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How to replace Honeywell Gas control valve
Do not drain water from tank
Icon gas valve  
For atmospheric vented heaters
WV8840 Honeywell gas control valve ... powered by thermopile.
Water heater does NOT plug into 120 volt outlet
Covered on this page
For atmospheric vent models, do not empty water heater, valve body can be replaced while tank is full of water
Range Low 55° - very hot 160°F
Average bath 110°F, typical water heater temp 120°F
Severe scalding risk over 135°F
ECO limit 180° F, if ECO trips, gas valve fails (except newer WT seriesw valves)
TP release water at 150 psi or 210°F
All calibrations are approximate
To reset gas control, rotate dial to OFF, wait 10 minutes for gas to clear. Then relight.
Buy newer model WT8800 series:
WT8840B1000 at Amazon
WT8840B1500
WT8840A1000
WT8840A1500
See replacement chart
Buy
Rheem WV8840C gas control
Honeywell gas control at Amazon
American / Honeywell gas control at Amazon
Honeywell gas valve for propane
Honeywell natural gas valve
Reliance NG at Amazon
Reliance LP at Amazon
Kenmore water heater gas valve
WT8840B1000 natural gas at Amazon

Replacement instructions
How to test & replace Honeywell/ pdf
WT8840 replacement manual

Resources WV8840/ WT8840:
Typical installation manual
Typical installation manual/ low NOx
Adjust temp on Honeywell gas valve
Error codes WV8840 series
Error codes WV8840 series
Error codes WT8840
AO Smith service handbook
Service handbook
State Error code/ troubleshoot/ service manual/ FVIR
Bradford White service manual
Error light blinking 4 times
How to light water heater
How to light water heater/ pdf
How to light Whirlpool energy smart

WT8840 product overview models
WT8840 gas valve manual and troubleshoot

How to replace gas control valves
How to test gas control valve

How to install gas water heater

 

For power vent and flue dampered heaters flue dampered heaterWV4460E Honeywell gas control valve ... powered by 120 volt or 24 volt
Water heater plugs into 120 volt outlet

Covered on this page
do not empty water heater
Range Low 90° - very hot 160°F
Average bath 110°F, typical water heater temp 120°
Average bath 110°F
ECO limit 188° F, if ECO trips, gas valve fails
TP release water at 150 psi or 210°F

Full valve eplacement instructions on separate page
How to replace Honeywell power vent water heater gas valve

Buy
Example Honeywell gas control valve at Amazon
Reliance NG at Amazon

Resources
Flue dampered service manual/ atmospheric
Flue dampered/general install and troubleshoot
Dampered troubleshoot codes
Dampered error codes
Dampered error codes
Induced draft troubleshoot codes
Example dampered install manual2

Example power vent install manual
Example power vent install manual
Example power direct vent install manual
Adjust temperature/ error codes on Honeywell
How to light Honeywell gas valve
Error codes and troubleshoot chart
Error codes
Error codes
Icon gas valve error codes

AO Smith service handbook
Bradford White power vent service manual 1
Bradford White power-vent service manual 2
Bradford power-direct-vent service manual
Condensing power vent service manual
Test gas control/ from BW service manual
Sequence of operation
How to clean burner
Icon gas valveThe WV8840, used for atmospheric heaters, is being phased out for the newer WT8840 ... (year 2020)

Can you install the newer Honeywell WT series gas valve on your AO Smith brands* or Bradford White water heater? Yes. It will probably require removal of gas valve from tank.
To change from older WV series to newer WT series, match numbers shown on chart with the model number shown on label located on side of your gas valve ... note the brand of heater, insulation thickness by removing burner door or TP valve ... and of course note if your valve is natural gas or propane.
WV880 to WT8840Buy:
WT8840B1000 at Amazon
WT8840B1500
WT8840A1000
WT8840A1500
Resource:
WT8840 replacement manual
WT8840 product overview models

What is the difference between WV8840 and WT8840?
Answer: Response to Error code 4

