What Is a Heat Exchanger and Why Is It Important?

What Is a Heat Exchanger in a Furnace?

The heat exchanger, also known as a fire box or “chamber,” is made up of coiled tubes (though not “coils”) which contain the hot combustion gases. When the blower kicks on and cool air flows over the gas-to-air heat exchanger, the air gets warmer without having to come into contact with dangerous gases.

The heated air then rises into the plenum. This is a sheet-metal box that is connected to supply ducts. From there, air gets distributed throughout the home

The combustion gases involved in this process, after giving off their heat, get passed through the flue pipe and safely exit the house, usually through the chimney.

Learn more about how forced air furnaces work.

The Importance of Heat Exchangers

Since heat exchangers hold dangerous combustion gases, any cracks, splinters, or holes are extremely dangerous because they may end up in your living spaces.

Combustion spillage can happen whenever fuel is burned. While the quantities are usually small, the toxic compounds can cause major health problems, and even death.

Harmful substances released when burning fossil fuels include:

  • Carbon Monoxide
  • Carbon Dioxide
  • Sulfur
  • Nitrogen Dioxide
  • Nitric Oxide
  • Volatile Organic Compounds
  • Hydrocarbons

Source: e-Education Institute

The amount of combustion gases created depends on a variety of factors, but heating equipment is usually designed to safely remove all of the combustion gases from the home.

With a properly working heat exchanger and ventilation system, none of the combustion gases should ever make it into the circulating air.

Unfortunately, combustion leakage can occur, and you may not even notice since many combustion gases are odorless and colorless, such as carbon monoxide (“the silent killer”).

How Things Can Go Wrong

The top three reasons why combustion gases leak into the home are:

  1. Chimney or vent problems
  2. Equipment failure (i.e., cracked heat exchanger)
  3. Pressure problems (i.e., backdraft due to negative pressure)

Without regular professional maintenance, mechanical problems can occur and prevent gases from escaping properly.

We highly recommend signing up for an annual maintenance plan for your household combustion appliances. Your service technician will check the heat exchanger, ventilation system, and any evidence of incomplete combustion of the fuel.

Cracked Heat Exchangers

Usually, the main cause of heat exchangers is a lack of professional maintenance. When dirt and dust accumulate on filters, blowers, coils, and heat exchangers, it becomes much more difficult for air to pass through and get heated.

If there isn’t enough airflow or if the heat exchanger has developed a layer of dust and dirt, the heat exchanger could possibly overheat and cause cracks and splinters to develop.

Another reason why heat exchangers may develop cracks is due to excessive gas pressure. Sometimes, the valves that control the pressure wear down, changing the amount of pressure

How to Stay Safe from Cracked Heat Exchangers

Unless you are a professional HVAC technician, it can be near impossible to tell if you have a cracked heat exchanger.

The best indication of a heat exchanger problem is with a carbon monoxide detector. If the detector continues to go off, don’t ignore it!

Turn all fuel-burning appliances off and call your local HVAC contractor ASAP to take a look before turning the heat system back on again.

In addition to scheduling annual furnace maintenance in the fall, make sure you are checking your air filter every 30 days and cleaning or replacing it when it gets dirty.

A clogged air filter can restrict airflow going over the heat exchanger, causing the heat exchanger to overheat.

What to Do If You Have a Cracked Heat Exchanger

The heat exchanger is a major system component. If you have a cracked heat exchanger, you need to replace it or replace the entire furnace. It can be difficult and expensive to find a matching heat exchanger for an older furnace.

Since fixing a cracked heat exchanger is a major repair, we recommend getting a second opinion to make sure there is in fact a crack in your heat exchanger.

If you suspect any problems with your furnace or heat exchanger, contact the experts at Service Champions to for exceptional service and care.

Service Champions is known for trustworthy, on-time heating and air conditioning service throughout the East Bay, South Bay, and Sacramento areas. Contact us today to schedule your custom indoor air quality solution.

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