In a heating system, what is the role of the reversing valve?

The role of the reversing valve in a heating system is to change the direction of refrigerant flow. This is essential in heat pumps, which can operate in both heating and cooling modes. When in heating mode, the reversing valve alters the path of the refrigerant, allowing heat to be extracted from the outside air and transferred into the indoor space. Conversely, in cooling mode, the reversing valve shifts the flow so that the refrigerant absorbs heat from indoors and expels it outside. This versatility is critical to the dual functionality of heat pumps, making the reversing valve a key component in their operation.

The other options don't accurately reflect the function of the reversing valve. For instance, while the system does ultimately aim to increase ambient temperature during heating, that is not the specific function of the reversing valve. Similarly, the tasks of expanding the refrigerant and monitoring system performance are carried out by other components in the heat pump system, such as the expansion valve and various sensors, respectively.