This application discloses a control logic for maintaining a proper solution concentration within an absorption chiller. Further, safeguards are added to a system control to ensure robust operation when operated in a co-generation application with a heat source such as a micro-turbine, a reciprocating engine, etc. In such applications, in proper management of the heat flow into the chiller from such sources can result in crystallization of the absorption solution, which would be undesirable. Inventive control logic works to minimize such occurrences.