Flame rod BR 80L L35

Flame rods operate on the rectification principle. Flames contain ions capable of conducting electrical current. An AC voltage on the flame rod will conduct current through the flame to a grounding surface, usually the metal parts of the burner. The signal will be rectified to DC with a 4:1 ratio of surface areas of the burner ground and flame rod that are in contact with the flame.

On receipt of the DC signal, the controller will send power to keep the automatic fuel shutoff valves open. If the flame rod shorts to ground, then the DC signal is lost and the resulting AC signal is rejected by the controller and the shutoff valves are closed. Because of this action, flame rods with appropriate flame safeguard controllers are considered fail safe.

Unless the burner manufacturer’s literature states otherwise, use flame rods only on gas burners, not oil burners. The rods may accumulate soot, or oil film, causing nuisance shutdowns. Flame rods will work properly only if you maintain a predetermined ratio of rod surface area to burner grounding area in contact with the flame. Consequently, observe the flame rod length recommendations published for various burners.