When two machines serve the same room they could split its load in shares, and a share is always wrong for one of them: the load being divided is sensible only, and the machine doing the latent work — a DOAS — must not be throttled to a fraction. So machines take a room in turn instead. The leading machine is offered the whole demand; the next is offered what the lead did not actually deliver; equals divide what reaches them.

Declared rather than inferred, because nothing in a graph says which machine is the outside-air unit. The rule has a moisture side too: the machine behind a lead is asked for the supply humidity that lands the room on its bound beside the air the lead delivered, so a DOAS carries the latent and the handler behind it only the remainder. One wart to know: a lead's own unmet count reads hours it could not cover alone — the room's count is the comfort truth.

Open the builder — the examples under ＋ Open include a machine of this kind, and a building tab runs it against a year of weather.

Other terms

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 · Category · Nested system · Design point and TMY year · Superheat · Subcooling · Sensible heat ratio (SHR) · Bypass factor · Wet-bulb temperature · Dew point · COP and EER · Compressor map · Evaporating and condensing temperature · Range and approach · Heat-recovery (three-pipe) VRF · Typical meteorological year (TMY)