By: Rawal  09-12-2011
Keywords: humidity control

Rawal Devices – Humidity control – APR Control

There are no specialized tools required to install the APR Control – only the gauges and the usual tools that a refrigeration mechanic would have on his truck.

It requires soft soldering or braising – low-temperature (silver bearing) soft solder similar to stay bright #8 (with a 535° F melting point) or 15% silver braising rod. Please note that at all times, for all types of APR Controls, it is necessary to protect the valves of the APR Control from excessive heat associated with this work. Please wrap the valves with wet rags when soldering.

Normal Installation time is usually 4 to 6 hours for an experienced mechanic, with more time required for those who are new to the APR Control. Allowing some time for adjustment can be helpful.

We strongly recommend isolation valves to assist with trouble shooting the installation, as well as charging the system, and adjustment during the initial setup of the equipment.

APR Control Installation Resources and Downloads

Keywords: humidity control

Other products and services from Rawal


APR Control – Operational and Functional Description

The difference in system BTU capacity and the current BTU load is continually being bypassed in the form of hot gas through the APR Control’s desuperheating chamber and into the suction line at the compressor. The increase in suction pressure resulting from the hot gas and suction mix reduces the compression differential in the compressor, causing a decrease in required compressor horsepower.


APR Control –System and User Benefits

In the design of small direct expansion systems, the APR Control gives the contractor or engineer the opportunity to select equipment based on maximum possible load and have continuous capacity modulation down to the minimum required load – all at increased system efficiencies. Drives the system into a constant temperature & stabilized humidity mode by creating long operating cycles.



In addition, they contain charts with control dimensions as well as sizes for the connections to the air conditioning system's hot gas, liquid, and suction lines. Rawal Devices’ specification sheets show the models and capacities of the APR Controls. Please contact Rawal Devices engineers if you have any questions. Rawal Devices – Humidity control – APR Control.


Selection Criteria

Most systems that employ a low minimum of outside air will benefit from about 50% modulation on a simple single-stage system, or even on the lead stage/circuit of a simple multiple-stage system. We are pleased to assist both new and long-term customers with selection of the best APR Control model (percentage of modulation) for their particular application.



By matching system capacity to continuously changing load conditions, the APR Control-enhanced system is able to maintain better comfort conditions, as well as provide a number of unique solutions that standard air conditioning systems are unable to achieve. From residences to hospitals, computer rooms to offices, pharmaceutical clean rooms to manufacturing facilities, the APR Control has always provided the solution.


Air Conditioning SystemsThe Inevitable Design Flaw

The air conditioning system is “short cycling,” meaning that for each 5 minutes the air conditioning system is actively cooling the space, there are 20 minutes when the system is merely recirculating air and not dehumidifying it. A standard thermostat, when set at 70°F, will turn the air conditioning on at 72°F and cool the space, at full capacity, until the temperature is 68°F and the thermostat is satisfied.