Carrier RTU Open v3 Integration Manual

Contents

Sequence of OperationRTU Open v3 Carrier Proprietary and Confidential CARRIER CORPORATION ©2016Integration Guide All rights reserved21Power ExhaustThe RTU Open may enable and disable an exhaust fan, based on either the controller’s occupancy or itseconomizer damper position. If the Fan Control is set to Two Speed or Variable Speed, the Power ExhaustSetpoint is automatically adjusted based on the fan’s air delivery. The Calculated PE Setpoint used for control isdisplayed in the Maintenance section.If Continuous Occupied Exhaust is Yes, the Power Exhaust binary output (BO-8) is energized while the RTU Openis occupied and de-energized when unoccupied.If Continuous Occupied Exhaust is No, the Power Exhaust binary output (BO-8) is energized when the economizerdamper output exceeds the Calculated Power Exhaust (PE) Setpoint value. The output remains energized until theeconomizer output falls below the Power Exhaust Setpoint value by a fixed hysteresis of 10%.Pre-Occupancy PurgePre Occupancy Purge allows the rooftop equipment with an economizer damper to use outdoor air to purge thespace of contaminants just prior to the beginning of the occupied period.The following conditions must be true for pre-occupancy purge to operate:• Pre-Occupancy Purge set to Enable• Economizer Exists set to Yes• A local time schedule is configured• The local time schedule is currently unoccupied and the remaining time is less than the configured PurgeTimeWhen the RTU Open schedule is unoccupied and the remaining unoccupied time is less than the purge time, thesupply fan starts. The economizer damper opens to the configured Economizer Purge Min Pos. The RTU Opencontinues to operate in this mode until the occupied start time is reached. The Pre-Occ Purge state is displayed inthe Maintenance section.Unoccupied Free CoolingUnocc Free Cool Enable allows rooftop equipment with an economizer damper to use outdoor air for free coolingduring unoccupied periods.The following conditions must be true for unoccupied free cooling to operate:• Unocc Free Cool Enable set to Enable• The system is unoccupied• The outside air temperature is below the Economizer High OAT Lockout Temp setpoint• The outside air temperature is less than the space temperature• Enthalpy (if enabled) is Low