Home Service Professionals

What Exactly Does A Heat Exchanger Do?

Have you ever been in a position where your furnace wasn’t producing enough heat? Like most homeowners, you have called a technician to diagnose the problem.

After waiting to find out what is wrong with your furnace, the technicians come back to inform you that the heat exchanger in your furnace is cracked and your furnace needs to be replaced.

Why would your furnace need to be replaced if the heat exchanger is cracked? Couldn’t it simply be repaired? What happens if a crack heat exchanger goes without attention? What exactly does this heat exchange do, how does it work when it is not damaged?

These are all common questions that are asked when a homeowner is given the news that a simple service call has turned into an expensive replacement.

What Does a Heat Exchanger Do?

What Does a Heat Exchanger Do?

So what exactly does a heat exchanger do? For starters, it is important to note that your HVAC equipment is not responsible for creating cool energy. Instead, the way that your HVAC systems work are by transferring heat (thermal energy) from one area to another. To put it more simply, that is exactly what a heat exchanger does: it moves thermal energy from one place to another. So when it is hot outside, your HVAC system and its heat exchanger are responsible for eliminating thermal energy from your home and placing it into your home during the cold seasons.

How Does a Heat Exchanger Work? How does a heat exchanger work?

When your furnace turns on, burners send hot combustible gases to your heat exchanger. From there, heat from the combustion gases gets transferred to the metal walls within the heat exchanger, which causes those metal walls to heat up.

Now that the walls are heated up, cold air from your house goes over those hot metal walls on the outside of the heat exchanger. This allows air from your home to heat up without picking up those dangerous combustible gases within the heat exchanger. Warm air is then distributed throughout your home using your ductwork.

However, those dangerous combustible gases need a place to go or vent to. With standard furnaces, those gases are blown out of the heat exchanger and vented outside of your home. If you have a high-efficiency furnace, those gases are cycled through a second heat exchanger, where even more heat is pulled from those gases and used to further heat your home.

What Does It Mean When Your Heat Exchanger Is Cracked? Can It Simply Be Repaired? 

Damaged heat exchanger

Cracks in a heat exchanger can’t be fixed long-term, and repeated short-term repairs can cost more than a new heating unit. The metal of the heat exchanger is generally too thin to weld shut and nearly impossible to access without removing it completely. Often even more cracks are found along the way to attempt the repair of the original.

What Happens if You Don't Fix the Cracked Heat Exchanger?

These gases contain the products of combustion. If they get into your air supply circulating through your house, gases like Carbon Monoxide can have dangerous health consequences. Heat exchanger cracks cause interior pressure changes, affecting how well the furnace burns. It is important to repair or replace your cracked heat exchanger as soon as possible, in order to prevent potential worse damages and costly repairs that could be avoided with professional help.

Poor combustion, when the furnace flame burns incompletely, produces higher carbon monoxide levels. Soot can block the venting of these lethal gases, sending it into the house, thus your family breathes them in. We’ve all heard the unfortunate news stories about family tragedy brought on by carbon monoxide exposure, especially in the winter heating season. The worst case of odorless, colorless carbon monoxide accumulation cause death. The main reasons carbon monoxide poisoning can happen are:

cracked heat exchanger

  • Inadequate or blocked gas vents
  • Heat exchanger problems
  • Incomplete combustion, resulting in high CO production
  • Lack of fresh, clean air and proper ventilation in the home
  • CO detectors missing or non-functional

Be sure you have working CO monitors/detectors, right outside each sleeping area. Don’t forget to install and maintain smoke alarms and radon detectors.

There you have it! Those are the basics of a heat exchanger and why they are so important to your heating system.

If you have been given a diagnosis of a cracked heat exchanger and would like a second opinion, feel free to give us a call at (360) 558-3242

Related: Why It’s Never Too Early or Late for Heating Maintenance

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