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Heat Exchangers: Why A Cracked Heat Exchanger is Bad News

By: Team ProSolutions

Every year in Alberta, many people die from accidental carbon monoxide (CO) poisoning. These deaths are accidental and can be prevented. One of the biggest causes? Problems with fuel-burning appliances like furnaces. Specifically, cracked furnace heat exchangers can cause this potentially deadly problem.

Everyone knows carbon monoxide in your home is not good for your health. But, at what point is it unsafe and how can you prevent accidental poisoning from happening in your home due to a cracked heat exchanger?

In this article, we’ll discuss heat exchangers, what they are, and why cracks can be so dangerous. Stay tuned for answers to the following questions:

What is a heat exchanger?
What are the dangers of a cracked heat exchanger?
What causes a heat exchanger to crack?
How do I know if my heat exchanger is cracked?
Who can fix my cracked heat exchanger?
How can I prevent cracks in my furnace heat exchangers?
Are there certain brands of furnaces that are known for getting cracked?
When does carbon monoxide become dangerous?
At what level do CO detectors go off?
Are CO detectors enough to protect me and my family from CO poisoning?

What is a furnace heat exchanger?

A heat exchanger is the part of your furnace that transfers heat from the fuel being burned. The exchanger also prevents the furnace’s exhaust from mixing with the air in your home.

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 are the different types of heat exchangers?

There are several different types of heat exchangers – two of the most common include shell and tube heat exchangers and plate heat exchangers.

The most common type is a tube (or shell and tube) heat exchanger. These heat exchangers contain a single tube or several parallel tubes (called a tube bundle) enclosed within a sealed shell. One fluid flows through the small tube (or tubes) and another fluid flows through the sealed shell around the smaller tube(s). The idea here is that heat is transferred between the two fluids, which are of different temperatures, through the tube walls. These fluids can be liquids or gases.

heat exchangers tube and shell ⋆ ProSolutions Inc

Stamped, or plate, heat exchangers, on the other hand, are composed of thin, stamped plates that are stacked and bundled together. Pairs of plates are stacked and bolted or welded together, creating channels for fluid to flow through. Much like a tube heat exchanger, the goal is to transfer heat from one fluid to the other through the walls of the plates.

While both shell and tube and plate heat exchangers are similar in concept (i.e. exchanging heat between two fluids), they are very different in their construction and therefore offer differing advantages.

Advantages of shell and tube heat exchangers

  • Simple
  • Flexible
  • Easier and less expensive to service

Advantages of plate heat exchangers

  • More compact
  • Higher temperature capabilities

Furnace heat exchanger cracks

Heat exchanges can crack for various reasons, creating a potentially dangerous situation in your home. The most dangerous situation results from carbon monoxide leaking from a cracked heat exchanger.

What are the dangers of a cracked heat exchanger?

A cracked heat exchanger can be very dangerous. When cracked, gases from the exhaust can leak out into your home. These gases include carbon monoxide – a colorless, odorless, tasteless gas that can cause serious side effects, including death.

What causes a heat exchanger to crack?

There are several reasons your heat exchanges might crack but the most common causes include:

  • Frequent temperature cycling – the constant expansion and contraction of the metal due to continuous heating and cooling wears down and weakens the metal, resulting in cracks over time.
  • Poor furnace preventative maintenance – furnace tune-ups provided by a reputable company are very important. Without regular maintenance, rust, and corrosion that results from dust, moisture, and heat, will weaken the metal of your heat exchangers, resulting in dangerous cracks. An overheated heat exchanger can also lead to cracks. Overheating often results from a dirty air filter – another reason for regular maintenance on your furnace.
  • Age – age can also play a role in the condition of your heat exchangers. A heat exchanger lasts about fifteen to eighteen years –  if yours is older, it may be time to consider replacing your heat exchangers.
  • Poor installation – unfortunately, poor installation is often the case in Edmonton. Many installers do not properly set the Start-up Temperature Rise to a level that is appropriate for Edmonton’s elevation. They base this setting on the manufacturer’s specs – 2000 ft. However, at a higher elevation, less air in Edmonton means that the calculations need to be adjusted. More often than not, this setting is improperly set and can lead to cracks in your heat exchangers. A professional and reputable installer is therefore important to ensure that you will not experience any dangerous issues like a CO leak.
  • Bad manufacturing – metallurgical heat exchanger failure, bad batches, etc. can lead to cracks in heat exchangers. At any given time there is usually one bad furnace out there that is experiencing common issues like cracks in heat exchangers. It seems each manufacturer goes through this at some point and currently Carrier Furnaces are having these problems.

