Auto-Zone Control Systems Auto-Zone Plus Systems Installation & Operation (Version 03A) - Manual (Page 195)

Auto-Zone Plus Section 4
Start-Up and Troubleshooting 4-45
4.0 CV Controller
Overview
4.1 How It Works
4.1.1 Initialization
On system powerup the LED2 remains extinguished for five seconds. After this delay, the
LED2 will blink out the address of the controller (Address Switch Setting). The LED2
will then extinguish for another five seconds and then begin to blink for a twenty second
startup delay. At the conclusion of this twenty second period, the LED2 will begin
blinking a diagnostic code every ten seconds. This code is described later in this
document. The duration of a powerup initialization sequence is roughly one minute.
During this initialization period, the controller retrieves all operating setpoints from its
non-volatile EEPROM memory and initializes all outputs to an OFF condition.
Note: All future references to the Constant Volume Unit in this document use
CVAHU as the designation.
4.1.2 Operating Summary
At all times, after the conclusion of the initialization sequence, the CVAHU performs a
specific set of operating instructions in the following order: (a - g repeat continuously)
a. Read Analog Inputs for Temperatures and Overrides.
b. Check the RS-485 communications port for any new setpoints from the System
Manager and keeps the status updated for the System Manager.
c. If the push-button override is active, it checks the timer to see if the override is
finished.
d. Calculates the current occupied/unoccupied mode from its internal week
scheduling.
e. Calculates what state the output relay and analog output should be set to.
f. Updates the diagnostic LED2 blinking.
g. Stores data in the internal trend log if ready for another log.