What design must liquid line filter-driers have if used on a heat pump system without check valves?

In a heat pump system without check valves, the use of a bi-flow design for liquid line filter-driers is essential. This design allows the filter-drier to effectively manage refrigerant flow in both directions, which is necessary because heat pumps operate by reversing the flow of refrigerant depending on whether they are in heating or cooling mode.

In heating mode, refrigerant flows in one direction, while in cooling mode, it flows in the opposite direction. A bi-flow filter-drier will facilitate the filtration and drying of refrigerant regardless of the direction of flow, preventing issues such as contamination and moisture from accumulating in the system. This capability is crucial for maintaining the reliability and efficiency of the heat pump system, ensuring optimal operation and longevity.

Other designs, such as single-flow or multi-stage, would not adequately accommodate the bidirectional flow required in heat pump applications without check valves, potentially leading to mechanical failures or decreased performance.