What component is necessary when a system does not have unloaders?

In systems that do not utilize unloaders, a solenoid on the liquid line is essential for controlling the flow of refrigerant. The solenoid plays a critical role in regulating refrigerant to the evaporator under certain conditions, especially when the system needs to be shut down or when specific adjustments in the system's operation are required. By controlling the flow of refrigerant, the solenoid helps maintain efficient operation during periods of varying load demands.

When the solenoid is energized, it allows the refrigerant to flow, enabling the system to operate normally. Conversely, when the house cooling demands decrease, the solenoid can close to prevent refrigerant from entering the evaporator, thereby reducing cooling capacity and preventing the compressor from working against a low load.

In contrast, components like an expansion valve or bypass valve serve different functions within the refrigeration cycle, focusing primarily on managing refrigerant flow or pressure variations rather than acting as the primary control mechanism in the absence of unloaders. The compressor crankshaft, while crucial for the mechanical operation of the compressor, does not control refrigerant flow directly.

Thus, the solenoid on the liquid line becomes a vital component to ensure proper system function when unloaders are not part of the design.