Danfoss AK-CH 650 - Page 83

AK-CH 650 Capacity controller RS8ER302 © Danfoss 2016-02 83
In appendix A there is a more detailed description of the coupling
patterns for the individual compressor applications with associ-
ated examples.
The following is a description of some general rules for handling
capacity-regulated compressors, speed-regulated compressors
and also for two speed-regulated compressors.
Capacity-regulated compressors with unload valves
"Unloader control mode" determines how the capacity distributor
should handle these compressors.
Unloader control mode = 1
Here the capacity distributor allows only one of the compressors
to be unloaded at a time. The advantage of this setting is that it
avoids operating with several compressors unloaded , which is not
energy ecient.
For example:
Two capacity-regulated compressors of 20 kW, each with 2 unload
valves, cyclical coupling pattern.
• For decreasing capacity, the compressor with the most operating
hours is unloaded (C1).
• When C1 is completely unloaded, it is cut-out before compressor
C2 is unloaded.
Unloader control mode = 2
Here the capacity distributor allows two compressors to be un-
loaded while capacity is decreasing.
The advantage of this setting is it reduces the number of compres-
sor start/stops.
For example:
Two capacity-regulated compressors of 20 kW, each with 2 unload
valves, cyclical coupling pattern.
• For decreasing capacity, the compressor with the most operating
hours is unloaded (C1).
• When C1 is completely unloaded , compressor C2 with one-step
is unloaded before C1 is cut out.