OEM Lennox Flame Rollout Switch — 26H78

The genuine OEM Lennox 26H78 flame rollout switch is a critical safety limit that protects your gas furnace from dangerous flame rollout — a condition where flames escape the burner box due to blocked venting, a cracked heat exchanger, or restricted combustion air. When it senses excessive heat outside the burner area, the 26H78 instantly cuts power to the gas valve to prevent fire and equipment damage.

Common failure symptoms: A tripped or failed rollout switch will typically shut the furnace down with no heat, often locking out the control board. You may notice the furnace igniting briefly then stopping, a switch that won't reset, soot around the burners, or a failure code on the control board. Because it is a one-shot manual-reset safety device, a nuisance-tripped or worn switch must be replaced, not bypassed.

Why OEM matters: The 26H78 is set to the precise trip temperature and physical dimensions Lennox specifies for your furnace model. A generic switch with the wrong temperature rating can fail to protect against a genuine hazard or nuisance-trip repeatedly. Installing the factory OEM switch preserves the safety certification and dependable operation Lennox engineered into your equipment. Never bypass this safety device.