly
installed, the draft hood cools the
combustion products and allows them
to flow safely from the building. It
also protects heater operation during
updrafts and downdrafts that are
caused by indoor/outdoor air pressure
differences.

WARNING!

• The venting system shall comply
with applicable local and state/
provincial codes. The venting system
shall also comply with the current
edition of the National Fuel Gas
Code ANSI Z223.1/NFPA 54 (U.S.A.)
or the Natural Gas and Propane
Installation Code CAN/CSA-B149.1
(Canada).

• Each standard vent gas water heater
is supplied with a specific draft
hood. This ensures the safe, correct
operation of the water heater.
However, the draft hood must be
installed correctly.

• Do not use a draft hood other than
the one that is supplied with the
water heater.

• Do not re-use any previously
installed draft hood. Previously
used parts should be discarded.

• Do not modify, cut, or bend a draft
hood during installation.

• Do not block or restrict the open
areas around the draft hood. Do not

2

store or place objects on top of the
water heater.

• Install the draft hood securely to the
water heater and flue pipe according
to the installation instructions.
These instructions were provided
with the water heater.

• Do not use flex vent pipe or dryer
vent pipe.

• Vent pipe should be made of
galvanized steel. Do not use
aluminum vent pipe.

• Always wear work gloves when
working with sheet metal parts.

Tools and Materials

The following tools and materials
may be required to install the draft
hood and vent pipe. Other tools and
materials may be needed.

• Work Gloves

• Flat-ended pliers

• Water Heater Installation Manual

• 1/4-inch hex nut driver

• Screw driver with flat tip

• Powered screw driver tool (optional)

• Tape measure (for checking sizes)

• Sheet metal cutting tools (optional)

Types of DraŌ Hoods Covered in
this SecƟ on

3-inch Draft Hood

4-inch Draft Hood

Combination Draft Hood (3-in./4-in.)

Figure 29.

26 • Residential Standard Gas Water Heater Service Handbook

2 Originally published as 187010-000.

Types of Vent Pipe Covered in
this SecƟ on

• Single Wall - Galvanized Steel

• Double Wall (Type B) - Galvanized
Steel

InstallaƟ on Procedure

1. Determine the size of the draft

hood.

To determine the size of a draft hood,
measure across the portion that will fit
into the vent or vent connector. (Vent
connection will be covered later.)

Example:

DĞĂƐƵƌŝŶŐĂŽŵďŝŶĂƟŽŶ

ƌĂŌ,ŽŽĚ

3”

Figure 30.

4”

the legs into the slots, then
secure them with screws as
described in your installation
manual.

3. Connect the draft hood to the
venting system as described below.

IMPORTANT: The inside diameter
of the vent pipe or draft hood
connector may vary slightly by
manufacturer. Always verify that
vent connections are secure and air
tight.

In instances where correctly­matched pieces will not fit together,
use flat-ended pliers to flare the
end of the pipe or flatten its seam
joint. However, do not modify, cut,
or bend the draft hood.

To Ňare the end of the vent
pipe, bend the edge outward
all the way around the
perimeter (approx.
1/4-inch from the
edge).

If you are connecting the draft

hood to Type B vent pipe or to
vent pipe of a different size or
brand, read the Coupling section
before you proceed.

Vent Pipe

ƌĂŌ,ŽŽĚ

Figure 33.

B. Verify that all vent connections

are secure and air tight.

C. Secure the vent pipe to the draft

hood with self-drilling screws.
Also secure any new sections of
vent pipe.

Use a minimum of three screws

per connection. Screws should
be evenly spaced. For example,
three screws should be spaced at
120 degree increments around
the perimeter of the vent pipe.

2. Install the draft hood to the water
heater according to the installation
manual.

NOTE: There are two methods for
securing a draft hood. Use only the
method that applies to your water
heater model.

• Lock-in Type: Some draft hoods

have notches at the bottom of
each leg. Simply align the legs
of the draft hood with the slots
in the top of the water heater.
Insert the legs, then rotate the
draft hood. Ensure that the
draft hood is secure before you
proceed.

