Abstract: A system for meeting building air conditioning load conditions by optimally selecting a combination of chillers having dissimilar efficiency characteristics, the system having a load sensor for sensing building load a refrigerant head sensor for sensing refrigerant head of the chillers, and a controller connected to the load sensor and to the refrigerant head sensor for sorting the chillers according to their efficiency characteristics data with the chiller having a minimum kw/ton versus capacity point being ranked first and for selecting a combination of the chillers which will require a minimum energy input to meet building load conditions.

Abstract: A control system for minimizing the total energy consumed by an air conditioning system of a building is disclosed having a sensor for sensing the energy expended by the fan of the air conditioning system, a sensor for sensing the energy expended by the chiller of the air conditioning system, and a controller responsive to the fan energy sensor and the chiller energy sensor for controlling the air conditioning system so that the total energy consumed by the fan and chiller systems is minimized.

Abstract: An air conditioning control system is disclosed for controlling a refrigeration unit located in a building which has both interior zones and exterior zones, the refrigeration unit being capable of supplying both chilled water for cooling and hot water for heating. The hot water temperature is controlled by first controlling the amount of heat rejected by a cooling tower, then by controlling the position of an outdoor air damper as a source of free cooling, then by overriding both the chilled water and hot water temperature controllers and finally by controlling the amount of fuel heat supplied to the hot water. The chilled water temperature controller is overridden to lower the chilled water temperature thus increasing the rejected heat from the refrigeration unit. The hot water temperature controller is overridden to increase the rejected heat supplied by the refrigeration unit.

Abstract: An optimization system for switching between plural parallel connected chillers in a refrigeration system is disclosed which system establishes optimized changeover criteria based upon the design refrigerant head for the chillers, the minimum refrigerant head for the chillers, the capacity of the chillers at design head and the capacity of the chillers at minimum head, and which system, using these criteria, calculates optimized switchover capacity as a function of the present actual refrigerant head. The system then compares the optimized switchover capacity to the present building load and, if the capacity is insufficient to meet the building load, an additional chiller is switched in and, if the optimized switchover capacity is greater than the building load and more than one chiller is operating, one of the chillers is disconnected.

Abstract: In a system for limiting power consumption during peak power consuming periods, a proportional demand limit controller is disclosed having a condition sensor for sensing the condition of air being supplied to a space, a reset circuit responsive to the condition sensor for controlling a load connected thereto for in turn controlling the condition of the air being supplied to the space, and a proportional demand controller for sensing load consumption of the loads within a building and for resetting the reset circuit in a manner to maintain the power consumption of the building loads below a predetermined demand limit.

Abstract: In an air conditioning system having both a hot deck for heating air and a cold deck for cooling air, both decks being supplied by a supply duct, a control system is disclosed for minimizing the total cost of heating the air in the hot deck and cooling the air in the cold deck by measuring the amount of heating done in the hot deck and deriving the heating cost therefrom, measuring the amount of cooling done in the cold deck and deriving the cooling cost therefrom, and controlling the temperature of the air in the supply duct until the heating cost equals the cooling cost to thereby minimize the total heating and cooling costs.

Abstract: In an air conditioning system wherein the outdoor air and recirculated air mixing dampers are operated to control the volume and condition, such as temperature, of the mixture of outdoor air and return air to be discharged to at least one zone, a control apparatus is disclosed having sensors for sensing the condition and volume of the mixture and a control system responsive to the sensors for controlling the operation of the outdoor air and recirculated air dampers for maintaining a predetermined condition and a predetermined volume of the mixture. In addition, an exhaust air damper may also be provided, controlled by the control system, for regulating the amount of air returned for the system.