OEM Lennox Flame Rollout Switch — 78L29

The genuine OEM Lennox 78L29 flame rollout switch is a manual-reset safety limit that protects your Lennox furnace from dangerous flame rollout conditions. Mounted near the burner box, it constantly monitors for abnormal heat that occurs when flames escape the combustion chamber — typically due to a blocked heat exchanger, restricted flue, or failing draft inducer. When it senses an unsafe temperature, it immediately opens the circuit and shuts the furnace down to prevent damage and hazard.

Common failure symptoms: a furnace that repeatedly trips and won't restart until reset, no heat with a tripped rollout switch, short cycling on the burners, or a switch that stays open even after the cabinet has cooled. A switch that fails closed is even more concerning, since it removes a critical layer of safety protection.

Why OEM matters: the Lennox 78L29 is set to the precise trip temperature your furnace's safety design requires. Substituting a generic switch with a different rating can allow unsafe operation or cause nuisance shutdowns. Because this is a life-safety component, always install the factory-specified part to preserve proper protection and warranty coverage.