What causes excess superheat increase on the way to the compressor?

The cause of excess superheat increase on the way to the compressor is primarily due to inadequate insulation on the suction line. When the insulation on the suction line is insufficient or damaged, heat from the surrounding environment can transfer to the refrigerant inside the line. This heating of the refrigerant can lead to a higher superheat level before the refrigerant reaches the compressor.

Superheat is crucial as it ensures that only vapor enters the compressor, preventing potential liquid slugging that could damage the compressor. When the suction line is not properly insulated, the refrigerant absorbs heat, increasing its temperature and causing the superheat to rise excessively. This can lead to inefficiencies in the refrigeration system and impact the overall performance.

The other options, while they may influence the operation of a refrigeration system, don't have the same direct correlation with causing excess superheat in the way that inadequate insulation does. Understanding this relationship helps in diagnosing issues within the refrigeration system effectively.