G2 Gas Fitter Practice Exam

Which type of draft is primarily affected by temperature differences within a chimney?

1. Mechanical draft

2. Natural draft

3. Exhaust draft

4. Balanced draft

The correct answer is: Natural draft

Natural draft is primarily affected by temperature differences within a chimney. This phenomenon occurs because of the principle of buoyancy, where warmer air rises and cooler air descends. When the air inside the chimney is heated by the flue gases, it becomes less dense compared to the cooler air outside. This temperature difference allows the warmer air to rise, creating a draft that pulls combustion gases up and out of the chimney. In systems utilizing natural draft, external environmental conditions can significantly impact the efficiency of the draft. For instance, as outside temperatures drop, the draft can be more pronounced, enhancing the flow of gases. Conversely, in warmer conditions, the draft can diminish. Understanding this concept is crucial for ensuring proper ventilation in gas appliances and maintaining optimal combustion efficiency. Other options, such as mechanical draft, rely on fans or blowers to move air, so they do not depend on temperature differences in the same way. Exhaust draft refers generally to the removal of gases but does not specifically focus on the temperature-driven natural convection of air, while balanced draft systems combine both mechanical and natural drafts to achieve efficient gas removal but are not solely influenced by temperature differences.