Which of the following is NOT a characteristic of gravity, warm-air furnaces?

Warm-air furnaces that operate based on gravity use the natural rise of warm air to circulate heat throughout a space. One of the defining characteristics of this type of system is that it does not employ a fan to assist in air movement; instead, it relies on the natural buoyancy of the warm air. This means there is no mechanical intervention to push air through the duct system, making the absence of a fan a fundamental aspect of gravity warm-air furnaces.

Additionally, warm-air furnaces do not typically incorporate high-temperature limit switches, which are safety features found in forced-air systems. These switches are designed to shut down the furnace in the event of overheating. The reliance on natural convection in gravity systems means they generally don't need such a feature since they aren't designed to reach high temperatures rapidly.

The location of the furnace is typically not standardized to the center of the house and can vary based on the layout and construction of the building. Similarly, the supply and return ducts in a gravity system are often larger and rounded, allowing for effective air movement without mechanical push. These ducts need to be sloped upwards from the furnace to facilitate the natural upward movement of warm air.

Therefore, the characteristic that is not associated with gravity warm-air furnaces is having a