What causes a direct-acting low-pressure switch to open its contacts?

A direct-acting low-pressure switch is designed to monitor the pressure within a cooling system and respond accordingly. When there is a drop in suction pressure, it indicates that the refrigeration system is not able to adequately absorb heat or is experiencing a fault, such as low refrigerant levels or a restriction in the flow.

In such scenarios, the low-pressure switch reflects this decrease by opening its contacts. This action typically serves as a protective measure, preventing the compressor from running under conditions that could lead to damage, such as a lack of lubrication or overheating due to insufficient refrigerant. Essentially, the switch helps maintain safe operational parameters for the system by interrupting power to the compressor when it detects that pressure has fallen below a certain threshold, thus helping to protect the integrity of the system.

The other potential answers do not align with the behavior of a direct-acting low-pressure switch. Opening due to a drop in discharge pressure or a rise in discharge pressure would pertain to different types of pressure switches with distinct operational thresholds. Furthermore, an action at the beginning of each cycle does not accurately reflect the purpose of a low-pressure switch, which is more about real-time monitoring and responding to changes in the system's operational state.