Overview
The electronic ignition system in a gas furnace is a modern development that allows more reliable performance than standing pilot furnaces, provides energy savings and contributes to better furnace efficiency (AFUE). With a standing pilot, found most commonly on older low efficiency furnaces (55% to 65% AFUE is not uncommon), a small gas flame is always burning and is known in the lexicon of American home repair as a "pilot light". The problem with this type of "analog" ignition is that it wastes energy by constantly burning gas and can sometimes be unreliable.
These issues have led to the development of electronic ignition systems for mid to high efficiency furnaces that exceed the U.S. government’s established minimum AFUE rating of 78%. The electronic ignition occurs typically in one of two ways:
The intermittent pilot system uses an electronically controlled high voltage electrical spark to ignite the gas pilot and then subsequently the main burners, when the thermostat calls for heat.
The hot surface ignition system uses an electronically controlled resistance heating element not unlike a light bulb filament (and shown in the photo above), to ignite the gas burner.
It is important to understand some of the other components of a modern furnace that you will encounter depending on the type of high efficiency furnace you have. Why? Because they can also come into play in repairing an electronic ignition furnace when it won't run properly. Let's take a quick review of the types of furnace designs and components found in high efficiency furnaces using electronic ignition.
