How do I troubleshoot or diagnose a system with the APR Control installed, but there are no Isolation Ball Valves?

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Diagnosing the system without the isolation ball valves, is extremely time consuming and difficult. Evacuating the system, installing the ball valves, and recharging may be more efficient with your time and eventual accuracy of your diagnosis.

If installing ball valves is not feasible or possible, then consult with our Senior Technical Engineer by calling Rawal Devices (800) 727 – 6447.

If you are on the job site dealing with this issue, please let our team know and you will speak with a real person immediately to solve your issue.

Will the APR Control cause high head pressure issues?

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No. The APR Control when active will reduce the head pressure and increase subcooling. In the 30+ years of Rawal Devices operating, there has never been an instance where the APR Control increased head pressure.

APR Control appears to be operating all of the time, what do I do?

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When we receive this phone call at Rawal Devices, 98% of the time this is caused by a leak in the system or the system having a low charge. We recommend isolating the APR Control by closing all of the ball valves, and diagnosing the system per manufacturer’s recommendations.

The other possibility is that the evaporator is in a constant low load condition where modulation is needed. For example, low airflow (below 375 cfm/ton), dirty filters, loose belt, extremely low room setpoint (below 68 deg), high percentage outdoor air during low ambient conditions, etc. In these conditions it is beneficial for the APR Control to operate to prevent floodback and icing.

Will I need to adjust the APR Control?

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The APR Control is shipped from the Factory set for approximately 40 degrees F. evaporator coil temperature, or to start opening at 118psi (in an R-410A system). We have found this to be an excellent setpoint for most applications, and will not require adjusting the APR Control.

However, every job, system, and application is unique. Our rule of thumb is to allow the APR Control to provide maximum modulation before compressor termination. If the runtime is inadequate or low load operation does not cause suction pressure to fall low enough, you may need to adjust the APR Control Compressor Ratio Reduction Valve (CRR Valve).

Please call Rawal Devices Engineer’s (800-727-6447) at the factory prior to attempting any adjustment. For more information see our Installation page.

The AC unit is not operating correctly, how do I troubleshoot with an APR Control in the system?

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The APR Control must be isolated during system troubleshooting. Otherwise, you will not be able to judge what the unit is doing when an APR control is operating. You will need to isolate the control from the system with either a ball valve or solenoid valve (with manual stem) in the suction line between the outlet of the control and the “T” on the suction line. It is imperative that isolation ball valves be installed on all connections to the APR Control device. Without these isolation valves the APR Control can mask several types of issues that would otherwise be easily diagnosed.