This module controls a proportional heating source within a zone control application. Besides controlling the primary source temperature (typically the zone), this module specifies functionality for controlling a discharge air low limit temperature. The module accepts as inputs a mode, process variable, setpoint, limit variable, limit setpoint, limited max value, flush position, and inputs to the PID blocks within the module. Based upon the input command and parameter settings, the module outputs a percent command and control status. This module also incorporates tracking the overridden value of the actual output object (AO, PAO). The module resets the PIDs to default tuning parameters if the Reset PID Tuning input is not Normal.
This module provides a second output that incorporates lead compensation to control devices. This function attempts to remove some of the dynamics of the control loop. This process results in forward-looking predictions and speeds up controller responses. The effect is similar to adding derivative action to the controller. Lead compensation is incorporated into most zone temperature control processes where oversized or nonlinear valves might be applied. For more information on the Lead Compensator block, see Lead Compensator in the Control category of the Logic section.
This module provides Exponentially Weighted Moving Average (EWMA) diagnostic values calculated by the PID. Controllers have the ability to collect data about their inputs, outputs, and internally calculated variables. Inside the controller, the EWMA minimizes memory requirements, reduces communication traffic, and provides an easy way to analyze collected data. See EWMA Diagnostics in the Commissioning a System section for more information.