Capacity Distribution Methods - Danfoss AK-PC 781A User Manual

Capacity distribution methods

The capacity distributor can work based on 2 distribution
principles.
Coupling pattern – Cyclical operation:
This principle is used if all compressors are of the same type and
size.
The compressor cuts-in and cuts-out in accordance with the "First
In First Out" principle (FIFO) to equalise operating hours between
the compressors.
Speed-regulated compressors will always be cut in first, and the
variable capacity is used to fill capacity gaps between the subse-
quent steps.
Timer restrictions and safety cut outs
If a compressor is prevented from starting because it is "hanging"
on the restart timer or is safety cut out, this step is replaced by
another compressor.
Operating time equalisation
The operating hour equalizing is carried out between compressors
of the same type with the same total capacity.
-At the different startups the compressor with the lowest number
of operating hours will be started first.
- At the different stops the compressor with the highest number of
operating hours will be stopped first.
- For compressors with several steps, the operating time equalizing
is carried out between the compressors' main steps.
- The left column shows the operating hours, according to which
the controller equalises.
- The middle column shows (as a percentage) to what extent
the individual compressor has been activated within the last
24 hours.
- The right column shows the compressor's current operating time.
The value should be reset when the compressor is replaced.
96 Capacity controller RS8HE202 © Danfoss 2017-07
Coupling pattern – Best fit operation
This principle is used if the compressors are of different sizes.
The capacity distributor will cut-in or cut-out the compressor
capacity in order to ensure the least possible capacity jump.
Speed-regulated compressors will always be cut in first, and the
variable capacity will be used to fill capacity gaps between the
subsequent steps.
Timer restrictions and safety cut outs
If a compressor is prevented from starting because it is "hanging"
on the restart timer or is safety-cut out, this step is replaced by
another compressor or another combination.
AK-PC 781A