What is the purpose of a check valve in the suction line of the lowest temperature coil in a multiple evaporator system?

The purpose of a check valve in the suction line of the lowest temperature coil in a multiple evaporator system is primarily to prevent refrigerant migration. In a refrigeration system, especially in configurations with multiple evaporators, the risk of refrigerant from the warmer evaporators flowing back into the suction line of the colder evaporator is present. This migration can cause inefficiencies and operational issues since the warmer refrigerant might not effectively absorb heat, reducing the system's overall effectiveness.

By installing a check valve, the refrigerant flow is restricted in one direction, allowing it to return to the compressor from the coil it is meant to service while preventing backflow from higher temperature evaporators. This ensures that each evaporator operates efficiently at its designated temperature, maintaining optimal performance across the system.

While refrigerant can flow freely in one direction with the check valve open, the essential function here is to safeguard against unintended flow into the lower temperature coil, thus enhancing the efficiency and reliability of the refrigeration system.