Definition
A hot surface igniter is a silicon carbide or silicon nitride element that glows hot enough to light the gas at a furnace's burners. During a heating call it heats for several seconds, then the gas valve opens and the burners ignite. Hot surface ignition replaced the standing pilot light on most residential gas furnaces built in recent decades.
Also called: HSI, Furnace igniter
Why it matters to you
Igniters are brittle and wear with every heating cycle, so in a heating-dominant climate where the furnace runs from fall through spring, a cracked igniter is a common no-heat problem on a cold morning. Silicon carbide igniters generally wear faster than silicon nitride types.
Practical guidance
If the furnace's inducer fan runs but the burners never light, turn the thermostat down and call for service; never touch an igniter, since skin oils and bumps can crack it. Igniter replacement means working in the burner compartment near the gas valve and is technician work.
About this definition
Written by the Home Energy Group team — a family-owned HVAC company celebrating 25 years of comfort & care across SW Washington and the Portland metro, licensed in Washington (WA LIC# HOMEEGI003J7) and Oregon (OR CCB# 184255). Definitions inform; an on-site diagnosis decides.
