Gas Fitter Practice Test

What does a condensing warm air furnace have?

1. Operates without a heat exchanger

2. One heat exchanger

3. Two heat exchangers

4. Three heat exchangers

The correct answer is: Two heat exchangers

A condensing warm air furnace is specifically designed to improve the efficiency of heating by utilizing two heat exchangers. The first heat exchanger is where the combustion occurs, extracting heat from the burning gas. The second heat exchanger captures additional heat from the exhaust gases by cooling them down to the point where condensation occurs, hence the name "condensing" furnace. This allows the system to recover latent heat from the flue gases, which would otherwise be lost and vented outside. The presence of two heat exchangers significantly enhances overall system efficiency, often exceeding 90%. This is why the correct answer highlights the inclusion of two heat exchangers, fundamentally distinguishing condensing furnaces from traditional models, which typically use a single heat exchanger and are less efficient because they release more heat into the venting system.