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 Electric water heater thermostats Thermostats stick melt and come out of calibration... replace thermostat Symptoms: Cold water, uneven temperatures, reset tripping, TP releasing water Buy: Water heater thermostats at Amazon Resources: How to replace electric water heater thermostat Add another thermostat to water heater How to wire thermostats Marathon water heater thermostats Two water heaters Troubleshoot electric water heater |
  Gas water heater thermostats If tank is overheating or not heating correctly, replace thermostat Symptoms: Cold water, uneven temperatures, TP releasing water Buy: Gas water heater thermostats at Amazon Resources: How to replace gas water heater thermostat Add another thermostat to water heater Troubleshoot gas water heater |
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to 14 things for troubleshooting gas water heater 10) troubleshoot thermocouple- thermopile, pilot light Pilot light heats the thermocouple or thermopile, producing small millivoltage of electricity that travels to the gas control valve. Current from thermocouple travel to control on a hollow copper pilot tube with wire inside. Current from thermopile travel through 2 wires that pass through the TCO then to gas control. If the pilot light goes out, the lack of electric current shuts cause gas control to shut off all gas to water heater. Ordinary function is restored after pilot light is re-lit. Older model gas water heaters required a long match and patience to relight pilot, while more recent water heaters have sealed combustion chamber and use spark created by piezo igniter to re-light pilot. |
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 Image from burner assembly, or
manifold assembly salvaged off old water heater shows
the fixed-positioned bracket that holds pilot, thermopile and igniter.The piezo igniter creates spark that ignites pilot light, assuming gas valve is working correctly, gas pressure is correct, and pilot tube is clean and dry. A good pilot flame burns clear blue when water heater is receiving adequate air supply, correct gas pressure, and burner parts are clean. Color and operation of pilot flame can be inspected by looking upward through viewport located on front of combustion door.  The
pilot light performs three jobs: 1) The pilot heats the
thermocouple or thermopile which creates small electric current
that powers operation of gas control valve
2) the small current signals gas
control valve that pilot is lit so gas control will release gas into
the manifold tube and down to burner when thermostat calls for
heat, and 3) when the pilot flame is aligned correctly in front of a
burner port, and burner is clean, dry, has correct size orifice, and in
good working order, then pilot will immediately ignite the gas so
heater will heat water to set point. When thermostat senses that water
inside tank has reached set point, the gas control valve stops
releasing gas to burner, but continues releasing gas to the pilot
flame.This cycle of operation will continue as long as, parts are
functional, gas supply and pressure are within range, air suppy and
venting are adequate.A thermopile is basically several thermocouples put together. The thermopile produces more current than thermocouple. Thermopile produces enough current to power circuit board inside the electronic gas valves so it can compile status of heater operation, issue error codes via LED status light, and control operation of heater. A thermocouple produces a small current for a mechanical gas valve, but not enough current for the circuit board on electronic gas control.  Larger imageMethod 1: Open Circuit Thermopile Testing "Step 1. Following lighting instructions located on water heater label. Light the pilot and allow to operate for three minutes. If the pilot will not stay lit, hold the pilot button (rotate the gas control knob to the pilot position, push and hold in) during this test. Step 2. Using a multimeter capable of measuring millivolts, place one lead of the multimeter on the left side of the wire harness and place the second lead of the multimeter on the right side of the wire harness. Step 3. If meter reads 300 millivolts or higher, the thermopile is OK. If reading is below 300 millivolts, replace the pilot assembly. Method 2: Closed Circuit Thermopile Testing The following test should be performed while the pilot flame is on. Step 1. Disconnect the red and white pilot wires from the gas control. Step 2. Using a multimeter capable of measuring millivolts, connect one lead to the red thermopile wire and one lead to the white thermopile wire. Step 3. Following the lighting instruction label on the heater, proceed to light the pilot and allow the heater to operate for three minutes. It will be necessary to hold the gas control knob down in the “PILOT” position continuously throughout this test. A reading over 400 millivolts indicates a good thermopile output. Step 