Flame Sensor

Flame Sensor:

Thermocouple and flame sensor picture

Difference Between a Thermocouple and a Flame Sensor

A thermocouple is used on a standing pilot furnace (with a pilot light). An electronic ignition furnace (intermittent pilot or hot surface ignition) uses a flame sensor. The flame sensor and thermocouple both perform similar functions in that they both control the flow of gas from the gas valve.

The flame sensing rod can be straight or “L” shaped. In both cases the thermocouple or flame sensing rod are generally part of a pilot burner assembly and both connect to the gas valve or to the electronic control box.

Flame Sensor Replacement

Replacement of a removable type flame sensor is a simple repair.

Shut off gas and power to the furnace. /li>
Remove the furnace's access cover.
If the furnace has been running, wait 30 minutes or so until the flame sensor cools.
The sensor may integral to the gas ignition system or independent and fastened to the burner assembly with a screw.
If your sensor is removable, first disconnect the electrical wire leads to the sensor. Disconnect the other end of the leads at the control box.
Next, remove the flame sensor by loosening the fastening screw(s) with a nut-driver or wrench.
Replace the flame sensor and fasten with the fastening nut, tightening with a nut-driver or wrench.
Connect the electrical leads to the sensor other end of the electrical leads to the electronic control box.
Replace furnace access cover.