1)  Gas valves come out of calibration and have other problems ... it is unavoidable that they do fail. The older WV8840 requires gas valve replacement if error 4, overheated tank, occurs ... even if water inside tank is not overheated to the ECO trip point of 188-199°F.
It is most likely that error 4 is a temporary misread and that water inside tank did not reach 188-199°F.
It is possible that water could reach 188-199°F since the TCO located of front of burner compartment (or inside the burner compartment on ultra low nox heaters) shuts down combustion at 190-200°F. The TCO is a thermal cut off switch that can be reset if located on front of burner compartment, or replaced on ultr low nox models.
The newer WT8840 is more flexible, letting you reset error code 4 if the gas valve temperature sensor or circuit board has experienced a temporary misread.

2) As near as I can tell, there is a higher ECO limit on the new WT series gas valve .... the older WV high limit is 188-199°F and newer WT at 210°F, which is more in line with commercial water heater gas valves that trip at higher temperatures than residential heaters.
What is ECO? Energy cut off or high limit. The Honeywell gas valve has a thermostat probe located on back of gas valve that extends into water. The probe holds a thermistor that connects to circuit board via 3 wires. As water temperatures inside tank rise and fall, the thermistor produces small variation in current that circuit board interprets as change in water temperature. If the resistor senses temperatures over the ECO limit, or the high limit, then circuit board on the older WV series will fault the gas valve into failure, and issue error code 4.
Error code 4 on older WV gas valve requires a new gas valve
Except error 4 is more likely a temporary misread of water temperature than your tank actually overheated to 188-199°F ...  of course a misread can result if thermostat probe is coated with sediments (do the recommended maintenance and flush tank each 6 months), and the variable resistor (thermostat) and circuit board can fail .... but if gas valve is functioning correctly, and there are no other problems .... then the cause for error 4
should be repairable with simple dial-down of temperature and maybe ON-OFF cycle of heater by setting gas valve knob to off, waiting 10 minutes and then relight heater ...
except the older WV880 will not accommodate repairs ... and error code 4 is a failed gas valve.
You might be able to reset the circuit board DIY as shown following link: error code blinking 4 times

4) The newer WT8840 also issues error code 4 and shuts down heater, but does not have same fatal condition as older WV8840 (in all circumstances).
Error 4 on newer WT8840 doesn't mean the gas valve is OK .... you might still need a new gas valve if the variable resistor or circuit board failed ... however if the gas valve experienced a temporary misread, then the newer WT gas valve usually does not need to be replaced.
Dial down temperature a bit ....
and if needed, cycle the gas valve OFF using temperature dial located front of gas control valve, wait 10 minutes for gas to clear, then relight heater, and the newer WT8840 gas valve should be functional again.
Resources:
How to light heater .pdf 
Read error code blinking 4 times
Why I do not recommend Rheem water heaters

*AO Smith brands include: State, American, Reliance, Kenmore, Craftmaster, Lochinvar, Kenmore etc
Where is Rheem? LOL. Rheem has proprietary model numbers for their gas valves to prevent folks from buying a generic elsewhere and installing the gas valve themselves. Rheem owns your repair work, and basically expects to own their water heaters even after sale is made ... unlike Bradford and AO Smith that post service manuals and have good troubleshoot and maintenance in their product manuals .... Rheem has no service manuals available to the general public ... and scant maintence and troubleshoot in their product manuals, instead telling customers to call for service. This is rediculously expensive for prople and renders the public powerless to learn and expand skills.
Honeywell gas control valve     AO Smith gas control valve Reset gas control to see if it will work:
Rotate dial to OFF, wait 10 minutes for gas to clear.
Then relight.  

