Most homeowners do not identify where their furnace secondary heat exchanger is until something goes off with the machine. When a furnace is in excellent working condition, ignoring this crucial device is simple. People often fail to recognize that the heat exchanger is a huge part of the furnace and must be well taken care of. 

Similar to other devices, after use and sometimes heat exchangers also wear out and can be damaged by a hole and crack formation. So, whenever you come across this issue, the outcome can be that the furnace generates partial fuel combustion. Further, it can also produce high levels of carbon monoxide, which is very harmful to health if CO enters your apartment—via poor emitting or leakage in the heat exchanger leading to severe illnesses or can also be fatal.

There are many varied kinds of HVAC furnace secondary heat exchanger. Their chief aim is to exchange heat securely and other crucial functions, comprising space heating, cooling and refrigerating, power stations, and other procedures. The article will serve all your necessities concerning heat exchangers. Read to the end to get a precise understanding of these furnaces. 

How Do Heat Exchanger Function?

Tubes, heat exchangers, and metal shells function by exchanging heat from one part. When furnaces burn propane fuel or natural gas, the by-products of combustion enter and move over the heat exchanger. The boiling flue gas warms up the metal as the vapor enters the exhaust making its way. While this is occurring, the heated metal warms the vapor circulating outside the heat exchanger.

Primary Heat Exchanger

This component comprises the warmest flue gas, which is very close to the gas rings in a furnace. Because of this, the flame and warmth create a lot of stress, which can lead to breakage and warmth stress with time. Also, the heat exchangers with 70% efficiency have a single heat exchanger.

Secondary Heat Exchanger

If you own a high-efficiency furnace, it comprises both secondary and primary heat exchangers. As combustion escapes the primary heat exchanger, it invades the secondary heat exchanger, where maximum warmth is freed from the gas, vapor begins to form. This alteration of the condition from water as a gas to a fluid removes latent warmth into the secondary heat exchanger, getting the furnace to improve efficiency levels. Because of this, these furnaces are also considered condensing furnaces. A furnace secondary heat exchanger is usually built from coated or stainless-steel material and sustains warmth, acid and moisture.

Signs Your Heat Exchanger is Damaged 

Every furnace depends on a heat exchanger to give heated air to the entire home. It is a crucial component of your warming system, and any problems can lead to the damage of your furnace and impose severe risks to your home and your health.

  1. Different smells 

A poorly functioning heat exchanger will usually make an unpleasant and pungent odor similar to that of formaldehyde. Thus, if you notice any foul smells, you must consider taking a service and make alterations accordingly. 

  1. Soot Formation 

Formation of white soot anywhere around the gas rings of a furnace. Any build-up is not a great sign and can get your furnace secondary heat exchanger clogged. Thus, the production of soot is not healthy for your device. 

  1. Damage & Leakage

If you locate damage or cracks in different parts of your furnace, especially the inducer motor, then instantly contact a service provider to solve the issue. Cracks are a very common issue that can signify issues in the furnace. 

  1. Variation in the flame 

In several furnaces, one can easily notice the warmth of the flame. Blue flames are normal; however, yellow is not. Any person can easily notice the flame change without close consideration. 

  1. Strange Sounds

If there is a breakage in your heat exchanger, you will most likely notice a rattling noise as the thermostat turns the warmth on. As the heat exchanger is created from metal, so as it gets warmed, these cracks also expand or contract and lead to banging or popping noises.

  1. Generation of Carbon Monoxide

CO is an odorless and tasteless explosive gas that is highly lethal. A poorly functioning or damaged heat exchanger can easily leak CO in residence. Only CO detectors and alarms can notice its presence; yet, you can not entirely depend on an alarm to identify failures. 

What Can Make Secondary Furnace Heat Exchangers Fail?

A random reason a heat exchanger can fail to work is if it is clogged or filthy. A filthy air filter blocks airflow via the furnace, warms up the heat exchanger extremely, and eventually causes cracks. 

Also, a furnace must be suitably sized for your residence. A large furnace can lead to overheating and force damage to the heat exchanger.

Yet, the most usual cause that leads to cracks is wear and tear. A furnace secondary heat exchanger is built using metal, go via continual expansion and contractions. Also, over time, this will easily cause the heat exchanger to crack. Most companies suggest a complete exchange and renewal of the burners after 20 years. Also, to extend the life of your furnace, ensure you take yearly services and inspections. Further, also change your filters once a year for perfect outcomes.

A damaged heat exchanger can impose a severe threat to your close ones. So, if you notice cracks in any cell of the heat exchanger, the harmful gases can leak into your home causes severe illnesses.


If you want your furnace to last long and give you desired outcomes, then serve it well. A faulty furnace secondary heat exchanger can cause severe impairment to your health and home. So, contact experts and solve these issues instantly. Using a bad furnace is unsafe for your residence. It can also be fatal and cause extensive damages. Also, there could be hidden issues that you might not notice and require expert assistance to identify. Thus, take regular services and keep your furnaces on track. 

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