An optimal combination of the characteristics of an air conditioning system and the control strategy is necessary to minimize costs and the energy demand. Therefore a sequential control for such a system was developed, tested by simulation and implemented in an existing plant. The simulation runs have been done with TRNSYS.For the sake of comparison, an optimized control was calculated using a nonlinear optimization method. For this purpose, TRNSYS had to be combined with MATLAB which includes some optimization
tools.