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  • Electrical safety for unearthed power supplies (IT systems)
  • Insulation monitoring equipment, insulation fault location systems
  • Power supplies for medical applications
  • Measuring and monitoring relays
  • Electrical safety for earthed power supplies (TN systems)
  • Using renewable energies efficiently: wind power, photovoltaics
  • Test systems for electrical equipment and medical technology


The AC and pulsed DC sensitive residual current monitor RCM420-D (Type A) from Bender is designed for fault and residual current monitoring in earthed power supply systems (TN and TT systems) where an alarm is to be activated in the event of a fault, but disconnection must be prevented. In addition, the device can be used to monitor single conductors, such as PE conductors, N-PE connections and PE-PAS connections.

The prewarning stage (50…100 % of the set response value IΔn2) allow to distinguish between prewarning and alarm. Since the values are measured with measuring current transformers, the device is nearly independent of the load current and the nominal voltage of the system.


  • AC and pulsed DC sensitive residual current monitor Type A according to IEC 62020
  • r.m.s. value measurement (AC)
  • Two separately adjustable response values
  • Frequency range 42…2000 Hz
  • Start-up delay, response delay and delay on release
  • Restart function
  • Digital measured value display via LC display
  • Measured value memory for operating value
  • CT connection monitoring
  • LEDs: Power On, Alarm 1, Alarm 2
  • Internal/external test/reset button
  • Two separate alarm relays (one changeover contact each)
  • N/O or N/C operation and fault memory behaviour selectable
  • Password protection for device setting
  • Device self monitoring
  • Sealable transparent cover
  • Two-module enclosure (36 mm)
  • RoHS compliant
  • Push-wire terminal (two terminals per connection)


  • Residual current monitoring in earthed two, three or four conductor systems
  • Current monitoring of single conductors de-energised under normal conditions
  • Socket-outlet circuits for devices which are operated unattended for a long time and which may not fail
  • Alarm systems, safety devices
  • Air conditioning systems, EDP systems
  • Cooling equipment with valuable frozen goods
  • Canteen kitchens
  • Monitoring of earthed power supplies for stray currents
  • Impact on N conductors
  • Trace heating systems

Downloads for LINETRAXX® RCM420

CE Declarations of conformity RCM42x 89.4 KB 12.08.2022 06:17:25
Manuals RCM420 736.1 KB ES13.05.2019 10:31:54D00057
Manuals RCM420 747.0 KB FR13.05.2019 10:31:55D00057
Datasheets RCM420 497.1 KB ZH13.05.2019 10:31:33D00057
Manuals RCM420 1.7 MB DE18.03.2021 13:26:37D00057
Manuals RCM420 1.7 MB EN18.03.2021 13:27:05D00057
Datasheets RCM420 317.5 KB DE10.01.2020 10:34:44D00057
Datasheets RCM420 285.2 KB EN10.01.2020 10:35:02D00057
Datasheets RCM420 318.2 KB ES10.01.2020 10:35:15D00057
Quickstarts RCM420 1.0 MB DE26.03.2021 07:29:15D00057
Quickstarts RCM420 1.0 MB EN26.03.2021 07:29:15D00057
Datasheets XM420-Schnittstellenoptionen 264.1 KB DE13.05.2019 10:31:35
Datasheets XM420 interface options 223.5 KB EN13.05.2019 10:31:36D00051
Technical information Changed variants of relays from goldplated to silver-plated contacts 166.3 KB EN27.06.2022 09:03:08
Technical information Geänderte Relaisvarianten von vergoldeten Kontakten auf versilberte Kontakte 166.3 KB DE27.06.2022 09:03:08

Optional accessories for LINETRAXX® RCM420

External measuring current transformers

TypeInside diameter (mm)Art. No.
CTAC20ø 20B98110005
CTAC35ø 35B98110007
CTAC60ø 60B98110017
CTAC120ø 120B98110019
CTAC210ø 210B98110020
WR70x17570 x 175B98080609
WR115x305115 x 305B98080610
WS20x3020 x 30B98080601
WS50x8050 x 80B98080603
WS80x12080 x 120B98080606


TypeArt. No.
Mounting clip for enclosure XM420 (1 piece per device)B98060008

LINETRAXX® RCM420 Variants

TypeResponse range IΔnFrequency rangeSupply voltage US*Art. No.
RCM420-D-110 mA…10 A42…2000 HzDC 9,6…94 V /
AC 16…72 V, 42…460 Hz
RCM420-D-210 mA…10 A42…2000 HzDC 70…300 V /
AC 70…300 V, 42…460 Hz

* Absolute values
**(B7… = push-wire terminal / B9… = screw-type terminal)