Types of cracks

There are 3 types of cracks that can occur in your heat exchangers. 

  1. Partial cracks – partial cracks, also known as hairline cracks, do not go all the way through the metal. These cracks may not be dangerous initially but can easily become larger and more dangerous, as the crack continues to grow due to the constant heating and cooling of the metal.
  1. Through cracks – these types of cracks, also known as small or minor hairline cracks, can be dangerous if gases are leaking through into the air in your home. It is important to have a professional take a look and access the damage to determine whether the crack is a danger to you and your household.
  1. Large fissures – a crack like this is large. You may be able to fit a toonie into it or see light coming through the crack, for example. Cracks like this are dangerous and should be dealt with immediately by replacing your heat exchanger. 

How do I know if my heat exchanger is cracked?

Several signs that you may have a crack in your heat exchanger include:

  • A flickering flame when you turn on the heat
  • Soot
  • Corrosion and/or cracks on other parts of your furnace
  • Strong, unpleasant smells (similar to formaldehyde)
  • Water under your furnace
  • Carbon monoxide detectors going off in your home
  • Members of your household feeling lightheaded, nauseous, sick or disoriented

These signs may alert you to a crack however, it isn’t possible to see the heat exchanger in your furnace. In order to do a visual inspection, you would need to dismantle your furnace which can take many, many hours. Therefore, you won’t be able to look for and see a crack yourself. 

This is where a professional contractor comes in. Companies like ProSolutions have special tools like scope cameras that are able to get inside your furnace to see what is going on. These cameras are very expensive (the one used by ProSolutions, for example, is approximately $4,000) but can reach places that other tools cannot. This scope camera also has night vision which is helpful considering it’s dark in the furnace where the heat exchanger is located. The tool also provides a large external screen to see and record images and video of the heat exchanger that can be used to inspect for cracks.

The best way to tell if your heat exchanger is cracked is to hire a professional team like ProSolutions to check it. This will ensure that you and your family are safe inside your home.

prosolutions furnace tune ups ⋆ ProSolutions Inc

Companies like ProSolutions Plumbing, Heating & Air Conditioning provide furnace maintenance plans to help keep your heating equipment in top working condition. Regular inspections of your furnace will ensure there are no cracks or other problems that may pose a threat.

Make sure to always have a properly installed, working carbon monoxide detector in your home.

Who can fix my cracked heat exchanger?

You should always have a professional heating services provider do furnace repairs and tune-ups for you. They will be able to examine your furnace and heat exchangers and provide you with a course of action. If your heat exchangers are cracked, they will replace them in order to ensure the safety and comfort of you and your family.

How can I prevent cracks in my furnace heat exchangers? 

You can prevent cracks in your furnace heat exchangers by:

  • Investing in proper preventative furnace maintenance and furnace tune-ups
  • Changing your furnace filters frequently
  • Keeping the utility room clean
  • Ensuring your furnace is properly installed with an optimized start-up temp rise set

Preventative furnace maintenance is, by far, the best way to keep your heat exchangers from becoming cracked and to ensure you and your family’s safety in your home.

The Government of Alberta suggests that appliances, such as furnaces, be cleaned and inspected by a professional every year before cold weather arrives.

Current furnaces with an above-average rate of heat exchanger failure

There are certain brands of furnaces that are known for getting cracked heat exchangers. Most manufacturers, at some point, go through a period where troubles with their heat exchangers are common. Right now, Carrier furnaces and Carrier heat exchangers are facing this issue.

In addition to Carrier, GFA, TUA, and Weathermaker models are commonly having issues in the Edmonton area. Units that are approximately ten to fifteen years old seem to be experiencing the most problems. 

If you currently have one of these models, it’s a good idea to contact a local plumbing and heating company that can take a look to ensure there are no issues with your furnace. Cracks in the heat exchangers of these furnaces can be very dangerous, especially if they are leaking potentially deadly carbon monoxide into your home.

When does carbon monoxide become dangerous?

Any amount of CO can be dangerous, especially for health compromised individuals. In addition to a person’s health, their age, the concentration of CO (measured in parts per million, or PPM) in the air, and the length of exposure play a significant role in how severe the side effects will be.

For example, a healthy person exposed to 1 – 70 PPM of CO for a prolonged period of time will likely not experience any symptoms. However, a person with heart problems may experience chest pain.

