What does a 'natural draft' in gas systems primarily rely upon?

A 'natural draft' in gas systems primarily relies on gravity and thermal differences to facilitate the movement of combustion gases. This phenomenon occurs because warm air, being lighter than cooler air, rises due to convection. As the hot gases rise through the venting or chimney system, they create a low-pressure area at the base, which draws in cooler air from the appliance. This natural circulation allows for ventilation without the need for mechanical assistance.

The effectiveness of this system depends on the height of the chimney or vent and the temperature difference between the exhaust gases and the ambient air outside. Conventional systems designed with proper venting height and configurations can effectively utilize this principle. It’s important for installers to ensure that the design is optimized to create sufficient updraft for proper combustion and venting.

Mechanical fans, pump systems, and external blowers are associated with forced air systems that actively push or pull air through mechanical means rather than relying on natural forces. These types of systems are typically used when natural draft is insufficient or impractical.