Insulation monitoring device
for mobile generators
The IR423 A-ISOMETER® monitors 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). 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 μF.
• Electrical installations in mobile or transportable units IEC 60364-7-717: 2001; (Require-
ments for special installations and locations – Mobile or transportable units) DIN VDE
• Insulation monitoring for mobile gene-
rators AC 0…300 V
• Option “W”: For high mechanical stress
when using the protective measure “Pro-
tective separation with insulation moni-
toring and disconnection”
• Two separately adjustable response values
• Connection monitoring system / earth
• Power On LED, LED Alarm 1, LED Alarm 2
• Internal and external test / reset button
• Two separate alarm relays (one change-
over contact each)
• N / O or N / C operation
• Fault memory, selectable
• Self monitoring with automatic alarm
• Multi-functional LC display
• Adjustable response delay
• Two-module enclosure (36 mm)
The currently measured insulation resistance is indicated on the LC display. In this way any
changes, for example when circuits are connected to the system, can be recognized easily.
When the insulation resistance falls below the set response values, the response delay “ton”
starts running. Once the response delay “ton” has expired, the “K1 / K2” alarm relays switch
and the alarm LEDs “AL1 / AL2” light up. Two separately adjustable response values / alarm
relays allow a distinction to be made between “prewarning” and “alarm”. If the insulation resis-
tance exceeds the release value (response value plus hysteresis), the alarm relays return to
their initial position. If the fault memory is enabled, the alarm relays remain in the alarm state
until the reset button is pressed or until the supply voltage is switched off. The device func-
tion can be tested using the test button. The parameterization of the device can be carried
out via the LC display and the function keys integrated in the front plate.
The connections to the system (L1 / L2) and to earth (E / KE) are either automatically checked
every 24 h, or by pressing the test button or when supply voltage is applied. In case of inter-
ruption of a connecting lead, the alarm relays K1 / K2 switch, the LEDs ON // AL1 // AL2 flash
and the following message appears on the display:
„E.02“ indicating a fault in the connecting leads to the system,
„E.01“ indicating a fault in the connecting leads to PE.
After eliminating the fault, the alarm relays return to their initial position either automati-
cally or by pressing the reset button.
The IR423 A-ISOMETER® uses the measuring principle “superimposed square-wave pulses”.
The IR423 type range complies with the standards: DIN EN 61557-8 (VDE 0413-8): 1998-05,
EN 61557-8: 1997-03, IEC 61557-8: 1997-02, ASTM F 1669M-96: 2002, DIN VDE 0100-551: 1997,
IEC 60364-5-551: 1994, IEC 60364-7-717: 2001, DIN VDE 0100-717: 2005.
2 DB101013en / 09.2006