CT-600-2 43
Regulation / Select Operation Mode
The ACP can operate in different modes. The ACP LINK will distribute
the requested capacity over the available compressors in all modes,
except for “remote ind.” and “service”, where the capacity of each
compressor is handled separately. The distribution of the capacity
over the compressors is done in a way to assure a certain
compromise between energy efficiency and control accuracy. See
also item no. 3.5 in section 12.4 about capacity distribution between
compressors. Take in mind that the first compressor to start will
require that the requested capacity is 1/3 above the minimum nominal
capacity of the ACP. The minimum capacity to start is displayed on
the CTRL screen [7]. The last compressor will only stop when the requested capacity is below 1/3 of the
minimum capacity of the ACP
Definition of minimum nominal capacities and minimum capacity to start
The minimum nominal capacity levels of the compressors and the unit are used to decide whether to start or
stop the operation of the unit or the single compressor in the operating modes manual, auto, remote and
remote individual.
Minimum nominal compressor capacity for a slide valve regulated compressor is defined as the minimum slide
valve position.
Minimum nominal compressor capacity for a speed regulated compressor is defined as the ratio between the
minimum and the maximum speed..
The minimum capacity of the unit is equal to the sum of the minimum capacity for each compressor, which in
case of variable speed operation is corrected with the ratio between the maximum frequency and the line
frequency.
The minimum capacity to start (operation modes manual, auto and remote) is exactly 4/3 times the minimum
nominal capacity of the unit. The minimum capacity to start is higher than the minimum nominal capacity in
order to assure that the ACP LINK can regulate the capacity (up/down), once started. It also assures that a
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