The APR control provides full-capacity modulation for all sizes of direct-expansion air conditioning systems. 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. According to the manufacturer, the control maintains the system in a dehumidifying mode without risk of coil icing or liquid slugging. 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. 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 as well.
Rawal Devices Inc., 128 F. New Boston St., Woburn, MA 01888; 800-727-6447; 781-933-3306 (fax); email@example.com; www.rawal.com
Rawal Devices Inc.: Air Conditioning Capacity Control
March 19, 2007