If the pilot light won’t stay lit or keeps going out in your Bradford white water heater, it could indicate a problem with the thermopile. This guide will help you to:
- Test if the thermopile is functioning correctly.
- Clean and replace a faulty thermopile.
- Troubleshoot related issues, such as problems with the thermal cutoff switch.
Note: This guide applies to standing pilot water heaters with electronic gas valves. Some steps may vary for conventional gas valves.
Understanding Pilot and the Thermopile
Pilot water heaters operate with a continuously burning pilot flame. This flame is responsible for igniting the main burner whenever heat is required. Positioned next to the pilot flame is the thermopile, a critical component that:
- Generates Voltage: The thermopile creates a small electrical current when heated by the pilot flame. Though it produces less voltage than a standard AA battery, it’s enough to power the electronic gas valve and diagnostics.
- Acts as a Safety Switch: If the pilot light goes out, the thermopile cools, causing the voltage to drop. This prompts the gas valve to shut off, preventing unburnt gas from being released into your home.
When the thermopile becomes faulty, the pilot light may struggle to stay lit. This issue needs prompt attention to restore proper functionality.
Tools and Safety Precautions
Tools Required:
- Adjustable wrench
- Screwdriver
- Nut driver
- Multimeter (capable of measuring millivolts)
- Dish soap
- Small brush
- Emery cloth (for cleaning)
Safety Precautions:
- Always turn off the gas supply before starting. The gas valve handle should be perpendicular to the pipe.
- If you smell a strong gas odor, immediately shut off the gas, ventilate the area, and call a technician.
- Allow the burner and pilot area to cool down before handling any components.
Testing Thermopile
Remove the bottom access cover of the water heater to expose resettable thermal switch terminal.
While keeping the pilot ON to keep the flame on, disconnect the red (+ve) wire from the resettable thermal switch.
Set the multimeter to DC millivolts mode. Set a multimeter to measure millivolts and connect the positive probe to the terminal of the resettable thermal switch. Attach the negative probe to an earth ground point, such as the jacket base or a screw. A properly functioning thermopile should generate a voltage reading between 350mV and 850mV.
If the voltage is less than 350, there should be a problem with the Thermopile. Sometimes due to the long time usage carbon builds up on the thermopile causing it to produce low voltage. We need to take it out and clean it with emery cloth and test again it voltage doesn’t comes up replace it with a new Thermopile.
Replacing the Thermopile
A. Disassembly
- Turn Off Gas Supply:
- Turn off the main Gas supply valve and Set the control valve to the “OFF” position.
- Remove Burner Assembly:
- Disconnect the ignitor wire and the wires leading to the control valve and thermal switch.
- Remove two 1/4” hex drive screws from the right side inner door, two 1/4” hex drive screws from the flange section of the inner door, and two 1/4” hex drive screws from the left side inner door.
- Disconnect the thermocouple/thermopile, pilot tube, and feedline from the gas control/gas valve with the help of Adjustable Wrench. NOTE: The feedline nut for natural gas control uses right-hand threads; Propane gas control uses left-hand threads.
- Disconnect the piezo ignition wire from the piezo igniter.
- Remove the burner assembly from the combustion chamber.
- Access the old Thermopile:
- Look the burner assembly and locate the thermopile. Check how its connected if there are any screws remove them.
- To remove it inspect the pilot assembly from the top and press the thermopile towards the right while gently pulling to remove.
- Remove the thermopile from its housing. Check for carbon deposits on it, if present clean it and check by connecting back. It is recommended to replace with a new Thermopile for better working for long time.
B. Replacing a new Thermopile
- Insert New Thermopile:
- Slide the new thermopile into place and secure it with the retaining clip. You might have to wiggle it, ensuring it is pushed in all the way.
- Reinstall the burner assembly, ensuring all components are in their original positions. Reconnect the pilot tubing, gas feeder line and igniter wire, tightening them by hand first to avoid stripping threads.
- Reinstall inner door:
- Fix the inner door in place and fix all the 1/4” hex drive screws which we removed in their places. Fix it with care as it has a gasket which we should not damage it.
- Reconnect Wires:
- Attach the wires to the control valve and thermal switch. Reconnect the ignitor wire.
If your water heater has thermocouple refer this guide: Bradford white water heater Thermocouple replacement.
Final Steps and Testing
- Relight Pilot:
- Turn on the gas supply and relight the pilot.
- Set the control valve to the desired temperature.
- Check for Gas Leaks:
- Apply a soapy water solution to all connections. Look for growing bubbles, which indicate a leak. If detected, turn off the gas and retighten connections.
- Observe Burner Operation:
- Ensure the main burner ignites and functions properly.
Troubleshooting Other Issues
- Thermal Cutoff Switch: If the thermopile is functioning but the pilot still won’t stay lit, test the thermal cutoff switch. Replace it if necessary.
- Gas Control Valve: Persistent issues may point to a faulty gas control valve, which should be inspected and replaced by a professional if needed.
Find Bradford White water heater Age by Serial number
Conclusion
By following these steps, you can restore the functionality of your water heater’s thermopile and ensure safe, efficient operation. For more detailed troubleshooting or additional repairs, consult a technician or refer to the manufacturer’s guide.
