Model OAC-4000


OAC Series


Outdoor Airflow Controller Module with Analog Control Output Signal for Proportional Actuators and Analog Input Fan Speed Controllers

Outdoor Airflow Controller Modules for Systems without an Airside Economizer

The OAC-4000 modulates a proportional analog actuator or fan speed controller to maintain the outdoor airflow rate. The analog actuator solution allows for larger damper sizes and is ideal for ducted systems to fan coils, makeup air to air handlers, makeup air fans or zone level DOAS applications. DCV requires approved BACnet MS/TP CO2 sensors or occupancy counters.

  • Occupied mode is typically enabled by a 24 VAC output from a thermostat on fan coil systems or via BACnet MS/TP on makeup air to air handlers or zone level DOAS systems.
  • Compensate for damper hysteresis, filter loading, wind, stack and fan speed variations √ Provide continuous verification of intake flow rates
  • Demonstrate compliance with ASHRAE Standards 62.1, 90.1 and 189.1
  • Satisfy LEED prerequisites and document code compliance
  • Improve indoor air quality and thermal comfort
  • Save energy
Overview PDF



  • Compatible with GreenTrol IAT integrated thermal dispersion airflow/temperature sensors or approved BACnet MS/TP airflow measuring devices
  • 24 VAC/DC or MS/TP BACnet binary input activates occupied mode operation
  • Provide airflow setpoint control, CO2-DCV or population based-DCV during occupied mode
  • Accepts approved BACnet MS/TP CO2 sensors or occupancy counters when DCV is required
  • Clamp DCV airflow rates between minimum and maximum airflow limits
  • Supports unoccupied airflow setpoint control
  • Built-in notification alarms
  • Contact closure relay can be assigned to notification alarms or active control mode
  • MS/TP BACnet connection


The OAC-4000 can be provided with a single integrated IAT-DI duct probe, one or two integrated IAT-UI or IAT-US universal mount probes or an approved external BACnet MS/TP airflow measurement device.

The OAC-4000 interfaces with approved MS/TP BACnet CO2 sensors and occupancy counters when DCV is required.

The OAC-4000 modulates a proportional damper actuator or variable speed fan (VFD or ECM with analog speed control input) to maintain the outdoor airflow rate when an external binary trigger is active (i.e. occupied mode). The binary trigger is typically is provided by a thermostat or other analog or MS/TP BACnet binary output. The trigger can also be provided by the 24 VAC control signal used when a two-position actuator is provided for outdoor air control (replace the two-position actuator with a proportional actuator).

Advanced logic and airflow measurement improves traditional CO2-DCV when demand control ventilation is required. The OAC-4000 controller resets the outdoor airflow setpoint between user defined minimum and maximum airflow limits to maintain either a user defined fixed CO2 level or variable airflow setpoint based on the population using a built-in CO2/airflow counting algorithm or external occupancy counter.

The OAC-4000 interfaces with most MS/TP BACnet building automation systems and supports full read/write privileges as a BACnet 1/8 load master. An RS-485 signal isolator is available when an isolated MS/TP network is required.


Minimum Outdoor Air Control (MOAC) Modes Supported

FLOW: Maintains a user defined airflow setpoint

CO2: Maintains a user defined CO2 level by resetting the outdoor airflow setpoint (requires a CO2 sensor)

CO2/OAF: Maintains a calculated outdoor airflow setpoint based on the estimated ventilation zone population (requires a CO2 sensor)

COUNT: Maintains a calculated outdoor airflow setpoint based on the occupancy counter population (requires an occupancy counter)

FIXED: Maintains a fixed damper position (no control)

PASS: Passes the economizer controller output signal (no control)

Unoccupied Air Control (UAC) Mode Option: Yes, maintains a user defined airflow setpoint

Economizer Controller Fault Signal Output: Not supported

Notification Alarms

“Unoccupied Mode” High/Low Airflow Alarm

“Minimum Outdoor Airflow Mode” High/Low Airflow Alarm

“All Modes” CO2 Alarm (requires a CO2 sensor)

“All Modes” System Trouble Alarm

Note: Alarms can be assigned to the contact closure relay


Display: 16-character alpha-numeric LCD

Navigation: 4-button interface


Type: Accepts GreenTrol IAT-DI, IAT-UI and IAT-US Thermal Dispersion Airflow and Temperature Measurement Probe (required unless an external MS/TP airflow measurement device is provided). See appropriate IFT product data sheet for probe information.

Available Configurations: IAT-DI Probes

Single Probe: 1 probe x 1 or 2 sensor nodes/probe

Available Configurations: IAT-UI and IAT-US Probes

Single Probe:Dual Probe: 2 probes x 1 sensor node/probe

Dual Probe: 2 probes x 1 sensor node/probe



Type: Binary Input (BI1)

Assignment: Mode activation trigger signal

Configurable Ranges: 0-24VAC or 0-24VDC

Trigger Threshold:

VAC Configuration: 7 VAC

VAC Configuration: 3 VAC



Assignment: Airflow control signal

Configurable Ranges: 0-5V, 0-10V, 2-10V, or 4-20mA

Maximum Number of Actuators Supported:

0-5V, 0-10V or 2-10 V: Unlimited

4-20mA: 2



Type: Dry contact w/ onboard jumper to drive a remote LED

Assignment: OAC alarms or Control Mode

Status: Normally Open (N.O.)

Rating: 30 VDC or 24 VAC @ 3 amp. max.



Type: Non-isolated MS/TP BACnet master connection (provide an RS-485 network isolator if isolation is required)

B.A.S. Object Read/Write Access: Yes

Device Load: 1/8 load

Supported Baud Rates: 9.6, 19.2, 38.4 and 76.8 kbaud

MS/TP BACnet Airflow Sensor Capability: One GreenTrol Automation or approved third-party airflow measurement device (cannot be used if an integrated airflow measurement device is connected).

MS/TP BACnet CO2 Sensor Capability: One GreenTrol Automation or approved third-party space mounted or return air CO2 sensor

MS/TP BACnet Occupancy Counter Capability: One to four GreenTrol Automation or approved third-party occupancy counterssensor


Environmental Limits

Temperature: -20 to 120 ⁰F [-28.9 to 48.9 ⁰C]

Humidity: 5 to 95%

Important: Provide a weather-proof enclosure if the controller module is mounted outdoors

Power Requirement: 24 VAC (22.8 to 26.4 under load) @8.5V-A

Dimensions: 4.34H x 6.59W x 1.83D in. [110.2 x 167.3 x 46.6 mm]

Related Documents

Data Sheets
Users Manual
Product Catalog