The use of variable airflow in air conditioning systems has become a standard expectation rather than just a part of design choices. Variable air volume (VAV) and variable volume/temperature (VVT) require refrigeration capacity modulation in order to operate effectively and reliably. More recently expectations have been set nationwide demanding single zone VAV applications in order to improve operational efficiency.

A VAV system of any kind saves money on the operation of the evaporator fan motor (reduced HP) during part load conditions. This is known in the industry! But did you know the APR Control reduces horsepower requirements on the compressor? Usually this reduction is directly related to reduced airflow. Reducing airflow volume without refrigeration circuit modulation, causes a great deal of stress to be placed upon the refrigeration circuit and compressor. APR Controls can reduce if not eliminate stress on the refrigeration circuit components while reducing power consumption.

Without an APR Control for continuous capacity modulation there is a high likelihood of system short cycling/rapid cycling, coil frosting, duct sweating and inconsistent discharge air temperatures that can lead to an increase of space humidity. Using DX equipment for a VAV system usually results in a mismatch of system capacity to building load. A contributor to this mismatch is that as fan speed varies in relation to building load, the load on the evaporator changes. The APR Control provides flexibility to the refrigeration circuit and system capacity eliminating this problem.

APR Control improves performance by maintaining the evaporator coil at constant temperature. This extends the runtime of the system keeping it in a dehumidifying mode during part-load conditions. The APR Control also provides stable and consistent discharge air temperature, reducing or eliminating the need for reheat. This stability prevents the controls from hunting at the zone level providing improved occupant comfort and decreased commissioning times.

The APR-E, the electrically driven and electronically controlled modulation device, will provide precise temperature control to adjust to different temperature set point demands. APR-E Valves can further enhance VAV systems to comply with today’s energy codes. This gives a system enhanced with the APR-E Valve the ability to operate with a temperature reset control sequence.

The APR Control capacity reduction ratio is usually enough to meet the minimum airflow requirements in most applications.