US Patent 8011196 Refrigerant control of a heat-recovery chiller

A chiller includes a main condenser that has a refrigerant condensate sump with an internal weir or standpipe that maintains at least a minimum liquid seal between the outlets of the main condenser and a heat-recovery condenser. The main condenser is used for normal cooling operation, and the heat-recovery condenser is for supplying an external process with heat that would otherwise be wasted. In addition to providing a liquid seal, the sump and weir combination provides a reliable source of liquid refrigerant to cool the chiller's compressor motor and creates a trap for collecting foreign particles that might exit either of the chiller's two condensers.