KGL Operating Manual – VS 3010 BS
2018-07-02
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31 178
4.4.4 Capacity-controlled compressors
The pack controller can be used to regulate capacity-controlled compressors with up to 3 capacity stages
(base load plus 2 capacity stages (bypass valves)). The number of capacity stages can be configured
separately for Z1 and Z2 compressors. Capacity-controlled compressors do not have any influence on the
pack controller’s control algorithm, only the control sequence changes.
The base load of an available compressor is loaded first for the control of the compressors. Then the capacity
stages of the compressor are loaded for the refrigeration requirement before the base load of any other
compressor can be loaded. The shifting down of capacity stages is performed in reverse order.
The number of the controlled capacity stages of a compressor is taken into account for the base load rotation.
The base load stage of a compressor can be switched using the integrated manual control switches. If the
base load stage has been switched off, the associated capacity stages are also switched off by the controller.
If both single-stage compressors as well as capacity-controlled compressors are configured in the Z1/Z2
circuit, the capacity-controlled compressors are loaded first. This proceeds in the order described above (first
the base load stage, followed by the associated capacity stages). When all the capacity-controlled
compressors of the Z1/Z2 circuit are running at 100%, and additional refrigeration is required, the single-stage
compressors are loaded. In order to obtain a finer gradation, when a single-stage compressor is loaded, the
capacity stages of a capacity-controlled compressor are unloaded so that only its base load is still operating. If
additional refrigeration is required, these capacity stages are loaded again.
In an example (Z1circuit) for the loading and unloading of compressors, the system configuration is as follows:
Number of compressors Z1: 2
Number of capacity stages per capacity-controlled compressor Z1: 3
Number of capacity-controlled compressors Z1: 1
Loading of compressors
The loading of compressors is illustrated using the example in the following table:
Base module
Relay no.
S1
terminals 13/14
S2
terminals 23/24
S3
terminals 33/34
S4
terminals 43/44
Meaning
Base load stage 1
Capacity stage 2
Capacity stage 3
Base load stage 4
1
X
2
X
X
3
X
X
X
4
X
X
5
X
X
X
6
X
X
X
X
When unloading, the capacity stages of a capacity-controlled compressor are switched off first. This is followed
by the loading of a single-stage compressor. The capacity stages of the capacity-controlled compressor are
loaded again at the same time.
Shifting down of compressors
The shifting down of compressors is illustrated using the example in the following table:
Base module
Relay no.
S1
terminals 13/14
S2
terminals 23/24
S3
terminals 33/34
S4
terminals 43/44