Setting Up CO2 (DCV)
Overview:
The W7212 will default to the DCV MAX Setpoint (for damper position) in the event of a CO2 sensor failure, we will use this feature in this procedure.
You will need some alligator clip jumper wires, a DC Voltmeter, and a control screwdriver.
Terms used in this procedure:
CW - Clockwise
CCW - Counter Clockwise
Minimum Position - the damper position when the CO2 level is below the DCV setpoint
DCV Max - the maximum the damper will open to when the CO2 level is above the DCV setpoint
DCV Set - the required CO2 level for the damper to start to move to the DCV Max setting
Sequence of Operation
If a field-installed CO2 sensor is connected to the economizer control, a demand-controlled ventilation strategy will begin to operate in parallel with the free cooling strategy. As the CO2 level in the zone increases above the CO2 set point position (as controlled by the DCV set potentiometer), the position of the damper will be increased proportionally to the DCV Max position (as controlled by the DCV Max potentiometer). As the CO2 level decreases because of the increase in the fresh air, the outdoor-air damper will be proportionally closed back down to the Min Position (minimum open position). The damper position will follow the higher demand condition from the DCV mode or free cooling mode.
Demand Control Ventilation CO2 Sensor Wiring
The CO2 sensor should be wired to the AQ and AQ1 terminals of the controller.
(sensor output should be configured for 2 - 10VDC Output)
Setting the DCV Setpoint, DCV Max Position, and Minimum Position
Remove CO2 Sensor output wires from the AQ and AQ1 terminals
Set the DCV SET Pot to full CW
Set the Min POS and DCV MAX pots to full CCW
Install a jumper wire between 2-10 VDC Actuator Output + terminal and AQ
Start the Indoor Fan
Connect DC Voltmeter to 2-10 VDC Actuator Output terminals
Turn MIN POS Pot to the desired voltage output for the ppm needed (see 2-10 chart below)
Turn the DCV SET Pot CCW until the DCV LED illuminates (this has set the DCV setpoint)
Turn the Min POS Pot full CCW
Disconnect the jumper wire between 2-10 VDC Actuator Output + terminal and AQ
Still measuring 2-10 VDC Actuator Output terminals adjust DCV MAX Pot to the desired volt setting (using the damper position chart below)
Reconnect CO2 sensor
Now set the Minimum Position using MIN POS Pot (measuring volts at 2-10 VDC Actuator Output and using the damper position chart below)
Approximate Damper Positions vs DCV Output from the Economizer Module
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.