If the TXV is adjusted correctly, it will close and remain closed whenever the compressor is:

The correct response highlights the importance of the thermostatic expansion valve (TXV) in regulating the flow of refrigerant to the evaporator coil in relation to the compressor's operation. When the compressor is idle, there is no suction pressure being generated, which leads to a reduction in the pressure difference across the TXV. In this state, the TXV senses that the evaporator coil has sufficient refrigerant and, to prevent flooding or liquid refrigerant from entering the compressor, it will close and remain closed. This functionality is crucial for protecting the compressor and ensuring efficient system operation.

In contrast, when the compressor is running, the TXV is actively responding to the cooling demand by adjusting the flow of refrigerant to maintain optimal operating conditions. Additionally, if the compressor is cold (which generally indicates that it is not operating efficiently) the TXV may not fully close as it may still need to allow some refrigerant to flow based on system needs. Thus, the condition of the TXV being fully closed is specifically tied to the state of the compressor being idle.