Fuel oil begins to break down under a vacuum exceeding what pressure?

Fuel oil begins to break down under a vacuum exceeding 10 inches of mercury (in hg). When the pressure inside the fuel system drops below this threshold, it can lead to issues such as vaporization of the fuel or the release of dissolved gases. This phenomenon is due to the physical properties of fuel oil and how it behaves under low-pressure conditions.

All fuel oils contain various hydrocarbon compounds that are stable under normal atmospheric pressure. However, once a vacuum surpasses 10 in hg, it can disrupt the stability of these compounds, causing the fuel to deteriorate and become less effective for combustion. This breakdown can result in problems like blocked fuel lines, clogged filters, and ultimately inefficient heating performance.

Understanding this threshold is crucial for HVAC professionals to ensure proper fuel delivery and system efficiency. Maintaining a vacuum below this level helps to ensure that the fuel remains in its liquid state and does not degrade, supporting the reliable operation of heating systems that use oil.