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  • Insulation monitoring device for de-energised loads
  • Application in TN, TT or IT systems
  • According to IEC 61557-8
  • Two separately configurable response values
  • Multi-functional LC display

The offline monitor of the IR420-D6 series is designed to monitor the insulation resistance of loads in the de-energized state. These loads, usually temporarily operated or de-energized most of the time, e.g. fire extinguisher pumps, slide valve drives etc are supplied from TN, TT or IT systems. During the shut-down periods, hohwever, humidity or other effects may cause insulation faults in the wiring or the loads which may go undetected. Switching the device on may then lead to the tripping of the protective device or may even result in motor fires and the device cannot be operated. In combination with a coupling device, the Iso­meters can also be used for higher voltages.


  • Insulation monitoring for de-energised TN, TT and unearthed systems AC, 3(N)AC and DC
  • Nominal voltage extendable via coupling device
  • Two separately adjustable response values 100 kΩ…10 MΩ
  • LEDs: Power On LED, LEDs Alarm 1, Alarm 2 for signalling insulation faults
  • Combined test/reset button
  • Two separate alarm relays with one changeover contact each
  • Fault memory behaviour, selectable
  • Push-wire terminal (two terminals per connection)


  • De-energized loads such as automatic fire extinguisher pumps, emergency drives, ship cranes, slide-valve drives in supply lines (gas, water, oil), motor-driven closing systems, diving pumps, drives for anchors, elevators, flue-gas valves and stand-by generators.

ISOMETER® IR420-D6 Variant(s)

TypeSupply voltage* USResponse value RanSystem leakage capacitance CeArt. No.**
IR420-D6-1DC 9,6…94 V /
AC 16…72 V, 42…460 Hz
100 kΩ…10 MΩ≤ 10 µFB71016415
IR420-D6-2DC 70…300 V /
AC 70…300 V, 42…460 Hz
100 kΩ…10 MΩ≤ 10 µFB71016407

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

Optional Accessories for ISOMETER® IR420-D6

TypeNominal system voltage* UnArt. No.
AGH520SAC 0…7200 V, 50…400 HzB913033
Mounting clip for screw mounting (1 piece per device) B98060008
Mounting frame XM420  B990994 

Downloads for ISOMETER® IR420-D6

CE Declarations of conformity IR42x 94.2 KB 2022/08/12 06:17:2412.08.2022 06:17:24
Manuals IR420-D6 1.3 MB DE2021/05/07 10:08:5007.05.2021 10:08:50D00117
Manuals IR420-D6 1.3 MB EN2021/05/07 10:08:5007.05.2021 10:08:50D00117
Manuals IR420-D6 491.4 KB ES2019/05/13 10:31:5413.05.2019 10:31:54D00117
Datasheets IR420-D6 447.7 KB DE2021/05/06 04:43:4506.05.2021 04:43:45D00117
Datasheets IR420-D6 407.9 KB EN2021/05/06 04:43:4906.05.2021 04:43:49D00117
Datasheets IR420-D6 447.2 KB ES2021/05/06 04:43:5406.05.2021 04:43:54D00117
Datasheets IR420-D6 490.1 KB ZH2019/05/13 10:31:3313.05.2019 10:31:33D00117
Datasheets XM420-Schnittstellenoptionen 264.1 KB DE2019/05/13 10:31:3513.05.2019 10:31:35
Datasheets XM420 interface options 223.5 KB EN2019/05/13 10:31:3613.05.2019 10:31:36D00051
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
Technical information Geänderte Relaisvarianten von vergoldeten Kontakten auf versilberte Kontakte 166.3 KB DE2022/06/27 09:03:0827.06.2022 09:03:08