Improving degree of superheat control in a direct expansion (DX) air conditioning (A/C) system

In a direct expansion (DX) air conditioning (A/C) system having a variable-speed compressor and supply fan, the degree of refrigerant superheat regulated by a built-in conventional proportional–integral–derivative (PID) controller would experience fluctuation, after the speeds of both compressor and supply fan were regulated by a capacity controller. This would impact the operating efficiency and stability of the DX A/C system. Therefore a new DS controller, which was intended for improving the DS control performance when the fluctuation of operating DS was resulted from speed changes, has been developed and its controllability tested. The test results showed that this new DS controller, which replaced the conventional PID DS controller, can significantly improve DS control performance after speed changes while indoor air temperature and humidity were controlled to their respective settings. With the improved DS control performance, the operating efficiency and stability of the DX A/Csystem were also enhanced.