What could cause excessive superheat at the evaporator outlet?

Excessive superheat at the evaporator outlet can result from various factors, which makes the option encompassing all these causes the most comprehensive answer. Each factor can lead to conditions that result in higher-than-normal superheat levels.

When considering blocked refrigerant flow, this can occur due to restrictions in the system, such as a clogged filter drier or a malfunctioning expansion valve. When the flow of refrigerant is restricted, less refrigerant enters the evaporator. This leads to insufficient heat absorption and higher superheat as the remaining refrigerant is heated excessively.

Low refrigerant levels can similarly contribute to the problem. In scenarios where the refrigerant charge is insufficient, the evaporator won't be fully flooded with refrigerant liquid. As a consequence, there will be less refrigerant available to absorb heat, causing the refrigerant exiting the evaporator to be at a higher temperature, thus resulting in increased superheat levels.

High ambient temperatures can also play a role. A higher temperature surrounding the evaporator can increase the heat load on the system. In such cases, if the evaporator cannot absorb this additional heat effectively due to insufficient refrigerant flow or levels, it can lead to excessive superheat.

Since all these scenarios can independently or collectively lead to excessive