Any appliance in which the products of combustion at the point of entrance to the flue under normal operating conditions have a temperature of 1000 degrees is a ____________ appliance.

Any appliance in which the products of combustion at the point of entrance to the flue under normal operating conditions have a temperature of 1000 degrees is a ____________ appliance.

• A. High-efficiency appliance
• B. Low-heat appliance
• C. Medium-heat appliance
• D. Standard appliance

Answer: (B)

The main idea is how much heat the appliance actually delivers into the living space versus how much goes out with the exhaust. When the products of combustion enter the flue very hot—around extremely high temperatures—the heat exchanger isn’t capturing much of that energy. Most of the fuel’s energy leaves with the exhaust, so the appliance is delivering relatively little heat to the house. That’s described as a low-heat appliance. In contrast, high-efficiency units pull more heat from the combustion gases, so the exhaust leaving the appliance is much cooler. Intermediate categories would fall between these extremes. So, a condition where the flue entrance temperature is very high indicates a low-heat appliance.

The main idea is how much heat the appliance actually delivers into the living space versus how much goes out with the exhaust. When the products of combustion enter the flue very hot—around extremely high temperatures—the heat exchanger isn’t capturing much of that energy. Most of the fuel’s energy leaves with the exhaust, so the appliance is delivering relatively little heat to the house. That’s described as a low-heat appliance.

In contrast, high-efficiency units pull more heat from the combustion gases, so the exhaust leaving the appliance is much cooler. Intermediate categories would fall between these extremes. So, a condition where the flue entrance temperature is very high indicates a low-heat appliance.