Air Conditioning Repair Certification (ETI) Practice Exam

An increase in head pressure leads to an increase in the pressure at the inlet of the capillary tube. In a capillary tube, the flow of refrigerant is directly influenced by the pressure differential between the inlet and outlet. When head pressure increases, it results in a higher pressure at the inlet, but because the capillary tube has a fixed diameter and length, this can create a scenario where the flow is restricted due to the increased resistance to flow.

In a typical system, an increase in head pressure often results from factors such as overcharging the refrigerant, high ambient temperatures, or restricted airflow. These conditions can result in less refrigerant being able to pass through the narrow confines of the capillary tube at any given moment, as the increased head pressure can exceed the flow capacity of the tube, effectively resulting in a reduced flow rate.

Therefore, the correct understanding here is that as head pressure rises, the system's ability to maintain a sufficient flow of refrigerant through the capillary tube diminishes, leading to less refrigerant being able to effectively travel through the system.