How does a cylinder unloader function in a refrigerant system?

A cylinder unloader in a refrigerant system is designed to manage the operation of the compressor by altering the state of the suction valve during specific phases of the mechanical cycle. In particular, during the return stroke of the compressor, the unloader allows the suction valve to remain open. This enables the system to circulate refrigerant for efficient operation and helps in managing the load on the compressor.

By keeping the suction valve open during the return stroke, the cylinder unloader plays a crucial role in decreasing the workload of the compressor when cooling demands are lower. This mechanism not only enhances the efficiency of the refrigerant system but also contributes to energy savings, as it effectively reduces the operational strain on the compressor.

This correct function is vital for optimizing the performance and longevity of refrigeration systems, ensuring they operate within desired parameters. The other options do not accurately reflect the purpose and functioning of a cylinder unloader within the context of refrigerant systems.