Which situation could lead to immediate refrigeration efficiency issues?

High pressure ratio can lead to immediate refrigeration efficiency issues due to its impact on the system's performance. In refrigeration systems, the pressure ratio is the ratio of the pressure in the condenser to the pressure in the evaporator. An excessively high pressure ratio indicates that the difference between the condensing pressure and the evaporating pressure is greater than optimal, which can cause inefficiencies in heat exchange and the overall cycle.

When the pressure ratio is too high, it means the compressor must work harder to compress the refrigerant, leading to increased energy consumption and reduced capacity. This directly affects the efficiency of the refrigeration system, resulting in higher operational costs and the potential for overheating or other operational failures.

In contrast, while excessive oil, high ambient temperatures, and too much refrigerant can also affect efficiency, they typically do not lead to as immediate or drastic issues as a consistently high pressure ratio. For instance, excessive oil can cause lubrication problems over time, high ambient temperatures may result in performance drops in heat exchange but won’t instantly affect the pressure ratio, and too much refrigerant can cause liquid floodback, which also does not usually create an immediate drop in efficiency compared to an elevated pressure ratio situation.