VAV Air Handlers are ideal for providing zones in a commercial building. Office space typically has several offices and open areas that need to be conditioned for the comfort of the people working in those areas or offices. By installing VAV boxes and zoning the ductwork from those VAV boxes these areas and offices can be kept comfortable using a VAV air handler system. More on how VAV boxes work.
VAV Air Handler | HVAC Zoning
Depending on what the thermostat temperature set point is and the temperature in the space will determine the amount of airflow the space will receive from the VAV box. Additionally, A box with reheat will energize the heat strips or open the actuator for the hot water coil if the set point and room temperatures call for the reheat to provide heat to the space (If the VAV box is equipped with reheat).
HVAC Zoning - Primary Air
The primary air is typically conditioned at the VAV air handler to provide a constant set point of whatever the engineer determines the set point needs to be maintained at. Control systems with trim and respond capabilities can modulate the primary air set point up and down depending on the demand. If the VAV boxes are all calling for cooling the program responds by lowering the discharge air temperature set point on the air handler to say 50 degrees Fahrenheit.
If the VAVs are calling for heat then the control program responds by increasing the discharge air temperature set point to say 65 degrees Fahrenheit. Trim and respond is not an option that comes with all control programs or widely used in AHU applications however if one was to crunch the numbers one can see where a trim and respond program can save a lot of money by way of energy dollars by automatically changing the discharge air temperature set point on the VAV air handler based on load demand.
The two VAV’s pictured to the left are VAV boxes that will get their primary air from the VAV air handler in the zone which they are installed. They are in the construction phase being stored in an empty room.
VAV Air Handler and HVAC Zoning