Home Inspection State Practice Exam

While a heat pump is cooling, how should the temperature of the liquid line compare to the outside air temperature?

1. Cooler than the outside air temperature

2. Identical to the outside air temperature

3. Warmer than the outside air temperature

4. Variable based on humidity

The correct answer is: Warmer than the outside air temperature

When a heat pump is in cooling mode, the liquid line carries refrigerant that has undergone a process of compression and condensation. As a result, this refrigerant is discharged from the condenser at a higher temperature than the surrounding air. The heat from the indoor environment is absorbed and expelled outdoors, leading to a situation where the temperature of the refrigerant in the liquid line is indeed warmer than the outside ambient air temperature. The reason for this temperature difference is that the heat pump must transfer heat from inside the home to the outside, necessitating that the refrigerant remains warmer than the external environment to efficiently reject this absorbed heat. Therefore, in cooling mode, you should expect the liquid line to be warmer than the outside air temperature. This characteristic behavior of the heat pump's liquid line temperature during cooling aligns with principles of thermodynamics and the functionality of the refrigeration cycle involved in heat pumps. In contrast, other options do not accurately describe the typical conditions. For example, having the liquid line cooler than the outside air temperature would indicate an inefficient operation or potential malfunction. Identical temperatures would suggest a lack of proper refrigerant flow or heat exchange. Lastly, while humidity can influence various operational aspects of a heat pump, it does not determine the baseline temperature comparison