How to Replace a Water Heater Thermocouple or Flame Sensor

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How to Replace a Water Heater Thermocouple or Flame Sensor

When you decide to run a bath or wash the dishes, you don’t have to boil water; you simply turn the faucet lever to the hot position. Your home’s water heater takes care of the rest, making sure you have a consistent supply of heated water. Although reliable, water heaters don’t function perfectly forever. 

Like all other plumbing fixtures and components, water heaters need maintenance and repairs in order to function optimally. When a water heater’s thermocouple or flame sensor breaks, the water heater is unable to heat water until the part is replaced. Keep reading to learn about thermocouples and flame sensors, their differences and how to replace them. 

Need the best water heater repair Midlothian, TX, has to offer? Dial One Johnson Plumbing, Cooling & Heating is your one-stop shop for plumbing maintenance, repair and installation. Call us at (972) 291-0740 to schedule service. 

Thermocouple or Flame Sensor?

If you’ve been troubleshooting water heater issues, you’ve probably encountered thermocouples and flame sensors. Despite having different names, both of these parts do basically the same thing: control gas flow in your water heater. 

Both thermocouples and flame sensors are part of the burner assembly and connect to the gas control valve on the outside of the water heater. They convert heat from a burning flame into a small electrical current which acts as a switch to control the gas flow. If the thermocouple or flame sensor doesn’t sense a flame, it does not allow gas to flow to the burner. 

When a thermocouple or flame sensor breaks, it isn’t able to sense a flame. As a result, it won’t allow gas to enter and heat the water. Before you attempt a DIY replacement, you need to figure out what type of ignition system your water heater uses.

Water Heater Ignition Systems

Your water heater’s ignition system will determine whether it uses a thermocouple or flame sensor. There are two types of ignition systems in water heaters: standing pilot and electronic. In both of these systems, the thermocouple or flame sensor is attached to the burner assembly. 

Standing Pilot 

Older water heaters tend to use a standing pilot ignition system, as well as a thermocouple. In this system, a gas line leads to a small burner, which creates a flame. The thermocouple, which is made from composite metal wire, connects the burner to a valve in the gas line. When the pilot light is on, the thermocouple senses heat and sends an electrical current down to open the gas valve. This keeps the pilot light burning. 

Electronic Ignition

Newer water heaters generally use an electric ignition system. An electronic ignition system uses a pilot, flame sensor and an electronic igniter to control gas flow. It utilizes solid-state controls to ignite and prove the flame. An electronic ignition system differs from a standing pilot system in that it only turns on when there is a call for heat. As a result, electronic ignition systems are generally more efficient. 

Not sure you want to install a new flame sensor on your own? That’s not a problem. When you’re ready for the best water heater repair, Midlothian, TX, has to offer, contact the plumbing experts at Dial One Johnson. 

How to Replace a Thermocouple 

If you’ve determined that your water heater uses a standing pilot ignition system, you’re ready to replace the thermocouple. Before you begin any of the steps, it’s critical that you disconnect the gas from the water heater. After you’ve turned the heater’s gas control valve off and closed the shutoff valve on the gas supply line that leads to the heater, follow these steps: 

  • Remove the burner assembly manifold cover. This cover protects the various components inside the combustion chamber, and it’s generally located near the bottom of the water heater. Remove the fasteners that secure the cover and set the cover aside.
  • Remove the burner assembly. Push down slightly on the burner supply tube to free the manifold, pilot tube and thermocouple connections. Gently lift the burner assembly from the combustion chamber and set it aside. 
  • Remove the cover plate gasket. Remove the old gasket from around the manifold cover plate. At this point, you can keep the gasket if it’s in good condition or buy a replacement. Next, clean the metal surfaces between the water heater and cover plate. 
  • Remove the thermocouple. Firmly pull and twist the broken thermocouple from its mounting bracket. Be careful not to bend the connection between the pilot and bracket. Pull the old thermocouple through the rubber grommet seal from inside to out, or through the opening in the manifold cover. If you’re struggling to remove the old thermocouple, you can also cut it out.
  • Install the new thermocouple. Insert the new thermocouple through the grommet or manifold cover opening and then into its mounting bracket. When it’s fully seated, it should click into place. Position the thermocouple so that the pilot flame will cover a little less than a half an inch of its tip. 
  • Reinstall the burner unit. Reinstall the old manifold cover gasket or a new one. Put the burner back in the combustion chamber and seal it. Finally, reinstall the cover and reconnect the gas. 

How to Replace a Flame Sensor 

If your water heater uses an electronic ignition system, you’re going to be replacing the flame sensor. As with the thermocouple installation, it’s critical to turn off the heater’s gas control valve and close the shutoff valve on the gas supply line before you begin. After the gas is off, follow these steps: 

  • Remove the burner assembly. Disconnect the pilot supply tube, burner supply tube and flame sensor from the gas control valve. Lift and remove the burner assembly from the bottom of the water heater. 
  • Remove the flame sensor. Pull and twist the old flame sensor from its bracket. It should come out easily with firm pressure. 
  • Install a new flame sensor. Insert the new flame sensor into the bracket and position it so that a little less than half an inch of its tip will be enveloped by the pilot flame. 
  • Reinstall the burner unit. Reinsert the burner in the combustion chamber and seal the unit. At this point, you can reconnect the gas control valve. 

Midlothian Plumbing Service

Water heaters account for about 18% of a home’s energy usage, according to the U.S. Department of Energy. If your water heater is outdated, it may be using even more energy. In that case, you may want to consider upgrading to a more energy-efficient model. Whether you’re in the market for a new water heater or the best water heater repair Midlothian, TX, has to offer, the plumbing experts at Dial One Johnson are here to help. Contact us online to schedule service or give us a call at (972) 291-0740.

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