Innovative technologies for safe handling of electrical power to achieve high availability

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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


  • Insulation monitoring device for mobile generators
  • Protective separation with insulation monitoring and disconnection
  • According to IEC 60364-5-55 and IEC 61557-8
  • Two separately configurable response values
  • Multi-functional LC display

The ISOMETER® of the IR423 series is designed to monitor the insulation resistance RF of an unearthed AC system of 0…300 V to earth that is supplied by a mobile generator accor­ding to IEC 60364-5-551 / DIN VDE 0100-551 (VDE 0100-551). The IR423 is suitable for AC sys­tems with operating frequencies ≥ 30 Hz as well as for AC systems with directly connected DC circuits. The maximum permissible system leakage capacitance Cemax is 5 F.


  • Insulation monitoring for mobile generators AC 0…300 V
  • Protection by electrical separation with insulation monitoring and disconnection
  • Version “W” for protection against high mechanical stress
  • Two separately adjustable response values
  • Connection monitoring system/earth
  • Power On LED, alarm LEDs: Alarm 1, Alarm 2
  • Internal/external test/reset button
  • Two separate alarm relays (one changeover contact each)
  • N/O or N/C operation, selectable
  • Fault memory behaviour, selectable
  • Self monitoring with automatic alarm
  • Multi-functional LC display
  • Adjustable response delay
  • Two-module enclosure (36 mm)
  • Push-wire terminal (two terminals per connection)


  • IEC 60364-7-717, DIN VDE 0100-717 (2005) Electrical installations in mobile or transportable units
  • DIN VDE 0100-551 (VDE 0100-551), IEC 60364-5-551 Low-voltage generating sets (mobile generators)
  • GW 308 “Mobile Stromerzeuger für Rohrleitungsbaustellen 8/00” (Mobile auxiliary power generators on pipeline site”) (DVGW)
  • BGI 867 (German Berufsgenossenschaft Information) Auswahl und Betrieb von Ersatzstromerzeugern auf Bau- und Montagestellen (Selecting and operating standby generators on construction and installation sites)

Downloads for ISOMETER® IR423

CE Declarations of conformity IR42x 94.2 KB 12.08.2022 06:17:24
Manuals IR423 1.1 MB DE13.05.2019 10:31:41D00038
Manuals IR423 1.1 MB EN13.05.2019 10:31:41D00038
Manuals IR423 1.1 MB ES13.05.2019 10:31:54D00038
Datasheets IR423 365.3 KB DE13.05.2019 10:31:34D00038
Datasheets IR423 319.2 KB EN13.05.2019 10:31:35D00038
Datasheets IR423 312.2 KB ES13.05.2019 10:31:37D00038
Datasheets IR423 538.6 KB ZH13.05.2019 10:31:33D00038
Application brochures Elektrische veiligheid bij aggregaten en omvormers conform de NEN1010 3.6 MB NL13.05.2019 10:31:28
Application brochures Elektrische veiligheid bij voertuigen conform NEN1010 287.9 KB NL13.05.2019 10:31:28
Technical information Geänderte Relaisvarianten von vergoldeten Kontakten auf versilberte Kontakte 166.3 KB DE27.06.2022 09:03:08
Technical information Changed variants of relays from goldplated to silver-plated contacts 166.3 KB EN27.06.2022 09:03:08

Optional accessories for ISOMETER® IR423

TypeArt. No.
Mounting clip for screw mounting (one piece per device)B98060008

ISOMETER® IR423 Variants

TypeNominal system voltage* UnSupply voltage* USArt. No.**
IR423D4-1AC 0…300 V, 30…460 HzAC 16…72 V, 30…460 Hz / DC 9,6…94 VB71016304
IR423D4-2AC 0…300 V, 30…460 HzAC/DC 70…300 V, 30…460 HzB71016305
IR423-D4W-1AC 0…300 V, 30…460 HzDC 9,6…94 V / AC 16…72 V, 30…460 HzB71016304W
IR423-D4W-2AC 0…300 V, 30…460 HzAC/DC 70…300 V, 30…460 HzB71016305W

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