Bitzer CM-RC-01, Reference Manual

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v. 3.0 Reference guide
Compressor Control Module CM-RC-01
3.0
17 / 44
5.
Control of the CM-RC-01
Control commands and setpoint can be given to the CM-RC-01 via different interfaces
Digital inputs:
Start/stop
Analogue input: Setpoint
Serial control: Commands and setpoint
The commands from the different interfaces are merged and the resulting “Control Word” can be
read via the serial Interface.
The capacity is limited between 10 % and 100 % even if the sum of the setpoints may be below
100 % or above 100 %.
The serial protocol is Modbus (RTU). Modbus can be connected for example for monitoring only
but still using the digital and analogue inputs for control of the CM-RC-01. Most common is to
monitor and control the CM-RC-01 via the Modbus interface.
The serial control is inactive by default. Please see section 5.2 Enable serial control.
5.1 Commands and setpoint
The basic operation of the CM-RC-01 is controlled by

Commands: Start and stop

Setpoint
– analogue or serial control

Setting of serial control parameters
o
"Serial Control Source"; default is none: 0
– 10V input
See parameter in section 10.3.7 Configuration
– application
o
Setting of the refrigerant (if not done via the BEST Software)
Commands and setpoint can be given via the digital and analogue inputs or by combining the
digital and analogue inputs with values from the serial interface. See later in this section.
5.1.1 Command Start
The Start command becomes active when a start signal is given via digital input or serial control.
If the compressor is started too many times per hour, the CM-RC-01 will give a waning but the
compressor will be allowed to start
The speed of the motor will normally match the setpoint. Details are described below.
When the motor is running and the start condition is removed (Start is set to inactive), the
compressor is stopped.
5.1.2 Setpoint
– and speed changes
The setpoint is a value in the range -100 % to +100 %. There is no ramping of a capacity change
request. The setpoint from the analogue input and the serial control are added. E.g. the analogue
signal could be an offset and the serial control could be the fine tuning.
Analogue control: Apply a 0
– 10V speed signal (0 – 100%) to the CN13 Cap. Input.
Serial control: Set the capacity request in parameter Serial Setpoint (-100 %
– +100%)
Please see section 10.3.1 Control
– application for the parameter to use for the setpoint.