The heat exchanger is the metal chamber inside a furnace where combustion happens. Hot combustion gases stay on the inside of the metal walls; the house air being heated passes over the outside. The two air streams should never mix.
Cracked Heat Exchanger = Carbon Monoxide Risk
When the heat exchanger cracks (usually from years of heating/cooling cycles), combustion gases including carbon monoxide can leak into the air being blown through your home. This is one of the most serious furnace problems you can have. Every Colorado home should have working CO detectors on every floor.
Types of heat exchangers
- Primary heat exchanger — present in all gas furnaces. Direct combustion chamber.
- Secondary heat exchanger — only in high-efficiency condensing furnaces. Captures additional heat from cooling flue gases. More prone to corrosion in hard-water areas.
Signs of a cracked heat exchanger
- Yellow or flickering burner flame (should be steady blue)
- Soot accumulation around the burner area
- “Chemical” or formaldehyde smell when furnace runs
- CO detector intermittently alarming
- Excessive moisture on windows when furnace runs
If a cracked heat exchanger is confirmed, the furnace must be replaced or have the heat exchanger swapped (often comparable cost). Don’t run the furnace until diagnosed.
Related: Furnace, Carbon Monoxide, AFUE. See also: 24/7 emergency.
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Right Way Mechanical is a family-owned HVAC contractor serving Wheat Ridge, Arvada, west Denver, and the Colorado foothills.