Danfoss AK2-SC 255 Reference Manual page 38

RS.8D.M1.22
Control method
Target control type
Ramp stages if ambient
AK2-SC 255 Reference Manual
Yes answer here will create an analog input (sensor
input) for the drop leg temperature sensor. (Appears
only if control is not by dropleg temperature.)
(List box:)
Target: The condenser fans will be controlled to
maintain a target pressure, dropleg temperature, or
saturated condensing temperature, depending on which
strategy is selected by the answer to the Control
sensor question above.
Cutin Cutout: The condenser will be controlled by
cut-in and cut-out based on target pressure, dropleg
temperature, or saturated condensing temperature,
depending on which strategy is selected by the answer
to the Control sensor question above. If Cutin
Cutout is selected, the next page will provide for
selection of cut-in and cut-out setpoints. The page is
not shown here, but is straightforward.
[Please read about all of the possible answers:]
(List box:)
Ramp together: Where there is variable speed fan
motor control, fans will come on in stages at minimum
speed, then all will be ramped up together.
Ramp stages: Where there is variable speed fan
motor control, each stage will be brought on and
ramped up. When a stage is at maximum speed and
additional fan capacity is needed, the stage will be
dropped to minimum speed and the next stage brought
on at minimum speed, then ramped up as required.
Neutral Zone: Danfoss Neutral Zone control will be
used. This is a strategy that operates to move current
value closer to target more rapidly the farther away the
current value is from target. If you select Neutral
Zone here, you will cause the next page answer on
inverter control to change to None. That will in turn
lock this selection to one between Rate of change and
Neutral Zone, since those strategies apply to installa-
tions without variable speed fans. If you change
equipment strategies, or select Neutral Zone in error,
first change the Target control type here to Rate of
Change, then go to the next page and change Fan
inverter control to the appropriate variable speed
control, either VO or VLT, to restore the variable
speed choices here.
Rate of change: An algorithm of an earlier generation
that approximates PID control by causing slower
capacity change as the current pressure approaches
target, and larger changes when current pressure is
more distant from target pressure.
(-99.0 to 150.0, +/- 0.0 to 9.9) If Ramp together is
selected, the strategy will change to ramp stages if the
ambient temperature is less than this setpoint.
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