Can a cracked heat exchanger cause a fire?

Author: Fabiola Wyman  |  Last update: Wednesday, July 30, 2025

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.

Is a cracked heat exchanger a fire hazard?

A crack in the heat exchanger means combustion byproducts could escape and mix with the air supply that circulates throughout the home. Carbon monoxide is one byproduct of combustion, and exposure to this gas can be deadly. Another danger associated with a cracked heat exchanger is the possibility of a furnace fire.

What happens if a heat exchanger is cracked?

A crack in these tubes and coils can lead to the gases being burned in the furnace, such as carbon monoxide, sulfur dioxide, and nitrous oxide, leaking into your home. These dangerous gases can cause illness, or in extreme cases, death.

Can a heat exchanger catch fire?

In extreme cases, a cracked heat exchanger can become a fire hazard. If the crack is large enough and allows hot combustion gases to escape, they can come into contact with flammable materials within the furnace or ductwork. This can lead to a fire that poses a significant risk to your home and safety.

How long can you run a furnace with a cracked heat exchanger?

So, can you run a furnace with a cracked heat exchanger? The straightforward answer is no. Operating a furnace under these conditions is unsafe and can lead to severe consequences, including the risk of carbon monoxide poisoning.

Watching A Furnace Run With A Cracked Heat Exchanger

How much does it cost to fix a cracked furnace heat exchanger?

It can range between $1,000-$4,000 for parts and labor, with an average cost of $2,000. Learn how this heat exchanger cost breaks down and how to identify the crucial signs it's cracked and needs replacement.

Is it better to replace a heat exchanger or a new furnace?

Furnaces have an average lifespan of around 10 years, and most exchangers tend to go out around this time. If your furnace is close to this 10-year mark, a new furnace is likely a better investment. If your furnace is relatively new, a new heat exchanger may be worth it to avoid early furnace replacement.

What do flames look like with a cracked heat exchanger?

Changes In How The Flame Looks

In a normal gas furnace, the flame will usually appear blue. A blue flame means that your furnace is working as it should. If this flame turns yellow, however, it might mean that your burner needs to be cleaned, or worse, that the heat exchanger is cracked.

What causes a furnace to catch fire?

Inadequate Gas Pressure

It also causes unwanted condensation within the heat exchanger, increasing the rate of corrosion. Conversely, high gas pressure can produce excessive heat in the furnace, which can cause the soot inside the heat exchanger to combust. Such fires can readily spread to other areas.

Can a cracked heat exchanger cause flame rollout?

A cracked heat exchanger allows air from the furnace blower to interfere with the flame causing it to turn yellow, flutter, or even roll out of the combustion chamber. Flame rollout will trip a safety switch and shut down the gas furnace.

What is a major indicator of a cracked heat exchanger?

If you notice strange smells, like formaldehyde or any other strong chemical smell, it strongly indicates that your heat exchanger is cracked. It also means dangerous gasses, like carbon monoxide, are leaking into your home. You should immediately evacuate and call 911.

What are the four causes of a cracked heat exchanger?

The metal surface of the heat exchanger is subjected to years of temperature extremes combined with expansion and contraction from multiple heating seasons. Another potential cause of cracking is limited air flow. Blocked registers, dirty filters, and ductwork obstructions can cause pressure to build up in the furnace.

Can you smell a cracked heat exchanger?

Soot can collect when combustion is incomplete. This can be caused by burners that are improperly adjusted or a cracked heat exchanger. A faulty heat exchanger will produce a strong and unpleasant odor that smells similar to formaldehyde.

What happens if your heat exchanger is cracked?

What if Your Have Cracked Heat Exchanger? When you're told that your heat exchanger is cracked, exhaust gases can leak into the air instead of entirely into the flue pipe. The most hazardous of these gases is Carbon Monoxide. For this reason it is a must for you to have a carbon monoxide detector in your home.

Are heaters a fire hazard?

Portable electric heaters are high-wattage appliances that have the potential to ignite nearby combustible materials like curtains, beds, sofas, paper, clothing, and flammable liquids. If ignition results from a heater left on and unattended, a major fire could result. damaged.

Can I replace a heat exchanger myself?

And remember, trying to replace a heat exchanger without professional assistance can pose potential hazards such as carbon monoxide poisoning and other safety risks.

Is it normal to see fire in your furnace?

Worn-out or frayed wires can create short circuits, leading to sparks or even fires. Another potential risk is a malfunctioning ignition system. If the ignition system fails, it may cause gas to build up in the furnace before igniting, resulting in a dangerous explosion or fire.

What can cause a furnace to explode?

A furnace explosion is usually the result of ignition and instantaneous combustion of highly flammable gas, vapor, or dust that has accumulated in a boiler. The effect of the force from the explosion is often much greater than the boiler combustion chamber can withstand.

Why would a furnace fail to ignite?

Issues with the gas line, like a clog, can also lead to an instant furnace ignition failure. That problem is simple since any obstruction in the gas valve or gas supply will prevent enough natural gas from reaching the ignition. That means the system won't trigger the combustion process or generate heat.

What action should be taken if a cracked heat exchanger is found in a residential home?

Typically, you will need to switch out the damaged heat exchanger or replace the entire unit. The technician can give you a run-down of your options.

How much does it cost to replace a cracked heat exchanger?

Were you recently told that your furnace heat exchanger is cracked and needs to be replaced? If so, here's the thing: replacing a heat exchanger isn't as simple or affordable as it sounds. In fact, replacing a furnace heat exchanger can take up to 8 hours and can cost anywhere from $3,000 to $5,000.

Should I replace the heat exchanger or buy a new furnace?

Replacing the Heat Exchanger & Repairing Your Furnace

If your furnace is less than ten years old and the rest of the components are in good condition, it will likely be worth just replacing the heat exchanger component. An HVAC technician can replace the damaged heat exchanger and install a new one.

How many hours does it take to replace a heat exchanger?

Because replacing a heat exchanger can take up to eight hours or longer, it represents the bulk of the cost. If your warranty is expired, and you would need to pay both parts and labor for a new heat exchanger, look further into whether a full unit replacement would be more advantageous for you.

Does a cracked heat exchanger leak carbon monoxide?

It is important that the heat exchanger is always in proper working condition. If it cracks or leaks, the exhaust gases, which include carbon monoxide, can mix with the air in your home resulting in a potentially deadly situation.

What is most expensive part to replace in a furnace?

Following are some of the most costly furnace parts to fix or replace:
  • Heat Exchanger. Typical Cost: $500 – $1,500. ...
  • Blower Motor. Typical Cost: $400 – $1,200. ...
  • Circuit Board. Typical Cost: $300 – $650. ...
  • Gas Valve. Typical Cost: $200 – $1,000. ...
  • Thermostat. Typical Cost: $100 – $500.

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