The APR control provides full-capacity modulation for direct-expansion a/c systems of all sizes. Responding to changing conditions, the unit controls temperature and humidity to maximize comfort and eliminate excessive compressor cycling. The unit's desuperheating chamber modulates the a/c system's capacity by varying refrigerant flow according to suction pressure, which changes with the temperature of air crossing the evaporator coil. The control maintains the system in a dehumidifying mode without risk of coil icing or liquid slugging, said the manufacturer. The control permits multiple-evaporator zoning with a single condensing unit. Each evaporator conditions a different zone, reducing ductwork requirements and the cost of airside controls. The control can be used for variable air volume systems where fluctuating or reduced airflow across the evaporator can cause coil icing. Also, it can be used for high-percentage make-up air systems where significant variations in the heat content of outside air can cause unusually frequent system cycling.

Rawal Devices Inc., 128 F. New Boston St., Woburn, MA 01888; 800-727-6447; 781-933-3306 (fax);;

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