How is discharge from one or more cylinders allowed to flow through a bypass line and into the suction line on a compressor with external unloaders?

The correct answer identifies the function of a solenoid valve in managing the flow of discharge from one or more cylinders of a compressor equipped with external unloaders. When external unloaders are used, the compressor can adjust its capacity based on the demand for cooling or heating.

In this system, a solenoid valve is utilized to control the flow of refrigerant. When the solenoid valve opens, it allows the discharge from the cylinders to bypass and flow back into the suction line. This mechanism helps regulate the refrigerant flow and alters the compressor's capacity without the need for the compressor to cycle on and off, providing more efficient operation and improved comfort in the conditioned space.

Understanding this process clarifies how the compressor can modulate its performance based on the system's needs. While other aspects, such as cycling the compressor or increasing pressure, are related to compressor operation, they do not specifically facilitate the discharge through the bypass line as effectively as the activation of a solenoid valve does. This capability is essential for achieving energy efficiency and maintaining desired temperatures within HVAC systems.