Precise Temperature & Humidity Control Solution

Precise Temperature & Humidity Control Solution

Precise and stable temperature with the APR Control

Many applications, including surgery suites, clean rooms, high-precision manufacturing, etc., have tight temperature and humidity requirements that can benefit from the addition of the APR Control. By providing continuous capacity modulation to match changing load conditions, the APR Control has helped correct many under-performing systems.


At Angiotech manufacturing, cleanrooms were experiencing humidity that exceeded the specifications of their manufacturing process. When the temperature/humidity variations caused the cleanroom to be out of compliance with the company’s own stringent standards usable products could not be produced, potentially impacting the company’s sales and delivery.

Angiotech specifications and performance requirements lead to several compressors failing while attempting to hold temperature and humidity constant. The installation of apr controls reduced the cycling conditions, eliminated compressor loss, and most importantly, corrected the humidity problems allowing for uninterrupted production.

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Precise discharge temperature control with the electronic APR-E Valve

ASHRAE has approved several research projects to test and demonstrate the use of new technologies in controlled environments. Rawal devices had the opportunity to have the APR-E® Valve installed on an ASHRAE sponsored research project for cleanroom air quality and energy saving standards.

On this particular research project (rp-1604), an automated cleanroom test lab was built in Farmington Hills, Michigan to develop ASHRAE standards for all cleanrooms. Ashrae will use this cleanroom lab for new technology demonstrations as well as making it accessible to ashrae members.

The apr-e® valve is an electrically driven, electronically controlled, external compressor unloading device – popularly used as a discharge air controller on many staged dx systems. The field-proven electronic apr-e valve provides a unique solution for maintaining stability and precise control of temperature. Resetting the discharge air temperature based on space conditions or energy requirements is becoming the rule rather than the exception. With the electrically driven & electronically controlled apr-e valve, engineers now have the ability to control any single or multi-stage dx system to a precise discharge air setpoint. Equipment or system design limitations make direct discharge air control of this type almost impossible to achieve otherwise.

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The Rawal APR Control is a variable capacity enhancement to DX HVAC systems.