Download VAV Terminal Control Applications Application Note

VAV Terminal Controller Applications Application Note
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Key Concepts
Variable Air Volume (VAV) Controller
The Variable Air Volume (VAV) controller is an electronic device for
digital control of single duct, dual duct, fan powered, and
supply/exhaust VAV terminal configurations. Along with the control
capability of the VAV box, the controller can also integrate the control
of the room or zone baseboard heat and lighting logic. You may use
the VAV as a standalone controller or connected to the Metasys®
Network through a Network Control Module (NCM), Metasys
Companion™/Facilitator™, or N30 Supervisory Controller.
When connected to the Metasys Network, the VAV provides all point
and control information to the rest of the network. The devices
communicate through the N2 Bus.
HVAC PRO™ Release 6.00 or later allows you to configure the
Variable Air Volume controller with more ease, simplicity, and
application flexibility than ever before. Refer to the Getting Started on
HVAC PRO chapter of the User’s Guide to HVAC PRO (LIT-6375040)
for information on using the windows environment, general
information pertaining to starting HVAC PRO, and hardware/software
requirements.
HVAC PRO Release 6.00 or later allows a VAV controller application
to be downloaded with one sideloop. A sideloop is a control loop
where an input controls an unused output, in addition to the VAV
controller’s main strategy.
For example, you may want to control a humidifier based on return air
humidity. Since the VAV controller does not offer a humidity loop, a
sideloop could accomplish this task. This sideloop strategy could
provide an occupied setpoint and an optional unoccupied setpoint.
Moreover, you could disable the output (either from the On status of
the controller’s Shutdown mode or the Off status of a binary input
interlock) in order to prevent the humidifier from operating when no
air is flowing through the VAV box.
If more than one sideloop is required, HVAC PRO Release 5.10 or
later allows downloading of a VAV terminal control configuration to a
UNT11n-1.
The VAV controller cannot be downloaded as a point multiplexer. The
unused points, however, can be user defined and used with a single
sideloop.
For more detailed information on the operation of sideloops, see
Appendix A: Sideloop Applications (LIT-6375160).