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Air source mode determination
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
EVACUATION
VENT
See the air source's installation manual for more specific operation.
VVT Bypass Controller
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.
Evacuation is usually the result of a fire-life safety input at the air source
being active. The terminal fully closes its primary air damper and disables
its terminal fan, if equipped.
All terminals treat VENT mode the same as the COOL mode. For VVT
terminals, VENT modes allows for an increase in airflow. VVT terminals use
the greater of the configured Vent Damper Position or the Minimum Cooling
Damper Position as the minimum during the VENT mode.
Carrier Proprietary and Confidential
23
Sequence of operation
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