What creates a mechanical or induced draft in an appliance?

A mechanical or induced draft in an appliance is created by a fan or blower action. This method utilizes mechanical means to facilitate the movement of air or flue gases, which is particularly important in applications where natural drafting might be insufficient due to factors such as the design of the appliance or the installation setup. The fan or blower actively draws air into the appliance and expels flue gases, enhancing combustion efficiency and ensuring proper ventilation.

In contrast, while the height of the chimney can impact natural draft by creating a temperature difference that can draw air upwards, it does not directly contribute to mechanical draft. Similarly, natural gas pressure is essential for delivering gas to the burner but does not generate draft. Flue gas temperature differences can assist in natural draught scenarios but are not capable of creating induced draft. Hence, the use of a fan or blower is the key factor in establishing mechanical or induced draft, making it the correct choice in this context.