Most vented gas stoves, fireplaces, and fireplace inserts have a gas valve, a thermocouple, a thermopile, a piezo, and a pilot light. These parts are used to light and control the main burner.

     A piezo spark ignition is used to ignite the pilot after the gas knob is turned to the “pilot” position and depressed. Once lit, the pilot light heats up BOTH a thermocouple and a thermopile.

     The thermocouple is sometimes called a heat sensor or flame sensor. A thermocouple is a device made of two different metals which creates a small electrical charge (25 to 100 millivolts) when heated at one end by the gas pilot. A millivolt is 1/1000th of a volt. This small charge causes an electromagnet inside the gas valve to open and allow gas to flow to the pilot light. If the pilot light goes out and the thermocouple is no longer heated, it will shut down the gas flow to both the pilot and main burner. 

      Since the thermocouple must be heated in order to open the gas flow, fireplaces often have a startup mode, during which a pilot knob must be depressed and held for 30 seconds or so after lighting the pilot. At the end of the 30 seconds, the pilot should be generating enough heat so that the thermocouple is generating enough electricity for the gas to keep flowing to the pilot light. At this time, the startup knob can be released and the valve turned to an “on” position for appliance operation. Most fireplaces are designed to have a “standing” pilot light, which means it is always on –year round. Turning a pilot light on and off can shorten the lifespan of the thermocouple. A thermopile is a probe that contains multiple thermocouples; therefore it can produce a larger electrical current.

     The thermopile circuit causes a larger electromagnet inside the main gas valve to open and allow gas to flow to the main burner. This second circuit is also powerful enough (300-600 millivolts) to allow the use of a thermostat, wall switch or control switch to operate the main valve. Control of the valve is obtained simply by hooking a pair of wires (from the switch or remote control receiver) to two terminals located on the valve.

     Most vented gas stoves, fireplaces, and fireplace inserts have a gas valve, a thermocouple, a thermopile, a piezo, and a pilot light. These parts are used to light and control the main burner.

     A piezo spark ignition is used to ignite the pilot after the gas knob is turned to the “pilot” position and depressed. Once lit, the pilot light heats up BOTH a thermocouple and a thermopile.

     The thermocouple is sometimes called a heat sensor or flame sensor. A thermocouple is a device made of two different metals which creates a small electrical charge (25 to 100 millivolts) when heated at one end by the gas pilot. A millivolt is 1/1000th of a volt. This small charge causes an electromagnet inside the gas valve to open and allow gas to flow to the pilot light. If the pilot light goes out and the thermocouple is no longer heated, it will shut down the gas flow to both the pilot and main burner. 

      Since the thermocouple must be heated in order to open the gas flow, fireplaces often have a startup mode, during which a pilot knob must be depressed and held for 30 seconds or so after lighting the pilot. At the end of the 30 seconds, the pilot should be generating enough heat so that the thermocouple is generating enough electricity for the gas to keep flowing to the pilot light. At this time, the startup knob can be released and the valve turned to an “on” position for appliance operation. Most fireplaces are designed to have a “standing” pilot light, which means it is always on –year round. Turning a pilot light on and off can shorten the lifespan of the thermocouple. A thermopile is a probe that contains multiple thermocouples; therefore it can produce a larger electrical current.

     The thermopile circuit causes a larger electromagnet inside the main gas valve to open and allow gas to flow to the main burner. This second circuit is also powerful enough (300-600 millivolts) to allow the use of a thermostat, wall switch or control switch to operate the main valve. Control of the valve is obtained simply by hooking a pair of wires (from the switch or remote control receiver) to two terminals located on the valve.