Many large refrigeration systems, such as those used in supermarkets, are designed to use outdoor air-cooled condensers. The benefits of using outdoor air-cooled condensers are numerous, including minimal operating costs as compared to water-cooled condensers. Associated maintenance costs can also be much lower. There is also an added benefit to free subcooling and lower condensing pressures during low ambient conditions.
However, there is a downside to this added benefit: If the condensing pressure falls too low, it will cause some system problems. One major problem that could develop is that the metering devices at the refrigerated cases will not be fed properly. Typically, thermostatic expansion valves (TXVs) are used as metering devices. A TXV should have a full column of liquid at its inlet.