90
Capacity
controller RS8HF102 © Danfoss 2017-07
AK-PC 772A
Variable integration time
There are two parameters, so Tn can be made variable. This allows
control to be more rapid, the further pressure deviates from the
reference.
The A+ setting will lower Tn when the pressure is above the refe-
rence, and the A- setting will lower Tn when the pressure is below
the reference.
Tn has been set to 120 s in the graph below, and falls to 60 s if the
pressure is above the reference and to 40 s if the pressure is below
the reference.
Above the reference: Set Tn divided by the A+ value.
Below the reference: Set Tn divided by the A- value.
The controller calculates the curve, such that regulation is smooth.
Regulation parameters
To make it easier to start up the system, we have grouped regula-
tion parameters into sets of commonly used values, called "Easy-
settings". Use these to choose between sets of settings appropri-
ate for a system which responds slowly or quickly. The factory
setting is 5.
If you need to fine tune the control, select the "User defined" set-
ting. All parameters can then be freely adjusted.
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.
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.
Easy-
Settings
Regulation parameters
Kp
Tn
A+
A-
1 = Slowest
1.0
200
3.5
5.0
2
1.3
185
3.5
4.8
3 = Slower
1.7
170
3.5
4.7
4
2.1
155
3.5
4.6
5 = Default
2.8
140
3.5
4.4
6
3.6
125
3.5
4.2
7 = Faster
4.6
110
3.5
4.1
8
5.9
95
3.5
4.0
9
7.7
80
3.5
3.8
10= Fastest
9.9
65
3.5
3.5
User defined
1.0 - 10.0
10 - 900
1.0 - 10.0
1.0-10.0
