Table of Contents
Advertisement
• Space Static Pressure: The exhaust fan modulates
to maintain a space static pressure setpoint 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 (-10%).
• Outside Air Damper Tracking: The exhaust fan
proportionally modulates based on the outdoor
air damper modulation. (This sequence requires a
modulating outdoor air damper.
• Exhaust Fan Only Mode: This fan mode is an
optional fan mode available where the exhaust fan
and the modulating outside air damper, if equipped,
are the only devices enabled. A contact closure
enables the mode and forces the exhaust fan to
run at 100%. The OA damper is forced to the
OAD Exhaust Fan Only position (100%) during this
operation. All other fans and tempering devices are
disabled during this mode of operation.
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 setpoint positions.
• CO
Control: The controller will proportionally
2
modulate the OA/RA dampers based upon a
comparison of the CO
2
level reported from the sensor. As the CO
the controller will proportionally modulate the OA
damper open, between the min OA damper position
and max CO
position.
2
• 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 setpoint to the actual building static
pressure level reported from the sensor.
• 0-10 by Others: An external field supplied 0-10 VDC
signal is responsible for setting the damper position.
• Two Position: An external field supplied digital
contact is responsible for setting the damper to max
position. The OA Damper min (30%) and max (100%)
positions are used for the low and high position
settings.
8
Microprocessor Controller for DOAS
Sequence of Operation
setpoint to the actual CO
level rises,
2
Energy Wheel Control
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.
• Modulate Wheel: When economizer mode is
enabled and there is a call for cooling, the controller
modulates wheel speed to maintain the supply
temperature setpoint.
• 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.
• Jog Wheel Control: A jog wheel control sequence
allows the wheel to rotate for a short period of time
exposing a new section to the air stream. This
sequence occurs when the wheel has been off for
the Wheel Jog Delay (60 minutes) and rotates for the
Wheel Jog Duration (2 minutes).
Frost Control (Polymer): The microprocessor
controller will activate the frost control method when
the OA temperature is less than the defrost setpoint
(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.
2
• 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).
Advertisement
Table of Contents
