What type of appliance is defined by having combustion products with a temperature greater than 2,000 F at the flue entrance?

The definition provided in the question points specifically to an appliance that generates combustion products at a temperature exceeding 2,000 F at the flue entrance. This characteristic is indicative of a high-heat appliance, which is designed to operate at elevated temperatures. Such appliances typically include certain types of furnaces, boilers, and other heating devices that produce significant heat during their operation and can produce exhaust gases at these higher temperatures.

High-heat appliances are generally engineered for applications where the efficiency of heat transfer and high-temperature output are required, such as in industrial settings or for specific heating purposes. This differentiates them from low-temperature or standard appliances, which do not reach these higher exhaust temperatures, often operating within much lower temperature ranges to maintain safe and efficient operation.