Daikin DPS - Fan Control

Fan Control
(See page 36 for more information)
Indoor Air Fan - On/Off Control
A supply fan is provided on every unit. This may be the only
fan, but an exhaust fan can be provided also. The start/
stop signal and the speed signal for fans are provided via an
internal ModBus network.
Supply Fan
The supply fan is turned on when the unit enters the
Recirculation state. The supply fan is turned off when
the unit transitions to the Off state, but it stays on for a
OffHtClDelayTime (Default- 120 seconds) if the unit is turned
off while cooling or heating is active. The OffHtClDelayTime
function is overridden when and Emergency Off or Duct High
Limit fault is active.
Exhaust Fan On/Off Control
A DPS unit can be equipped with either a CAV or VAV 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%).
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%).
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).
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 congured for CAV exhaust fan operation
via the Unit Conguration menu. When congure 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.
Supply Fan Capacity Control (VAV)
The speed of a modulating supply fan is controlled by a
0-100% signal provided to the fan motor via an internal
Modbus network. Supply Fan Capacity Control for a
modulating fan is controlled to maintain the duct static pressure
at a desired value, maintain a xed speed based on a signal
provided via a network, or maintain space temperature
conditions (1ZnVAV).
The choice of control method, SF Cap Ctrl, may be set to Duct
Pressure, Speed or Single Zone VAVvia the keypad. After the
supply fan is started, a speed signal of 33% is sent to the fan
motor for the DSPCtrlDelay (Default=30 seconds). Control
reverts to either duct pressure, speed or single zone VAV after
the fan has been on for the duration of the DSPCtrlDelay time.
The motor speed is not controlled below the minimum SAF
speed setting (default 33%) while the fan is operating.
operator’s guIde
www.DaikinApplied.com 111 OM 1141-3 • MICROTECH UNIT CONTROLLER