High efficiency furnaces utilize hot surface ignition and use ceramic ignitors. The furnace control module supplies power to the ignitor, which causes the ignitor to heat up. When the ignitor is glowing bright, the control module sends power to the gas valve. The gas is ignited by the heat of the ignitor. After the flame sensor senses heat, the control module turns the power off to the ignitor.
Ignitors are available in "flat" and "round" styles.
Flat Ignitors are classified by Mounting Block Types and Lead Wire Connection styles.