A.O. Smith GCV Series How to use

MODELS: GCV, GCVH, GCVL, GVR, XCV, XCVL,
XGV, XVR - SERIES 200/201
GVRL, XVRL (40-Gallon Short) SERIES 202/203
06/09 316877-000
SERVICE HANDBOOK FOR
STANDARD RESIDENTIAL
FVIR GAS WATER HEATERS
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html

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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.
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 this handbook, please contact the Technical Information Center listed on
the cover of this handbook for further assistance. Additional information is also available on the web site listed on
the 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 recommend that on every service call an inspection & cleaning of the base ring filter
and flame arrestor be performed. See page 19.
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
• 11/16 inch – 6 point – socket – for anode removal
• electrical multimeter (with alligator leads)
• digital or analog manometer
• gas pressure gauge
• water pressure gauge
• thermometer
• tubing cutter if pilot tube is to be replaced
• hose – to drain tank
• container – to measure gallons per minute flow
SERVICE HANDBOOK
Digital manometer shown.

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.
Read instruction manual before
installing, using or servicing
water heater.

PROBLEM POSSIBLE CAUSE TEST / CORRECTIVE ACTION
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TROUBLESHOOTING QUICK REFERENCE
NO HOT WATER:
Insufficient Combustion Air or Venting
Issues – combustion chamber thermal
cut off tripped.
Follow the steps on pp 18 – 19. Always check
and clean the base ring filter and the flame
arrestor.
Pilot will not light Check gas supply/Bleed air from gas line/turn
gas on.
Pilot will not remain lit when top gas
control knob is released
Test thermocouple and gas control valve/
thermostat as described on pp 20-21.
Burner will not light or remain lit. Low gas pressure – check as described on p
18. Insufficient combustion air – follow steps
on pp 18 -19.
INSUFFICIENT HOT
WATER:
Water heater improperly sized to meet
hot water demands
Compare hot water requirements with the
capacity of the water heater. See sizing guide
on p. 25. You may also use the volume test
on page 34 to analyze your hot water needs.
If necessary, install a water heater with greater
capacity.
Gas Control Valve/Thermostat set
too low
Turn temperature dial to desired temperature
as described on p. 24
Sediment or lime in the tank Drain (p. 17). Determine if water treatment is
needed (p. 29).
WATER LEAKAGE:
Condensation Adjust the thermostat setting (p 24).
Dripping Temperature & Pressure Relief
Valve
Check water supply pressure.
In closed systems, the supply pressure should
not exceed 80 psi (in a 24 hour cycle). If the
pressure exceeds 80 psi, install a pressure
reducing valve in combination with a properly
sized thermal expansion tank (pp. 35-36 & 37).
IMPORTANT: 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.

PROBLEM POSSIBLE CAUSE TEST / CORRECTIVE ACTION
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WATER LEAKAGE:
Thermostat does not shut-off Check the Gas Control Valve/Thermostat as
described on p. 20-21.
Drain valve dripping/leaking Back flush to clean- out sediment, replace if
necessary
Tank Leak Check Leakage Checkpoints described on
p. 25.

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TABLE OF CONTENTS
BASIC INSTALLATION ...................................................................................................................................... 8-16
DRAINING AND FILLING THE WATER HEATER..................................................................................................17
Draining the Water Heater ................................................................................................................................17
Filling the Water Heater ....................................................................................................................................17
CHECKING THE GAS SUPPLY FOR PRESSURE................................................................................................18
CHECKING FOR SUFFICIENT COMBUSTION AIR OR VENTING ISSUES .................................................. 18-19
Combustion Air Test ..........................................................................................................................................18
Draft Test...........................................................................................................................................................19
External Inspection & Cleaning of the Base Ring Filter ....................................................................................19
Cleaning the Combustion Chamber and Flame Arrestor ..................................................................................19
TESTING THE THERMOCOUPLE AND GAS CONTROL VALVE/THERMOSTAT ...............................................20
Thermocouple Output Test................................................................................................................................20
Gas Control Valve/Thermostat (Thermal Switch Models) .................................................................................20
REPLACING THE THERMOCOUPLE AND GAS CONTROL VALVE/THERMOSTAT ................................... 21-23
Removing the Manifold/Burner Assembly .........................................................................................................21
Removing the Burner from the Manifold/Burner Assembly ...............................................................................21
Replacing the Thermocouple ............................................................................................................................21
Replacing the Manifold/Burner Assembly .........................................................................................................22
Removing and Replacing the Gas Control Valve/Thermostat...........................................................................23
ADJUSTING THE TEMPERATURE ON THE GAS CONTROL VALVE/THERMOSTAT .......................................24
GAS WATER HEATER SIZING GUIDE ..................................................................................................................25
LEAKAGE CHECKPOINTS....................................................................................................................................25
TECHNICAL SERVICE BULLETINS................................................................................................................ 26-38
Water Hammer..................................................................................................................................................27
Mineral Buildup .................................................................................................................................................28
Aluminum Hydroxide.........................................................................................................................................29
Condensation....................................................................................................................................................30
Discolored Water...............................................................................................................................................31
Smelly Water.....................................................................................................................................................32
Chlorination Procedure .....................................................................................................................................33
Not Enough Hot Water......................................................................................................................................34
Thermal Expansion ..................................................................................................................................... 35-36
Leaking Temperature and Pressure Relief Valve ..............................................................................................37
Insulation Blanket..............................................................................................................................................38
GENERAL INFORMATION............................................................................................................................... 39-40