This type gas control valve is powered by thermopile. Water heater does not have thermocouple. Thermopile is basically several thermocouples together. The thermopile produces enough current to power small circuit board inside gas control valve that monitors status and issues error codes.
How to light water heater
How to test gas control
Other things to try, depending on fault code
Turn off gas valve. Turn off heater. Flush the water heater, to help clean out sediment.
Remove the TCO wires plugged into front of unit in lower right corner, clean lightly, then replug into front with red inserted into side marked red, and white to other side marked white. Push in TCO reset button located on front of combustion chamber.
Check warranty status
Gas control valve and other parts are covered for full length of warranty period.
For example, AO Smith commercial-grade for residential heaters have 6 year tank and parts warranty ... and may offer extended warranty.
Labor for replacing parts or failed heater is covered in first year of warranty.

Model number and serial number are located on label on side of water heater.
Serial number contains code for year of manufacturer. Find age of water heater
Contact manufacturer.
Honeywell gas control label
AO Smith heater with 1" insulation
Identify gas control numbers to buy replacement
Order gas valve replacement
Located on side of gas control valve
WV8840B1042  ... AO Smith heater with 1" insulation
This natural gas valve was taken from failed AO Smith water heater 2012 that was replaced under warranty coverage.
Buy newer version
WT8840B1000  AO Smith brands (Reliance, State, Lochinvar, American etc) 1" insulation
WT8840B1500 AO smith 2" insulation
WT8840A1000 Bradford White 1" insulation
WT8840A1500 Bradford White 2" insulation
See replacement chart
Buy natural gas
Honeywell gas control at Amazon
American / Honeywell gas control at Amazon
Honeywell natural gas valve
Reliance NG at Amazon
Buy: Propane/ LP
Reliance LP at Amazon
Honeywell gas valve for propane
 Bradford White gas water heater   Turn off gas valve
Turn Gas valve OFF
Turn OFF incoming gas line
Rotate handle perpendicular across gas line.
Do not drain water from tank


Move gas valve knob to OFF


Wait 10 minutes for gas to clear
Honeywell gas control valve Black pipe union
Black pipe union
1/2" Black pipe Union. Use 2 wrenches
Keep pipe clean
Honeywell gas control valve Yellow flexible gas line
Protect end of pipe from dirt
Remove old teflon tape.
Keep all debris from inside of pipe.

Keep gas connections clean
Buy:
Irwin Hand tools
Klein hand tools
Remove gas line from gas control valve
You can reuse pipes and flex line ... no need to buy new.
Do NOT wash out pipes or flex lines with water etc.
1) Do not let pipe ends get dirty. Dirt, loose teflon tape etc will get sucked into gas valve ... will clog tiny orifices (holes) inside the new gas valve that are designed to limit the flow of gas going into the pilot and manifold tubes, causing gas valve to fail. See image
Carefully remove old teflon tape, and keep debris out of pipe.
Cover pipe ends and threads with household tape to protect from dirt.

2) Note how tight gas line is connected to gas control.
Gas pipes are not overtightened into gas control valve or it can ruin new gas valve.
With black pipe connection, use two wrenches to take apart union. Then disconnect black pipe from old gas control.

3) Gas water heaters with large BTU consumption: do not use yellow flexible gas line ... use only black pipe connection to ensure adequate gas flow.

4) Typical residential 30,000-50,000 BTU heater can use flexible gas lane.
Back of yellow flex package has BTU size chart.
Water heater BTUs shows on label located on side of tank




Honeywell gas control valve
Larger image
Disconnect manifold tube, igniter wire etc
1) Pull out plugs with red and white wires located on front of gas control ... FYI these wires connect to the TCO located on front of combustion chamber and to thermopile located inside burner.
2) Piezo Igniter wire comes apart
3) Unscrew manifold tube ... note tightness of connection ... no pipe sealant or teflon tape is used. Keep pipe clean.
4) Unscrew pilot tube (smaller tube) ... no sealant is used.
5) Pilot tube is reverse thread for propane
6) Remove phillips head screw that holds front cover in preparation for removing cover

Honeywell gas control piezo igniter Disconnect piezo igniter wire
WV8840 Gas control valve
Larger image
Temperature sensor, igniter and gas control can be replaced without draining tank.
Resource: Bradford White service manuals p24
Do not drain water from tank on atmospheric type
Loosen screw from front of gas control
Take apart gas control valve
Backplate remains installed.

