Danfoss AK2-SC 255, Reference Manual, Page: 25 / 206

24 AK2-SC 255 Reference Manual RS.8D.M1.22
Compressor capacity
staging patterns
Paging down from the neutral zone screen reveals the compressor staging pattern
screen:
In the default screen, the staging pattern is Auto, for automatic staging, and there is
no selection for Steps. The controller will stage rack capacity in the smallest steps
possible from lowest total capacity to highest, automatically selecting the compressors
combination to run for each stage (based on the the configured compressor capacities
available on the rack).
When there are a large number of steps, manual staging can be used to eliminate
needlessly small steps and compressor cycling.
To use manual staging, select Manual from the pattern list box, then specify the
number of steps you want. The display that results will show a row compressor icons
for each stage. A compressor’s unloaders are represented by the small rectangles to
the right of the compressor icon.
In the sample screen, compressors are all 20 HP and each has 2 unloaders. Each
unloader is 33% of compressor capacity. These settings were determined on the
configuration page for each compressor.
Stage #1 is fixed at zero capacity and cannot be changed.
To change stage #2 or any higher stage, move the cursor to a compressor icon and
press enter. You will notice that the “piston” in the icon moves. When it is up, the
compressor is on. If there are unloaders on a compressor, subsequent clicks on the
compressor icon will turn the unloader steps on, one at a time. The small rectangles
will change color to indicate that the step is on. When all steps are on for a compres-
sor, the next click on the icon will turn everything off.
As you change a stage’s capacity, the number in the right column of the screen will