AAON VCCX2 User Manual

39VCCX2 Controller Technical Guide
SEQUENCE OF OPERATIONS
Modes of Operation
Remote Contact Control
A remote contact control option can be congured on the VCCX2
Controller to initiate the HVAC Modes of operation. If this option
is congured, all Heating, Cooling, and Dehumidication modes
will only be initiated based on 24 VAC wet contact closures on the
forced heating, forced cooling, and forced dehumidication inputs
on the VCCX2 Controller. This is a single conguration option that
applies to all three modes.
If both the forced heating and forced cooling inputs are inactive
or if both are simultaneously active, then the unit is in Vent Mode
state. In this condition in the Occupied Mode, only the fan would
be on for ventilation. In this condition in the Unoccupied Mode,
the unit would be o.
If forced dehumidication is also being used, it will operate in
conjunction with the forced heating and forced cooling inputs
according to which dehumidication option that is congured.
Space Sensor Operation
Space sensors are available as a plain sensor, sensor with override,
sensor with slide adjust, and sensor with override and slide adjust
(this is the version that is factory supplied). An E-BUS Digital
Space Sensor is also available with override and setpoint adjustment
capability.
Sensors with slide adjust can be programmed to allow Space
Setpoint adjustment of up to ± 10° F.
If the space temperature is the supply air temperature/reset
source, then the slide adjust will adjust the HVAC Mode Enable
Setpoints and the Supply Air Temperature/Reset Source Setpoints
simultaneously.
During unoccupied hours, the override button can be used to force
the unit back into the Occupied Mode (by pressing the button for
less than three seconds) for a user-dened override duration of up
to eight hours. Pressing the button between three to 10 seconds
cancels the override.
Multiple Digital Space Sensors
Multiple (up to 10) Digital Space Sensors can be connected to
the VCCX2 Controller in applications where multiple spaces (not
utilizing VAV boxes) could be served by a single unit. These sensors
can be either the E-BUS Digital Space Temperature Sensor with
Display or the E-BUS Digital Space Temperature/Humidity Sensor
with Display.
The VCCX2 can be congured to use temperature (high and low)
to determine the Cooling or Heating Mode or average the space
temperature values and use that value to determine the mode of
operation – in both cases relative to the VCCX2 Space Temperature
Setpoints. It would use the highest humidity value relative to the
Space Humidity Setpoint to initiate Dehumidication Mode.
The digital sensors each need to be configured with unique
addresses (#1 -10) and have an LCD display for this operation. In
this arrangement, only the sensor at address #1 can utilize the slide
adjust. All push-button overrides on the sensors will function. Each
sensor can have its own calibration oset, if required.
Indoor Air Quality (CO
2
) Control Operation
If the VCCX2 Controller is congured to monitor and control CO
2
levels, the economizer operation will be modied as follows:
1. If the CO
2
levels remain below the Low CO
2
Level
Setpoint, the economizer minimum position (or airow
minimum) will remain at its congured value.
2. As the level of CO
2
increases above the Minimum CO
2
Level Setpoint, the economizer minimum position (or
airow minimum) will begin to be reset higher. The
economizer minimum position (or airow minimum)
will be proportionally reset higher as the CO
2
rises within
the range set by the Minimum CO
2
Level Setpoint and
the Maximum CO
2
Level Setpoint. If the CO
2
level
reaches the High CO
2
Level Setpoint, the economizer
minimum position (or airow minimum) will be reset
to the maximum reset position.
3. The Maximum Reset Position Setpoint is the highest the
economizer minimum position (or airow minimum) can
be reset to during CO
2
control operation. This setpoint is
user-adjustable and does not keep the economizer from
opening further during economizer operation.
Supply Air Temperature Setpoint Reset
Various sources can be configured to reset the Supply Air
Temperature Setpoint. The following reset source options are
available:
• Space temperature
• Outdoor air temperature
• Return air temperature
• Fan VFD signal
• Remote supply air temperature reset signal
For whatever option is selected, a High and a Low Reset Source
Setpoint must be congured that will correspond to congured Low
and High Supply Air Temperature Setpoints. This must be done
separately for the Cooling Mode Setpoints and for the Heating
Mode Setpoints.
When the reset source is at its highest congured setpoint, the Supply
Air Temperature Setpoint will be reset to its lowest congured
setpoint. When the reset source is at its lowest congured setpoint,
the Supply Air Temperature Setpoint will be reset to its highest
congured setpoint.

AAON VCCX2 Specifications

General

Brand	AAON
Model	VCCX2
Category	Controller
Language	English