Furnace Heat Exchangers: What They Are and How They Work

Your furnace has a heat exchanger inside it. It’s the most critical component in your furnace and is often referred to as its heart. But what is it and how does it work?

Furnace Heat Exchangers: What They Are and How They Work

What Is a Heat Exchanger?

A heat exchanger is a furnace component that’s made of metal shells and tubes. When your furnace turns on, gas is combusted to produce heat. The resulting flue gas enters the heat exchanger and warms it. The heat is transferred to the air passing over it, and that is then blown throughout your home by the furnace fan.

The heater exchanger separates flue gas from the warm air it produces. The flue gas is vented outdoors, as it’s dangerous to breathe.

Primary and Secondary Heat Exchangers

All gas furnaces have a primary heat exchanger. High-efficiency furnaces have a secondary heat exchanger as well. This allows them to extract more heat from the flue gas than just a primary heat exchanger can. High-efficiency furnaces are those rated as 90% efficiency or more.

Health Risks

Heat exchangers can become cracked and deteriorate. When this happens, flue gas can enter the warmed air that is blown into your home. The flue gas contains carbon monoxide and other dangerous combustion by-products.

Unless your carbon monoxide detectors are tripped, you likely won’t know the heat exchanger is cracked, although a cracked heat exchanger may also produce strange sounds. You should have your furnace tuned-up every fall. The technician will inspect the heat exchanger during the tune-up to see if it’s in good working order.

If the heat exchanger is cracked, you probably need a new furnace. It’s very costly to replace a heat exchanger, so it usually makes financial sense to upgrade the entire furnace rather than replace this part.

If your furnace’s heat exchanger has a problem and you’re a resident of Mount Airy or you live nearby, our team at J's HVAC Unlimited can help. We install, repair and tune up furnaces and air conditioners. Other services we offer include indoor air quality solutions, comfort zoning, mold removal, air duct cleaning and crawl space remediation. Call us today for any of your heating and cooling needs.