This module controls the Exhaust Air Damper (EAD), Outdoor Air Damper (OAD), and the Return Air Damper (RAD). The module controls airflow by modulating the EAD instead of the OAD; therefore, the EAD is modulated, the OAD is controlled like a 2-position damper, and the RAD position becomes the complement of the EAD position. Controlling the dampers in this fashion (with Return Fan Volume Matching Control) helps make sure that all outdoor air drawn into the unit comes through the outdoor air damper (and is not drawn in through the exhaust damper).
The module has functions for economizer and low limit control. It also has functions to ramp the damper 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.