NATE Air Conditioning and Heat Pumps Practice Exam

What amount of auxiliary electric heat is needed when the output of a heat pump on a design day equals 18,800 Btuh and the heat loss of a home is 29,700 Btuh?

1. 2.1 kWh

2. 3.2 kWh

3. 5.0 kWh

4. 10.9 kWh

The correct answer is: 3.2 kWh

To determine the amount of auxiliary electric heat needed, we start by calculating the difference between the heat loss of the home and the output of the heat pump. On a design day, if the heat pump has an output of 18,800 Btuh and the home has a heat loss of 29,700 Btuh, we can find the shortfall in heating capacity. The shortfall is calculated as follows: Heat loss of the home - Output of the heat pump = 29,700 Btuh - 18,800 Btuh = 10,900 Btuh. This value represents the additional heating requirement that must be met by auxiliary electric heat. To convert the required heating from Btuh to kilowatts (kW), we use the conversion factor where 1 kW equals 3,412 Btuh. Therefore, we can find out how many kilowatts are needed: 10,900 Btuh ÷ 3,412 Btuh/kW = 3.2 kW (rounded). Since typically, the amount of energy needed in kWh over the course of one hour can be looked at (considering constant usage), this means that 3.2 kW over one hour is indeed 3.2