Demand Controlled Ventilation (DCV)
Configuration
Verify that Demand Controlled Ventilation is configured and that Supply Fan Compensation is enabled.
Confirm that in Settings > View Configuration Demand Control Ventilation is enabled and the CO2 Sensor is installed.
Supply Fan Compensation is located under Settings > Fresh/Return Air section
How to Enter and Configure
Setpoints
Demand controlled ventilation setpoints used in all methods.
- Space CO2 High Limit
- Space CO2 Low Limit
Demand controlled ventilation reduces energy consumption by reducing the outdoor air damper below design minimum ventilation based on space CO2. When Demand Controlled Ventilation is configured and Supply Fan Compensation is enabled, DCV resets the outdoor air damper minimum position based on space CO2 and supply fan speed. Decreasing CO2 levels will decrease damper position below the Design Minimum toward the DCV minimum damper position setpoint. Increasing CO2 level will increase damper position toward design minimum setpoint. DCV requires a valid space CO2 value from a building management system or wired sensor. If Space CO2 value is invalid or Supply Fan Compensation is disabled, the Symbio™ 700 will revert to Outdoor Air Minimum Position Control
Occupied and Occupied-Bypass mode. If the supply fan is at 100 percent and CO2 is at the Space CO2 High Limit (1500 ppm default), the outdoor air damper will be positioned at Design Minimum OA Damper Position at Full Fan Capacity (10 percent default). As CO2 in the space reduces below the high limit, the outdoor air damper will close. If CO2 falls below the Space CO2 Low Limit, the damper position will be at DCV Minimum OA Damper Position at Full Fan Capacity (5 percent default).
Occupied-Standby mode. The damper will reset, based on CO2, between the Standby Minimum OA Damper Position at Full/ Mid/Min Fan Capacity and DCV Minimum OA Damper Position at Full/Mid/Min Fan Capacity.
- DCV Minimum OA Damper Position at Full Fan Capacity
- DCV Minimum OA Damper Position at Mid Fan Capacity
- DCV Minimum OA Damper Position at Min Fan Capacity
- Design Minimum OA Damper Position at Full Fan Capacity
- Design Minimum OA Damper Position at Mid Fan Capacity
- Design Minimum OA Damper Position at Min Fan Capacity
CO2 Sensor
Present Symbio Application Guide
Demand Controlled Ventilation (DCV) – Thermostat Control
When the Symbio™ 700 is configured for Conventional Thermostat Control, 0 to 100 percent Economizer Damper and Demand Controlled Ventilation (Installed), the controller provides an Occupancy binary input that can be used to control Occupied and Unoccupied modes of operation. In Unoccupied mode, DCV is disabled, and the outdoor air damper minimum position is effective 0 percent. In Occupied mode, DCV will control the outdoor air damper based on Space CO2 while the supply fan is ON, as described in the previous sections.
In Occupied mode, if the supply fan cycles OFF, the controller will continue to monitor Space CO2. If Space CO2 exceeds the Space CO2 High Limit setpoint for 15 minutes, the supply fan will turn ON and operate at minimum speed and outdoor air damper at the Design Minimum OA Damper Position. If Space CO2 falls below the Space CO2 High Limit – 200 ppm, the supply fan will cycle OFF. The supply fan will also cycle off if occupancy changes to Unoccupied.
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.