Many furnace breakdowns are little more than a minor annoyance until you have them fixed. However, there is one furnace problem that is particularly dangerous: a cracked heat exchanger. This component, which serves as a barrier between the flame and the circulating air, can crack as a furnace ages, especially if the furnace is oversized for the home. When this happens, carbon monoxide can leak into your home, which as you probably know, can have deadly consequences.
So, how do you know that your heat exchanger has cracked? Assess whether your furnace is showing these symptoms.
A Yellow Flame
A yellow flame indicates that the furnace is not burning as hot as it should. Sometimes, this just means that the gas line is blocked or that the burner is dirty. But other times, it may mean that the heat exchanger is cracked. When everything is working properly, the flame should be blue or white.
Soot Around the Furnace
Soot is a black, powdery substance. If you rub it between your fingers, it feels a little greasy. This black buildup may appear around your furnace when your heat exchanger is cracked. It is the result of incompletely burning fuel, and you'll often see soot in conjunction with a yellow flame. When the problem becomes more serious, you may see soot around the air vents, too.
Do you remember the strange chemical odor that the frogs had when you dissected them in high school? If you smell that same odor in your home and there's no other good explanation for it, the problem may be attributed to a cracked heat exchanger. Some people compare the smell to that of oil-based paint, and others say it smells like formaldehyde. It tends to be strongest when the furnace has just turned on.
Carbon Monoxide Alarm Going Off
If the carbon monoxide alarm rings, this is a sure sign that something is wrong -- and if your furnace still seems to be working, there's a good chance it's a cracked heat exchanger. When the alarm sounds, turn off the furnace and leave the home. If you feel ill, seek medical attention. Otherwise, just call your HVAC contractor and have them check things out before you venture back into the home.
A cracked heat exchanger is a problem your home furnace repair company can fix. However, since it is an expensive repair, you are sometimes better off replacing the furnace.