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Troubleshoot gas water heater thermostat |
Buy: Flexible gas line Keep ends of pipe connections clean when installing or repairing gas supply or water heater. Do let stray pieces of teflon tape get inside pipe... wrap tape one second thread from end and not at end. Install sediment trap and loop on flexible gas line to keep out moisture and debris. Use black pipe and yellow flexible gas line. Do not use galvanized pipe or flakes of galvanized will chip off and get into gas control. Do not use copper pipe unless approved locally.. |
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to 14 things for troubleshooting water heater 5) troubleshoot fuel supply to thermostat Natural gas and propane gas are different. Water heaters are purchased by type of gas used. Propane requires greater ratio of incoming air supply than natural gas. Propane has higher ignition temperature and burns hotter. The gas control valves are different with different threads for each type of gas. The burner and internal parts are different. Natural gas is lighter than air and rises. Propane is heavier than air and falls to low spot. Do not install propane appliances below ground level where gas leak can accumulate in basement. Water heaters are rated by BTU, or the amount of gas they burn. Gas lines and gas meters are rated by BTU for the amount of gas they can supply. Higher elevations consume more gas to achieve same BTU output. New appliance, or too many appliances can affect amount of gas. If overall consumption of BTU is greater than supply, then water heater will not function. Larger gas meter, or gas line may be needed. Look at labels on each appliance. Call gas supplier. Do not use copper pipe or galvanized pipe. Use only black pipe or yellow-colored flexible gas line. Check local codes for approved pipe that is non-reactive to the type of gas being used. Dirt, debris, moisture, galvanized flakes etc from wrong pipe or dirty pipes will get into the gas control valve and cause it to malfunction. yellow is international color code for gas line. Acceptable to reuse flex line when installing new appliance. |
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Resources: Definitions and formulas/ pdf Pipe size BTU chart Pipe capacity Square footage per BTU Gas pipe capacity .pdf |
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Thermostat
Calibration Thermostats are calibrated within a range, and not intended to be precise like a scientific instrument. Thermostats have 2 ranges for calibration: First calibration is actual temperature of water vs thermostat setting. Set thermostat to 120° and water temperature might be 115° or 125°. Typically, the range is +/-5°. Second calibration is the differential of water temperature before water heater turns on. How LOW will the water temperature get before the water heater turns ON?. On gas water heater, 'water temperature around the thermostat probe can drop 15-25°F before main burner is activated.' Water at bottom of tank can be 95° and top of tank still be near 120° thermostat set point. Resource/ page 10 If differential is greater than 20%, the thermostat should be replaced. Other things affect the actual water heater. If a water heater is short cycling, where it turns on-and-off too frequently, it can mean thermostat calibration is too narrow, however thermostat are not 'fast-acting' and problem can be caused by other issues, such as water leak or stacking, Deadband/ applies to gas and electric thermostats Deadband is a range of input that doesn’t result in any output. In this range, the thermostat fails to trigger any activity. Deadband sometimes causes thermostat to overshoot its setpoint. The effect can be occasional or sporadic and indicates thermostat failure and need to replace. |
Check
gas pressure on gas water heater: Watch what appliances do when adding load. If appliances stop working correctly when another gas appliance is activated, it implies low gas pressure. This observation can be done without equipment. Check rating plate (label) located on side of water heater for gas pressure rating Typically, a propane heater will be higher than natural gas. Line pressure is pressure on incoming gas line. Label shows max inlet or line pressure as 14.0" w.c. Manifold pressure is gas pressure from gas control valve to burner. Label shows 4.0" w.c. to 5.0" w.c. for manifold pressure. "The Gas Control is designed for a maximum line pressure of 14.0" w.c. and a minimum line pressure of 1.0" w.c. over the water heater’s rated manifold pressure. Line pressure must be checked with the main burner on and off to assure proper readings." If the burner and/or pilot do not function, service checks for gas pressure, thermocouple output, magnet assembly and ECO are to be performed. If these check OK, the gas valve may be faulty." "MANIFOLD PRESSURE TESTING (this procedure assumes a maximum