AK-PC
572
User
Guide RS8KH202 © Danfoss 2019-03
3
Suction Group
Compressor types
The following types of compressors can be used for regulation:
• Single-step compressors (one can be speed-regulated)
• Bitzer CRII compressor with two unloaders (4-cylinders). MT only.
Capacity regulation
The cut-in capacity is controlled by signals from the connected
pressure transmitter and the actual reference.
In the absence of any reference there is a neutral zone of up to 5 K.
– When the pressure is higher than the “ref a half neutral
zone”, cut-in of the next compressor (arrow up) is permitted.
– When the pressure is lower than the “reference - a half neutral
zone”, cut-out of a compressor (arrow down) is permitted.
– When the pressure is within the neutral zone, the process
will continue with the currently activated compressors.
This is always controlled using the "Best fit" connection pattern.
The reference
The controller will be set based on a fixed reference point.
Based on the configured reference, the controller will permit an
offset of up to +/- 8K depending on the other control parameters.
For example
- Night-time increase. Fixed 5 K (on the MT circuit only)
- Po optimisation (on the MT circuit only)
Load shedding
The function is activated from the system unit.
When the load shedding function is activated, the maximum
permissible compressor capacity will be limited to 50% of
maximum on both MT- and LT circuits.
In this way, the total electrical load in the store is limited.
Control parameters
To make it easier to start up the system, we have grouped the con-
trol parameters into a number of experience-based values. These
values have been combined in a setting called "Easy-settings".
Here you can choose between a set of control settings applicable
to a slow to rapidly reacting system.
The factory setting is medium.
Oil management
If the DO6 output is in use by a CRII, oil management cannot take
place. If the output is available, the controller can pulse oil into the
MT circuit. The time between the pulses can be configured using a
timer function or using a signal from a level switch.
8 K
8 K
Po ref.
