Dealing With a Faulty Heat Exchanger

The heat exchanger is the unsung hero of any furnace dependent on natural gas or heating oil. These complex series of tubes help gather heat from the furnace’s combustion chamber and transfer that heat to the air blown through your home’s ducts. Meanwhile, the heat exchanger safely funnels the spent gases out of the furnace and into the flue.

A heat exchanger failure can prove devastating for your home’s wintertime heating prospects. Not only can an unexpected failure rob your home of its heating capabilities but such failures can also prove dangerous. A cracked heat exchanger elevates your home’s risk of carbon monoxide poisoning, which could have serious consequences for your family’s health and safety.

Anatomy of Heat Exchanger Failure

Most heat exchanger failures involve stress cracks forming near bends, welds, and other thin, weak areas. Heat exchangers are also vulnerable to rust and corrosion. How these failures occur usually depends on the circumstances mentioned below.

Normal Wear and Tear

The life of a heat exchanger is not, by any means, easy. Every time you use your furnace, the thin metal walls of the heat exchanger have constant exposure to high temperatures. The metal subsequently undergoes constant expansion and contraction as the coil heats up and cools down after every run. The constant heating and cooling cycle can cause stress cracks to form throughout the furnace’s life cycle.

This constant cycle can take a toll on the heat exchanger’s longevity. The average lifespan of a heat exchanger is usually the same as the furnace itself. You can expect a typical furnace to last for 15 to 20 years, depending on its overall usage and maintenance history.

Limited Airflow

A clogged furnace filter or any other type of blockage can prevent air from circulating throughout the furnace properly. Without enough airflow to carry heat away, the heat exchanger overheats in excess of safe operating temperatures. Such overheating can cause premature metal fatigue and lead to stress cracks throughout the heat exchanger.

Poor Furnace Sizing

Whether your furnace is undersized or oversized for your home’s heating needs, a mismatch in heating needs can also lead to eventual heat exchanger failure. Oversized and undersized furnaces can overheat their heat exchangers through normal operation. Furnaces attached to undersized ductwork can suffer airflow problems that lead to heat exchanger damage.

Rust and Corrosion

Water vapor is one of the many byproducts of the combustion process. As the heat exchanger removes heat from passing combustion gases, the cooling effect causes the vapor to drop out of suspension.

The resulting condensate is acidic enough to eat away at metal surfaces, resulting in rust and corrosion formation. Secondary heat exchangers are especially prone to rust due to the amount of acidic condensate that forms during operation.

  • Yellow or flickering flames  A steady blue flame represents your furnace working at its most efficient state. A cracked heat exchanger can cause the burner to operate inefficiently, resulting in a yellow flame or a constantly flickering flame.
  • Visible rust and corrosion  The appearance of rust and corrosion often indicates a heat exchanger that’s on its last legs.
  • Excessive soot buildup  Incomplete combustion that a cracked heat exchanger causes can also encourage excessive soot buildup within the furnace.
  • Strange furnace odors  A damaged heat exchanger can also produce strong odors that are sometimes similar to formaldehyde.

A cracked heat exchanger can also allow dangerous combustion gases to leak inside your home. Carbon monoxide and other combustion gases can cause a variety of symptoms, including frequent headaches, nausea, eye irritation, and sleepiness.

Replacement Options

Your trusted HVAC professionals will thoroughly inspect your heat exchanger to determine the best course of action. If the furnace is relatively new and still under warranty, your HVAC technicians may replace the heat exchanger.

If your furnace is over 10 years old or is no longer covered under warranty, a complete furnace replacement makes more sense. With parts and labor factored in, the expense of a heat exchanger replacement may exceed the cost of installing a brand-new furnace.

If you currently have a faulty heat exchanger, let the experts at Advanced Heating & Cooling take care of it. Call us today to schedule an appointment or ask any questions you may have.


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