4 MRCDB300-series_D00343_05_Q_XXEN/01.2022
MRCDB300 series
Connection - N/C principle with contact feedback
Refer to the manual for further connection options.
Commissioning - Modbus RTU
Address setting
i
Every MRCDB3… has a factory-set Modbus address. The address is 1XX, where XX = the last
two digits of the serial number. Example: Serial number = 123456
78
-> Modbus address = 178
The preset address can be changed via a COMTRAXX gateway, via Modbus or directly on the de-
vice.
The address can be changed on the device before installation and offset calibration. The electron-
ic module must not be connected to the measuring current transformer during address setting.
Each address in the bus system may only be assigned once.
i
The use of a type 2 surge protection de-
vice (SPD) is mandatory due to possible
impulse voltages and in order to comply
with normative requirements.
The surge protection device must be con-
nected upstream of the power supply
unit on the supply side.
Features of the surge protection device:
– Nominal discharge current In (8/20 μs): 20 kA
– Response time: 25 ns
– Two-stage: 1 va 1 spark gab
– Alternatively, the power supply unit must be
connected to a CAT II supply without a surge
protection device.
U<
F 6 A
L1
L2
L3
N
DC 24 V
AC
DC
21
GND
T/R
GND
24 V
22 24
21
22 24
11
12 14
3
MRCDB30...-CTBC...
DG
D1
i
Within an interconnection of devices via
the RS-485 interface, the first and the
last device must each be provided with a
terminating resistor.
This device-internal resistor can be con-
nected by means of a wire jumper or a
DIP switch.
X1 X2
120 Ω
120 Ω
DIP switch
COM465IP
last device
MRCDB30...
first device
Wire jumper
