An office area system must maintain a comfortable temperature based on multiple set points in individual rooms. This complex problem is often solved by installing a system of Variable Air Volume controls on branch outlets. The simplest variable air volume control (VAV) system controls air from a single supply duct and varies the airflow to each zone or room based upon the temperature in the room. A VAV system consists of four basic parts: a thermostat, a precision actuator controlled damper, an airflow sensor, and a controller.
Types of VAV: – By-Pass
Pressure Independent
Constant Air Volume
By-pass
Maxell Variable Air Volume – By-pass is a pressure dependent variable air volume which serves the individual zones while by-passing the unneeded air to the ceiling as it is recirculated back. A VAV system turns out to be a feasible and economical solution when compared to a fan control system.
Pressure Independent 
Maxell Variable Air Volume – Pressure Independent is a pressure independent VAV consists of VAV units connected to the supply air duct where the air volume is supplied by a VFD driven fan motor.
In the case the thermostat [analog] is connected to the VAV, then it delivers a variable air volume within the limits of Vmin to Vmax [values settable in the controller supplied with VAV] with the response to room thermostat demand.
Constant Air Volume
Constant volume of conditioned air is supplied to each VAV unit with variable static pressure. The VAV damper modulates in response to variable static pressure to deliver a constant air volume Vconst. to the conditioned zone by the setpoint value within the limits of Vmin to Vmax.
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