Daikin DPS Installation And Maintenance Manual page 103

Variable Speed Wheel
When capacity limiting is allowed the effective measured
variable (ERDAT or DAT depending on the unit state as outline
in the Constant Speed Wheel section above) is controlled to
the effective discharge temperature setpoint using a PI loop .
Exhaust Fan Control
A DPS unit equipped with an energy recovery wheel is always
equipped with an exhaust fan . This fan is shipped from the
factory set up for VAV operation controlled based on building
static pressure . Units equipped with the 0-100% modulating
economizer operation should always remain set up for VAV
control on building pressure . Unit's equipped with 0-30% OA or
100% OA hoods can be set up for either CAV or VAV operation .
VAV Exhaust Fan
A VAV exhaust fan can be set for one of three different
methods of control with the RF/EF Ctrl= parameter . These are
building static pressure, manual/network speed, or outdoor air
damper position based control .
Building Static Pressure Control
When the RF/EF Ctrl= parameter is set for building pressure
control (BldgP) and exhaust fan operation is enabled, the fan
is turned on whenever the building static pressure input is
above the building static pressure setpoint by more than ½ the
deadband . Exhaust fan operation is enabled when outdoor
air damper position is greater than the MinExhOAPos= setting
(Default=5%) and the supply fan capacity is greater that the
MinExhSAFCap= setting (Default=10%) .
Once the fan is running the capacity of the fan is controlled
with a PI Loop to maintain the building static pressure at the
building static pressure setpoint .
The exhaust fan is turned off when the building static pressure
input is below the building static pressure setpoint by more
than ½ the deadband and the fan capacity is at its minimum
value (Default=5%) for longer than the MinExStopTime= period
(Default=120 seconds) .
Speed/Network Control
When the RF/EF Ctrl= parameter is set for speed/network
control (Spd/Net) and exhaust fan operation is enabled, the
fan is turned on whenever the RemExhF Cap= parameter is
set above the minimum value (Default=5%) via the keypad
or a network signal for longer than the MinExStartTime=
period (Default=120 seconds) . Exhaust fan operation is
enabled when outdoor air damper position is greater than
the MinExhOAPos= setting Default=5%) and the supply
fan capacity is greater that the MinExhSAFCap= setting
(Default=10%) .
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Once the fan is running the capacity of the fan is controlled
to the RemExhFCap= setting which is changed via the unit
keypad or a network signal .
The exhaust fan is turned off when RemExhF Cap= parameter
is set equal to or lower than the minimum value (Default=5%)
via the keypad or a network signal for longer than the
MinExStopTime= period (Default=120 seconds) .
Outdoor Damper Position Control
When the RF/EF Ctrl= parameter is set for outdoor damper
position control (OAD) the fan is turned on whenever the
outdoor damper position t is above the ExhOnOAPos= setting
(Default=40%) for longer than the MinExStartTime= period
(Default=120 seconds) .
Once the fan is running the capacity of the fan is controlled
between the minimum value (Default=5%) and 100% as the
outdoor damper position varies between the ExhOnOAPos=
setting (Default=40%) and the ExhMxOAPos= setting
(Defaut=100%) .
The exhaust fan is turned off when the outdoor damper
position t is below the ExhOnOAPos= setting (Default=40%)
for longer than the MinExStopTime= period (Default=120
seconds) .
CAV Exhaust Fan
A DPS unit can be configured for CAV exhaust fan operation
via the Unit Configuration menu. When configure this way
the exhaust fan is turned on 4 seconds after the supply fan
is started and runs at full speed as long as the supply fan is
running . The exhaust fan is stopped whenever the supply fan
stops .
Bypass Dampers (Not Applicable for
0–30% or 100% OA Units)
The bypass dampers are driven closed (Bypass Damper
Closed output is energized) whenever the OA Damper position
is less than or equal to the Minimum OA Position
The Bypass dampers are driven open (Bypass Damper Open
output is energized) whenever the OA Damper Position
exceeds the Minimum OA Damper Position by more that 3%
103 OM 1141-3 • MICROTECH UNIT CONTROLLER
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