Dual Duct VAV

Stencil: Zone HVAC Stencil: Grp-Dual Duct VAV

Type: Air Terminal

Sub Type: AirTerminal Dual Duct VAV

EnergyPlus IDF Objects

EnergyPlus Object - AirTerminal:DualDuct:VAV

AirTerminal:DualDuct:VAV (i.e., Dual duct variable air volume (DDVAV)) systems are used to obtain zone temperature control by mixing the cold and warm air in various volume combinations. The fan is sized for the anticipated maximum coincident hot or cold volume, not the sum of the instantaneous peaks. This system has an advantage of a true single path VAV system, except for warm port leakage. When cold air is modulated for control before mixing, it operates similar to the VAV induction when mixing occurs without hot deck reheat. It is similar to a reheat system when mixing occurs while the hot deck is using the reheat coil. It uses more energy than a true VAV system, but less than a constant volume dual duct system.

Component Properties

The table shows the properties that are displayed when the component is selected while in diagram mode. The second column shows the selection options available that are dictated by EnergyPlus or it shows the source for the library entries that are displayed in the drop down list.

Property Name	Value Sources/Options
Name	Simergy provides unique name (editable)
Availability Schedule Name	Schedules
Maximum Damper Air Flow Rate	0-Min; Autosize
Zone Minimum Air Flow Fraction	0 to 1; 0.2 Default
Design Specification Outdoor Air Object Name	SizingParams/HVACDesign/OutdoorAirDesignSpec

Name

Simergy automatically defines a unique name for each component. This can be changed by the user if desired.

Field: Availability Schedule Name

Schedule that this component will operate or is available to operate.

Field: Maximum Damper Air Flow Rate

The design maximum volume flow rate (m³/sec) specified for DDVAV ADU.

Field: Zone Minimum Air Flow Fraction

The minimum flow rate to the zone while the system is operating, specified as a fraction of the Max Damper Air Flow Rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants.

Field: Design Specification Outdoor Air Object Name

This alpha field specifies the name of a DesignSpecification:OutdoorAir object. When this field is used, the terminal unit will increase flow as needed to meet this outdoor air requirement. If Outdoor Air Flow per Person is non-zero, then the outdoor air requirement will be computed 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 field is blank, then the terminal unit will not be controlled for outdoor air flow. See documentation for the zone HVAC outdoor air object for further information (Ref DesignSpecification:OutdoorAir).

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