Your furnace's heat exchanger plays an essential role in heating your home. When this part fails, that could bring a warm and comfortable day inside your home to an end. The following is a brief guide on heat exchanger failures, including their causes and how they're repaired.
What Causes Heat Exchanger Failures
Excessive heat and rust formation are the major causes of heat exchanger failure, in most cases. Both can do a number on your furnace if you're not careful or proactive enough on maintenance:
- A lack of adequate air flow caused by undersized ductwork or a clogged air filter can, in turn, cause the heat exchanger to overheat. The excessive heat causes stress cracks to form near welds, bends and other vulnerable areas of the heat exchanger.
- A furnace whose heating capacity exceeds what's needed for your home can short-cycle as it attempts to heat your living spaces. Short-cycling prevents your furnace from evaporating the condensate that naturally forms as a byproduct of the heating process. As a result, the leftover moisture allows rust to form within the heat exchanger, producing cracks and holes in the process.
When a crack or hole forms on the heat exchanger, it allows air from the blower fan to seep through. This can cause the flame to flutter or "roll out" of its confined space, triggering a safety shut-off switch that shuts down the furnace automatically, in many cases.
The biggest danger of a heat exchanger crack is that it allows carbon monoxide, another byproduct of the combustion process, to leak out into your living areas. This odorless, colorless and tasteless gas is almost impossible to detect unless you have a carbon monoxide detector set up in your home.
Detecting Cracks and Leaks
A cracked heat exchanger will likely cause a no-heat condition or set off your carbon monoxide alarm, prompting a service call from your technician. A technician from a company like Mitchell Plumbing & Heating Inc may use one or more of the following methods for detecting cracks and leaks in your heat exchanger:
- Smoke testing
- Trace gas testing
- Visual inspection via camera or the naked eye
Can They Be Repaired?
It's possible to seal the cracks in question through welding, but it's a process that's more trouble than its worth. Not only can the welds fail later on, but there's no guarantee that the welds will prevent a future exchange of gases. Of course, there's no viable way to weld a rusty heat exchanger together without seriously compromising safety.
Once a crack, gap or hole forms on the heat exchanger, it's usually safer to replace the entire part with a brand-new, defect-free replacement. This way, you'll have peace of mind as you continue to use your furnace for years to come.