Daikin DPS - Airside Economizer

Minimum Position Control - Field
Supplied Outdoor Airow Station Input
When the OA Flow Station parameter in the Software
Conguration Code is set to Field Station or Flow Station with
reset and the Field Station parameter on the keypad is set to
VDC or mA, the Minimum OA Position value is adjusted based
on the measured amount of outdoor air being brought into
the unit from a eld supplied airow monitoring station. If the
airow is below the desired value, the Minimum OA Position
is increased and if the airow is above the desired value,
Minimum OA Position is decreased.
The eld airow signal will be in the form of a 0-10V or 0-20 mA
input. The minimum and maximum sensor input values (0-10V
or 0-20 mA) and the corresponding minimum and maximum
CFM values are user editable.
NOTE: The Minimum OA Position is reset up and down
between the Ventilation Limit and the Demand
Control Ventilation Limit by a PI_Loop function to
maintain the eld OA CFM value at an adjustable OA
CFM Setpoint.
NOTE: When the OA Flow Station parameter in the Software
Conguration Code is set to Field Station, the eld
air ow input is assigned to the MCB-X1 input and
External of CO2 reset of outdoor dampers is not
available. When the OA Flow Station parameter in the
Software Conguration Code is set to Field Station
w/Reset, the eld air ow input is assigned to the
EMB-X1 input and External of CO2 reset of outdoor
dampers is available using the MCB-X1 input.
0-30%OA Units
A two position 0-30% OA actuator is controlled by a modulating
analog output. This actuator is driven to its fully open position,
nominally 30%, when the OA damper analog output is at its
maximum value and it is driven closed when the OA damper
analog output is at its minimum value. The desired minimum
open position between 0% and 30% normally is set by an
editable keypad menu item (Vent Limit). If a valid value is
provided via the network, that position is used as the desired
minimum open position instead of the keypad value
The two position damper is driven to the closed position when
the supply fan is off (Off and Startup state), the unit is in the
Recirculation state, unoccupied operation is active, or the fan
has been on for less than the Zero OA Time. As a result the
OA dampers are driven closed in night setback, night setup,
morning warm-up, and morning cool down situations. The two
position damper is driven to the desired minimum open position
in all other conditions.
The Ventilation Limit equals the keypad editable Vent Limit
and the Demand Control Ventilation Limit equals the keypad
editable DCV Limit. The Vent Limit cannot be set higher than
the 0-30%OAMax value. The DCV Limit cannot be set higher
than the Vent Limit.
Building Static Pressure Override
The minimum position determined by the various available
reset methods may be overridden for a variable exhaust fan
controlled by building static pressure when the exhaust fan has
been stopped due to low building static pressure if the building
pressure remains negative. If the user elects to use this
function and the exhaust fan has been stopped for a minimum
exhaust fan off time (Default = 120 seconds) a PI_Loop will
begin modulating the Min OA Pos setpoint upward to maintain
the building static pressure at the building static pressure
setpoint.
100% Outside Air Damper Control, Two
Position
100% OA two position actuators are controlled by a modulating
analog output.
The OA damper is driven to its 100% open position when
the OA damper analog output is at its maximum value and it
is driven closed when the OA damper analog output is at its
minimum value
The OA damper is open during the Start Initial period, and
it remains open during all operating states. The OA damper
remains open after the fan is turned off until 30 seconds after
the Airow Switch digital input indicates loss of airow. This
keeps the outside air dampers open in case there is a failure
or external override that keeps the fan running after it is turned
off by controller logic. If the fan is turned on by bypassing the
controls that have it off, the Damper Output is NOT turned on.
Airside Economizer
(See page 45 for more information)
If a unit is equipped with a 0-100% modulating economizer,
and the outdoor air is suitable for free cooling, the unit attempts
to satisfy the cooling load by using outdoor air before using
mechanical cooling. When the control temperature is above the
Occupied Cooling Set Point by more than half the Occupied
Cooling Dead Band and the discharge air temperature is
above the Discharge Cooling Set Point by more than half
the Discharge Cooling Dead Band, the controller enters the
Econo state. When the unit is in the Econo operating state, the
outdoor air dampers are modulated as required to maintain the
Discharge Cooling Set Point.
Economizer to Cooling Operating State
The transition from the Econo to Cooling operating state
occurs when the economizer is unable to satisfy the cooling
load and mechanical cooling is available. This will occur when
the commanded economizer position indicates more than 95%
open and the discharge air temperature (DAT control units) or
control temperature (Zone control units) is above the applicable
Cooling Setpoint by more than half the applicable Cooling
Deadband for longer than the Cooling Interstage Timer.
OM 1141-3 • MICROTECH UNIT CONTROLLER 106 www.DaikinApplied.com
operator’s guIde