What if my furnace heat exchanger is bad?

1. What is a heat exchanger?

The heat exchanger in a furnace separates the combustion process from your breathing air. 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 the house.

The heat exchanger must have an air (and gas) tight seal to separate the gasses in the flue products inside the heat exchanger from the breathing air passing over the outside surface. This is because the flue gasses can be poisonous – such as deadly carbon monoxide – and contamination of the breathing air by these gasses pose a health risk and can be fatal.

2. Why do heat exchangers fail?

All heat exchangers fail eventually. This is because of metal fatigue. Metal when it is heated up expands, and when it is cooled off contracts. This expansion/contraction cycle is part of the normal furnace heating process. Over time this constant expansion and contraction has the same effect on a heat exchanger that bending a paperclip back and forth: it breaks. And when that happens contamination occurs and it is no longer safe.

While heat exchangers are typically manufactured to last between 10 – 20 years, many factors can accelerate the process of heat exchanger failure. These factors usually fall under the categories of poor maintenance, poor initial system design and installation, or poor equipment design by the manufacturer. Any one or a combination of these factors can result in a heat exchanger failing in a few short years.

3. How can you know when a heat exchanger has failed?

A heat exchanger must be visually inspected on a regular basis. Visual observation of light or water passing through the breach is positive confirmation of a crack or hole in a heat exchanger.

4. What tools are needed to determine if a heat exchanger is bad?

The only absolute way to determine if a heat exchanger is bad is to see it or visually confirm it. The old stand-by method of a mirror and a flashlight has been replaced by high tech infrared video inspection systems. This new technology has advanced the heating industry like arthroscopy has advanced medical surgery. The technician can now see places that are impossible with a mirror alone.

5. What about a carbon monoxide test?

A test for carbon monoxide (CO) can be inconclusive. A test for CO reveals whether a furnace is producing CO. A furnace creating CO is a symptom of bad combustion in a furnace because unlike a car, CO is not a regular by-product of the furnace combustion process. Therefore, a heat exchanger can be breached and if the furnace is not producing carbon monoxide the breach will remain undetected.

6. What are the options if a heat exchanger is bad?

There are only two options if a heat exchanger is bad:

Replace the heat exchanger or replace the furnace. If the heat exchanger is under warranty, this option is a good way to go unless it is unavailable in the time frame needed, which can be immediate in cold weather.

The other factors are energy efficiency and cost of service which can make replacing the furnace a preferable option even if the furnace is under warranty and available. If a furnace is out of warranty the preferable option is to replace the furnace.

7. What about a carbon monoxide alarm?

Relying on a CO Alarm is not an acceptable solution for a bad heat exchanger. This would be as unsafe as driving a car that has a leak in the brake line – you might be able to brake a few times but you wouldn’t want to bet your life on it.   Further it is against the Mechanical Code, Fire Department regulations, and SEMCO policy to allow a furnace to operate that has a bad heat exchanger. A representative from any of these organizations would shut the furnace down.

8. Is a heat exchanger inspection foolproof?  

Use of a mirror and a flashlight is adequate for the accessible spots, however the majority of the heat exchanger can’t be seen. If the technician uses an infrared video inspection system you get as close to foolproof as possible short of totally dismantling the furnace and removing the heat exchanger.

9. How much does it cost to replace a heat exchanger?

Plenty!  The most costly part of replacing a heat exchanger is the labor.  That’s the primary reason it is rarely done.  For most furnaces, the part itself is under lifetime warranty – or 20-year warranty on some models.  The part is covered, but since most furnaces come with a 1-year labor warranty and most homeowners don’t buy extended coverage, the cost of labor must be paid.

Replacing a heat exchanger involves disassembling much of the furnace.  It is right at the core of the unit. It’s an 8-10 hour job for most teams of HVAC technicians.  When you factor in the cost of labor for most heating and air conditioning companies, it gets expensive.  Labor rates vary, but most are between $75 and $125.  Total cost can be in the $600 to $1200 range for replacing a heat exchanger.

10. Repair or replace the furnace?

If you’ve got a furnace less than 10 years old, and it’s a high-performance model – high efficiency, staged heating, variable-speed blower – it may be worth repairing.  Get estimates on both the repair and the replacement and weigh your options.  Have a qualified contractor inspect the furnace and make a professional recommendation.  Get 2 recommendations/estimates if you’ve got the time.  It might be worth it to replace the heat exchanger.

