Should You Repair A Failing Furnace Heat Exchanger?

Posted on: 12 August 2021

Your furnace's heat exchanger sits comfortably out of sight, but it's perhaps the most critical element for heating your home safely. A gas furnace works by burning natural gas to produce heat, but the resulting combustion products contain incredibly toxic gases such as carbon monoxide. Your furnace uses a heat exchanger to extract heat while keeping the exhaust gases from entering your home.

Because it has a pivotal role in keeping you safe, you cannot operate a furnace with a failed heat exchanger. Cracks in the exchanger can allow combustion gases to escape and enter your home, posing a severe danger to you and your family. If your furnace is suffering from this issue, you'll need to either repair it or replace the entire furnace.

Why Do Heat Exchangers Fail?

It may seem strange, but overheating is one of the most common causes of heat exchanger failure. Although the entire purpose of this component is to extract heat, its materials still have an upper limit to what they can reasonably sustain. When operating normally, your blower also pushes heat away from the heat exchanger, keeping it relatively cool.

Unfortunately, your heat exchanger might develop cracks when anything interferes with this process. For example, leaving an extremely old filter in place can restrict airflow, ultimately allowing warm air to remain near the heat exchanger and cause it to overheat. For the same reasons, blower motor problems are another potential cause of heat exchanger failure.

While most modern furnaces will shut down when they overheat, it's still possible to cause damage by repeatedly allowing your furnace to run, overheat, and shut down. Some furnace manufacturers attempt to prevent this situation by requiring a reset if the unit shuts down several times over a short period.

What Are Your Options When a Heat Exchanger Fails?

Repairing a furnace with a bad heat exchanger requires a technician to open the main house, remove the old heat exchanger, and replace it with a new one. Heat exchanges are similar to air conditioning compressors in that they are the most critical and most costly component in your furnace. You can expect to pay anywhere from a few hundred to several thousand dollars for this repair.

When deciding if you should repair your heat exchanger, consider the age of your furnace, its overall condition, and any other necessary repairs. Modern furnaces can last several decades, so even an expensive heat exchanger repair is worthwhile on relatively new and well-maintained furnaces, especially if you expect it to give you at least another 5-10 years of service.

Remember that your furnace cannot operate safely with a cracked or otherwise damaged heat exchanger. Whether you decide to repair it or replace your whole furnace, you'll need to address the issue to keep your home warm this winter. Contact a local HVAC technician if you need more info on furnace repair.