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Carolina Climate Control Blog

What Is “Flame Roll-Out” in a Furnace?


One of our biggest concerns as an HVAC company offering heating services to local homeowners is ensuring that natural gas furnaces operate safely throughout the year. If a gas furnace receives regular professional maintenance annually (and right now is a great time to schedule it!) it has the highest likelihood of presenting no safety concerns during its service life. 

Nothing is able to stop all safety worries with a gas furnace and you might also have a furnace that is aging or which hasn’t received the routine maintenance it needs. In this post we want to caution you about a furnace safety issue that might occur, one which people aren’t often aware of: flame roll-out.

What Is Flame Roll-Out?

When people think about potential danger from a gas furnace, they think of carbon monoxide poisoning first. Flame roll-out is an entirely different type of furnace hazard and can occur as frequently in an aging or deteriorating furnace as CO leaks. 

Simply put, flame roll-out is when flames escape from the combustion chamber of a furnace. During normal operation, the flames from the gas jets in a furnace are confined to the combustion chamber and their heat is drawn into the heat exchanger. 

The roll-out can occur for several reasons. Non-flammable gases can build up in the combustion chamber and stop oxygen from getting to the flames. This makes the flames work harder to get the oxygen they need for combustion, causing them to grow too big and escape the combustion chamber.

Another cause of flame roll-out is if the exhaust flue for the furnace is blocked, trapping combustion gases in the combustion chamber until they build up to the point where they will escape the chamber when they ignite. 

Why Flame Roll-Out Is Dangerous

The idea of fire getting outside of a furnace is scary all on its own. But flame roll-out presents several dangers. First, even if the flames don’t get out of the furnace itself, they will reach other parts of the furnace and severely damage them and even cause the furnace to catch fire.

The other concern is the flames igniting flammable material around the furnace. This is why we advise people to clear the area around their furnace for at least three feet and make sure flammable materials are kept far away. 

The Flame Roll-Out Switch

Fortunately, your furnace does have protection against flame roll-out: the flame roll-out switch. Without this switch, the furnace would present a much greater risk of roll-out occurring. The switch detects high heat levels outside the combustion chamber and shuts off the gas to the burners when this happens. The switch itself can malfunction, and this is when flame roll-out can become a serious concern. 

Preventing Flame Roll-Out

The best way to prevent flame roll-out is to have the furnace inspected each fall. Our technicians will check that the flame roll-out switch is operating, and we’ll also check the exhaust flue to ensure it’s venting properly. If you need any heater repair in Greenville, SC to keep your furnace working safely, we’ll inform you during maintenance so you can schedule the work promptly. Sometimes we can fix the issue on the spot.

Rely on the experts at Carolina Climate Control. The Moose Is Loose in Your Neighborhood!

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