Control apparatus for space cooling system

Abstract

Apparatus for providing integrated control of a space cooling system is disclosed. The apparatus receives inputs from a plurality of temperature sensors, including a temperature sensor for measuring evaporator superheat, space temperature and compressor discharge temperature. The control apparatus incrementally adjusts the position of the cooling system expansion valve to regulate evaporator superheat and compressor discharge temperature and cycles the outdoor condenser fan on and off to raise condenser pressure in response to a low condenser pressure condition. In one embodiment, the cooling system includes a plurality of evaporators and a corresponding plurality of controllers electrically interconnected in a series loop for controlling the expansion valves and defrost heaters associated with the respective evaporators. One of the controllers functions as a master controller and receives inputs from the space temperature sensor and the compressor discharge temperature sensor as well as from the temperature sensors associated with the corresponding evaporator. The master controller activates and deactivates the cooling cycles in response to the inputs from the space temperature sensor. Both the master controller and each slave controller separately control the corresponding expansion valve and defroster. The master controller also initiates the system defrost cycle. However, once the defrost cycle is initiated, each slave controller controls the defrost cycle for its corresponding evaporator.