• Push-in Type with screws: Most

draft hoods are designed to be
secured with screws (which are
provided). Align the legs of the
draft hood with the slots in the
top of the water heater. Insert

Figure 31.

End View of Vent Pipe

If necessary, use
Ňat-ended pliers
to Ňare the end
of the pipe or to
ŇĂƩĞn the seam
joint.

Seam Joint

Figure 32.

A. Fit the female end of the vent

pipe over the draft hood as
shown below. Note that you may
need to adjust or reposition the
vent pipe during this process.

IMPORTANT: Only use screws

that are 5/8” long or less in
length.

Coupling

The opening of your draft hood will be
either 3-inches or 4-inches in diameter.
(You measured the diameter during
Step 1 of the Installation Procedure
section.)

• If you are connecting double wall
(Type B) vent pipe to the draft hood,
you must use a Type B draft hood
connector. Without this connector,
double wall vent pipe will not fit the
draft hood properly. See Type B Draft
Hood Connectors.

• Compare the size of your draft hood
opening to the size of the vent pipe.
If the vent pipe has a wider diameter
than the draft hood, use an adapter
to connect them. See Figure 34 on
page 28.

SUPPLEMENTS

Residential Standard Gas Water Heater Service Handbook • 27

• When transition to a larger vent
size is required, the vent transition
connection must be made at the
draft hood outlet. Do not connect
a 4-inch draft hood to 3-inch vent
pipe. A draft hood must only be
connected to an equal or larger­sized vent pipe (as allowed by code).

Only use the draft hood that is supplied
with the water heater.

Type B DraŌ Hood Connectors

Double wall (Type B) vent pipe will not
fit draft hoods properly. To ensure a
secure connection, use a Type B draft
hood connector between double wall
vent pipe and the draft hood.

Type B vent connectors are available
in various sizes, including those shown
below.

dLJƉĞsĞŶƚWŝƉĞ

pe B

ĂŌ,ŽŽĚ

ŶŶĞĐƚŽƌ

ƌĂŌ,ŽŽĚ

^ĞĂůũŽŝŶƚĂƚďŽƩŽŵ

of vent pipe

Increaser

4-inch Vent Pipe

ϯͲŝŶĐŚƌĂŌ,ŽŽĚ

Figure 34.

• When two vent pipes are made by
different manufacturers, they may
not fit together properly. In such
cases, use a universal adapter to
join the vent pipes. (Follow the
manufacturer’s instructions and all
applicable code.) However, do not
use a universal adapter to join the
draft hood to the vent pipe. Always
verify that the vent connections are
secure and air tight.

džĂŵƉůĞƐŽĨdLJƉĞƌĂŌ,ŽŽĚŽŶŶĞĐƚŽƌƐ

3-Inch Type B
Connector

4-Inch Type B
Connector

Figure 35.

Figure 36 shows a typical connection
between a draft hood and Type B vent
pipe.

Figure 36.

NOTE: Be sure to secure the

connections as described in step 3 of
the Installation Procedure section.

SUPPLEMENTS

28 • Residential Standard Gas Water Heater Service Handbook

NOTES

NOTES

Residential Standard Gas Water Heater Service Handbook • 29

NOTES

NOTES

30 • Residential Standard Gas Water Heater Service Handbook

NOTES

NOTES

Residential Standard Gas Water Heater Service Handbook • 31

COPYRIGHT © 2014 A.O. SMITH CORPORATION. ALL RIGHTS RESERVED.

ALL TECHNICAL AND WARRANTY QUESTIONS SHOULD BE DIRECTED TO THE LOCAL DEALER FROM WHOM THE WATER HEATER WAS PURCHASED. IF

YOU ARE UNSUCCESSFUL, CONTACT A.O. SMITH WATER HEATERS RESIDENTIAL TECHNICAL ASSISTANCE AT 1-800-527-1953 OR WWW.HOTWATER.COM.