to the flow chart of fig2 in decision block 58 controller 52 compares the actual chilled water temperature to an established chilled water temperature target or set point controller 52 can determine the actual chilled water temperature from a temperature sensor 60 on supply line 38 and or individual temperature sensors 62 and 64 associated with chillers 14 and 16 respectively controller 52 may receive temperature indicating signals 66 68 and 70 from temperature sensors 60 62 and 64 respectively establishing the chilled water temperature target can be performed through a conventional input device such as a keyboard dial etc if block 58 determines that the actual chilled water temperature is less than or equal to the set point control decision block 70 determines whether chiller 14 should continue operating provided it was already operating if chiller 14 is operating below its predetermined minimum capacity control block 72 deactivates chiller 14 and control returns to decision block 58 otherwise control shifts to control block 74 which compares an actual chilled water pressure to an established chilled water pressure target establishing the chilled water pressure target can be a performed at any time before or after the installation of system 10 and may be performed through a conventional input device such as a keyboard dial etc controller 52 can determine the actual chilled water pressure from a pressure sensor 76 sensing pressure of water entering chiller 14 a pressure sensor 78 sensing pressure of water entering chiller 16 a pressure sensor 80 sensing the pressure of water leaving chiller 14 a pressure sensor 82 sensing the pressure of water leaving chiller 16 a pressure sensor 84 sensing the pressure of water.