Final answer:
In a standard heat pump system, the scale trap is most likely located between the condenser and the receiver, where it can effectively remove scale or debris formed in the system.
Step-by-step explanation:
The scale trap is typically used in a refrigeration or heat pump system to remove any scale or debris that may have formed within the system to protect the components and maintain efficiency. While the exact location can vary depending on the system design, it is generally placed where the risk of scale formation is highest, which is often associated with the processes involving significant changes in pressure and temperature. From the provided options, the most likely location for a scale trap in a standard heat pump system would be between the condenser and the receiver, as the refrigerant is typically in liquid form and has just condensed, making it an opportune point for scale to drop out before entering the receiver. Therefore, the correct answer is (2) Condenser and receiver.