Sequence of Operation
RTU Open v3
Carrier Proprietary and Confidential
CARRIER CORPORATION ©2016
Integration Guide
All rights reserved
21
Power Exhaust
The RTU Open may enable and disable an exhaust fan, based on either the controller’s occupancy or its
economizer damper position. If the
Fan Control
is set to
Two Speed
or
Variable Speed
, the
Power Exhaust
Setpoint
is automatically adjusted based on the fan’s air delivery. The
Calculated PE Setpoint
used for control is
displayed in the
Maintenance
section.
If
Continuous Occupied Exhaust
is
Yes
, the
Power Exhaust
binary output (BO-8) is energized while the RTU Open
is occupied and de-energized when unoccupied.
If
Continuous Occupied Exhaust
is
No
, the
Power Exhaust
binary output (BO-8) is energized when the economizer
damper output exceeds the
Calculated
Power Exhaust (PE) Setpoint
value. The output remains energized until the
economizer output falls below the
Power Exhaust Setpoint
value by a fixed hysteresis of 10%.
Pre-Occupancy Purge
Pre Occupancy Purge
allows the rooftop equipment with an economizer damper to use outdoor air to purge the
space 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
Purge
Time
When the RTU Open schedule is unoccupied and the remaining unoccupied time is less than the purge time, the
supply fan starts. The economizer damper opens to the configured
Economizer Purge Min Pos
. The RTU Open
continues to operate in this mode until the occupied start time is reached. The
Pre-Occ Purge
state is displayed in
the
Maintenance
section.
Unoccupied Free Cooling
Unocc Free Cool Enable
allows rooftop equipment with an economizer damper to use outdoor air for free cooling
during 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