What does draft refer to in heating systems?

In heating systems, draft refers to the pressure differential between warm indoor air and cool outdoor air. This concept is crucial for the effective operation of heating systems, as it determines how air moves through the system and influences the combustion process. A proper draft allows for the efficient expulsion of exhaust gases from the furnace or boiler, ensuring that fresh air can be drawn into the system for combustion.

When there is a significant pressure difference where the indoor air is warmer than the outdoor air, this helps to promote the upward movement of warm air and the downward movement of cooler air. It is essential for maintaining efficiency and safety within the heating system. Poor draft can lead to incomplete combustion, resulting in wasted fuel, inefficient heating, or potentially hazardous conditions due to the buildup of harmful gases.

In contrast, the other options touch on different aspects of heating systems, such as combustion efficiency and temperature differentials, but do not directly address the fundamental definition of draft in relation to pressure differentials in heating systems. Understanding draft is essential for maintaining optimal performance and safety in any heating installation.