AAON Orion VCCX2 User Manual

83
VCCX2 Controller Technical Guide
Building Pressure Control
The VCCX2 can maintain Building Static Pressure anytime the
Supply Fan is operating. A Building Pressure Transducer must
be connected to the VCCX2 Controller. The following are the
available control options.
Direct Acting Building Pressure Control
• On/O󰀨 Exhaust Fan: If an On/O Exhaust Fan is being
used, a relay output must be congured for “Exhaust
Fan”. This relay will energize whenever the Building
Pressure rises above the Building Pressure Setpoint by
the Deadband amount. The relay will de-energize when
the Building Pressure falls below the Building Pressure
Setpoint by the Deadband amount.
• Exhaust Fan VFD or Modulating Exhaust Damper: If
congured for Modulating Exhaust, a user-adjustable
voltage output (AOUT4 – Building Pressure Output
on the VCCX2 Controller) will be used to control this
fan or damper. An Exhaust Relay can be congured if
necessary to enable the fan or damper. Whenever the
Building Pressure rises above the Building Pressure
Setpoint by the Deadband amount, the Exhaust Fan
Relay will energize and the Modulating Signal will
activate to control to the Building Pressure Setpoint. If
the Building Pressure falls below the Building Pressure
Setpoint by the Deadband amount, the Modulating
Signal will modulate towards 0% as it attempts to
maintain the Building Pressure Setpoint. The Exhaust
Fan Relay is energized whenever the Modulating Signal
is above 0%.
Reverse Acting Building Pressure Control
• Outdoor Air Damper: If this option is congured,
the VCCX2 will use the user-adjustable Economizer/
Outdoor Air Damper output signal (AOUT2 – Economizer
Control Signal) to maintain the Building Pressure
Setpoint. Whenever the Building Pressure falls below
the Building Pressure Setpoint by the Deadband
amount, the modulating Economizer Output Signal will
modulate the damper open to control to the Building
Pressure Setpoint. If the Building Pressure rises above
the Building Pressure Setpoint by the Deadband amount,
the damper will modulate towards closed as it attempts
to maintain the Building Pressure Setpoint. When this
option is selected, no Economizer free cooling or CO2
IAQ operation will be available.
NOTE: If Reverse Acting Building Pressure Control using
the Outdoor Air Damper is congured, the Hood
On input is ignored and will not drive the Outdoor
Air Damper open.
• Supply Fan VFD: Careful consideration should be made
regarding the eects of potential reduced airow when
using this option. Contact AAON if you have questions.
If this option is selected, the Supply Fan VFD Output
(AOUT1 on the VCCX2) will be used to control the
Supply Fan VFD to maintain the Building Pressure
Setpoint in similar fashion to the Outdoor Air Damper
control described above.
Return Plenum Pressure Control
The VCCX2 Controller can control the Return Plenum Pressure
using a motorized exhaust damper. This is used on certain RZ
units that have a return fan that will be used to control Building
Static Pressure. This sequence will require the use of the VCC-X
EM1 Expansion Module which has an input for a Return Plenum
Pressure Transducer (the same transducer used for the Building
Pressure control) and an analog output that is wired to the actuator
used to control the motorized exhaust damper. When the return
fan is active (based on Building Pressure) the motorized exhaust
damper will modulate to control to the Return Plenum Pressure
setpoint. If the pressure is above the setpoint the modulating
signal will move towards 100%. If the pressure is below setpoint
the modulating signal will move towards 0%.
Exhaust Duct Static Pressure Control
of Exhaust Fan
The VCCX2 Controller can control an exhaust fan based o of
exhaust duct static pressure. This sequence will require the use
of the VCC-X EM1 Expansion Module which has a modular
jack that the Duct Static Pressure Sensor will plug into. The
building pressure output will be used to control the exhaust fan
for this operation.
A standard pull-through exhaust fan creates negative duct static
pressure. Since a duct static pressure sensor reads positive
pressure, this sequence requires the tubing for the sensor to be
reversed so that the low side is in the exhaust ductwork. So,
although the user is actually controlling to a negative pressure, the
VCCX2 will be congured to use (and will display) an equivalent
positive Exhaust Duct Static Pressure Value and Setpoint. So,
if the duct static pressure is below setpoint, the control signal
will ramp up.
See the VCCX2 Controller Operator Interfaces SD Technical
Guide for the Setpoint and Deadband ranges associated with
this control. The Control Rate is the same as the Control Rate
congured for the Supply Duct Static Pressure control.
SEQUENCE OF OPERATIONS
Building Pressure Control and Exhaust Duct Static Pressure Control

AAON Orion VCCX2 Specifications

General

Brand	AAON
Model	Orion VCCX2
Category	Controller
Language	English