- gas valve
- heat exchanger
- ventilation system
Each part is pivotal in keeping you warm during cold weather. Because of their central roles, these parts also endure the most wear and are most prone to requiring repair or replacement.
In this discussion, we’ll focus on the heat exchanger. We’ll review what it is and why you should care about its condition in your heating system.
What Is a Heat Exchanger?
The Second Law of Thermodynamics establishes that heat flows from areas of high temperature to areas of low temperature. To do its seasonal work for us, an HVAC system reverses this natural flow by removing hot air from our homes in summer and placing it in our homes in winter.
The heat exchanger in a gas furnace is pivotal in this process in that it transfers thermal energy from one medium to another. Two main types of heat exchangers are condenser coils and evaporator coils, which both contribute to the heating and cooling of a home.
A thin sheet (wall) between the blower and the combustion chamber, the heat exchanger in the furnace is an airtight vessel with one hole at the bottom and one hole at the top, known as the flue. It delivers heated air into the home through the following process:
The burners create combustion gases and send them into the heat exchanger through the bottom hole.
While the burners are generating and sending the gases, a blower directs indoor air over the heat exchanger’s exterior.
The heat exchanger uses the combusting gases to warm the air as it blows along the heated walls.
The heated air is sent through the supply duct for distribution into the home.
Exhaust gases from the combustion (including sulfur dioxide and carbon monoxide) are released outside of the home through the flue.
As a result of this process, the heat exchanger achieves two vital functions:
Exchange heat to warm the home.
Separate toxic combustion gases from the heated air that enters the home.
As long as the heat exchanger is in good condition, you can enjoy comfort in warmed air that is safe to breathe because it is free of the spent combustion gases.
Heat Exchanger: When a Problem Can Start
The heating process causes the exchanger’s metal to expand. Once the cycle is completed, the hot metal cools and contracts back to its original size.
Over time, the repeated expansion and contraction of the metal strains it, and constant stress can force the heat exchanger to crack. A cracked exchanger will not form the vital seal between the toxic flue air and the air you breathe indoors. As the toxic exhaust mixes with the oxygen, it can lead to illness or even death.
Some signs of a cracked heat exchanger can include:
- weaker heating
- odd noises from the furnace
- white soot around the burner
- discolored metal
- strange or unpleasant (toxic) smells
- cracks and corrosion
- appearance of orange or yellow flame
- water at the base of the furnace
If you notice any of these symptoms of damage, contact Air Dynamics right away.
In addition, because a cracked heat exchanger can release dangerous carbon monoxide into your home, be sure you have a properly operating CO alarm or detector installed with sufficient battery life.
Heat Exchanger: Replacement Cost
Heat exchangers are typically designed to operate for as long as the furnace itself, which these days can average 12 to 15 years. However, as we’ve discussed, wear and tear can sometimes shorten their longevity. Other factors that can reduce an exchanger’s duration can be poor design, improper installation and a lack of furnace maintenance.
Replacing the heat exchanger can range from $1,500 to $3,000, making it one of the most expensive repairs. Should the part crack, the decision to replace it will often be determined by the age of the heating system.
If the system is more than 10 years old, in many cases it will make more financial sense to replace the entire furnace instead of just the heat exchanger. This can especially be true if the cracked exchanger involves other components, such as the blower.
If the heat exchanger is still under warranty, the manufacturer will often cover the part cost but not labor and disposal. Replacing a heat exchanger usually requires from 8 to 10 labor hours, so the charge will normally be at least $500.
Heat Exchanger: How You Can Help Prevent Damage
Although old age is a leading factor in whether a heat exchanger will crack, you can take useful steps to help prolong its function and life.
Checking and changing the air filter regularly is important for preventing airflow problems that can cause the part to overheat. Also be sure to keep all vents and registers open and clear to avoid overheating that damages the heat exchanger.
Set and monitor the thermostat so that it runs the furnace only when you need it as opposed to all day long. In addition, if you ever detect your furnace might be overheating for any reason, turn it off and call Air Dynamics.
Scheduling annual maintenance is important as well. A yearly inspection will identify and address any minor issues with the system and ensure that the coils and other vital parts are clean and operative. A little bit of maintenance really can lead to a lot of furnace life.
Contact Us Today
Air Dynamics helps you get the greatest performance and return from your furnace investment. We support homeowners in Oswego, Yorkville, Naperville, Aurora and Plainfield (IL) with the professional training, knowledge and equipment for heating systems that run better, longer and more safely. If you ever have questions or concerns about your heat exchanger, simply give us a call at (630) 731-1550!