The APR Control is a highly effective solution in certain situations where AC energy efficiency must be improved. As a solution for oversized systems and part-load control needs, standard field-installed hot gas bypass to the evaporator coil is often used to shed system capacity. The APR Control has shown to be far more responsive and smooth in its operation. The device provided 12% more AC energy efficiency (under run conditions that approximated various part-load scenarios) in testing conducted by Underwriters Labs in Texas.
The APR Control modulates systems operating in part load, reducing the need for reheat. Since humidity levels are constant and low, thermostats can be set at a higher temperature resulting in similar comfort levels. The U.S. Department of Energy estimates that each degree of temperature increase (when cooling) translates into 5% to 7% of energy savings.
"We have a 35-ton package rooftop air conditioning unit on our county library that was grossly oversized and therefore would not dehumidify the library sufficiently. Books were molding and it was very uncomfortable, even though the temperature was being maintained. The first attempt to fix this problem was to add electric strip heat to “false load” the unit to increase the runtime in the cooling cycle. This worked as far as dehumidifying the library, but the electric bill skyrocketed. We then installed a Rawal device. The APR Control has performed wonderfully and has allowed us to shut off the electric strip heat, greatly reducing the electric bill while at the same time maintaining humidity and temperature better than with strip heat. We are very pleased with the results and are about to order three more Rawal devices." (HVAC department manager for firm servicing library in Alabama)
Finally, there is a benefit to AC energy efficiency when we compare the installation of the APR Control to a system using hot gas reheat. This benefit derives from reduced static pressure on the fan operation, which is a constant cost, and on the refrigeration circuit where the loss of performance in the circuit and cooling capacity in adding hot gas to the air stream while attempting to enact cooling reduces overall system efficiency for the sake of dehumidification.