Lennox Furnace Error Code 8

Error code 8 on a Lennox furnace means a rollout switch has opened and shut the furnace down. The rollout switch is a safety device that trips when it detects heat or flames outside of the normal burner compartment area. This condition typically points to a blocked flue, restricted heat exchanger, or inadequate combustion air. The furnace will not operate again until the root cause is fixed and the switch is manually reset.

Yes, the condition that triggers error code 8 can be dangerous. Flame rollout means combustion is occurring outside its intended containment area, which is a fire risk and can also indicate that combustion gases including carbon monoxide may be escaping into the living space. The furnace correctly shut itself down as a protective measure. Do not attempt to bypass the rollout switch or force the furnace to operate until the cause has been identified and corrected.

No, a simple power cycle will not clear error code 8 on a Lennox furnace. The rollout switch is a mechanical safety device that physically opens a circuit and must be manually reset by pressing its reset button directly on the switch. Even after a manual reset, the furnace will trip again if the underlying problem such as a blocked flue, restricted heat exchanger, or inadequate combustion air has not been corrected first.

The rollout switch does have a manual reset button that you can press, but resetting it without finding and fixing the underlying cause is not safe and will likely result in another trip shortly after. The switch opened for a reason, and continuing to reset it without inspection can mask a serious problem such as a cracked heat exchanger or blocked flue. It is strongly recommended to have a qualified technician diagnose the cause before resetting the switch and restarting the furnace.

Repair costs depend entirely on the root cause. If the issue is a blocked flue or combustion air problem, costs may be limited to a service call fee in the range of $80 to $200. If the heat exchanger is cracked and needs replacement, costs can range from $500 to $1,500 or more depending on the part and labor involved. A full diagnostic visit is necessary to determine the actual scope of the repair before estimating costs.