How to remove Honeywell gas control.
1) Remove 1 phillips head screw to left of pilot tube that holds cover (shown in image above).
3) Remove plastic gas control cover. Press down on top of gas control cover to help release gas valve cover. Tip plastic cover out from bottom, and then pull straight back toward you and cover snaps off. Caution: plastic cover is connected to body with 3-strand yellow-orange-white wire.
4) Disconnect yellow-orange-white wire that connects to temperature sensor. Wire is plugged into circuit board on plastic cover. Grasp wire and pull upward to unplug wire from circuit board..

Internal Parts are not sold separately
year 2020 ... My experience shows that control board and thermostat can both go bad ... or one or the other goes bad.
If you have an old Honeywell valve laying around that has same manifold pressure and rated for same type gas, try replacing either part... while this action may pose extreme hazard, and choosing safety over money is not best course, some folks might want to experiment.
Honeywell gas control
Larger image
How it the valve body looks with front cover removed and circuit board pulled off
Circuit board is attached to front cover and can be taken out if desired ... the board lifts off 3 pins located on gas valve body ... these are the points of electrical connection and how the circuit board controls the solenoid valves inside the body ... circuit board is connected to the thermistor (thermostat) via the 3-strand yellow-orange-white wire that appears top of image.

The valve body is removed next ... 2 clips and 1 screw hold valve body to backplate. (the valve body is not taken apart, instead it is a complete sealed unit).

The backplate stays attached to tank (assuming new and old models have same connection points and screw holes line up)

Pull the variable resistor (thermostat) out of the probe section of gas valve that extends into tank. The thermostat is not attached to the backplate .... it should just come straight out by gently pulling the yellow-orange-white wire.
Honeywell gas control valve Close up of clip that holds Valve Body to Backplate
5) Remove valve body from backplate
Models generally have 2 plastic clips and a screw that hold valve body to backplate. Clips are located at bottom on right and left side. Use screwdriver to push 1 clip down while while using another screwdriver to pry valve body outward. Then use screwdriver to push down other clip to release valve body.

Note the pressure tap is for checking the gas pressure
Resource: How to test gas pressure
Honeywell gas control valve Replace valve body and other non-functioning parts
Reverse the steps you performed to remove the gas valve
Make sure that circuit board is seated over the 3 pins that stick out from new gas body.

Reinstall cover

Push cover straight onto backplate.
Snap two top pieces into backplate
Put screw into bottom
For power-vent and flue-damper models that plug into 120 volt outlet

 ''Removing Electronic Control Module

1. Set the gas control valve/thermostat to its lowest setting by turning the knob counter-clockwise to the VAC point

2. Turn gas control switch to the “OFF” position and turn off the gas supply to the unit.

3. Disconnect the electrical power to the water heater from the wall outlet.
-pull out molex connection(s) or wire harness at bottom of gas valve
-remove maniforld tube etc as shown steps higher on page

4. Remove the front Torx screw at the bottom of the gas control valve/thermostat.

5. Use a flat-blade screwdriver to release the two tabs at the top of the gas control valve/thermostat and lift the electronic control straight up .

6. Disconnect the temperature sensor cable.

Note: When removing the control module from the gas control assembly, disengage the pins on the valve module without causing damage.

7. Re-assemble in the reverse order.
 Note: During re-assembly, align the pins on the valve module to their proper location in the control module without causing damage.''

Resource manual
''Removing Valve Module
1. Set the gas control valve/thermostat to its lowest setting by turning the knob counter-clockwise to the VAC point

2. Turn gas control switch to the “OFF” position and turn off the gas supply to the unit

3. Disconnect the electrical power to the water heater from the wall outlet.

4. Remove the Electronic Control Module as outlined in
“Removing Electronic Control Module” above.

Note: When removing the control module from the gas control assembly, disengage the pins on the valve module without causing damage.