4. A reading under 400 millivolts indicates a bad thermopile, replace the pilot assembly. Another description: of method 2 Step 1. Turn knob to pilot position and depress. Step 2. Continue pressing knob and remove red (+) wire (coming from the gas contro valve) from resettable thermal door switch (the TCO) Step 3. Using a multimeter capable of measuring millivolts, connect the positive side of the multimeter to the terminal of the resettable thermal door switch. Connect the negative side of the multimeter to any earth ground location (jacket base, screw, etc.). Step 4. If thermopile reading is between 350mV - 850mV, remove multimeter and reconnect red wire to positive (+) terminal of Gas Control. Step 5. Release Gas Control knob and turn to desired setting to resume normal operation |
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 How to test thermopile / Method 3Applies to Honeywell WV8840, WT8840 series gas control valves that have TCO located on front of combustion compartment ... found on regular-NOx (not ultra low NOx) atmospheric heaters. Source: Bradford White "Open circuit Thermopile testing (Honeywell Gas Control) The following test is performed with pilot flame on. Step 1. Turn knob to pilot position and depress. Step 2. Continue pressing knob and remove red (+) wire from resettable thermal door switch. Step 3. Using a multimeter capable of measuring millivolts, connect the positive side of the multimeter to the terminal of the resettable thermal door switch. Connect the negative side of the multimeter to any earth ground location (jacket base, screw, etc.).  Normal thermopile operation will be between 350mV - 850mV. If reading is less than 350mV, replacement of pilot assembly is recommended Step 4. If thermopile reading is between 350mV - 850mV, remove multimeter and reconnect red wire to positive (+) terminal of Gas Control. Step 5. Release Gas Control knob and turn to desired setting to resume normal operation."  Note:
your water heater jacket may not be grounded ... bring over 3-prong
extension cord and insert multimeter Negative probe into ground prong |
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 How
to test TCOIs the thermal switch bad? For example TCO trips when combustion chamber is not hot. Test the TCO thermal switch. Temporarily jumper a wire across the two terminals and see if water heater functions. Buy: Thermal reset Resource: What is TCO |
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 With
the mechanical gas control valve thermostats,
the pilot flame heats the end of a thermocouple. A
thermocouple is
2 dissimilar  metals
joined together that produce small current when
heated. The small electric current travels from the thermocouple
though a hollow tube that contains a wire inside. The thermocouple tube
screws into to bottom of the control valve, where it
connects to an electromagnet. If the pilot light is ON and thermocouple is sitting in the pilot flame, and the thermocouple is working and making electrical connection to the gas control, then the electromagnet is energized. The electromagnet holds open the safety valve as long as the pilot flame is heating the thermocouple. If the pilot light is out, then the electromagnet closes the safety valve, and no gas can enter gas control. When pilot is re-lit, the magnet makes audible sound that can be detected when troubleshooting. If the pilot flame is extinguished, it can take up to 180 seconds for the thermocouple to cool sufficiently for the electromagnet to de-energize and close the safety valve. The safety valve determines if gas can flow into gas control. If safety valve is open, then gas control operates normally, and releases gas continually to the pilot light through the pilot gas regulator valve, and releases gas to burner through the main regulator valve when thermostat probe detects water temperature is below set point as selected on dial located on front of gas valve.  With the electronic gas control valve, the pilot flame heats a thermopile instead of thermocouple. The thermopile works on same principle as thermocouple, except is larger and creates more current than thermocouple, enough current to power a circuit board inside the gas control valve. Unlike thermocouple, the current from thermopile travels to gas control valve through two wires that connect to front of gas control. The circuit board controls a series of self-check routines, error compilations of water heater operation, etc and uses electromagnets to control flow of gas that enters the gas control, and gas going to pilot and burner. See basic gas water heater parts If no current is produced by thermocouple or thermopile, then gas to the valve is shut off until pilot is re-lit or defective thermocouple or thermopile replaced. The temperature-reading thermostat on a gas valve is located inside a copper tube that protrudes into tank and reads water temperature. When water temperature drops below selected thermostat setting, then the gas valve releases gas through the manifold tube and into the burner located in combustion chamber. How to adjust temperature Gas flows out of the burner where pilot light ignites gas. If burner is dirty, sooted or obstructed, the gas may not light immediately, resulting in unburned gas building up until it reaches the pilot flame causing explosion hazard. Sooted and dirty burner and yellow flame indicate this problem. After cleaning the burner and the combustion chamber, the gas should burn blue with bits of red and yellow. Clean burner |
