Problem:
Setting Outside Air Damper position on Voyager III units
Issue:
The Voyager III IOM, RT-SVX34M-EN has instructions (pgs. 50-55) on how to set the Outside Damper position or Outside Airflow setpoint for Constant Volume (CV), Multi-zone VAV (MZVAV) and/or SZVAV units with or without the Demand Control Ventilation option. The problem that most techs run into 99% of the time is that the Outside Damper position is being controlled by BAS or the unit has a TD5 display installed and the Display Read Only mode of operation is set to Write.
Resolution:
TD5
There are several advantages of a TD5 display especially when you are setting up a SZVAV unit with DCV. The main advantage is that the TD5 will allow you to visually see all 5 damper position setpoints in the Economizer / Ventilation Report screen. The setpoints displayed are a result of if the TD5 display is set for Read or Write mode. If you would prefer your setpoints to come from the TD5 display then the "Display Read Only Mode" in Settings must be set to Write and if you would like the setpoints to come from the onboard potentiometers then the mode must be set to Read. The Read or Write setpoints are all or nothing, you cannot go in and choose to have setpoints from both setpoint sources. One last important thing to remember is either of these setpoint sources, Read or Write modes are overridden by communicated BAS control setpoints.
BAS has control of Outside Air Minimum Position Setpoint or Outside Airflow Setpoint
If connected to a Building Automation System or has a communications module installed, you notice no matter how the setpoints are adjusted at the onboard potentiometers or TD5, it is only controlling to one setting. More than likely, your BAS system has control over the minimum position or outside airflow setpoint. You can test this out by temporarily bypassing the communications module or placing the unit in LOCAL control with TU or at the Front-End System. Now try to control the damper's setpoints using the specified potentiometers or TD5 setpoints.
Unit has Traq option but only controls to Economizer Minimum Position Setpoint
If the BAS is sending an Economizer Minimum Position Setpoint (AO-1) to the unit, this must be placed out of service. You should also make sure that the Economizer Minimum Position Enable Command (BO-7) is out of service and set to Disabled.
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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.