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Carolina Climate Control Blog

How Your Furnace Is Able to Operate Safely


Gas furnaces … are they safe?

The answer is yes. They’re safe the way that the gas oven and stove in your house is safe. If you use your furnace right and make sure it’s taken care of, then it’s safe.

That doesn’t mean it can’t be hazardous, and this is one of the reasons that we always urge our customers to arrange for annual furnace inspections and maintenance and for prompt furnace repair in Summerville, SC when anything appears to be wrong. 

In this post, we’re going to look at how your gas furnace is able to run safely through the winter. The manufacturers of furnaces build them to high standards and equip them with several important safety features. Let’s examine the most important of these features.

The Flame Roll-Out Switch

Flame roll-out is when flames inside the furnace’s combustion chamber escape from the chamber. Flame roll-out can not only damage other parts of the furnace, it can set objects on fire around the furnace. (This is one of the reasons we recommend people keep a clear space of about a foot around the furnace.)

The flame roll-out switch detects when this happens—usually because the flames lack oxygen and are leaping to the nearest source—and shuts off the burners when it does.

The Flame Sensor

When a furnace starts up, natural gas begins to flow to the burners where the electronic ignition system ignites them. If this ignition doesn’t occur, unburned gas will flood the chamber and create the danger of an explosion.

To prevent this, a device called the flame sensor monitors if the burners have lit. If it doesn’t detect the flames, it will shut off the gas to the burners. 

The Limit Switch

This device prevents the furnace from overheating by registering the temperature around the combustion chamber and the heat exchanger. It’s located on the plenum and will shut off the furnace if the temperature rises too high. This may happen because the heat exchanger isn’t cooling down because of trouble with the blower fan.

The limit switch is also responsible for monitoring when to turn the blower fan on, so it’s not just a safety device but an important part of the furnace’s heating cycle.

The Draft Pressure Switch

For a furnace to operate safely, it must vent out the leftover combustion gas from the heat exchanger through a flue to the outside of the house. A draft inducer fan helps to push out these toxic gases.

However, a change in pressure or a failed fan could cause gas to move in the wrong direction and flow back into the furnace and therefore the house. The draft pressure switch detects this reversal of pressure and shuts down the furnace to stop it.

Carbon Monoxide Detectors

These aren’t parts of your furnace—but we want to make sure to mention them because they’re an important defense in your house against an indoor build-up of carbon monoxide (CO) from your furnace or any other gas-using appliance. 

Rely on Carolina Climate Control for fast and accurate furnace repair. The Moose Is Loose in Your Neighborhood! 

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