ABSTRACT
Staged control breaks up the control of the “end device” into parts, from zero percent to one hundred percent. Two-position control of a device or component is that which the component can assume only one of two positions, or “states.” Staged control can be thought of as “incremental control” of a process. A proportional controller is required to operate the end device. A proportional control signal is generated at the controller, which can be sent out to the control valve. For stable control, the controller must register the change in the controlled variable very quickly. Proportional Plus Integral Plus Derivative (PID) is a precision control strategy with origins in the process control industry, and is not normally needed in typical HVAC applications.
