| In order for a furnace to operate the flame must be | | | | electrons are flowing then the furnace knows the |
| proved. This means the furnace needs to know that | | | | flame is not there and it will close the gas valve to |
| there is a flame present and burning and if not then it | | | | protect against a dangerous gas build up. |
| has to shut off the gas supply so a build up of | | | | A very common problem that can make your |
| explosive gas does not occur. | | | | furnace stop working is a build up of silicon oxide on |
| Most newer furnaces use a technique called flame | | | | the flame sensor. Silicone oxide is produced when |
| rectification to determine this. This is accomplished | | | | small traces of common chemicals that are present in |
| with a simple device called a flame sensor. The | | | | the air burn with the gas in the burners. |
| sensor is a small stainless steel rod that is insulated | | | | Silicone oxide is almost invisible but it prevents the |
| with a ceramic insulator. | | | | electrons from leaving the flame sensor and the |
| A wire is attached to the sensor on the bottom. The | | | | furnace will think that there is no flame present even |
| sensor is positioned in front of the burner which is | | | | when there is a flame. The furnace will shut down |
| the furthest burner from the burner that has the | | | | leaving you with no heat. |
| ignitor. When the furnace turns on the ignitor glows | | | | To correct this problem first shut off the electric |
| red hot. Then the gas valve opens and allows gas to | | | | supply to the furnace. Remove the door to the |
| flow through the burners and ignites when the gas | | | | burner area and locate the flame sensor. Next |
| passes over the hot ignitor. | | | | remove the screw holding the sensor in place. Now |
| Next the furnace must quickly determine if the flame | | | | you can take the sensor out and clean it with a |
| is lit. A voltage is applied to the wire that is | | | | Scotch Brite pad. Replace the sensor and door and |
| connected to the flame sensor. If a flame is present, | | | | torn on the electric supply. |
| some electrons will flow through the sensor and | | | | Cleaning the flame sensor allows the furnace to |
| through the flame to the metal burners which are | | | | recognize a flame when it is present. |
| grounded. | | | | If other problems persist or you are uncomfortable |
| The flame will conduct the electricity because free | | | | working on a furnace then call, your local heating |
| electrons are produced in a burning flame. If no | | | | contractor. |