Variable air volume (VAV) systems control the dry-bulb temperature inside a zone by varying the supply air volume instead of the air temperature. At full cooling the VAV damper is fully open supplying the specified maximum air flow rate. As the cooling load decreases, the damper closes until it reaches the minimum stop specified by the zone minimum air flow fraction.
VAV systems can be used for interior or perimeter zones with a common fan system and air temperature control. The VAV concept may vary according to the VAV box locations and air temperature controls. Heating can be provided if necessary by use of baseboard.
This is a read-only label that is automatically generated by the software and which incorporates the name of the zone in which the ADU is located.
The design maximum volume flow rate (m3/s or ft3/min) specified for VAV ADU. This is auto-sizable.
This is used to select how the software will determine the minimum flow rate to the zone while the system is operating. There are 5 choices for selecting how the minimum flow rate is specified:
If 1‑Constant is selected for the Zone minimum air flow method, then this setting is used to define the minimum flow rate to the zone specified as a fraction of the maximum air flow rate while the system is operating. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants.
If 2‑Fixed flow rate is selected for the Zone minimum air flow method, then this setting is used to define the minimum flow rate (m3/s or ft3/min) to the zone specified as a fixed air flow rate while the system is operating. The minimum air flow rate is normally specified to meet the minimum ventilation requirement for the occupants.
If 3‑Scheduled is selected for the Zone minimum air flow method, then this setting is used to define the schedule that determines the value of the minimum air flow fraction. The schedule should contain fractions from 0.0 to 1.0. These values will define the minimum flow rate to the zone while the system is operating, specified as a fraction of the maximum air flow rate.
If this option is selected, the terminal unit will increase flow as needed to meet the outdoor air requirement specified on the HVAC zone dialog. If Outdoor air flow per person is non-zero, then the outdoor air requirement will be calculated by the software based on the current number of occupants in the zone. At no time will the supply air flow rate exceed the value for Maximum air flow rate. If this option is not selected, then the terminal unit will not be controlled for outdoor air flow.
This is the schedule that determines whether or not the unit is available for each timestep of the simulation. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the timestep . A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the timestep.