A poor control sequence can completely neuter the best equipment selection, layout, and painstaking coordination. On the other side of things, a great Sequence can sometimes mask design deficiencies. Along with specifications and control diagrams, the control sequences is where the rubber meets the road, so to speak in an HVAC design. It is through a Sequence that all of the required and desired functionality is conveyed to the BAS contractor. This includes different modes of operation (think heating versus cooling), allowable operator overrides, alarms, etc. It can be a time-consuming process to write a robust Sequence that delivers the strikes the right balance between useful functionality & frivolous modes, actionable notifications & nuisance alarms, robust operation & susceptibility to getting caught in logic loops.