Design point and TMY year. One set of entering conditions the Design tab solves at; a typical meteorological year is the 8 760 hours the Simulate tab runs against. A solve is one condition; a simulation is a year of them.
A design point is one set of entering conditions — 35 °C outside, 24 °C return, a duty — and a solve at it answers what the machine does there: the coil's leaving air, the compressor's evaporating and condensing temperatures, the COP. It is what a catalog rating is, and what a selection is made on. A typical meteorological year is 8 760 of those conditions in the order a real year serves them, assembled by PVGIS from decades of measurements so that no month is unusually mild or harsh.
A simulation runs the machine — or the building — against that year, hour by hour, with the control deciding what runs and the rooms remembering what happened the hour before. The design point tells you whether the machine can; the year tells you what it costs, how often it falls short, and which day decides its size. HVAC Builder's Design tab is the first, its Simulate tab the second, and the same graph feeds both.
Open the builder — the examples in the Design tab's sources list include a machine of this kind, and the Simulate tab runs it against a year of weather.
DOAS — dedicated outside-air system · SZVAV — single-zone variable air volume · VAV terminal box · Economiser · Waterside economiser · Demand-controlled ventilation · Face-and-bypass · Head-pressure control · Humidity ceiling and floor · Cycling and modulation · Coupling · Priority · Category · Nested system