What must a system's design pressure not be less than for proper function?

The correct choice indicates that a system's design pressure must not be less than the saturation pressure at specified temperatures for both the low side and the high side of the refrigeration system.

For any refrigeration system to operate effectively, it is crucial to ensure that the pressures within the system are adequate to support the necessary thermodynamic processes. The saturation pressure corresponds to the pressure at which a refrigerant transitions between its gas and liquid phases at a given temperature. If the design pressure is lower than the saturation pressure at the expected operating temperatures, the system may not function properly, leading to inefficiencies or even failure to cool.

In this case, the provided temperatures—80°F for the low side and 125°F for the high side—represent a balance that is commonly found in many refrigeration applications. The saturation pressures at these temperatures are established standards that are critical for ensuring that the refrigeration cycle can occur without compromising the integrity of the system's components. By adhering to these saturation pressures, you ensure the system operates within safe and effective limits, keeping both the evaporator and condenser functioning correctly.

Other choices may present saturation pressures at different temperatures, which may not align with conventional operating ranges for many refrigeration systems. Therefore, choosing the correct option aligns with industry practices and standards