Auto-Zone Control Systems Auto-Zone CV-C Controller Installation Guide (Version 01A) - Manual (Page 24)

Section 2 Auto-Zone CV-C
2-14 Sequence of Operation
below the cooling setpoint by the same amount it rose above it to start the
demand.
c. Once the cooling demand has been satisfied, the valve will go fully closed
until the next cooling demand or until the Humidity requires the valve to
open.
Once the Chilled Water Valve is enabled for operation, the actual valve position is
calculated using a Proportional, Integral and Derivative (PID) formula. All three formula
constants are user adjustable along with a fourth setpoint for the Integrating Interval.
There are defaults programmed in the code that should not be changed unless the user,
through actual observation, has determined that the valve is hunting or is not operating
quickly enough to maintain a constant Supply Air Temperature.
A later section entitled PID Operation can be refereed to for an actual example of code
that does the valve positioning. This formula applies to both Chilled Water and Hot
Water Valve operations.