What defines a sealed combustion system in gas heating?

A sealed combustion system is characterized by its ability to draw in air for combustion directly from the outside environment rather than relying on indoor air. This design is essential for improving efficiency and safety in gas heating applications. By sourcing air externally, it prevents the system from consuming the indoor air, which can lead to a drop in indoor air quality and could create a negative pressure within the living space.

This external air intake allows for better control of combustion settings, contributing to optimal efficiency and reducing the risk of backdrafting, where hazardous gases could enter the living space. The sealed nature of the combustion process also minimizes the impact of variations in indoor air pressure, ensuring consistent performance.

In contrast, a system that operates without external air intake can lead to safety issues, and those that rely on indoor air can compromise air quality and heating performance. Therefore, the defining characteristic of a sealed combustion system is its reliance on outside air, as it enhances both operational efficiency and safety.