An appliance that is less than 83% efficient and non-positive would be categorized as?

The categorization of gas appliances is based on their efficiency and venting methods. An appliance that is less than 83% efficient and non-positive (meaning it doesn't create a negative pressure to effectively vent combustion gases) falls into the Category I classification.

Category I appliances include those that use natural draft venting systems and operate on non-positive vent pressure. They typically have low efficiency ratings and rely on the natural buoyancy of flue gases to expel combustion byproducts. Given that the performance threshold of 83% is a critical marker for categorization, an efficiency below this level indicates the appliance cannot be safely classified as a higher category, which would require improved venting and efficiency.

Understanding these categories is essential for ensuring proper installation and compliance with safety standards, as each category has specific requirements regarding venting systems and combustion efficiency that must be adhered to for safe operation.