An igniter is an electrically heated ceramic element that reaches 1,800-2,200°F to ignite natural gas or propane fuel in furnace burners at the beginning of each heating cycle. Modern ignition systems use hot-surface igniters instead of spark electrodes, providing more reliable ignition with fewer failed starts. Igniters are precision components that typically operate for 5,000-10,000 hours before degradation requires replacement.
Operating Sequence
The igniter energizes 15-30 seconds before the gas valve opens, allowing the element to reach full temperature and prevent delayed ignition. Current draw ranges from 3-8 amps at 24V AC or 120V AC depending on igniter type. Once burners ignite, the flame sensor detects heat and allows continued gas flow while the igniter remains energized throughout the heating cycle, then de-energizes during the cooling phase.
Failure and Maintenance
Igniter failure results in immediate furnace lockout after 2-3 failed ignition attempts, requiring service to restore operation. Common failure causes include thermal cycling stress, voltage fluctuations, or contamination from combustion byproducts. Failed igniters must be replaced with exact OEM parts matching voltage and amperage specifications. Annual inspection of igniter condition and electrical connections ensures reliable cold-weather furnace startup.