What additional component is included in heat pump systems with a thermostatic expansion valve at each coil?

In heat pump systems that utilize a thermostatic expansion valve (TXV) at each coil, a by-pass line with check valves serves an essential function. The TXV regulates the refrigerant flow based on the cooling demand, ensuring that the right amount of refrigerant is delivered to the evaporator coil for optimal heat exchange.

The addition of a by-pass line allows for continuous circulation of refrigerant, particularly in situations where the demand for cooling or heating fluctuates. This component helps to maintain efficiency and prevents potential issues like refrigerant starvation or flooding of the coil. The presence of check valves ensures that refrigerant can flow in the appropriate direction, which is crucial for the proper functioning of the system, especially when it is operating in different modes (heating or cooling).

The other options, while related to heat pump systems, serve different purposes. A liquid reservoir typically manages refrigerant levels, an accumulator tank is used for managing liquid refrigerant and preventing compressor damage, and a filter drier is essential for removing moisture and contaminants from the refrigerant. However, none of these components specifically address the dynamic control of refrigerant flow in conjunction with a TXV at each coil like a by-pass line with check valves does.