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 Causes for pilot outage: Backdraft from shared vent and wind coming down the flue can blow out the pilot. Dirty combustion parts and need for maintenance. Bad thermopile or thermocouple. Misaligned thermocouple. Thermocouple too tight of too loose on gas control valve. Tripped TCO, thermal cut off. Not enough fresh air. Bad gas control valve and ECO can cause pilot outage. Improper venting, clogged vent, obstructed vent. Tripped FV flammable vapor system. No gas, or not enough gas. |
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| Problem and action for pilot
light issues: Pilot flutters and goes out when gas valve moved to heat: FV lockout, Bad gas control valve Pilot light gets small when gas valve moved to heat: Low gas pressure, Bad gas control valve Pilot light burns blue but flame is small: Low gas pressure, Clean pilot tube and combustion chamber, Wrong orifice installed Pilot light burns yellow instead of blue: Check proper venting, Low gas pressure, Clean pilot tube and combustion chamber Pilot constantly or periodically goes out: Check proper venting, Low gas pressure or inconsistent gas supply, Insufficient air supply clean the FV screen, Open windows and doors, Clean pilot tube and combustion chamber, Replace thermocouple, Bad gas control valve, Backdraft down the flue caused by shared vent or household vent fans, Undersized gas supply caused by too many gas appliances. Pilot will not light: Low gas pressure, Improper lighting sequence, Clean pilot tube and combustion chamber, Replace thermocouple, Bad gas control valve Pilot will not stay lit: Poor thermocouple connection at gas valve, misaligned thermocouple, defective thermocouple/ replace, ECO tripped on gas control valve or defective gas valve, TCO is tripped |
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| Causes
for pilot outage: Backdraft from shared vent and wind coming down the flue can blow out the pilot. see section 11 for venting. Dirty combustion parts and need for maintenance can also cause outage. see section 7. Bad thermopile or thermocouple. Misaligned thermocouple can also cause outage. Modern water heaters have solved the misalignment problem with fixed positioning and 1-piece replacement for combustion parts. see section 7. Bad gas control valve can cause pilot outage. see section 6. |
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 Look upward, and to one side, through sight glass to see that pilot flame is lit and clear blue color. |
Pilot
light troubleshoot: Clean the air intake, and get more fresh air to unit. Push in TCO located on front of combustion chamber. Pilot troubleshoot resources Test thermocouple How to light gas water heater Pilot light goes out Burner goes out when control knob turned to ON Pilot light will not stay lit/ pdf Pilot outage/ pdf Pilot problem or ECO or gas control? Wind blows out pilot light Pilot light or thermocouple? Negative pressure blows out pilot |
 Pilot tube orifice Clean with compressed air or carburetor cleaner Do not rub with rag, or tube can clog Pilot troubleshoot resources con't Standing pilot light maintenance Attic Ventilation and Pilot Outage Pilot outage and negative pressure Pilot light maintenance/ pdf Ventilating tight-house/ pdf Pilot light troubleshoot |
 Buy: Rheem Pilot assembly AO Smith Pilot Reliance Pilot Kenmore Pilot Bradford White Pilot |
 Gas water heater How to remove burner How to test thermocouple |
Avoid
Corrosive environments Exposure to corrosive environments such as pool chemicals, process chemicals, bleach can damage burner parts. Air is drawn into water heater, and if air contains trace amounts of chemical, or chemicals are burned in the flame, this will damage water heaters over time, and shorten life of water heater Remove chemicals from same room as water heater. -Chemicals that will corrode water heater parts and vent pipe include: 'Spray propellants, cleaning solvents, refrigerants, swimming pool chemicals, calcium and sodium chloride, household bleach, waxes and process chemicals ... all these chemicals are corrosive at very low levels with no odor." Read Bradford White Pdf pg2-8 Read Rheem pdf Avoid corrosive atmospheres |
| Piezo