5. Remove the screw and the ground tab with a Torx screwdriver

6. Insert a fl at-blade screwdriver between the casting and the locking tabs at the bottom of the valve.

7. Carefully pry against the casting until it barely slides past the locking tab edge.

8. Repeat on the opposite side.

9. Replace the valve.
Note: When replacing the valve, do not apply pressure with the hand on the valve pins.

10. Re-assemble in the reverse order.
Note: During re-assembly, align the pins on the valve
module to their proper location in the control module
without causing damage.''
 ''Removing Temperature Sensor and Cable
1. Set the gas control valve/thermostat to its lowest setting
by turning the knob counter-clockwise to the VAC point

2. Turn gas control switch to the “OFF” position and turn
off the gas supply to the unit

3. Disconnect the electrical power to the water heater from the wall outlet.

4. Remove the Electronic Control Module as outlined
in “Removing Electronic Control Module” section above.
Note: When removing the control module from the gas control assembly, disengage the pins on the valve module without causing damage.

5. Remove the Valve Module as outlined in ”Removing
Valve Module” section above.

6. Use a screwdriver to pry under the sensor retainer finger to remove the temperature sensor and cable

7. Re-assemble in the reverse order.
Note: When replacing the valve, do not apply pressure with the hand on the valve pins.
Note: During re-assembly, align the pins on the valve module to their proper location in the control module
without causing damage.''
  Yellow flexible gas line Reconnect gas line using yellow teflon
Apply yellow teflon tape.
Must have yellow teflon tape of approved sealant.
Leave first two threads clean with no tape.
Do not let dirt, stray teflon, or any debris enter gas line. Make sure gas line is clean.
Do not overtighten gas line to gas control valve, or it can damage valve

Reconnect tubes and wires
NO tape teflon on pilot tube or manifold tube
Do not overtighten manifold tube. Give is a snug tighten as noted when taking apart.

Pilot tube is snug tight. No sealant or tape is used.

There is no thermocouple with this type gas valve ... and therefore no copper thermocouple to connect to gas valve ... because unit is powered electrically via the thermopile that connects via the red-white wires.

Plug in thermopile-TCO wires on front ... red wire on left and white wire on right as marked on plastic cover

Reconnect piezo igniter wire.
Test Honeywell gas control for leaks

Smell for gas leak
Natural gas is lighter than air, and gas smell will rise
Propane gas is heavier than air, and gas smell will fall to floor
Turn Gas ON
Test for gas leak
Apply soapy water to each gas connection
a) Test gas line or flexible pipe: Mix liquid soap with water and use brush to put around around gas line joints to see if there are bubbles. Use plenty of soapy water.

Wait: It will take time for bubbles to appear since gas is under low pressure.
Soap bubbles coming from joint indicate leak: retighten pipes, use teflon tape on yellow flex pipe and black pipe.
Do not overtighten pipes or damage can occur to gas control valve.

b) Test factory-installed connections located below gas control valve
Manifold and pilot tube connections located under the gas control valve do NOT use teflon tape.
See image of manifold and pilot tubes
If either tube under gas control valve is leaking, then tighten a little bit. Do not overtighten.
Manifold and pilot tube: look for reverse thread on LP water heater. Regular thread on NG water heater
Remember: Natural gas and propane gas both have less pressure on the line than water pipes, so gas pipes are easy to seal with ordinary wrench. If you can install water line without leaking, you can do the same with gas line. Do not over-tighten connections.
WV8840 Gas Valve
See larger
Light water heater:
Instructions printed on face f gas control to right of knob
Rotate knob to OFF, wait 10 minutes for gas to clear.
Rotate knob to Pilot
Press in and hold knob in Pilot position
Press piezo igniter button until pilot lights
You should hear click sound, keep holding down knob
Release knob when status LED blinks

