Heat Exchanger
Updated
The heat exchanger is the set of sealed metal chambers inside a gas furnace where combustion happens. Burners heat the metal from the inside, household air picks up that heat from the outside, and the two air streams never mix. That separation is the whole job.
Combustion byproducts, including carbon monoxide, stay contained and vent out the flue. Metal that heats and cools thousands of times can eventually crack, and a cracked heat exchanger can let those byproducts reach household air. A suspected crack is a shut-it-down-and-call situation, not a run-it-until-the-appointment one. It is one of the main things a technician inspects on an older furnace.
Common Questions
What does a heat exchanger do?
The heat exchanger keeps the fire and your household air separated while letting heat pass between them. Burners inside a gas furnace heat the metal chambers from within, air blows across the outside and warms up, and combustion byproducts vent out the flue.
What are the signs of a cracked heat exchanger?
Common signs include a carbon monoxide alarm going off, soot around the furnace, an odd burner flame, or repeated safety shutdowns. None of them proves a crack on its own. A technician confirms it with an inspection during a furnace repair visit. Until then, leave the furnace off.
Is a cracked heat exchanger worth fixing?
On a newer furnace still under warranty, replacing the exchanger can make sense. On an older unit, the labor involved often puts the cost close to a new furnace with a better AFUE rating, so it becomes a repair-versus-replace conversation with real numbers on paper first.
Related Terms
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