Valent VX Series Controller 7
supplied 0-10 VDC signal to the fan’s VFD is
responsible for modulating the supply fan’s speed.
The signal is linear and the speed is at min when 0V
is present and at max when 10V is present.
• Space Static Pressure: The exhaust fan modulates
to maintain a space static pressure set point based
on a sensor located in the space. A space static
pressure sensor or BMS communicated value in
required for this sequence.
• Supply Fan Tracking: The exhaust fan proportionally
modulates based on the supply fan speed plus an
adjustable offset.
• Outside Air Damper Tracking: The exhaust fan
proportionally modulates based on the outdoor
air damper modulation. (This sequence requires a
modulating outdoor air damper.)
Outside Air and Recirculated (Recirc) Air
Damper Control
If equipped with a modulating OA and recirculated air
damper, the recirculated air damper will operate inverse
of the OA damper. The OA damper opens to its min
position. If the controller is configured to modulate the
supply fan speed, the min and max OA positions can
be reset based on supply fan speed. If equipped with
BMS communications, the BMS can directly control
the outside damper position. The damper position is
constrained by its min and max set point positions.
• CO2Control: The controller will proportionally
modulate the OA/RA dampers based upon a
comparison of the CO2set point to the actual CO2
level reported from the sensor. As the CO2level rises,
the controller will proportionally modulate the OA
damper open, between the min OA damper position
and max CO2position.
• Space Static Pressure: The OA/RA dampers will
modulate based upon the signal from a building static
pressure sensor. The controller will modulate the
dampers, between the min and max OA positions,
based upon a comparison of the building static
pressure set point to the actual building static
pressure level reported from the sensor.
Energy Recovery Wheel Sequences
Economizer: If the unit is equipped with an energy
recovery wheel, the economizer will modulate/stop the
energy wheel to achieve free cooling.
• Stop Wheel: When economizer mode is enabled and
there is a call for cooling, the wheel will stop rotating
to allow free cooling. Jog wheel control is available
during stop wheel economizer operation. This
sequence allows the wheel to rotate for a short period
of time exposing a new section to the air stream.
• Modulate Wheel: When economizer mode is
enabled and there is a call for cooling, the controller
Sequence of Operation
modulates wheel speed to maintain the supply
temperature set point.
• Energy Wheel Bypass Dampers, if equipped:
During normal operation, the dampers shall remain
closed to allow full operation of the energy wheel.
During economizer sequences, the dampers will be
open to bypass the energy wheel.
Frost Control: The microprocessor controller will
activate the frost control method when the OA
temperature is less than the defrost set point (5°F) and
the wheel pressure switch is closed due to a high wheel
pressure drop. Once the pressure drop decreases
below the pressure switch point or the OA temperature
increases, the unit will resume normal operation.
• Electric Preheater: When frosting is occurring, the
preheater is energized to defrost the wheel.
• Modulate Wheel: When frosting is occurring, the
wheel slows to allow defrosting to occur.
• Cycle Wheel: When frosting is occurring, the
energy wheel is cycled off for a defrost cycle time
(5 minutes). After the defrost cycle time, the wheel
is re-energized to continue normal operation. The
controller will not allow another defrost cycle for a
min normal operating cycle time (30 minutes).
• Timed Exhaust: When frosting is occurring, the
supply fan is cycled off along with the tempering
for a defrost cycle time (5 minutes). The exhaust
fan will continue to run allowing the warm exhaust
air to defrost the wheel. After the defrost cycle
time, the supply fan and tempering are re-energized
to continue normal operation. The controller will
not allow another defrost cycle for a min normal
operating cycle time (30 minutes).
Alarms
The microprocessor controller includes a digital output
for remote indication of an alarm condition, which
connects via the J15 port. Alarms include:
• Dirty Filter Alarm: If the outside air or return air
filter differential pressure rises above the differential
pressure switch set point, the microprocessor
controller will activate an alarm.
• Supply and Exhaust Air Proving Alarm:
Microprocessor controller monitors proving switch on
each blower and displays an alarm in case of blower
failure.
• Sensor Alarm: Microprocessor controller will send
an alarm if a failed sensor is detected (temperature,
pressure, relative humidity).
• Supply Air Low Limit: If the supply air temperature
drops below the supply air low limit (35°F), the
controller disables the unit and activate the alarm
output after a preset time delay (300 sec.).
• Other Alarms: Wheel Rotation, High Wheel Pressure,
High/Low Refrigerant Pressure.
