Heat-recovery (three-pipe) VRF. Some indoor units cool while others heat on one outdoor unit, the heat moved between rooms rather than rejected. The clinic case measures it over a year.
A variable-refrigerant-flow system runs several indoor units on one outdoor unit through a shared refrigerant line. A two-pipe system has one direction at a time — every indoor unit cools, or every one heats. A heat-recovery, or three-pipe, system lets some rooms cool while others heat: the heat taken from a glazed south office is moved to a north waiting room instead of being rejected outdoors, and the outdoor coil handles only the difference. In a building whose rooms disagree by kilowatts — a clinic in spring, an office with a server room — the compressor works for the larger side and the smaller side's heat comes nearly free.
AHRI 1230 rates such a system on a simultaneous cooling-and-heating efficiency, the two outputs summed over the power, which is the sum of the two coefficients of performance. This model runs a heat-recovery block with both ends pinned by their coils, the recovered heat credited to the smaller side and the outdoor coil facing the way the larger side needs; the worked clinic case measures what the recovery is worth over a year. What decides the size of a VRF design is usually the indoor unit's ceiling rather than the outdoor unit's, which the same case shows.
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 · 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 · Typical meteorological year (TMY)