The main objective of this work is to study the influence of design and operating conditions on the divided wall column (DWC) controllability. Firstly, two designs for which the total distillation cost is minimised are compared. For each design, different optimal reflux to minimum reflux ratio is assumed. Secondly, three non-optimal designs are compared with an optimal one. Adding trays to different column sections, the distribution of the distillation effort is changed. The effect of this change on the controllability is studied. The DWC has extra operation degrees of freedom and the operation that minimises the boilup is searched. The influence of the operating conditions over the controllability is studied comparing optimal and non-optimal nominal operations.