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Modular residual current device type B for additional protection (protection against indirect contact) in earthed systems (TN and TT systems)

The AC/DC sensitive MRCDB423 with the corresponding CTUB101-CTBC… measuring current transformers are used as additional protection (protection against indirect contact) in earthed systems (TN and TT systems) in which AC or DC fault currents may occur. Part of these systems are particularly loads containing six-pulse rectifiers or one-way rectifiers with smoothing, such as converters, battery chargers, construction site equipment with frequency-controlled drives.

Since the values are measured with measuring current transformers, the MRCDB423 is almost independent of the nominal voltage and the operating current of the monitored system.

The residual operating current IΔn2, the response delay ton2 as well as the currently measured residual current IΔ are shown on the standard display.

By using an MRCDB423 with a suitable current transformer and a switching element with isolating properties, the device combination fulfils the requirements of IEC 60947-2 Annex M for an MRCD protective device.

The application is specifically intended for protection goals such as protection of persons, fire protection and plant protection. The switching element must not exceed a switch-off time of 17 ms.


  • AC/DC sensitive MRCD type B in accordance with IEC 60947-2 Annex M
  • Use as modular residual current protective device for additional protection in earthed systems
  • Operating characteristic type B in accordance with IEC 60755
  • RMS value measurement of the residual current
  • Alarm and prewarning indication via LEDs
  • Alarm and prewarning output via relays (K1/K2)
  • Control of a switching element with isolating properties via relay K2
  • Measuring current transformer connection monitoring
  • Fault memory


  • Additional protection (protection against indirect contact) in earthed systems (TN and TT systems)

Downloads for LINETRAXX® MRCDB423

CE Declarations of Conformity MRCDB4xx 86.3 KB 2022/08/12 06:17:2512.08.2022 06:17:25
Datasheets MRCDB423 678.1 KB EN2021/08/02 12:00:1702.08.2021 12:00:17D00396
Manuals MRCDB423 2.5 MB EN2021/07/13 13:10:4313.07.2021 13:10:43D00396
Flyers Modular Residual Current Device (MRCD) 96.3 KB EN2021/05/18 07:41:3318.05.2021 07:41:33
Technical Information Changed variants of relays from goldplated to silver-plated contacts 166.3 KB EN2022/06/27 09:03:0827.06.2022 09:03:08

Optional Accessories for LINETRAXX® MRCDB423

External measuring current transformers

TypeCT diameterShieldArt. No.
CTUB101-CTBC20ø 20B78120010
CTUB101-CTBC20Pø 20B78120020
CTUB101-CTBC35ø 35B78120012
CTUB101-CTBC35Pø 35B78120022
CTUB101-CTBC60ø 60B78120014
CTUB101-CTBC60Pø 60B78120024
CTUB101-CTBC120ø 120B78120016
CTUB101-CTBC120Pø 120B78120026
CTUB101-CTBC210ø 210B78120018
CTUB101-CTBC210Pø 210B78120028

Connection cable measuring current transformer – MRCDB423

TypeLength/mArt. No.


TypeArt. No.
Mounting clip for XM420 enclosureB98060008


TypeResponse range IΔnRated frequencySupply voltage US*Art. No.
MRCDB423-D-130 mA…3 A0…2000 HzDC 9,6…94 V / AC 42…460 Hz, 16…72 VB94043055
MRCDB423-D-230 mA…3 A0…2000 HzDC 70…300 V / AC 42…460 Hz, 70…300 VB94043056

* Absolute values of the voltage range