Bitzer CM-RC-01, Reference Manual

Page: 39 / 44

v. 3.0 Reference guide
Compressor Control Module CM-RC-01
3.0
39 / 44
11.
Trouble shooting

Check if there is power to the unit according to specification.
If the power is ok,

Turn off the power for 5 seconds and see if the relays are energized after power on and
applying the run signal again.

If not energized:
turn off all the power to avoid risk of injury!

Un-mount one of the cables to the PTC element in the motor

If the measured resistance is above 4.5 k
Ω ±20%, the temperature of the PTC-sensor is
above the threshold limit and the fault relay has been released to protect the motor or
installation.

If the measured resistance is more than 1 MΩ, there is a broken connection to the PTC-
sensor and the relays will not be engaged.

If the measured resistance is close to zero
Ω, there is a short circuit on the PTC-sensor
cables and there is no overheat protection!

If all three phases are within range and resistance is below 2.7 k
Ω ±20%, the compressor
module may be defect and needs replacement.

Application limits
Via the serial communication the actual zone where the warning or alarm is raised can be
read via the BEST Software.

Verify using BEST Software that CM-RC-01 is configured for the correct compressor and
application. Also that the correct compressor start type is configured: DOL, Part winding,
Star-delta.
11.1 Communications trouble shooting

Check the communication cables for correct wiring

Check if the communication address setting matches the selected.
Note: Address 0 is not allowed! Default address is 48.

Check if the communication speed matches the selected. Use the BEST Software to read
the settings.

Check if communication is active. There is one LED for communication activity, please see
next section.

Please observe that all registers in the parameters are index based, meaning they start
with no. 1 and not with zero.
Use BEST Software for viewing Modbus communication status.
Return codes from Modbus communication if a telegram is not accepted by the CM-RC-01.
Code Name Meaning
01 Illegal function The function code is not valid.
02 Illegal data address The specified register is not valid
03 Illegal data value The value is not allowed
04
Slave device failure Unrecoverable error in slave
Check warning, critical and fault messages via Modbus or BEST Software.