What Is A Furnace Heat Exchanger and Why Does That Matter?
The heat exchanger is the metal passage separating combustion products and gasses from the indoor air being heated. This metal is exposed to the hot flame within the furnace and is constantly expanding and contracting as the furnace heats up and cools down. The stress of this constant expansion and contraction will eventually wear the metal out. This is known as “metal fatigue”. Over time, this will cause the metal in the heat exchanger to split or crack-no different than if you were to bend a metal coat hanger back and forth until it breaks. Oversized furnaces (where the gas is continually turning on and off) are subject to more stress and usually wear out sooner due to their operating conditions. These types of furnaces should be inspected yearly.
Plenty of uninformed homeowners will go on line and read things like this information we pulled from the Better Business Bureau’s website where it says:
“Fall is the ideal time of year to have your furnace serviced – before the busy winter season starts. All too often, however, unsuspecting homeowners are duped into buying a new home furnace or authorizing expensive, but unneeded, repairs to their existing heating system by contractors who use scare tactics.
The Better Business Bureau reports that while most furnace companies are reputable, competent and fair; others may falsely tell you that your furnace needs to be repaired or replaced when in reality it does not. These con artists may try to frighten you with warnings that your system is leaking dangerous gases that could explode or poison those inside the house.
Sometimes unscrupulous furnace dealers will offer you a furnace inspection at a too-good-to-be-true low price. They may then use scare tactics to get you to buy a new furnace whether you need one or not. One method they might use in trying to sell you unneeded equipment is to tell you that your furnace has a cracked heat exchanger, is emitting carbon monoxide, must be shut down immediately, and that you need to replace it.
If they claim your furnace is unsafe, allow them to shut it down, after all, it’s better to be safe than sorry. But don’t sign a contract to buy a new furnace until you’ve gotten a second opinion, preferably from your public gas utility, as they won’t try to sell you anything.”
Don’t Let That Information Throw You, Here’s What Causes A Heat Exchanger To Fail?
Start with keeping your furnace’s blower motor and blades clean; is critical. Dirt build-up on the blades of your furnace’s blower can also contribute to early aging of your furnace’s heat exchanger. Blower cleaning is critical since a buildup of dirt on the blower blades will reduce the furnace’s airflow and cause it to use more electricity. The lower airflow will cause the furnace to run hotter, increasing the rate of expansion and contraction of the heat exchanger’s metal. The end result is excessive metal fatigue and eventual premature failure. This is another reason annual furnace maintenance is so critical — especially if more than ten years old.
The only true way to know for sure if your heat exchanger is cracked is to actually see the crack. If a service technician claims to be able to see a crack in your heat exchanger, he should be able to show it to you.
Inspecting The Heat Exchanger
A comprehensive heating system inspection is designed to do just that. We think we do one of the best heat exchanger inspections available. For years the best the best way was a visible inspection of the exposed areas of the heat exchanger with a flashlight and a mirror. This was effective in finding larger holes in easily accessible areas.
Several years ago we learned of a new method which we now employ as necessary based upon the observed conditions of your furnace and its age.
The most advanced method works like a scope a surgeon would use when doing what they call non-invasive surgery. We use a video camera that is mounted on the end of a flexible wand which will show you on a video screen where the crack is located.
The question is, when will the crack be large enough to begin leaking carbon monoxide into your home. When we find a crack or hole in your heat exchanger we shut down your furnace to protect you and your family from any potential dangers and work with you to facilitate an expedited repair or replacement. When it comes to furnaces, knowing positively whether you have a crack or hole in the heat exchanger is a big deal.