Abstract: A system for minimizing the energy consumption in a central air conditioning unit incorporating a refrigeration unit which is normally in operation to supplement or substitute for the cooling effect of outside air. The system employs sensor to sense the enthalpy of the return air entering the unit from the work space, the outside air entering the unit from the outside, and the washer air discharged into the work space from the unit, and controls the operation of the unit in accordance with the relative levels of enthalpy at these points. The energy content of the discharged washer air may be modified by modulating dampers controlling the proportion of outside and recirculated air, and also by modulating the washer which provides evaporative cooling and, in addition, cooling by refrigeration.

Abstract: An air-conditioning system for a work space in which recirculated air is mixed with outside air and the mixture is passed through a washer. The controls for the system include an absolute moisture controller in the primary air supply downstream from the air washer, a direct-acting humidistat for the room air and a reverse-acting thermostat for the room air. The proportional output signals of the thermostat and humidistat are fed to a high-and-low signals selector which transmits the higher of the two signals to a heating control for the recirculated air and the lower of the two signals to a throttling valve for the air washer. In normal operation, the air washer is fully throttled before the heating control is activated to supply heat to the recirculated air since the heating control is responsive to a pressure above the range of pressures which are effective to modulate the washer sprays.