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Power pack types – compressor combinations
The controller is able to control power packs with up to 8
compressors of various types:
- One or two speed controlled compressor
- Capacity controlled piston compressors with up to 3 unloader
valves
- Single step compressors – piston or scroll
The chart below shows the compressor combination which the
controller is capable of controlling. The chart also shows which
coupling pattern can be set for the individual compressor combi-
nations.
Combination
Description
One-step compressors. *1
A compressor with an unload
valve, combined with one-step
compressors. *2
Two compressors with unload
valves, combined with one-step
compressors. *2
All compressors with unload
valves. *2
A speed-regulated compres-
sor combined with one-step
compressors. *1 and *3
A speed-regulated compressor
combined with several com-
pressors with unload valves. *2
and *3
Two speed-regulated compres-
sors combined with one-step
compressors *4
*1) For a cyclical coupling pattern, the one-step compressors must be the same size.
*2) For compressors with unload valves, it is generally true that they must have the
same size, the same number of unload valves (max 3) and the same sized main
steps. If compressors with unload valves are combined with one-step compres-
sors, all compressors should be the same size.
*3) Speed-regulated compressors can have different sizes in relation to subsequent
compressors.
*4) When two speed-regulated compressors are used, they must have the same
frequency range.
For cyclical coupling patterns, the two speed-regulated compressors should be
the same size and the subsequent one-step compressors should also be the same
size.
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.
AK-HP 780
Coupling
pattern
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Heat pump controller
RS8GF202 © Danfoss 2015-08
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 efficient.
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
x
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.
x
For example:
Two capacity-regulated compressors of 20 kW, each with 2 unload
valves, cyclical coupling pattern.
x
• 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.
83
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