“How Can I Tell If My Heat Exchanger Is Cracked?” Beth in Roseville, CA Asks an Expert

Beth in Roseville, CA has had the same heat exchanger for years. In that time, it has served her well, but she’s recently had a few problems with it. Beth asks:

“I’m not totally in the dark when it comes to my furnace. In fact, I’ve had more than a few chats with HVAC specialists about the importance of furnace upkeep, which parts do what, and how long I can expect my furnace to last. I know that one of the most important parts of my furnace is the heat exchanger—and I know that mine is just about at the end of its average lifespan. I also know that even a tiny crack can kill a heat exchanger.

So, with all that in mind, what I want to know is how can I tell if my heat exchanger is cracked? I live out in Roseville and winter is here! I want to make sure that my house stays nice and toasty now that it’s gotten cold out. Thanks!”

Wow, Beth in Roseville! You really have paid attention to your heating and cooling service techs over the years. Kudos to you. I don’t know how old exactly your furnace and heat exchanger are, but seeing as you sound so knowledgeable, I’m going to go ahead and take your word that your heat exchanger is old enough to be in danger of starting to fracture or crack. The truth of the matter is that there isn’t always one simple way to identify a heat exchanger crack, so you have to take a number of complex factors into consideration when you’re trying to figure it out. Think of yourself like an HVAC detective, solving the mystery of the (potentially) fractured heat exchanger.

How to Tell If Your Heat Exchanger Is Cracked Clue #1: How it Should Work

Your first clue in this how can I tell if my heat exchanger is cracked mystery is to figure out what exactly a heat exchanger is—and why it’s so important. This step isn’t really all that relevant to Beth, who has a good deal of base knowledge already, but seeing as she tends to be more of the exception than the rule, I think for a lot of people it’s worth going over.

What is a furnace heat exchanger? In the simplest possible terms, your heat exchanger is the part of the furnace that heats the air. It’s a set of tubes or coils that are looped repeatedly inside your furnace. They must be fully sealed because the air we breath has to be separate from the combustible air in that part of your furnace. It is a combination metal chamber and passageway that starts at the burner assembly and ends approximately where the chimney vent connects to the furnace. Air is heated as it is blown across the hot metal surface of the heat exchanger. The heated air is then distributed through the house to warm it.

Why is it so important to your furnace? If your heat exchanger is cracked, it can be dangerous for you and your family. I’ve talked in the past about how a healthy heat exchanger in your home can prevent illness, but it’s worth reiterating. There are dangerous gasses in your heat exchanger, the most dangerous being carbon monoxide. The most common pollutants that can enter your home’s air through a crack in your heat exchanger include:

• Carbon monoxide
• Carbon dioxide
• Soot
• Nitrogen oxides

How to Tell If Your Heat Exchanger Is Cracked Clue #2: How Old Is It?

Sooner or later your heat exchanger will crack or fail. That’s the very simple reality of it. Don’t blame me, blame metal fatigue. With that in mind, a key piece of info in this investigation is your furnace’s age.

Metal expands when it’s heated, that’s just physics. Then, when it cools, it contracts. In Roseville where Beth lives, and the rest of the Sacramento area for that matter, we have harsher summers and colder winters than other areas. Because of our climate, we run both our heaters and air conditioners quite a bit. This means the metal that seals the dangerous gasses in heat exchangers moves around. Like a paperclip that is bent in and out of shape over and over again, the metal eventually becomes brittle and breaks.

Heat exchangers are built to last 10 to 20 years, but that period could be shorter if an HVAC system is used more often than the norm. Not having proper furnace maintenance performed by a skilled professional will also take years off the life of a heat exchanger.

How to Tell If Your Heat Exchanger Is Cracked Clue #3: Common Signs of a Crack

We’re getting close to discovering the answers behind the heat exchanger mystery. The final part of our investigation is knowing the signs and dangers of a cracked heat exchanger. Here are the most common signs that you may have a problem:

• A change in flame appearance: You know the flame in your furnace? It should be blue if you have a regularly-functioning gas furnace. If the heat exchanger is cracked (or if the burner is dirty), you’ll see a moving yellow flame. That’s a sign to immediately call an HVAC pro.
• Soot build up inside your furnace: Like I noted above, soot can leak out of your heat exchanger if there’s a crack. If you open up your furnace and see a black carbon buildup on the surfaces there, this is another sign that there’s a crack in your heat exchanger.
• Unusual smells: Cracked heat exchangers generally produce a strong, unpleasant smell, kind of like formaldehyde. This can give you headaches and other physical symptoms, so immediately call a local HVAC tech.

Hopefully, I’ve helped shed some light on this matter for Beth, or anyone else worried their heat exchanger is cracked. A good furnace tune-up will involve checking your ductwork, as well as the performance and efficiency of the HVAC system, which will help you avoid the multiple scenarios that lead to a crack in the heat exchanger in the first place. It will also be evaluated for cracks so that you can rest assured toxins aren’t polluting the air in your home.

If you have any concerns about your furnace or heat exchanger, my expert opinion is always to have a trusted HVAC tech out for a visit (which you should have had done for a pre-winter checkup anyway). Be sure to mention to them that you’ve done some investigating and found that your heat exchanger may be in danger. And go ahead and pay attention to what the tech tells you in return, so you can be a responsible homeowner, like Beth, who knows the danger signs to look out for in the future as well.

Contact the HVAC professionals at Bell Brothers to schedule your checkup today. And, while we’re visiting your home, let us give you a whole house assessment for energy efficiency. We’ll offer recommendations and upgrades that are sure to increase your year-round comfort—and decrease your power bills.

Wondering how to finance a new HVAC system, windows, or plumbing? HERO is a unique financing option that helps California homeowners afford energy efficient upgrades to their home. Contact Bell Brothers, a HERO-approved contractor, to learn more. Our local HVAC, plumbing, and window specialists will walk you through the entire process, from applications to installation.

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