However, if your high-quality furnace is more than 10 years old – and the older it gets – replacing it starts to make more sense.  If the furnace is a basic model to begin with, the cost of the repair may approach or exceed the purchase price. In that case, no decent furnace professional would recommend repairing it. Your money is much better spent on a new furnace.


In most cases, your heat exchanger won’t fail.  If it does, the $600 to $1200 bill should give you reason to consider replacing the entire furnace.  Perhaps the information here will help you make your decision easier.

What Is A Heat Pump?

A heat pump is a standalone, two-component appliance that uses refrigeration technology and electricity to provide heating and cooling for homes, businesses and other applications.

A heat pump has two components – a condenser unit that most often sits outside of a home that produces the heating or cooling, and an indoor unit that typically sits on a wall and passes hot or cool air into the home; because the condenser and air handler are separated or “split” by refrigerant line, heat pumps may sometimes be referred to as “mini-splits.” Heat pumps offer extraordinarily high efficiency rates, as well as the opportunity to provide heating and cooling without needing duct work in the home; because duct work is not required, you may hear heat pumps referred to as “ductless.”

How Does a Heat Pump Work?

In the simplest terms, a heat pump uses electricity and refrigerant to move heat from one location to another.

To provide heat, a heat pump works by extracting heat from the air outside of your home and transferring it to refrigeration coolant – the coolant is then compressed, which increases the temperature significantly; the coolant is then moved to the indoor unit of the heat pump, which then passes air over the hot coolant, increasing its temperature to accommodate the thermostatic call for heat inside the home.

Want To Learn More About Heat Pumps in Oklahoma? Give us a call at 405-243-1613 or visit this webpage.

Why Are Air Filters In Your Home Important?

DID YOU KNOW? Regular filter changes cut 5% - 10% off your energy bill every month.

100% of the air in your home passes through a filter, typically twice every hour. Since clean, quality air filters keep the air in your home fresh, the people inside stay healthier. A quality filter captures the harmful bacteria typically found in sneezes, coughs, viruses and molds, as well as pollutants like dust and car fumes.

Clean filters also keep your HVAC system healthy—they enable it to run more efficiently, keep repair costs to a minimum, and reduce monthly energy bills. About half of your monthly energy bill is attributed to HVAC, and keeping clean air filters is the single most effective way to improve HVAC efficiency. Clogged filters make the HVAC work harder as it conditions your home, which raises your energy bill. (And if there are no filters, the coils will clog, which is even worse for your system.)

We recommend changing filters at least every 3 months, but every 1 to 2 months will usually serve you better (especially if you have a busy lifestyle, family with allergies, pets in the home, etc.). 

Facebook Special Offer - Fall Heating Tune-Up ONLY $69!

Being without heat during the winter can be a miserable experience, especially when you have to wait for service because everyone else in town is having the same problem. If you want peace of mind that you’ll be warm and cozy all winter long, we recommend taking advantage of this special offer!

Call us at 405-243-1613 and tell us that you are a fan of Air Factory OKC and we'll take care of your heating tune-up for only $69 (regular price $99). 

Fall Heater Tune Up Special from Air Factory Heating & Cooling

Early fall is best time of year to schedule furnace maintenance, before you need to turn on your furnace. One of the biggest misconceptions about a furnace is “my system is heating, so it’s working properly.” Many furnaces are operating and heating but doing so with a common unsafe condition, a cracked heat exchanger.

Take a look at this cracked heat exchanger! It needs to be fixed ASAP!

Take a look at this cracked heat exchanger! It needs to be fixed ASAP!

A cracked heat exchanger will heat your home or property as normal, but with an increased risk of carbon monoxide entering the living space. Carbon Monoxide is a colorless, odorless, and tasteless gas that is toxic at high concentrations. A carbon monoxide detector is a good device to have in your home. If you have one, this is the perfect time to make sure the batteries are fresh and new.

You may not be able to completely prevent heating system breakdowns, but you can help avoid them, save money, and maintain your manufacturer’s warranty with professional maintenance from Air Factory Heating & Cooling!