What effect does an expansion device that is stuck open have on an evaporator?

When an expansion device is stuck open, it allows an excessive flow of refrigerant into the evaporator. This increased refrigerant flow results in a flooded evaporator, which occurs when liquid refrigerant does not have enough time to evaporate into a gas before it exits the evaporator coil.

In a properly functioning system, the expansion device regulates the amount of refrigerant entering the evaporator, ensuring that it matches the heat load. However, if the device is stuck open, more refrigerant than necessary enters the evaporator coil, leading to an accumulation of liquid refrigerant. This situation can cause reduced efficiency and can even damage the compressor if the liquid refrigerant returns to it.

Furthermore, a flooded evaporator can impede heat transfer, as the coil is not sufficiently vaporized, causing the system to operate improperly. In summary, a stuck-open expansion device results in a flooded evaporator, where excess liquid refrigerant is present, severely impacting the refrigeration cycle and overall system performance.