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Cracked Heat Exchanger
in Portland, ME
The heat exchanger is the most critical part of a gas furnace. It keeps combustion gases, including carbon monoxide, away from the air that blows through your home. In Portland, where furnaces often run 7 months a year, heat exchangers in furnaces from the 1990s and early 2000s are reaching the end of their service life. A crack isn't always visible and doesn't always trigger a carbon monoxide alarm right away, which makes it dangerous.
Quick Answer
The heat exchanger is the metal wall inside the furnace that separates combustion gases from the air your family breathes. When it cracks, carbon monoxide can get into the house. In Portland, heat exchangers often crack after 15 to 20 years of hard use through long winters. This is not a repair to put off. If you have a crack confirmed, the furnace needs to be shut down. Call (207) 387-7691 right away.
Telltale Signs
Warning Signs to Watch For
- Carbon monoxide detector alarming with no obvious source
- Occupants experiencing headaches or nausea that clear up when they leave the house
- Visible soot streaks on or near the furnace cabinet
- Flame in the burner flickers or bends when the blower starts
- Furnace is more than 20 years old and has never had an inspection
Root Causes
What Causes Cracked Heat Exchanger?
Age and Thermal Stress Cracking
Heat exchangers expand and contract with every heating cycle. After 15 to 20 years of Portland winters, where the furnace runs almost every day from October through April, the metal develops fatigue cracks the same way metal does when you bend it back and forth. These cracks start small and invisible and grow over time.
The Fix
Furnace Replacement
A cracked heat exchanger cannot be patched safely. The furnace is replaced with a correctly sized new unit. The old unit is removed from service immediately.
Overheating from Restricted Airflow
When airflow through the furnace is blocked by a clogged filter or closed vents, the heat exchanger gets hotter than it was designed to run. Portland homes that go all winter without changing a filter can push the heat exchanger temperature high enough to accelerate cracking. A furnace that trips its limit switch repeatedly is often doing so to protect a heat exchanger that's already stressed.
The Fix
Airflow Correction and Heat Exchanger Inspection
The technician restores proper airflow, then inspects the heat exchanger with a camera and combustion analyzer. If cracking is found, the furnace is taken out of service.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Age and Thermal Stress Cracking | Overheating from Restricted Airflow |
|---|---|---|
| Burner flame bends toward the heat exchanger wall when blower starts | ||
| Furnace is 18 or more years old and runs every day all winter | ||
| Furnace has been overheating and tripping limit switch repeatedly | ||
| Soot or carbon tracking visible on the outside of the furnace cabinet | ||
| Carbon monoxide detector alarming only when heat is running |
Free Inspection
Get a Diagnosis in Portland
An on-site inspection is the only way to confirm which cause applies to your property. Free, no obligation.
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