Condenser flooding is necessary on cooler or cold days to:

Condenser flooding on cooler or cold days is primarily necessary to maintain constant head pressure. In refrigeration systems, particularly those using a vapor-compression cycle, the heat exchanger's pressure is crucial for the system's efficiency and performance.

On cooler days, the ambient temperature decreases, which can lower the pressure within the condenser if not managed properly. By flooding the condenser, the refrigerant flow can be adjusted so that a sufficient amount of refrigerant remains in the condenser coil, maintaining a higher pressure. This ensures that the refrigerant can condense effectively into a liquid, which in turn allows the system to operate efficiently and prevents issues related to low head pressure, such as reduced cooling capacity and potential system instability.

This management of head pressure allows for consistent cooling performance and reduces the risk of operational issues related to fluctuating pressures, which can arise in colder conditions if condensation and flooding are not properly controlled.