Low primary temperature drop across district heating substations is an undesirable phenomenon observed in the district heating industry. Professionals in the industry have argued that this is caused by inappropriate sizing and controls of district heating substations. The thesis aims to investigate the impact of design and operation parameters on the performance of district heating substations, so that building designers and engineers can potentially better design and operate new and existing district heating substations. The thesis shows that, by developing and using a physical model as a computational tool for sensitivity analysis, different design and operation parameters can be evaluated. This generates insights for energy conserving control strategies to be developed. A preliminary control strategy was proposed for district heating substations, and simulation results show energy saving potentials.