In a condensing gas furnace, which form of heat is primarily recovered by the condensing heat exchanger to improve efficiency?

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Multiple Choice

In a condensing gas furnace, which form of heat is primarily recovered by the condensing heat exchanger to improve efficiency?

Condensing furnaces gain efficiency by recovering heat from the moisture in the exhaust through a phase change. When the hot exhaust gas cools in the condensing heat exchanger, the water vapor condenses into liquid water. That condensation releases latent heat—the energy stored in the phase change from vapor to liquid—which would otherwise go up the chimney. Capturing this latent heat adds useful heat to the home's supply, boosting overall efficiency. This is different from sensible heat, which is just temperature change without a phase change; radiant heat is heat transfer from a surface by radiation and isn’t what the condenser primarily recovers; and chemical heat refers to energy stored in chemical bonds, not the heat released by condensing water vapor.

Condensing furnaces gain efficiency by recovering heat from the moisture in the exhaust through a phase change. When the hot exhaust gas cools in the condensing heat exchanger, the water vapor condenses into liquid water. That condensation releases latent heat—the energy stored in the phase change from vapor to liquid—which would otherwise go up the chimney. Capturing this latent heat adds useful heat to the home's supply, boosting overall efficiency.

This is different from sensible heat, which is just temperature change without a phase change; radiant heat is heat transfer from a surface by radiation and isn’t what the condenser primarily recovers; and chemical heat refers to energy stored in chemical bonds, not the heat released by condensing water vapor.

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