Thermocouples and Thermopiles

Shop replacement thermocouples and thermopiles for gas fireplaces. These two parts are often confused, but they solve different problems: a thermocouple keeps your pilot light lit, while a thermopile powers a wall switch or thermostat-controlled fireplace.

Thermocouples & Thermopiles

Both thermocouples and thermopiles sit in the pilot flame and convert heat into electrical power, but they serve different roles. A thermocouple generates a small signal, typically 20-30 millivolts, used only to hold the pilot's safety valve open. If it weakens or gets sooty, the pilot lights won't stay lit. A thermopile generates a much larger signal, typically 300-750 millivolts, strong enough to power the entire gas valve along with any wall switch or thermostat. If it fails, the pilot may stay lit but the main burner won't respond to your controls.

Replacing the thermopile or thermocouple fixes the two most common pilot-system failures: a pilot that won't stay lit (thermocouple) or a wall switch/thermostat that won't fire the burner (thermopile).

What to Consider When Buying

  • Identify which part you need before ordering: if your fireplace has a wall switch, remote, or thermostat, you likely need a thermopile; if it only has a pilot knob with no separate on/off control, you need a thermocouple.
  • Match the lead wire length and thread size to your existing part so it fits without modification.
  • Not sure which one you have? Check the model number on your existing part or measure its millivolt output with a multimeter.
  • If a new part doesn't resolve the issue, the pilot flame position or the gas valve itself may need attention.

Frequently Asked Questions

  • What's the difference between a thermocouple and a thermopile?

    A thermocouple produces a small millivolt signal, typically 20-30 millivolts, used only to hold the pilot's safety valve open. A thermopile produces a much higher output, usually 300-750 millivolts, strong enough to power the main gas valve and any wall-mounted switch or thermostat.

  • How do I know if I need a thermocouple or a thermopile?

    If your fireplace has a wall switch, remote, or thermostat that turns the flame on and off, it uses a thermopile. If it only has a pilot control knob with no separate on/off switch, it uses a thermocouple. Checking your existing part's model number or testing its millivolt output will confirm which one you have.

  • How do I install a replacement thermocouple or thermopile?

    Shut off the gas supply, disconnect the lead wire from the gas valve, and remove the old part from the pilot bracket. Install the new part so its tip sits directly in the pilot flame, reconnect the wiring, and test all connections with a soapy water solution for leaks before restoring service. If you're not comfortable working with gas connections, have a qualified technician handle the installation.