8 Symptoms of A Cracked Heat Exchanger

If you have a cracked heat exchanger, it’s important to know the symptoms and what to do about it. A cracked heat exchanger can cause your furnace or boiler to work harder than necessary, which leads to increased energy costs and even damage to your unit.

Even worse, a cracked heat exchanger can be a safety hazard. For instance, if natural gas is leaking from the heat exchanger, it can create a fire or explosion hazard. It can also potentially cause carbon monoxide leakage and build-up, which can be quite dangerous.

Therefore, it’s important to be able to tell when your heat exchanger has been damaged. We’ll cover 8 symptoms of a cracked heat exchanger to watch out for. But first, let’s go over how heat exchangers work in the first place.

Heat Exchanger Overview

First, it is essential to understand what a heat exchanger entails. In every gas furnace, there must be one heat exchanger. It contains metal coils found in the furnace warmed by the hot gas from the combustion process. Its main function is to move the heat from the flue gas or exhaust fumes into your home.

Generally, depending on your type of furnace, you can have one or two heat exchangers. You’ll only have one heat exchanger for standard furnaces, known as the primary heat exchanger. This one helps to transfer up to 80% of the heat to your indoor air.

However, high-efficiency furnaces will contain two heat exchangers. The primary one and a secondary one. The primary heat exchanger still transfers around 80% of heat, while the secondary exchanger transfers around 12-18% additional heat.

The furnace will release the flue gas generated during operation safely into the outdoors. But with a cracked heat exchanger, these gases can leak through the cracks into your home, which can be quite hazardous.

To ensure you’re aware of when this occurs, let’s determine how you can identify the signs of a cracked heat exchanger and know when you need to call for a heating repair service.

Top Cracked Heat Exchanger Symptoms

Here are some of the most common things to look for if you suspect a cracked heat exchanger:

  1. Change in the Color of the Furnace Flame

A furnace flame is usually blue. If your furnace flame maintains this color, it shows that the heat exchanger is operating perfectly.

However, if the furnace flame changes to yellow, it could be a warning sign. It either means a cracked heat exchanger or that your burner has debris affecting its efficiency.

If the color of the flame is yellow and flickering, there are likely more issues with the furnace. If you notice such color changes, contact a professional to assess the problem and prevent more damage to the system.

  1. CO Detector Going Off

As we’ve already seen, carbon monoxide leakage can result from a cracked heat exchanger, which can cause your CO detector alarm to go off as it notices higher carbon monoxide levels than usual in your indoor air.

If this happens, the first step is to evacuate the house. Then, call a technician to come to assess the situation. The technician will let you know when it’s safe to reenter your house once they have solved the CO problem.

For this reason, it’s also important to ensure that your CO detector is always functional. It will certainly come in handy in detecting these kinds of problems in advance.

  1. Unpleasant Smell from your System

Another symptom of a cracked heat exchanger in a furnace is an unpleasant smell. If your system is producing strong and irritating smells, then there is a possibility that your heat exchanger is cracked. The fumes are usually formaldehyde compounds and similar substances that can be dangerous when inhaled.

For this reason, never ignore strange smells from your furnace. Instead, you should take immediate action and contact an HVAC professional.

  1. Loud Sounds

A cracked heat exchanger can produce different sounds, including popping, banging, whistling, or scraping. You’ll notice the sounds emanating from the furnace cabinet.

Most of these sounds usually indicate an issue with the physical structure of the furnace parts. Some you can troubleshoot on your own while others require professional assistance.

The best course of action is to call an expert to examine your unit if you hear some of the above-mentioned sounds so they can safely fix the problem.

  1. Physical Symptoms within Household Members 

A cracked heat exchanger can result in gases leaking into your home, such as Sulfur and nitrous dioxide, which are dangerous to your health.

These substances may cause physical symptoms to develop within household members. Some conditions to look out for include insomnia, eye and nose irritation, headaches, and nausea.

Thankfully, most of the severe negative effects of dangerous gases only happen when you spend an extended amount of time in close proximity to the furnace itself. If you suspect that your furnace is damaged, it is advisable to stay away from the area and  book a service appointment immediately.

  1. A Lot of Soot Production from your Furnace

Whenever burning through carbon compounds in your heating unit, the furnace might generate a small amount of soot. However, a faulty heat exchanger causes inefficiencies that lead to the gas only burning partially. This results in incomplete combustion and creates a lot of soot as a byproduct.

The use of faulty burners is a potential reason why the fuel only burns partially. Of course, a cracked heat exchanger is also another reason for soot production in your furnace. You can easily prevent this issue by regularly doing furnace maintenance, around thrice every year.

  1. Visible Damage

If you inspect the furnace, you might see the cracks in the exchanger. Cracks are usually a result of metal wear and tear because of constant contraction and expansion. There may also be corrosion caused by water from the chloride-containing fumes or combustion byproducts.

The best way to address this is to conduct regular maintenance and parts replacement on your furnace performed by a professional.

  1. Water on the Floor

If moisture has buildup on the floor at the foundation of your furnace, then the most probable cause is a cracked heat exchanger. While leaking water is common in high-efficiency furnaces due to the condensation process, it’s rare in standard-efficiency ones.

Therefore, if you have a standard-efficiency heat exchanger and notice water leaks, examine your heat exchanger and determine the source. Once you’ve outlined this, contacting a professional HVAC technician is the ideal course of action.

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