Symptoms of CO poisoning

Carbon monoxide can be especially dangerous to people with pre-existing conditions and those who are asleep or intoxicated. In these cases, irreversible brain damage or death may occur without anyone noticing the issue.

Below are the signs and symptoms of CO inhalation at various concentrations.

50 PPM or less

This is considered low-level exposure and should not result in any symptoms in healthy adults. 50 PPM is considered the maximum allowable concentration for an eight hour period.

51 – 100 PPM

Considered mid-level exposure, this concentration is also unlikely to cause symptoms in healthy adults.

Greater than 101 PPM 

This concentration is considered to be a high-level exposure if no symptoms are experienced. However, it is considered dangerous if anyone in your household is experiencing symptoms.

200 PPM 

At this exposure level, a person may start experiencing a headache, fatigue, dizziness, and nausea after two to three hours.

400 PPM

Headaches will occur in one to two hours at 400 PPM and exposure at this level can be life-threatening after three hours.

800 PPM

Dizziness, nausea, and convulsions will start within forty-five minutes and the person will be unconscious within two hours. This high level of exposure can result in death within two to three hours

1,600 PPM

Headache, dizziness, and nausea will occur within 20 minutes and death will result within one hour.

In general, signs and symptoms to look out for that may indicate CO poisoning include:

  • Headache
  • Weakness
  • Dizziness
  • Nausea/vomiting
  • Feeling hungover
  • Shortness of breath
  • Confusion
  • Blurred vision
  • Loss of consciousness

If you think you might be experiencing carbon monoxide poisoning, please seek professional medical advice immediately.

It is important to note that carbon monoxide poisoning doesn’t always happen suddenly at high levels – it can also occur over time. In fact, breathing in low levels of CO over an extended period of time can lead to heart problems and even brain damage. 

If CO levels in your home increase above 70 PPM and stay that way for some time, this can lead to noticeable effects including headache, nausea, and fatigue. If the levels go higher (150 – 200 PPM) disorientation, unconsciousness, and even death may result.

Carbon monoxide alarms in your home can help prevent CO poisoning. However, they are not a fail-safe way to avoid the dangers of carbon monoxide. In fact, CO detectors may not sound the alarm soon enough to prevent some effects. Therefore, it is important to take other measures to ensure you do not have a carbon monoxide leak in your home.

Carbon monoxide detectors

While a CO detector is not 100% effective, you should always have at least one installed in your home.

Unfortunately, carbon monoxide can have negative effects even at low levels and CO detectors may not detect these levels soon enough to save you from low-level exposure.

Below are the detection levels and alarm response times for three of the most common CO detector brands on the market.

At what level do CO detectors go off?

GE Interlogix

The GE Interlogix CO detector is sensitive to carbon monoxide levels between 70 – 400 PPM. The alarm’s response times are as follows:

  • 70 PPM – one to four hours
  • 150 PPM – ten to fifty minutes
  • 400 PPM – four to fifteen minutes

First Alert

First Alert’s carbon monoxide detectors will sound once exposure levels reach 70 PPM. Alarm response levels and times are:

  • 70 PPM – one to four hours
  • 150 PPM – ten to fifty minutes
  • 400 PPM – four to fifteen minutes


Kiddie carbon monoxide detectors are more sensitive and offer detection at lower rates than those above. Response time and CO levels are:

  • 40 PPM – ten hours
  • 50 PPM – eight hours
  • 70 PPM – one to four hours
  • 150 PPM – ten to fifty minutes
  • 400 PPM – four to fifteen minutes

As you can see from the detection levels and time above, low levels of carbon monoxide may go undetected in your home for quite some time. Even with a properly installed and working CO detector, it could be hours before a detector alerted you to a low-level exposure. Nonetheless, low levels of carbon monoxide can have devastating effects. This is why it’s important to exercise other measures to ensure CO is not leaking into your home.

Are carbon monoxide detectors enough?

No, a carbon monoxide detector alone is not enough. Carbon monoxide can leak slowly out of cracks in your heat exchanger, slowly poisoning you and your family. 

CO detectors don’t detect carbon monoxide until levels become dangerous therefore, they may not alert you to a problem until it’s too late. Improperly install CO detectors and detectors that have expired or are not working properly can also pose a threat to your safety.

The only sure way to prevent a CO leak is to have regular maintenance and tune-ups performed by a team of professionals on your furnace.

If you’re in Edmonton and concerned you might have a crack in your heat exchangers, contact ProSolutions today. We’d be happy to take a look at your furnace and ensure everything is in working order. 

Don’t forget to book your appointment now before the weather gets cold!

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