NATE Gas Heating Practice Exam

Which of the following is a common cause of a lifting burner flame?

1. A new ignitor

2. Low gas pressure

3. High gas pressure and/or too much primary air

4. Blockage in the flue

The correct answer is: High gas pressure and/or too much primary air

A lifting burner flame typically occurs due to an imbalance of gas and air in the combustion process. The correct choice highlights that high gas pressure combined with excess primary air can cause the flame to lift off the burner ports. This occurs because the optimal mixture of gas and air necessary for stable combustion is disrupted. When too much primary air is introduced or when the gas pressure is excessively high, the flame can be drawn away from the burner, resulting in a lifting or unstable flame. In proper combustion, there is a specific ratio of air to fuel that must be maintained for efficient and safe operation. When the mixture is skewed, it can lead to improper combustion, which not only causes operational issues but also becomes a potential safety hazard due to the instability of the flame. Understanding this principle is essential for diagnosing issues in gas heating systems and ensuring they operate efficiently and safely, making it crucial for technicians to recognize the conditions that lead to a lifting burner flame.