What is the most likely cause of high discharge pressure and high normal subcooling in a refrigeration system controlled by a TEV?

The presence of high discharge pressure alongside high normal subcooling in a refrigeration system that is managed by a thermal expansion valve (TEV) strongly suggests refrigerant overcharge.

In a properly functioning system, the TEV regulates the flow of refrigerant into the evaporator based on the temperature and pressure conditions in the system. When there is an overcharge of refrigerant, it leads to excessive refrigerant being pushed through the system. This condition results in increased pressure in the discharge line because the compressor is working to handle a greater volume of refrigerant than it is designed for.

Additionally, high subcooling indicates that the refrigerant is in a liquid state at temperatures below its saturation point rather than vaporizing into gas, which is typical when there is an excess of liquid refrigerant remaining in the condenser outlet. This too correlates with overcharging, where the additional refrigerant does not have a place to expand properly into vapor once it exits the condenser.

Thus, the combination of high discharge pressure and high normal subcooling strongly points towards a refrigeration system that is overcharged with refrigerant, leading to inefficient system operation and potential damage if not corrected.