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 a cracked igniter is a common no-heat problem on the first hard freeze or during a Kentucky cold snap, when the furnace is cycling most. Silicon carbide igniters generally wear faster than silicon nitride types.
Practical guidance.
First check the thermostat setting, the furnace power switch and the breaker; if the 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, and leave replacement near the gas valve to a technician.
About this definition
Written by the Feistritzer Heating & Air Conditioning team — family owned and operated in Danville since 1976, Kentucky HVAC license M02584. Definitions inform; a whole-system diagnosis in your home decides.