How does natural draft affect flow in a venting system?

Natural draft is a key factor in determining the efficiency and functionality of a venting system for combustion appliances. It is primarily driven by the temperature difference between the flue gases and the ambient air. When flue gases are heated, they rise due to their lower density compared to cooler air, thereby creating a vacuum or negative pressure in the flue or chimney that facilitates the upward movement of air and gases.

Greater draft enhances the lifting force on the flue gases, encouraging a stronger upward flow. Consequently, as the draft increases, it enhances the ability of the combustion gases to rise and exit through the venting system more effectively. This increased flow ensures that harmful combustion byproducts are efficiently expelled from the home, contributing to a safer and more effective operating environment for the appliance.

Thus, in a properly functioning venting system, the relationship between natural draft and flow is direct: as the draft increases, it causes a greater flow of combustion gases outward. In contrast, lesser draft would lead to insufficient flow, potentially resulting in backdrafts or the accumulation of dangerous gases within the system.