The APR Control provides full capacity modulation for direct-expansion air conditioning systems of all sizes. Responding quickly to changing conditions, the unit efficiently controls temperature and humidity to maximize comfort and eliminate excessive compressor cycling. Because an air conditioning system equipped with the APR Control continuously monitors the heat content of return air, it is more economical than systems relying only on end-type controls such as thermostats and humidistats. The APR Control maintains the system in a dehumidifying mode without risk of coil icing or liquid slugging. The unit is suitable for VAV systems where fluctuating or reduced air flow across the evaporator can cause coil icing. It is also the suitable for high-percentage makeup-air systems where significant variations in the heat content of outside air can cause unusually frequent system cycling. The APR Control also permits multiple-evaporator zoning with a single condensing unit, even for out-of-the-way or oddly shaped areas with widely differing load conditions. Each evaporator conditions a different zone, reducing ductwork requirements and the cost of air-side controls. No complicated piping or wiring is required.