Sequence of operation
The VAV Zone Controller supports 3 types of pressure-independent terminal configurations:
•
Single duct
•
Series fan-powered
•
Parallel fan-powered
The controller can operate as part of a linked system (VAV or VVT) or as a stand-alone controller.
Temperature sensors
The VAV Zone Controller supports the following temperature sensors:
Sensors
Notes
Space temperature sensors:
•
SPT Standard, Plus, or Pro
You can average up to 5 SPT communicating sensors.
•
T55
Push the sensor's override button from 2 to 10 seconds to initiate a
timed override.
If a network space temperature value is used, that value must be
written to the BACnet space temperature point (system_spt) at 1 to 5
minute intervals or on a COV of 0.1∆°F (.06∆°C).
Supply Air Temperature (SAT)
sensor
If the zone has ducted reheat, install an SAT sensor downstream of
the reheat source. The SAT is used in controlling the reheat.
If heat is not supplied, install the SAT sensor in the duct on the
terminal's leaving air side.
The SAT determines the air source mode should Linkage
communication fail or if the controller is stand-alone. See
Air Source
Mode Determination
(page 46) for details.
See the
Carrier Sensors Installation Guide
for details on these sensors.
Zone airflow control
The VAV Zone Controller provides pressure-independent zone temperature control by modulating its built-in
damper actuator to control the flow of primary air into the zone. The controller uses PID control to calculate the
airflow setpoint based on the air source mode and the difference between the zone’s temperature and setpoints.
The air source mode determines if the primary air can meet the zone’s need. If the zone controller is in a linked
system, the air source mode is determined by the air source. If the zone controller is stand-alone or if linkage
communication fails, the mode is determined by the controller's SAT sensor. See
Air source mode determination
(page 46). If the air source mode is the same as the zone’s required mode, the damper is positioned so as to
modulate the airflow setpoint between the mode’s configurable minimum and maximum airflow based on the
occupancy status of the zone. This minimum insures sufficient minimum airflow at the air source and sufficient
ventilation to the zone during occupied periods.
Sequence of operation
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VAV Zone Controllers