Where should noncondensibles be manually purged from in a refrigeration system?

In a refrigeration system, noncondensibles, which are gases that do not condense under the operating conditions of the system, often accumulate in the condenser. Since these noncondensables can affect the efficiency and performance of the system by increasing pressure and lowering the heat exchange capacity, it's important to remove them effectively.

Purging noncondensibles from the highest point of the condenser is the correct approach because noncondensibles tend to rise within the system due to their lower density compared to refrigerants in vapor phase. When purged from the highest point, the noncondensibles can escape more easily, allowing for the removal of these unwanted gases without significantly affecting the refrigerant fluid. This ensures that the refrigeration cycle remains efficient, as the accumulation of noncondensibles at low points can lead to reduced system performance and increased operating pressures.

In contrast, purging from the lowest point would not be effective because noncondensibles would remain trapped in the upper portions of the condenser, leading to insufficient removal and continued performance issues. Similarly, purging from the compressor discharge or the suction line would not be ideal for the same reasons, as these locations do not directly address the accumulated noncondensibles within the condenser where they typically gather.