Understand the Causes Flame Rollouts in Gas Furnaces

Understand the Causes Flame Rollouts in Gas FurnacesThe sight of flame rollouts in your gas furnace may be alarming—and it should be. Flames exuding from your burner and combustion chamber is a fire hazard, presenting a definite danger to your furnace components. In normal operation, all burner flame action should be restricted to the combustion chamber and should appear as a clean, blue flame emitted by the burner jets.  

How Does It Happen?

Flame rollouts in gas furnaces and boilers are caused by a high concentration of combustion gases inside the combustion chamber. Normally, these inflammable gases are exhausted from the furnace through the flue passageways in the heat exchanger, then up the vent to the exterior of the home. These narrow conduits in the heat exchanger may become restricted with age—usually due to soot buildup and flakes of rust or corrosion—decreasing their effectiveness to convey combustion gases out of the combustion chamber.

What are the Signs?

Because combustion gases are non-flammable, a high concentration inside the combustion chamber can inhibit proper ignition of natural gas at the burner. Unburned gas may project as far as the opening to the combustion chamber before adequate oxygen is available for ignition. In this case, the burner flame may “roll out” of the combustion chamber.

What are the Dangers?

Furnace components located outside the combustion area are not designed to withstand contact to an open flame. Wiring, switches and the gas valve itself can be damaged from exposure to heat and flame. In some cases, flame rollout may result from a hole or crack in the heat exchanger—a hazardous condition that may allow dangerous carbon monoxide gas to infiltrate your home. For these reasons, many gas furnaces and boilers come with flame sensors that can shut down your furnace automatically.

How Is Flame Rollout Prevented?

As part of a regular annual furnace checkup, you HVAC technician will inspect the condition of your heat exchanger and look for any soot and corrosion, as well as dangerous cracks and holes.

For professional help to resolve hazardous flame rollouts in gas furnaces, please contact Hartman Brothers Heating & Air Conditioning, Inc. in New Haven today.

Our goal is to help educate our customers in New Haven, Indiana and surrounding Fort Wayne area about energy and home comfort issues (specific to HVAC systems). For more information about furnaces and other HVAC topics, download our free Home Comfort Resource guide.

Credit/Copyright Attribution: “lculig/Shutterstock”


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    Richard Hartman Richard Hartman has worked in many capacities: service, installations, and production of sheet metal since the early years of the business.... More »