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Exhaust Vent to
Ouside of Building
Union
Union
Water
Shut-Off
Valve
Water
Supply- Cold*
Expansion Tank
Pressurize to Equal
Supply Water Pressure*
(Relieve water pressure
on the expansion tank
before adjusting air
pressure.)
Temperature-Pressure Relief Valve
with discharge piped to an
adequate drain. Do not cap or plug.
6” Maximum Air Gap
NOTE: Local codes
may vary.
Drain
Gas Control Valve/Thermostat
Recommended setting of 120°F.*
Metal Drain Pan piped to an adequate drai
NOTE: Drain pan diameter must be at lea
s
2 inches wider than the diameter of the
water heater.
Sediment Trap
(Drip Leg) 3” Minimum.
Gas Supply
To Fixtures - Hot
Air is drawn in for combustion.
Keep area clean and free from
flammables and flammable vapors.
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.
INSTALLATION OF RESIDENTIAL GAS WATER HEATER
See Labels and
Installation Instructions
and Use & Care Guide
for clearances.
* NOTE: If on a well system the expansion tank should be set to the maximum pressure of the pump tank.
** White-Rodgers® gas control valve/thermostat shown in this figure. The valve may vary according to model and year.
*Massachusett: Install
a vacuum relief in cold
water line per section
19 MGL 142.
Do not cap or plug.
Union
Manual Gas
Shut-off Valve
Untempered
Hot Water
Tempered Water
To Fixtures
Cold
Water
Inlet
Hot
Water
Outlet
Mixing Valve
(Set to 120°F)
Follow the Mixing
Valve Manufacturer’s
Instructions
BASIC INSTALLATION & OPERATION
Figure 1

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This portion of this handbook applies to the Operations and Servicing of Residential Gas, Tank Type, Water
Heaters, which are vented atmospherically and use a thermocouple as their electrical source.
Control: There are two gas control valve/thermostat configurations available. Both valves have similar control
elements such as the Gas Control Knob & Water Temperature Dial. Both valves have high water temperature limit
safety. Please note the location of the control elements on the following figures.
Hot Water
Outlet Cold Water
Inlet
Draft Hood
Flue Baffle
Anode Rod
Foam Fill
Hole
Draft Hood
Temperature-Pressure
Relief Valve
Dip Tube
Flue Baffle
Gas Control Valve
/Thermostat
Drain Valve
Anode
Rod
Flue
Tube
Jacket
Temperature Probe
/High Limit Probe
Gas Control Knob
On|Pilot|Off
Water
Temperature
Dial
Water
Temperature
Dial
Gas Control Knob
Off|Pilot|On
Setting Indicator
(Index Bar)
Thermal Switch
Wire Leads
with Connectors
(some models)*
Reset
Button
Robertshaw®
Gas Control Valve/
Thermostat
White-Rodgers®
Gas Control Valve/
Thermostat
Gas Supply- Inlet
Gas
Supply
- Inlet
*NOTE: Some models do not have thermal switch wire leads as shown in this figure.
** Manifold Gas Pressure Taps are located on the underside of the gas control valve/thermostat.
**Manifold Gas
Pressure Tap
**Manifold Gas
Pressure Tap
BASIC INSTALLATION & OPERATION
Figure 2

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Burner/Manifold Door Assembly: The burner/manifold assembly consists of several components such as:
main burner, burner orifice, manifold tube, pilot burner, pilot orifice, pilot tube, igniter, and thermocouple. See the
figure below for the complete list of components.
The pilot burner remains on once it is manually lit. When incoming cold water activates the thermostat, gas flows
to the main burner. The pilot flame ignites this gas. The main flame burns until the tank reaches set temperature
then the thermostat interrupts this main gas flow.
Burner Orifice*
Main Burner
Pilot (Burner)
Thermocouple
Burner Screws
Manifold Door
Door Gasket
Manifold Tube
Pilot Tube
Igniter Wire
View Port
TCO (Thermal Cut
Off) Switch
Igniter Wire
TCO (Thermal Cut
Off) Sensor
Front View
TCO Reset
Button
Pilot (Burner)
Thermocouple
Pilot Orifice*
Ferrule
Pilot Nut
Pilot Tube
Pilot Bracket
*DO NOT operate the water heater without the pilot and burner orifices installed.
NOTE: The base of the
Thermocouple must be
flush with the base of
the pilot bracket.
Pilot Assembly View
Piezo Igniter Tip
BASIC INSTALLATION & OPERATION
Gas Control Knob
Reset
Button
Pilot
Flame
Safety Valve
Safety Valve
RobertShaw Gas Control Valve/Thermostat Shown.
Figure 3
Figure 4
Normal Operation
Pilot: The pilot flame heats the end of a thermocouple.
As the thermocouple gets hotter, it generates a small
(cannot be detected without an electrical meter)
electrical current to the bottom of the gas control valve/
thermostat. This current powers the electromagnet
and holds open the main gas interrupter as long as the
pilot flame is heating the thermocouple. The normal
voltage for a properly working thermocouple is between
20 and 30 mv. DANGER! If the pilot is extinguished,
it can take up to 180 seconds for the thermocouple to
cool sufficiently to close the safety valve.