Larger image of instructions
How to light water heater
Icon gas valve Adjust temp
All water heater temperatures are approximate
Calibration of temperature should be within 10°-15° of temperatures shown on chart

Use mixing valve when temperature setting is above 135°
Risk of scalding when temperatures exceed 120°
Typical bath-shower is 110°

Buy from my affiliate links:
Mixing valve kit at Amazon
Water heater mixing valves at Amazon

Resource:
Advantages mixing valve
Honeywell WV8840 circuit board
Larger image
COM port/ communication port connects on RX TX GND located at bottom of image
GND is ground, other two contacts are unknown
WV8840 communication port
Image shows front and back of circuit board flipped in photoshop so front and back can be laid over top of the other.

I cannot find a spec sheet showing model numbers, or differences between models.

Circuit board is powered by current generated by heating thermistor. E1 and E2 in lower right corner connect to thermistor.
Bradford White Service manual

The Bradford White gas water heater timer connects to COM port on Honeywell gas control valve thermostat. Timer is for specific models only.

I do not know how the 24volts interfaces with the RX TX GRD communication terminals on the gas control valve thermostat.
April 2020:
Years ago, Bradford white had a setback controller that interfaced with the COM port  It was powered by 24 V transformer .... meaning that the com port is NOT powered by the thermopile that powers the circuit board and gas water heater operation.
The setback controller was able to disable gas valve until a setpoint was reached ... so I assume all it did was turn off circuit to gas valve until thermostat probe signaled that a lower temperature was reached.It’s too bad that folks did not buy the setback controller just so today's com port mystery could be solved Other than that information, some guy sent me a pdf that makes no sense to me
honeywell-gas-control-communication-port.pdf
honeywell gas control valve circuit board
Larger image
Second example of circuit board shows numerous differences between the two boards. Basic layout appears the same, but the circuit board has different type of connection points for relays
More pictures of Honeywell
Bradford White ICON gas valve
Spec sheet showing model numbers, or differences between models is unavailable at Honeywell except for following resource: WT8840 product overview models
As near as I can tell, the WV8840 and WT8840 are rather generic ... but the circuit boards vary somewhat from the gas valves I've examined.
Circuit board is powered by current generated by heating thermistor. E1 and E2 in lower right corner connect to thermistor.
Bradford White Service manual

WV8840 communication port, or COM port
The COM port or communications port is available to water heater manufacturer for connecting a 'future' product.
In 2020,  there is no method to utilize this port for DIY innovation.
Bradford White uses the COM port to connect their 'setback controller' ... the design has gone through changes, and the application is unclear today.
Read about BW setback controller

Service manual (10Mb)
Service manual 2
This gas control used for power vent models
Honeywell makes 2nd style gas control for power-vent and flue-damper models
FYI ... each major manufacturer of flue damper heaters uses this style gas valve ... gas valves for the AO Smith and Rheem flue damper heaters are powered by 24 volt AC ... while Bradford White gas valve is powered by 120 volt. This implies that models for this type gas control valve vary more widely than the Honeywell gas valve covered on this page.
The situation with power vented models is unclear to me at this point, since there are a wider variety of power vented models than flue dampered models, 2020.
To reset gas valve:
Slide on-off switch to OFF position.
Go to blower system located on top of water heater and turn blower switch to OFF.
Turn off all electric power to water heater appliance.
Set Red knob to LOW.
Wait 5 minutes to clear out gas.
Check for the smell of gas that would indicate a leak.
Turn on electric power to water heater
Set blower to ON position.
Slide on-off switch to ON position.
Set Red knob thermostat to desired temperature.
Troubleshoot this style Honeywell: see resources at very top of this page
How to light power vent Honeywell gas valve

Honeywell gas valve error codes
Adjust temperature/ error codes on Rheem Honeywell
How to light this type of gas valve:
Review AO Smith flue damper heater
Remove gas valve Gas control valves can be removed

How to replace gas valve thermostat
Troubleshoot power vent water heater
 


Troubleshoot gas water heater/ all gas valves

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