Modern furnaces have numerous safety features to ensure that failures don't put your house, your family, or the furnace itself in danger. These safeties typically rely on sensors (sometimes called switches) that prove safe operating conditions to the control board. For example, the draft pressure switch will prove that the draft inducer can pull exhaust gases from the combustion chamber.

The flame rollout switch is another critical safety feature. This switch detects when flames "roll out" to an area outside the burners. In most furnaces, a rollout condition will cause the furnace to shut down immediately, and you'll need to reset the switch to use your furnace. Keep reading to learn why you should never try to restore your heat by simply resetting this switch and turning the furnace on again.

Understanding Flame Rollout

Your furnace uses a gas burner manifold to direct combustion fuel and oxygen into the combustion chamber. This fuel passes over an igniter and creates a directed and contained flame. If you remove your furnace door, you should be able to see a steady blue flame from each burner port. Flickering, expanding, or red/orange flames can all indicate trouble.

Flame rollout typically occurs when the burners lack adequate fuel to burn cleanly. The flame will "seek out" more oxygen in these situations, allowing it to expand away from the burners. Unfortunately, flame rollout can often be less dramatic than many people expect. Instead of watching flames engulf your furnace's entire interior, you'll likely only see quick flickers as the fire consumes nearby oxygen.

Why You Can't Ignore Flame Rollouts

Despite the sometimes relatively mild appearance, flame rollout poses a substantial hazard. Combustion outside of the standard burner path can allow harmful exhaust gases to seep into your home. Rollout can also damage nearby components and wiring, leading to more damage and even costlier repairs. Your furnace's flame rollout switch exists to help prevent these problems.

However, it's crucial to understand that flame rollout is not a one-off situation. Rollouts can occur due to numerous issues, including clogged exhaust paths or even cracked heat exchangers. Anything that allows combustion gases to remain in the burn chamber will push out oxygen, forcing your flames to expand and seek more fuel.

Resetting your flame rollout switch may allow your furnace to turn back on briefly, but the problem will inevitably return. By resetting your switch without resolving the underlying issue, you can cause significant damage to your furnace and even allow dangerous gases into your home. If your furnace shuts down due to a rollout condition, it's critical to stop using it immediately.

In these cases, the best option is to contact an HVAC professional for a diagnosis and repair. Since rollouts may have many causes, you'll need an experienced furnace repair technician to find the underlying issue and ensure your furnace can operate without putting you in danger.

For more information on furnace repair, contact a professional near you.