AAON Orion VCCX2 User Manual

81
VCCX2 Controller Technical Guide
Airow Monitoring
Outdoor, Supply, Return and Exhaust Airow can be monitored
using the EBTRON
®
GTC116 or HTN104 series, Paragon
MicroTrans
EQ
series, or GreenTrol GA-200-N Module in
conjunction with a GreenTrol GF series of airow station.
Contact AAON Controls for information on other airow station
options. The VCCX2 will control the Outdoor Air Damper to
maintain an Outdoor Air CFM Setpoint. This operation can be
overridden higher by normal Economizer control.
On an MUA unit or a unit congured for Space Control of High
Percentage Outdoor Air, since the damper is typically at 100%,
the VCCX2 can be congured to modulate the Supply Fan VFD
to maintain an Outdoor CFM Setpoint.
Pre-Heater Operation
A Pre-Heat relay can be congured to energize anytime the
Supply Fan is operating and the Outdoor Air Temperature is
below the Pre-Heat Setpoint. This option allows pre-heating of
cold outside air before it reaches the evaporator coils and is useful
in Hot Water/Chilled Water applications or during CO
2
control
of the economizer in low temperature conditions. This operation
only occurs in the Occupied Mode of Operation.
If using the Preheat-X Controller, an SCR preheater and/or stages
of preheat can be controlled. If the Entering Air Temperature
(sensor connected to the Preheat-X) falls below the Pre-Heat
Setpoint, then preheat will be controlled to either a Cooling,
Heating or Vent Mode Preheater Leaving Air Setpoint - depending
on if the VCCX2 is currently in the Cooling, Heating, or Vent
mode of operation. These setpoints are all set in the VCCX2
Controller. If using the Preheat-X Controller in conjunction
with the VCCX2 controller, the entering air temperature on
the Preheat-X (instead of the outdoor air temperature sensor
connected directly to the VCCX2 Controller) will be used as the
temperature that locks out compressors. See the PREHEAT-X
Controller Technical Guide for more details.
Low Ambient Operation
A Low Ambient Relay can be congured. Whenever the Outdoor
Air Temperature falls below the Low Ambient Setpoint, this Low
Ambient Relay will energize. This operation occurs in both the
Occupied and Unoccupied Modes of Operation.
Heat Wheel
One of the relay outputs can be congured as a Heat Wheel Relay.
This relay will enable the Heat Wheel when the unit goes into
the Occupied Mode. If the unit is a recirculating unit congured
to use Economizer free cooling, the relay will disable during
Economizer operation.
If the unit is a 100% Outdoor Air MUA unit congured to use
the Outdoor Air Sensor as the controlling sensor, then the Heat
Wheel Relay will disable in between the Outdoor Air Cooling
and Heating Mode Enable Setpoints (Outdoor Air Vent Mode).
Similarly, on a unit configured for Space Control of High
Percentage Outdoor Air, and the unit is in Outdoor Air Vent Mode,
the wheel is disabled. The controller can also be congured to
disable the Heat Wheel Relay between High and Low Outdoor
Air Enthalpy Setpoints.
Heat Wheel Defrost
A Defrost Mode will occur if the Heat Wheel relay is active, the
Outdoor Temperature is below the Heat Wheel Defrost Setpoint,
and 30 minutes have elapsed since the last Defrost Mode. The
Defrost Mode will disable the Heat Wheel Relay for 2 minutes.
Before the Heat Wheel Relay disables, a 2-minute delay will
occur while the Economizer closes to a 10% position to allow
the return air to have maximum defrost eect on the wheel. At
the end of the Defrost Mode, the Heat Wheel Relay will enable,
and the economizer will return to its normal position. This 10%
re-positioning will not occur on units congured for MUA control
(OA is the controlling sensor), or for units in Hood-On operation,
or for units that are congured for Space Temperature Control
of a High Percentage Outdoor Air.
Duct Static Pressure Control
If the VCCX2 Controller has been congured for Duct Static
Pressure Control, then anytime the Supply Fan is operating, the
unit will be controlling to a Duct Static Pressure Setpoint. The
Static Pressure Control Output Signal can be used to control a
Supply Fan VFD (Direct Acting Operation) or a Zoning Bypass
Damper Actuator (Reverse Acting Operation).
The Duct Static Pressure Setpoint, the Setpoint Deadband, the
Static Pressure Control Signal, and the Static Control Rate are
all user-adjustable. The Static Control Rate is the amount of time
that elapses between each adjustment to the Duct Static Pressure
Control Output Signal. The default period is 10 seconds and
should not be changed unless close observation reveals that the
Supply Fan or Bypass Damper is hunting and not maintaining a
stable pressure reading.
For Supply Fan VFD operation, the Output Signal increases
(increases the VFD speed) if the Duct Static Pressure is below
the Duct Static Pressure Setpoint by the Deadband amount, and
the Output Signal decreases (decreases VFD Speed) if the Static
Pressure is above the Setpoint by the Deadband amount.
SEQUENCE OF OPERATIONS
Airow Monitoring, Pre-Heater, Low Ambient and Duct Static Press

AAON Orion VCCX2 Specifications

General

Brand	AAON
Model	Orion VCCX2
Category	Controller
Language	English