Air Source Mode Determination - Carrier RTU Open v3 Integration Manual

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.

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 and the referenced zone's temperature. The following modes can be sent by the air
source depending on its configuration:
• OFF – Air source fan is off.
•
WARMUP – Air source fan is on and providing first cycle of heat when changing from unoccupied to occupied.
•
HEAT – Air source fan is on and providing heat.
• FREECOOL – Air source fan is on and providing cooling using economizer only.
•
COOL – Air source fan is on, and cooling is provided by economizer and mechanical cooling.
•
PRESSURIZATION – Fire-Life safety override input is active. Air source fan is on providing 100 percent
outside air. Mechanical heating and cooling may be disabled.
•
EVACUATION/SHUTDOWN – Fire-Life safety override input is active. Air source fan is off.
• VENT – Air source fan is on, economizer providing ventilation without heating or cooling, providing neutral
supply air temperature.
See the air source's Installation manual for specific operation.
RTU Open v3
Integration Guide
Carrier Proprietary and Confidential
31
Sequence of Operation
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