Essentially, the APR Control operates as an external modulating compressor capacity unloader. As the heat content of return air drops, so does the system’s suction pressure. The APR Control senses that drop in suction pressure, opening the APR Control to maintain a suction pressure setpoint.
When the APR Control begins to function (modulates) to maintain suction pressure setpoint, it will start diverting discharge gas from the compressor through our CRR valve. The diverted gas is sent into our Desuperheating chamber, where it is cooled down and sent back into the compressor via the suction line as a cooler gas. If the Desuperheating chamber can’t cool the gas down enough, due to a high rate of capacity modulation, the liquid injection valves will inject a tiny amount of liquid to maintain no more than a 20(degree) superheat at the compressor.
This diversion of mass flow around the compressor varies the amount of refrigerant through the TXV, evaporator, and condenser. This varied amount of refrigerant allows the system to match the capacity of refrigeration to the actual heat load entering the system.
By matching the capacity to the load, the APR Control can extend the run time of the compressor, proven to be very effective in dehumidification. This load matching ability serves as a benefit for VAV systems, MUA, as well as various other systems and applications.