Danfoss ADAP-KOOL AK-PC 783, Руководство по конструкции, Страница: 120 / 128

120 Capacity controller RS8GN202 © Danfoss 11-2013 AK-PC 783
In this section, there is a more detailed description of the com-
pressor combinations and the associated coupling patterns.
Compressor application 1 – single step
The capacity distributor is capable of managing up to 4 one-step
compressors according to the following coupling patterns:
• Cyclical
• Best fit
Cyclical operation - example
Here, all compressors are of the same size and the compressors
are cut in and cut-out in accordance with the First-In-First-Out
(FIFO) principle, in order to equalise operating hours between the
compressors.
- There is operating time equalizing between all compressors
- The compressor with the fewest running hours starts first
- The compressor with the most running hours stops first.
Best fit - example
Here are at least two compressors are of different sizes. The capac-
ity distributor will cut in and cut-out the compressors to produce
the best possible capacity fit (the least possible capacity jump).
- There is operating time equalizing between the compressors 1
and 2 (same size in example).
- There is operating time equalizing between the compressors 3
and 4 (same size in example).
Compressor application 2 – 1 x single step
The controller is able to control a combination of one capacity
controlled and multiple single step compressors. The advantage
of this combination is that the unloader valves will be used to fill
in capacity gaps and thereby achieve many capacity steps via few
compressors.
Preconditions for using this compressor application are:
• All compressors are the same size
• The capacity-regulated compressor can have up to three unload
valves.
• The main step and the unload valves can be different sizes, i.e.
50%, 25% and 25%.
This compressor combination can be handled in the following
coupling patterns:
• Cyclical
General regarding Handling:
Cutin
The capacity-regulated compressors with unloader valves start
before one-step compressors. The capacity controlled compres-
sor will always be fully loaded before cutting-in of subsequent
one-step compressors.
Cutout
The capacity regulated compressor will always be the last to
stop. The capacity controlled compressor will always be fully
loaded before cut-in of subsequent one-step compressors.
Unloader valves
At cyclical operation unloader valves are used to close capacity
holes from the subsequent one-step compressors.
Anti-cycle timer restrictions
In case a capacity controlled compressor is prevented in start-
ing due to anti-cycle timer restrictions, then the start of any
subsequent one-step compressors is not allowed. The capacity
controlled compressor is started when the timer restriction has
expired.
Cyclical operation - example
The one-step compressors will be cut in and cut-out in accordance
with The First-In-First-Out (FIFO) principle in order to equalise
operating hours between the compressors.
- The capacity controlled compressor is the first to start and the
last to stop.
- Unloader valves are used to close capacity holes
- There is operating time equalizing between the compressors 2
and 3 (same size in example).
Appendix A – Compressor combinations and coupling patterns