line pressure of 14.0" w.c.) Step 1. Set gas valve to “OFF” position. Step 2. Remove pressure tap plug located on the bottom of gas control valve (or side of Intellivent gas valve) and install pressure tap. Step 3. Connect manometer to pressure tap. Step 4 Follow lighting instructions and light main burner and observe manometer reading. Step 5 Proper operating range for natural gas is 4.0 ±0.5" W.C. For intellivent 3.5 to 4.0" W.C. Proper operating range for L.P. gas is 10.0 ±0.5" W.C. Image above shows Honeywell gas control valve Step 6 If pressure is OK, set gas valve to “OFF” remove manometer and pressure tap and replace pressure tap plug. Check for gas leaks before placing water heater back in operation. If pressure is out of the specification noted in step 5, proceed to step 7 or 8 for proper service procedure. For Honeywell electronic and White Rodgers Intellivent control, the manifold pressure is not adjustable. If manifold pressure is outside the range in step 5, the gas control valve must be replaced. For White Rodgers mechanical control, the manifold pressure is not adjustable. If manifold pressure is outside the range in step 5, the gas control valve must be replaced. For Robertshaw mechanical control, the manifold pressure is adjustable, proceed to step 7 for adjustment procedure Step 7 While burner is in operation, remove regulator access cap to expose the regulator adjusting screw. With small screw driver, rotate adjusting screw clockwise to increase pressure and counter clockwise to decrease pressure. Step 8 Replace regulator access cap, set gas valve to “OFF”. Remove manometer and pressure tap and replace pressure tap plug. Check for gas leaks before placing water heater back in operation." Buy Manometer Resources: Bradford white service manual Pg 15 Intellivent service manual |
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to 14 things for troubleshooting water heater 6) troubleshoot gas water heater thermostats Thermostats are usually single-use after ECO (energy cut off) trips. Exception, some Intellivent and Honeywell thermostats can be reset using button sequence. -ECO Energy Cut Off is located inside the thermostat probe that extends into the tank to measure water temperature. When ECO senses overheating inside tank, the ECO trips and shuts off gas control. -If ECO is tripped, or other malfunction, Gas valve must be replaced. -ECO must have continuity so small current (derived from thermocouple or thermopile when heated by pilot light) can travel from thermostat through the ECO and back again to thermostat, completing the electric circuit, and signaling to gas control to function normally. -If water heater burner or pilot light has gas, if pilot or burner flutters and goes out, then ECO is not tripped: Gas thermostat might still be bad, but FV system or related maintenance is first suspect. -Do not install cold water line above gas valve where condensation drips on valve. Thermostat calibration means tank temperature matchs thermostat setting. All setting are approximate and vary widely. Adjust temperature, replace gas control if temperature setting is unreliable. Resources Pilot outage troubleshoot Test ECO on Robertshaw- White Rodgers ECO on Robershaw,White Rodgers, Honeywell pg 17 Read about resetting intellivent How to adjust thermostat temperature Buy Gas water heater thermostats at Amazon |
\Image show the thermostat probe, containing both the ECO and the heat-sensing thermopile. Thermopile, the center rod in image, responds to heat by creating small electric current that is interpreted by the gas control and determines when gas is released to burner. |
"Test Energy Cut off (ECO) White
Rodgers Step 1. Disconnect thermocouple from gas valve. Step 2. Using a multimeter capable of measuring Ohms (or continuity), attach one lead (alligator clip) to the pilot tube. Insert the other lead (probe) fully into the magnet opening, Be sure the probe makes contact only at the top center of the magnet opening. Do not allow the probe to make contact with the threaded sides of the opening. Step 3. If continuity is indicated, the ECO is OK. If continuity is not indicated, the ECO has opened and the gas valve must be replaced" Test Energy Cut off (ECO) Honeywell "The Honeywell Gas Control is designed with an ECO device that will reset. To reset the Gas Control after an error code (4), turn the Gas Control knob to the “OFF” position and wait a minimum of (5) minutes before relighting following the instructions located on the lighting instruction label or the lighting instructions located in the installation and operation manual" |
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 control. How to test thermocouple 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 |
14 things needed for gas water heater & .pdf resources | |
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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