igniter Today's water heaters have igniter to send spark to pilot light to start flame. Older water heaters have open combustion chamber and pilot was lit with a match ... the piezo igniter helps prevent explosion into someone's face, or ignition of flammable vapors in the room caused by open flame. The igniter is part of the FV flammable vapor prevention system where the combustion chamber is sealed so flames cannot easily travel from inside combustion chamber out into surrounding room. How to test piezo igniter How to check the igniter Electronic spark troubleshoot Troubleshoot hot surface ignition Hot surface igniter troubleshoot Power vent hot surface ignition |
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| How to check ignition cable and
spark ignitor "This procedure will expose you to 10,000 volts of electrical energy. When performing these steps do not touch bare or exposed wiring. Make sure the heater is turned off when servicing or inspecting the spark ignition system. 1. Make sure ignition cable does not contact any metal surfaces, is no more than 36 inches long, and connections to the ignition control module and ignitor are clean and tight. 2. On power vents and flue damper heaters: Check ignition system grounding. Nuisance shutdowns are often caused by a poor or erratic ground. Check for good metal to metal contact between the pilot burner bracket and the main burner. b. Check the ground lead from the GND terminal on the ignition module to the pilot burner. c. Check the ceramic flame rod insulator for signs of cracked or exposure to extreme heat. This can cause a short to ground and will prevent the pilot electrode assembly from sparking. Clean the flame rod with emery cloth if dirty. 3. Check spark ignition circuit. You will need a short jumper wire made from ignition cable or other heavily insulated wire. a. Close the gas valve manually. b. Disconnect ignition cable at the SPARK terminal of the control module. Move the ignition cable out of way. c. Energize the module by turning heater on or adjusting the thermostat to demand heat. d. Immediately place one end of the jumper firmly on the 24V (GND) terminal on the control module. Move the free end of the jumper slowly toward the SPARK terminal of the control module until a spark is established. e. Pull the jumper slowly away from the SPARK terminal and note the length of the spark gap. If the arc is 1/8 inch or more, then the voltage output is okay. If the spark is less than 1/8 inch or there is no spark, then replace the control module. f. Remove the jumper, turn heater off, reinstall the ignition cable and turn heater back on. |
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 Buy: Thermocouples at Amazon Thermocouple adapters Thermocouple Test and replacement How to test water heater thermocouple How to replace thermocouple pdf How to replace thermocouple/ forum Test thermocouple Test thermocouple and thermopile |
Thermocouple/
thermopile How to Remove burner & replace thermocouple thermopile |
How to light gas water heater Pilot light goes out Burner goes out when control knob turned to ON Pilot light will not stay lit/ pdf Pilot outage/ pdf Attic Ventilation and Pilot Outage Pilot outage and negative pressure Pilot light maintenance/ pdf Ventilating tight-house/ pdf Pilot light troubleshoot when thermostat set lower Pilot problem or ECO or gas control? Wind blows out pilot light Pilot light or thermocouple? Negative pressure blows out pilot |
| 14 things needed for gas water heater & .pdf resources | |
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What you need for
operation of gas water heater. General troubleshoot 1) Basic parts and operation 2) Adequate incoming air supply ... issues: closed doors, tightly insulated house, very hot attic. 3) Adequate air supply getting to burner... issues: dirty vent screen, dirty environment, maintenance. 4) Thermal cutoff ... TCO ... issues: failed part, maintenance, vent. 5) Flammable vapor lockout .... issues: exposure to vapors, bad FV sensor, failed FV system, 6) Fuel supply to gas valve thermostat ... natural gas and propane are different ... issues: wrong gas, low pressure, moisture in pipe, undersized gas meter, supply line too small for BTU rating. 7) Gas valve thermostat regulates fuel supply ... issues: not enough gas, failed thermostat, failed gas control valve. 8) Fuel supply from thermostat to burner ... issues: maintenance, thermocouple-thermopile, gas control valve. 9) Clean and replace burner ... issue: periodic maintenance requires burner inspection, cleaning, and possible replacement 10) Functioning thermopile-thermocouple-pilot light ... issues: misalignment, failure of part. 11) Ignition of fuel supply by pilot light or hot surface igniter ... issues: pilot light, piezo igniter, electrode. 12) Power vent water heater troubleshoot ... issues: pressure switch, blower, blower sequence from gas control, outlet polarity 13) Venting combustion byproduct .... issues: vent in disrepair, other vents in house drawing air 14) Misc troubleshoot manuals 15) How to install gas water heater 16) How to maintain water heater |
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