BenderIREH470Y2-6ISOMETER Insulation Monitoring Device for Unearthed IT Systems, 0-793 V AC, 230 V AC Supply, DIN Rail

Product Description

What this part is

A Bender ISOMETER IREH470Y2-6 insulation monitoring device, Bender article number B91078001. It continuously measures the insulation resistance between an unearthed (IT) power system and protective earth, and raises an alarm when that resistance falls below a set response value. It is a DIN-rail mounted device for AC IT systems.

What these specs mean in practice

An IT system has no deliberate connection between the live conductors and earth, so a single earth fault does not trip the supply and the load keeps running. That resilience is the reason IT systems are used on ships, in mines, in operating theatres and on continuous process plant. The trade-off is that the first fault is invisible: nothing trips, and a second fault on another phase becomes a short circuit. An insulation monitoring device is what makes the first fault visible, which is why IT distribution is required to carry one.

The device superimposes a small measuring signal onto the system and evaluates the returning current, so it monitors continuously while the system is live and loaded. Two independently adjustable response values allow a prewarning threshold and a main alarm threshold to be set separately, so degrading insulation is reported before it reaches the alarm level.

Published specifications

Function: insulation monitoring device (ISOMETER) for unearthed IT systems
Monitored system voltage: AC 0–793 V
System frequency range: 50–400 Hz
Supply voltage: AC 230 V, 50/60 Hz
Power consumption: 3.0 VA
Response values: two, independently adjustable
Alarm output contact rating: 250 V, 5 A
Mounting: DIN rail
Manufacturer article number: B91078001

Quantity and configuration

Sold as 1 Pc — one insulation monitoring device. The unit is supplied without a coupling device and without external current transformers.

Installation and setup notes

The device connects between the monitored IT system conductors and the protective earth conductor, with its own 230 V AC supply brought in separately from the monitored system so that monitoring continues when the system is de-energised. Response values are set on the device. For system voltages above the monitored range, Bender supplies separate coupling devices; those are ordered separately.

Interchange guidance

Within Bender’s ISOMETER range the IR470 family covers the same class of AC IT system duty, and the IR470LY2 variants share the unearthed-AC-system application. Response value ranges, supply voltage and enclosure differ between variants, so those are related devices, not substitutes. An exact match carries the IREH470Y2-6 designation or Bender article number B91078001.