Liquid trap for freeze-up protection on air cooled centrifugal chiller

An air cooled centrifugal liquid chiller is disclosed which includes an air cooled condenser exposed to ambient conditions such that, during those times when the temperature of the ambient is at a relatively low level and the chiller is inoperative, refrigerant will tend to migrate to and condense in the air cooled condenser. If this accumulated condensed refrigerant is permitted to then flow by gravity to the evaporator of the chiller, the heat exchange liquid within the tubes thereof may freeze, causing possible damage. In order to prevent this occurrence, the conduit means connecting the air cooled condenser to the evaporator are provided with a trap portion disposed at a level above the maximum level of condensed refrigerant accumulation within the air cooled condenser, which trap portion is vented to a point in the air cooled condenser above said maximum level. In this manner, during those times when the chiller is inoperative, accumulated condensed refrigerant in the air cooled condenser is prevented from passing to the evaporator. In the preferred embodiment, the conduit means connecting the air cooled condenser to the evaporator include a generally inverted U-shaped portion having a bight portion disposed above the maximum level of refrigerant accumulation in order to define the aforesaid trap.