LG AR-DR12-05A Installation And Operation Manual page 118

CONTROLLER
Sequences of Operation
Off / Standby
Standby occurs when there is not an occupied or unoccupied start command.
Hard Shutdown: A hard shutdown occurs under the following conditions:
• A user or the BMS disables the system, and the supply temperature is less than the soft shutdown enable set-point.
• The service switch is in the off (disabled) position.
• Occupancy is commanded to unoccupied while there is no unoccupied start command, and the supply temperature is less than the soft
shutdown enable set-point.
When a hard shutdown occurs:
• The unit shuts down immediately; and
• Dampers spring-return to their off position.
Soft Shutdown: A soft shutdown occurs under the following conditions:
• A user or the BMS disables the system, and the supply temperature is greater than or equal to the soft shutdown enable setpoint.
• There is no unoccupied or occupied start command and the supply temperature is greater than or equal to the soft shutdown enable set-
point.
The following occur during a soft shutdown:
• Thermodynamic outputs immediately revert back to their off value; while
• Dampers remain open and fans continue to run; until
• The supply air temperature falls below the soft shutdown enable set-point minus 5.0°F; or
• The soft shutdown delay timer has expired.
System Disabled
The unit becomes disabled due to the following:
• The unit was disabled from the Unison controller's Main Menu >
Unit Enable screen.
• The unit was disabled from the BMS.
When disabled, the following actions occur:
• The unit shuts down immediately; and
Damper Sequences
Outside Air Damper: The outside air damper modulates based on the maximum value of the following control options:
• CO control
2
• Economizer
The final outside air damper position command is constrained by the outside air damper minimum and maximum set-points. The maximum
outside air damper position may be limited by one of the following:
• Heat pump defrost
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• The service switch is in the off position.
• The shutdown input is in the shutdown position.
• A shutdown alarm was activated.
• Dampers spring-return to their off position.
• Outside air damper CFM
• Space static pressure
• Winter ramp