If an appliance is less than 83% efficient and non-positive, it would be considered a?

An appliance that operates at less than 83% efficiency and is classified as non-positive falls under the Category I classification. This category pertains to appliances that utilize gas and discharge their flue gases into a space that is not deemed "ventilated." In simpler terms, these are appliances that vent directly into the room rather than having a dedicated venting system that directs exhaust to the outside.

The significance of the 83% efficiency threshold is essential in determining the category of gas-fired appliances. When an appliance's efficiency is below this level, it indicates that a significant amount of energy is being lost to the environment, which is why Category I appliances, associated with lower efficiency, often require additional safety measures to prevent the accumulation of hazardous gases within the living spaces.

The other categories (II, III, and IV) pertain to appliances with higher efficiencies and different venting methods. For instance, Category II appliances can have varying venting arrangements but still are more efficient than those in Category I. Understanding these classifications helps ensure proper installation and maintenance for safety and efficiency in gas utilization.