What might cause low suction pressure in a refrigeration system?

Low suction pressure in a refrigeration system can occur for various reasons, but a TXV (Thermostatic Expansion Valve) that is stuck nearly shut can significantly impact the system's operation. When the TXV is not allowing enough refrigerant to flow into the evaporator coil, the evaporator will not be able to absorb sufficient heat from the surrounding area. This inadequate refrigerant flow leads to less evaporation within the coil, resulting in a drop in suction pressure because the evaporator is not functioning effectively.

By constricting the refrigerant flow, a nearly shut TXV effectively limits the system's ability to relieve vapor pressure, resulting in low suction pressure readings. This condition can severely affect the overall performance of the refrigeration system, leading to inefficient cooling and potential compressor issues due to being starved of refrigerant.

While other options can cause low suction pressure as well, they do so through different mechanisms. For instance, a leak in the system would generally lead to a loss of refrigerant and possibly lower suction pressure, but that is not the primary mechanism involved when considering the specific scenario of a stuck TXV. Understanding the role of the TXV in refrigerant flow makes it clear why this condition can lead to low suction pressure specifically.