Auto-Zone Control Systems Auto-Zone CV-C Controller Installation Guide (Version 01A) - Manual (Page 31)

Auto-Zone CV-C Section 2
Sequence of Operation 2-21
Relief Pressure Control Relief Pressure Control Relief Pressure Control Relief Pressure Control
If you have assigned both a Relief Pressure Sensor on an Analog Input and Relief Fan
control on one of the Analog Outputs, then the following control occurs.
If the Fan is running then the relief fan voltage signal increases as the relief pressure rises
above the Relief Pressure Setpoint by 0.02” WG. The voltage decreases as the pressure
drops below the setpoint by 0.02” WG. this 0.04” WG deadband is not user adjustable.
If the pressure ever exceeds the setpoint by 0.10” WG, the voltage signal will be doubled
in an attempt to reduce building pressure before damage occurs.
The relief fan voltage signal remains at zero volts whenever the main fan is off.
Economizer Control Economizer Control Economizer Control Economizer Control
If you assigned an Analog Output to control an Outside Air Damper ( Economizer ) then
the following sequence occurs.
Assuming that the current HVAC mode is calling for Cooling, the economizer is enabled
for operation when the outside air temperature is below the Enable Setpoint or a Wetbulb
Temperature, received from another controller on the communications loop, is receiving
a value that is below the Enable Setpoint. Whichever value that is being used, the
economizer is enabled when the temperature is 1° below the enable setpoint and is
disabled when the temperature rises 1° above the setpoint.
The economizer is always considered to be the first stage of cooling. If it cannot satisfy
the space temperature with the supply air or mixed air temperature it is providing, then
mechanical cooling will be enabled to operate if the outside air is above the mechanical
cooling lockout setpoint.
The user can select either Supply Air Temperature control or Mixed Air Temperature
control. If the user selects Mixed Air Temperature but then neglects to configure an
Analog Input as a Mixed Air sensor, the controller will default to using the Supply Air
Temperature. If no supply air temperature sensor is provided, then incorrect control will
occur!
Once the economizer is enabled to begin controlling, it checks the outside air temperature
and calculates a starting position to immediately drive to instead of just creeping slowly
open from its programmed minimum position. Once this initial adjustment is made, the