Accessories
4.8 Residual current devices
3VA molded case circuit breakers with IEC certificate
468
Manual, 03/2019, A5E03603177010-03
Use of the residual current device as a pure display unit
The RCD820 residual current device can also operate as a pure display unit without a
tripping function, i.e. it detects and signals residual currents, but does not trip the molded
case circuit breaker or interrupt the circuit.
If the RCD820 device is to operate as a pure display unit, the connecting cable between the
residual current device and the ETU of the molded case circuit breaker can be omitted. With
the exception of its communications interface functionality, the residual current device can
perform all its normal functions (e.g. status signaling via LEDs or alarm switches) in "display
mode". Since there is no connection between the RCD and the ETU, the LED "ACT" flashes
continuously and the LED "COM" is not illuminated even if a 5-series or 8-series ETU is
installed.
Communications interface
The RCD-ETU connecting cable not only carries the trip command, but also acts as the
communications interface between the residual current device and the 3VA communication
system.
Precondition for interface functionality:
●
The 3VA2 molded case circuit breaker is equipped with a communication-capable,
electronic trip unit (ETU 5-series or 8-series).
●
The molded case circuit breaker is linked to the communication system via a COM060
communication module.
If the residual current device is linked to the communication system, the link can be used not
only to interrogate the device for important status, diagnostic, maintenance and identification
data, but also to transmit commands.
The residual current device is normally supplied with power by the main current paths. When
the molded case circuit breaker is switched off, the power supply will be interrupted if the
feed is at the top. In order to maintain the link to the communication system when the power
supply from the main current paths is disconnected, the residual current device is supplied
with the necessary power by the COM060 communication module.
