Gas Heat ESCO Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

A Category I natural gas furnace is designed to vent flue gases directly to the outdoors without requiring a fan for venting, which makes its efficiency and air temperature characteristics critical for proper performance. The typical air temperature rise for this type of furnace usually falls within the range of 40°F to 70°F. This temperature rise is a measure of how much the air temperature increases as it passes through the heat exchanger of the furnace.

When air is heated by the furnace, this rise indicates the effectiveness of the heat transfer process from the combustion of gas to the air being circulated in the home. An air temperature rise in this range suggests that the furnace is operating efficiently and effectively delivering heat to the living space.

Maintaining a proper temperature rise is essential for system performance, as it impacts comfort levels and the efficiency of heating. If the air temperature rise were too low, it might indicate issues like insufficient combustion, airflow problems, or an oversized furnace, which could lead to discomfort and inefficiency. Conversely, if it were too high, it might signal airflow restrictions or other operational issues.

The other temperature ranges provided in the choices do not align with the established performance parameters for Category I gas furnaces, thus reinforcing why the range of 40°F to