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Control Variables
Fan Control
Exhaust Fan Control
26
Microprocessor Controller for DOAS
Menu
The Exhaust Fan Control menu allows the user to adjust exhaust control
setpoints.
e
F
d
xhausT
an
elay and
This screen displays the exhaust fan delay and enable based on OA damper
position. The exhaust fan delay will begin once the damper sequence is complete.
This delay can be used to offset starting times between the supply fan and
exhaust fan. This screen also provides the ability to enable the exhaust fan on a
set OA damper position if the unit is equipped with a modulating OA damper.
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F
o
o
xhausT
an
nly
uTside
This screen will appear when the exhaust fan only mode is available at the
controller by a contact closure. When the contact is closed, the exhaust fan will
run at 100%. The outside air damper will go to this position (100%) when the
contact is closed.
e
F
s
xhausT
an
peed
This screen displays min and max exhaust fan speed percentages.
The speed setpoint is the proportional percentage of the analog output from the
controller to the VFD.
25% Speed = Min speed
100% Speed = Max speed
Setpoint Selections:
Constant Volume – The fan speed will be constant; set from screen (e.g. 100%).
BMS – The BMS can directly control the fan speed (requires BMS communication
option).
Space Pressure – Fan speed is determined by building pressure control loop.
Supply Fan Tracking with Offset – The exhaust fan will track the supply fan,
between a min and max position. An offset can be added to achieve the proper
balance.
Outside Air Damper Tracking – The exhaust fan will proportionally track the OA
damper, between a min and max position.
Return Duct Static Pressure – Fan speed is determined by duct pressure control
loop.
0-10V Hardwired - The 0-10V signal hardwired at the controller determines
the speed of the fan after the controller sends an enable command to the vfd.
When the signal is below the minimum fan speed setpoint, the fan will operate at
minimum. When the signal is above the maximum fan speed setpoint, the fan will
operate at maximum.
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amper
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