VAV or Variable Air Volume systems, are used to control both the ventilation and temperature to satisfy the requirements of a building. Central VAV systems are

considered to be the most energy efficient method to air condition buildings. By designing central systems instead of distributed systems, a greater efficiency can

be obtained.

The efficiency comes from utilizing larger fans and larger chillers which have much higher efficiencies than small motors and distributed air-cooled chillers. Savings

are also seen from the decreased maintenance requirements.

2.7.14 The AF-600 FP Solution

While dampers and IGVs work to maintain a constant pressure in the ductwork, a frequency converter solution saves much more energy and reduces the complexity

of the installation. Instead of creating an artificial pressure drop or causing a decrease in fan efficiency, the frequency converter decreases the speed of the fan

to provide the flow and pressure required by the system.

Centrifugal devices such as fans behave according to the centrifugal laws. This means the fans decrease the pressure and flow they produce as their speed is

reduced. Their power consumption is thereby significantly reduced.

The return fan is frequently controlled to maintain a fixed difference in airflow between the supply and return. The advanced PID controller of the HVAC frequency

converter can be used to eliminate the need for additional controllers.

Cooling coil

Heating coil

Filter

Pressure

signal

VAV boxes

Supply fan

Pressure

transmitter

Flow

Return fan