How Does a Pilotless Gas Heater Work?

Pilotless Gas Heaters

• A gas heater system uses a device designed to light the furnace when temperature readings go below a preset level. Older heating systems use a standing pilot light that remains lit whether the furnace is running or not. Newer pilotless heater systems use an electronic igniter mechanism that lights the pilot when needed. Pilotless gas furnaces provide a more efficient method of gas heat compared to standing pilot systems, since the standing pilot must burn gas on a continual basis in order to maintain the flame. According to Preferred Home Repair & Services, pilotless gas heater systems meet or exceed the United States government’s 78 percent minimum annual fuel utilization rating for furnace efficiency.

Igniter Types

• Within a modern gas heater system, electronic ignitions come in one of two types, which include intermittent pilots and hot surface ignitions. Hot surface ignitions use a resistance heating element in much the same way that a light bulb sends electrical current through its filament material. When a room thermostat calls for heat, the hot surface ignition lights the pilot. A flame sensor mechanism then triggers the lighting of the main burner valve.
  Intermittent pilots use a high-voltage electrical spark to light the pilot when a room thermostat calls for heat. The main burner valve ignites once the flame sensor mechanism detects a lit pilot. Between the two types, the hot surface ignition system is the most commonly used due to its reliability and affordability of parts.

Types of Furnaces

• Pilotless gas ignitions work inside newer furnace models, which are designed to further improve upon gas burning efficiency levels. The two types of furnaces used with pilotless ignitions include the induced draft furnace and high-efficiency condensing furnace. Instead of relying on natural air flows, induced draft furnaces use a fan device to circulate air and gases into the furnace flue. This process produces an 80 to 82 percent AFUE furnace efficiency rating, according to Preferred Home Repair & Services.
  High-efficiency condensing furnaces use an additional heat exchange device to eliminate water vapor from flue gases and generate more heat within the combustion process. As a result, high-efficiency condensing furnaces carry a 90 percent or more AFUE efficiency rating.

Igniter Filaments

• The igniter filament found inside a pilotless gas ignition consists of either silicon carbide or silicon nitride materials. Both types of material generate the heat needed to produce a pilot flame. In general, filament materials only last for so long before they require replacement. On average, silicon carbide igniters last three to five years, while silicon nitride lasts nearly twice as long. When replacing igniter materials, furnaces that usually take carbide filaments can be upgraded to silicon nitride; however, the ignition control module will require upgrading, as well.