This module controls the Outdoor Air Damper (OAD) and Return Air Damper (RAD) in a system with a relief fan. The module is designed so that OAD and the RAD are staged as shown in the following figure and ASHRAE Guideline16-2003 - Selecting Outdoor, Return, and Relief Dampers for Air-Side Economizer Systems. The OA Percent Cmd output is double the value of the Minimum OA Position input as indicated in the figure.
For temperature control modes, the OAD modulates from minimum position to 100%, Once the OAD is 100% open, the RAD modulates from 100% to 0%. The module has functions for economizer control and low limit control of the dampers. It also has functions to ramp the dampers to minimum position and maximum position. The module also accepts commands for pressurize, depressurize, and purge. This module also incorporates tracking the overridden value of the actual output objects. The module resets the PIDs to default tuning parameters if the Reset PID Tuning input is not Normal.