Linkage Modes And Operation - Carrier TruVu VVTZC-E2 Installation And Startup Manual

The air source responds by sending the air source mode, supply air temperature, and outside air temperature. The
air source verifies the mode by comparing its supply air temperature to the space temperature received through
Linkage. See the air source documentation for operation and parameters used to verify its mode. This verification
allows the VVT system to determine if the desired air source mode is actually being provided. For example, if the
VVT Master sends a request for heating and the air source does not have heat or it's heat has failed, the air
source's actual mode indicates that and its current mode is sent to the zones so that they can control accordingly.
The system remains in that mode until all zones of that demand are satisfied or until the System Mode Reselect
Timer (factory default is 30 minutes) causes a forced re-evaluation of the system. If there is no demand for the
opposite mode, the reselect timer starts again and the current mode continues until all zones are satisfied or until
the reselect timer expires, repeating the process. If there is a demand for the opposite mode, the VVT Master
sends the reference zone's space temperature and setpoints to the air source and restarts the reselect timer. The
air source re-evaluates its demand based on the new information and goes to the Vent mode until the new mode
can be verified as described above. The amount of time this takes is determined by the air source's operating
parameters.
The VVT Master continuously evaluates the system and updates the air source with the most current system
demand. Based on the evaluation, the reference zone can change from one zone to another. The evaluation
process continues until there is no demand from any zone or the 30 minute timer causes a re-evaluation of the
system conditions.
If no heating or cooling is required or the current air source mode is satisfied, the VVT Master calculates the
weighted average of the occupied and unoccupied heating and cooling setpoints. It also calculates a zone
temperature that is midway between the setpoints (occupied or unoccupied based on the system's current
occupancy status). This information, plus the occupancy status, is sent to the air source so that its current mode is
disabled and the unit ceases heating or cooling operation. If the system is occupied, the air source fan and OA
damper, if applicable, operate to maintain proper ventilation.

Linkage modes and operation

Linked air source modes – In a linked system, the air source determines its operating mode and qualifies that
mode based on its own SAT. The following modes can be sent by the air source depending on its capability and
configuration:
OFF
WARMUP
HEAT
FREECOOL
COOL
PRESSURIZATION
TruVu™ VVTZC-E2
Installation and Start-up Guide
Air source fan is off. Terminal damper is positioned approximately 70%
open to allow for system restart.
Air source fan is on and providing first cycle of heat when changing from
unoccupied to occupied. It may also be used as an equipment safety to
increase system airflow. The terminal's heating setpoint temporarily
increases to the midpoint between the configured occupied heating and
occupied cooling setpoints.
Air source fan is on and providing heat. The terminal modulates its primary
air damper to maintain the current heating setpoint.
Air source fan is on and providing cooling using only the economizer and
usually during an unoccupied period. The terminal modulates its primary air
damper to maintain the midpoint between the configured occupied heating
and occupied cooling setpoints.
Air source fan is on and providing cooling. The terminal modulates its
primary air damper to maintain the current cooling setpoint.
Air source supply fan is on usually as a result of a fire-life safety input being
active. It may also be used as an equipment safety to increase system
airflow. The terminal modulates its primary air damper to provide the
configured maximum cooling airflow.
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Wiring inputs and outputs
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