Heat Exchangers: What You Need to Know

Colder temperatures have arrived – if you haven’t fired up your heating system yet, you will be soon! A furnace is made up of many critical components, one of which is a heat exchanger. Without it, you’d have no heat – learn function of a heat exchanger, how it works, issues, and how to maintain it!

What Is a Heat Exchanger?

The heat exchanger is the furnace component that heats air. It is a set of metal tubes or coils that connects to the burner assembly and ends at the vent or flue pipe. Air and gas are separated within the heat exchanger to prevent mixing and exposure to harmful combustion byproducts, such as carbon monoxide.

Your heating fuel (typically natural gas, oil, or propane, though electric furnaces use electricity to warm the heat exchanger) combusts within the heat exchanger, creating heat that warms its surface. The furnace’s blower motor forces air over the heat exchanger, causing the air to increase in temperature. Once air is warmed, it circulates through the ductwork into your home.

Common Issues with Heat Exchangers

If the heat exchanger malfunctions, your home may not achieve the desired temperature. Not only is furnace performance an issue, but heat exchanger malfunctions can pose serious health and fire risks.

Heat exchanger cracks are a serious furnace repair issue. If the heat exchanger is cracked, byproducts of the combustion process that takes place within the component can spill out. Cracked heat exchangers pose a risk of carbon monoxide poisoning – carbon monoxide is produced by combustion but is typically vented safely from the furnace out of the home, but if the heat exchanger is cracked, carbon monoxide can leak into the home.

Signs your heat exchanger may be cracked or damaged include:

  • Soot within your furnace
  • Rust on the heat exchanger
  • Visible cracks
  • Flickering or moving burner flames
  • Water surrounding the base of the furnace
  • Odors resembling formaldehyde
  • Symptoms of carbon monoxide exposure, including disorientation, nausea, and irritation of the nose or eyes

Cracks and damage to a heat exchanger can be diagnosed by an HVAC technician through a visual or camera diagnostic examination. Your HVAC technician will replace the heat exchanger so your furnace will function safely. Heat exchangers offer a typical service life between 10 to 20 years – depending on the life of your furnace and other factors, you may decide to replace the entire furnace if the heat exchanger requires replacement. Replacing the heat exchanger only comes with an average cost between $600 to $1200.

Care for Heat Exchangers

The performance and longevity of your heat exchanger can best be enhanced through annual furnace maintenance performed by a skilled HVAC technician. During your maintenance tune-up, the heat exchanger is inspected for cracks – if minor cracks are found, your technician can repair them to prevent further damage and safety threats.

During annual maintenance, your technician will also check for other issues that could lead to heat exchanger damage in the future. While normal wear and tear can lead to heat exchanger damage, airflow issues are often a cause of cracks and damage to the component. Closed or blocked vents inside the home and dirty air filters prevent restrict airflow in the heat exchanger, causing the component to overheat, leading to cracks. Identifying blocked vents and other blockages compromising airflow through the duct system can be resolved during a maintenance tune-up, and dirty air filters replaced to ensure air flows properly through your furnace.

  • Protect your heat exchanger by keeping your air filter Change your air filter according to the manufacturer’s specifications. Most air filters last between 3 to 6 months, though filters with low MERV ratings typically require replacement every month or so. You may need to change your furnace filter more frequently throughout the winter when heating system use is constant.
  • Always keep the vents in your home open. Keep supply and return vents clear of furniture, rugs, and other objects. Do not shut vents in attempt to save money on heating bills – doing so may cause airflow issues that create costly damage to the heat exchanger and other system components.